Net Pay--What Is It? What Does It Do? How Do We Quantify It? How Do We Use It?
- Paul F. Worthington (Gaffney, Cline & Associates)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- October 2010
- Document Type
- Journal Paper
- 812 - 822
- 2010. Society of Petroleum Engineers
- 5.1.1 Exploration, Development, Structural Geology
- net pay, estimates of ultimate recovery
- 7 in the last 30 days
- 2,710 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 10.00|
|SPE Non-Member Price:||USD 30.00|
A knowledge of net pay is important for the volumetric estimation of hydrocarbon resources, a practice that underpins the value of the petroleum industry. Yet, there is no universal definition of net pay, there is no general acceptance of its role in integrated reservoir studies, there is no recognized method for evaluating it, and there are disparate views on how to make use of it. Partly for these reasons, net-to-gross pay constitutes a major source of uncertainty in volumetric reserves estimates, second only to gross rock volume. With the aim of improving this unsatisfactory state of affairs, I chart a critical path of net-pay understanding and application to dispel some of the unhelpful myths that abound within the industry and replace them with a defensible rationale to guide the quantification of net pay (thickness). Central to this process is the identification of net-pay cutoffs, themselves the subject of much controversy over the years. The approach is data-driven, in that it uses what we know, and also fit-for-purpose, in that it takes account of reservoir conditions. The outcome is a sounder basis for incorporating net pay into volumetric estimates of ultimate recovery and thence hydrocarbon resources.
|File Size||558 KB||Number of Pages||11|
Aguilera, R. 2003. Net pay in naturally fractured reservoirs. CSPGReservoir 30 (6): 28-29.
Bennion, D.B., Thomas, F.B., Imer, D., and Ma, T. 2000. Low Permeability Gas Reservoirs andFormation Damage--Tricks and Traps. Paper SPE 59753 presented at theSPE/CERI Gas Technology Symposium, Calgary, 3-5 April. doi:10.2118/59753-MS.
Boak, J.M. 1992. Conversion of Well Log Data to Subsurface Stratigraphic andStructural Information. Part 6. Geological Methods. In Development GeologyReference Manual, Vol. ME 10, 289-293. Tulsa: AAPG Methods in ExplorationSeries, AAPG.
Brown, C.A., Erbe, C.B., and Crafton, J.W. 1981. A Comprehensive Reservoir Model ofthe Low Permeability Lewis Sands in the Hay Reservoir Area, Sweetwater County,Wyoming. Paper SPE 10193 presented at the SPE Annual Technical Conferenceand Exhibition, San Antonio, Texas, USA, 4-7 October. doi:10.2118/10193-PA.
Caldwell, R.H. and Heather, D.I. 2001. Characterizing Uncertainty In Oil andGas Evaluations. Paper SPE 68592 presented at the SPE Hydrocarbon Economicsand Evaluation Symposium, Dallas, 2-3 April. doi: 10.2118/68592-MS.
Cobb, W.M. and Marek, F.J. 1998. Net Pay Determination for Primary andWaterflood Depletion Mechanisms. Paper SPE 48952 presented at the SPEAnnual Technical Conference and Exhibition, New Orleans, 27-30 September. doi:10.2118/48952-MS.
Cosentino, L. 2001. Integrated Reservoir Studies. Paris: EditionsTechnip.
Desbrandes, R. 1985. Encyclopedia of Well Logging. Paris: EditionsTechnip.
Egbele, E., Ezuka, I., and Onyekonwu, M. 2005. Net-To-Gross Ratios: Implications inIntegrated Reservoir Management Studies. Paper SPE 98808 presented at theNigeria Annual International Conference and Exhibition, Abuja, Nigeria, 1-3August. doi: 10.2118/98808-MS.
Finley, R.J. 1985. ReservoirProperties and Gas Productivity of the Corcoran and Cozzette Tight Sandstones,Colorado. Paper SPE/DOE 13852 presented at the SPE/DOE Low Permeability GasReservoirs Symposium, Denver, 19-22 May. doi: 10.2118/13852-MS.
Flølo, L.H., Menard, W.P., Weissenburger, K.W., Kjærefjord, J.M., andArnesen, D.M. 1998. Revealing thePetrophysical Properties of a Thin-Bedded Rock in a Norwegian Sea Reservoir bythe Use of Logs, Core, and Miniperm Data. Paper SPE 49326 presented at theSPE Annual Technical Conference and Exhibition, New Orleans, 27-30 September.doi: 10.2118/49326-MS.
George, C.J., and Stiles, L.H. 1978. Improved Techniques for EvaluatingCarbonate Waterfloods in West Texas. J Pet Technol 30 (11):1547-1554. SPE 6739-PA.
Grieser, B., Brinska, J., and Stout, R. 2001. Zone Selection and ProductionPrediction Using Advanced Logging Technology. Paper SPE 67198 presented atthe SPE Production and Operations Symposium, Oklahoma City, Oklahoma, USA,24-27 March. doi: 10.2118/67198-MS.
Holtz, M.H. and Hamilton, D.S. 1998. Reservoir CharacterizationMethodology to Identify Reserve Growth Potential. Paper SPE 39867 presentedat the International Petroleum Conference and Exhibition of Mexico,Villahermosa, Mexico, 3-5 March. doi: 10.2118/39867-MS.
