The Development,Distribution and Constraints of Fractured Reservoir in Ordovician Lianglitage Formation,Central Tarim Basin
The Tarim Basin undergoes multiphase tectonic deformations,superimposition of multi-type basins and is characterized with the complicated geologic structure.Now,it has made substantial progress in oil and gas explorations of carbonate formations in Tazhong uplift.But it is still impercipient in the distribution,evolution and their controls of potential reservoir facies.The major problem is that the research on fracture,distribution of cave and control factors of carbonate formations is not enough constraining the knowledge of oil and gas distribution.A research on the distribution of the fracture of Lianglitage carbonate formation was made based on a lot of rock cores,conventional logs and the FMI analysis,using the seismic sedimentology and the sedimentology theories and this makes some contribution:(1)The identification of types and the analysis of genesis of the development of fractures on Lianglitage carbonate formation of up Ordovician in Tazhong uplift.There are a lot of structural fractures and nonstructural fractures.The major are structural fractures,the nonstructural fractures develop more.The major types are suture,diagenetic fissure and weathering fracture.(2)The distribution,major control factors and the occurrence of fractures.It is rock selective to the development of fractures.The activity of fractures development becomes more obvious with increased rock brittleness.The development of fractures relates to the size of rock grains.Under the same conditions,the activity of fractures development becomes more obvious with increased rock grain sizes.The occurrence and distribution of structural fractures relate to the development and nature of major fracture belts.(3)The research on the nature of the gouge filling the rock fractures of the Tazhong core wells and the mutual crosscutting relationship.Combining with analyzing the fluid inclusion composition containing the calcite,the fluorite,there are three phase developments of fractures,the fractures strike northwest,northeast and east nearly.(4)The analysis of the relevance of fractures to Karst collapse and the law of fracture development.Research has revealed that Karst collapse has the relationship with the fracture,Karst collapse is well developed where the fracture is also well developed.Karst collapse is positively correlated to the fracture.(5)The main reservoirs are explained and has established the evolvement model of carbonate pore,fracture and cave complexes.It indicates the main prospective regions for oil and gas exploration which is nearby the main fracture belt where the fracture and cave are well developed.