Dawson Geophysical Eprint 0707.qxp - Dawson Geophysical Company by cuiliqing


									                                                                  JULY 2007

The “Better Business” Publication Serving the Exploration / Drilling / Production Industry

   & Seismic

                         Barnett Shale
                         Beneath DFW

                                                      Reproduced for
                                                      Chesapeake Energy Corporation &
                                                      Dawson Geophysical with permission
                      Bustling DFW Airport
                    Creates Unlikely Setting
                    For High-Fold 3-D Survey
                     To Image Barnett Shale
By Tim Beims
   OKLAHOMA CITY–The Dallas/Fort Worth International               around the globe.
Airport is one of the busiest and largest commercial airports on       Little do the 60 million passengers who pass through the 174
the planet. Every day, more than 2,000 flights land and take off   boarding gates each year realize that under their feet is the very
from 80,400 feet of runways and taxiways laid out over 29.8        stuff that makes the convenience of modern air travel possible.
square miles–bigger than the island of Manhattan–ferrying more     From the high-octane fuels that propel jets into the skies, to the
than 165,000 passengers and 2,300 tons of cargo to destinations    compressed natural gas that powers buses and trams to check-in
                                                                   counters and rental car lots, hydrocarbons make it all go.
FIGURE 1                                                               About a mile-and-a-half beneath the airport, far removed from
    DFW 3-D Survey Source/Detector Locations                       the hustle and bustle on the surface, is a thick, dense blanket of
         and Fold Attributes (All Phases)                          Mississippian-age rock (350 million years old) that has proven
                                                                   a prolific source of hydrocarbons–specifically, natural gas–across
                                                                   the Fort Worth Basin. DFW Airport is smack in the middle of
                                                                   Barnett Shale country. In fact, countless oil and gas profession-
                                          Phase 1
                                                                   als have undoubtedly traveled through DFW in support of Barnett
                    Phase 5                                        Shale projects in the Dallas-Fort Worth area. But for Chesapeake
                                                                   Energy Corporation, the airport itself holds the ticket to expand-
                                                                   ing the company’s presence in the red-hot play, says Larry
          Phase 2                                                  Lunardi, Chesapeake’s vice president of geophysics.
                                                                       “The Barnett has been arguably the fastest growing gas play
                                                    Phase 4
                                                                   in the world, and we are aware of precious few opportunities to
                                                                   lease so much contiguous acreage,” relates Lunardi, noting that
                                                                   the chain link fences surrounding the airport’s perimeter encir-
                                                                   cle 18,076 acres untouched by a drill bit. “The airport not only
                                                                   represents one of the single largest remaining Barnett Shale lease
                      Phase 3                                      opportunities, but this acreage likely contains one of the thickest
                                                                   and best-developed reservoir facies anywhere in the play. That is
                                                                   the biggest reason we are so excited about the DFW project.”
                                                                       Chesapeake reached a leasing agreement with the Airport
                                                                   Board of Directors in August 2006 whereby the company agreed
                                                                   to pay a $181 million initial bonus and a 25 percent royalty on
                                                                   all gas produced from wells drilled on the property. But for DFW
                                                                   to receive royalties, Chesapeake has to drill productive wells.
                                                                   And before Chesapeake can drill, it has to know where and how
                                                                   to place well bores to hit sweet spots in the ultralow-permeabil-
                                                                   ity shale, points out Kevin Werth, senior geophysicist in charge
                                                                   of 3-D seismic acquisition and design at Chesapeake Energy.
                                                                       So as unlikely as a sprawling airport complex may seem as
                                                                   a location for a 3-D seismic survey, for a few months last win-
                                                                   ter, the drive to work for Dawson Geophysical’s crew number
                                                                   25 ended on International Parkway, the main thoroughfare to
                                                                   and from the airport’s five terminals. With three Federal Aviation
                                                                   Administration flight control towers looming ever-watchful in
                                                                   the background, Werth reports, the crew acquired 32 square
                                                                   miles of high-density 3-D data in five overlapping phases for
SpecialReport: Geophysics & Seismic Acquisition