Hunter, C.D., Kilgo, W.M., and Hickman, T.S. 1990. The Development of a MarginalClearfork Waterflood Prospect. Paper SPE 20128 presented at the PermianBasin Oil and Gas Recovery Conference, Midland, Texas, USA, 8-9 March. doi:10.2118/20128-MS.
Joshi, S. and Lahiri, G. 1998. Integrated Reservoir Characterizationof Neelam Field. Paper SPE 39742 presented at the SPE Asia PacificConference on Integrated Modelling for Asset Management, Kuala Lumpur, 23-24March. doi: 10.2118/39742-MS.
Kessler, C., Frisch, G., Hyden, R., and Stegent, N. 2000. New Petrophysical Process ImprovesReservoir Optimization by Linking Stimulation Design, Reservoir Modeling, andEconomic Evaluation. Paper SPE 62544 presented at the SPE/AAPG WesternRegional Meeting, Long Beach, California, USA, 19-22. doi:10.2118/62544-MS.
Lemos, W.P., Baláo de Castro, M.R., Soares, C.M., Rosalba, J.F., and Meira,A.A.G. 2006. Albacora Leste FieldDevelopment: Reservoir Aspects and Development Strategy. Paper OTC 18056presented at the Offshore Technology Conference, Houston, 1-4 May. doi:10.4043/18056-MS.
Maricic, N., Mohaghegh, S.D., and Artun, E. 2008. A Parametric Study on the Benefits ofDrilling Horizontal and Multilateral Wells in Coalbed Methane Reservoirs.SPE Res Eval & Eng 11 (6): 976-983. SPE-96018-PA. doi:10.2118/96018-PA.
Martin, F.D., Murphy, M.B., Stubbs, B.A., Uszynski, B.J., Hardage, B.A.,Kendall, R.P., Whitney, E.M., and Weiss, W.W. 1999. Reservoir Characterization as aRisk-Reduction Tool at the Nash Draw Pool. SPE Res Eval & Eng 2 (2): 169-179. SPE-56007-PA. doi: 10.2118/56007-PA.
Ringrose, P.S. 2008.Total-Property Modeling: Dispellingthe Net-to-Gross Myth. SPE Res Eval & Eng 11 (5):866-873. SPE-106620-PA. doi: 10.2118/106620-PA.
Schlachter, G. 2007. UsingWireline Formation Evaluation Tools To Characterize Coalbed MethaneFormations. Paper SPE 111213 presented at the Eastern Regional Meeting,Lexington, Kentucky, USA, 17-19 October. doi: 10.2118/111213-MS.
Schoeling, L.G. and Mark, S. 2000. Improved ReservoirManagement/Characterization for Independent Operators in Mature Basins, A CaseStudy: South Slattery Field, Powder River Basin, Wyoming. Paper SPE 59299presented at the SPE/DOE Improved Oil Recovery Symposium, Tulsa, 3-5 April.doi: 10.2118/59299-MS.
Snyder, R.H. 1971. A Review ofthe Concepts and Methodology of Determining "Net Pay." Paper SPE 3609presented at the SPE Annual Technical Conference and Exhibition, New Orleans,3-6 October. doi: 10.2118/3609-MS.
SPE, WPC, AAPG, and SPEE. 2007. Petroleum Resources Management System, http://www.spe.org/industry/reserves/docs/Petroleum_Resources_Management_System_2007.pdf.
Spivey, J.P. and Pursell, D.A. 1998. Errors in Input Data and the Effecton Well-Test Interpretation Results. Paper SPE 39773 presented at the SPEPermian Basin Oil and Gas Recovery Conference, Midland, Texas, USA, 23-26March. doi: 10.2118/39773-MS.
Tearpock, D.J. and Bischke, R.E. 1991. Applied Subsurface GeologicalMapping. Englewood Cliffs, New Jersey, USA: Prentice-Hall.
Thomas, E.C. and Stieber, S.J. 1975. The Distribution of Shale in Sandstonesand its Effect Upon Porosity. Trans., SPWLA Annual Logging Symposium,4-7 June, Paper T, 1-15.
Worthington, P.F. 2000. Recognition and evaluation of low-resistivity pay.Petroleum Geoscience 6 (1): 77-92.
Worthington, P.F. 2008. TheApplication of Cutoffs in Integrated Reservoir Studies. SPE Res Eval& Eng 11 (6): 968-975. SPE-95428-PA. doi:10.2118/95428-PA.
Worthington, P.F. and Cosentino, L. 2005. The Role of Cutoffs in IntegratedReservoir Studies. SPE Res Eval & Eng 8 (4):276-290. SPE-84387-PA. doi: 10.2118/84387-PA.
Yeager, D.L., Frantz, J.H. Jr., Moody, M.A., and Neese, M.A. 1996. Evaluation of Infill DrillingPotential of the Beekmantown Formation, Bakersville Field, Coshocton County,Ohio. Paper SPE 37335 presented at the SPE Eastern Regional Meeting,Columbus, Ohio, USA, 23-25 October. doi: 10.2118/37335-MS.