Comparison of basic features and origins of
oolitic shoal reservoirs between carbonate
platform interior and platform margin locations
in the Lower Triassic Feixianguan Formation of
the Sichuan Basin, southwest China |
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Authors: | Tan Xiucheng Zhao Luzi Luo Bing Jiang Xingfu Cao Jian Liu Hong Li Ling Wu Xingbo and Nie Yong |
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Affiliation: | 1. State Key Laboratory of Oil and Gas Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China;School of Resource and Environment, Southwest Petroleum University, Chengdu, Sichuan 610500, China 2. Branch of Exploration Management, PetroChina Southwest Oil and Gas Field Company, Chengdu, Sichuan 610051, China 3. Branch Station in Research Institute of Petroleum Exploration and Development, Post-doctoral Workstation of PetroChina Southwest Oil and Gas Field Company, Chengdu, Sichuan 610051, China 4. Branch of Exploration Industry, PetroChina Southwest Oil and Gas Field Company, Chengdu, Sichuan 610051, China 5. Department of Earth Sciences, Nanjing University, Jiangsu 210093, China 6. School of Resource and Environment, Southwest Petroleum University, Chengdu, Sichuan 610500, China |
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Abstract: | The oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation carbonates in the Sichuan Basin of southwest China are an important target for gas exploration in the basin.Their occurrence,like other cases worldwide,can be divided into two locations in general,i.e.,platform interior and platform margin locations.Their differences of reservoir features and origins,however,have not been investigated comprehensively due to different exploration degrees.This issue is addressed in this paper,to provide basic data and information for the basin's hydrocarbon exploration and for the study of carbonate platform sedimentology and reservoir geology worldwide.We compared the features of these two types of reservoirs in detail,including the depositional and diagenetic features,pore types and petrophysical features.Based on the comparison,the origin of the reservoirs was further discussed.It is shown that the reservoirs in platform interior and platform margin locations differ significantly.The interior carbonates were deposited in moderate to high energy settings and the dominant lithologic type was limestone,which was weakly compacted and intensely cemented and has undergone meteoric dissolution.Pore types include intragranular dissolution and moldic pores,with low porosities(6%) and low permeabilities(0.1 mD).By contrast,the platform margin carbonates were deposited in relatively high energy settings and mainly consisted of dolostones with some limestones.The rocks were strongly compacted but incompletely cemented.As a result,some primary intergranular pores were preserved.Both meteoric solution and burial solution have taken place.There are various types of pore spaces including intergranular and intercrystalline solution pores and residual intergranular pores.This type of reservoir generally has better petrophysical properties(9% porosity and 0.1 mD permeability) and pore-throat structures than the interior reservoirs.These differences were influenced by both primary depositional features and secondary diagenesis.For the interior carbonate reservoirs,early meteoric dissolution,weak compaction and strong cementation are important controlling factors.By contrast,the factors controlling the formation of the margin carbonate reservoirs mainly include dolomitization,preservation of primary pores and burial dissolution. |
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Keywords: | Carbonate platform oolitic shoal reservoir platform margin platform interior Lower
Triassic Feixianguan Formation Sichuan Basin China |
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