Modeling the swelling of shale matrix in unconventional reservoirs

作者：Bui Binh T^*; Tutuncu Azra N

来源：Journal of Petroleum Science and Engineering, 2018, 165: 596-615.

DOI：10.1016/j.petrol.2018.01.043

• Shale swelling
• Coupled modeling
• Unconventional reservoirs
• Dual-porosity model
• Water injection
• Mass transport

The imbibition of the injection water into shale matrix may result in shale swelling affecting oil recovery from the rock matrix and the transport properties of the fractures. The expansion of rock due to the swelling of shale matrix compresses the pore space in the rock matrix and the surrounding fractures. This reduces fracture and matrix porosity and permeability. The reduction of matrix pore space can reduce the rate of oil recovered from the rock matrix. On the other hand, it also forces the oil out of the matrix pore space increasing oil recovery. However, this effect has not been evaluated and integrated in reservoir modeling.
This study presents a coupled fluid flow and geomechanics model for modeling shale swelling to quantitatively investigate the effect of swelling on transport properties of rock matrix and fractures. The main objective is to quantitatively determine the effect of shale swelling on the oil recovery from the rock matrix. A numerical solution is presented to solve the coupled equations simultaneously for the phase pressure, fluid saturation, stress, and strain. We show that the mechanical properties of the rock matrix vary significantly as the result of water imbibition. The reduction of the fracture and matrix permeability and porosity due to swelling is considerable. This results in the reduction of more than 50% of the oil recovered from shale matrix. Hence, shale swelling should be prevented in any water injection operations.

• 出版日期2018-6