塔里木盆地库车坳陷克拉苏西部油气相态特征及控制因素

The phase characteristics and controlling factors of oil and gas in the west of Kelasu structural belt in Kuqa Depression,Tarim Basin

塔里木盆地库车坳陷克拉苏西部博孜—大北地区油气勘探持续获得突破,但油气组成、物性与油气藏类型复杂,存在油气相态与物性分布规律不清、油气相态主要控制因素不明确等问题。系统收集了研究区75口生产井烃类流体数据,分析了凝析油的地球化学特征,油气物性参数(密度、黏度、胶质含量、沥青质含量、干燥系数及生产气油比)及其变化规律,根据干燥系数和气油比划分了油气藏类型,恢复了地质条件下的油气相态特征与赋存状态,探讨了相态分布主控地质因素。结果表明:研究区烃类流体总体表现出“东西分段,南北分带”的特征,黏度密度等物性参数整体呈现出由西向东逐渐升高的趋势。油气赋存状态纵向上由深到浅表现为从液相到凝析气相,再到凝析气(湿气)相,最后到气相。油气类型整体上呈环带状分布,挥发性油藏、凝析气藏与湿气藏受侏罗系恰克马克组烃源岩成熟度控制,干气气藏的分布不仅受侏罗系烃源岩成熟度的控制,还受高—过成熟的三叠系烃源岩的共同影响。研究为准确认识克拉苏西部博孜—大北地区油气相态与物性分布规律、油气相态主控因素及未来油气勘探开发部署提供有力的理论支撑。

The explorational breakthroughs have consistently revealed a huge new oil and gas production area in the Bozi-Dabei regions within the western Kelasu structural belt,Kuqa Depression,Tarim Basin.However,oil and gas compositions,physical properties,and oil and gas reservoir types are complex.There are unclear oil and gas phase states and physical property distribution rules,and the main controlling factors of oil and gas phase states are not clear.In this study,75 production-well data were systematically collected for statistical analysis and phase simulation,including hydrocarbon compositions and physical parameters of oil and gas production(e.g.,density,viscosity,colloidal content,asphaltene content,dryness coefficient,production gas-oil ratio).Oil and gas reservoirs were divided into four types of volatile oil reservoirs,condensate gas reservoirs,wet gas reservoirs and dry gas reservoirs according to the dryness coefficient and gas-oil ratio,and then the phase characteristics and occurrence of oil and gas were reconstructed under geological conditions to reveal the main controlling geological factors of phase distribution.The results indicate that the hydrocarbon fluids are generally characterized by the distribution of block-divided from east to west and belt-divided from north to south in the study area.The physical parameters(e.g.,density,viscosity etc.)show a gradual increasing trend from west to east.The occurrence of oil and gas transforms from liquid phase to condensate phase,condensate(wet gas)phase and dry gas phase from deep to shallow reservoirs.Four types of oil and gas are located in circle-curved distribution caused by the maturity differences of the Jurassic Qiakemake source rocks.The distribution of target strata controls the distribution of volatile oil reservoirs,condensate gas reservoirs and wet gas reservoirs.The distribution of dry gas reservoirs is attributed to the combined contribution of mature Jurassic and high-over mature Triassic source rocks.This study has successfully confirmed the distribution of oil and gas phases and physical properties,exploring the main controlling factors for the complexity of oil and gas phases in the Bozi-Dabei regions,which can provide theory-supported helps for the further oil and gas exploration and development in the Kuqa Depression.