俄罗斯季曼-伯朝拉盆地碳酸盐岩油气藏特征分析——以Trebs和Titov油气田为例

季曼-伯朝拉盆地是俄罗斯境内的富油气盆地,属裂谷-被动陆缘前陆复合盆地;早里菲世早石炭世为裂谷-大洋被动边缘、浅海大陆架阶段,晚石炭世第四纪为乌拉尔造山和造山后的前陆演化阶段。盆地共发育3套碳酸盐岩储集层,包括下古生界、下泥盆统-上泥盆统(上弗拉斯阶-法门阶)及石炭系-下二叠统碳酸盐岩。研究表明,该区碳酸盐岩储层明显受沉积、成岩双重作用的控制,有利沉积相带及不整合面共同控制有效储层的分布;储集空间包括原生孔隙和喀斯特作用形成的溶蚀孔洞,储层物性空间横、纵向变化大,通常不整面之下30~40 m为有利储层发育的最佳地带;储层非均质性极强,盆地内部分油藏具有低孔隙度、低渗透率特性,制约了油气藏开发速度。通过分析该盆地具有较长开发历史的12个碳酸盐岩油气藏数据,证实该类油藏具有低采油速度、低采出程度特点。 

Characteristics of carbonate reservoirs in the Timan-Pechora Basin in Russia: The Trebs and Titov oil fields as examples

The Timan-Pechora Basin is a petroliferous basin in Russia. It is a composite basin of rift, passive margin, and foreland. From the Early Riphing to Early Carboniferous, a rift, passive margin, and shallow continental shelf developed in the basin. From the Late Carboniferous to Quaternary, the Ural orogeny and post-orogeny foreland developed. Three sets of carbonate reservoirs were formed in the basin, including the Lower Paleozoic, Lower-Upper Devonian (Frasnian-Famennian), and Carboniferous-Lower Permian. They were controlled by both sedimentary and diagenetic effects. Favorable sedimentary facies and unconformities controlled the distribution of effective reservoirs. Reservoir porosity includes primary pores and dissolution vugs formed by karst. Reservoir physical properties vary both horizontally and vertically. Generally, the formation 30-40 m below an unconformity is the most favorable reservoir position. The reservoirs have a strong heterogeneity, and are featured by low porosity and low permeability, which restricts hydrocarbon exploitation. Data from 12 carbonate reservoirs with a long development history in the study area were analyzed, confirming low recovery rates and low recovery levels.