延安陆相页岩气藏“甜点”识别方法与技术研究

Research onmethods and technologies for identifying “Sweet spots” in Yan’an continental shale gas reservoir

鄂尔多斯盆地是我国典型的陆相沉积盆地,延安国家级陆相页岩气示范区具备页岩气成藏地质条件。该区中生界和上古生界页岩储层非均质性强、孔隙结构复杂,储层“甜点”识别和综合评价难度大,成为制约该区页岩储层勘探开发的关键。本文基于大量薄片观察鉴定,结合测井、录井资料,分析了控制陆相页岩储层的关键地质因素,提出陆相页岩气“甜点”评价技术和定量评价标准,对研究区储层完成综合评价。结果证实:(1)建立的“甜点”评价技术评价结果与延安地区陆相页岩气实际勘探开发效果吻合,相对于常规评价方法准确率大幅提高;(2)研究区页岩气“甜点”区基本沿湖盆中心展布,该区东南部北东向为页岩气富集区,是气藏开发的重点区域。该技术可有效促进陆相页岩气藏勘探开发,同类储层可借鉴。

The Ordos basin is a typical continental sedimentary basin, while the Yan’an national-level continental shale gas demonstration area has the geological conditions for shale gas accumulation. The Mesozoic and Upper Paleozoic shale reservoirs in this area have strong heterogeneity and complex pore structure. It is difficult to identify and comprehensively evaluate the “sweet spots” for the reservoirs, which has become the key to restricting the exploration and development of shale reservoirs in this area. Based on a large number of thin-section observations and identifications, combined with logging and mud logging data, the key geological factors that control continental shale reservoirs are analyzed, the continental shale gas sweet spots evaluation technology and quantitative evaluation criteria are proposed, and the comprehensive evaluation of the reservoirs in the study area is completed. The results confirm that:(1)The established sweet spot evaluation technology evaluation result is consistent with the actual exploration and development effect of continental shale gas in Yan’an area, and the accuracy rate is greatly improved compared with conventional evaluation methods;(2)The shale gas sweet spot in the study area is basically distributed along the center of the lake basin, the north-east direction in the southeast of this area is a shale gas enrichment area, which is a key area for gas reservoir development. This technology can effectively promote the exploration and development of continental shale gas reservoirs, and similar reservoirs can be used for reference.