2002-2003 OTRC PROJECT: INVESTIGATION OF FACTORS AFFECTING ULTIMATE RECOVERY FROM SUBSEA WELLS
OBJECTIVE:
An assessment study is being finalized which considers the special challenges of subsea production. This assessment has identified several technical and operational gaps associated with subsea production and well systems. One of the most striking findings is the low ultimate recoveries anticipated from many subsea wells. The same long, multiphase flowlines that enable development of these resources act to reduce ultimate recoveries. This study proposes an examination of the factors affecting recovery in subsea wells. The study will also consider what role subsea processing and/or multiphase pumping can play in improve ultimate recoveries.
Subsea completed wells are a technology which enable development of both deepwater resources and marginal fields in normal water depths. Subsea technology allows oil and gas discoveries to be turned into “booked reserves.” However, wells developed without some form of subsea processing are expected to experience poor ultimate recoveries due to the high backpressures imposed on the subsea-completed well. For example, conventional production operations routinely drawdown wellhead pressures to 100-200 psig. A subsea completed well, however, may have abandonment wellhead pressures of 1,000-2,000 psig due to the backpressure added by the long multiphase flowline. In addition, these wells operate with a continual high backpressure. For gas wells, this has been shown to have a direct impact on production decline behavior, acting to reduce ultimate recovery. Maintaining a high backpressure can be viewed as a production practice that wastes reservoir energy. Energy that could be used to move reservoir fluids to the wellbore and out of the well is instead lost to flow through a choke or a long flowline. It is anticipated that some form of subsea processing of produced fluids will be necessary to improve efficiencies, allowing longer-term production from these wells and better recovery of this natural resource. Subsea processing can take several forms. These include a myriad of subsea separation and boosting scenarios. This project will compare and contrast subsea separation and pumping with seafloor multiphase pumping and wellbore based artificial lift. The project will also consider the use of new concepts such as floating support structures that can provide an effective alternative to long power cables and chemical treating and control umbilical.
The Petroleum Engineering Department at Texas A&M University is well positioned to perform the proposed study. The PI leads projects on both multiphase pumping and compact separation and processing. The Multiphase Team at Texas A&M has direct experience with operating the equipment proposed for subsea application. The Team operates a large-scale experimental facility that features both a full-size multiphase pump and a high-pressure compact separator. The team is also well trained in modeling the many various development strategies being commonly considering in industry and use of commercial multiphase simulator software.
APPROACH:
This project will utilize classical reservoir engineering techniques combined with numerical multiphase simulation to investigate the factors influencing ultimate recovery. The project will develop new analytical techniques that tie together reservoir performance with backpressure. In addition the project will utilize state-of-the-art multiphase models such as PIPESIM and OLGA to predict multiphase flow behavior in various subsea development strategies. The project will involve direct meetings with oil & gas producers and engineering contractors to insure the most current subsea production systems are investigated. The project will involve several Texas A&M Undergraduate Students and a few select Graduate Students to perform this investigation. The goal is to provide decision makers with the information necessary to assess the conservation impact associated with various subsea production strategies; strategies that may or may not consider subsea processing or subsea multiphase pumping.
DEPLOYMENT OF RESULTS:
This project will provide decision makers and producers with vital information regarding the reserves impact of various subsea development strategies. This is expected to improve the long-term efficiency of subsea production systems by increasing awareness of the effects of various development strategies on ultimate recovery. Workshops and technical papers will be utilized to transfer the findings of this study to industry and raise overall awareness.
ANTICIPATED PROJECT DURATION: 1 year
PROJECT PLAN FOR YEAR 1 (2002-2003):
Scope of Work:
Literature Review – A thorough review will be undertaken of published literature on the effect of backpressure on ultimate recovery and reservoir production decline characteristics. The literature review performed in the ongoing assessment of subsea production systems will be expanded an necessary.
- Direct Meeting with Producers and Subsea Engineering Contractors – After the review of literature, direct meetings will be held with engineering contractors and producers to provide input on the subsea production systems to be investigated.
- Reservoir Modeling – Classical reservoir engineering techniques will be utilized to provided a firm understanding of how high backpressure acts to effect ultimate recovery from a reservoir. The techniques pioneered by Fetkovich for single-phase gas and oil wells will be extended to multiphase flow through use of the Muskat and/or other material balance relationships. The proposed models will be verified with field data as available.
