Research On The Conductive Mechanism Of Low-permeability Shaly Sand

At present, the interpretation of low-permeability complex shaly sandstones is one of the most difficult challenges in log evaluation. Its special petrophysical characteristics complicate the logging response of such reservoirs. These features made models which used in conventional reservoirs unusable and water saturation calculated in such reservoirs inaccurate. The research indicate that features which related to the mechanism of conductive in such pays are: the additional conductance arised from fine sediment grains , high irreducible water saturation caused by micropores and complicated pore structure.This research is mainly based on experimental data of low-resistivity and low-permeability shaly sand samples. The paper analyses the applicability and shortcomings of electric double layer model. In dual-water model, we adopts a new method of parameter calculation which solves the difficulty of determining formation factor and Qv. In capillary model, we improve its principle and introduce a new parameter which describes the invasion of hydrocarbon in small pores. Results show that the improved capillary model is feasible in low-permeability reservoirs.Analyze the factors related to rock conductance inferred using numerical simulation. The type, volume and distribution of clay materials play an important role in shaly sand conductance, especially when the salinity of formation water is low. As to low-permeability complex reservoir, the paper analyses the influence of micropores and the complex pore structure which answer for obscure conductive mechanism. Satisfying result is obtained.