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An Integrated Multi-Disciplinary Approach to Mud Gas Mass Spectrometry Technology Implementation in Bakken/Three Forks Unconventional Tight Light Oil Play, Williston Basin, North Dakota


This paper discusses the implementation of a systematic, integrated, multi-disciplinary approach to utilizing mud gas mass spectrometry technology in the Middle Bakken and Three Forks tight oil reservoirs in Williston Basin, North Dakota. Mud gas, gamma log and cuttings are typically the only types of information routinely gathered during lateral well drilling in tight light oil plays. Mud gas composition carries a wealth of information about the petroleum system (e.g. charge, maturity) and the reservoir (e.g. oil versus water saturation, reservoir barriers, fractures, depletion). However, the signature of the reservoir gas coming to the surface with the drilling mud can be compromised by multiple factors, including mud gas recycling effects, different gas component extraction efficiency, variations in drilling mud, flow line and detector setups and drilling practices. Our approach is implemented in two main stages, and incorporates the integrated efforts of geologists, drilling engineers, completion engineers and reservoir engineers in both data acquisition and interpretation. During the first stage, a pilot test was performed on a vertical and lateral well-pair to evaluate different advanced mud gas technologies and their effectiveness. The results indicate that mud gas compositional parameters can identify higher porosity, oil saturated zones and distinguish reservoir compartments. The pilot test also provided clear evidence for the strong impact on mud gas composition of operating the mini-separator during lateral drilling. The second stage incorporates the learnings from the first stage with respect to data acquisition and data interpretation. It consists of extended field tests to further validate mud gas detection of natural fractures, reservoir compartments, oil versus water saturation, and depletion. It integrates mud gas data with cuttings analyses, geo-steering facies interpretations, data acquired during hydraulic frac operations, and surveillance during flow back data. These results provide a solid basis for optimization in lateral targeting and completion design to increase production and reduce operational costs.