- Modeling Subsea Production Systems – Commercial simulators such at PIPESIM and OLGA will be utilized to investigate the backpressure generated by various subsea development strategies. In addition analytical multiphase models will be considered where appropriate to improve understanding of the basic mechanisms. The modeling will compare and contrast: 1) multiphase pumping; 2) subsea separation and single-phase pumping; and, 3) use of conventional wellbore installed artificial lift methods.
Anticipated Results: This project will extend over a 12-month period. The final result of this project will be a report documenting the findings and a workshop where these findings will be presented to the public. Technical papers are also anticipated.
PRINCIPAL INVESTIGATOR (S): Dr. Stuart L. Scott
2001-2002 OTRC PROJECT: ASSESSMENT OF SUBSEA PRODUCTION & WELL SYSTEMS
OBJECTIVE:
The rapidly accelerating shift to subsea production represents a significant departure from conventional production operations. These increasingly complex subsea production and well systems present a number of technical challenges. A project is proposed to assess the technical, operations and safety issues associated with subsea production and subsea well systems. The needs assessment will involve discussions with regulators, operators, construction/engineering contractors and equipment manufacturers. In addition, a subsea production workshop will be conducted to gain input in an open forum format. Once the needs and technical gaps have been assessed, research will be undertaken on one or more of the highest priority areas.
The subsea environment is perhaps the most remote and unexplored on earth. The remoteness of subsea wells, coupled with a number of complex interactions between subsea wells/flowlines and the ocean environment make monitoring and intervention much more difficult. Historically, subsea production and subsea well systems have had a good track record. However, these systems are now being deployed in ways rarely encountered in previous development schemes. One of the forces driving increased use of subsea production systems is the dramatic reduction in development costs when compared with conventional methods. In some cases this allows development of smaller field, once thought to be uneconomical. Subsea production is also an enabling technology. Its use enables access to remote deepwater locations, turning oil and gas discoveries into “booked reserves.” However, a number of technical issues are associated with subsea production. These include poor recoveries due to the high backpressures imposed on subsea-completed wells and difficulties in monitoring and intervention. In addition, there is growing interest in processing the produced fluids subsea, to achieve even greater efficiencies. This is especially important for ultra-deepwater developments where the cost and size of deploying a floating production system becomes prohibitive and a breakthrough in reducing deck loads is needed. Many in industry view subsea processing as the means of obtaining this necessary breakthrough. Strategic technologies that are believed to be essential for the successful implementation of subsea production include multiphase pumping and metering. Subsea production systems require the transportation of a multiphase mixture of oil, water and gas for many miles from the producing well to a distant processing facility. Industry and regulators are increasingly becoming aware that, while reducing up-front capital outlays, long, multiphase flowlines add additional backpressure, reducing flow rates and ultimate recoveries. For example, conventional production operations routinely drawdown wellhead pressures to 100-200 psig. A subsea completed well, however, may have abandonment wellhead pressures of 1,000-2,000 psig due to the backpressure added by the long multiphase flowline. One of the challenges posed by subsea production is how to reduce wellhead pressure to allow effective recovery of hydrocarbon resources. Multiphase pumping is one technology being considered to help remedy this situation, as well as pressure boosting deployed in advanced subsea well systems. Improved reservoir management is expected to play a critical role in improving recoveries from subsea wells. Multiphase metering holds the potential to provide continuously available oil, gas and water flow rates and is expected to present new opportunities in reservoir management and optimization. This study will assess the progress in developing these and other vital technologies as well as identify the high priority research needs. (We note that flow assurance in long multiphase flowlines can also be a technical challenge for subsea production systems. However, flow assurance topics are not being addressed in this study since there are a number of other active research efforts being conducted elsewhere.)
APPROACH:
This project will utilize surveys, direct meetings, literature reviews and workshops to assess the current state-of-the-art in subsea production and well systems. The project will involve several Texas A&M Undergraduate Students and a few select M.S. Graduate Students to perform this assessment. The research team will then tackle one or more of the higher priority needs to complete the proposed study. The goal is to provide decision makers with the information necessary to assess the technical, operational and safety issues associate with subsea production systems.
