OOIP Utilizing GEOCHEM [ECS] Data, Triple Combo Data Only, and Pyrolysis S1 Data Permian Wolfcamp "A" and "B" Shales

G. B. Asquith¹

¹Texas Tech University

Abstract

As a result of a very complete data set including Pyrolysis S1 data over an interval of 8035ft to 8497ft at 5ft intervals on a Wolfcamp well in the Midland Basin of Texas enabled the author an opportunity to compare different methods of calculating Oil in Place. The first OOIPstb calculation was done using only resistivity (AIT90), bulk density (*b), and neutron porosity (*nls) data with TOC determined by the Schmoker Equation. The volume of clay (Vcl), volume of quartz (Vqtz), and total porosity (*total) were determined by the Simultaneous Equation Method developed by Rick Lewis with Schlumberger. Effective porosity (*e) was calculated as *e = *total – (Vcl×*clay). Using a permeability cut-off of ka > 100nD {ka = [(0.0108×*oil) – 0.000256]×10^6} the OOIPstb/160 acres over the interval from 8035ft to 8494ft was 4.8mmbo.

The next OOIPstb calculation was done using AIT90, *b, and *nls data along with GEOCHEM [ECS] data. TOC was determined by the Schmoker Equation. The *total was determined with a variable matrix analysis using Vqtz, Vcalcite, Vkerogen, Vcl, and Vpyrite. Effective porosity (*e) was calculated as *e = *total – (Vcl×*clay). Using a permeability cut-off of ka > 100nD {ka = [(0.0108×*oil) – 0.000256]×10^6} the OOIPstb/160acres over the interval from 8035ft to 8494ft was 6.1mmbo.

The third method to determine Oil in Place was based on the method outlined by Downey and others (2011) using Pyrolysis S1 data. The equation used is listed below:

Oil in Place/160acres = *[1241.34×*b*S1×*oil*5'] 8035' to 8497'

Using the above equation the calculated Oil in Place/160acres was 5.2mmbo. The 5.2mmbo value compares favorable with the OOIPstb calculated by the other two methods [4.8mmbo and 6.1mmbo].

Does the general agreement of OOIPstb from GEOCHEM [ECS] and Triple Combo data with Oil in Place from Pyrolysis S1 data suggest that the use of a permeability cut-off of ka > 100nD may have validity in establishing a net pay cut-off for the Wolfcamp. In addition, the OOIPstb values calculated with only the Triple Combo data [AIT90, *b, and *nls] gave reasonable values [4.8mmbo] versus [6.1mmbo] using GEOCHEM [ECS] data is important, because a great many wells have only Triple Combo data.

AAPG Datapages/Search and Discovery Article #90190©AAPG Southwest Section Annual Convention, Midland, Texas, May 11-14, 2014