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Downhole Water Sink Technology

The Louisiana State University Craft & Hawkins Department of Petroleum Engineering is soliciting participants for a cooperative affiliation, Downhole Water Sink (DWS) Technology Initiative. The DWS Initiative is dedicated to the emerging completion/production technology employing a downhole water sink installation. The technology uses a hydrodynamic concept of downhole water drainage in-situ to control and abate excessive volumes of formation brine produced by oil and gas wells. The development of this technology has been already advanced to the point that some DWS completions and production schemes can be designed and implemented in field operations while other aspects need further research and development efforts.

Mission of DWS Initiative

The overall goal of the initiative is to advance theoretical principles of the DWS technology, implement the technology in field operations by the industrial members of the DWS Initiative, and provide technical support for the implementation.

Participation in DWS Initiative

Participation in DWS Initiative is open to the oil and gas operators and service companies involved in implementation of the DWS technology (Industrial Contributor), as well as sponsoring agencies or other research organizations interested in getting data from the DWS Initiative projects (Other Contributor). The financial and legal terms of participation are defined in the attached document titled, Cooperative Agreement for DWS Initiative.
 

Procedure

The DWS Initiative develops DWS technology through field implementations of the technology by the Industrial Contributors, on one hand, and concurrent research and technical support provided by the LSU team, on the other hand. We believe that this approach is the most effective and fastest way to make the technology work in various conditions and for different petroleum operators. Also, the approach gives all participants the benefit of having access to the broader data base of various DWS field trials and results of analytical/experimental work performed at LSU for these trials.

There is a continuous interaction between each Industrial Contributor and the LSU team during implementation of a specific DWS field project by this participant, from well planning to completion design to production schedule. LSU provides conventional theoretical analysis of the design and operational variables necessary for advancing the project. In case the project requires unconventional approach the LSU team performs a short-term research study for the Industrial Contributor to solve the problem.

In addition to providing technical support for individual Industrial Contributors the LSU team conducts research projects on new aspects of the DWS technology that are of interest to all members of DWSTI. A list of such projects is included in the section, "Other Suggested Annual Projects" of this document. The LSU team reports on progress in these projects at the semiannual meetings of the initiative participant representatives, DWS Initiative Advisory Panel (IAP).

DWS Technology Brief

Downhole water sink is a new technique for producing water-free hydrocarbons from reservoirs with bottom water drive and strong tendency to water coning. Conventional wells in these reservoirs produce increasing volumes of brine with decreasing amounts of oil or gas which ultimately leads to early shut downs of these wells without sufficient recovery of hydrocarbons in place. Furthermore, the produced waters are contaminated with hydrocarbons and require costly treatment prior to offshore discharges or subsurface injections.

DWS technology eliminates water cutting the hydrocarbon production by employing hydrodynamic mechanism of coning control in-situ at the oil-water or gas-water contact. The mechanism is based upon a localized drainage generated by a controlled downhole water sink installed in the aquifer beneath the oil or gas-water contact.

Figure 1 depicts the principles of two basic variants of the DWS systems, drainage-injection (variant A) and drainage-production (variant B). In the system a well is dually completed in the oil and water zones and the two completions are separated by a packer set inside the well at depth of the oil- water contact. The water zone completion includes a submersible pump and water drainage perforations. The submersible pump drains the formation water around the well and prevents water coning from breaking through the oil column into oil-producing perforations. Since the produced stream of oil is water-free flow performance of the well can be fully utilized to maximize oil production.

Fate and quality of the drained formation water depend upon configuration of the DWS system. In the drainage-injection systems (Variant A) the drained water, free from oil contamination, is either re-injected downhole into the same aquifer (downhole water loop) or into a deep injection zone (split drainage-injection).

The DWS drainage-production systems (Variant B) can be operated in the "clean water" range such that the drained water is free of oil and readily discharged overboard. The systems can also be designed for maximum oil production (intensive production) with the upper completion producing water-free oil and the water sink completion producing water with some oil cut. In the latter case the design involves inversing the water cone to create oil breakthrough into the water sink.