DEPLOYMENT OF RESULTS:
This project will assist industry with safe and effective implementation of subsea production systems. The successful implementation of new technology is crucial in order for producers to realize the full potential from deepwater and other subsea development. Workshops and technical papers will be utilized to transfer the findings of this study to industry. By utilizing a substantial undergraduate component to this research, the project will provide the added benefit of transferring this technology into industry as members of the research team graduate and take jobs in industry.
ANTICIPATED PROJECT DURATION: 1 year
PROJECT PLAN FOR YEAR 1 (2001-2002):
Scope of Work:
Assessment
- Literature Reviews – The first step of this project will be a review of published literature on subsea production and well systems. This will include well-known sources such as the SPE literature, OTC papers and other industry publications. In addition, an extensive Internet search will be conducted.
- Surveys and Direct Meeting with Regulators, Suppliers and Producers – After the review of literature, a survey will be conducted with equipment suppliers, engineering contractors and producers to evaluate the state of subsea production technology and identify any gaps. A web-site will also be created to solicit input. Direct meetings will be held with selected regulators and industry representatives to further assess the state of the technology and prioritize the research needs.
- Workshop – An open forum workshop will be held to foster discussion on subsea production. This workshop will utilize speakers and panels to stimulate interaction with the workshop participants. The goal of the meeting will be to rank the research needs and identify technical gaps for subsea production. The P.I. has conducted a number of these interactive workshops, including the Texas A&M Multiphase Pump User Roundtable (MPUR), held in 1999, 2000 and 2001, and the Multiphase Measurement & Production Testing Roundtable, held in 2000.
Research-While the priority of the various research areas will not be established until the assessment is concluded, listed below are some of the topics from which a research area may be defined:
- Subsea Processing – The ability to off-load fluid processing to the seafloor has a number of benefits. These include reduction in platform/FPSO deck load requirements, elimination of backpressure imposed by the production riser, etc. Critical issues associate with subsea production include: multiphase pumping, compact separation, multiphase metering. These technologies are all in varying stages of maturity.
- Flow Assurance – The buildup of wax, scale, hydrate etc. in subsea flowlines, wellheads and risers is a special problem for subsea production where temperatures are quite low. While much work has been done to develop design tools, little has been done in the area of monitoring subsea production systems to detect and locate these materials for remedial action. As more subsea systems are placed in operation, the monitoring and operation needs (rather than the design needs) may emerge as a high priority area.
- Well Intervention – The cost of intervention in subsea wells in extremely high and has limited efforts to monitor wells and install artificial lift. Also, timeliness can be an issue when severe operations problems develop. Development of novel, low cost methods may be a priority.
- Long-Term Well Monitoring – The ability to monitor the long term condition of a well is a special concern for subsea wells. The GOM has experienced a widespread occurrence of sustained casing pressure in producing wells. Methods to monitor and remediate this problem in subsea wells may be an area of high interest.
Anticipated Results: This project will extend over a 12-month period. The final result of this project will be a report documenting the findings and a workshop where these findings will be presented to the public. Depending on the high priority research project undertaken as a results of the assessment, experimental and modeling results will also likely be available and presented in technical papers. Milestones for the project are listed below:
Sponsorship: MMS
PRINCIPAL INVESTIGATOR (S) & OTHERS INVOLVED IN PROJECT:
PI(s): Dr. Stuart L. Scott, Associate Professor of Petroleum Eng., Texas A&M U.
DATE: June 2003
PROJECT NAME: Assessment of Subsea Production & Well Systems (Year 2)
PROJECT NUMBER: 32558-5888Q Task Order: 18206
PRINCIPAL INVESTIGATORS: Dr. Stuart L. Scott
ESTIMATED COMPLETION DATE: August 30, 2003
PROJECT DESCRIPTION:
The first year of this study was spent assessing the technical, operations and safety issues associated with subsea production and subsea well systems. The needs assessment involved discussions with regulators, operators, construction/engineering contractors and equipment manufacturers. The focus has been on the topics of: 1) Subsea Processing; 2) Flow Assurance; 3) Well Intervention; 4) Long-Term Well Monitoring; and, 5) Safety & Environmental Concerns.Reservoir engineering techniques combined with numerical multiphase simulation was utilized to investigate factors influencing ultimate recovery. State-of-the-art multiphase models such as PIPESIM and OLGA along with numerical reservoir simulation software like ECLIPSE were used to predict multiphase flow behavior with various deepwater production strategies.
