基于连通导电理论的白云岩储层导电模型

A conductivity model for dolomite reservoirs based on connectivity theory

针对雷家地区沙四段白云岩储层既有基质孔隙又有裂缝孔隙存在的特征,将孔隙-裂缝型泥质白云岩划分为基质相、裂缝相和黏土相,认为基质侵入较浅,其孔隙包含油气和水,而裂缝侵入较深,其孔隙包含残余油气和泥浆滤液,利用连通导电理论,建立了一种新的适用于雷家地区孔隙-裂缝型白云岩储层的导电模型.对于未侵入的饱含水纯白云岩,当只含基质孔隙时,该模型可简化为孔隙型纯岩石的阿尔奇公式;当只含裂缝孔隙且基质相导电指数等于1时,该模型可简化为水平裂缝纯岩石的地层因素与孔隙度关系.从理论上分析了连通导电模型中基质相导电指数、裂缝相导电指数及裂缝孔隙度对岩石导电规律的影响,得出在总含水饱和度一定时,岩石电阻率随基质相导电指数增大而增大,随裂缝孔隙度增大而减小,随裂缝相导电指数变化较小,而电阻增大系数随基质相导电指数、裂缝孔隙度增大而增大,随裂缝相导电指数变化较小.利用所建立的导电模型对该区块雷A井进行处理,并与试油结论进行对比,结果表明该模型可很好地应用于该区块孔隙-裂缝型泥质白云岩储层的饱和度评价.

In ES4 dolomite reservoirs of Leijia area, reservoirs were characterized by both matrix pore and fracture pore.The pore-fracture shaly dolomite reservoirs were divided into matrix phase, fracture phase and clay phase.Considering that matrix invasion was shallow which pore contains hydrocarbon and water, while fracture invasion was deep, its pore con-tains hydrocarbon and mud filtrate.A new conductivity model was established for the porous and fractured dolomite reservoirs in Leijia area using connectivity theory.For non-invaded water saturated clean dolomite, with only matrix pore existing, the model can be simplified to the Archie formula for porous -type clean rock; when only fracture pore existed with the conductive index of matrix phase equals 1.0, the model can be simplified as the relationship between the formation factors and porosity of horizontal fracture clean rock.Influence of frac-ture porosity and conductivity exponents of matrix phase and fracture phase on conductivity of rock were analyzed theoretically.Formation resistivity increases as conductive exponents of matrix phase increases;it decreased as fracture porosity increases and changed little as con-ductivity exponents of fracture phase varies.Resistivity index increased as fraction of conduc-tive exponents of matrix phase and fracture porosity increased, and it changed little with con-ductivity exponents of fracture phase varied.Log data of Lei A were processed with the mod-el, and the results were compared with well test results.The results showed that the model could be well applied in saturation evaluation of porous and fractured shaly dolomite reser-voirs.