   “As an old doodlebugger who has been acquiring seismic
data for 27 years, it was incredible to see a vibrator truck shak-
ing on a taxiway just behind a commercial jet with rows of air-
craft lined up at terminal gates in the background,” Werth re-
lates. “Standing there watching all this, all I could think was
‘Wow! Here is something I never could have imagined.’”
   The last of the data were acquired in late March, and Werth
says Chesapeake has since moved five drilling rigs onto airport
grounds as it spuds the initial DFW Barnett Shale wells.
Five Puzzle Pieces
    Because of airport operational issues with aircraft landing
and departing, and with a litany of security, FAA, environmen-
                                                                      After signing a leasing agreement with the Dallas/Fort Worth
tal, safety and Airport Board requirements, Werth explains that       International Airport–among the world’s four largest airports in
Chesapeake had to design and acquire the survey in separate           terms of land area–Chesapeake Energy began surveying oper-
phases, which were then pieced together as a single 3-D data          ations last December to acquire high-resolution 3-D seismic on
set (Figure 1).                                                       the 18,076 acres within the airport’s perimeter. The company is
                                                                      now commencing a horizontal drilling program targeting the
    “There was no way to shoot it all at once, but DFW is so          prolific Barnett Shale.
large that we had lots of room to work outside the airport’s main
core area where the terminals are located. The phases over-
                                                                     other parts of the airport away from where we were working
lapped one another so that when the puzzle pieces were joined
                                                                     on a particular night. We never had to deal with planes coming
at the end they created one strong, robust 3-D survey. The first
                                                                     into the areas where we were acquiring data.”
four phases were outside the high-security core area. The final
                                                                         Even so, airports are noisy places, no matter the hour. So be-
survey covered the concourse, terminals, runways, taxiways,
                                                                     fore data acquisition got under way in December, Werth says
towers, maintenance buildings, etc.”
                                                                     Chesapeake and Dawson conducted extensive on-site testing
    Although it certainly sounds complicated, merging the data
                                                                     as part of its presurvey planning to determine how all the nois-
from the five phases was relatively simple, Werth contends.
                                                                     es associated with traveling through the air could affect the
“The biggest chore in the design stage was to make sure we had
                                                                     recording of sensitive seismic energy traversing the earth.
sufficient coverage to prevent low-fold wings around the edges
                                                                         “After several introductory meetings with the Airport Board
of the phases when the data were tied together. Although Dawson
                                                                     to explain all the operations we had planned, we brought in vi-
shot and processed the individual phases separately, each phase
                                                                     brator trucks from a local crew for source and noise testing. By
was cut from the larger 3-D survey, which meant they were tied
                                                                     understanding noise trains from the airport, we could align the
by bin, azimuth, placement in the subsurface, etc.,” he states.
                                                                     geophones to best accommodate noise,” he imparts. “We also
“Once all the data were processed, it was easy to put everything
                                                                     demonstrated through peak particle velocity testing that the vi-
together. There are very few issues with the data. The quality
                                                                     brators caused very little particle movement. We imposed buffers
is excellent.”
                                                                     around some of the critical buildings and underground infra-
    The data from each phase were processed concurrently while
                                                                     structure, but the testing showed airport officials exactly how
the next phase was being shot. “We were anxious to get the
                                                                     the vibration and recording operations would work.”
processed results into our interpreters’ hands,” Lunardi says.
                                                                         One significant concern for Chesapeake was the 17 inches
“Great pains were taken to get each phase processed as quick-
                                                                     of special reinforced concrete covering the runways and taxi-
ly as possible so we could begin making drilling plans and get
                                                                     ways, Lunardi adds. Would a thick layer of concrete impact the
permits filed and approved by the DFW Board. For each of the
                                                                     transmission of source signatures from the vibrator pads into
phases, it was a matter of a few days rather than weeks between
                                                                     the subsurface, or the reflected energy back to the surface?
taking the last shot and delivering a useable data volume to in-
                                                                         “We were afraid the source signal would travel perpendicu-
                                                                     lar to the runway system instead of into the earth, but fortunate-
    The survey was designed with much higher fold than a typ-        ly, that turned out not to be the case,” he says. “In fact, the data
ical Barnett Shale 3-D project to achieve maximum resolution         quality may have been slightly better where we vibrated on con-
and spatial coverage, Werth notes. “We knew we were not go-          crete. That is probably because of the exceptional coupling be-
ing to be able to get back in anytime soon to reshoot data, so       tween the concrete and the ground, which eliminated source-
we had to make certain we had adequate data quality,” he ex-         generated energy and noise moving horizontally along the
plains. “Also, we were not entirely clear as to how vibrations       runway system.”
from jet engines or aircraft landings and takeoffs would impact          That came as particularly welcome news, because just as the
seismic recording. In the end, we decided to shoot very high         Dawson crew moved to the airport’s core operations area, Werth
fold to accommodate any statistics we might need.”                   notes that the DFW Board informed Chesapeake that the vibrator
                                                                     trucks needed to remain on concrete wherever possible. “We went
All Night Long                                                       into it thinking we needed to discharge sources between runways
   Part of the solution was to conduct all acquisition operations    and anywhere else we could find a piece of unpaved ground, but
during nighttime hours when air and land traffic were greatly        for airport operational reasons, the airport preferred it the other
diminished, Lunardi points out. “The seismic crew generally          way,” he states. “If we tracked a bit of dirt onto the concrete–even
worked between the hours of 11 p.m. and 6 a.m. DFW still has         mud from the crew’s boots–it had to be immediately cleaned.
200 flights a day during those hours, but traffic was routed to      Airport sweepers were constantly cleaning the concrete.”
SpecialReport: Geophysics & Seismic Acquisition

