孔隙型碳酸盐岩储层地质建模探讨

以中东白垩系生物碎屑灰岩为例,基于多个油田的岩心资料、铸体薄片资料、分析化验资料及测井资料开展研究,从孔隙型碳酸盐岩储层特征入手,总结了孔隙型碳酸盐岩储层建模难点及建模方法。孔隙型碳酸盐岩储层成因要受沉积作用和成岩作用双重控制,构造作用影响弱,生物碎屑含量高;以铸模孔、生物体腔孔和残余体腔孔等次生孔隙为主;储层厚度大,垂向非均质性强。研究表明:孔隙型储层建模难点主要在构建储层格架模型、储层属性模型及建模约束方法三方面:物性隔夹层隐蔽性强,测井解释困难;贼层成因多样,静态资料难以识别;微裂缝随机展布,空间展布预测困难;复杂的孔渗关系制约了渗透率模型的建立;强烈的成岩改造降低了沉积相对储层物性的约束,不同类型储层地球物理响应区分性低,造成井间模拟约束效果差。孔隙型储层建模的方法主要有相控建模、成因建模和等时建模,其中相控建模中基于岩相的相控建模应用最为普遍。同时指出孔隙型储层建模存在问题和不足:建模方法和随机模拟算法比较局限;储层构型研究薄弱,地质知识库不健全;地震多级约束方法、虚拟井约束方法及水平井建模技术等研究不够深入;储层的穿时性和展布方向模糊化制约了变差函数分析的有效性。

Geological Modeling of Porous Carbonate Reservoirs

Taking the bioclastic limestone of Cretaceous in Middle East as an example, based on the core, cast thin section, experiments data, and logging, starting with the characteristics of porous carbonate reservoirs, difficulties and methods in modeling were systematically analyzed and summarized. The genesis of porous carbonate reservoirs were mainly controlled by sedimentation and diagenesis with weak tectonics. The content of bioclastic were high and the secondary pores such as the mold pore, the biological skeletal pore and the residual biological skeletal pore were dominant. Reservoir thickness was large with complex microstructure and intense vertical heterogeneity. The result showed that the difficulties in the modeling of porous reservoir of Cretaceous included the construction of reservoir model, the property model and the constraint method. The physical interlayer were highly hidden, the logging interpretation was difficult. The geneses of thief zone were diverse and it was difficult to identify just with static data. Micro-fractures distributed randomly and it was difficult to predict. Complex correlation of porosity and permeability restricted the building of permeability model. Intense diagenesis reduces the relationship between sedimentary and reservoir physical properties. The geophysical data had weak response on reservoirs property, which results in poor constraint between wells. The modeling methods of porous reservoir mainly included facies controlling modeling, genetic modeling and isochronous modeling. Among them, lithofacies controlling modeling based on rock type was the most useful method. It concluded that the modeling methods and simulation algorithm were relatively limited. The research on reservoir architecture was rare and the geological database on carbonate reservoir was unsound. The research on the methods of seismic multi-level constraint, the methods of virtual well constraint and the horizontal well modeling technology were not completely. The diachroneity of reservoir and the fuzzy of reservoir distribution direction restrained the validity of variogram.