Understanding the coupled transport of water and ions in gas shales for interpreting hydraulic fracture flowback data

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Oil and gas production from tight hydrocarbon resources by drilling and completion of multilateral/multifractured horizontal wells is becoming a common practice in the North America. However, efficient, responsible, and sustainable development of such resources requires careful evaluation of massive hydraulic fracturing operations involved. The main concerns include 1) inefficient recovery of fracturing water, 2) high concentration of various salts in the produced water, and 3) lack of reliable models for characterizing the induced fracture network using the pressure, rate and concentration data measured during flowback operations.This research hypothesizes that a large fraction of non recovered water is imbibed into the shale matrix during the shut-in period. To test this hypothesis, extensive flow experiments will be conducted on shale samples selected from cores drilled into different shale members of the Horn River Basin, located in northeastern British Colombia. It is estimated that up to 500 TCF of natural gas is stored in this basin, making it the third largest North American natural gas accumulation. This experimental study is aimed at understanding the fundamental mechanisms controlling the imbibition of fracture water into the shale matrix and diffusion of ions from shale into fracture water. Furthermore, the experimental data will be modeled to obtain the parameters required for modelling field scale processes including 1) spontaneous water leak off and salt concentration build up in fractures during the well shut in period, and 2) transport of water and salt during flowback operations.The proposed research, that will be conducted by two PhD and two MSc students, will help the industry to understand the complex interaction between water and shale for evaluating fracturing operations and optimizing future development plans.