塔里木盆地北部奥陶系海相碳酸盐岩断溶体油藏成因类型及特征再认识

New insights into the genetic types and characteristics of the Ordovician marine fault-karst carbonate reservoirs in the northern Tarim Basin

前人提出的“断溶体”油藏概念,现已成为海相碳酸盐岩油气藏勘探开发的新目标、新类型。但断溶体油藏与传统的风化壳型喀斯特油藏有显著差别,断溶体储集体类型、结构特点也存在差异。研究断溶体溶蚀作用和构造破裂作用的差异性,将断溶体划分为过溶蚀残留型、破碎+强溶蚀型和强破碎+弱溶蚀型3种类型。研究表明不同成因类型的断溶体油藏,其溶蚀程度、缝洞规模、累产油量、地层能量和缝洞间连通性差异明显。过溶蚀残留型油藏的分布受风化壳不整合面及断裂带的纵向溶蚀作用控制。破碎+强溶蚀型及强破碎+弱溶蚀型油藏的形成和分布与不整合面的发育和构造位置关系不大,主要受溶蚀断裂带“破碎+溶蚀程度”控制,在溶蚀断裂带核部发育规模较大的洞穴,向两侧逐步发育裂缝-孔洞型、裂缝型储层。

The previously coined fault-karst reservoirs have become new exploration and exploitation targets and types of marine carbonate hydrocarbon reservoirs.However,these reservoirs are significantly different from conventional weathering-crust karst reservoirs and also show diverse reservoir types and structural characteristics themselves.By delving into the differences in the dissolution and tectonic fracturing of fault-karst reservoirs,we categorize these reservoirs into three types:the over-dissolved residual type,the fractured and highly dissolved type,and the highly fractured and weakly dissolved type.Investigations into these types of fault-karst reservoirs reveal that these reservoirs significantly differ in dissolution intensity,fracture and vug sizes,cumulative oil production,formation energy,and fracture-vug connectivity.Furthermore,the distribution of over-dissolved residual fault-karst reservoirs is influenced by both weathering crust unconformities and the longitudinal dissolution of fault zones.In contrast,the formation and distribution of the remaining two types,manifesting a minimal association with unconformities and tectonic locations,are primarily governed by the fracturing and dissolution intensity of dissolved fault zones.Specifically,large-scale caves occur in the cores of dissolved fault zones,gradually transitioning to fractured-vuggy and fractured reservoirs towards their both sides.