Calibration of Well Logs with Mini-Frac Data for Estimating the Minimum Horizontal Stress in the Tight Gas Monteith Formation of the Western Canada Sedimentary Basin: A Case Study

Abstract

Abstract The determination of the minimum horizontal in-situ stress is one of the most important aspects in the characterization of geomechanical behavior of petroleum reservoirs, since a good knowledge of such stress is critical in many activities of practical importance, including design of hydraulic fracturing treatments and estimation of the distribution of minimum horizontal stresses for reservoir simulation purposes. The main objective of the study is to calibrate well logs with available mini-frac data for estimating the minimum horizontal stress in the tight gas Monteith formation, Nikanassin Group of the Western Canada Sedimentary Basin (WCSB). For deep formations like Monteith, the minimum stress is generally horizontal. Thus, the focus of this research is the minimum horizontal stress of the Monteith formation. First, actual values of the minimum horizontal stress at different well locations are acquired from the analysis of surface pressure data during mini-frac treatments. Next, the estimates calculated from an existing correlation and from actual mini-frac data are matched for calibration purposes. Finally, Biot's constant values are determined in order to generate a correlation applicable to the Monteith formation. Vertical Biot's constants ranging between 0.1 and 0.2 are obtained in this study. Horizontal Biot's constant is assumed to be equal to 1.0. Three vertical wells located in the same township with available compressional and shear sonic logs and mini-frac data are selected for this work. Five additional wells in the same general area are selected to assist in the analysis. The Monteith was hydraulically fractured in isolation in these wells. This aspect is important because there are many commingled completions in the area from which selective Monteith data are not available. It is concluded that assuming a vertical Biot's constant equal to 1.0 is not appropriate for the Monteith formation in the study area. The procedure presented in this paper is robust and has the potential to help obtaining more reliable values in other tight formations around the world.