Geology of Devonian Shale Oil and Gas in Pleasants, by amw19049


									Geology of Devonian ShaIe Oil
and Gas in Pleasants, Wood, and
Ritchie Counties, West Virginia
J.K. Filer, Wesf Virginia Geological and Eco;omic Survey

                                                                                                      5PE i~33q
Sumtirary.Upper DevoniaII shale play of western West Virginia is an area of active development
       The                                                                                                  of unconventional oil and
 gas reserves. It is unconventional in that production is from tine-grained fractured reservoirs. Examimtion of recent d+g     resufts
 has led to a more detailed understanding of the structure and. stratigraphy of the area, which in mm can explain some of the                       . ,
 production trends observed. Areas of greater fracture density and therefore higher productivity are rdated to areas of shearing
 motion in the Burning Springs Otmst sheet. Open flows after stimulation in these wells can be ve~ Klgh, but first-year decline is
 rapid. It is’uncertain at this time how long a production life these wells will have.

The most active oif and gas play in West Virginia from 1981 to              street m~bers decreases significantly from west to esst (Fig. 1),
1984 was in the Devonian shales in six northwestern countie.s—              and the two units become significantly lighter in color. 7.8
Wood, Pleasants, Ritchie, Wirt, Calhoun, and Rome. The West                    The lighter-colored, generaly siltier, and less organic units are,
Virginia Geological and Economic Survey is monitoring and sum-              in descending order, an undivided section at the top of the Devcmi-
marizing this activity to gain a better understanding of the geolo-         an above the Huron, the Java formation, the Angola member of
gy. Pleasants, Wood, and Ritchie counties are discussed here.               the West Falls formation, the Cashaqua member of the Scmyesfor-
                                                                            mation, the West River member of the Genesee formation, and the
Stratigraphic Framework                                                     Mahantango formation (Fig. 1).
 Fig. 1 is a west-to-east (dip-oriented) stratigraphic cross section           All @ese units are Upper Devonian, except the Maharttango and
of the shale section in this ares (see Fig. 2 for location). The sec-       fvfarcdus formations, which comdtute the Middle Devonian Handl-
tion thickens from 2,100 ft [6A0 m] in western Wood County (A)              ton group. In general, all units thicken from west to east, except
to more than 4,CKM [1220 m] in eastern Ritchie County (A’). Until
                     ft                                                     the undivided upper section (Fig. 1).
recently, the sequence was stratigrapbicalJy undMded, seldom ds-              As Nea16 and Dowse7 pointed out, the section consists of repeat-
cussed, and generatly ignored by operamrs in this area despite sig-        ed cycles of gray shak?s underlain by dark organic shales. No de-
nificant gas pmd.ction     from  eq”ivdent rocks in southern West          fined dark shale unit separates the Java formation from the Angola
                                                                           shale in this area, but Dowse7 considered a thin, 2- to 10-ft [0.6-      .. .
Virginia and eastern Ke”mcky, including Big San@, CottageviOe,
and Midway-Extra fields.                                                   to 3.O-m] zone with a distinct lowdensity kick at the base of the
   Since 1970, several studies on the Devonian shale stratigraphy          Java formation (Tig. 3) to be an organic-rich zone correlative with
of western West Virginia 1-7have provided a format stratigrapbic           the Pipe Creek member of New York.
framework correlated to shale outcrop in Ohio and New York.                   As Fig. 1 shows, an unconformity separates the Middle and Up
                                                                           per DeVON~ k the w-.1.2.7 O&.p OIUO the UIICOIIfCItity           SUI-
Dowse7 in pzrti&dar studied the shale stratigraphy of nofiwestem
West Virginia, which is discussed here.                                    face mounts    for the disappearance of progressively younger Upper
   The section (Fig. 1) extends t+om the base of the Pocono group          Devonian units to the West, whiJe the same feature accounts for
to tie top of @e Onesquethaw group and is Middle to Me Devc-               the truncation of progressively older Middle Devonim sedimen~
nkm. The top of the Devmda.nis easily idendtied by the Berea&.             in the same dmtion. Thus, in western Wood County, the Casha-
stone or Sunbury shale at the base of the Pocono when they are             qua member rests dizectly on the Omndaga limestone (Gnesquethaw
present, but is dit%cult to separate. from silts and silty shales of the   group).
lower Pocotto where they are absent in much of Ritchie and parts              Iq esstem Ritciie County, a very thin (< 5 ft [< 1.5 m]), very
of Pleasants counties. The base of ~e shale section is easily identi-      low gamma ray peak is present above the gray Mahantsngo shale.
fied by the contrast with underlying cherts and cherty limestones          Dowse7 considered this to represent the feather edge of the Tully
of the Onesquerhaw.                                                        limestone and suggested a second unconfonni~ beneath it.
   The section is generally composed of interbedded ShzdeS,S@
shates, and sitt?.tcmes.The shales V.WY    from black, organic-rich,       Geophysical Log Characteristics
and pyrite-rich zones to lighter gray, much less organic, and fre-         Idend6caricm of contacts between these shale units is relatively easy
quently siltier beds. Organic content d-ses         from west to esst,     with a combination gamma ray and density log, with certain ex-
while silt content increases. The organic shafe zones are promi-           ceptions. Fig. 3 shows these contacts on a rypicaf log in western
nent on geophysical logs as zones of high gamma ray intensity,             Wood County (WcGd-769), and a second log from Tyler County
primarily because of uranium associated with the organics, and as          (TYIw-735). (See Fig. 2 for lcxxions.) These logs illusrmle changes
zones of low bulk density because of the organics’ lower specific          across the mea.
gravity. These organic-rich zones, identititd in Fig. 1, are the ba-          On the Wood-76910Z, the tou of the Devouian is easilv recoz-
sis for stratigraphic subdivisions.                                        rdzed beneath the radioa%ve .Sm&NYshale and a thin spike;f Be&
   The organjcafly richer zones are, in descending order, the        sandstone just below 1,800 ft [549 m]. The base of the undivided
er Huron member of Ohio shale, the Rhinestreet member of the               section is essily seen at 2,9dl ft [902 m]. The more radbmtive
West FaJls formation, rbe Mtidiesex member of the Sonyea for-              Huron stands out prominently on logs below this point ~d changes
~f.iOn, the Gene.seo member of the Genesee formation, and tic              from interbedded gray and black shales to more massive black shale
Marcellus fmtnw.ion. The organic content of the Huron and Rbirte-          near its base at 3,456 ft [1053 m].
                                                                             TIICbase of the Jam formation is readdy identified at the base
C.pydght   1987 Sc4ety   .1 Pelmlewn   Enginwm                             of the Pipe Creek marker,7 prominent on the density log at 3,590

