临兴上古生界致密储层裂缝发育特征及对 致密气富集影响

临兴区块上古生界储集层为致密砂岩，裂缝发育特征及对致密气富集影响尚不清楚，一定程度上制约了甜点区预测。 根据岩心、露头、薄片及测井资料，分析了研究区裂缝发育特征，探讨了裂缝对致密砂岩气富集的影响。临兴区块上古生界主 要发育高角度缝，其次为中低角度缝及水平缝，微观上根据裂缝与矿物颗粒的相对位置关系，可识别出粒内缝、粒缘缝和穿粒 缝，其中粒缘缝最为发育。受塑性泥岩阻挡，裂缝垂向延伸较差，一般延伸1~2 m后消失于泥岩层中，受燕山期北西-南东向 地应力影响，裂缝走向多为北东-南西向，裂缝密度一般2~5条/ｍ。裂缝可改善储集空间、提高油气充注效率，储层裂缝发育 区渗透率可增大1~2个数量级，含气饱和度高，此外，研究区裂缝是油气垂向运移的有效通道，影响着石盒子组及石千峰组致 密气的富集，在后期的勘探开发过程中应充分寻找裂缝发育区，并通过进一步压裂获得高产。

Development of Fractures and Its Effects on Gas Accumulation in the Upper Paleozoic Tight Sandstone Reservoirs of the Linxing Block

The Upper Paleozoic reservoirs in the Linxing block, Ordos Basin, were tight sandstones. Fractures characteristics and its effects on gas accumulation were unclear. This limited the prediction of sweet spots in the region. Based on the data and analyses of outcrop, core, thin section and well logging, the development characteristics of the fractures in the study area was analyzed, and their effects on tight gas accumulation were discussed. Results show that the Upper Paleozoic reservoirs of the Linxing block mainly developed high-angle fractures, followed by mid-low-angle and horizontal fractures. According to the relationship between fractures and mineral grains, the intragranular fractures, the grain-edged fractures and grain-crossed fractures could be identified microscopically, of which the grain-edged fractures were the most developed. Influenced by the plastic mudstones, vertical extension of the fracture was poor, and thus the fractures usually disappeared in the mudstones after stretching one to two meters. Due to the northwest-southeast ground stress in the Yanshanian period, the fracture strike was mostly northeast-southwest in trending, and the fracture density was two to five every meter. The fractures could improve the reservoir’s porosity and gas filling efficiency. In the fracture areas, permeability can be increased by one to two orders of magnitude and gas saturation is higher. In addition, the fractures were the effective pathway of gas migration and affected the enrichment of tight sandstone gas. In the future exploration and development, the fracture-developed area should be fully explored and further fracturing should be carried out to obtain higher production.period.