低孔隙度低渗透率储层物性参数与胶结指数关系研究

On the Relation Between Cementation Exponent m and Petrophysical Parameters of Low Permeability and Low Porosity Reservoir

在低孔隙度低渗透率储层实际应用中发现,地层因素和孔隙度关系与典型的Archie公式特征不符。对于完全含水储层,由于岩石中导电介质和渗流介质都是地层水,其导电路径与渗流路径可近似看作相同,可以利用孔隙曲折度搭建岩石物性参数与电性参数之间的桥梁。对储层岩石孔隙曲折度的分析表明,在低孔隙度低渗透率储层中,孔隙曲折度与渗透率呈正比关系,渗透率越大,孔隙曲折度越大。当渗透率降低时,孔隙曲折度减小,说明细或微毛细管之间存在相互交联沟通,相对增加了岩石孔隙的渗流能力。正因为微毛细管之间的相互交联沟通形成了导电网络,导致储层岩石导电性增强;当孔隙度变小时,细或微毛细管孔隙所占比例增大,胶结指数值降低。

Archie equation is a bridge between resistivity logging and quantitative saturation eval- uation in reservoir, and links porous rock electrical properties with the types of fluid contained. For high porosity sandstone reservoir, the relation can be well described by Archie＇s formula, but in low permeability and low porosity reservoirs, the relationship between formation factors and porosity is different from Archie formula described. Due to conductive medium and seepage medium in reservoir are formation water, the conductive path and seepage path can be approxi- mately regarded as the same. So pore tortuous degree can be used to connect petrophysical pa- rameter with electrical parameter of rock. The analysis for pore tortuous degree of rock indicates that in low permeability and low porosity reservoir the higher permeability is, the more pore tor- tuous degree is. That when permeability is low, pore tortuous degree is less, which shows that it exists mutual cross-linking communication among micro-capillaries, relatively increasing permea- bility of rock. Micro-capillary mutual cross-linking leads to form the conductive network, and en- hance conductivity of reservoir rock. When porosity decreases, the proportion of fine and micro- capillary pore increases, the value of cementation exponent （m） reduces.