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Petrophysical Analysis of the 3rd Bone Spring Formation

Abstract

The Permian Basin is very attractive to oil companies and researchers due to the fact that it has the biggest potential oil production in the nation by 29% (e.g., Dutton, et al., 2003; Root, Attanasi, Mast, & Gautier, 1995; Galloway, et al., 1983). The area of the basin is roughly 86,000 square miles in Texas and New Mexico. The sub-basin of interest is situated to the West of the Central Platform in the Delaware Basin and covers approximately 10,000 square miles. The assigned formation for evaluation was the 3 rd Bone Spring sitting immediately above the Wolfcamp and located in the Leonardian period. The 3 rd Bone Spring formation is predominantly shaly-sand with intermittently inter-bedded carbonate layers. A full well-log suite including geochemical data was presented in the assignment for analysis. A series of systematic calculations were performed in both software programs Microsoft Excel (2013) and Techlog by Schlumberger (2013). Assigned calculations included; (1) thermal maturity using vitrinite reflectance, (2) total porosity, (3) effective porosity, (4) total organic carbon, (5) variable matrix analysis, (6) clay bound water, (7) OOIP using variable matrix analysis, (8) bitumen corrected OOIP, (9) T2 cutoff OOIP, (10) OOIP from rock evaluation data (S1), and finally (11) geo-mechanics. In addition, to generate rigorously defined conservative OOIP estimates and precise optimization of horizontal well placement we developed new and creative methods. The most conservative OOIP estimate using multiple stacked pay flags (MHI and Permeability combined) came from the Bitumen Corrected OOIP at 9700ft and an EUR of 0.9 MMstb. More precisely, the least conservative OOIP estimate using multiple stacked pay flags came from Variable Matrix Analysis using ECS data at 9698.5ft and an EUR of 4.1 MMstb. Finally, all optimized zones peaked within 5ft of each other regardless of the method of OOIP calculation. Given this additional level of assurance we determined the optimal placement was at 9700ft. This depth has a carbonate dominated layer with a marked decrease in gamma ray count allowing for accurate geolocation and geo-steering of the well bore.