DWS Technology Development to Date

DWS technology has been theoretically developed at the LSU Department of Petroleum Engineering since 1991. Also, a DWS drainage-production system successfully field tested by Hunt Petroleum Corporation in 1994 and has been in operation ever since. Recently, LSU and Hunt Petroleum were jointly awarded a 1996 Special Meritorious Award for Engineering Innovation by the Petroleum Engineer International. Another DWS well installation has been just completed by Texaco in the Kern River field, California.

The field trial of the DWS water drainage - production system was performed by Hunt Petroleum in a Wilcox sand of the Nebo-Hemphill field in LaSalle Parish, Louisiana, a formation known for high water-cut production. Most of the sands in this formation have very strong natural water drives and are clean, with 1-4 darcy permeability and high vertical-to-horizontal permeability ratios. This leads to rapid bottom water coning. A typical well in this field would develop a water problem in 60-90 days after oil production began, and the excessive water cut (97%) would cause production to drop from the initial rate of 35 BOPD to 12 BOPD.

The new well was drilled through the oil and water columns and dual-completed in both zones. The water-drainage completion is gravel packed and isolated from the oil completion with a packer and 3 1/2-in. tubing. A downhole progressive cavity pump lifts the water to the tubing, while the formation pressure drives the water-free oil up the annulus between the tubing and 7-in. casing. After two years of production, the well is averaging 55 BOPD (higher than the initial rate) with only 0.2 percent water cut. The produced water is pumped directly to the salt water disposal system with no additional treatment.

The Nebo-Hemphill field test showed that the DWS technology was able to: 1- prevent water breakthrough ;and, 2- reverse development of water coning after the breakthrough occurred. In the first application the oil and grease (O&G) concentration in the produced brine was below the detection level of the EPA - approved test. Thus formation waters produced with this new method could qualify for permitted discharges with no treatment. In the second application a developing water cut was reduced from 7 percent to 0.2 percent.

Present Status and Rationale for DWS Initiative

In the past, technical support for DWS technology was offered by the LSU team to the petroleum industry on an individual basis through consulting services or the DOE - sponsored technology transfer program. Several major oil companies and independent operators had used the LSU expertise at various stages of implementation of the DWS technology: from economic feasibility studies, to completion designs, to actual recompletions and production trials.

Our past experience showed that when employing DWS systems operators were challenged with reservoir problems and well conditions so different that each design required additional research. In the result, new DWS techniques were created. However, there was lack of a concerted effort to advance design studies that would be of interest to many operators at the same time. The DWS Initiative was created to provide a financial basis for such studies and enable technology transfer to all industrial members. On September 10, 1997, at the DWSIT Kick-Off meeting at LSU the DWSIT concept was discussed with petroleum industry. It was concluded that the DWS Initiative would well serve member companies and fulfill the industry research needs and our academic objectives at LSU.

Presently (February, 1998), DWSTI has nine industrial members (Shell, Mobil, Chevron, PanCandian, Texaco, Baker Hughes, Sonat, Unocal, and Pennzoil). The 1998 annual project, Principles and Design Method for DWS Well Completions with Segregated Inflows of Oil and Water, is underway with completion date, December, 1998. Also, several industrial members are in the process of designing or completing wells with DWS installations.

DWS Initiative Deliverables

The initiative deliverables will include two types of activities performed by the LSU team: technical support, and research projects. Technical support will involve theoretical computer aided design of DWS systems for a specific reservoir/well conditions provided by the Industrial Contributors. Based on this design the operator will be able to assess DWS project economics and prepare well completion program. Specifically, deliverables here may be one of the following studies:

  1. Estimation of DWS input data from water cut history matching;
  2. Computation of DWS performance windows for a given completion program;
  3. Optimization of completion parameters for maximum DWS performance; and,
  4. Customized studies such as the effects of leaking cement behind casing, vertical permeability barriers, or reinjection to the same aquifer upon DWS system performance

Each Industrial Contributor is entitled to receiving one technical support study per year. The extent of such study will be negotiated between the LSU team and the Contributor. The study will be provided as a written report with all additional data necessary for well completion design and production schemes. Deadlines for these studies will be negotiated between the LSU team and the Industrial Contributor according to the Contributor's activity timetable.