SPE   Formation    E.dustion,     December 1987                                                                                             4i9
                                             Fig. 1—Stratigraphic section of Devonian shale.
                                                                                                                                                    ..,. .....

ft [1094 ~In interbeds of radioactive sbafe are present in the
          m].                                                            below the Berea where Lw!bare identifiable. A siltstone in the same
Java, but contrast with the overlying Huron section is apparent.         position can be traced across dl three counties and has been a sig-
The base of the Angota shate is placed at the top of the first higbfy    iificant exploration target inaltoftbem.        It is generafly referred
organic radioactive bed at3,7S0ft[1155 m]. The Rbinestreet shale         to as the “Gordon sand” by drillers and occurs near the base of
is composed of interhedded organic shales and gray sbale$ near tie       a sifty section at the top of the Devonian. This section is equivalent
top and becomes more massively organic-rich below 3,S22ft[1165           to the following diiJJers’ “sands”: Gantz, Fifty-Fcot, TbirIy-Foot,
ml. Tbe oldest unit remaining above the unconformity here is the         Gordon Stray, Gordon, Fourth, and Fifth. The secdon is relative-
Casbsqua shale, represented by massive gray shale between 3,947          ly fme-gra.bwl this far west, and only the zone in the position of
and3,976ft[1203       and 1212 m].                                       the Gordon continues into Wood County.
   Below the unconfonnhy is a radioactive low-density zone that             Jn general, the section in es?.tem Ritcbie and Pleasanti counties
extends down to the top of the Onon&ga limestone at 3,992 fi [1217       contains numerous sittstone lenses, and the shales are less organic
m]. ~is may represent tbe remaining MarceUus formation, but              and siltier. The top of the Huron is difficult to see on the Tyler-735
Dowse7 recognized asimilar zone above tbe Onondagaongeo-                 log but falls at a thin, somewhat radioactive kick at 3,509 fi [1070
physicaJ logs throughout the study area regardless of the supradja-      ml, about ft [46 m] above sweral tin siltstones and about 20il
cent unit. She felt it might represent Tioga metabentonite or an         II [61 m] below another siltier mne. The up~er Siks w be cor-
organic-rich zone developed on the Onondaga during the erosional         related with the ddlers’ “Warren sand.”g,
event t@pmdncedt beunconformity. Akbougbgammarayand                         This far east, the Huron has lost most of its organic-rich charac-
density logs show a decrease in the organic content of the Huron         ter, and is composed primarily of gmy silty shale and siltstone, with
and Rbinem’eet shales across Wcwd County, the characteristics cited      scattered darker gray sbde interbeds. T’he silts occur throughout
should identify tbeseccmtacts counVwide.                                 in thin lenses and represent the distal tongues of the more promi-
   There are significant differences in the gamma ray density sig-       nent and well-known drioers’ “sands” to the east (upper Sp&ec&
natures of sbafes in the eastern pan of the study area. The Tyler-735    ley, lower Speecldey, Balttown, Bradford, Riley, and Benson).
welJlog(Tig. 3)istypicaf ofwellsintbis area. Altbough outside            Many silt lenses are seen on the Tyler-735 log, and the approxi-
of the study area (Fig. 2), this well is one of the few drilled to the   mate correlation of zones with dri!.fem’ sands is indicated in Fig.
Onesctuetbaw group this far east in the area, and it is a higbquality,                               a
                                                                         3. Fewer siltstone re present in western Ritcbie and Plessantx
representative-log:                                                      counties.
   In the Tyler-735 weU, the Sunbury iBerea is not obvious, a com-          Jn Wmd County, grayer shales in conma?.twith adjamnt organic
mon trait east of Wocd County. Thus, the top of the Devonian can         shales may ap         to represent sik.stone lenses, but the absence of
be approximated only by reference to overlying Greenbrier lime-          den.sity porosities greater than 2 to 3% in the Iow-gamnw.-fsy-
stone and upper Poccmo sands (“Big frjttn” of drillers), and to an       intensity zones indicates that they are not significantly cOarser-
underlying prominent siltstone. The siltstone is prssent in this well    gmined. Very few time siltstone beds exist in the Huron of western
at 2,678 ft [gl 6 m] and generally is present about 400 ft [122 m]       Wcud County.

420                                                                                                  SPE FormationEvaluation.December 1987
                                                                                  w.m~        WELL DISC”5SED         IN ~EX7 OP. lN
                      53! N%OL&’’%YY                                                          CROSS SECIION         A-A   [FIG. 11

                                  OF     PRODUCTION  FROM SILTS IN BASAL HURON,      +.,,5,              ,“,?+,..   SPRINGS   mJrlcLIFJE
                      ~?AVA       AND   ANGOLA, CIOT7E0 WHW2   OIL M PRODUCED
                                                                                                     N     FAULT, lEEIH   ON UP lHROWN     SIDE
                              MIXED PROOUCTION    FROM lHROUGHOUT   SHALE             h       %.,,          W,,,,     *Fmox\MbTE
                      ml      SEC11ON, DOTTED  WHERE  011 IS PRODUCED


                      Fia. 2—Productive areas. Devonian shale oil and gas i“ indicates tYrMlows shown in FkJ. 3).

