波斯湾盆地Arab组—Hith组成藏组合地质特征及油气成藏规律

Geological Characteristics and Hydrocarbon Accumulation of Arab-Hith Play in Persian Gulf Basin

Arab组—Hith组成藏组合为波斯湾盆地重要的成藏组合之一,侏罗系Arab组碳酸盐岩储集层和Hith组层间硬石膏是成藏组合的基本储盖要素。侏罗系Tuwaiq Mountain组、Hanifa组和Diyab组烃源岩为该成藏组合提供了绝大部分的烃类,烃源岩有机质含量高,在始新世中晚期大面积成熟生油,此时阿尔卑斯构造运动Ⅰ幕已形成众多圈闭,油气生成之后即可直接运移至圈闭中。Arab组储集层分布面积广,以颗粒灰岩为主,成岩阶段早期原生孔隙破坏少,后期普遍经受白云岩化和淋滤作用,储集层物性优越。Hith组硬石膏厚度大,分布面积广,遭受断层的破坏程度较弱,油气很少能穿越它进入上部储集层,仅在相变尖灭带或大型断裂处造成油气垂向逸散。由于侏罗系烃源岩生成的油气大多属近源成藏,油气侧向运移的距离短,最有潜力的区域为侏罗系台内盆地分布区,Arab组储集层的油气丰度主要取决于Hith组盖层的封盖能力。

Arab-Hith play is one of the most important plays in Persian Gulf basin,in which the Jurassic Arab carbonate reservoir and Hith anhydrite constitute its basic reservoir-cap rock combination.Most of the hydrocarbons in it are provided by the source rocks of Jurassic Tuwaiq Mountain formation,Hanifa formation and Diyab formation.These source rocks with high TOC and very good oil generation potentials have entered into oil windows during the Middle-Late Eocene in large scale,while many traps had already been formed at Episode Ⅰ of Alpine orogeny.So the generated oil and gas could be charged or migrated directly into the traps.Arab reservoir is characterized by wide distribution,grain limestone and seldom destruction of primary porosity during the early diagenesis,followed by widespread dolomitization and leaching during the late diagenesis,witch allowed it to have superior petrophysical property.Hith formation is characterized by thick anhydrite,broad distribution and weak damage by faulting,which allowed the hydrocarbons hardly to be migrated through it toward the upper reservoirs.The petroleum loss may only occur in phase change/pinch-out belt or near large-scale faults.Most of the hydrocarbons generated from Jurassic source rocks in this play were proximal accumulation and the lateral migrations were short in distance,so the most potential areas should range around the Jurassic intraplatform basins,while Arab reservoir＇s hydrocarbon abundance depend on the sealing ability of Hith cap rock.