Right now, the focus is on developing analytical techniques to investigate the effects of backpressure on reservoir energy. Reservoir energy is being utilized to move fluids through long flowlines thus reducing the availability of energy to recover more fluids from the reservoir. These analytical methods will demonstrate the disadvantages of setting up subsea facilities without some form of subsea processing. Subsea processing is shown to be beneficial to the recovery of more hydrocarbons from the subsea reservoir, thus aiding in project economics and adequate utilization of non-renewable resources.
Progress:
Literature Review: The literature review has concentrated on the challenges faced by operators when operating deepwater fields in the offshore Gulf of Mexico region. It is anticipated that many of the fields being exploited by subsea production systems will be abandoned with high wellhead pressures (1,800-3,000 psi) due to the backpressure created by long pipelines. This, in addition to the fact that production rates are reduced due to the backpressure, is expected to affect ultimate recovery from subsea wells. The literature review concentrates on the reasons for this and also highlights ideas from operators and service companies alike to overcome this problem. The options studied are multiphase pumping, subsea separation and pumping and downhole oil-water separation. Also included in the study is a review of the problems being faced with ultra-deepwater, long distance tie-backs when it comes to multiphase pumping and subsea separation and pumping. In particular, the technology gaps and barriers that have so far made operators reluctant to utilize these techniques to improve production.Numerical Simulation: To demonstrate that techniques like multiphase pumping and subsea processing and pumping can be effective in improving ultimate recoveries, a reservoir model in conjunction with a numerical subsea production facilities model has been developed and is being used to predict improvements in hydrocarbon recovery. The reservoir model has been developed for black oil reservoirs and for condensate reservoirs and both the types of reservoir systems are being studied currently. In the future, this model will be refined and applied to a generic GOM reservoir.
Analytical Modeling: Reservoir energy is constantly being utilized to move fluids through long flowlines and deepwater risers to the surface facility. If this energy was, instead made use of to recover more fluids from the reservoir, the ultimate recoveries are seen to be better. An analytical model to investigate just how much reservoir energy is being wasted to move fluids through long flowlines and risers is being developed. This would demonstrate the effectiveness of utilizing some means of subsea processing to aid in decreasing the wastage of reservoir energy.
Industry Interaction: During the past few months, research team members have met with operators & subsea equipment vendors at the following meeting:
Galveston Subsea Tieback Forum Mar. 18-19Recent Publications:
Devegowda D. and S.L. Scott: "An Assessment of Subsea Well and Production Systems," SPE paper 84045 accepted for presentation at the 2003 SPE Annual Technical Meeting & Exhibition, Denver, Colorado, Oct. 3-6.
OTRC PROJECT STATUS REPORTDATE: 15th November, 2002
PROJECT NAME: Assessment of Subsea Production & Well Systems (Year 2)
PROJECT NUMBER: 32558-5888Q-PE Task Order: 18206
PRINCIPAL INVESTIGATORS: Dr. Stuart L. Scott
ESTIMATED COMPLETION DATE: 30th August, 2003
PROJECT DESCRIPTION:
The first year of this study was spent assessing the technical, operations and safety issues associated with subsea production and subsea well systems. The needs assessment involved discussions with regulators, operators, construction/engineering contractors and equipment manufacturers. The focus has been on the topics of: 1) Subsea Processing; 2) Flow Assurance; 3) Well Intervention; 4) Long-Term Well Monitoring; and, 5) Safety & Environmental Concerns.This assessment has identified several technical and operational gaps associated with subsea production and well systems. One of the most striking findings is the low ultimate recoveries anticipated from many subsea wells. The same long, multiphase flowlines which enable development of these resources act to reduce ultimate recoveries. The second year of this study will examine the factors affecting recovery in subsea wells. In particular, the study will also consider what role subsea processing and/or multiphase pumping can play in improve ultimate recoveries.
