Facies And Diagenesis Of Shiniulan Formation In Southeast Area Of Sichuan Basin

The Southeast area of Sichuan basin,with abundant hydrocarbon source,is located in ccumulation zones of petroleum and gas.It is also the key area of hydrocarbon exploration and exploitation in China.The Longmaxi Formation was always the key target of the researching in this region because of it containing a set of deep black shale,which is high-quality hydrocarbon rock.The potential of petroleum and gas in Shiniulan Formation was ignored.While,researchers start to believe the exploration prospect of hydrocarbon in Shiniulan Formation,along with farther exploration in recent years and the often Industrial gsa in the well drilling.There are just residual formation for Longmaxi,Shiniulan?Xiaoheba?and Hanjiadian Formation in the research region because of the effection of the Guangxi tectonic movement in the Silurian.The Shiniulan and Xiaoheba Formations are synchronous different facies.The former is the target formation,which belongs to the carbonate platform deposits on neritic shelf,distributes on the area of southeast Sichuan and the north of Guizhou.The lithologic properties are gray calcareous shale interbedded with Thin layers of limestone and marlstone,there comes nodular limestone and biohermal limestone on local area.In this paper,the third-and fourth-order sequences are divided by outcrop,well drilling and seismology.And then the stratigraphic sequence framework is established.We distinguish the dividing indexes of facies and know the sedimentary facies of target formation integrating outcrop,core observation,well ogging and seismic profiles interpretation.On the basis of sequence stratigraphy and study of seismic facies,we describe sedimentary facies belt distribution of study area,establish depositional model.Combined with rock thin section,casting thin sections,the analysis of single well sedimentary facies,researching diagenetic evolution of reservoir,we reveal control relationship of diagenesis and reservoir property,analyse reservoir pore types,origin,distribution and controlling factors,to uncover the characteristics of porosity evolution rule and physical property change.Finally combining reservoir macroscopic distribution,physical property change,diagenetic evolution,pore structure characteristics research,we can Comprehensively evaluate favorable facies belt and advantageous reservoir distribution area,provide good scientific guidance for the further oil and gas exploration.The main results obtained are mainly as follows:?1?This study according to the outcrop,drilling and seismic data,conjointly cascading key interface for pattern recognition and sequence and maximum flood flooding surfaces characteristics research,etc.,will be divided to two sequences in the study area,respectively SS1?early?and SS2?late?,and further divided into eight level 4 cycles.?2?For the evolution of depositional facies and model on the target formation,we think carbonate tidal flat occurring in northern depression of north rim of middle guizhou uplift after uneven uplift in middle guizhou uplift and the bottom of the sea basin.Continuing to north,there is shallow open platform sedimentary and platform edge facies belt.It is slowly transforming to shelf deposit in southern region.?3?In combination with characteristics of petrology and geochemical study of reservoir,it shows that there experienced relatively simple a series of diagenetic evolution,which damage reservoir.Quality of reservoir compaction,pressure solution and cementation is very strong,causing dense reservoir,small reservoir space and poor permeability.And these two kinds of diagenesis mainly occur before maturity of organic matter.When organic matter decomposes and releases CO₂ and organic acids,rock has become so dense that restricted the improvement of acidic fluid for the quality of reservoir group.