Distinct sedimentary environments and their influences on carbonate reservoir evolution of the Lianglitag Formation in the Tarim Basin,Northwest China  

作　　者：LIU JiaQing LI Zhong HUANG JunCou YANG Liu 

机构地区：[1]Institute of Geology and Geophysics, Chinese Academy of Sciences, Be ijing 100029, China [2]State Intellectual Property Office of China, Beijing 100088, China

出　　处：《Science China Earth Sciences》2012年第10期1641-1655,共15页中国科学（地球科学英文版）

基　　金：supported by National Major Project of China (Grant No. 2011ZX05008-003);National Natural Science Foundation of China (Grant No. 41172096)

摘　　要：The Upper Ordovician Lianglitag Formation carbonate rocks are important oil and gas reservoirs in the Tarim Basin, Northwest China, with obviously distinct reservoir properties among different oilfields. As a case area of the above carbonate reser- voirs correlation, Tahe and Tazhong oilfields are chosen for the study through an integrated analysis of biostratigraphic isoch- ronous framework, cores, thin sections, logs, and strontium isotopes. The research shows that the two areas were respectively attributed to different carbonate platforms during the Lianglitag Formation depositional phase. For the Lianglitag Formation, five fourth-order sequences may be divided in Tazhong, whereas only four fourth-order sequences are preserved in Tahe that correspond to the lower ones observed in Tazhong. The Lianglitag Formation carbonate platform in Tahe was characterized by ramp and/or weak rimmed types, with low depositional rates （37 ktm/a）, higher whole-rock clastic contents, and higher 878r/86Sr isotope ratios of carbonate matrix, showing relatively deep-water environment and evident terrigenous input for car- bonate deposition. However, a strongly rimmed carbonate platform was developed in Tazhong, with high depositional rates of 250 p.m/a and less whole-rock clastic contents, indicating a high-energy depositional environment. Because of the sedimentary environment differences mentioned above, less high-energy facies but relatively intense syndepositional （early diagenetic） sea-water cementation of carbonates were developed in Tahe, and ubiquitous high-energy reef and shoal facies, with a frequent exposure to subaerial, and weak syndepositional sea-water cementation of carbonates in Tazhong. Therefore, fewer primary pores occurred in the Lianglitag Formation carbonate rocks of Tahe, whereas more primary pores were preserved in the same lithostratigraphic unit of the Tazhong （No. 1 fault zone）. Available high-energy reef-shoal facies and early diagenesis, with more primary pores preserved, provided a key matThe Upper Ordovician Lianglitag Formation carbonate rocks are important oil and gas reservoirs in the Tarim Basin,Northwest China,with obviously distinct reservoir properties among different oilfields.As a case area of the above carbonate reservoirs correlation,Tahe and Tazhong oilfields are chosen for the study through an integrated analysis of biostratigraphic isochronous framework,cores,thin sections,logs,and strontium isotopes.The research shows that the two areas were respectively attributed to different carbonate platforms during the Lianglitag Formation depositional phase.For the Lianglitag Formation,five fourth-order sequences may be divided in Tazhong,whereas only four fourth-order sequences are preserved in Tahe that correspond to the lower ones observed in Tazhong.The Lianglitag Formation carbonate platform in Tahe was characterized by ramp and/or weak rimmed types,with low depositional rates(37 μm/a),higher whole-rock clastic contents,and higher 87 Sr/86 Sr isotope ratios of carbonate matrix,showing relatively deep-water environment and evident terrigenous input for carbonate deposition.However,a strongly rimmed carbonate platform was developed in Tazhong,with high depositional rates of 250 m/a and less whole-rock clastic contents,indicating a high-energy depositional environment.Because of the sedimentary environment differences mentioned above,less high-energy facies but relatively intense syndepositional(early diagenetic) sea-water cementation of carbonates were developed in Tahe,and ubiquitous high-energy reef and shoal facies,with a frequent exposure to subaerial,and weak syndepositional sea-water cementation of carbonates in Tazhong.Therefore,fewer primary pores occurred in the Lianglitag Formation carbonate rocks of Tahe,whereas more primary pores were preserved in the same lithostratigraphic unit of the Tazhong(No.1 fault zone).Available high-energy reef-shoal facies and early diagenesis,with more primary pores preserved,provided a key material basis for the Lianglitag Formation carbonate res

关 键 词：sedimentary environment carbonate platform Lianglitag Formation Tahe Oilfield Tazhong Oilfield 

分 类 号：P618.130.2[天文地球—矿床学] P512.2[天文地球—地质学]