页岩气储层人工裂缝优化及渗流规律研究

发布时间：2018-10-15 13:11

【摘要】：页岩储层是典型的低孔、低渗的致密储层,需要采取压裂改造技术才能获得有效产能。本文以延长组长7页岩为研究目标,在综合考虑储层特征、气体赋存状态和水力压裂技术基础上,建立了考虑页岩气多尺度流动形式的离散裂缝模型,探究了压裂后页岩气储层渗流规律。同时,运用数值试验的方法对裂缝参数进行优化,获得了人工裂缝、天然裂缝和基质的最优沟通关系,并通过室内裂缝渗透率测定试验验证了最优关系及模型建立的准确性。研究结果表明:长7页岩主要孔隙类型包括晶间孔、溶蚀孔、有机质孔、基质边缘孔和微裂缝,普遍发育高角度和低角度裂缝;孔隙半径主要分布范围广0~40μm,最小孔隙和裂缝尺度达到了纳米、微米级,平均孔隙度1.8%,平均渗透率7.8×10-6μm2,孔隙度小,渗透率极低,二者呈明显的负相关且相关性较差,储层孔隙结构较差,非均质性较强;根据页岩孔隙特征及气体流动状态,可将整个页岩气渗流过程分为基质表面的解析,微孔到大孔和微裂缝的扩散,以及在井筒附近、微裂缝以及人工裂缝中的达西流动三个过程。数值模拟结果表明,当人工裂缝与天然裂缝夹角75°时沟通最优。以此为优化基础,在给定的人工裂缝参数研究范围内对其优化并得出当人工裂缝长度为230m,缝宽7mm,裂缝间距120~140m,裂缝条数为3时,人工裂缝与天然裂缝、基质沟通最优。同时,对基质系统和天然裂缝系统参数优化得出:天然裂缝长度为70m,裂缝条数为4或5,裂缝间距为70m,沿着储层宽度方向改造储层改造比220:400,基质系统渗透率为1.686×10-2mD时,人工裂缝与基质、天然裂缝沟通最优。通过HXDL-2C型支撑剂裂缝评价系统对裂缝走向进行液测渗透率实验得出,人工裂缝与天然裂缝夹角为75°,裂缝走向最优,数值模拟结果与实验结果相契合,数值模拟结果及所建立的离散裂缝模型准确性。该研究结果对于压裂设计具有一定的理论指导价值。
[Abstract]:Shale reservoir is a typical tight reservoir with low porosity and permeability. Taking Yanchang No. 7 shale as the research goal, a discrete fracture model considering the multi-scale flow of shale gas is established on the basis of comprehensive consideration of reservoir characteristics, gas occurrence state and hydraulic fracturing technology. The percolation law of shale gas reservoir after fracturing is studied. At the same time, the optimum communication relationship between artificial crack, natural crack and matrix is obtained by optimizing fracture parameters by using numerical test method, and the accuracy of the optimal relationship and model establishment is verified by indoor fracture permeability measurement test. The results show that the main pore types of Chang 7 shale include intergranular pore, dissolution pore, organic pore, matrix edge pore and microfracture, and high angle and low angle fractures are commonly developed. The pore radius is mainly distributed in a wide range of 40 渭 m, the minimum pore and fracture scales are nanometer, micrometer, average porosity is 1.8, average permeability is 7.8 脳 10 ~ (-6) 渭 m ~ (2), porosity is small, permeability is extremely low, there is obvious negative correlation and poor correlation between them. According to the pore characteristics of shale and gas flow state, the whole shale gas seepage process can be divided into matrix surface analysis, micropore to macropore and microfracture diffusion, and near wellbore, the reservoir pore structure is poor and the heterogeneity is strong, and according to the shale pore characteristics and gas flow state, the whole shale gas seepage process can be divided into matrix surface analysis, micropore diffusion and microfracture diffusion, There are three processes of Darcy flow in microfracture and artificial fracture. The numerical simulation results show that the communication is optimal when the angle between artificial and natural cracks is 75 掳. On this basis, the artificial crack is optimized in the given range of artificial fracture parameters, and it is concluded that when the artificial crack length is 230 m, the fracture width is 7 mm, the crack spacing is 120 ~ 140 m, the number of cracks is 3, the communication between artificial crack and natural crack and matrix is the best. At the same time, the parameters of matrix system and natural fracture system are optimized: when the length of natural fracture is 70m, the number of fractures is 4 or 5, the distance of fracture is 70m, the reconstruction ratio of reservoir is 220: 400 along the direction of reservoir width, and the permeability of matrix system is 1.686 脳 10-2mD. Artificial crack and matrix, natural fracture communication is optimal. The hydraulic permeability test of fracture strike with HXDL-2C proppant fracture evaluation system shows that the angle between artificial fracture and natural fracture is 75 掳, the fracture strike is optimal, and the numerical simulation results agree with the experimental results. The results of numerical simulation and the accuracy of the established discrete fracture model. The research results have certain theoretical guiding value for fracturing design.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE37

【相似文献】