四川盆地龙岗地区雷四上标³亚段储层特征及古岩溶作用对其影响
Reservoir Characteristics and the Influence of Paleokarstification in T₂I₄³ in Longgang Area, Sichuan Basin

雷四³亚段作为雷口坡组主要含油气层段之一，一直是近年的研究重点和热点。本文以四川盆地龙岗地区雷四3亚段为研究对象，通过分析岩石学和地球化学特征，探讨其储层特征以及古岩溶改造作用的影响。结果表明：龙岗地区雷四³亚段主要发育砂屑白云岩、鲕粒白云岩、粉晶白云岩和岩溶角砾岩四种储集岩，储集性能以砂屑白云岩为最好。储集空间类型以粒间溶孔为主，其次为粒内溶孔、晶间溶孔，渗流空间主要为裂缝，总体上储层表现为低孔、低渗的特征。此外，在龙岗地区雷四³亚段中共识别出同生期岩溶作用、表生期岩溶作用、埋藏期岩溶作用三种类型的古岩溶作用。其中，表生期岩溶作用是储层形成的基础，控制着早期储层的形成与分布；同生期岩溶作用是储层形成的关键，不仅改善了原有孔隙的储集性能，更为油气运移提供了更多的有效通道；埋藏岩溶作用是储层进一步优化改造不可忽视的因素。
As one of the main oil-bearing stratum in The Leikoupo Formation, the T₂I₄³ has been the re-search focus and hotspot in recent years. Based on the analysis of petrological and geochemical characteristics, this paper discusses the reservoir characteristics and the influence of paleokarstification in T₂I₄³ in Longgang area. The results show that Arenite dolomite, oolitic dolomite, silty dolomite and karstic breccia are mainly developed in T₂I₄³of Longgang area. Arenite dolomite has the best reservoir property. The main storage space is intergranular dissolved pore, secondly is intragranular dissolved pore and intercrystal dissolved pore. The major influent space is fracture. Generally the reservoir is characterized by low pore and low permeability. In addition, there are three types of palaeokarstification in the research area: syndepositional karstification, epigenic karstification and buried karstification. syndepositional palaeokarstification is the foundation of reservoir formation and controls the formation and distribution of reservoirs in early stage. Epigenic palaeokarstification is the key to reservoir formation, which not only improves the storage performance of previous pores, but also provides more effective channels for oil and gas migration. Buried palaeokarstification is considered as the key factor for further optimization and reconstruction of reservoir.