Abstract: Large-scale bioturbated carbonate rock reservoirs are developed in Ordovician Yingshan and Yijianfang Formations in the Tahe Oilfield. On the basis of core observation and detailed description,through observing thin sections under polarizing microscope,cathodoluminescence microscope and scanning and analyzing the plugs by using X-ray microscope,we have conducted digital characterization of pore structures and connectivity analysis of microcosmic pore structures of the Ordovician bioturbated carbonate reservoir rocks in Tahe Oilfield of Tarim Basin. The results show that: (1)Because of the great difference in rock fabric between burrow fills and surrounding host rock matrix,these reservoirs are highly heterogeneous. (2)The burrow fills are mainly composed of euhedral or subhedral dolomite crystals. The pore volume sets are between 10~100 μm³,the throat radii are generally smaller than 10 μm,and the throat lengths are generally shorter than 40 μm. The dolomite intercrystalline pores are the main reservoir space for this type of reservoir,and various pores are not well developed in the host rock matrix. (3)The porosity of burrow fills is between 7% and 10%. Although the number of isolated pores is large,the volume of connected pores still accounts for a large proportion. Moreover,the topology structure of connected pores is complex,and the pore network connectivity is overall great. Through coarsening and upgrading of Representative Elementary Volume(REV)in the scale,it is found that the pores in the samples are locally connected,while the overall connectivity is relatively poor. This study accurately characterized the micro-pore structures of the bioturbated carbonate reservoirs,which can provide the required characteristic parameters for the subsequent micro-seepage simulation of the bioturbated carbonate reservoirs. In future,the digital characterization of pore structure and the microcosmic seepage simulation of this type of bioturbated carbonate reservoirs should be combined with the macroscopic distribution rules and applied to the actual reservoir evaluation,which can provide guidance for the estimation of oil-gas resources, optimization of development plans, prediction of productivity and enhancement of oil-gas recovery.

Key words: bioturbation, pore structure, quantitative characterization, connectivity analysis, Tahe Oilfield

摘要： 塔河油田奥陶系鹰山组和一间房组发育大规模生物扰动碳酸盐岩储集层。在岩心观测和详细描述的基础上,通过岩石薄片的偏光显微镜、阴极发光显微镜观测和柱塞样品的X射线显微镜扫描与分析,实现了塔河油田奥陶系生物扰动碳酸盐岩储集层孔隙结构的数字化表征与连通性分析。结果表明: (1)由于生物扰动区潜穴充填物和围岩基质的岩石组构差异大,使这类储集层呈现极强的非均质性。(2)生物潜穴充填物主要由白云石晶体组成,白云石晶体以自形、半自形晶体为主;白云石晶间孔隙发育,孔隙体积集中于10~100μm³,喉道半径一般小于10μm,喉道长度一般小于40μm,白云石晶间孔为这类储集层的主要储集空间,围岩基质孔隙不发育。(3)生物潜穴充填物孔隙度介于7%~10%,孤立孔隙虽然数量多,但连通孔隙体积占比大,且连通孔隙拓扑结构复杂,孔隙连通性很好;通过表征单元体的尺度粗化升级分析发现,这类储集层的孔隙局部连通较好,而整体连通性相对较差。该研究真实、直观、准确刻画了生物扰动碳酸盐岩储集层微观孔隙结构特征,可为后续这类生物扰动碳酸盐岩储集层的微观渗流模拟研究提供所需的特征参数;未来将这类生物扰动碳酸盐岩储集层微观尺度上的孔隙结构数字化表征和渗流模拟结果与宏观分布规律相结合并应用到实际储集层评价中,可为这类储集层的油气资源量估算、开发方案优选、产能预测和提高采收率提供指导。

关键词: 生物扰动, 孔隙结构, 定量表征, 连通性分析, 塔河油田

CLC Number: 

• Q911.28