A Prediction Model for Methane Adsorption Capacity in Shale Gas Reservoirs

Jie Zou,Reza Rezaee

doi:10.3390/en12020280

Abstract

Estimation of methane adsorption capacity is crucial for the characterization of shale gas reservoirs. The methane adsorption capacity in shales is measured using high-pressure methane adsorption to obtain the adsorption isotherms, which can be fitted by Langmuir model. The determined Langmuir parameters can provide the methane adsorption capacity under actual reservoir conditions. In this study, a prediction model for the methane adsorption in shales was constructed based on 66 samples from 6 basins in China and Western Australia. The model was established in four steps: a model of Langmuir volume at experimental temperature, the temperature dependence of Langmuir volume, a model of Langmuir pressure, the temperature dependence of Langmuir pressure. In the model of Langmuir volume at experimental temperature, total organic carbon (TOC) and clay content (Vsh) were considered. A positive relationship was observed between the TOC and the temperature effect on the Langmuir volume. As the Langmuir pressure is sensitive to various factors, the Langmuir pressure at experimental temperature shows no trend with the TOC, clay content and thermal maturity, but a positive trend with the Langmuir volume. The results of this study can help log analysts to quantify adsorbed gas from well-log data since TOC and Vsh, which are the measure inputs of the introduced models, can be obtained from well-log data as well.

Highlights

Shale gas contains free gas in pore volume and a significant amount of adsorbed gas on the surface area of the pore wall [1]
As the Langmuir pressure is sensitive to various factors, the Langmuir pressure at experimental temperature shows no trend with the total organic carbon (TOC), clay content and thermal maturity, but a positive trend with the Langmuir volume
Since the studied shale samples were measured at different temperatures and the amount of Results at and eachDiscussion high temperature is limited, a model of the Langmuir volume at experimental temperature

Summary

Introduction

Shale gas contains free gas in pore volume and a significant amount of adsorbed gas on the surface area of the pore wall [1]. The most popular model is the Langmuir model because of its simplicity and accuracy [2,3] Langmuir parameters such as Langmuir volume and Langmuir pressure can be determined using Equation (1) to characterize the methane adsorption isotherms of shale samples [4]. For the Langmuir pressure, Zhang, Ellis [11] classified the shale samples by the thermal maturity and employed the temperature to model the Langmuir pressure; the temperature is the only considered factor in the model of the Langmuir pressure by Liu, Chen [13], while the content of clay minerals, illite, feldspar, and carbonate was used by Li, Tian [12]. To assess the methane adsorption capacity in shales, it is required to establish a prediction model based on representative data and proper factors

Materials

Results and Discussion

Model of Langmuir Volume at Experimental Temperature

TheThe relationship between the measured and predicted

Conclusions