Reservoir characterization, performance monitoring of waterflooding and development opportunities in Germania Spraberry Unit.

摘要

The Germania Unit is located in Midland County, 12 miles east of Midland, Texas and is part of the Spraberry Formation in the Midland Basin which is one of the largest known oil reservoirs in the world bearing between 8.9 billion barrels and 10.5 billion barrels of oil originally in place. The field is considered geologically complex since it comprises typically low porosity, low permeability fine sandstones, and siltstones that are interbedded with shaly non-reservoir rocks. Natural fractures existing over a regional area have long been known to dominate all aspects of performance in the Spraberry Trend Area. Two stages of depletion have taken place over 46 years of production: Primary production under solution gas drive and secondary recovery via water injection through two different injection patterns. The cumulative production and injection in Germania as of July 2003 were 3.24 million barrels and 3.44 million barrels respectively and the production level is 470 BOPD through 64 active wells with an average rate per well of 7.3 BOPD and average water cut of 60 percent. This performance is considered very low and along with the low amount of water injected, waterflood recovery has never been thoroughly understood. In this research, production and injection data were analyzed and integrated to optimize the reservoir management strategies for Germania Spraberry Unit. This study addresses reservoir characterization and monitoring of the waterflood project with the aim of proposing alternatives development, taking into account current and future conditions of the reservoir. Consequently, this project will be performed to provide a significant reservoir characterization in an uncharacterized area of Spraberry and evaluate the performance of the waterflooding to provide facts, information and knowledge to obtain the maximum economic recovery from this reservoir and finally understand waterflood management in Spraberry. Thus, this research describes the reservoir, and comprises the performance of the reservoir under waterflooding, and controlled surveillance to improve field performance. This research should serve as a guide for future work in reservoir simulation and reservoir management and can be used to evaluate various scenarios for additional development as well as to optimize the operating practices in the field. The results indicate that under the current conditions, a total of 1.410 million barrels of oil can be produced in the next 20 years through the 64 active wells and suggest that the unit can be successfully flooded with the current injection rate of 1600 BWPD and pattern consisting of 6 injection wells aligned about 36 degrees respect to the major fracture orientation. This incremental is based in both extrapolations and numerical simulation studies conducted in Spraberry.