Numerical Investigation on Wellbore Temperature Prediction during the CO2 Fracturing in Horizontal Wells

Xinrun Lyu,Zhan Meng,Yueying He,Chong Zhang,Shicheng Zhang,Zihan Zhuo

doi:10.3390/su13105672

Abstract

A novel model is established to predict the temperature field in the horizontal wellbore during CO2 fracturing. The pressure work and viscous dissipation are considered, and the transient energy, mass and momentum equations as well as the CO2 physical properties are solved fully coupled. The model passes the convergence test and is verified through a comparison using the COMSOL software. Then, a sensitivity analysis is performed to study the effects of the treating parameters. Results illustrate that the relationship between the injection rate and the stable bottom-hole temperature (hereinafter referred to as BHT) is non-monotonic, which is different from the hydraulic fracturing. The existence of the horizontal section will increase the BHT at 2 m3/min condition but reduce the BHT at 10 m3/min condition. The problem of high wellbore friction can be alleviated through tube size enhancement, and the ultimate injection rate allowed increased from 2.7 m3/min to 29.6 m3/min when the tube diameter increased from 50.3 mm to 100.3 mm. Additionally, the open-hole completion method of the horizontal section can increase the BHT to 2.7 °C but reduce the near formation temperature to 24.5 °C compared with the casing completion method.

Highlights

Shale gas is one of the most important unconventional oil and gas resources [1,2]
Slickwater fracturing and horizontal well drilling are the basic technologies for the development of the shale gas reservoirs [3]
When the injection time was less than 50 min, an increase in the injection rate speeded up the decrease in the temperature

Summary

Introduction

Slickwater fracturing and horizontal well drilling are the basic technologies for the development of the shale gas reservoirs [3]. The usage of the water-based fracturing fluid can generate formation damage and consume a large amount of water resources. Unlike the water-based fracturing fluid, the physical properties of CO2 vary significantly with temperature and pressure [10,11], which can affect the sand-carrying capacity and the performance of the stimulation. It is impractical to modify the CO2 temperature during the fracturing process based on the temperature monitor data because of the expense and time consumed. Accurately predicting the temperature and pressure of the horizontal well CO2 fracturing process is necessary in terms of both the environmental and economic aspects

Methods

Results

Conclusion