Research projects will be conducted by the LSU team reporting to all Contributors through their voting representatives to the IAP. Semiannual review meetings of the IAP will give DWS membership an opportunity to make comments regarding both the priority of proposed future projects and the direction of research in the pending project. Specific deliverables for the research projects include:

  1. Quarterly written progress briefs;
  2. Semiannual progress reports presented at the initiative member meetings;
  3. Complete annual or final reports.

More specific listing of deliverables will be prepared for each annual project in relation to the project's objectives.

1999 Project

 Tittle:  Principles and Design Method for DWS Well Completions with Commingled Inflows of Oil and Water

Objective:      

To perform a study and develop technical criteria for sustainable maximized oil production using the DWS well systems operating in the commingled inflow mode when water (or oil) breakthrough is allowed and controlled by adjusted production rates.

Tasks:

  1. Develop a mathematical model of commingled inflow of oil and water into the well's water drainage completion (reversed coning);
  2. Write software for computation of the dynamic oil-water interface during reversed coning;
  3. Demonstrate behavior of DWS systems with reversed coning using a physical model;
  4. Determine critical parameters for sustainable and unstable operation of the physical model;
  5. Mathematically model the physical model's behavior;
  6. Develop a computer-aided design procedure for designing inflow performance window for DWS well completions with reversed coning;
  7. Determine feasibility criteria and a method to calculate maximum oil production rate for reversed coning.

  Deliverables:

  1. A summary report providing a basic understanding of the reservoir-well system behavior during DWS operation with reversed coning;
  2. Video tapes and photographs supporting our findings from the physical model studies;
  3. Theoretical recommendations regarding feasibility, technical requirements and limitations of the intensive DWS technology;
  4. Software for calculating inflow performance window and oil production rate limit.

 2000 Project

“DWS Well Selection and Production Optimization Method for Maximum Performance” 

Objective:      

There is a need for systematic approach to implementation of DWS technology in a specific oilfield. Operators should know if DWS is a suitable solution, how to select wells for re-completion, how to operate and evaluate DWS wells. Objective of this project is to perform study and develop technical criteria and analytical tools for deployment and operation of DWS wells to maximize advantage of DWS over conventional technology in reservoirs with water coning problems.

Tasks:

  1. Criteria and Method for DWS Well Selection: Perform sensitivity analysis of reservoir properties and well parameters to identify controlling factors; Formulate screening criteria for selection of the best well candidates for DWS installations; Develop software for computation Performance Parameter representing advantage of DWS over conventional completion; Formulate selection procedure for a reservoir candidates; Formulate selection method for well candidates.
  2.  DWS Well Evaluation Method: Develop a transient pressure testing method and software for evaluation well hydraulic integrity; Modify the pressure transient method to evaluate formation permeability damage;  Formulate a mathematical model of multi-rate testing of DWS wells; Introduce productivity index and wellbore flowing pressure to inflow performance mapping; Solve problem of well stabilization prediction; Develop testing procedure and analysis method for DWS well productivity testing; Demonstrate the method with simulated examples.
  3. DWS Well Production Optimization Schedules: Introduce well performance limits to Inflow Performance Chart; Formulate mathematical optimization model for daily performance of DWS well in terms of maximum production/return rates; Formulate mathematical optimization model for timerelated well production schedule and maximum NPV; Write a software for designing the optimized production program for DWS wells to maximize recovery of oil or NPV; Solve example applications.
  4.  Feasibility of Water Control in Horizontal Wells Using DWS Completions: Review the methods for water cresting and pressure drawdown distribution in horizontal wells - literature study; Develop water cresting study tool using commercial numerical simulator; Determine a design method for maximum length of the reach section for horizontal wells with water cresting problems; Modify the simulation tool for modeling horizontal wells with dual completions; Study productivity increase for horizontal wells with tail-pipe water sink; Study productivity increase for bi-lateral horizontal wells with water sink completions.
  5.  Physical Demonstration of DWS Technology: Install data collection/monitoring system on the radial model; Develop procedures for model pre-packing, operating and cleaning; Test the model up-scaling procedure using a homogeneous sand pack; Conduct a video-taped experiment 1: Prediction of DWS Well Performance from Physical Model; Conduct a video-taped experiment 2: Recovery Performance of Wells with Water Coning and permeability Stratification

