The answer is many of the newer subsea wells are accessing deeper, higher-pressure reservoirs, which can only deliver product to nearby existing infrastructure (platforms and pipelines, designed for lower pressure fields) to remain an economical venture. Most subsea valves do not have limit switches as they are considered unreliable and unnecessary; limit switch technology is limited in the water depths so valve status for subsea wellheads is inferred through monitoring of the hydraulic pressures to the valve actuators.
Subsea system worries High integrity pressure protection systems (HIPPS) have been around for years, but industry seeks new version for ocean ﬂoor use By William M. Taggart IV W hy is the offshore oil-and-gas sector struggling with writing a new standard for an old subject? It has to do with the unique location where these new high integrity pressure protection systems (HIPPS) will locate—subsea. As the oil/gas industry moves into deeper and deeper waters, the tool of choice is increas- ingly becoming subsea production. Locating the classic Christmas tree well head on the ocean ﬂoor saves the weight and cost of the pipes required to extend those wellheads to the surface, but it also involves changing the well- head into something resembling a NASA project. With subsea wells going in at 10,000 plus feet where ambient conditions are less than 40°F at 4500 psig external pressure, access to the plumbing is only via remote operated vehicles (ROV). ROVs are expensive to operate and in short supply. Still, why HIPPS? The answer is many of the newer subsea wells are accessing deeper, higher-pressure reser- voirs, which can only deliver product to nearby existing infrastructure (platforms and pipelines, designed for lower pressure ﬁelds) to remain an economical venture. A HIPPS system located downstream of a sub- sea well provides a barrier (called a “spec break”) between the high-pressure oil/gas reservoirs and the lower pressure infrastructure. 12 12 INTECH APRIL 2009 INTECH MONTH 2009 WWW.ISA.ORG WWW.ISA.ORG cover story In this case, HIPPS is the only means that several concerns with FaSt Forward would allow tying into the lower rated systems. the North Sea designed l Many of the newer subsea wells are access- The costs for a separate high-pressure infra- systems serving in the ing deeper, higher-pressure reservoirs. structure could very quickly result in costs that U.S. jurisdictional wa- l The likelihood of a HIPPS failure is minimal not only make the development uneconomical, ters without additional by its very design. but also would result in expending more energy redundant design safe- l At 10,000 feet, regular testing and operation than would be gathered from the wells. guards being included. has to be a built-in part of the system. Along the same lines, there are many reser- Recognizing this di- voirs, which industry has overlooked in the past rective of redundancy to offset a lack of regional because they either would not ﬂow or not ﬂow operating experience, and wanting to establish at an economical rate. a uniform set of rules and requirements for Sub- In today’s climate, these wells are receiving sea HIPPS, industry has formed the API 17O more attention, and prospectors are consider- committee, with participation from the MMS, ing options like subsea pumps in order to ob- to produce a new recommended practice. tain that higher and economically viable ﬂow A concern of the MMS is that for mandated rate. Subsea pumps come with their own set of safety devices (down-hole safety valves, Christ- challenges, one of which includes a potential to mas tree master valves, platform-boarding over pressure the downstream ﬂow line. HIPPS valves, and the like) frequent testing is required is one option to mitigate this problem. to conﬁrm their efﬁcacy. Another reason for using HIPPS is as water Leak testing of valves, which authorities there depths increase, it is becoming harder and hard- have waved in some North Sea applications, er to lay high pressure piping systems. The very would not be acceptable to the MMS because of weight of the high-p
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