页岩气层裂缝气侵机理及封堵抑制方法

Fracture gas invasion mechanism and plugging method of shale gas layer

为探讨页岩地层裂缝气侵机理及控制对策,通过开展页岩裂缝气侵模拟实验,揭示气侵机理并探讨针对性的气侵抑制方法。研究发现,页岩裂缝气侵包括非致漏裂缝气侵和致漏裂缝气侵两类,封堵带渗透率和有效长度是非致漏裂缝气侵的关键控制因素,而封堵失效是诱发致漏裂缝气侵的根本原因。对于非致漏裂缝而言,可以将纳米颗粒掺入钻井液,利用纳米颗粒对钻井液固相颗粒间的纳微孔隙进行封堵,增强封堵带致密性实现抑制气侵;致漏裂缝则可以采用向钻井液中添加堵漏材料与纳米颗粒,并通过堵漏材料在裂缝中架桥和纳米颗粒的致密充填协同作用实现抑制气侵。

This paper takes the gas invasion of Longmaxi shale reservoir in Weirong Block, Sichuan Basin as the research object. Through the gas invasion simulation experiment of shale fractures, the mechanism of gas invasion is revealed, the targeted gas invasion suppression method is discussed, and the field application effect of the control method is analyzed. It is found that shale fracture gas invasion is composed of two types: non-leaky fracture gas invasion and leaky fracture gas invasion. Permeability and effective length of sealing zone are the key controlling factors for non-leaky fracture gas invasion, while sealing failure is the fundamental reason for inducing leaky fracture gas invasion. For non-leakage-inducing fractures, in order to enhance the compactness of sealing zone and inhibit gas invasion, nanoparticles can be incorporated into drilling fluid and used to seal the nano and micro pores between solid particles of drilling fluid. For leak-inducing fractures, plugging materials and nanoparticles can be added to the drilling fluid, and gas invasion can be inhibited by the synergistic effect of bridging the fracture with plugging materials and dense filling with nanoparticles.