Characteristics and main controlling factors of dolostone reservoir of the Middle-Lower Ordovician Yingshan Formation in Katak Uplift of Tarim Basin
Wu Shiqiang1, Qian Yixiong1, Li Huili1, Yang Suju2, Sha Xuguang2, Xia Yongtao2, Ma Qingyou2, Zhu Xiuxiang2
1 Research Institute of Exploration & Production，SINOPEC，Beijing 100083 2 Exploration and Development Research Institute，SINOPEC Northwest Company，Urumqi 830011，Xinjiang
Abstract：Dolostones of the Middle-Lower Ordovician Yingshan Formation in Katak Uplift of Tarim Basin are hydrocarbon reservoir rocks of vital importance.Based on detailed petrographic and geochemical investigations，the characteristics and origin of the reservoir have been figured out.Silt-sized limy dolostone and silt-sized dolostone are the two main types of reservoir rocks.Intercrystal pores，intercrystal dissolved pores and acicular pores occupied more than 85％ of the reservoir space.Intracrystal dissolved pores，dissolved vug and other pores are minors.Geological and geochemical analyses suggested that dolostone reservoir was controlled by several factors.Dolomitization produced massive intercrystal pores and provided later dissolution with potential spaces.A large number of intercrystal dissolved pores are formed during the epigenic karstification，the 87Sr/86Sr value of the dolostone was modified during this process and the value decreased with growing depth，at the same time the trace elements concentration of Fe and Mn decreased，the luminescent was getting weak.The epigenic karstification was also indicated by logging responses and dedolomitization.Bitumen impregnation was suggested by the bitumen alongside sytlolites，moderate bright to moderate dark fluorescence can be seen in some intercrystal pores.Burial dissolution was less fabric selective and caused most of the acicular pores，so occurrence of the pores was less relative to the fabric. Some acicular pores were filled by calcite, among which the Fe content was 18.1×10-4 in average, and Mn was 16.5×10-4 in average. Both of the content was less than that of matrix dolomite apparently, which was 617.4×10-4 and 166.8×10-4, and the fluorescence was also darker than matrix dolomite．
Wu Shiqiang,Qian Yixiong,Li Huili et al. Characteristics and main controlling factors of dolostone reservoir of the Middle-Lower Ordovician Yingshan Formation in Katak Uplift of Tarim Basin[J]. JOPC, 2012, 14(2): 209-218.
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