柴达木盆地跃进地区下干柴沟组上段藻丘灰岩储层特征

柴达木盆地跃进地区下干柴沟组上段 (E3 2 )为一套碳酸盐岩与泥岩互层或夹层的地层。研究揭示这套碳酸盐岩形成于滨浅湖环境,岩石类型有陆屑泥晶灰岩、藻团块灰岩、藻泥晶灰岩、颗粒灰岩、藻纹层灰岩及藻叠层灰岩。其中,藻纹层灰岩及藻叠层灰岩 (藻丘 )储集物性极佳并含油,混合水白云化及大气淡水淋溶是该套储层形成的主要原因。特大孔 +(微 )细喉组合、大孔 +(微 )细喉组合是主要的孔喉组合类型。自然电位高负值、视电阻率极高值、过井地震剖面强反射特征是追踪这套含油藻丘灰岩时空展布的重要依据。上述研究成果对跃进地区的油气勘探和开发均具重要意义。

A Research on E32 Algal-Reef Reservoir in Yuejin Area, Qaidam Basin, Northwestern China

E ₃ 2 lacustrine stratum, located in Yuejin area, Qaidam Basin, northwestern China, is mainly composed of interbedded /intercalated carbonate rock mudstone. Terrigenous debris-bearing micrite,algea-originated laminated micrite,algea-originated stromatolitic micrite,algea-originated micrite and grainstone could be recognized in the carbonate rock, of which algea-originated laminated micrite and algea-originated stromatolitic micrite developed into good reservoir(oil-bearing) with a mean porosity of 25% and mean permeability of proximate 100×10 -3 μm 2. Meteoric water-seawater mixing dolomitization and dissolution in meteoric vadose zone were the main courses for reservoir development. Based on the research of diagenetic sequence, porosity evolution of the algea-originated laminated micrite and algea-originated stromatolitic micrite have been reconstructed. Furthermore, pore and throat diameters and their combinations have been discussed, which play an important role in petroleum development. The determination of spatial distribution for E 3 2 algal-reef micrite reservoir is very important in petroleum exploration in Yuejin area. Log and seismic data also play important roles in prediction of algal-reef micrite reservoir. High SP and SN values imply the exist of petroleum-bearing algal-reef micrite reservoir, while strong seismic reflection shows the lateral distribution of them. Based on the above discussion, spatial distribution of E ₃ 2 algal-reef micrite reservoir in Yuejin area have been mapped.