Experimental studies on the reservoir dynamics of water-based and gas-based fracturing fluids in tight rocks




Luo, Xiao

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Low permeability formations, including shale and tight reservoirs, have contributed over 50% of U.S. annual oil production. Many of these formations are oil productive formations, they include Bakken, Eagle Ford, Marcellus, Permian, and Utica. In order to obtain economic production, large amounts of fracturing fluids are consumed during the hydraulic fracturing treatments, but only a small fraction of the fluid is returned to the surface as flowback. Water-based fracturing fluids may invade the rock matrix in a tight or unconventional reservoir and result in a water block that hinders oil production. To remedy this possibility, gas- and foam-based fluids have been developed. For an oil productive formation, the invasion of gas can also result in oil permeability reduction, i.e. a gas block, but the mechanism and clean up are likely to be different than a water block. As the two fluids exhibit different wetting nature, it is not clear how they compare to each other in a multi-phase flow perspective, such as their impact on the productivity in the short and long term.
In this work, we conduct experimental studies the reservoir dynamics of invaded fracturing fluids, reduction in the hydrocarbon permeability, and potential mitigation for cleaning up the fluid block. We scaled down this fluid invasion problem to a laboratory core sample. Water and N₂ are injected into a rock matrix to mimic the invasion of slickwater and gas-based fracturing fluids, respectively. We studied the evolution of the oil productivity and flowback versus time during the oil production. The respective performances for different fracturing fluids under different conditions will also be investigated in this study.


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