Lina Cao's research while affiliated with ZhenHua Oil and other places

The physical and chemical properties of hard brittle shale and its mechanical properties under different drilling fluid systems are of great practical significance to the in-depth study of shale borehole stability. Microscopic geological characteristics of hard brittle shale and the changes of physical and chemical properties after soaking different drilling fluids are revealed. After soaking in different drilling fluid systems, the mechanical properties have changed. After soaking in distilled water, water expands along micro-cracks due to the structural composition of rocks, eventually lead to cracking along the structural plane. After soaking in polysulfonate drilling fluid, the sample is destroyed and the strength of rock sample is weakened. After soaking in organic salt drilling fluid, the strength of rock sample weakens, drilling fluid fills the fracture surface to a certain extent. After soaking in oil-based drilling fluid, the strength of rock sample weakens, and oil-based drilling fluid fills and closes the fracture surface. The research results are of great significance to the analysis of borehole instability mechanism of hard brittle shale and drilling fluid optimization of shale gas drilling.

Multiflow mechanisms coexist in shale gas reservoirs (SGRs) due to the abundant nanopores and the organic matter as a medium of gas souring and storage. The gas transport mechanisms in nanopores including bulk gas transfer and adsorption‐gas surface diffusion were already investigated in pore‐scale models, but their effects on actual gas production of multistage fractured horizontal wells in SGRs are not clearly understood, which are crucial for the economic development of unconventional resources. Therefore, a comprehensive apparent permeability (AP) model which couples the surface diffusion of adsorbed gas, slippage flow considering the additional flux generated by surface diffusion based on Langmuir's theory, and Knudsen diffusion is established. The presented model is validated with the experimental data and lattice Boltzmann method (LBM) simulation results. Then, we propose a numerical model which combines multiflow mechanisms in microscale pores and a multistage fractured horizontal well (MSFHW) in macroscale shale gas reservoirs together. The effects of different transport mechanisms on both AP of nanopores and gas production are analyzed thoroughly. The results show that the effect of surface diffusion on the apparent permeability of nanopores is much greater than that on the actual gas production of MSFHW, and the influence of high‐pressure condition must be considered when calculating the surface diffusion coefficient. The presented numerical model has important implications for accurate numerical simulation and efficient development of shale gas reservoirs.