New Understanding of Matrix-Fracture Dual Media Reservoir Damage Based on Pressure-Controlled Fracturing

The Tarim Oilfield Krasu tectonic zone is deeply burial, high temperature, low porosity and permeability, and constitutes the complex matrix-fracture dual media seepage channels. Reservoir damage evaluation for such reservoirs is important for subsequent development. In this study, we firstly processed the fracture network in the reservoir core by controlled-pressure fracturing to improve the fracture tortuosity, and verified the reasonableness of this method by CT scanning and shape factor calculation. Then, based on the dual-media condition, we establish the water/oil-lock damage evaluation method, the stress-sensitive evaluation method, the fluid-sensitive evaluation method, and the in-well fluid damage evaluation method. Based on the above methods, the sensitivity of matrix-fracture dual-media reservoirs is moderately strong for water-oil locking, stress, and fluid salinity, moderately weak for liquid alkalinity, weakest for liquid flow rate. In-well fluid damage replacement experiments show that reservoir damage caused by first contact is the most important factor of reservoir damage during the whole process of drilling-completion-reconstruction. For deep tight reservoirs, fracturing fluid is easy to cause serious reservoir damage, and it is necessary to pay attention to reservoir protection during fracturing in low-yield blocks. 1. INTRODUCTION Reservoir damage is defined as any process that causes a reduction in the natural inherent productivity of gas or oil producing reservoir, or a reduction in the injectivity of a water or gas injection well (Ahmed E. 2021). Reservoir damage is a generic term. It relates to the permeability reduction of a reservoir due to a series of adverse processes (Lucas G. 2012). In the process of oil and gas development, the oil and gas transportation channels are blocked by fluids, stresses and other factors, and the permeability of the reservoir rock decreases (Civan, F., 2000; Radwan, A.E.2019a; Radwan, A.E.2019b). Fomlation damage from drilling and completion fluids can have substantial impact on the productivity of a well (L. Bailey, 1998). During hydraulic fracturing, a large amount of fracturing fluid is retained in the fractures and cannot be discharged, blocking the pores and fractures and reducing the gas relative permeability of the reservoir (Chen et al., 2021; O'Malley et al., 2016; Zhang et al., 2019; King et al., 2012). The main types of fluid damage to reservoirs includes water sensitivity damage, acid sensitivity damage, alkali sensitivity damage and velocity sensitivity damage (Zhou, 2022). Stress sensitivity damage means that after the microfracture closes under the effective stress action, the reservoir filtration capability decreases greatly. And the closed fracture is difficult to open after the effective stress release (Hana, 2022).