四川盆地"十三五"以来天然气风险勘探理论技术进展与攻关方向OA

To guide the future deployment of natural gas exploration in the Sichuan Basin,this paper systematically summarized the critical theoretical understandings,technical progress and significant achievements with respect to risk exploration in the basin since the 13th Five-Year Plan began.Based on the exploration practices of PetroChina Southwest Oil&Gasfield Company,the geological conditions for gas accumulation were investigated in four major domains(marine conventional gas,continental tight gas,shale gas,and coal-rock gas),the collaborative innovations in geophysical and engineering technologies were analyzed,and the controls of tectono-sedimentary evolution on large-scale reservoir-controlling geological units were clarified.The following results are obtained.(i)In terms of marine conventional gas,the"four-paleo"accumulation theory(paleo-rift trough,paleo-platform,paleo-oil cracking gas,and paleo-uplift)and the new insights on trough-platform differentiation were deepened,and an innovative model of"three-dimensional hydrocarbon accumulation in traps controlled by faults and lithologies"was established for slope zones,supporting the identification of five new areas such as Penglai,southwestern Sichuan Basin,and northwestern Sichuan Basin,each with reserves exceeding 1 000×108 m3,contributing the addition of proven gas in place(GIP)over 1.27×1012 m3.(ii)In terms of continental tight gas,a strategic shift from lithologic gas reservoirs in uplift areas to inner-source tight gas reservoirs in depression areas was achieved in accordance with the theory of whole petroleum system,with newly added GIP of 1 110×108 m3 in the Triassic Xujiahe Formation,northwestern Sichuan Basin,suggesting a resource potential up to 3.04×1012 m3.(iii)In terms of shale gas,the enrichment model controlled by the trough-uplift spatiotemporal coupling for the Cambrian Qiongzhusi Formation and the"four-high"(high TOC,high brittle mineral,high porosity,and high gas content)quality shale evaluation system for the Permian Wujiaping Formation were established,and two 1.00×1012 m3-scale strata were defined for exploration.(iv)In terms of coal-rock gas,a new"dual"occurrence mechanism for deep Permian Longtan Formation featured with high pressure,high gas saturation and high free gas content was revealed,leading to a novel strategic discovery with the favorable area predicted to be 1.04×104 km2.It is concluded that the continuous growth of natural gas reserves and production in the Sichuan Basin will be primarily secured by enhancing the basic research on large-scale reservoir-controlling geological units,developing high-resolution seismic imaging and subtle trap identification technologies,and improving the adaptability of ultra-deep reservoir stimulation and deep shale gas reservoir fracturing processes.