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Relating Natural Fractures and Fluid Migration in Permian Basin Horizontal Wells: Ideas for Completion Optimization

Abstract

There is an increasing shift amongst horizontal well operators from geometric to engineered hydraulic fracture stimulation designs. These engineered fracs are often the result of geomechanics analyses, with many technologies available to collect measurements such as Young’s Modulus and Poisson’s Ratio right at the drill bit. Characterizing stresses, bedding, and natural fractures can lead to improved stage placement and cluster spacing. This is only part of the problem, however, as there is still the missing component of the changes in fluid composition as a result of changing geomechanical properties. Geochemical techniques, specifically including hydrocarbon molecular and isotopic chemistry are increasingly integrated to ascertain information about hydrocarbon production from shales including hydrocarbon source, fluid compartmentalization, and other information relevant to addressing the problems described above. By measuring the noble gas composition in paired fluids and mineral solids, noble gases can be specifically useful for defining the physico-chemical conditions of fluid origin, migration mechanisms, residence time of fluids, and rock, matrix permeability, and storage conditions. The 4He/21Ne* ratio is useful for tracing fluid flow because, although their initial production ratio is fixed, both 4He and 21Ne* interact with quartz crystals differently. 4He diffuses readily through quartz and other silicates over geologic time and equilibrates with pore fluids, while the blocking temperature for 21Ne is ~80oC corresponding to the onset of catagenesis. Although many studies explore fracture-related fluid flow by monitoring helium migration alone, the relative 4He/21Ne* ratio provides a significantly more robust and sensitive marker for fluid migration processes. As a result, the 4He/21Ne* can be used to provide an estimate of the rock volume on which fluids interact, the length-scale of fluid migration, and provide insights into the temperatures conditions (i.e., burial depth) at which paleofluid flow occurred. Here, we combine the 4He/21Ne* measurements of drill cuttings and associated fluids from the laterals of Delaware (Permian) Basin horizontal wells with geomechanical data collected while drilling. Preliminary data from this study suggest that noble gas data can be used to differentiate hydraulically conductive zones of faulting and increased fracture intensity from low conductivity zones, which can then be used to optimize completion design.