   The base of the Huron can beidentitied fairly easily in most wells.      Ritcbie and Pleamnts counties, and identify the top of tie
fn the Tyler-735, the orgmtic tongue at the base (Fig. 1) has dk.ap         Rbines—t-5,206        ft [1587 m] in Tyler-735—where the contrast
peared, but the contact can be seen at a thin, somewhm radioactive          with the overlying Angola is not obvious.
kick m 4,6P0 ft [1430 m]. The thin silmmne just below the Huron                The massive, gray Cashaqua shale is easily idendfied L=E1OW 5,778
is seen on gantnm 12y curves only in a few scmtemd welh ,ilong              ft [1761 m] in Tyler-735. Below the base of the Cashzqua at 5,928
the extreme eastern edge of JZitchieand Pkasams counties, but the           ft [1807 m] is the dark shale. The top of the West River
Iowdensiw kick associated with it can be followed across the en-            member is at 5,963 ft f1817 ml and the black Geneseo is at 6,019
tire area..& the mne above becomes more organic, the combina-               ft [1835 m]. The Mid~esex, West River, and Geneseo onlap the
tion makes distinguishing the base of the Huron simple. This same           unconfomdty in central Wocd County, and east of there they can
low-denzitylintennedia~”gamrm-ray nwker is present ~Wcmd-769                be easily ideu~ed in all wells @led deep enough to reach them.
(Fig. 3) m 3,458 ft [1054 m], but this his thim~ and is difficult           They consistently show geophysical log charzctmistics similar to
m 2-ePEw3@   tithe   Overlying,organic zone at the base of tie Huron.       Tyler-735. (In some wells, the Geneseo is more radioactive.)
   Tbe lowdenslty Pip Creek marker is still obvious, marking the               A 3-ft [1-m] low gamma ray spike at 6,042 ft [1842 m] sep.mmes
base of the Java at 4,920 ft [1500 m]. To the south, in southeastern        the Geneses from the underlying Middle Devonian fvfarcdus shale.
Ritchie County, the low-density mne is lost between two sikstcme            lt IMY be a cakamons shale or shaly limestone eqnivzdent to the
tongues at the base of the Java mtd top of the Angola (see Fig. 1).         ‘fully limestone. fn some wells in Rimhie and Pkasards counties,
The best correlation for the base of the Java appears to be just be-        this may be underlain by about 10 ft [3 m] of gray shale, which
low the base of the upper tongue. These two sikmone tongues,                probably represents the Maimntango formation. Thc highly radi-
although not present in ~ler-735, thicken to more than 100 tl [30           oactive black Marcelbm formation is easily identified by its exm$me
m] m the wutheam, are composed of numerous individual lenses,               gamma ray sigrmm where present, but also it is absent in western
and are the most si~cant       coarser-grained interval in the Upper        Weed County, where it has been muncated by the overlying un-
Devonian section beIow the Gordon anywhere in the study area.               Conformiv.
They are also the deepest significant sihy?.one. Density log @msiv
in the sils”avemges about 6%, but reaches 10% in Odn zones. Tim
zones correlate with the drillers’ “Alexander” and have been a sig-         Development in the Devonian Shale
nificant exploration target in eastern Rimbie County.                       Thefirst ~orded production was obtained from the Upper Devo-
   l%e Mmstmet, although more tn’gankxich and radioactive h“                nizn 2bale3of 2Uthree mumiez around 40 yearz ago. Plea22nt3-124,
the Huron, has fewer dark ShaIe interbeds in Ritc@ieand Pleasants           ccmpl~     Oct. 18, 1939 @ig. 2), produced 1.5 BOPD [0.24 m3/d
counties Tyler-735 is ~picaf of the extreme east, with the lower            oil] from a zone at 2,930 ft [893 m] below the surface and just over
half niore radkmtive (lJig. 3). The five radioactive beds at the top        1,2w fl [366 m] below the Berea, according to the driJJer’s log.
of the Rhinestreet in Tyler-735 can generally be identified across          On the basis of geophysical logs of nearby wells, this production

SPE FormationEvaluation, December 1987                                                                                                            421

                                                                                                                                             - .....

                                                    Fig. 3—Type geophysical logs.

was protiably cpming from about 30 ft [9 m] above the top of the      there is a lag of several months between completion and fding of
Hurdit sI@e. Three other wells were completed nearby the foUow-       re@s, the actual toial is probably more than 1,3Cil.
ing Yeir. ‘ho were dw and abandoned, but tie tMrd, Pka.sams.170          When activity resumed in 1979, the focus was on the silty sec-
(about 2;OC0ft [610 m] southwest of the discovery welt), produced     tion at the top of the Upper Devonian, primarily the Gordon silt-
40 BOPD [6:3 m3 Id oil] from a ,28-ft [8.5-m] -thick zone about       stone. Gordon production (both 01 and gas) was discovered in
400 ft [122 m] above the Pleasants-124 pr~u~g          hO~On.         scattered areas in northern Wocd County and across Pleasams and
   In n@th-central Wood County in 1944, Wood-M4 found sever-          Ritchie counties (Tig. 2). More than 180 completion have been
d ga;-pfoducing zones at depths between 2,782 and 3,082 ft [848       repmted in this secdon since 1979, and they are about evenly divided
and 940 ml, About700 to 1,Wl ft [213 to 335 m] below the Berea.       among the three counties. The most active period for development
The prcduqioh was from tie lowest undivided Upper Devonian            in this mne was from late 1979 to early 1981. By the end of 1980,
seal+ aid mturd open flow was 2,409 Mcf/D [68x103 m3 /d]              operators were frequently attempting to find deeper shale produc-
gas. Attemp$ to.extend, this production were abandoned as dy.         tion in Pleasants and Ritie counties.
   Otdy icatired exploration ftdlowed until the mid-1960’s, when         Deeper shale weIls can be divided into two general groups. fn
Oie Pyketsbtig field was developed in Weed County. This field         eastern Ritchie County, about 120 wells have been completed,
produced gas and oil i@m the Berea and tlom an Upper Devonian         primatil~ f.; gas prcd.ction (mean open flow about 750 Mcf/D
silt.itone about 300 ft [91 m] below the Berea. This is the Gordon    [21 x 10 m Id] gas). Areas of development are outlined in F,g.
my, and it is ,tie only significant siltstone in the Upper Devonian   2. Prcducdon has been primarily from siltstone tongues in the basal
SectIon of Woti county.                                               Hurofi sbate, the Java formation, and the Angola member (Riley,
   AfIer we Parkersburg field, only intermittent activiv occurred     Benson, and Alexander of drillers). This area was most active in
until 1979. Between 1979 and the end of 1983, howevkr, 1,110          1981, but some wells are still being completed, especially in the
records of completions were reported between the Berea and the        northwestern comer of Ritchie County, despite the current slump
One@a&w of Plewms, Rhchie, and Wood counties. Because                 in gas markets.
422                                                                                              8PE FormationEvaluation, December 1987
                                           .-              —

                        .     ,1.X   B4WD 1P, &4AY HAVE 30ME           GAS    PROD                 +       S,NCUNAL       AXIS,   DASHED   WHERE   APPROXIMATE
                        .     >1000 MCFGPD        1?, MAY HAVE     SOME      OIL       PROD.                 UCIURE    CONTOUR, 8ASE HURON SHALE, C, I .30       FT.
                        .     >,00   BOPO W,      ,000   MC FGPD                                   J      YCEPT   20 O FT. ON BURNING SPRINGS ANTICLINE
                                                                                                          THRUSr       FAULT TEEIH   a   up THROWN      SIDE,
                    +          ANTkLINAL         AX!S, DA,”,.      WHERE     APPROXIMATE           \      ,A,HED        ~HE~E  .ppRoxlMArE

                                                            -.     .    ..         .           .                   .              . .