 Deliverables:

  1. A summary report providing the theory, criteria and method for DWS Well Selection and evaluation.
  2. A summary report providing the theory, experimental results, data from analytical studies and methodologies for well evaluation, testing, and production optimization.
  3. Software for optimized production program for a DWS well;
  4. Data from computer simulation studies and a numerical method for estimation of the feasibility of water control in horizontal wells using DWS completions
  5. Two videotapes and written training materials summarizing the visual demonstration experiments

2001 Project

“Principles and Design Method for DWS Completion of Gas and Horizontal Wells with Water Coning Problems”

Objective:

There is a need for methodology to design DWS well completion for gas reservoirs with water coning and horizontal wells with water cresting problems. These two well-reservoir systems are fundamentally different than vertical oil wells because of the nature and mobility of reservoir fluids (water/gas) or well geometry and inflow performance capacity (horizontal wells).  For gas wells, the objective of this project is formulation of technical criteria for sustainable production of gas with no water breakthrough to the well. For horizontal wells, the study should determine well configurations and completion criteria for horizontal wells with reversed water coning. The well performance relationships resulting from this design should define technical feasibility of using DWS in gas wells and horizontal oil wells. 

 

Tasks:

  1. Feasibility of Water Coning Control in Gas Wells through Completion Modifications: Describe specific mechanism of water coning in gas wells; Identify inflow performance procedure for gas wells in presence/absence of bottom water; Develop analytical model of gas well with leaking cement; Analyze the effect of perforations on water flow behind casing; Develop a method for completion design with maximum gas well deliverability.
  2.  Computer-aided Design of Horizontal Well Completion for Water Cresting Control: Formulate model of water cresting in horizontal well with 2-phase flow; Define productivity and inflow performance of horizontal well with water cresting; Build simulation model of horizontal well with tail pipe/bi-lateral completion; Perform parametric study of DWS system in the well; Develop a method for DWS completion design in horizontal well.
  3. Gas Lift Design for DWS Wells: Analyze dual gas lift installations and methods for design; Develop procedure for optimized design of single gas lift in DWS wells; Formulate methodology for designing dual gas lift in DWS wells: define IPC limitations; build mathematical model; perform sensitivity analysis; Demonstrate the method with solved examples.
  4. DWS Well Deliverability with Oil-free Water Drainage: Perform literature studies of capillary pressure zone data and procedures for oil and gas reservoir systems; Develop a method for inclusion capillary pressure effects in DWS well deliverability prediction; Formulate procedure for designing DWS wells with no oil in drainage water.
  5. Physical Demonstration of Water Coning Control in Oil and gas Wells: Fabricate a physical model; Formulate theory and improve the up-scaling procedures for pie-shape sand packs with DWS installations; Perform video-taped experiments on oil-water and gas-water systems; Verify the experiments with numerical simulator; Edit visual records from the experiments.

 Deliverables:

  1. A summary report describing analytical and numerical comparison of gas wells with bottom water drive to DWS gas wells.
  2. A report and Eclipse simulator data deck used to model and study horizontal wells and horizontal DWS wells together with an analysis of the study results.
  3. A procedure and solved example of designing optimized dual gas lift for maximum oil production in DWS wells;
  4. A summary report describing the use of numerical reservoir simulator (Eclipse) to determine operational parameters of DWS well producing
  5. A report and video-CD with video-taped results of physical-simulation experiments showing effect of stratification permeability barriers on water coning and its control with DWS completions.

