The simulation results of relationship between cementation exponent m and total porosity of different diagenetic facies with different content of parameters

The study of conduction mechanism is the key to establishing the
subsequent physical derivations, resistivity simulation and saturation
models. The purpose of this research is to clarify the conduction
mechanisms under different diagenetic facies and build suitable saturation
evaluation models. Experimental data of tight gas sandstone from the Ordos
Basin were analysed, including data from scanning electron microscopy,
conventional core physical property analysis, core casting thin section
analysis, core mercury intrusion experiments, and rock electrical
conductivity experiments. Accordingly, the diagenetic minerals of the
study block were examined, the diagenetic facies were classified by
differences in diagenetic properties across the study area. The reservoir
was divided into 3 types of diagenetic facies: construction facies,
cementation facies, and destruction facies. On this basis, the
conductivity characteristics and saturation models of different diagenetic
facies within the study area were systematically discussed for the first
time. A number of experiments have shown that according to the type of
diagenesis, the structure of the pores, and the influence of the
reservoir, a classification scheme for diagenetic facies (consisting of
construction, cementation, and destruction facies) can be established.
According to the influence of the diagenesis of various diagenetic facies,
theoretical pore structure models of the three diagenetic facies were
established, in which the construction facies includes mainly dissolved
feldspar pores and intergranular pores, the destruction facies includes
clay residual intergranular pores and intergranular pores, and the
cementation facies includes primarily residual intergranular pores. Based
on these theoretical pore structure models, the construction facies was
evaluated with a pore-connected vuggy conductivity model, the destruction
facies was evaluated with a nonconnected matrix pore conductivity model,
and the cementation facies was evaluated with a residual intergranular
pore conductivity model. Then, the rationality of each model and the
effects of the parameters in each model on the final cementation exponent
were analysed by simulation. The predicted cementation exponents of the
diagenetic facies match the measured cementation exponents well and can
guide the qualitative understanding of these characteristics in such
reservoirs.