    West of this play, at least 800 wells have been completed for                                      about 2,500 to 2,PO0 ft [762 to 8~ m] below sea level, or about
  both oil and gas production in large areas of western Ritchie and                                    3,300 to 4,200 ft [1C06 to 1280 m] below the surface, depending
  central and western PIeasants counties.. fnterest in Ods,play has *                                  on elevation.
 great because of repoks of many high-volume oit wells (as great                                           It is unckar at this dme exactly why this part of the shale section
 as 2,CUI0  BOPD [31$ m3/d oil]). Reported oil and gas flows have                                       has prcduced the most oil. A complex combination of factors, in-
 varied greatly, even in adjacent wells.                                                                cluding geochemimy, litboio~, fnwttue intmsity, and fmcture per-
    me variation in reported flows is partly a function of inconsis-                                    meabiiirj, am probably responsible. One unique feature of this pat
 tent testing techniques and repotiug among operatorq but mostly                                        of the section in western Ritchie County and west and central
 a result cifvariatioq~ in the *gree of fracturing in the shale section                                 Pleasam County is the de-             of interbedding of Mbologies–
 encountered by indwidual we~. Also important is success in ar-                                         siftstones interb=eddedwith shales of varied organic cmntent. Gam-
 tificially fractt@ng the rock surrounding the wellbore to connect                                      ma ray logs indicate that the overlying section is composed of
 the well with mhmd fracture systems. Ex@nmmaJ techniques (in-                                          monotonous gay silty shale for several hundred feet, wbiIe the un-
 cluding N2 and C02 as fracturing fluids) have been used, but a                                         derlying section consists of interbedded gray and darker shales, with
 discussion of these is beyond the scope of this paper.                                                 few silt.st0ne3.The siltsmnes are slightly more porous than the as-
    p@”cdmt has bee” foun~ throughout the stratigrapbic section                                         sociated shale, but they still lack the pmeability necessary to serve
 discuswd h$re, although relatively fewer wells have tested beneath                                     as productive reservoirs.
 the Rbinestreet. Completion te+iques often male it impossible                                             It is possible that the combination of mechanically smnewhat het-
 to determine exactly where production in a well is coming from.                                       erogenmm interbeds resulted in tie development of a more prcduc-
 More than 2,fW3 ft [610 m] of section maybe perforated and frac-                                      five fracture system. Sharp contacts between siltstones of probably
 tured in two or MOWs~ges, and often perforation de@s within                                           mrbiditic origin and shales may ah allow ti’acmring along twd-
 stages are not reported                                                                               ding surfaces to occur. This relatiomhip of the lithology to the
    fn generat, however, gas has been produced throughout&e sec-                                       pmducdvity of the section is speculative.
 tion where fracNres are found, and oil production has also been                                          The post-19g0 drilling bcom in the deeper-sJtale sec&m bas yet
 developed. Overbsy and Henniger 11 suggested that tluw to five                                        to be extended to any significant degree into Wcod Coumy. As of
 different crudes, ny@g b gravity from 43 to 62”API [0.81 to                                           the end of 1983, only 20 completions in the shale section beneath
0.73 g/cm3], are being prOduc@ from different depths in the area.                                      the Gordon were reported since 1979. Most resulted in some gas
 The bulk of oil production, however, appears to be coming from                                        prcducdon, with opsn flow averaging around 100 McflD
a section about 3C0 to 400 fi [Ql to 122 m] thick at the top of and                                    [2.8 X 103 m3/d] gas, but most wells had little or no oil pmduc-
just above the Huron sbate member (see Fig. 1). Gamma ray logs                                         tirm. The lack of oil productim is probably a result of lower frac-
indicate that me section contains thin siltstopes interbedded witi                                     ture densirj in the section west of the Burning Springs anticline,
light-to mdluin-dark-gray shales. The zone cccprs at a depth of                                        discussed below.

