伊拉克HF油田上白垩统碳酸盐缓坡相储层发育特征

伊拉克HF油田上白垩统Hartha组灰岩沉积在碳酸盐缓坡环境,储层发育特征及其主控因素尚不明确。通过钻井、测井、岩芯和地震资料,并结合薄片观察、分析化验,研究了该油田Hartha组的岩石学特征、储集空间特征及物性特征,并分析了沉积相和成岩作用对储层发育的控制。结果表明,厚度约50 m的Hartha组的储层岩石类型主要为粒泥灰岩、泥粒灰岩和颗粒灰岩,孔隙度10%～22%,渗透率集中在(0.1～0.5)×10^(-3 )μm^2和(1～5)×10^(-3 )μm^2,基质物性较好。Hartha组上段储集性能相对较好,Hartha组下段发育外缓坡灰泥,储集性较差。沉积作用对储层的物性起着主要控制作用,滩相储层的物性明显好于非滩相。该套灰岩的储集空间为粒间孔、铸模孔、生物体腔孔,以及粒内溶孔和微裂缝。晚白垩世暴露剥蚀期,在表生作用下Hartha A层溶孔部分被胶结物充填,存在局部的强烈胶结带。

Characteristics of the Reservoirs in Carbonate Ramp Facies from the Upper Cretaceous,HF Oilfield,Iraq

The limestone deposits of the Upper Cretaceous Hartha Formation in the Iraqi HF oilfield are found in a carbonate ramp environment. The reservoir characteristics and main controlling factors are still unclear. Through drilling, logging, core, and seismic data, combined with thin section observations and analysis, the petrological characteristics, reservoir space types, and physical properties of the Hartha Formation in this oilfield are studied, and the controlling factors for the sedimentary facies and diagenesis are analyzed. The results show that the reservoir rocks of the Hartha Formation, with a thickness of about 50 m, are mainly wackstone, packstone and grainstone, with a porosity range of 10%-22% and permeability of (0.1-0.5)×10-3 μm2 and (1-5)×10-3 μm2, and the physical properties of the matrix are good. The upper part of the Hartha Formation has relatively good reservoir performance, while the lower part of the Hartha Formation develops external gentle slope mortar with poor reservoir performance. Sedimentation plays a major role in controlling the physical properties of reservoirs, the physical properties of reservoir rocks in shoal facies are better than that in non-shoal facies. The limestone reservoir develops inter-granular pores, biological mould pores, intra fossil pores, dissolved pores and micro fractures. During the exposure period of the Late Cretaceous, the dissolved pores were partially filled by cements under the epi-diagenesis, and there were strong cementation zones locally.