                                                                      square miles in each phase. “The geophones stayed in place un-
                                                                      til that phase was completed, with the vibrator trucks shooting
                                                                      wherever they could,” Werth explains. “Each phase took two-
                                                                      three weeks to shoot, after which time the geophones were
                                                                      picked up and laid out for the next phase.”
                                                                          The project kicked off in the northern part of the airport,
                                                                      which has access to a nearby natural gas pipeline. “We decided
                                                                      to start both seismic acquisition and drilling in the northern sec-
                                                                      tion, because we will be able to immediately market production
                                                                      in that area,” reasons Lunardi. “The goal for Chesapeake, as well
                                                                      as the DFW Board, is to move the development process along
                                                                      as quickly as possible to get to production.”
 Seismic surveying operations at DFW were conducted daily be-             The first well–a vertical disposal well drilled through the
 tween 11 p.m. and 6 a.m. Although air and surface traffic were       Barnett Shale to the underlying Ellenberger formation–was
 greatly diminished during nighttime hours, the airport still had     spudded in early May, providing the first “real world” control
 200 flights each night that had to routed to parts of the airport    data for the Barnett and Ellenberger zones acquired on airport
 away from where the crew was working.
                                                                      property, according to Lunardi. “The vertical well provided us
                                                                      a control point for structural considerations in terms of reser-
   According to Lunardi, another key aspect of the noise study        voir thickness, quality and measurements,” he remarks. “The
program was assessing how the radio frequencies of the I/O            3-D data correlated seamlessly with data from the first well.”
RSR™ (remote seismic recorder) cableless system might in-                 Since then, Chesapeake has spud multiple horizontal wells
terfere with airport communications. “The FAA was afraid the          intended as producers, and has five rigs on location drilling hori-
RSR towers that communicate with the geophone boxes could
                                                                      zontally from five pads, Lunardi continues. “The drilling plan is
interfere with airport radio frequencies,” he relates. “Thankfully,
                                                                      based on 500-foot lateral spacing, which is what we typically
the RSR system operates far outside the bandwidths the airport
                                                                      have used in the good part of the Barnett Shale. With that spac-
uses for its radio communications, so that was a nonissue.”
                                                                      ing, we can drill up to 10 horizontal wells from a single pad,” he
Designed For Density                                                  says, noting that the top of the Barnett is at ±7,500 feet at DFW
   The high-fold survey was designed with a density of 256 de-        and averages 400 feet thick. “Most of the wells will drill verti-
tector and 205 source locations per square mile. “We bumped           cally into the top of the shale, turn within the shale, and then drill
up the sweep effort only nominally, because we were statisti-         3,500-4,000 feet of lateral through the lower part of the Barnett.”
cally so much heavier on the sourcing than is typical in the
                                                                      Any More Airports?
Barnett Shale play that we felt the distributive energy of the
sources would definitely account for some of the noise issues,”          Despite the obvious challenges associated with acquiring 3-
Werth says.                                                           D in the shadows of rumbling 450-ton Boeing 747s in an envi-
   The only cables used with the RSR radio telemetry system           ronment of never-ending noise and activity, Lunardi quips that
are local to a box and six geophone takeouts, Werth points out,       Chesapeake only wishes there was more than one airport the
which simplified data acquisition in parts of the airport where       size of DFW in the Barnett Shale play. “I learned that I love
surface obstacles made “hard wiring” difficult.                       shooting seismic on airports,” he enthuses. “I keep telling our
   “We designed for 256 receivers per square mile, but of course,
you have to take whatever you can get. Because of the system’s
flexibility, we were able to put down a remarkable number of
geophones,” he says. “In addition to everything associated with
the terminals and runways, we had to shoot around road traf-
fic, a golf course, ponds, a lake, construction sites and other
obstacles. There are major interstate highways running through
the northern part of the survey and International Parkway bi-
sects the airport north-to-south. I have no idea how many vehi-
cles travel through DFW in a day, but I can tell you it is a lot.”
   The heavy volumes of traffic added yet another layer of com-
plexity to managing project logistics. Besides thousands of
planes and aircraft support vehicles, Werth notes that the survey
also had to contend with cars and trucks buzzing around. “We
had worked in high-traffic urban areas before, so we knew the
key was preplanning on the crew level to make sure everything
ran smoothly,” he comments. “Nighttime traffic was not nearly          For a few months last winter, the drive to work for Dawson
as heavy as during daytime, but it still presented serious opera-      Geophysical’s crew number 25 ended on International Parkway,
                                                                       the main thoroughfare to and from DFW’s five terminals. With
tional and safety issues. The crew did a terrific job working          three FAA flight control towers looming ever-watchful, the crew
around all the hazards.”                                               acquired 32 square miles of high-density 3-D seismic data in
   The geophone arrays and communication towers were lo-               five overlapping phases for Chesapeake, with the last phase
cated in dirt areas between runways, terminals and other facili-       covering the high-security core area containing the concourse
                                                                       and terminals.
ties, and laid out as a single static spread covering five or six
SpecialReport: Geophysics & Seismic Acquisition

