准噶尔盆地南缘高泉构造下组合油气成藏主控因素分析及有利区预测

Controlling Factors and Favorable Area Prediction of Cretaceous Qingshuihe Formation in Gaoquan Area of the Southern Junggar Basin

准噶尔盆地深层油气资源丰富,成藏过程复杂,深入认识控藏要素与富集规律具有重要科学及实践意义.以准噶尔盆地南缘高泉构造下组合白垩系清水河组为例,综合利用岩心观察、薄片鉴定、单井相分析、油藏解剖、地层水分析等技术手段,明确了高泉构造清水河组砂体成因、关键控藏要素及有利区带,丰富了复杂构造带沉积-成储-成藏理论认识.分析认为:(1)高泉构造白垩系清水河组砂体为扇三角洲前缘多期水下分流河道砂体叠置而成,砂体储集性能横向变化快,非均质性强.(2)清水河组油气保存条件差异大,高泉构造自燕山期以来为继承性构造,受多期构造运动影响,背斜构造受断裂切割改造严重,在挤压变形强烈的背斜翼部,深浅断层纵向对接,造成背斜构造翼部油气沿断裂调整散失,仅在构造高点富集成藏.(3)清水河组底部砂体物性受沉积期古地貌控制,古地貌相对较高的低凸起,砂体泥质含量低,分选好,物性优;古地貌相对较低的古沟槽沉积区,砂砾岩分选磨圆差,泥质含量高,储集物性差.(4)高泉构造清水河组油气成藏受优质储层及保存条件两大关键要素控制,围绕两大控藏要素,基于三维地震资料,开展古地貌恢复及敏感属性分析,预测高泉构造清水河组优质储层发育区,主要分布于三维工区西南部,呈北西-南东向条带状分布,有利面积约110 km2,为该区深层油气勘探提供有效支撑和借鉴.

Petroleum resources are abundant in deep formation of the foreland thrust belt,the large-scale oil and gas reservoir exploration field.However,due to the large buried depth,low exploration degree and complex reservoir forming mechanism,it also faces great challenges.It is of great scientific and guiding significance to reveal the reservoir control factors and enrichment rules under complex reservoir forming conditions.Taking the southern margin of Junggar Basin as an example,basing on core observation,thin section identification,logging and single well facies analysis,the sand body sedimentary microfacies and reservoirs type and key factors of Qingshuihe Formation in Gaoquan area were clarified.The comprehensive analysis shows follows:(1)The Cretaceous Qingshuihe Formation sand bodies in Gaoquan structure were superposed by multi-stage underwater distributary channel sand bodies in the fan delta front,with fast lateral changes in sand body reservoir performance and strong heterogeneity.(2)The oil and gas reservoir preservation conditions of the Qingshuihe Formation vary greatly.The Gaoquan anticline structure had been an inherited structure since the Yanshanian Period.Affected by multiple tectonic movements,the anticline structure was severely cut and transformed by faults.In the anticline wing with strong compression deformation,deep and shallow faults were vertically connected,causing the oil and gas in the anticline wing to disperse along the fault adjustment,and only enriched and formed reservoirs at the structural highs.(3)The physical properties of the sand bodies at the bottom of the Qingshuihe Formation were controlled by the paleogeomorphology of the sedimentary period.The sand bodies deposited in areas with relatively high ancient landforms have low shale content,good sorting and excellent reservoir physical properties.The gravels deposited in areas with relatively low ancient landforms are poorly sorted and rounded,with high shale content and poor reservoir physical properties.(4)The oil and gas accumulation of Qingshuihe Formation in Gaoquan structure area are controlled by two key factors:high-quality reservoir and preservation conditions.Focusing on the two major reservoir control factors and based on 3D seismic data,ancient landform restoration and sensitive attribute analysis are carried out to predict the high-quality reservoir development area of Qingshuihe Formation in Gaoquan structure,which is mainly distributed in the southwest of the 3D work area,in NW-SE strip distribution,with a favorable area of about 110 square kilometers,it provides effective support and reference for deep oil and gas exploration in this area.