摘要
白云岩储层的孔喉非均质性主要表现为孔喉结构及展布特征复杂，常规储层表征方法对其进行微观定量化表征存在很大难度。利用CT成像技术对塔东古城地区奥陶系（鹰山组）鹰三段的9个白云岩储层样品进行实验测试，建立了孔喉结构的三维网络模型，并在此基础上计算了孔喉半径、孔喉数量、总孔隙度、空间连通性等表征参数。实验结果表明，白云岩储层样品孔喉半径分布曲线呈现出明显差异。依据曲线形态特征，将其分为3类：①正常单主峰型；②喉道多峰、孔隙单主峰型；③喉道多峰、孔隙多峰型。结合岩心观察和铸体薄片鉴定，对该三类曲线形态的成因展开了分析，并建立了孔喉半径分布模式。综合分析认为，以晶间孔为主要孔隙类型的白云岩储层，孔喉半径曲线整体上呈现出较匀称的单主峰偏态分布特征，局部微裂缝的发育会造成喉道半径曲线上主峰旁较小的尖峰；若存在孔隙沿层理面等残余沉积构造定向富集的现象，则喉道半径曲线会呈现出明显的多峰形态；随着溶蚀作用增强、晶间溶孔的增多，孔喉半径分布曲线均会向多峰形态发展，表现出越来越强的非均质性。
Abstract
The pore-throat heterogeneity of dolomite reservoirs is mainly reflected by their complex structure and distribution that are difficult to sufficiently and quantitatively analyze with conventional reservoir characterization methods.In this study, nine samples from dolomite reservoirs in the 3rd member of the Ordovician Yingshan Formation (Ying 3 member), Gucheng area, eastern Tarim Basin, were CT scanned to establish a 3D network model for the pore-throats.Such reservoir parameters as pore-throat radius, pore and throat numbers, total porosity, spatial connectivity, and etc., were calculated based on the model.The results show obvious differences among the pore-throat radius distribution curves for the samples.These curves can then be grouped into three categories in terms of shape features, that is, Type Ⅰ, the normal unimodal curve; Type Ⅱ, the unimodal curve for pores and multi-modal curve for throats; and Type Ⅲ, the multi-modal curve for both pores and throats.The genesis of the curves was analyzed and pore-throat radius distribution patterns were set up based on core observation and casting thin section identification of the samples.In conclusion, the pore-throat radius distribution curves for dolomite reservoirs dominated by intra-crystalline pores are generally evenly skewed unimodal distribution, except for some tinny peaks beside the main summits caused by the development of local micro-fractures.The curves may show obvious multiple summits with pores converging along some residual sedimentary structures such as bedding surfaces.All the curves may show the multi-modal distribution with increasing numbers of inter-crystalline dissolved pores under stronger dissolution that indicates high heterogeneity of reservoirs.
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