流量替代渗透率评价破碎性储层工作流体伤害程度

若地层岩石整体强度偏低,在力学环境改变后岩石易破碎成不规则破裂体,则储存油气资源的此类破碎地层被称为破碎性储层。由于破碎性储层在纵向上存在着较强的非均质性,通过测试单个柱塞岩样在工作流体伤害前后的渗透率变化难以体现工作流体对储层的整体伤害程度。为此,利用达西定律先从理论上探讨用流量替代渗透率定量表征储层伤害程度的可行性,再开展单层开采、双层及三层并采的流量测试实验,评价工作流体对单层、多层储层的整体伤害程度,并将流量损害率与渗透率损害率进行对比以求证流量替代渗透率的可行性。研究结果表明:①单层开采时,流量损害率与渗透率损害率基本一致,渗透率损害率是流量损害率的一种特殊形式;②双层及三层并采时,单层各自稳定流量损害率与渗透率损害率接近,且流量损害率可以定量表征并采储层的整体伤害程度,而渗透率损害率则无法定量表证;③稳定流量损害率较累积流量损害率更接近渗透率损害率。结论认为,测定稳定流量可以替代测定渗透率评价工作流体对破碎性储层的伤害程度,从而为优选工程技术与评价工作流体的适应性提供了方法依据。

Evaluation of working fluid damage in fractured reservoirs usingflow rate instead of permeability

A "sofigenthcarbon formation" is a subsurface pool of hydrocarbons contained in the rock formations that can be easily broken into irregular fractured bodies when the mechanical environment changes. Typically, it happens on low overall strength rocks with anisotropic property of seepage and stress, such as coal, carbonate, unconsolidated sandstone or fractured tight sandstone, shale. Due to the strong heterogeneity of fractured reservoirs in the vertical direction, it is difficult to reflect the overall reservoir damage degree caused by working fluids by testing the permeability change of a single core plug before and after the intrusion of working fluids. To this end, this paper took advantage of the Darcy's law to theoretically discuss the feasibility of replacing the permeability with the flow rates to quantitatively characterize the reservoir damage degree. Then, the flow test experiments were carried out on single-layer development, double-layer joint development and three-layer joint development to evaluate the overall damage degree of single-layer and multi-layer reservoirs by working fluids. Finally, the flow damage degree was compared with the permeability damage degree to verify the feasibility of replacing permeability with flow rates. And the following research results were obtained. First, during the single-layer development, the flow-rate damage and the permeability damage are basically accordant, and the permeability damage degree is a special form of the flow-rate damage degree. Second, during the double-layer and three-layer joint development, the steady flow-rate damage degree of each layer is close to the permeability damage degree, and the flow-rate damage rate can quantitatively characterize the overall damage degree of jointly developed reservoirs, but the permeability damage degree cannot. Third, the steady flow-rate damage degree is closer to the permeability damage degree than the cumulative flow-rate damage degree. In conclusion, the determination of steady flow rates can be used as the substitute of permeability measurement to evaluate the damage degree of fractured reservoirs by working fluids, so as to provide a method and a basis for optimizing the engineering technology and evaluating the adaptability of working fluids.