低渗砂岩储层岩石学特征与应力敏感性耦合关系——以鄂尔多斯盆地苏里格-吉尔地区下石盒子组八段下亚段为例

Coupling relations between the petrologic characteristics and stress-sensitiveness in low-permeability sandstone reservoirs:an example from the lower 8 member of the Lower Shihezi Formation in Sulige-Jier area,Ordos Basin

何江 付永雷 沈桂川 朱晓燕 伍启林

He Jiang Fu Yonglei Shen Guichuan Zhu Xiaoyan Wu Qilin

低渗油气藏主要采取衰竭式开发,地层压力得不到补充,储层的应力敏感性问题显得尤为突出。以鄂尔多斯盆地苏里格-吉尔地区下石盒子组八段下亚段为例,依靠详细的井下地质调查、岩心精细描述、系统取样配套测试及室内比对分析等方法,对岩石学特征与应力敏感性耦合关系进行精细解剖,发现目的层位岩石类型主要为岩屑石英砂岩,其次为硅质石英砂岩以及少量岩屑砂岩。样品采用CMS-400型高压孔渗分析仪测试,初始渗透率普遍偏低,应力敏感性中等偏强,两者呈明显的正相关关系。岩石组分中,柔性岩屑和基质硬度及稳定性低,在外力作用下易变形、破碎和位移,其含量与应力敏感性呈正相关关系。碎屑石英、刚性岩屑及石英、铁绿泥石等胶结物硬度和稳定性高,在外力作用下变形弱,其含量与应力敏感性呈负相关关系。不同岩类因岩石学特征差异间接导致应力敏感性不同,在开发过程中可采用不同级别的生产压差求得油田的最优产能。

Low-permeability reservoirs are usually developed through natural depletion and the loss of formation pressure is not restored,causing stress sensitivity of reservoirs.We chose the lower 8 member of the Lower Shihezi Formation in Sulige-Jier area,the Ordos Basin as a case study.Through downhole geological survey,core observation,systematic sampling and testing,and lab correlation and analysis,we studied the coupling relation between the petrologic characteristics and stress-sensitivity and found out that the rock types of the layers of interest are mainly lithic quartz sandstone,followed by siliceous quartz sandstone and small amount of lithic sandstone.The samples were tested with model CMS-400 high-pressure porosity and permeability analyzer.The initial permeability was low and stress-sensitivity was medium to strong and the two presented an obvious positive correlation.Among the rock components,the soft debris and matrix that have low hardness and stability are easily deformed,crushed and displaced under exogenic action.Their contents have positive correlations with the stress-sensitivity.Detrital quartz,rigid debris and cements such asquartz and daphnite have higher hardness and stability and remain stable under exogenic action.And their contents have negative correlations with stress-sensitivity.Different rocks have various stress-sensitivities because of their different petrologic characteristics.During the development of oilfields,we suggest to optimize deliverability by using production pressure differentials at different levels.

10.11743/ogg20120614