                                                                      minimizing impact to the ground to controlling carbon dioxide
                                                                      emissions before we could step foot on the airport. The FAA
                                                                      was a separate entity, as was security, health and safety, etc. We
                                                                      had to comply with all these requirements, but everything fell
                                                                      under the Airport Board’s authority.”
                                                                      Step By Step
                                                                          Rather than trying to get approval for the entire project, the
                                                                      survey work was submitted to the DFW Board by phase, start-
                                                                      ing with the northern-most area, which was the least involved
                                                                      in daily airport operations. “We gradually worked our way
                                                                      around the airport and finished with the highest-security phase
                                                                      covering the core operational area in the center,” Lunardi re-
                                                                      calls. “The total time it took to get all the approvals was exten-
                                                                      sive, but approaching the approval process step by step made it
                                                                      much easier and allowed work to proceed on one phase while
 Chesapeake credits close cooperation with airport authorities        other phases were still undergoing approval.”
 and due diligence in the planning and design stages for trou-
 ble-free operations on the ground as well as a high-quality data         Security requirements were relatively minimal on the first
 set covering the geology beneath it. Chesapeake even main-           four phases, but they heightened dramatically once the final
 tained a temporary office at DFW to better coordinate day-to-        phase got under way, Werth notes. “When we moved into the
 day field work with airport and FAA administrators. Here,
 Dawson Crew Chief Ben Gonzalez (left) and Chesapeake Project
                                                                      airport operational area, the members of Dawson’s crew 25 had
 Manager Dave Leopold (second from left) discuss operational          to have identification with them and be escorted by badged se-
 plans with DFW Project Manager Galyn Black (third from left)         curity staff at all times,” he says. “All crew members working
 and DFW Operations Manager Steve Tobey (right).                      in the core airport operations area. We also had lots of traffic
                                                                      control restrictions, and our vehicles were flagged.”
land department, ‘Let’s find another airport!’”                           Werth says that even with all the preparatory work that went
    The reason is simple. With permitting and regulatory proce-       into planning the high-fold, high-resolution DFW survey, the
dures becoming more and more burdensome, Lunardi says DFW             final design had to be modified on the fly time and again to ac-
gives Chesapeake access to a large expanse of acreage under           commodate surface obstacles, work hazards and operational re-
the control of a single entity. “We now are working eight 3-D         strictions imposed by airport regulations.
seismic projects in the Barnett Shale, and we have shot at least          “We laid out the initial design during preplanning and then
a dozen over the past couple years. All of them are smaller,          started incorporating all the operational restrictions, security
much more time consuming and much more difficult in just              and safety requirements, surface obstacles, hazards and the cul-
about every detail, largely because we are dealing with hun-          tural inventory–including buried pipelines, water lines and elec-
dreds or even thousands of landowners and lessees–a tremen-           tric lines. As we went through this process, we built multiple
dous complexity of small acreage tracts–and numerous regula-          sets of models for each phase to work through all the issues
tory agencies,” he explains. “Give me a big airport any day.”         while satisfying our geophysical goals,” Werth reflects. “We
    The ability to streamline the approval and permitting process     had to change the operational plans for all the phases many
under the umbrella of the Airport Board of Directors expedited        times during the planning and approval processes, but the Airport
project scheduling, Lunardi adds, even though the scope of the        Board and the FAA were extremely cooperative. They bent over
field work involved high-level security and operational consid-
erations. “The approval process was absolutely crucial to the
ultimate success of this survey,” he relates. “In fact, it probably
was as important as the field operations themselves.”
    Chesapeake maintained a temporary office at DFW staffed
by Dave Leopold, the company’s project manager, who served
as a liaison to airport and FAA administrators. “We could not
have succeeded without (Leopold),” Lunardi contends. “He was
the go-between for getting approvals for all the work we did,
and he communicated with the DFW Board and the FAA dai-
ly. It was not a very enviable job, but the relationships he forged
with key airport personnel made life so much easier for
Chesapeake and Dawson.”
    Lunardi says the survey was shot under a single permit is-
sued by the DFW Board, but that at least a dozen other agen-
cies and groups had particular requirements that had to be sat-        Drilling rigs are now part of the everyday scene at DFW as
isfied–from security, to environmental, health and safety, and         Chesapeake drills horizontal Barnett Shale wells based on the
air traffic control.                                                   3-D data. The first well–a vertical disposal well drilled through
    “For example, although the average traveler is probably not        the Barnett to the underlying Ellenberger–was spudded in ear-
                                                                       ly May and Chesapeake has since moved five rigs on location
aware of it, DFW is very environmentally conscious,” he states.        to drill horizontal production wells at 500-foot lateral spacing.
“We had to provide best management plans for everything from
SpecialReport: Geophysics & Seismic Acquisition

