准噶尔盆地西北缘扇体形成演化与扇体油气藏勘探

Fans Sedimentation and Exploration Direction of Fan Hydrocarbon Reservoirs in Foreland Thrust Belt of the Northwestern Junggar Basin

准噶尔盆地西北缘广泛发育二叠纪—侏罗纪冲积扇、水下扇、扇三角洲等砾质粗碎屑沉积,其形成演化严格受不同时期活动的同生断裂控制。二叠纪以乌尔禾组扇体最为发育,呈由盆缘向盆地方向逐渐增强的前展式推覆冲断及渐进式扇体迁移响应模式。三叠纪—侏罗纪以百口泉组、克拉玛依组扇体最为发育,呈由盆内向盆缘方向逐渐减弱的退覆式冲断活动及后退式扇体迁移响应模式。已知扇体油气藏主要富集于水下扇扇根及扇中、扇三角洲平原及前缘4个亚相带,及二叠系佳木河组、乌尔禾组、三叠系百口泉组、克拉玛依组、侏罗系八道湾组、头屯河组6个层位。二叠—三叠纪扇体含油层多、规模大、储量丰度高,侏罗纪扇体反之。受断裂、不整合、岩相岩性、物性4种因素控制,扇体主要形成断块、地层不整合及构造岩性油气藏。断阶带及扇根—扇中相带主要发育构造(断块)油藏,为扇体与断层相配置的垂向运聚成藏模式;斜坡区及扇中—扇缘相带主要发育岩性油藏,为扇体与不整合相配置的侧向运聚成藏模式。西北缘扇体成藏条件好,探明程度总体较低,剩余资源潜力大,进而指出了七大有利勘探区块和方向。

The Permian-Jurassic alluvial-fan, subaqua-fan, fan delta were well occured and widely distributed in foreland foldand-thrust belt of the northwest Junggar basin. Synsedimentary faults acting in varied period strictly controlled sedimentation and distribution of various fans from Permian to Jurassic. The fan bodies formed at P1j and P3w have the largest distribution and scale. The Permian was characterized by a model of forward thrusting movement of synsedimentary controlling-fan faults and obvious gradual advance migration response of fan bodies from the margin to the center of Junggar basin. The fan bodies formed at T1b and T2k own the largest distribution and scale from Ttb to J2t stage. Triassic-Jurassic was characterized a model of shrink back thrusting migration of controlling-fan faults and gradual countermarch migration response of fan bodies from the center to the edge of Junggar basin. Known fan petroleum pools mainly enrich in four subfacies belt（root-middle part of underwater fan and alluvial fan, fan delta plain-front）, as well as six horizons（P1j .P2-3w.T1b.T2k .J1b .J2t）. Permian- Triassic fans have plenty of oil-bearing formation, large scale of petroleum pool, higher reserves abundance. But Jurassic fans went in opposite conditions. Fan bodies mainly formed fault block oil reservoir, stratigraphie unconformity oil pools, struetural-lithological oil pools, lithological pools which are concerned with faults and unconformity. Structural pools mainly distribute at scalariform fault belt and root-middle part of fans, lithological pools mainly forms at slope belt and middlefront of fans. The main controlling factors of petroleum pool forming are trusting fault, unoonformity, lithofacies and physical nature of fans. There were the pool-forming pattern of vertical migration-accumulation with the setup of fans and thrusting faults at scalariform fault belt; and the pool-forming pattern of lateral migration- accumulation with the combination of fans and unconformity at slope belt. The pool-forming oondition of fan boides was favorable, its prove extent was lower, and residual resources potential was great. Then the seven beneficial exploration domains and favorable blocks in future are pointed out in foreland thrust belt of the northwest Junggar basin.