REMINDER September 8th, 2022 DGS Luncheon Presentation – Carolina Mayorga-Gonzalez – NEW LOCATION

Reservoir Quality and Well Performance Analysis in the Middle Member of the Lewis Shale, Greater Green River Basin, WY

Carolina Mayorga-Gonzalez, Colorado School of Mines

Abstract:

The Lewis Shale is a turbidite system encompassing sandstones, siltstones, and organic-rich shales deposited during the last Cretaceous seaway transgression. Its lithological characteristics vary depending upon its location within the Lewis Shale depositional basin (eastern Greater Green River Basin). This basin is a large oil and gas producer in the United States, and it is expected to increase in the upcoming years. As a result, drilling operations in the area can significantly affect the wildlife by impacting their habitat and reproduction areas.

The main concerns of log analyses in tight sandstone reservoirs are porosity estimation, accurate water saturation calculation, permeability determination, and understanding how clay affects log responses. In addition, petrographic thin section, routine, and special core analyses are necessary to develop a reliable petrophysical model. Several authors have mentioned some of the petrophysical properties of the Lewis Shale. However, there are no petrophysical models in the sandstone intervals tying together log and core data to the author’s knowledge. Completion techniques are often one of the most expensive parts of drilling and producing a well. Therefore, the costs of proppant and completion fluid are significant in determining individual well or even field economic viability. To identify which one was affecting the production the most, the production analysis was made using the volume of proppant, the volume of fluid injected, the number of fracture stimulation stages, and production to infer their effect on production. But it seems there is no correlation between them.

The objective of this work is to develop a high-resolution reservoir characterization. This analysis is crucial for understanding this play and decreasing uncertainty when planning new well placements. This formation is considered an unconventional reservoir due to its low porosity and permeability and the need to use hydraulic fracturing to obtain hydrocarbons at commercial rates. In addition, this area around the cores is relatively undeveloped for horizontal wells. The petrophysical characteristics of these four core displayed the same level of heterogeneity as the facies described. Samples have high variation in water saturation values and, in general, very low porosity and permeability, characteristics of these reservoirs.

Ligia Carolina Mayorga-Gonzalez is a PhD from Colorado school of Mines. She obtaine her degree in May 2022.  She obtained her undergraduate degree in geology at the Universidad Nacional de Colombia in Bogota. She then pursued a master’s degree at the University of Oklahoma. She worked for two years as a reservoir geologist at MorningStar Partners focusing on the Lewis Shale formation in Wyoming.