SPE   P.m.,;.”   Evd.,tion,          ficernber      19S7                                                                                                                  423
 Structure                                                                                 hundred feet of ovemhickening in specific parts of the shale sec-
                                                                                           tion, although the indefinite gamma ray characteristics make it
 The Plemants, Wcixl, and Rhcbie counties area is bisected by the
                                                                                           diffictdt to identify specific repeated intervals or to detefmine the
 mott remarkable stmctme of the western Allegheny Plateau, the
                                                                                           exact number of faults present. At least one thrust fault with sig-
 Burning Springs aoticline (Fig. 4). White 12 and Grimsley 13 dE-
                                                                                           nificant displacement apparently cutt the base of the Huron along
 cussed its influence on early oil development in West Virginia.
                                                                                           much, if not all, of the western flank of the anticlbte. The relative
 StNctural maps of M or part of the feature can be found in Refs.
                                                                                           lack of ovenhickening (=500 vs. = 1,600 ff [= 152 vs. =488 m])
  13 through 18.
                                                                                           in these wells relative to the Sandhill well indicates that the thmstz,
    The San&ill well (wocKi-351), drilled to basement on the crest
                                                                                           which have ramped up from the Silurian d6collement to form the
 of the structore in 1955 Fig. 2), encotutterti re ted middle and
                                                                                           stmcture, are dying upward in the shale section.
 lower Devonian sections, leading WcmdwardYm                 ~kvret    ,
                                                                                              Shtmtaker30 presented a two-stage mcdel for the development
 thNsted origin for the stmcture. Rodgerszo and Gwinn21 expandd
                                                                                           of the Burning Springs anticline (1) batement faulting along an
 this, interpreting the Burning Springt anticliie as tie terminal th’uc-
                                                                                           essentially north/south strike (confined by seismic data), be@-
 ture at the western end of a tbrttst sheet, the result of thrusting up
                                                                                           ning in the Cambrian and related to Lbe formation of the Rome
 ward from a d&olJement zone at the Siiurkut t%iii dt level d@g
                                                                                           trough, followed by (2)detachrnent and westward movement above
 the Allegheny orogeny.
                                                                                           the .%linadbllement during the Late Paleozoic Allegheny orogeny.
    The Burning Springs anticline is unique for itt position in the
                                                                                           The location and orientation of the anticline have been attributed
 plateau because of itt high amplitude of 1,600 ft [488 m], steep
                                                                                           to either inchout or offset of the gQde zone along this basement
 dips (up to 70” [1.2 rad] on the west flattk), and nortiisoutb axial                                 t
                                                                                           halt. ZO.3
 strike. The structural map on the base of the Huron shale member                                                                                                       - .
                                                                                              Structures of much lower relief are present east of the Burning
 (Fig. 4) shows the crest of the anticline to be offtet by a series of
                                                                                           Springs antichne, generaUy< 150 tl [<46 m]. Initially, these trend
 transverse or strike/slip faults within the Burning Springs thmst
                                                                                           northkotmh parallel to the major smcmre, but several miles to the
 sheet. COWIS and Smith22 suggested the presence of both the
                                                                                           em the strike of the structures swings to the northeast and p2raUe12
 northernmost fault shown here (Fault A) as well as the fault along
                                                                                           the regionzl structural grain to the eatt (Fig. 4).
 the Wocd/Pleas3ntr County line (C). Calvert” mapped this part of
                                                                                             To date, as Figs. 2 and 4 show, most significant oil prcducrion
 the saucture on the top of the Onon&ga and thought that a trans-
                                                                                           from below the Gordon is west of about 81”05’ and east of tie crest
 verse fault zone was present at this position. Haught 17 IMPFKCI      a
                                                                                           of the Burning Springs anticline, esycially eatt of 81013’. AU but
 right lateral strike/slip fault (Ms Saint Marys fault), which maybe
                                                                                           a handful of the more prcducdve oil wells (> 100 BOPD [> 16
 the eattem extension of the fatdt shown on the anticline at the Ohio
                                                                                           m3/d oil] initial production p]) fall in this band. Continued de-
 River (B).
                                                                                           velopment may alter this relationship somewhat, but it currently
    Gwinn21 showed a fault offsetting the crest of the Burning
 Sminm anticline near the Dosition of the fault shown on this IMP                          appmrs that tie best ofl PlaY f~s ~~n MS band. W=t Of the
                                                                                           Burning Springs anticline, fmcture denziry may be sigmiffcantlylow=
 o; tb; sottthem border of “Ritchie County (D), while Swwztey*i
                                                                                           er in the undetached section. Eastof81 “05’, permeabili~ is sufti-
 identified the southernmost fatdt (E) shown. The exact Iccation and
                                                                                           iiently high to allow significant gas flows but may not be sufficient
 orientation of these transverse faults or shear mnes cannoI be deter-
                                                                                           for high oil production.
 mined ffom the contd avaifable, so all are shown as a dashed line.
                                                                                              It it interesting to note tbzt the eastern edge of the oil play roughly
    These zones of offset in the Bunting Springs structure may be
                                                                                           corresponds to the change in tie               of stmctm’af axes from
 more complex than a simple strike fault. Fault D and, to a Iester
                                                                                           nofthlsmttb to northeastlsouthwest (l%gs. 2 and 4). The correla-
 extent, Fault C can be followed east across Ritchie County as a
                                                                                           tion of these fatures sugge+s a structural difference between the
 band in which structural axes cbnge strike, are offset, !ermimte,
 or decrease in relief (this is more apparem on more delailed maps).                       two areas, resulting in a more productive fracture system west of
 Gwinn21 extended the zone of strucmrat disturbance associated
                                                                                              It is unclear why the area from 81”13’ west to the crest of tie
 with Offset D as a Iineament across the platkau along a strike almost
                                                                                           Bunting Springs anticliie has been somewhat less productive of
 due eatt into Upshtm County some 60 milet [96 km] away. He iden-
                                                                                           oil. Future drilling may result in greater success in tbit area, which
 tified parallel Iineaments beginning at the northern and southern
                                                                                           should be highly fractured. It is possible that some meat 1M%have
 ends of the Bunting Springs anticline and interpreted these as zones
                                                                                           bem .SOhighly fractured throughout the section fhat much of the
 of slip bounding the tbmst sheet.
                                                                                           oil bat escaped, although the number of gc+d gas wells (Fig. 4)
    More recently, two linear zones of apparent structural disturbance
                                                                                           in the area seemz to contradict this.
 in the eastern half of the Wesi Virginia plawau-the Petersburg
                                                                                              The structural picture presented here is simplified. Many more
 lineament23.26 and the Parsons lineament”,H-29 -have been
                                                                                           faults, related to both batement movement and AUegbenian defor-
                                                                                           mation within the thrust sheet, are no doubt present. Some (not ob-
    Although it has not been directly linked with the Burning Springs
                                                                                           vious on Fig. 4) are suggested by more detailed mapping on a larger
 stmcture, the Petersburg Iineament, which passes near Petersburg,
                                                                                           scale. It has long been recognized that production from Devonian
 WV, and striket N85 “E, projects across the plateau to very near
                                                                                           shalet is dependent on fm.cture-enbmced permeability. 31~2 Gper-
 the southern terminus of the Bunting Springs anticline.
                                                                                           ators in the area use both seismic data and linear features (identi-
    More important for Devonian shale exploration are dte conclu-
                                                                                           tied on topographic maps from high-altimde photography and fmm
 sions of Dixon and Wdson29 and Wheeler24 that these zones of
                                                                                           satelIite images) to locate areas of greater fracture iotensity. The
 cross-strike structural discontinuity are areas of intente jointing and
                                                                                           combimtion of these data with detailed structumt maps is needed
                                                                                           to develop a better srrucmral model and history of the area and to
    Fig. 4 shows the location of r+med wels with opm flows greater
 than 100 BOPD and lC@Mcf/D e- r16 m3/d oil and 2.8X 103
                                      gas                                                  explain tie location of petroleum prwhmtion trends
 m3/d gas]. Of interest is the concentration of oil wells in areas a                       Early Production History
 few miles east of the offwt zones on the crest of the Burning Springs                     Because of the high interest in oil prcducdon from the Upper and
 anticline. Apparently, these zones pass eatt into zones of strucntr-                      Middle Devonian Iine-grainfd clastic section, tlti smdy examined
 al disturbance in the tfuwst sheet that are more highly fractured and                     typical production decline during rhe fust 2 years for a set of rep-
 tierefore more permeable and more highly pmducdve. Overbey                                resermlive wells. Forty wells were used in the study, arl located
 and Efettniger11 also related higher production rates to areas of                         between the Burning Springs anticline and 81 “03. AO were com-
 shear faulting in the Burning Springs timst sheet.                                        pleted in rbc J_nwer Huron; however, other mnes were also corn-
    Three wells drilled a few thousand feet west of the cr=t Of the                        pleted in many of the wells.
 anticline, and at least to the bate of the Huron shale, show several                         At least 12 months of montidy oil-production totals were availa-
                                                                                           ble fOr w the walk. wed. More than 12 months of tfm were avail-
 .PMsonal   cornmunic,tion.   Q. CalvWI,   West Mmlnla   U,,           >332.
                                                               Mo!w”!c”w.                  able for 28 welts, and a ftdl 24 momht were ?vaiktble for 11 wells.
‘.mrsaml .amu!ni.athn,        J. Sweemy.   west Virginia Geolegicd   and Economic S.wey.
                                                                                           W* ~d reprted opeII flows tim 10 to 1,403 BOPD [1.6 to 222
  Morgr,”tow,   1934
                                                                                           ~3/d ~fi], ~i~ a mean pf 190 BOPD [30 m3/d Ofl].

