冀中坳陷东北部石炭—二叠系储层特征及勘探方向

Reservoir Characteristic and Exploration Target of Carboniferous-Permian Reservoirs in Northwestern Jizhong Depression

渤海湾盆地冀中坳陷石炭—二叠系残留分布区即坳陷东北部的文安斜坡、杨村斜坡、大城凸起等地区,受印支—燕山和喜马拉雅期强烈的后期构造运动改造,历经差异升降和拉张断陷两大构造发育阶段,致使东、西部剥蚀带的埋藏史表现为沉降—抬升—沉降、沉降—抬升两种类型。区内沉积体系发育较为齐全,自下而上可以识别出滨海潮坪—沼泽、三角洲和河流等三大沉积体系;其中,三角洲和河流体系发育的分流河道、辫状河道砂岩分布范围广、厚度大,形成了该区最主要的砂体类型。区内砂岩储层在其间断埋藏成岩过程中,受表生淋滤作用和深部淋滤作用的影响,形成了较为发育的次生孔隙,孔隙度一般为15%～25%,大气水的深部淋滤作用又进一步改善了断层发育区的储集性能,并由此形成了该区优质的储层。综合评价认为,西部剥蚀带附近是最有利的勘探区带。

The residual distribution area of Carboniferous-Permian in northwestern Jizhong depression, including Wen'an slope,Yangcun slope and Dacheng uplift, has sufferred from the later strong reconstruction of Indosinian-Yanshan and Himalayan movements as well as differential uplift-subsidence and pullapart-fault depression stages. As a result, the burial history in its east and west denuded belts witnessed uplift-subsidence-uplift and subsidence-uplift stages. However, the depositional systems of Carboniferous-Permian developed well, three types of depositional systems such as tide flat and swamp, delta and river can be identified from the bottom to the top , and the sandstone distributed in the distributary channels or braided channels microfacies of delta and river depositional systems covered large areas ,widely distributed and deposited in a deep depth, and formed main sand body types in this area. In the process of sandstone buried discontinuously and the reservoir diagenetic, especially, meteoric hypergene leaching process is an important factor to form the secondary porosity in sandstone reservoirs, the porosity degree is generally 15%~25%. Moreover, the deep meteoric leaching along fault surface may keep on improving the reservoir property of the areas developed with many faults, which formed the high quality reservoirs in this area. Based on comprehensive evaluation, it suggests that the west denudation belt should be the most favorable area for gas exploration.