A New Low-Damage Drilling Fluid for Sandstone Reservoirs With Low-Permeability: Formulation, Evaluation, and Applications

Drilling-induced formation damage is the key factor dominating the failure of the development of hydrocarbon reservoirs with low-permeability (i.e., tight formation). In this paper, a new low-damage drilling fluid was formulated, evaluated, and applied to well-drilling operations in a sandstone oil reservoir with low-permeability in the Shengli Oilfield, China. To formulate this low-damage drilling fluid, filter-cake forming agents were used to prevent fluid loss, inhibitors were used to enhance the shale inhibition of the fluid, surfactants were used to minimize water block, and inorganic salts were used to enhance compatibility. A holistic experimental approach combining micro-computed tomography (CT), scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) techniques was designed to identify the underlying interactions between new and conventional drilling fluids and rock samples as well as the corresponding damage mechanisms, demonstrating the significant mitigation effects of the newly formulated drilling fluid on formation damage, which mainly results from the hydration of clay minerals and the invasion of solid particles. The newly formulated low-damage drilling fluid then extended its applications to well-drilling operations with excellent performance. Not only can the new low-damage drilling fluid avoid non-fracturing stimulation, but also reduce the drilling operational costs and time, minimize the formation damage, and facilitate extending the reservoir life for a longer time.

钻井诱导的地层损害是主导低渗透（即致密地层）油气藏开发失败的关键因素。本文配制了一种新型低损害钻井液，对其进行了评价，并应用于中国胜利油田的一个低渗透砂岩油藏的钻井作业中。为了配制这种低损害钻井液，使用滤饼形成剂来防止流体损失，使用抑制剂来增强流体对页岩的抑制作用，使用表面活性剂来尽量减少水锁，使用无机盐来增强相容性。设计了一种结合微计算机断层扫描（CT）、扫描电子显微镜（SEM）、傅里叶变换红外光谱（FT - IR）和X射线衍射（XRD）技术的整体实验方法，以确定新型和常规钻井液与岩石样品之间潜在的相互作用以及相应的损害机制，证明了新配制的钻井液对地层损害有显著的缓解作用，地层损害主要是由粘土矿物的水化和固体颗粒的侵入造成的。新配制的低损害钻井液随后以优异的性能扩展了其在钻井作业中的应用。这种新型低损害钻井液不仅可以避免非压裂增产措施，还能降低钻井作业成本和时间，将地层损害降至最低，并有利于延长油藏寿命。