Characteristics And Distribution Of Ordovician Carbonate Reservoirs In The East Part Of Tazhong Ⅰ Gas Field

The Ordovician in the Tazhong area experienced sedimentation in the geological history process.Combined with the transformation of the late tectonic movement and paleokarst,this area has a good exploration prospect.The paper takes the Ordovician reservoir in the east of the Tazhong I gas field in the Tarim Basin as the research object,including the Tazhong 62,the 82 and the Tazhong 83 wells,etc.,for petrology and carbonate reservoir geology.Under the guidance of professional disciplines,logging,logging,and seismic techniques were used to describe the geological characteristics of reservoirs in the study area,and the distribution of the reservoirs was summarized.Through the analysis of regional exploration status,the study area can be divided into three sets of storage and cover combinations from bottom to top,and is divided into three sets of oil and gas combinations,Liangyi sub-section + Liang’er sub-section,Liangsan sub-section and Liangwu sub-section + Yingshan.Upper part of the group.The boundary between the first and the third gas group is clear,the difference in lithofacies is obvious,and the lateral contrast is good.Based on the analysis of regional depositional background,a comprehensive analysis of lithologic features and logging curves was performed.The principles and methods of stratigraphy were applied to reveal that the Lianglitage formation in the study area was characterized by the deposition of reef-flat complexes,and the lithology was mainly Biological limestone and granulite limestone.Tazhong 62 Block is located at the main part of the reef beach body,and the longitudinal combination of sedimentary facies is dominated by the reef and beach;the longitudinal combination of sedimentary facies of Tazhong 82 Block is dominated by stony mound.The lower part of the Lianglitage formation in the Tazhong 83 block and the upper part of the Yingshan Formation are semi-confined sea-basis facies and mesa-facies beach facies.The sedimentary microfacies consist mainly of stucco mounds and grain-bearing tidal flats.The lithology is dominated by muddy sand swarf.Limestone,cryptophytic muddy limestone.Combined with logging interpretation results,core description and analysis tests show that the first reservoir rock in the study area is dominated by granular limestone;the third set of reservoir rock is dominated by bright grained limestone.The type of reservoir is mainly crack-hole type,followed by hole-crack type.The first set of reservoirs are low porosity and low permeability reservoirs.The second reservoir is a mesoporous low-permeability reservoir.The comprehensive reservoir evaluation results show that the overall reservoir is dominated by Type Ⅱ and Ⅲ,and there are few Type Ⅰ reservoirs.Based on the analysis of reservoir diagenesis and the main controlling factors of reservoirs,a reservoir development model was established.It was proposed that the development of reservoirs in the study area was controlled by various factors,among which sedimentary facies were the basis for reservoir development and later experienced karstification.The transformation of tectonic functions has transformed the physical properties of the reservoir.The single well profile and reservoir development characteristics,the study of reservoir lateral variation,analysis and prediction of reservoir development and distribution,comprehensive evaluation and prediction of high-quality reservoir distribution and favorable exploration direction,for the next exploration of the area is of great significance.