断溶体储层类型识别、预测及发育模式探讨——以塔里木盆地塔河十区TH10421单元为例

Discussion on identification,prediction and development pattern of faulted-karst carbonate reservoirs:A case study of TH10421 fracture-cavity unit in block 10 of Tahe oilfield,Tarim Basin

断溶体油藏是近年来塔里木盆地研究的热点和难点,断溶体储层内部的非均质性是制约开发效果的关键。以塔里木盆地塔河十区TH10421单元为例,基于测井及地震高频属性分析,将断溶体内部储集体划分为4类:洞穴型、溶蚀孔洞型、裂缝-孔洞型和裂缝型。其中洞穴型和溶蚀孔洞型是断溶体内部最主要的储集体类型,裂缝-孔洞型及裂缝型是大型洞穴发育的前期阶段和重要沟通条件。研究结果表明,断溶体的储集体从裂缝-孔洞-洞穴的发育过程体现了溶蚀程度由外到内逐渐增强,其中走滑断裂产生的多级裂缝是加速溶蚀的重要因素。断溶体内部每种储集体类型均对应不同的测井、地震响应特征,地震结构属性能够较为清晰的预测断溶体内部不同储集体的分布关系,进一步佐证了断溶体发育模式。该研究对深化断溶体形成过程的理解具有一定推动作用,也为此类油藏开发提供地质借鉴。

Faulted-karst carbonate reservoirs have been a focus of study in the Tahe oilfield in recent years.The heterogeneity of the reservoirs is a key issue that restricts their development.The TH10421 unit in the block 10 of the Tahe oilfield is taken as an example to classify the reservoirs based on logging data and high-frequency seismic attribute analysis.There are four types of reservoir as a result,namely the cavity type,dissolved pore or cavity type,fracture-cavity type,and fracture type,among which the first two are the most common reservoir types,and the last two,still at early stages of evolving into large-scale cavities,serve mainly as connection between reservoirs.The results show that the evolution of reservoirs from fractures to pores and then to cavities indicates a gradual increasing dissolution from outside to inside,and that multi-stage fractures caused by strike-slip faults facilitated the dissolution.Each reservoir type in the faulted-karst carbonates corresponds to specific log and seismic responses.Seismic texture attributes can be used to clearly predict the distribution of different types of reservoirs within,which will in turn further confirm the proposed development model of the reservoirs.The study helps to promote the understanding of the forming process of faulted-karst reservoirs and to provide a geological basis for their future development.