This second year of this project will utilize classical reservoir engineering techniques combined with numerical multiphase simulation to investigate the factors influencing ultimate recovery. The project will develop new analytical techniques which tie together reservoir performance with backpressure. In addition the project will utilize state-of-the-art multiphase models such as PIPESIM and OLGA to predict multiphase flow behavior in various subsea development strategies. The project will involve direct meetings with oil & gas producers and engineering contractors to insure the most current subsea production systems are investigated. The goal is to provide decision makers with the information necessary to assess the conservation impact associated with various subsea production strategies; strategies that may or may not consider subsea processing or subsea multiphase pumping.
Progress:
Literature Review: The literature review has concentrated on the challenges faced by operators when operating deepwater fields in the offshore Gulf of Mexico region. It is anticipated that many of the fields being exploited by subsea production systems will be abandoned with high wellhead pressures (1,800-3,000 psi) due to the backpressure created by long pipelines. This, in addition to the fact that production rates are reduced due to the backpressure, is expected to affect ultimate recovery from subsea wells. The literature review concentrates on the reasons for this and also highlights ideas from operators and service companies alike to overcome this problem. The options studied are multiphase pumping, subsea separation and pumping and downhole oil-water separation. Also included in the study is a review of the problems being faced with ultra-deepwater, long distance tie-backs when it comes to multiphase pumping and subsea separation and pumping. In particular, the technology gaps and barriers that have so far made operators reluctant to utilize these techniques to improve production.Modeling: To demonstrate that techniques like multiphase pumping and subsea processing and pumping can be effective in improving ultimate recoveries, a reservoir model in conjunction with a numerical subsea production facilities model has been developed and is being used to predict improvements in hydrocarbon recovery. The reservoir model has been developed for black oil reservoirs and for condensate reservoirs and both the types of reservoir systems are being studied currently. In the future, this model will be refined and applied to a generic GOM reservoir.
Industry Interaction: During the past few months, research team members have met with operators & subsea equipment vendors at the following meetings/events:
Houston Technip-Coflexip July 25
College Station Subsea & Arctic Leak Detection Symposium Sept. 9-10
College Station BP (Thunderhorse Development) Sept. 19
San Antonio SPE Annual Tech. Conference & Exhibition Sept. 30-Oct. 1
Recent Publications:
Martin, A.M. and S.L. Scott: "Modeling Reservoir/Tubing/Pump Interaction Identifies Best Candidates for Multiphase Pumping," SPE paper 77500 presented at the SPE Annual Technical Meeting & Exhibition, San Antonio (Sept. 29 - Oct. 2, 2002).
Shippen, M.E. and S.L. Scott: "Multiphase Pumping as an Alternative to Conventional Separation, Pumping and Compression," paper presented at the PSIG Conference, Portland (Oct. 2002).
Date: June, 2002
Project Name: Assessment of Subsea Production & Well Systems
Task Order: 18206 Project Number: 5888Q
Principal Investigators: Dr. Stuart L. Scott
Estimated Completion Date: 30th August, 2002
Project Description:
The subsea environment is perhaps the most remote and unexplored on earth. A dramatic reduction in development costs has provided the impetus to use subsea production systems, enabling access to remote deepwater locations, thereby turning oil and gas discoveries into booked reserves.The remoteness of these subsea wells, coupled with a number of complex interactions between subsea wells, flowlines and the ocean environment make monitoring and intervention much more difficult. Also a shift to subsea production represents a significant departure from conventional production operations, and therefore presents a number of technical challenges.
This study will assess the technical, operations and safety issues associated with subsea production and subsea well systems. The needs assessment will involve discussions with regulators, operators, construction/engineering contractors and equipment manufacturers. To assess the state-of-the-art in subsea technology, our focus has been on the following topics:
i. Subsea Processing
ii. Flow Assurance
iii. Well Intervention
iv. Long-Term Well Monitoring
v. Safety and Environmental ConcernsProgress:
Literature Review: To date, we have collected information from exhaustive web searches from sources like SPE literature and other electronic databases. Other sources for information were OTC papers and company brochures. This information covers the latest technologies and practices currently available in the area of subsea production. Technology assessments have been completed in the areas of subsea multiphase metering and pumping as well as subsea pipelines & umbilical. Current efforts have focused on safety systems for subsea production, well intervention and flow assurance/thermal management.Modeling: Classical reservoir engineering methods have been applied to understand the relationship between well drawdown and ultimate recovery. Results indicate that wells produced with low backpressure tend to recover higher percentages of the hydrocarbons in-place. Application of a global energy balance in being investigated as a method to visualize/explain this effect.