 424                                                                                                                    SPE Formation Evaluation, December 1987


       0. a     “   .




                         0,,               .,,,0                 ,,        .,,,.,,   ,,
                                                          .0.,        ”$

       ‘i9. 5-Devonian shale oil-production decline, Ritchie md                              ‘i9- 6—DevOnian shale oil-production decline, Ritchie and
       Veasants counties, WV (average for 40 wells).                                         ‘Ieasmts counties, WV (high IP vs. average 1P wells).

    Fig. 5 shows an average production-decline curve for all 40 wells                          Note that all these welfs were also reported ~ p@uce gas (open
  in’the sample. Each well’s reported open flow was considered to                           flows 40 to 800 Mcf/D [1.1x 103 to 23 X 105 ins/d] gas). Many
 be a va3ue of 1.0 at O months, and the average daily production                            of the wells were not comected to pipelines’in 19g2, so less infor-
 during succeeding months was divided bv the initial rate to deter-                        mation is available concerning gas prcductiori. Avaifable informa-
 mine ~ relative v~ue for each month. Th.&e wdues were averaged                            tion shows that production stabilized at rates between 15 and 100
 for the whole sample and plotted vs. time.                                                Mcfi13 [0.42X 103 and 2.8x103 m3/d] gas after wvqal months.
    The average oil-production decline curve generated in this man.                        Bagnall and Ryan33 showed that Devonian shale gas wells in
 ner show%very steep and steady decline tluougb the frst year (aver-                       southern West Virginia declined very slowly from their stabiized
 age 96%). Standard deviation around the mean (shown by verticsl                           production rates for several years, then prcduced for many more
 ham) shows scatter in the tit months, but much less in Ister months.                      yeas at low rates without further significant dedine. Several years
 The 40 wells in the sample, with an average IT of lPO BOPD [30                            of prcducdon history is needed to determine whether sbde wells
 m3/d oil] and average first-month production grester than 100                             in this area will fOUOwthe same pattern.
 BOPD [16 m3/d oil], were only prcducing an average of 7 BOPD                                  An average of 326 days of production history was availabIe for
 [1.1 m3/d oi3] at the end of the year. For the wells having availa-                       17 walls drilled in the basal Lower Huron/Java/Angola silt.stones
 ble information, pmducficm cmtinued to decline slowly through                             fRifey, Benson, and Akxander) of eastern Ritchie County. Aver-
 the second year. At the end of this period, 11 wells showed a total                      age f~        opa flow on testing of these welts was 640 Mcf/lJ
 avefage decline of 98%.                                                                   [18 x103 rn3/d] gas. production was genefdly stable afler a feW
    At the end of the tirst yea, the most prcducfive wells, in abso-                       months at about 40 to 50 Mcfi13 [1.1X103 to 1.4x 103 m3/d] gas.
 lute and relative terms, were prcducing 48 BOPD [7.6 m3 lb oil]                          ‘f’hewet]s avenged 17.s fvffvfcf[0.5x 106 m3] total gas produc-
 (3P was 1,403 BOPD [222 m3/d oi3]; first- ear decline was                                tion during this period.
 96.6%), and 21% of IF (IF was 50 BOPD [8 m / /d oil], first-year                             This sample of brief production tloma few weifs precludes final
decline was to 10.6 BOPD [1.7 m3/d oil]), respectively. Produc-                           conclusions on ukimate pmducdon. Figures are presented onty as
tion itt the tist w.s31 continued to ddine rapidly, and no oi3 was                        a prelimkuy quantitative estimate of typical early production and
prcduced in the last 4 months of its semnd year. Only 15 months                           dec3iie rates. One major unknown factor is how rapidly the opem-
of &ta were avai3able for the second well, at which time produ-                           mrs attempt to prcxluce particular wells. Another factor that may
ctionbad declined to 13% of IF. After 2 years, both the absolute                          have a major influence on recovery is the techniques used in frac-
and relative best producer was one well flux prcduced 9.9 BOPD                            turing the well. fnsuftlcient data exist at tbk time to comp~e the
 [1.6 m3/d oil], 13% of its 3P (87% decline from 75 BOPD [12                              effectiveness of different methodq however, this should become
m3/d oit]). This rate is exceptional for the 11 wells that had 2 years                    possible over he next couple of years.
of available data, because the overall average production was 2%                              Rapid decline is expected in wells completed in fractured reser-
of fp, and four of the 11 wells had stopped prcducing akogetber.                          voirs. The steepness seen on all the CUI-,WS    shows that most of the
    To compare the decliie rates of initially more productive and                         first year’s production is ffom an initially highly permeable frac-
less productive we31swith the average decline rate, the sample was                        mre system. Either this system c+I be largely drained in 12 to 18
divided into two groups based on 3P (Fig. 6). One group contained                         months, or the fractures can close up enough during this time to
the 20 wefls with higher reported W’s (mean fP=351 BOPD [56                               reduce permeability signiticantiy.
m3 Id oil]) and the other group contained the 20 wet3s with lower                             On the basis of the data, it ~pears that few, if any, of these wefls
IP’s (mean LP=43 BOPD [6.8 m3/d oil]). A sepafa.te average                                will pfcduce more@         a couple of birrels of oil per day after the
decline curve was generated for each set in the manner described.                         second yesr. Devonian shafe gas we31shave t@itionaUy prcduced
