Geological conditions and distributional features of large-scale carbonate reservoirs onshore China
Based on the analysis and observation of well cores and thin sections of more than 300 wells from major exploration plays and intervals in the Tarim, Sichuan and Ordos Basins, and combined with seismic, well logging and testing data, this paper studies and analyses systematically on the types and characteristics of carbonate reservoirs as well as the geologic conditions for their development with large scale. And their distributional features are also summarized. All kinds of marine carbonate reservoirs revealed worldwide are developed onshore China, including 3 types of large-scale effective reservoirs, which are depositional reef-shoal and dolomite reservoirs, epigenetic dissolution-percolation reservoirs and deep burial-hydrothermally altered reservoirs. Besides sedimentary facies, paleoclimate and paleogeomorphy, other factors that have strong influences on the development of deep large-scale reservoirs include interstratal and intrastratal dissolution-percolation, burial dolomitization combined with hydrotherraal processes, etc. Large-scale effective reservoirs in deep carbonate sequence are mostly well distributed along the unconformities and hiatuses in sedimentational sequences, while reservoirs with epigenetic dissolution-percolation origion are well occurred from the paleo-uplift highs to the lower part of slopes. The reservoirs are widely distributed in stratified shape on plane, and presented multi-interval distributional patterns controlled by multi-stage karstification vertically with strong heterogeneity. Burial dolomitization is restricted by primary sedimentary facies, and can form extensive effective reservoirs in deep layers in stripe or stratified shape. Hydrothermally related reservoirs are generally distributed along discordogenic faults, forming effective reservoirs with beadlike distribution in vertical direction and band-fence like distribution on plane, which are not restricted by burial depth.
carbonatesreservoirdevelopment with large scalegeological conditiondistribution featuredeep sectionTarim BasinSichuan BasinOrdos Basin