Abstract: Hydrocarbon exploration in ultra-deep carbonate reservoirs within Shunbei area has progressed into secondary fault zones situated between major strike-slip faults. These zones exhibit significant heterogeneity in hydrocarbon enrichment, as their accumulation characteristics, reservoir-forming conditions, and primary controlling factors differ markedly from those of major strike-slip fault zones. Consequently, it is imperative to investigate the hydrocarbon accumulation and dominant enrichment factors within these secondary fault zones. Integrating geochemical testing, three-dimensional seismic data, and drilling records, this study employs grey relational analysis coupled with the entropy weight method, complemented by typical reservoir analysis, to delineate the accumulation characteristics and classify migration-accumulation types. Furthermore, the accumulation conditions in these secondary fault zones are quantitatively evaluated, unveiling the underlying patterns and variations of hydrocarbon enrichment. The research results show as follows. (1) The hydrocarbon genesis and evolution characteristics of reservoirs in secondary fault zones between major strike-slip faults are similar to those in adjacent major strike-slip faults zones. However, these reservoirs exhibit higher formation pressure coefficients and are classified as abnormally high-pressure condensate gas reservoirs. The type, thermal maturity, and thickness distribution of source rocks govern the formation processes, types, and physical properties of the condensate gas reservoirs in the study area. (2) Three categories encompassing four distinct migration-accumulation types are identified within the secondary fault zones between major strike-slip faults, i.e., Type A (direct source supply and vertical migration), Type B₁ (displaced penetrating indirect source supply and composite vertical-lateral migration), Type B₂ (segmented-stepwise indirect source supply and composite vertical-lateral migration), and Type C (adjacent major strike-slip fault source supply and lateral migration). Significant disparities exist in the hydrocarbon enrichment capacity among these different types, following the hierarchy of Type A>Type B₁>Type B₂>Type C. (3) The differential configuration of fundamental evaluation parameters such as source connectivity, transport capacity, and reservoir quality determines the degree of hydrocarbon enrichment, which exhibits a positive correlation with the enrichment coefficient (the coefficient of determination is 0.85). The contribution of main controlling factors to hydrocarbon accumulation and enrichment follows a descending order from deformation intensity of the gypsum-salt layer, source connectivity, reservoir quality, to thickness of the gypsum-salt layer. Notably, the deformation intensity of the gypsum-salt layer is a crucial factor constraining the degree of hydrocarbon enrichment within secondary fault zones between major strike-slip faults.

Key words: secondary fault, accumulation characteristics, main controlling factors for enrichment, quantitative evaluation, ultra-deep carbonate rocks, Shunbei area, Tarim Basin

摘要： 顺北地区超深层碳酸盐岩油气勘探已进入主干走滑断裂之间的次级断裂发育区,其油气富集程度差异大,成藏特征、成藏条件和富集主控因素与主干走滑断裂带的油气藏具有明显的区别,因此亟需开展主干走滑断裂之间次级断裂区的油气成藏和富集主控因素研究。基于地球化学测试、三维地震和钻井资料,运用灰色关联法和熵权法,结合典型油气藏剖析,明确了主干走滑断裂之间次级断裂区的成藏特征与油气运聚类型,定量评价了主干走滑断裂之间次级断裂区的油气成藏条件,揭示了其油气富集规律与差异性。研究结果表明:①主干走滑断裂之间次级断裂区油气藏的油气成因和演化特征与相邻主干走滑断裂带的油气藏相似,但油气藏的地层压力系数较高,为异常高压凝析油气藏。烃源岩的类型、热演化程度与厚度分布控制了研究区凝析气藏的形成过程、类型及物性。②主干走滑断裂之间次级断裂区的油气藏存在3类4种油气运聚类型,即A型(直接通源+垂向输导型)、B₁型(错位贯通式 间接通源+垂向-侧向复合输导型)、B₂型(分段阶梯式间接通源+垂向-侧向复合输导型)和C型(相邻主干走滑断裂通源+ 侧向输导型),不同运聚类型的油气富集能力存在显著差异,油气富集能力依次表现为A型＞B₁型＞B₂型＞C型。③通源性、输导性和储集性基础评价参数的差异配置决定了油气富集程度,且与油气富集系数呈正相关,相关性判定系数可达0.85,油气成藏与富集主控因素的贡献度从大到小依次为膏盐岩层变形强度、通源性、储集性和膏盐岩层厚度,其中,膏盐岩层变形强度是制约主干走滑断裂之间次级断裂区油气富集程度的重要因素。

关键词: 次级断裂, 成藏特征, 富集主控因素, 定量评价, 超深层碳酸盐岩, 顺北地区, 塔里木盆地