Abstract.A range of effects may make fast ion confinement in spherical tokamaks worse than in conventional aspect ratio tokamaks. Data from neutron detectors, a neutral particle analyzer, and a fast ion loss diagnostic on the National Spherical Torus Experiment (NSTX) indicate that neutral beam ion confinement is consistent with classical expectations in quiescent plasmas, within the ~25% errors of measurement. However, fast ion confinement in NSTX is frequently affected by magnetohydrodynamic (MHD) activity, and the effect of MHD can be quite strong.

No abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractUnwanted water production may adversely affect well economics because of water-disposal costs, environmental issues, and reduced hydrocarbon production. This paper presents examples of how openhole and cased-hole logs can help determine the type and location of water entry, and indicate appropriate conformance treatments. Selected logs run following the treatments are used to evaluate the treatments. The cost of running the logs and applying the indicated conformance treatments is compared with the cost of water disposal and declining petroleum production.Specific examples show that casing leaks, cement channels, coning, and watered-out reservoirs may all be easily identified and located through the use of openhole, production, pulsed neutron, casing inspection, and cement evaluation logs. Not all of these logs need be run in every well; thus, in each well, existing information was thoroughly studied to determine the most cost-effective diagnostic logging program.The diagnostic information provided by the logs was useful in selecting appropriate conformance treatments. Many of the same logs used in diagnosing the water-production problems were found to be valuable in evaluating the effectiveness of the performed treatment. In some cases, follow-up treatments were suggested by the evaluation of the initial treatment and were the difference between successful rejuvenation of hydrocarbon production and continued declining well performance.The costs of the logs used for conformance diagnosis and treatment evaluation were compared to the possible long-term costs of water disposal, environmental considerations, and reduced production from the well and were found to be relatively inexpensive. Using Well Logs for Conformance DesignOpenhole logs offer a wealth of information for reservoir characterization, well planning, and stimulation design, each of which is an integral component of conformance design.

%ciety.of Pe!mleum Engineers and are sublect to correction by the author(s). The matOriaL as presented-dOe$ n~nece$5afilY reflect any position of the Society of Petroleum Er,.ginews, its otflcem, c+ nyambem. Paper% presented at SPE rneeling$ %. sub]ecf to p.blicatlon re~isw by Eddorfal C.mmitlees of the Society of Petroleum Englnews. Perrnissio" m copy is restricted to a" abstract of not more than 300 words. Ilkt$lralions may not be cqvled. The ai%tracf should mntaln conspicuous acknowledgment of where and by whom the paper is presented. Write Llbraria", SPE, P,O. Box 83383S. Rlchardwm, TX 7S083-3836, U..%% Telex, 193M5 SPEUT.

Unwanted water production in oil and gas wells is a limiting factor in the productive life of the well. Many factors are influencing the drive for improved water control loss of hydrocarbon production, environmental impact of disposal, government regulations, and public opinion. The environmental issues and costs related to produced water and it's disposal are becoming major burdens for producers. The economic factor of reducing water production far outweighs the cost of typical water control treatments. Historically, water control treatments have often failed due to one or more of the following problems:the source of the problem was not properly identified,the wrong treatment was carried out, orthe correct treatment was improperly performed. Comprehensively identifying the source of the water control problem is the first and most important step in suggesting a solution. Well logs can be very effective at diagnosing downhole situations that can lead to unwanted water production. Casing leaks, cement channels, coning, and watered-out reservoirs are all typical sources of unwanted water that can be easily defined with well logs. Evaluating the effectiveness of water control treatments with cased-hole logs can help determine the success of the procedures. In many cases, ineffective treatments may need only a simple remedial second pass to accomplish the original goals. Specific applications are provided showing the use of open-hole, production logging, pulsed neutron, and casing/cement evaluation logs that detect and define downhole problems that can lead to the unwanted production of water. Open-Hole Evaluation Open-hole logs can be very useful in determining possible causes and sources of unwanted water or gas production. Caliper logs are good for finding areas where severe borehole washout has occurred that can contribute to poor cement bonding. Gamma ray and SP logs can be used to delineate shale beds from possible water or hydrocarbon producing reservoirs. Resistivity and porosity logs (sonic, density, neutron) can be combined to determine the location of water and pay zones which later can be compared to cased-hole logs to monitor changing water levels or look for coning in producing reservoirs. Full wave sonic measurements can be combined with bulk density log data to predict fracture height as a function of the differential pressure between downhole treatment pressure and fracture closure pressure. The log shown in figure 1 shows a FracPressure analysis. Fracture height predictions were made prior to the treatment to ensure that job design limited fracture growth, avoiding the water table. Track 1 contains the gamma ray and borehole profile. Fracture pressure is the amount of pressure equal to the least principle horizontal stress, and is computed from the rock properties measured by sonic and density logs. This stress profile identifies barriers to fracture growth and stress contrasts between producing zones. Track 2 shows the calculated static fracture initiation and closure pressures. The fracture initiation pressure is the pressure applied to begin the fracture. Track 3 shows formation lithology as determined from a computing center open-hole log analysis.