鄂尔多斯盆地长8、长6天然裂缝差异性研究及其对开发的影响

Study on the difference between the natural fractures in Chang 8 and Chang 6 reservoirs in Ordos Basin and its influence on the development of the reservoirs

通过野外露头、岩心观察、成像测井以及压裂施工曲线等资料的对比,认为鄂尔多斯盆地长8、长6特低渗储层天然裂缝发育程度差异较大,裂缝分布规律性明显.西南物源储层天然裂缝没有东北物源和湖盆中心储层天然裂缝发育.结合微地震监测资料,研究了天然裂缝发育程度对压裂缝控制作用,在天然裂缝发育区,由于人工压裂缝可能沿天然裂缝延伸,形成较大的有效渗流面积,因此,油田开发井网部署不仅要研究最大主应力方向,而且还要研究天然裂缝的发育程度,天然裂缝发育区适当放大井排距下仍能建立有效压力驱替系统,提高单井控制储量,降低水淹风险,这对指导特低渗油田注水开发具有重要的意义.

Through the conservation of outcrops and cores and the contrastive study of imaging well-logging data and fracturing curves,it is held that there is greater difference between the development degrees of the natural fractures in Chang 8 and Chang 6.The natural fractures in the reservoirs whose hydrocarbon is from the north-east and the reservoirs in the center of the basin are more developed than those in the reservoirs whose hydrocarbon is from south-west of the basin.With the information combining with microseismic monitoring data,the controlling effect of the natural fractures on fracturing fractures is studied.In the areas where the natural fractures are developed,the fracturing fractures may elongate along the natural fractures to form a larger effective percolation area,so not only the maximum principle stress direction but also the development degree of the natural fractures are studied when oilfield well network is arranged.In the areas where the natural fractures are developed,the distance between well rows can be properly increased,which can still establish effective pressure displacement system and reduce the risk of waterflooding.The research result in this paper is very important to the water injection development of ultra-low permeability reservoirs.