The more productive wells show steeper decline in the first few                           stnafl amounts of gas for long periods. This gas has represented
months. At the end of 15 months, these weUs were prcducing an                             prc.iuuion from the mck matrix, which slowly reaches the we31
average of about 1% of their 2P, or about 3.5 BOPD [0.5 M3/d                              through fracmre systems The rock matrix might not be sufficient:
oil]                                                                                      Iy permeable to maintain significant oil-production levels, so these
  Prcducdon in the other 20 weh had declined from 43 BOPD                                 wefls would have short fives as ol-pmducers.
[6.8 m3/d oil] to about 5% of that level, or just over 2 BOPD [0.3                            in fact, 4 of the 11 wells (for which 2 years of prcducdon histo-
m31d oi3]. Both sets of wdts showed rapid decline, but the more                           ry were available) had smppd producing oil by tie end of.this peri-
mpid decline in the first set resulted, in absolute numbers, in a differ-                 cd. Longer production histories from more wells are needed to reach
ence in average orcduction rates between tbe two moum of 1.5                              a conclusion concerning long-term oitprcduction, but the evidence
BOPD [0.2 my /~ oil] after starting with a differenc~of more ti”fi                        mgges~ tit much of tie production wiU come in +e first 12 to
300 BOPD [48 m3/d oil].                                                                   18 months and that short prcdttctive life may be common.
SPE         FwIII,ticm         Evdwtion,           December 1987                                                                                             415     >
  The decline curves can be used to estitite typicsd oit reserves           GmloH SYmpmiurn,                          M           W
                                                                                                ERDAMERC/SP-76i2, orgamown, V(1976)
fm time wetls. Overatl, avenge stating apn flow for oil-producing
                                                                         4. Patchen, D.G.: ‘-subsurfaceStmtigraphyand Gas productionof the
wells in the main play has been about 40 BOPD [6.3 m3 /d ofl].
                                                                            Dwoniao Shaks in WestW@da,” ERDAMERC/CR-77/5,NforEm-
About half of the we!.fsdrifled have had only gas production repmt-         town,  w   (1977)35.
ed, making the overall average about 20 BOPD [3.2 m3/d oiI]. If          5. Patch.”, D. G.: “Terminology and Cm’retationof Middle and Upper
this value is plugged into the low-fp curve of Fig. 6, average first-       Devonian Clastic Formations,’> Mounmin SIate Geology (Lkc: 1977)
year production would be about 2,00J3 bbl [318 m3 ], with a pro-            4-9.
duction rate at the end of that time of about 1 BOPD [0.15 m3/d          6. Neal, D.w.: 4Wbsurface Stmtigraphy of the Middle and Upper D:VT
oil]. Second-y- prcducfion of about 21X3 3C0 bbl [32 to 48 m3 ]
                                            to                              tian Clastic Sequencein SouthernWest Virginia and Its Relationto
wotdd be expected. After the second year, production becomes un-            Gas prcd”uim,’, PhD disswlaticm,West VirginiaU., Morgantown
certain.                                                                    (1979).
                                                                         7. Dowse,M.E.: “The Subsurfacektratigmphy of the Middle and Upper
   The dat8 used in this study suggest that many wells will have            hOlli.411 Ck.9iC sequence in Northwestern West Virginia;’ PhD diS-
a short prduc five life, so tbfal prcducfion of about 3,0C41 [477           senzdi.m, West Virginia U., Morgantown(1980).
m3] of oil per well might be a reasomble average. This rough             8. Martens,J.H.C.: Well .%mpfe Records, West Vtiginia Geological and
reserve estimate.may seem very low, but remember that it includes           EconomicSurvey, Momntown (1945) 17, 889.
theentire play, thui also weUs that produce no oif. Cenain areas         9. CardweU, D. H.: “01 and Gas RePrt and Map of GJmer and Lewis
have been more productive than others (such as the shear zones              Counties, West Virgiok” WVGeological and .%omnnfcSurveyBull.
discussed above), and wells in these areas will have I@her aver-             18A, Mor#ntown (1980) 55.
age reserves. Certainly, individual wells have been far more            10. Cardwdt, D.H.: .’01 and GasReportandMapof DcddridgeandHar-
productive-some producing as muchas70,0CH3bbl[11 129 m3]                                                                    and
                                                                            rison Coundes,WestVirginia,” WVGewlogicuf Economic Survey
                                                                            Bu[[. 16A, Mo,gantown (1982) , 55.
of oil in the first year.                                               11, OverLxy,W.K. and Henniger, B.R.: “Development o? Od and Gas
  fn addition, as operators become more experienced in this new             Production from Devonian Shales and Sittstonesin Plmam.s and Ritchie
play, they may learn optimum ihmtring and prcducfion techniques             Coundes, West Vi@ia,’” paper presentedat the 19S3WV Oeolo$-
that could increase reserves signiticanfly.                                 G4and Economic Sumey Annual AppalachianPetroleum &ology Syim
                                                                            posium, Morgantown, March 2P-31.
Conclusions                                                             12, White, 1.C.: ‘dPefmleumand Namral Gas, Praise Levels, ” WVGe&
                                                                            fogical and Economic Survey Bull. 1A, Morgamown (1904) 1A, 625.
   1. The Upper and Middfe Devonian shale section of western West
                                                                        13. @’imdeY.G.P.: CbwuyRepons     andMap, Pkmnts, Wacd, at!dRifch-
Virginia has been subdivided into stratigrapfdc units correlated to         ie Gxmdes, WV GeologicalandEconomicSurvey,Mozgantovm         (1910)
Ohio and New York outcrop belts by several previous authors.                .-

