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裂缝是影响致密砂岩储层天然气产能的主要因素,但井下裂缝的产状、规模和面孔率很难直接测量。通过选取与目的层地质情况相似的典型露头剖面,在人工测量、取样和室内分析化验的基础上,利用激光扫描技术对其进行多次覆盖以获取三维点云数据,配合高分辨率数码照片和人工实测裂缝信息,在数据体剖面上对裂缝进行精细解释,借助计算机模拟技术建立数字化裂缝模型和储层地质模型,更为准确地展示了研究区裂缝发育规律和控制因素,为井下储层预测提供更真实的地质信息。结果表明,研究区主要发育3组优势倾向剪切裂缝,倾角大,延伸长度短,裂缝间距呈略正态分布。裂缝开度与产状密切相关,具有双峰特征,分别为0.2~0.4mm和0.8~1mm。横向上单组和双组优势裂缝疏密相间分布,可划分为贯穿缝带和层间缝带,其中贯穿缝带裂缝具有较大的延伸长度和间距,较小的面密度且大部分贯穿邻近泥岩,后者正好相反。定量计算了剖面上11个单砂体的裂缝面孔率,范围为0.026%~0.081%,平均为0.05%,水下分流河道砂体要好于河口坝和远砂坝。裂缝发育规模受岩性、层厚、最大古主应力和岩矿成分等多个因素控制,之间存在较好的幂指数相关关系。
Cracks are the main factors that affect natural gas productivity in tight sandstone reservoirs. However, the shape, size and porosity of downhole fractures are difficult to measure directly. By selecting the typical outcrop profile similar to the geology of the destination layer, based on the manual measurement, sampling and laboratory analysis, laser scanning technology is used to cover the three-dimensional point cloud data to obtain high-resolution digital photos and Manually measured fracture information is used to finely interpret fractures on the data body profile. Digital fracturing models and reservoir geological models are established by means of computer simulation techniques to more accurately display the fracture development rules and control factors in the study area, Provide more real geological information. The results show that there are three predominant shear fractures in the study area, with large dip angle, short extension and slight normal distribution of fracture spacing. Crack opening and occurrence are closely related, with bimodal characteristics, respectively, 0.2 ~ 0.4mm and 0.8 ~ 1mm. In the transverse direction, the predominant cracks in single group and double group are densely and densely distributed, and can be divided into through-seam tapes and interlaminar tapes, in which the cracks extending through the tapes have larger extending length and spacing, the smaller areal density and most of them penetrate the adjacent Mudstone, the latter is the opposite. The fracture face porosity of eleven single sand bodies in the section is quantitatively calculated, ranging from 0.026% to 0.081% with an average of 0.05%. The underwater distributary channel sand body is better than the mouth bar and the distal sand bar. The scale of fracture development is controlled by a number of factors such as lithology, layer thickness, maximum paleo-principal stress and rock composition, and there is a good exponential relationship between fractures.