伊拉克AD油田上白垩统Kh2段生物扰动与储层非均质性

AD油田位于伊拉克中南部，上白垩统Khasib组是其重要的含油层系。Kh2段是Khasib组的主力产层，发育大量生物扰动构造，强烈的储层非均质性制约了油田的注水开发进程。为明确生物扰动与Kh2段储层非均质性的相关性及成因联系，基于岩心、显微薄片观察和阴极发光、点渗透率测试，通过岩相学、遗迹学及储层地质学研究方法，开展遗迹学特征与非均质性特征、类型及成因模式研究。结果表明：Kh2段主要发育Thalassinoides?Rhizocorallium、Ophiomorpha、Thalassinoides?Palaeophycus、Thalassinoides?Rhizocorallium?Planolites 4类遗迹组构，分别对应中缓坡固底底质颗粒滩、松散底质颗粒滩、绿藻滩/滩间以及外缓坡沉积。生物扰动造成不同环境沉积储层的非均质性，潜穴的储集空间、渗透率、含油性能等较基质得到改善。生物扰动造成潜穴与基质的组构差异，在此基础上叠加胶结、溶蚀、压实等差异性成岩改造作用后，进而形成3种储层非均质性类型。储层非均质性受控于沉积环境、岩石类型、遗迹组构、成岩作用等因素。生物扰动与沉积、成岩协同控制Kh2段多尺度的强非均质性。

Bioturbation and reservoir heterogeneity study of Upper Cretaceous Kh2 member,AD Oilfield,Iraq

AD Oilfield is located in the south-central Iraq, and the Khasib Formation deposited during the Late Cretaceous Turonian Age is one of the crucial oil-bearing strata. Kh2 member is the main producing layer of Khasib Formation and develops a large number of bioturbation structures. The water injection development process of Kh2 member is heavily restricted at present due to the strong reservoir heterogeneity. In aim of clarifying the correlation and genetic relationship between bioturbation and Kh2 reservoir heterogeneity, the study of ichnology characteristics, heterogeneity characteristics, types and genetics were carried out through petrography, ichnology and reservoir geology methods based on core, thin-section observation, cathodoluminescence and spot permeability tests. Results show that the Kh2 member mainly developed four ichnofabrics: Thalassinoides-Rhizocorallium, Ophiomorpha, Thalassinoides-Palaeophycus, Thalassinoides-Rhizocorallium-Planolites corresponding to mid-ramp sand beach firmground, sand beach looseground, green algae beach and beach interact, outer ramp deposition. Bioturbation led to the Kh2 reservoir heterogeneity and the reservoir spaces, oil-bearing and spot permeability distribution of burrows were improved comparing with the matrix. Bioturbation caused the composition and structure difference between burrow and matrix, and the physical and chemical properties of the two varied correspondingly. Based on the fabric difference as material basis and later superimposed by differential diagenesis including cementation, dissolution, compaction, etc., three heterogeneous types were formed and their genetic models were controlled by sedimentary environment, rock type, ichnofabric and diagenesis cooperatively. Bioturbation, sedimentation and diagenesis control the strong and multi-scale reservoir heterogeneity of Kh2 member coordinately.