backward to make the project work.”                                   pectations,” he remarks. “The signal-to-noise ratio is fantastic,
                                                                      the tie-in to our first vertical well is spot on, and we have a very
Smooth Operations                                                     detailed drilling hazard map for the Barnett Shale section un-
   Cooperating with airport authorities in the upfront planning       der the airport, which from a geophysical perspective, was the
and design stages paid off when it came time to acquire the data,     purpose of this survey.”
Lunardi says. “The presurvey conceptualizing and preparation              As a ubiquitous geologic feature underlying the Fort Worth
were far more onerous and difficult than the field operations. I      Basin, there was no doubt that Chesapeake would find the
think we were all a little surprised by how smoothly everything       Barnett Shale at DFW. However, the airport is located near a
went,” he recalls. “The survey operations came and went in the        major thrust system to the east that creates a natural boundary
blink of an eye without any real issues. There is no doubt that       to the Barnett play, Lunardi explains. The 3-D data are helping
was the result of the meticulous planning that was done before        Chesapeake resolve fundamental reservoir questions–namely
a single geophone was set down.”                                      continuity and faulting–that will help shape drilling and devel-
   Werth agrees, adding that the relationships Chesapeake and         opment work going forward.
Dawson forged with DFW officials throughout the planning                  “We ended with a simple 3-D map that shows the shale is
and approval processes contributed to quick resolutions when          largely intact and is not broken up by faults, as we had feared,”
problems did arise in the field. “We had far more angst in de-        he reports. “There are a couple significant faults that we have
signing the survey than anything experienced while actually           precisely located with 3-D, and we can adapt the trajectories of
shooting it because of the cooperation from DFW officials,” he        horizontal wells to avoid those areas. We are very pleased with
avers. “If a situation was encountered, it was immediately ad-        how well the survey went and with the data set that was acquired.”
dressed. Being able to adapt so quickly without missing a beat            And if a vibrator truck looked a tad curious thumping on a
was testimony to the level of coordination and communication          runway, imagine peeking out the cabin window of a jet taxiing
with the Airport Board.”                                              out for takeoff at DFW Airport and seeing the usual planes, bag-
   At the end of the day, it was due diligence in the design work     gage tractors, terminal buildings and trams, as well as the oc-
that led not only to trouble-free operations in the field, but also   casional rig drilling for natural gas. “Drilling rigs will be part
to a high-quality data set beneath one of the more imposing           of the scene for a while at DFW,” Lunardi concludes. “With the
man-made features on the Dallas-Forth Worth landscape,                3-D survey completed, we plan to drill wells continuously for
Lunardi relates. “The data quality is better than our wildest ex-     at least the next few years based on the data.”

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