Reservoir Characterization as a Risk Reduction Tool at the Nash Draw Pool

Abstract

F. David Martin, SPE, Dave Martin and Associates, Inc., Mark B. Murphy, Strata Production Company, Bruce A. Stubbs, SPE, Pecos Petroleum Engineering, Inc., Bruce J. Uszynski, Territorial Resources, Inc., Bob A. Hardage, Texas Bureau of Economic Geology, Richard P. Kendall, SPE and Earl M. Whitney, SPE, Dave Martin and Associates, Inc., and William W. Weiss, SPE, New Mexico Petroleum Recovery Research Center, New Mexico Institute of Mining and Technology Copyright 1997, Society of Petroleum Engineers, Inc. Abstract The Nash Draw Brushy Canyon Pool in Eddy County New Mexico is a cost-shared field demonstration project in the U.S. Department of Energy Class III Program. A major goal of the Class III Program is to stimulate the use of advanced technologies to increase ultimate recovery from slope-basin clastic reservoirs. Advanced characterization techniques are being used at the Nash Draw project to develop reservoir management strategies for optimizing oil recovery from this Delaware reservoir. Analysis, interpretation, and integration of recently acquired geological, geophysical, and engineering data revealed that the initial reservoir characterization was too simplistic to capture the critical features of this complex formation. Contrary to the initial characterization, a new reservoir description evolved that provides sufficient detail to indicate that substantial compartmentalization exists in the Brushy Canyon interval at Nash Draw. This new reservoir description is being used to identify "sweet spots" for an aggressive development drilling program as well as to optimize reservoir management strategies. As part of this strategy, a planned pressure maintenance project will be reevaluated in a more continuous part of the reservoir. This paper presents recent results of an integrated reservoir characterization effort that is being used at Nash Draw as a risk reduction tool. Introduction A producing property operated by Strata Production Company (Strata) in the Nash Draw Brushy Canyon Pool, Eddy County, New Mexico is a field demonstration site in the Department of Energy Class III program. The five-year project is in the second year of activities. The basic problem at the Nash Draw Pool (NDP) is the low oil recovery that is typically observed in similar Delaware reservoirs. By comparing a control area using standard infill drilling techniques to a similar area developed using advanced reservoir characterization methods, the goal of the project is to demonstrate that a development program based on advanced methodology can significantly improve oil recovery. During the first year of the project, four new wells were drilled as data acquisition wells, several hundred feet of whole core was obtained from one of the new wells, and vertical seismic profiles and a 3-D seismic survey were acquired. The advanced characterization effort is integrating geological, geophysical, petrophysical, geostatistical, production, and reservoir engineering data. The stratigraphic framework is being quantified in petrophysical terms using innovative rock-fabric/petrophysical relationships calibrated to wireline logs, and 3-D seismic attributes are being used to extrapolate petrophysical properties into the interwell area. Using the geological model developed in the first year of the project, a detailed reservoir description of the pilot area has been made, and current efforts are concentrating on defining the next generation geological model that will include 3-D seismic input and greater use of statistical methods. Reservoir characterization and simulation studies are being used to predict the distribution of remaining oil saturation and to optimize development drilling programs. Production and Recovery Challenges Production at the NDP is from the Brushy Canyon formation, a low-permeability turbidite reservoir of marginal quality. A challenge in developing the reservoir is to distinguish oil-productive pay intervals from water-saturated, non-pay intervals. Additionally, because initial reservoir pressure is only slightly above bubble-point pressure, rapid oil decline rates and high gas/oil ratios are typically observed in the first year of primary production. P. 751^