2002 Project

“Principles and Design Method for Integration of Dual Completion Design with Reservoir and Well Performance” 

 

Objective:            With fast developing technologies of downhole O/W and G/W separation and chemical water shut-off there is a need to qualify the reservoir engineering advantage of DWS. DWS technology inter-relates the reservoir and the well. To date, theoretical development of DWS technology focused on designing dual completion-production configuration for a simplified model of the well reservoir system: strong water drive, complete well integrity, three-dimensional coning and unlimited well lifting performance. It is necessary, however to qualify the use of DWS technology for specific well-reservoir systems. (For example, designing DWS for an old completely watered-out well is completely different than for a new well in the same reservoir). The project will address design aspects of DWS for a few typical well reservoir systems: gas wells with water problem and pressure depletion, and watered-out oil wells with significant bypassed oil reserves. Also, we intend to develop analytical tools, models and methods for predicting DWS performance in these systems.

 

Tasks:

  1. Alternative design of DWS for gas wells with downhole separation capability. The task is a continuation of Task 1 of the 2001 Project regarding water coning in gas wells. It will compare critically the advantage of DWS (reservoir control) with DGWS (in-well separation). Also, effectiveness of DWS to control water mechanisms unique for gas wells will be evaluated. We will develop a method for identifying these mechanisms. Also, we will formulate conditions for DWS operation to maximize pressure depletion rate while keeping the well above the water-loading threshold. Compare critically the advantage of DWS (reservoir control) with DGWS (in-well separation); Develop a method for identifying water mechanisms unique for gas wells, such as N-Darcy, perforations, skin, leaking cement; Evaluate performance of DWS to control these mechanisms and a method for screening well/reservoir candidates; Define best conditions for DWS operation for maximum rate w/o water loading.
  2. Valuation of inactive wells in water drive reservoirs. Present methods for valuation of inactive wells are based on oversimplifying assumptions of stripper productivity and advantageous oil prices. Correct valuation should be based on incremental recovery with a new technology. DWS is such a technology. This is a feasibility study into using DWS design theory and field data from matured oil reservoirs with abandoned wells to determine incremental recoverable reserves with DWS. Analyze current valuation methods (stripper  rate or oil price forecasting); Develop procedure for incremental well productivity with DWS; Examine time-related water drainage process to open DWS well to production; Adopt a commercial simulator tool to modeling the drainage-recovery process; Create a procedure for computing net present value of incremental recovery; Collect reservoir data and demonstrate the valuation procedure.
  3. Simulator-assisted tool for advanced analysis of water inflow mechanism at and around petroleum wells. Water inflow to wells is controlled by combination of phenomena occurring locally-around and inside wells. Smart completions (and DWS is one of them) should control the phenomena. Unfortunately, most commercial simulators have not been made to model these effects. Hence, there is a need to build an analytical tool that would couple simple Excel-based interface programs with a commercial simulator. The interface, developed by the LSU team, would model well inflow mechanisms (DWS) not supported by commercial simulator. The simulator would pass two-phase flowrates and pressures to the interface, which would compute the inflow conditions. Then, it would modify the constraints and pass it back to the simulator. We intend to develop this tool incrementally, by adding more programs in time. Also, we will solicit a vendor of numerical simulator to participate in this project through licensing the simulator to the members.  Build an analytical tool that would couple simple Excel-based interface programs with a commercial simulator; Create input module for 2D single-well water control simulations;   Add to the module basic properties plus skin, perforation, non-Darcy skin, rates, and completions; Integrate the module with commercial simulator; Add the report (output) modules presenting basic prediction, sensitivity, and Inflow Performance Domain.

