Evaluation of a novel mechanistic approach to predict transport of water and ions through shale

Abstract

Prediction of transport parameters is an important issue in shale formations. A unique and novel method to address this subject is the Revil model (Revil et al. 2011) which has been updated here for multivalent salts. The updated model for water and ion transport through shale has been evaluated against a range of experimental data sets. The updated Revil model only needs a few number of shale properties such as cation exchange capacity (CEC), porosity, and grain density which can be readily measured in laboratory. Also in the present work three parameters (f_Q,β_((+))^S,ν) have been considered as calibration parameters in the dynamic mode. In addition to updating Revil model for multivalent salts, we derived equations to calculate water and ion uptake in shale sample, a simplified equation to estimate IS and a proof for the conjecture that IS correlates with ME. The results show that in static mode, the model predicted the trend of data, however, the effect of semipermeable nature of shale on water uptake and alteration of ionic concentration in pore space was found negligible because of high salt concentrations (i.e. Cf>0.5M). In dynamic mode, by adjusting calibration parameters for each of test data, a complete matching could be obtained. In case of adjusting all experiments with only three common calibration parameters the prediction was not satisfactory, however, the results of "intact-anion method" was more accurate than "Donnan method". When multiple sets of ME data in a broader range of concentration including low concentrations were plotted along with high-concentration data, correlativity was significant (R2>0.9). The present study for the first time in petroleum engineering research, suggested and implemented the updated Revil model as an applied tool for investigating static and dynamic behavior of semipermeable shales.