Herz-Thyhsen Ryan J, Miller Quin R S, Rother Gernot, Kaszuba John P, Ashley Thomas C, Littrell Kenneth C
Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, United States.
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
ACS Appl Mater Interfaces. 2021 Apr 7;13(13):15811-15819. doi: 10.1021/acsami.0c22524. Epub 2021 Mar 26.
Hydraulic fracturing of low-permeability rocks significantly enhances hydrocarbon production from unconventional reservoirs. However, fluid transport through low-permeability rocks and the influence of geochemical transformations on pore networks are poorly constrained. Mineral reactivity during interactions with injected water may alter the physical nature of the rock, which may affect hydrocarbon mobility. To assess alterations to the rock, we have previously conducted a hydrothermal experiment that reacted cubed rock samples (1 cm) with synthetic hydraulic fracturing fluid (HFF) to simulate physicochemical reactivity during hydraulic fracturing. Here, we analyze unreacted and reacted rocks by small-angle neutron scattering and high-pressure mercury intrusion to determine how the pore networks of unconventional reservoir rocks are influenced by the reaction with hydraulic fracturing injectates. Our results suggest that fluid-rock interactions exhibit a two-fold influence on hydrocarbon recovery, promoting both hydrocarbon mobilization and transport. Pore-matrix interfaces smooth via the removal of clay mineral surface asperities, reducing the available surface area for hydrocarbon adsorption by 12-75%. Additionally, HFF-induced dissolution creates new pores with diameters ranging from 800-1400 nm, increasing the permeability of the rocks by a factor of 5-10. These two consequences of mineral dissolution likely act in concert to release hydrocarbons from the host rock and facilitate transport through the rock during unconventional reservoir production.
低渗透岩石的水力压裂显著提高了非常规油藏的烃产量。然而，流体在低渗透岩石中的运移以及地球化学转变对孔隙网络的影响尚不清楚。与注入水相互作用期间的矿物反应性可能会改变岩石的物理性质，这可能会影响烃的流动性。为了评估岩石的变化，我们之前进行了一项热液实验，使立方体岩石样品（1厘米）与合成水力压裂液（HFF）反应，以模拟水力压裂过程中的物理化学反应性。在此，我们通过小角中子散射和高压压汞法分析未反应和已反应的岩石，以确定非常规油藏岩石的孔隙网络如何受到与水力压裂注入液反应的影响。我们的结果表明，流体-岩石相互作用对烃采收率有双重影响，既促进了烃的运移又促进了烃的传输。孔隙-基质界面通过去除粘土矿物表面粗糙度而变得光滑，使烃吸附的可用表面积减少了12%-75%。此外，HFF诱导的溶解产生了直径范围为800-1400纳米的新孔隙，使岩石的渗透率提高了5-10倍。矿物溶解的这两个结果可能共同作用，从母岩中释放烃，并在非常规油藏开采期间促进烃在岩石中的传输。
