建南构造飞仙关组三段高精度层序地层学及南北高点储层差异原因探讨

以岩屑薄片为基础,结合侧井曲线分析资料,按Exxon公司经典层序地层模式,对建南构造南、北高点代表井建45井、建42井进行了层序地层划分,共划分4个沉积层序,均为Ⅱ型层序,层序级别相当于四级。并对南北高点进行了层序地层对比,南高点的鲕滩主要发育在层序1、2、3的高位期,北高点的鲕滩主要发育于层序4的海侵期。研究认为:南、北高点鲕滩储层存在差异,南高点的鲕滩可定义为“高位滩”,而北高点的鲕滩定义为“海侵滩”,后者因缺乏表生溶蚀作用而储集性能差;北高点可形成层状白云岩储层,层状白云岩储层发育于层序3的高位晚期,层位上处于北高点鲕粒滩与泥晶灰岩之间。针对南、北高点的储层分布规律,提出南高点应以滚动扩边,打斜井提高产能为主,北高点应以寻找优质白云岩储层为主。

High-resolution sequence stratigraphy and reservoir differences between the southern and northern culminations in the third member of the Feixianguan Formation in the Jiannan structure,Hubei

Sequence stratigraphic division is conducted on the strata of the Jian-45 and Jian-42 wells at the southern and northern culminations in the Jiannan structure using the Exxon’s classic sequence stratigraphic model.These strata may be divided into four Ⅱ-type fourth-order sequences.A sequence stratigraphic correlation is made for the southern and northern culminations,respectively.The oolitic shoals in the southern culmination were developed in the highstand systems tract of Sequences 1,2 and 3,whereas those at the northern culmination were developed during the transgressive period of Sequences 4.The former may be defined as the "highstand shoals",whereas the latter may be defined as the "transgressive shoals" whose reservoir capability is poor due to the lack of surface solution.The bedded dolostone reservoirs at the northern culmination were developed in the upper highstand systems tract of Sequences 3,and horizontally occur between the oolitic shoals and micritic limestone.In these cases,rolling stepout drilling and deviated drilling are proposed to improve production at the southern culmination,whereas at the northern culmination,high-quality dolostone reservoirs are expected.