黄骅坳陷页岩型页岩油富集规律及勘探有利区

Enrichment law and favorable exploration area of shale-type shale oil in Huanghua depression

近年勘探实践证实渤海湾盆地黄骅坳陷古近系孔店组二段、沙河街组三段和沙河街组一段主力烃源岩层系发育页岩滞留型页岩油,页岩油富集规律不清、有利层/区不明制约了坳陷页岩油扩展勘探和规模开发。基于黄骅坳陷古近系系统取心、岩石薄片、测井、录井、试油及烃源岩评价、滑溜水常压渗吸对比实验等测试资料系统开展页岩油烃源岩、储集性能、保存条件分析,探讨黄骅坳陷页岩型页岩油富集模式及有利区分布规律。研究认为,适中物源供给、适中总有机碳含量(TOC含量为2%~6%)、适中有机质类型(以Ⅰ型为主、Ⅲ型为辅)、适中热演化成熟度(Ro为0.7%~1.2%)等适中的物源及烃源岩条件,高密度微米—纳米纹层(密度可达15000层/m)、高占比微米—纳米孔缝(孔隙度平均为4.5%)、高滞留可动烃含量(S1含量平均为4.2 mg/g)等适高的储集条件,顶、底板封堵条件优(盖层厚度为50~100 m)、断裂破坏程度弱(水平井靶层距离为450~550 m)等优良的保存条件,是黄骅坳陷古近系页岩型页岩油富集的主控因素。提出了黄骅坳陷古近系“2优1超1匹配”的“中高匹配”页岩油富集规律,分别构建了毫米级有机质—长英质纹层、厘米级有机质—粉砂纹层、毫米级有机质—碳酸盐纹层3类“优势组构相”的页岩油富集模式。提出了研究区页岩型页岩油有利层及有利区的优选标准及定量评价方法,在黄骅坳陷古近系优选出7套Ⅰ类富集层作为首选钻探靶层。研究认识指导有效实现了沧东凹陷页岩油规模开发和歧口凹陷页岩油勘探突破,初步建成了产量10×104t/a的页岩型页岩油开发示范区,实现了在65美元/桶油价下的效益开发,展示了中国东部断陷盆地陆相页岩油良好的勘探开发前景。

The exploration practice in recent years has proved that the retained shale oil is developed in the main source rock series in Member 2 of Kongdian Formation,Member 3 of Shahejie Formation and Member 1 of Shahejie Formation in the Paleogene of Huanghua depression,Bohai Bay Basin.However,in Huanghua depression,the expanded exploration and large-scale development of shale oil are restricted by unclear enrichment laws and favorable layers/areas of shale oil.Based on testing data of the Paleogene of Huanghua depression regarding coring,rock slice,well logging,oil test,source rock evaluation and comparative experiment of slippery water imbibition under atmospheric pressure,this paper systematically analyzes the source rocks,reservoir properties and preservation conditions of shale oil in Huanghua depression,and explores the enrichment modes of shale oil and the distribution laws of favorable areas in Huanghua depression.It is found through the research that the enrichment of the Paleogene shale-type shale oil in Huanghua depression is mainly controlled by the source material supply and source rock conditions such as moderate source material supply,moderate total organic carbon content(TOC content of 2%~6%),moderate organic matter type(dominated by Type I,followed by Type III),and moderate thermal evolution maturity(Roof 0.7%~1.2%);suitable reservoir conditions such as high density of micro-nano laminae(up to 15000 laminae/m),high proportion of micro-nano pores(average porosity of 4.5%),and high content of retained movable hydrocarbons(average S1of 4.2 mg/g);excellent preservation conditions such as ideal roof and floor sealing conditions(caprock thickness of 50~100 m),weak fault damage(distance between faults and the target layers of a horizontal well:450~550 m).The shale oil enrichment law in the Paleogene of Huanghua depression,which features“a matching between medium and high level”that involves good fabric facies,excellent cross-over effect and perfect match between source rock and reservoir has been established,as well as the enrichment modes of shale oil respectively based on three types of dominant fabric facies in the Paleogene(namely the millimeter-grade organic matter-felsic lamina,the centimeter-grade organic matter-siltstone lamina,and the millimeter-grade organic matter-carbonate lamina in Huanghua depression).Additionally,this paper puts forwards the selection criteria and quantitative evaluation method for favorable layers and areas of shale-type shale oil in the study area,and selects seven sets of Type I shale oil layers in the Paleogene of Huanghua depression as the preferred target layers for drilling.By now,under the guidance of relevant theoretical understandings and technical methods,breakthroughs have been made in the large-scale development of shale oil in Cangdong sag and the exploration of shale oil in Qikou sag.Specifically,the shale oil development demonstration area with a production capacity of 10×10~4t/a has been preliminarily completed,and the economically viable development of shale oil at the oil price of 65 dollar/barrel has been achieved,which demonstrates the promising exploration and development prospects of continental shale oil in the faulted basins in eastern China.