Controls on the productivity in porous tight sandstone gas reservoirs
In this study,two suites of gas reservoirs in Sichuan Basin were taken as objectives to identify controls on the productivity in tight sandstone reservoirs with underdeveloped natural fractures,including the Upper Xujiahe 2 Member in Yuanba area of northern basin and Xujiahe 5 Member in Dongfengchang area in central basin.Their geological characteris-tics,drilling techniques and fracturing stimulation were discussed to ascertain the productivity controls.Results show that(i)vastly enriched in natural gas,both ancient and current structural highs with a great possibility in big output are avail-able for hydrocarbon migration and accumulation.While there exists a poor effect in structural lows;(ii)the better the res-ervoirs'physical properties,the higher the enrichment in the reservoir-forming process,and the stronger the flowing rate in the production process,also implying the thicker the developed reservoirs with high quality,the higher the output;(iii)it is essential to perform the stimulation in such reservoirs with underdeveloped fractures.Especially,to expand fracturing scale may create an obvious stimulation effect in the developed quality reservoirs;(iv)not all of tight sandstone reservoirs are de-veloped everywhere,creating more quality ones encountered in horizontal wells.So,an evidently incremental production can be attained in vertical wells;and(v)reservoir protection shall be stressed because some reservoirs with poor to moder-ate physical properties are contaminated by barite in drilling fluid to further condition the output.In conclusion,for the po-rous tight sandstone gas reservoirs,the productivity is mainly influenced by ancient and current structural highs,growth of quality reservoirs,stimulation scale and well types.What's more,the priority for well deployment shall be set in some su-perimposed zones developed with quality source rocks,positive structures and comparatively quality reservoirs.
Sichuan BasinUpper Triassic Xujiahe gas reservoirsProductivity controlTight sandstone gas reservoirRes-ervoir with underdeveloped fractures
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