Flow Simulation and Influence Factors Analysis of CO2 Foam Fracturing in Annulus Injection

Hao Li,Genbo Peng

doi:10.3389/feart.2021.807788

Abstract

CO2 foam fracturing fluid is widely used in unconventional oil and gas production because of its easy flowback and low damage to the reservoir. Nowadays, the fracturing process of CO2 foam fracturing fluid injected by coiled tubing is widely used. However, the small diameter of coiled tubing will cause a large frictional pressure loss in the process of fluid flow, which is not beneficial to the development of fracturing construction. In this paper, the temperature and pressure calculation model of gas, liquid, and solid three-phase fluid flow in the wellbore under annulus injection is established. The model accuracy is verified by comparing the calculation results with the existing gas, solid, and gas and liquid two-phase model of CO2 fracturing. The calculation case of this paper shows that compared with the tubing injection method, the annulus injection of CO2 foam fracturing fluid reduces the friction by 3.06 MPa, and increases the wellbore pressure and temperature by 3.06 MPa and 5.77°C, respectively. Increasing the injection temperature, proppant volumetric concentration, and foam quality will increase the wellbore fluid temperature and make the CO2 transition to the supercritical state while increasing the mass flow rate will do the opposite. The research results verify the feasibility of the annulus injection of CO2 foam fracturing fluid and provide a reference for the improvement of CO2 foam fracturing technology in the field.

Highlights

With the development of the economy, the exploitation of conventional oil and gas resources has been unable to meet the energy consumption required by scientific and technological progress
In the design of fracturing parameters, reducing the injection mass flow rate, increasing the injection temperature, proppant volumetric concentration, and foam quality, CO2 can be transformed into a supercritical state in a shallow well depth to improve the fracturing effect
The proppant volumetric concentration, foam quality, injection temperature, and geothermal gradient are positively correlated with the temperature, while the injection flow rate is negatively correlated with the temperature

Summary

INTRODUCTION

With the development of the economy, the exploitation of conventional oil and gas resources has been unable to meet the energy consumption required by scientific and technological progress. Through analysis of the influence of six factors on supercritical state, the main factors are proppant volumetric concentration Csf, foam quality Γ, mass flow rate Qw, injection temperature ti and geothermal gradient tg. These five factors are randomly combined to obtain the well depth data when the CO2 foam fracturing fluid reaches the critical temperature, as shown, where W is the well depth when the CO2 foam fracturing fluid reaches the critical temperature, m. In the design of fracturing parameters, reducing the injection mass flow rate, increasing the injection temperature, proppant volumetric concentration, and foam quality, CO2 can be transformed into a supercritical state in a shallow well depth to improve the fracturing effect

CONCLUSION

Findings

DATA AVAILABILITY STATEMENT