Other Suggested Annual Projects 

 

  • Development of screening criteria for re-activation of inactive wells using DWS installations.
  • Design of DWS completions and production schemes for gas/water and gas/oil/water wells with coning problems. 
  • Pressure transient testing and monitoring of DWS systems performance and external integrity.
  • Prediction of a long-term production decline and  recovery factors for reservoirs produced with the DWS technology.
  • Design of DWS wells for multi-layered reservoirs under conditions of selective water encroachment.
  • System (nodal) analysis method for DWS wells with various types of artificial lift for oil and water production/injection.
  • Feasibility study of an innovative DWS system with dual completion in the oil column.
  • Study into theoretical basis and development of testing procedures required to justify higher allowables for wells with DWS installations.
  • Design and performance of bilateral completions with DWS installations.
  • Development of analytical mathematical models for calibration of DWS numerical simulators.
  • Dynamic removal of excessive water saturation around oil/gas well completions using DWS technology - experimental and theoretical study.
  • Formulation of a quantitative method for prediction of the DWS field system performance using a bench-top physical model.
  • Feasibility study of using DWS technology for controlled downhole injection of treatment chemicals.
  • Experimental development of a monitoring technique and tools for downhole quality control of brine in DWS systems with continuous injection in-situ.
  • Full-scale experimental study of integrity, reliability and efficiency of  innovative downhole pumping systems for concurrent production/drainage/reinjection of formation fluids.
  • Feasibility, performance, and design of DWS completions in fractured reservboirs with water channeling problem.
  • Water Control in Oil Wells With Downhole Oil-Free Water Drainage and Disposal

Cost of Participation

The amount of annual contribution for a new member is $15,000.  To become a Contributor during the first year of DWS Initiative a new member must sign the Cooperative Agreement for Downhole Water Sink Technology Initiative and pay the annual contribution to LSU.  A  new member will have to pay the full annual contribution for the year in progress disregarding the time of the year . Through such payment, the new member will acquire access to all (published and unpublished) data on research performed and technologies developed in the course of the DWS Initiative. 

A Contributor may make contribution "in kind" by fabricating experimental setup, doing measurements, or hiring out graduate students to work on a current DWS project.  The dollar value of such in-kind contribution cannot exceed $7,500 per year.  This dollar value will be then used to reduce the amount of the annual cash contribution of the Contributor for the following year.

Contributor who joins DWSTI after the first year of operation will pay University a total cash contribution of $15,000 as its share for one- year participation in DWS Initiative and a one-time late-joining fee of  $7,500. The late-joining fee will give Contributor right to acquire past deliverables from DWSTI. 

 

LSU Contact

Dr. Andrew K. Wojtanowicz,  PE
Department of Petroleum Engineering
Louisiana State University
Baton Rouge, Louisiana 70803
Phone: (225) 578-6049;
Fax: (225) 578-6039
E-mail: awojtan@lsu.edu 

