7000m以深超深层古老缝洞型碳酸盐岩油气储层形成、评价技术与保存下限

Formation,evaluation technology and preservation lower limit of ultra-deep ancient fracture-cavity carbonate reservoirs below 7000m

随着油气勘探向深层发展,7 000 m以深的超深层成为勘探重点。超深层古老碳酸盐岩储层的形成、保存和预测是关键难题。通过分析中国塔里木盆地奥陶系7 000 m以深已钻井资料,表征超深层碳酸盐岩储层发育特征及形成演化过程,发现高能沉积相带、准同生期暴露岩溶作用和断裂改造等控制了超深层碳酸盐岩储层的形成。通过地震属性提取,发现"串珠"状反射,提出了沿断裂带顺岩溶层钻探的方法,钻井成功率提高到了75%。建立了缝洞体定量雕刻与表征技术,形成了缝洞型油藏油气富集规律与井点优选方法。建立断层与缝洞型碳酸盐岩储层中孔洞的力学模型,开展数值模拟和理论分析,结果表明:随与断层面距离的增加,裂缝发育能力减弱;8 500 m以浅为碳酸盐岩储层优势分布区,8 500~9 200 m为有效分布区,9 200~9 500 m为一般分布区,11 000 m以深大型孔洞逐渐消亡;台盆区超深碳酸盐岩储层中古溶洞顶部形成抛物面型压力拱,阻碍溶洞的完全垮塌,以高跨比为1、矢高为8 m的抛物面型溶洞为例,其完全闭合深度在50 000 m以深。因此,碳酸盐岩洞穴储层勘探深度下限远远超过目前可钻深度。

With the development of oil and gas exploration to deep layers,ultra-deep layers below 7000 m have become the focus of exploration.The formation,preservation and prediction of ultra-deep ancient carbonate res⁃ervoirs are key problems.Based on the analysis of the drilling data below 7000 m of Ordovician in Tarim Ba⁃sin,China,this paper characterizes the development characteristics and formation and evolution process of ultradeep carbonate reservoirs.The formation of ultra-deep carbonate reservoirs is controlled by high-energy deposi⁃tional bodies,penecontemporaneous exposed karstification and the reconstruct of faults.Through seismic attri⁃bute extraction,beads were found and a method of drilling along the fault zone along the karst layer was pro⁃posed.The success rate of drilling was increased to 95%.The quantitative sculpture and characterization tech⁃nology of fracture-cavity has been established,and hydrocarbon accumulation regularity and well point optimiza⁃tion method for fracture-cavity reservoirs have been formed.Mechanical models of vugs in fault and fracture-cav⁃ity carbonate reservoirs are established,and numerical simulation and theoretical analysis are carried out.The re⁃sults show that the distance from fault plane increases,and the fracture development ability decreases.Over 8500 m is the dominant distribution area of carbonate reservoir,8500-9200 m is the effective distribution area,9200-9500 m is the general distribution area,below 11000 m,large vugs are gradually disappearing.Parabolic pressure arches are formed at the top of the paleocave in the ultra-deep carbonate reservoir in the platform basin area to prevent the cave from collapsing completely.Take the parabolic cave with the height-span ratio of 1 and arrow height 8 m as an example,its fully closed depth is over 50000 m.Therefore,the lower limit of explora⁃tion depth for carbonate cave reservoirs far exceeds the current drillable depth.