Research on Carbonatite Buried Hill Paleokarst Reservoir of Paleozoic Erathem in Bozhong A Tectonic Belt

The object of this research is the formation of ancient buried hill of Paleozoic in Bozhong A Tectonic Belt. We, combining logging and earthquake data, adopt methods such as identification under thin lens, cathode... [ view full abstract ]

The object of this research is the formation of ancient buried hill of Paleozoic in Bozhong A Tectonic Belt. We, combining logging and earthquake data, adopt methods such as identification under thin lens, cathode luminescence, microelement analysis and fluid inclusion analysis to carry out the research on Carbonatite Buried Hill Paleokarst function and reservoir development characteristics in a deep-going way. The analysis shows that: 1) Buried hill section of Well No. 1 can be divided, from top to bottom, into Lower Ordovician Yeli Formation, Lower Ordovician Liangjiashan Formation and Middle Ordovician Lower Majiagou formation. The sedimentary environment is mainly tidal flat and restricted platform facies; 2) The hole seam of carbonatite reservoir space at the area has been developed, but the secondary pore and cave formed by karst is the main reservoir space; two reservoir sections of buried hill top and inner buried hill are formed along longitudinal direction and the reservoir in dolomite section are relatively developed; 3) The development and preservation of karst reservoir is controlled by supergene karstification and deep burial cementation. The original reservoir space is formed under supergene karstification and tectonic fissures function, but most reservoir spaces is cemented seriously under burial cementation function and the multi-phase cementation is formed; 4) At least three phases of burial cementation occur during area geology historical period, among them the cementation period of Well No. 1 mainly starts from the sediment of Guantao formation; 5) Comparing with Bozhong B structure, Bozhong A structure in late Paleozoic and late Mesozoic are located in relevant-high ancient landform, which results in the current fact that the reserved formation section of Bozhong A structure is located in relative low position and Bozhong B structure is located in the lower slope, and as a result, the karst reservoir of Bozhong B structure developed in Paleozoic erathem is thicker; 6) Comprehensive analysis shows that place around the southeast structural high is favorable distribution area of reservoir.