Natural Gas Reservoir And Pathway System Within Sulige Gas Field Of Ordos Basin

Sulige gas field is the biggest one in China so far, which is lithological gas reservoir in Craton Basin having tense sandstone reservoir, lower formation pressure, lower and variable resource richness. Through the contrast between reservoirs and conduit systems of typical natural gas reservoirs and non natural gas reservoirs, porosity evolution model of natural gas reservoir is built up, space time evolution and mechanism of conduit system are studied and "sweet point"is found among tense sandstone reservoir. The study not only accelerates the progress of exploration and development of Sulige gas field, but also brings about some experiences how to find similar natural gas fields in China. Based on the contrast between lithological features, diagenism, reservoir characteristics of gas-bearing beds and non gas-bearing ones, the difference of their diagenic facies is found: gas-bearing ones are popular in soluble void diagenic facies of coarse-detritus-quartz-sandstone, whereas non gas-bearing ones popular in tense compaction diagenic facies of mud-bearing medium-fine detritus-quartz-sandstone and residual intergranular pore diagenic facies of mud-bearing medium-coarse detritus-quartz-sandstone. Through burial history and temperature evolution history of upper palaeozoic by PRA Basin Modeling system, fluid inclusion analyses and other geochemistry indexes, the diagenetic stage of reservoirs is estimated: most are on the stage of late diagenesis A while some late diagenesis B. Medium-coarse sediments experience different diagenetic evolution pathway from fine ones because of different energy of their water body and their diagenism. With more secondary porosity and residual primary porosity, medium-coarse sediments form gas-bearing beds easily. However, with less residual primary porosity and secondary porosity, fine sediments form non gas-bearing formations. The quality of reservoirs is affected by structural setting, sedimentary facies, and diagenism. Mechanism of secondary porosity formation is studied through fluid-rock interaction simulation: during late diagenesis A, a lot of secondary porosity is formed because filler in reservoirs, such as tuff, feldspar, etc. are solved by organic acid from source rocks. Using high resolution sequence stratigraphy and sedimentary facies analyses, the geological model of conduit systems is built up in Sulige gas field. Types of conduit systems of Sulige gas field includes sandstone bodies, faults, sandstone bodies-faults. Moreover, sandstone bodies are divided into thick-banded,...