DWS Bibliography

  1. Wojtanowicz, A.K., and Shirman, E.I., 2002,"Inflow Performance and Pressure Interference in Dual-Completed Wells with Water Coning Control,” J. Energy Resources Technology-Transactions ASME, Vol. 124, December. “New Concepts of Dual-Completion for Water Cresting Control and Improved Oil Recovery in Horizontal Wells,” S. O. Inikori, and A.K. Wojtanowicz, SPE 77416, SPE Annual Technical Conference and Exhibition, San Antonio, Texas, Sep.29-Oct.2, 2002.
  2.  “Water Control in Oil Wells With Downhole Oil-Free Water Drainage and Disposal,” S. O. Inikori,, A.K. Wojtanowicz, and S.S. Siddiqi, SPE 77559, SPE Annual Technical Conference and Exhibition, San Antonio, Texas, Sep.29-Oct.2, 2002.
  3. “A Study of Water Coning Control in Oil Wells by Injected or Natural Flow Barriers Using Scaled Model and Numerical Simulator,” S.S. Siddiqi, and A.K. Wojtanowicz, SPE 77415, SPE Annual Technical Conference and Exhibition, San Antonio, Texas, Sep.29-Oct.2, 2002.
  4. “Dual Gas Lift in Wells with Downhole Water Sink Completion,” L. Marcano, and A.K. Wojtanowicz, Petroleumj Society’s Canadian International Petroleum Conference 2002, Calgary, Alberta, Canada, June 11-13, 2002.
  5. “Severity of Water Coning in Gas Wells,” M. Armenta, and A.K. Wojtanowicz, SPE 75720, SPE Gas Technology Symposium, Calgary, Alberta, Canada, Apr.30-May 2, 2002.
  6. “Prediction of Capillary Fluid Interfaces During Gas or Water Coning in Vertical Wells,” R.T. Johns, L.W. Lake, and A.M. Delliste, SPE 77772, SPE Annual Technical Conference and Exhibition, San Antonio, Texas, Sep.29-Oct.2, 2002.
  7. “Analytical Solution for Free-Hydrocarbon Recovery Using Skimmer and Dual-Pump Wells,” A.B. Obigbesan, R.T. Johns, L.W. Lake, L. Bermudez, M.R. Hassan, and R.J. Charbeneau, SPE 66756, SPE 66536, SPE/EPA/DOE E&P Environmental Conference, San Antonio, TX, Feb. 26-28, 2001.
  8. “Contaminated Water Production in Old Oilfields with Downhole Water Separation: Effects of Capillary Pressure and Relative Permeability Histeresis,” S.O. Inikori, and A.K. Wojtanowicz, SPE 66536, SPE/EPA/DOE E&P Environmental Conference, San Antonio, TX, Feb. 26-28, 2001.
  9. “Assessment and Inclusion of Capillary Pressure/Relative Permeability Histeresis Effects in Downhole Water Sink (DWS) Well Technology for Water coning Control,” S.O. Inikori, and A.K. Wojtanowicz, ETCE2001-17100, Engineering Technology Conference on Energy, Houston, TX, Feb. 5-7, 2001.
  10. “Vertical Interference Testing Method Using Dual Completions with Downhole Water Sink,” L.R. Ramos, E. Shirman, and A. K. Wojtanowicz, SPE 62921, 2000 Annual Technical Conference and Exhibition of SPE, Dallas, TX, Oct. 1-4, 2000.
  11. “Diagnosis of Excessive Water Production,” L. Ramos, A.K. Wojtanowicz, and E. Shirman, 11-th International Scientific and Technical Conference: “New Methods and Technologies in Petroleum Geology, Drilling, and Reservoir Engineering,” Krakow, Poland, June 29-30, 2000, 79-92.
  12. "More Oil Using Downhole Water Sink Technology: A Feasibility Study," A.K. Wojtanowicz, and Ephim I. Shirman, SPE Production and Facilities, 15 (4), November 2000.
  13. "Maximum Deliverability of Dual-Completed Wells with Downhole Water Sink (DWS) - Analytical and Experimental Study," E.I. Shirman, and A.K. Wojtanowicz, ETCE/OMAE 2000 Conference, New Orleans, LA, Feb. 14-17, 2000.
  14. "Controlling Water Production/Coning - A Case History," M.Swisher, and A. K. Wojtanowicz, Proc. ETEC Conference and 69th Annual meeting of IPAA, New Orleans, LA Nov. 11-14, 1998.
  15. "Downhole Water Sink (DWS) Completion Enhance Oil Recovery in Reservoirs with Water Coning Problem," A.K. Wojtanowicz, E.I. Shirman, and H. Kurban, SPE 56721, Proc. 1999 SPE Annual Technical Conference & Exhibition, Houston, TX, Oct. 3-6, 1999, 333-340.
  16. “Coning in Dual Completed Systems,” J. Gunning, L. Paterson, and B. Poliak, J. Petroleum Science & Engineering, Elsevier, 23, 1999, 27-39.
