| Author's Name: QIAO Zhanfeng, SUN Yuanhui, CAO Peng, ZHU Guangya, SHAO Guanming, WANG Yongjun, ZHANG Jie, SUN Xiaowei |
| Barrier and baffle (BB) and high permeable streak (HPS) are important factors influencing the development
effectiveness of the reservoir. Mishrif reservoir in Iraq H Oilfield used to be treated as massive reservoir. However, with
the development of the reservoir, some of serious problems, including water breakthrough, unclear water injection
response, etc., raise up, which influence the production effectiveness significantly. Based on the cores, thin-sections,
petrophysical properties, and logging data, by means of analyzing the controls of rock fabric, pore types, and diagenetic
modification on the permeability, the origin and development of BB and HPS of Mishrif Formation in Iraq H Oilfield have
been studied. It is known that the permeability of bioclastic limestone of Mishrif Formation is closely related to the rock
fabric, pore types, and diagenetic modification, which determine the origin and development of BB and HPS. BB includes barrier, baffle, and lateral barrier, and barrier can be subdivided into deep deposition type and shallow deposition type, consisting of mainly mudstone, wackstone, and coaly mudstone, developed in the lower part and top part of the sequence respectively, especially the barrier occurred in the transgrassive system tract of 3rd-order sequence would be able to comprise the regional barrier separating the reservoirs. Baffle, influencing the fluid flow within the reservoir, can be subdivided into sedimentary type and diagenesis type, controlled by sedimentary architecture and high frequency sequence respectively. Lateral barrier consists of lime mudstone filling in tidal channel and / or incision valley which usually occurred around sequence boundary. HPS also includes sedimentary type and diagenesis type, the former consists of mainly high energy bioclastic grainstone filled in tidal channel or bioclastic shoals with obviously high permeability compared with surrounding lagoonal fine grained sediments; the latter formed by the lagoonal fine grained sediments and/or shoal bioclastic grainstone dissolved by meteoric water during exposure, is mainly developed under the 4th or 3rdorder sequence boundary and controlled by lithofacies and topography. Multiple origins of BB and HPS significantly complicated the reservoir architecture, which influences the production largely. The implication of this study to the development of oilfield are twofold: on one hand, the developing section or perforation could avoid the BB and HPS mostly occurred in the bottom and top part of the sequence, so as not to penetrate the development units; on the other hand, it’s better to adopt the internal injection within the development units and to design the injection and production relation based on the development of baffles. The knowledge of BBs and HPSs are meaningful to the development of massive reservoirs of meso Cenozoic counterparts in Mideast, Mid-Asia, and South American. |