Site-Visits: The following site-visits have been conducted during the last few months to meet with operators and subsea equipment vendors:
Houston OTC 7th May
Houston Baker Hughes 26th JuneAdditional meetings with ABB, Halliburton, Intec and other equipment suppliers are planned for this summer. Meetings with producers are also being arranged.
Workshop: Due to the abundance of deepwater and subsea workshops, we have attended these events rather than trying to hold yet another workshop.Upcoming Publications:
Martin, A.M. and S.L. Scott: "Modeling Reservoir/Tubing/Pump Interaction Identifies Best Candidates for Multiphase Pumping," SPE paper 77500 accepted for presentation at the SPE Annual Technical Meeting & Exhibition, San Antonio (Sept. 29 - Oct. 2, 2002).
Shippen, M.E. and S.L. Scott: "Multiphase Pumping as an Alternative to Conventional Separation, Pumping and Compression," paper accepted for presentation at the PSIG Conference, Portland (Oct. 2002).
Date: February 13, 2002
Project Name: Assessment Of Subsea Production & Well Systems
Task Order: 18206 Project Number: 5888Q
Principal Investigators: Dr. Stuart L. Scott
Estimated Completion Date: September 2002
Project Description:
The subsea environment is perhaps the most remote and unexplored on earth. A dramatic reduction in development costs has provided the impetus to use subsea production systems, enabling access to remote deepwater locations, thereby turning oil and gas discoveries into booked reserves.The remoteness of these subsea wells, coupled with a number of complex interactions between subsea wells, flowlines and the ocean environment make monitoring and intervention much more difficult. Also a shift to subsea production represents a significant departure from conventional production operations, and therefore presents a number of technical challenges.
This study will assess the technical, operations and safety issues associated with subsea production and subsea well systems. The needs assessment will involve discussions with regulators, operators, construction/engineering contractors and equipment manufacturers. In addition, a subsea production workshop will be conducted to gain input in an open forum format. Once the needs and technical gaps have been assessed, research will be undertaken on one or more of the highest priority areas.
Progress:In order to assess the state-of-the-art in subsea technology, our principal focus is governed by:
i. Subsea Processing
ii. Flow Assurance
iii. Well Intervention
iv. Long-Term Well Monitoring
v. Safety and Environmental ConcernsLiterature Review: An extensive review of published literature from the Offshore Technology Conference (1996-2001), and from the SPE (1991-2001) has been carried out. This is to supplement the database already assembled by Dr. Scott in his role as editor for an SPE Reprint on Offshore Multiphase Production. Other published articles, vendor and equipment information, and reviews of present day technology were searched through various electronic databases. A list of subsea equipment vendors is being prepared to receive a survey mailing regarding the goals of this project. Vendors in the area of subsea pumping have already been contacted. Individual members of the team have been assigned specific focus areas such as subsea pump, multiphase metering and compact separation.
Modeling: Work is underway to understand the relationship between well draw down and depletion. This work is expected to show what role subsea processing and subsea multiphase pump can play in improving ultimate recoveries from subsea wells.
Site-Visits: The following site-visits have been conducted to meet with operators and subsea equipment vendors:Houston Speaker–SPE Luncheon on Subsea Processing 27th November
Houston Copper/Cameron 24th January
Norway Kvaerner 29th January
Germany Bornemann Pumps 30th January
Houston Panel Member – SPE Workshop on Subsea Processing 7th February
Additional meetings with other equipment suppliers, regulators, producers, and engineering contractors are scheduled for this Spring.Workshop: A workshop is planned to foster discussion on the key issues regarding subsea production and well systems. Over the next few weeks, the focus of the meeting will be better defined, with topics such as monitoring subsea wells for sustained casing pressure, subsea separation systems, multiphase metering, environmental impact of subsea processing being considered.