   2. These wdts are generally feadily identified in the area and can   14. Wdscm,T.C.: ,-The Burning Springs-VolcanoAnticline, West Vti-
usually be distinguished consistently on the basis of specific gam-         ginia,” PhD dissemadon,Comelt U., Ithaca, NY (1951).
ma ray density log characteristics presented here.                      15. Stmckey,P.M.: ..Some .&Fcts of the SurfaceGeologyof tie Nmth-
   3. Although shale production was apparently first developed in           ern Portion of the BurningSpringsAmidine,” MS thesis, West Vk-
 1939, development of tie re.wuice did not begin in earnest for more        ginia U., Morgantowm     (1965).
than 40 years afterward. Development began in the relatively silty                                                                 W
                                                                        16. Haught, O.L.: ‘“Oiland GasReportandMapof Plea$?rds, eed, and
                                                                            Rldde Comties. West Vimiti.’, wVGeoioxfcoland Economic Sur-
top few hundred feet of the Upper Devonian section (including the
                                                                            vey Buft. 11, Morgamown-(19S6) 1. 2        -
Gordon zone) and proceeded into deeper zones. Prinmfily gas has         17. 3faught, O,L.: ‘ODandGasbiap of Plwsants,W@cd,   andRitchieCoun-
been developed in eawem Ritchie County where siltstones in the              ties, WestVirginia,RevisedEdidon,,2Geologic4and EconomicSur-
lower half of the upper Devonian don         @asal Huron member,            ,,,. . Mor.zammm [1966):
                                                                               .. . .
Java formation, and Angola member) have been primary objectives.        1S. CardweU, D.H.: ‘;Deep”well and Structi GeologicMap of West
In western Ritchie and Pleasants counties, both oil agd gas have            Virginia,,,WV Ge@icd andEconomicSurvey,Mo-wn               (1973).
been developed, with oil production concentrated in a silty mne         19. Wcodward, H.P.: ‘Wrucmmt Interpretationsof the BurningSprings
near fhe top of the Huron.                                                  Amid%,, 27w      QmfWl Deep WeU,Wood Chunfy, West l+rginia,WV
  4. Shale production depends on encountering hydrocarbons                  G@logical and EconomicSurvey s+18 (1959) 159-68.
                                                                        20. Rcdgers, J.: “Mecb8nicsof Appatachim Fordand Foldingin Penr-
@ap@in natural fractures. Structural mapping suggesk that areas             sylvti and West Virginia,,, ~G Bulletin(Aug. 196S)1527–36.
cotuammg concentrations of highly prdmfive oil wetts are bands          2,, G~, V,E,: “~.~               T~~~ rntie p~u ~ N~fi-m
of stmctoml disturbance related to shearing witbii the Burning                                                       A
                                                                            VatIeyand RidgeFlovincesof the Cenh’aJ ppalachians,”GSABulk-
Springs thrust sheet. These may be areas of greater fmco.we demity.               ._.r.. —.,,
                                                                            fin {Sem. t96-f) 863-90R
                                                                                        .. .—.
   5. Although significant open flows of both oil and gas can be        22. Collins, H.R. and Smith, B.E.: “Geology and MineralResourcesof
encountered in shale wells in this area (> 1,IY13BOPD, >2,003                                                                    S
                                                                            WashingtonCounty,Ofdo,’,OhioDivisionof Geological urvey,U
Mcf/D gas [> 159 m3/d oil, > 57x 103 m3/d gas]), oil produc-                66, Columbus(1977) 1S4.
tion rates declined steeply in the firw year (up to 11X3 ) and stabi-   23. Wleder, R.L.: “Cross-S  frike StructuralDisccmdnuitiesPosifoleEx-
lized gas flows are typically 103 Mcf/D [2.8x 103 m3 /d] gas or             PlmationTcol for Natural Gas in DetachedAPPakhim Forehand,,’
                                                                            Pro..,   western Limitsof Deta.dmemandRelatedSuucturesm the Ap
                                                                            mlachianForeland.DOEMETUSP-SOL23, orwntowm.M           w (Am’iJ
                                                                            i980) 41-55.
Acknowledgments                                                         24. Wheeler, R.L.: ‘<Cross-StrikeSfmctural Dkcondnnitks: Possz%leEx-
I thank yassociates at the West Viiinia Geological and Economic
       m                                                                   ploration Teal for Natural Gas in Appafachim Overibmst Belt,” MG
                                                                           Bulfefin (Dec. 19s0) 41-55.
Survey for their help in preparing this paper. Doug Pntchen and
                                                                        25. Sites, R.S.: “St!uctum3Anatysi.s tie Petersburg Lineament,Cen-
Katharine Awmy read the mamwa’ipt and provided many usetid sug-             ti Appdacbians,” PhD dissertation, West Virginia U., Morgantown
gestions, and Fred Whroyer carefully edited the text. Cindy Wil-            (1978) 171.
liams is to be thanked for her typing, and Ray Stmwser for drafting     26. KuIander, B.R. and Dean, S.L.: ‘Ilavify, Magnedcs, and Skucture,
of the illustrations. This paper is published with the approv+ of           .kfleghenyPtafeaulWestem Valley and Ridgein WestVirSiniaandAd-
the State Geologist of West Virginia.                                       jacent States,” WV Oeologicafand EconomicSurveyRS-27,Mor@n-
                                                                            fown (1978)91.
                                                                        27. wheeler, R.L. er al.: “Field Studyof the ParsonsL.imanmt, Tucker
                                                                            cc,my, w (abs.),’%    GSA.46s withProgmnu, 8, No. 2 (1%’6)298.
References                                                              28. Trwnbo, D.B.: “The paxsonsLiieament, Tucker County, West Vir-
 1.Schwietafrg,J.F.: “DevonianShalesofOhioandTheirEa.stem     Equiva-       ginia.,” MS thesis, West Virginia U., Morgantmvn(1976).
    lents,>,PhD dissertation, Ohio State U., Columbus(1970).            29. Dixon,J.M. andWilson,T.H.: ‘<The     parsons Cross-StrikeStructmat
 2. .%hw(eterkg, J. F.: ‘LDevonimShates of Ohio and Their Eastern and       Discontinuityas an ExplorationArea for Fracture Gas Reservoirs,”
    Soutbem E@ivdenfs,” Contract No. METcICR-7912, U.S. DOE,                Thbd EasternGasSha3es    Sympium, DOE METC/SP-79/6,Morgan-
    Morgantow”, WV (1979).                                                  tow”, w (Oct. 1979)407-14.
 3. Patchen, D,O. and Larese, R.E.: “Stratigraphyand Petrologyof the    30. Shumaker,R.C. : ‘The Effect of Basement.Slmcturem Sedimemn-
    Devonian‘Brown,in West Vi@da,>>Proc. , Seventh APPdacbhn Pet.           tim Wd Detached Stmctuml Trends WitJin tie Appalachian Basin
426                                                                                                SPE Formdon Evaluation.December 1987
      (ah),”GSA NE& SE Secdon.s Meeting,   Washinsfon,DC (March          Sl Metric Convemlon Faotors
                                               Shale.” Ap@chian
31. Merty, R.C.: “@cnrremces of Gas in L3evonian
                                                                                    bbl X 1.5S9 873   E–01 = m3
    &ological Se.+ Syqmsium on Devonian shales, Charleston, WV                         ft X 3.C48*    E–01 = m
    (1933) 14-15.                                                                  miles x 1.609 344* E+(KI = km
32. Bfllingsley,J. E.and Zebid, W,O.: “PomsifyandResemoirFacili-
    ties of the Devonianshale,>’AppalachianGWIosic!zl wsietySympc-       -C-mwmm     Iaclor   isexact.                                            SPEW
    simnon DevonianSbaLes,ChmIeston,WV (1935)21-23.
33. sasnall, W.D. and Ryan, W.M.: “The Geology, Reserves and Pm-
                                                                         Orlglnd SPE man”6c’lPt ti[ved    !0! !avhw May 16, 19W Ps$ar acqsted for Publb8.
      ducdon Characteristics of tbe Devonian Shale in Souihwcstem West   110” S4Pt. 18, !926. Revisw msrusz+P! IK+iwd  Dec. 18, WM. PeF.3r [SPE 12834) flrat
      Virginia,’, Proc., seventh Appalachian Pemkum GeQIogySympxi-       PmnW.1      the 19~ sp~OWGRl       Unw.wnUone!     Gas %wvev     Ewnwstum   held h
      um, ERDA MERC/SP-72/Z, MOrg?mtovm,WV (1976)41-53.                  Pm9buqh,   May 1s-15.


SPB   Fomaticm   Evaluation,   D&ernkr   19S7                                                                                                          427     ‘

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