关键词: 川西拗陷, 侏罗系河道, 致密砂岩气藏, 压裂, 提高采收率

Abstract: The characters of tight sandstone gas reservoir types in the Western Sichuan Depression were complex, such as complicated channel sand stacking, unstable the sand body distribution, low reserve taste, complex gas-water relationship, low natural productivity, poor stable production capacity, and low recoverable reserves in a single well. In order to achieve continuous production increase and stable production of gas reservoirs, based on the reprocessing and interpretation of old seismic data, a complete geophysical and logging fine evaluation technology system was established, which achieved fine characterization of channel sandstone, accurate reservoir prediction and water saturation and quantitative evaluation. Aiming to increase production, we selected double geological and engineering sweet spots and formed a mixed well pattern plus large-scale multi-stage and multi-cluster volume fracturing reservoir stimulation technology system, of which the type was the combination of linear, "Y" "X" "V" etc on the plane, and "multiple wells in one field and multiple layers in one well" with well type group optimization in vertical direction. The construction displacement was increased from 5$\sim$8 m$^3$/min to 16$\sim$18 m$^3$/min, and the sand addition intensity was increased from 0.4$\sim$0.7 t/m to 4.0$\sim$4.5 t/m, the number of fractures increased from 20$\sim$30 clusters to 50$\sim$80 clusters, and the single-well productivity increased from 5.07$\times$10$^4$ m$^3$/d to 15.64$\times$10$^4$ m$^3$/d. Taking seismic-eology-modeling-mathematical modeling-engineering-economic integration as means, the origin and scale of remaining gas were found out, and measures such as infill adjustment, layer transfer, sidetracking, repeated reconstruction and process maintenance were put forward to improve the gas reservoir recovery rate. It has achieved continuous and stable production of more than 2 billion cubic meters of tight sandston gas reservoirs in western Sichuan for 18 years. With the popularization and application of these technologies, the Southwest Oil and Gas Company$'$s annual production of tight natural gas is expected to remain above 3 billion cubic meters during the "14th Five-Year Plan" period, and the production will continue to be stable.

Key words: Western Sichuan Depression, Jurassic channel, tight sandstone gas reservoir, fracturing, EOR