青海油田弱胶结生物泥岩气压裂裂缝起裂

Fracture Initiation of Weakly Consolidated Biological Mudstone Gas Fracturing in Qinghai Oilfield

涩北气田第四系泥岩生物成因气区块储层改造过程中压裂工艺参数优化缺乏理论基础和指导原则的问题日益突出。为探究第四系弱胶结生物泥岩裂缝起裂机理及影响规律,首先通过岩石基础实验,明确了弱胶结生物泥岩的矿物组成与力学特性,开展了弱胶结生物泥岩裂缝起裂实验研究,并通过数值模拟方法详细探究了固井质量和射孔深度对裂缝起裂的影响规律。研究结果表明,固井质量和射孔深度都是影响裂缝起裂的重要影响因素;在固井质量较差的情况下,压裂液进入第二界面堆积延伸,导致井眼发生严重扩径,无法达到裂缝起裂条件;深穿透射孔可以减小裂缝起裂尖端的塑性形变,降低裂缝的起裂压力。研究结果对弱胶结生物泥岩压裂工艺参数优化有一定的指导意义。

In order to investigate the fracture initiation mechanism and influencing factors of weakly consolidated biological mudstone in the Quaternary system of the Qinghai oilfield,a series of experiments was currently underway.Rock-based experiments were being used to determine the mineral composition and mechanical properties of the weakly consolidated biological mudstone.Additionally,fracture initiation experiments were taking place to investigate the crack initiation law in detail,while taking into account cementing quality and perforation depth.The results show that cementing quality and perforation depth are critical factors that affect fracture initiation.Specifically,the results indicate that poor cementing quality can lead to wellbore enlargement,making it difficult to achieve the conditions necessary for fracture initiation.Conversely,deep perforation reduces the plastic deformation of the fracture initiation tip and lowers the fracture initiation pressure.These results will have significant implications for the optimization of fracturing process parameters for weakly consolidated biological mudstone in the Quaternary system of the Qinghai oilfield.