塔里木盆地克深2气田储层构造裂缝多方法综合评价

Comprehensive assessment of reservoir structural fracture with multiple methods in Keshen-2 gas field,Tarim Basin

构造裂缝是改善克深2气田低渗透砂岩储层物性的重要因素,对构造裂缝的分布特征进行分析有利于提高钻井成功率,综合采用岩心描述、数值模拟、主曲率法、二元法以及天然气产能数据,对克深2气田巴什基奇克组的构造裂缝进行了多方法综合评价。结果表明:克深2气田的构造裂缝以直立和高角度的剪切裂缝为主,断层附近多发育密集网状缝,且具有较高的充填程度;深度越大,构造裂缝的分布越趋于分散;背斜高部位的构造裂缝线密度较低,但开度和孔隙度等物性参数较高,构造裂缝的整体发育程度较强,且充填程度较低,通常具有较高的产能,背斜翼部和构造低部位则与之相反;鞍部构造裂缝也较发育,但受较高的充填程度或其他未知因素的影响,天然气产能较低。研究还得出,构造裂缝密度并未考虑裂缝的开度,因此在油气田开发中单纯根据构造裂缝密度值来判断构造裂缝发育有利区并不合适,在粗略评价构造裂缝发育程度时,可采用构造裂缝的孔隙度或渗透率,精细评价时还要考虑裂缝产状、延伸距离、连通性和有效性等因素进行综合分析。构造裂缝发育程度的系统化和定量化综合评价仍然是一个有待攻关的前沿课题。

Structural fractures are a significant factor for improving the physical properties of low-permeability sandstone reservoirs in Keshen-2 Gas Field. An analysis on the distribution characteristics of structural fractures is beneficial to enhance the success rate of well drilling. Therefore, the structural fractures of Bashijiqike Formation in Keshen-2 Gas Field was comprehensively evaluated based on core description, numerical simulation, principal curvature method, binary method and natural gas production data, multi- method comprehensive assessment. The results show that structural fractures in Keshen-2 Gas Field are dominated by the upright shearing fractures with high angles. Intensive netted fractures are mainly developed adjacent to faults with high filling degree. The greater the depth is, the more scattered the distribution of structural fracture will be. At the high positions of anticline, structural fractures have low linear density, but with higher physical properties such as opening and porosity, indicating the high overall devel- opment degree of structural fractures with low filling degree and large natural gas production capacity. The situation in the wings of anticline is opposite to the low positions of the structure. Structural fractures are also relatively developed in the saddle, where the natural gas production capacity is low due to high filling degree or other unknown factors. Moreover, the research indicates that frac- ture opening is not considered in terms of the density of structural fracture. Thus, it is not suitable to determine the favorable devel- opment zones of structural fractures only according to the density of structural fractures in the development of oil and gas fields. The porosity or permeability of structural fractures can be used for roughly evaluating the development degree of structural fracture, while fracture occurrence, extended distance, connectivity, effectiveness and other factors should be considered for comprehensive a- nalysis in the detailed evaluation. Comprehensive systematical and quantitative assessment on the development degree of structural fracture is still a front subject to be studied.