Reservoir identification in the Bazhenov Formation from well log and core data

Abstract

Unconventional oil and gas development is one of the most challenging subjects of contemporary times. Despite the fact that certain black shales were known to geologists as hydrocarbon-bearing source rocks since the XIX century, it is only in the late twentieth century that they have been considered as viable alternatives to conventional oil and gas resources. This article provides a brief overview on the reservoir potential analysis of source rocks, as well as existing methods for evaluating the content of total organic carbon from well log data. The purpose of the research is to develop new ways to identify reservoirs within the Bazhenov Formation by analyzing well log and core data. The paper considers several methods of rock type classification within the Bazhenov Formation derived from well logs: U/Th ratio vs. total organic carbon, Gamma Ray vs. total organic carbon, and Gamma Ray vs. Density Log. Rock bulk volumes provide the basis for understanding the mineralogical composition and reservoir properties of a formation. The authors have proposed a technique of direct introduction of core analysis results to well logs in order to build up a more reliable bulk volume model of the Bazhenov Formation. New empirical relations to compute the density and compressional slowness of the Bazhenov Formation rocks were proved. This allows us to estimate the mechanical properties and predict the most brittle zones within the formation. The example of the Salym Field well demonstrates mechanical properties analysis and prediction of the most brittle zones considered as sweet spots.

Keywords

• unconventionals
• Bazhenov shale
• source rocks
• total organic carbon
• reservoirs
• fractures