Abstract: Deep shale reservoirs are characterized by high closure pressure,high formation temperature,and high elastic modulus,making it challenging to achieve high conductivity fractures through fracturing.To effectively support and maintain pressure fractures in deep shale gas reservoirs,taking the deep shale of the Weiyuan Block in Sichuan as an example,based on an self-developed testing platform of API fracture conductivity,this study investigated the impact of high closure pressure (82.8 MPa) and high formation temperature (160 ℃) on the conductivity of supported fractures.The differences in conductivity under different types and combinations of proppants are compared,and the adaptability of self-supported fractures under deep shale conditions is analyzed.The results indicates that the high closure pressure is the main controlling factor for the decrease of fracture conductivity.Under the high closure pressure of 82.8 MPa,the positive effect of increasing sand concentration on conductivity is no longer evident;the high-temperature environment increases the degree of proppant breakage and embedment,with higher temperatures resulting in lower conductivity;the fracture conductivity of 40/70 mesh ceramsite proppant is significantly greater than that of 70/140 mesh quartz sand and micro-nano proppants;the conductivity of quartz sand and ceramsite (mass ratio of 1∶1) placed in sections is more economical and has higher conductivity than the whole mixed placement;the convex points on the wall of self-supported fractures are easily crushed under high closure pressure,showing strong stress sensitivity in conductivity,which is not conducive to maintaining conductivity in the later stages of production.The results of this study provide theoretical support for the design of fracturing parameters and optimization of conductivity in deep shale gas reservoirs.

Key words: deep shale, conductivity, high closing pressure, high reservoir temperature, self-supporting fractures