鄂尔多斯盆地姬塬油田上三叠统延长组超低渗透砂岩储层微裂缝研究

A Study on Micro Cracks in Super-Low Permeability Sandstone Reservoir of the Upper Triassic Yanchang Formation in the Ordos Basin

通过对鄂尔多斯盆地姬塬油田上三叠统延长组长4+5油藏的精细描述,指出微裂缝对提高储层渗流能力、提高超低渗透油藏开发效果具有十分重要的意义。研究表明,鄂尔多斯盆地姬塬油田上三叠统延长组长4+5油藏微裂缝线密度为7.86条/cm,微裂缝开度为3.70μm,微裂缝间距为1.2723mm,微裂缝孔隙度为0.29%,微裂缝渗透率为3.32×10-3μm2。微裂缝孔隙度是基质孔隙度的2.74%,微裂缝渗透率是基质渗透率的12.15倍。微裂缝分布的差异性和不均一性是造成研究区超低渗透致密储层中有相对高渗透层的主要原因。微裂缝发育及展布状况是沉积微相带及基底断裂基础上成岩过程中多期古构造应力场与现今构造应力场共同作用的结果。在油气勘探中以寻找有利的沉积相—成岩相—微裂缝带为勘探目标,会加大勘探成功率。

Through the reservoir description on Chang 4＋5 reservoir group of the Upper Triassic Yanchang Formation in the Jiyuan oil field, Ordos Basin, it is pointed out that micro crack is of great importance to increase the permeability and the development level of super-low permeability reservoir. The research shows that the density of the micro crack is 7.86 strips/cm, its width is 3.70μm, its space is 1.2723mm, its porosity is 0.29%, its permeability is 3.32×10^-3μm^2. The storage ability of micro crack is 2.74% to that of matrix, and its permeability ability is 12.15 multiple to that of matrix. The existence of relatively high permeability reservoir lies in the difference and heterogeneity of the distribution of micro crack in super-low permeability reservoir. The growth and the distribution of micro crack resulted from the mutual actions between multiple periods palaeotectonic stress fields and the present based on microfacies belt and basement fault. It＇s possible to improve the success ratio in the oil and gas exploration if the aim is focused on to find favorable sedimentary facies, diagenetic facies and micro-fracture ribbon.