安岳-威东地区须家河组低渗、低阻油气层形成机理

GENETIC MECHANISM OF LOW PERMEABILITY AND LOW RESISTIVITY RESERVOIRS IN XUJIAHE GROUP OF ANYUE-WEIDONG AREA

安岳～威东地区须家河组低渗储层中普遍发育低阻油气层，其成因类型多样、识别难度大。针对这一问题，利用岩心分析化验资料，结合低阻油气层测井响应特征，综合分析认为，造成该地区低渗低阻油气层的主要因素为：①高不动水饱和度；②高地层水矿化度；③低幅度构造背景引起气水分异差；④复杂的孔隙结构造成油气运移对地层水驱替不彻底，残留大量地层水。此外，局部富集导电矿物和钻井液侵入进一步降低了油气层的电阻率。弄清了低渗背景下发育的低阻油气层形成机理，探索出低阻变化规律及其与储层物性之间的关系，为准确识别和评价低阻油气层提供有利的依据，这也为下一步勘探开发奠定可靠的地质基础。

Low resistivity reservoirs usually develop in low permeability reservoirs in Xujiahe group of Anyue-Weidong area.It is difficult to identify them because of diversified genetic types.Through comprehensive analysis,it is thought that there are four key factors to form low permeability and low resistivity reservoirs:①high immobile water saturation;②high water salinity;③gas-water differential caused by low amplitude structural background;④complcated pore structure makes oil and gas migration inexhaustively on drive of formation water and remains a lot of formation water.Furthermore,localized enrichment of conductive minerals and invasion of drilling fluid reduce the resistivity of reservoirs.To know the genetic mechanism and search out the law of low resistivity variation and relationship between reservoir physical properties can provide favorable foundation for identifying and evaluating low resistivity reservoirs.It also lays a reliable geological foundation for further exploration and development.