碳酸盐岩储层非均质性极强,孔喉结构复杂,且孔隙度与渗透率相关性差.中东地区白垩系Mishrif组发育典型的孔隙型碳酸盐岩储层,相同孔隙度条件下渗透率相差达3个数量级,给准确评价该类储层的渗透能力以及合理的储层分类带来了极大挑战.为深入分析中东地区Mishrif组孔隙型碳酸盐岩储层渗透率的主控因素,基于M油田415个高压压汞实验样品数据统计对比,明确了研究区Mishrif组碳酸盐岩储层具有多种模态并存的孔喉结构特征,其中单模态孔喉结构储层的孔渗相关性明显好于双模态和多模态孔喉结构储层;进而对孔喉结构特征参数进行定量分析,明确多模态孔喉结构碳酸盐岩储层孔隙度和渗透率随孔喉结构参数变化的规律.研究表明,汞饱和度为20％对应的孔喉半径(R20)与渗透率的相关性最好,将R20作为特征孔喉半径与孔隙度和渗透率进行相关性分析发现,随着孔喉半径的增加,孔隙度先线性增加,至一定程度后维持稳定不再增加,与之形成对比的是随着R20的增加,渗透率持续增加.

The M carbonate reservoir in Rumaila Oilfield,Iraq,is studied to describe the response features of various lithologies and sedimentary facies on XRMI image logging.By using core calibrated the image logging and combining the natural gamma ray spectrum logging,litho-density logging and other traditional logging material,this paper had effectively distinguished clay mineral,tight limestone,reef limestone,bioclastic limestone et al.Besides,the image logging response characteristics of sedimentary facies,such as ramp face,reef face,bioclastic shoal face et al,had also been summed up.At last,a plate for electrofacies model and the corresponding sedimentary facies had been established and applied on a single well for continuous electrofacies interpretation.The results show that: the natural gamma ray spectrum response at the top of M formation is high Thorium,high Potassium and high Uranium which indicates that the M formation had exposure to the air at the end sedimentation of M formation,thus formed a unconformable contact with the overlying formation.The lower part of M formation deposited ramp face,high energy bioclastic shoal face,reef face,back shoal face and lagoon face successively,which form a complete regressional sedimentation cycle.

储层岩石含流体饱和度的确定涉及面广、影响因素多、确定难度大,在实际油气藏评价中,需要发展一套实用可靠的饱和度计算方法.在阿尔奇公式的应用中,通常把岩石当成岩石骨架、孔隙和孔隙流体(油气和水)3个组成部分.然而,在多数情况下,油的电性特征与地层的岩石骨架类似,都为电流的不良导体,那么,如果将油成分视为不导电的岩石骨架一部分,则岩石总可认为是充满水的,此时,由阿尔奇公式导出的孔隙度为岩石的含水孔隙度.以该思路为指导,并结合孔隙度测井方法,可以推导出一套岩石饱和度计算公式和可动油评价方法.更进一步,通过实验室岩石毛管压力曲线和油藏中自由水面以上的高度,可标定出不同类型储层的含水饱和度,以此作为测井饱和度计算的检验和校正.将上述方法应用于中东Mishrif厚壳蛤颗粒灰岩饱和度解释和储层评价中,取得了很好的效果.