Take the Cambrian Xiaoerblak Formation in the Keping(Kalpin) outcrop area as an example, a 28 km reservoir scale geological model was built based on description of 7 profiles, observation of more than 1000 thin sectio...Take the Cambrian Xiaoerblak Formation in the Keping(Kalpin) outcrop area as an example, a 28 km reservoir scale geological model was built based on description of 7 profiles, observation of more than 1000 thin sections, petrophysical analysis of 556 samples and many geochemical tests. The Xiaoerblak Formation, 158–178 m thick, is divided into three members and 5 submembers, and is composed of laminated microbialite dolomite(LMD), thrombolite dolomite(TD), foamy-stromatolite dolomite(FSD), oncolite dolomite(OD), grain dolomite(GD)/crystalline dolomite with grain ghost and micritic dolomite(MD)/argillaceous dolomite. The petrology features show that its sediment sequence is micro-organism layer – microbial mound/shoal – tidal flat in carbonate ramp background from bottom up. The reservoir has 5 types of pores, namely, framework pore, dissolved vug, intergranular and intragranular dissolved pore and intercrystalline dissolved pore, as main reservoir space. It is found that the development of pore has high lithofacies selectivity, FSD has the highest average porosity, TD, OD and GD come second. The reservoir is pore-vug reservoir with medium-high porosity and medium-low permeability. The dolomite of Xiaoerblak Formation was formed in para-syngenetic to early diagenetic stage through dolomitization caused by seawater. The reservoir development is jointly controlled by sedimentary facies, micro-organism type, high frequency sequence interface and early dolomitization. The classⅠand Ⅱ reservoirs, with an average thickness of 41.2 m and average reservoir-stratum ratio of about 25.6%, have significant potential. It is predicted that the microbial mounds and shoals in the middle ramp around the ancient uplift are the favorable zones for reservoir development.展开更多
A great breakthrough has been made on oil-gas exploration of the Middle Devonian Guanwushan Formation in Northwest Sichuan Basin.The further exploration shows that the dolomite reservoir is complicated with insufficie...A great breakthrough has been made on oil-gas exploration of the Middle Devonian Guanwushan Formation in Northwest Sichuan Basin.The further exploration shows that the dolomite reservoir is complicated with insufficient investigation.Taking the Middle Devonian Guanwushan Formation as an example,systematic study has been carried out on its reservoir character,mechanism and genesis of dolostone.The field and core data suggest that reservoir types of Guanwushan Formation consist of crystalline dolomite,breccia dolomite and reef dolomite,and reservoir space is characterized by intercrystal(dissolution)pores,residual pores among breccias,intragranular dissolution pores,pockets as well as fractures.Besides,pore structure is of good configuration,showing medium-low porosity and moderate permeability,with average porosity and permeability of 2.23%and 0.44mD respectively,which suggesting fracture-pore and fracture-cavity reservoir.Combined with the previous research,it is suggested that the reservoir of Guanwushan Formation was controlled by facies,dolomitization and two-step karstification,with reef-shoal facies being material base for reservoir development,early dolomitization being key factor for reservoir space preservation,polyphase karstification being foundation for reservoir development and tectogenesis finally finalizing the reservoir.展开更多
基金Supported by the China National Science and Technology Major Project of(2016ZX05004-002)Petro China Science and Technology Major Project(2019B-0405 and 2018A-0103)
文摘Take the Cambrian Xiaoerblak Formation in the Keping(Kalpin) outcrop area as an example, a 28 km reservoir scale geological model was built based on description of 7 profiles, observation of more than 1000 thin sections, petrophysical analysis of 556 samples and many geochemical tests. The Xiaoerblak Formation, 158–178 m thick, is divided into three members and 5 submembers, and is composed of laminated microbialite dolomite(LMD), thrombolite dolomite(TD), foamy-stromatolite dolomite(FSD), oncolite dolomite(OD), grain dolomite(GD)/crystalline dolomite with grain ghost and micritic dolomite(MD)/argillaceous dolomite. The petrology features show that its sediment sequence is micro-organism layer – microbial mound/shoal – tidal flat in carbonate ramp background from bottom up. The reservoir has 5 types of pores, namely, framework pore, dissolved vug, intergranular and intragranular dissolved pore and intercrystalline dissolved pore, as main reservoir space. It is found that the development of pore has high lithofacies selectivity, FSD has the highest average porosity, TD, OD and GD come second. The reservoir is pore-vug reservoir with medium-high porosity and medium-low permeability. The dolomite of Xiaoerblak Formation was formed in para-syngenetic to early diagenetic stage through dolomitization caused by seawater. The reservoir development is jointly controlled by sedimentary facies, micro-organism type, high frequency sequence interface and early dolomitization. The classⅠand Ⅱ reservoirs, with an average thickness of 41.2 m and average reservoir-stratum ratio of about 25.6%, have significant potential. It is predicted that the microbial mounds and shoals in the middle ramp around the ancient uplift are the favorable zones for reservoir development.
基金We thank Dr.Sicong Luo,Feifan Lu and Chengpeng Su for their constructive comments.We thank Dr.Hao Tang and Cheng Huang for their help in filed work.This research was supported by National Science and technology major project(2016ZX05004002-001).
文摘A great breakthrough has been made on oil-gas exploration of the Middle Devonian Guanwushan Formation in Northwest Sichuan Basin.The further exploration shows that the dolomite reservoir is complicated with insufficient investigation.Taking the Middle Devonian Guanwushan Formation as an example,systematic study has been carried out on its reservoir character,mechanism and genesis of dolostone.The field and core data suggest that reservoir types of Guanwushan Formation consist of crystalline dolomite,breccia dolomite and reef dolomite,and reservoir space is characterized by intercrystal(dissolution)pores,residual pores among breccias,intragranular dissolution pores,pockets as well as fractures.Besides,pore structure is of good configuration,showing medium-low porosity and moderate permeability,with average porosity and permeability of 2.23%and 0.44mD respectively,which suggesting fracture-pore and fracture-cavity reservoir.Combined with the previous research,it is suggested that the reservoir of Guanwushan Formation was controlled by facies,dolomitization and two-step karstification,with reef-shoal facies being material base for reservoir development,early dolomitization being key factor for reservoir space preservation,polyphase karstification being foundation for reservoir development and tectogenesis finally finalizing the reservoir.
