Gas accumulation conditions and key technologies for exploration & development of Sulige gasfield

Up to now, the Sulige area in Ordos Basin has the favorable exploration area of 55 × 103 km2, the total reserve of natural gas of nearly 6 × 1012 m3 and the proven reserve (including basic proven reserve) of 4.77 × 1012 m3, where the annual production of natural gas reaches 23 × 109 m3, and the Sulige gasfield is the largest onshore natural gas field in China. The pay zone of the Sulige gasfield mainly is Member 8 of Shihezi Formation and Member 1 of Shanxi Formation of Permian which belong to the typical tight sandstone gas reservoir. The coal measure strata in Carboniferous Benxi Formation, Permian Taiyuan Formation and Shanxi Formation provide abundant gas sources for the Gulige gas reservoirs. An open-flow sedimentary model of lacustrine delta is developed, the gentle bottom, sand supply from multi-source, strong hydrodynamic force and multi-period superposition control the distribution of large-area reservoir sand body. Lithology of the reservoir is the sandstone of the fluvial-delta facies, the physical property is poor and the heterogeneity is strong, the average porosity ranges from 4% to 12% and the average permeability varies from 0.01 to 1 mD. The gas reservoir is characterized by wide hydrocarbon generation, pervasive hydrocarbon charging, short-range migration and massive accumulation. The pressure coefficient of the gas reservoir ranges from 0.62 to 0.90, indicating the low-pressure gas reservoir, and the single-well yield is low. Full digital seismic technique in the desert area, non-longitudinal seismic technique in the loess plateau, accurate logging evaluation technique, tight sand reservoir stimulation technology and horizontal well development technology are key technologies for exploration and development of Sulige gasfield.