鄂尔多斯盆地延长探区陆相页岩气勘探开发进展、挑战与展望

鄂尔多斯盆地为大型富油气叠合盆地,发育二叠系和三叠系多套页岩层系,陆相页岩气资源丰富。相比较于海相页岩,陆相页岩存在较多特殊性,其勘探开发面临诸多挑战,制约陆相页岩气难以实现经济开采,在地质特征、资源背景及勘探开发技术等方面对鄂尔多斯盆地页岩气勘探开发实践中取得的成果进行归纳,对目前的技术难点进行分析,以期在陆相页岩气发展进程中,有效利用机遇及时应对挑战。综合分析认为:延长探区陆相页岩厚度、有机碳含量、成熟度、含气量等参数达到国家标准规定的页岩气有利层段参数下限标准,具备页岩气成藏地质条件;陆相页岩气在宏观和微观非均质条件控制下,相态和规模上具有差异性富集特征,存在吸附成藏和吸附+游离复合成藏两类成藏模式,不同成藏机理指导陆相页岩气有利区优选及页岩气井生产。陆相页岩气勘探实践中形成多项关键配套工艺技术,建立起适用于强非均质性陆相页岩的测井评价方法,研发出适用于陆相页岩的水基钻井液体系和系列钻完井配套技术装备,形成CO_2压裂技术体系和井场废液回收处理—利用技术。同时,面临精细"甜点"预测、钻井提速提效、压裂环保增效、降低成本等诸多挑战。目前中国陆相页岩气仍处于勘探开发初期,成本高,初期产量低,还需通过开展陆相页岩气勘探开发先导性试验,实现科技突破,形成资源接替,促进陆相页岩气产业取得经济效益。

Progress,challenges and prospects of the continental shale gas exploration and development in the Yanchang exploration area of the Ordos Basin

As a large oil and gas-rich superimposed basin,the Ordos basin develops multiple sets of Permian and Triassic continental shale strata and is abundant in shale gas resources.Compared with marine shale,the continental shale is more complicated,and there are many challenges during its exploration and development,which restrict its economic exploitation.In this paper,in terms of the geological characteristics,resources background,and exploration and development technologies,the achievements in the practice of continental shale gas exploration and development in the Ordos basin were summarized.In addition,the current technical diffi culties of continental shale gas were analyzed,in order to effectively utilize opportunities and approach challenges in the development process timely.According to comprehensive analyses,shale gas parameters in the Yanchang exploration area,such as the lacustrine shale thickness,total organic carbon content,maturity,and gas content,have reached above the lower limit of favorable shale gas intervals stipulated by national standards.So the continental shale the geological conditions for gas accumulation.Under the control factors of macro and micro heterogeneous,continental shale gas has different enrichment characteristics in terms of phase state and scale.There are two types of accumulation modes,which are adsorption accumulation and adsorption+free composite accumulation.Understanding of different accumulation mechanisms guides the selection of the favorable zone and the production from continental shale gas wells.A number of key supporting technologies have been formed during the practice of continental shale gas exploration.Logging evaluation methods suitable for strong heterogeneous continental shale have been established.Water-based drilling fluid system and a series of supporting equipment for drilling and completion have been developed.CO2 fracturing technology system and wellsite waste fl uid recovery and treatment-utilization technology have been formed.Meanwhile,there are still many challenges in terms of precise prediction of“sweet spot”,acceleration and effi ciency of drilling,environmental protection and effi ciency of fracturing,and cost reduction.At present,the exploration and development of continental shale gas in China is still in an early stage,with high costs and low initial production.It is still necessary to carry out pilot tests of continental shale gas exploration and development to achieve scientifi c and technological breakthroughs,form a resource replacement,and promote the continental shale gas industry to obtain economic benefi ts.