  17. “More Oil with Less Water Using Downhole Water Sink technology: A Feasibility Study,” Shirman E. I., and Wojtanowicz A. K., SPE 49052, Proc. 73rd Annual Technical Conference and Exhibition of SPE, New Orleans, LA, October 27-30, 1998.
  18. “Completion Design for Downhole Water and oil Separation and Invert Coning,” A. Loginov, and C. Shaw, SPE 38829, Proc. 72nd Annual Technical Conference and Exhibition of SPE, San Antonio, Texas, October 5-8, 1997, also, Journal of Petroleum Technology, March 1998, 70 -73.
  19. “In - Situ gravity Segregation Eliminates Bottom Water Coning,” C. K. Chea et al., Proc. 26th Convention of Indonesian Petroleum Association, May, 1998.
  20. “Field Application of In-Situ Gravity Segregation to Remediate Prior Water Coning,” Bowlin K. R., et al. SPE 38296, Proc. 1997 SPE Western Regional Meeting, Long Beach, CA June 25-27, 1997, also, Journal of Petroleum Technology, October 1997, 1117 - 1120.
  21. “Water Coning Reversal Using Downhole Water Sink-Theory and Experimental Study,” Shirman, E.I., and Wojtanowicz, A.K., SPE 38792, Proc. 72nd Annual Technical Conference and Exhibition of SPE, San Antonio, Texas, October 5-8, 1997.
  22. “Water Cone Histeresis and Reversal for Well Completions Using the Moving Spherical Sink Method,” Shirman, E.I., and Wojtanowicz, A.K., SPE 37467, Proc. 1997 Production Operations Symposium, Oklahoma City, Oklahoma, March 9-11, 1997. 611-616.
  23. “Field Application of In-Situ Gravity Segregation to Remediate Prior Water Coning,” Bowlin, K.R., et al., SPE 38296, Proc. 1997 SPE Western Regional Meeting, Long Beach, California, Feb. 25-27, 1997.
  24. “Downhole Oil and Water Separation - Potential of a New Technology,” L. I. Chruseh, IPA 96 - 2.4 - 156, Proc. Indonesian Petroleum Association 25th Silver Anniversary Convention, Jakarta, October 1996.
  25. “A Well Completion Design Model for Water-Free Production from Reservoirs Overlaying Aquifers,” Shirman, E.I., Proc. 1996 SPE Annual Technical Conference and Exhibition, Denver, Colorado, October 6-9, 1996. 853-860.
  26. "Dual Completion Solves Water Coning," The American Oil and Gas Reporter, March, 1997, 126-128.
  27. "In-Situ Segregated Production of Oil and Water - A Production Method with Environmental Merit: Field Application," M. Swisher, and A.K. Wojtanowicz, SPE Advanced Technology Series: Health, Safety, Environment, Vol.4, No.2, August 1996.
  28. Oil and Water don't Mix," Thad Slaton, Bussiness Report, August 6, 1996, 18-20.
  29. "New Completion Design Keeps Water in Its Place," Petroleum Engineer International, June 1996, 42.
  30. "Dual Completion Method Minimizes Bottom Water Coning," Petroleum Engineer International, April 1996, 11.
  31. "Analytical Modeling of Crossflow into Wells in Stratified Reservoirs: Theory and Field Application," Shirman, E.I., and Wojtanowicz, A.K., Proc. 7th Intl. Scientific and Technical Conference, "New Methods and Technologies in Petroleum Geology, Drilling, and Reservoir Engineering," Krakow, Poland, June 20-21, 1996.
  32. "An In-Situ Method for Downhole Drainage-Injection of Formation Brine in a Single Oil-Producing Well," A.K. Wojtanowicz, and E. Shirman, in "Deep Injection Disposal of Hazardous and Industrial Wastes," J.A. Apps, and Chin-Fu Tsnag, editors, Academic Press, 1996, 403-420.
  33. "New Dual Completion Method Eliminates Bottomhole Water Coning," Swisher, M.D., and Wojtanowicz, A.K., SPE paper 30697, Proc. SPE Annual Technical Conference and Exhibition, Dallas, TX, October 22-25, 1995, 549-555.
  34. “Dynamic Water Coning Control Through Dual Completion, Downhole Separation and Reinjection of Water,” J. Kleppe, et al., IATMI 950141, Proc. Society of Indonesian Petroleum Engineers Symposium on Production Optimization, Bandung, Indonesia, July 24-26, 1995.
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