Fracture Prepropping and Temporary Plugging for Formation Damage Control in Deep Naturally Fractured Tight Reservoirs

Abstract

Summary To address the challenges of formation damage related to drill-in fluid loss into deep reservoir fractures during the drill-in process, we propose pre-propping and temporary plugging (PPTP) technology as an integrated solution in this paper. The PPTP approach combines high-strength bridging (HSB) materials with self-degrading filling (SDF) materials for efficient fracture plugging during lost circulation and effective fracture propping during oil and gas production from deep naturally fractured reservoirs. HSB material with good mechanical properties and SDF material with a controllable degradation cycle are developed and systematically evaluated. Fracture plugging tests and stress sensitivity experiments are conducted to evaluate the transformation effect of fracture plugging zones on fracture propping zones. Research results show that the developed HSB material exhibits a high compressive capacity and friction coefficient, which maintains a crushing rate below 3% under 60 MPa pressure and an average friction coefficient of 1.56. The degradation ratio of SDF material increases with temperature and pH value. The degradation cycle can reach up to 168 hours under the conditions of 120°C and pH = 13, which ensures continuous stable fracture plugging and lost-circulation control during the drill-in process. The PPTP technology, combining HSB and SDF components, efficiently plugs fractures with widths ranging from 1.0 mm to 3.0 mm, with a maximum plugging pressure of up to 10.16 MPa. HSB material props the fractures after SDF degrades, preventing fracture closure and converting the fracture plugging zone into a propping zone. The stress sensitivity damage of reservoir fractures can be effectively mitigated, preserving and enhancing fracture conductivity. Thus, the PPTP technology shows great potential for the integration solution of drill-in fluid loss and formation damage in deep naturally fractured reservoirs.