The Performance Evaluation and Field Application of Low Temperature Coalbed Gas Clean Fracturing Fluid

Jianhan Xu,Bin Liu,Shoucheng Wen,Jiao Ka,Jidan Tang

doi:10.4236/ojogas.2018.34020

Abstract

Clean fracturing fluid has many advantages, such as strong sand carrying capacity, strong ability to high generation and low friction, etc. However, the temperature of coalbed gas in the shallow part is low (25°C to 35°C). And there are no liquid hydrocarbons or no large amount of free water in the reservoir, which can make fracturing fluid break. The difficulty to break the clean fracturing fluid could result in serious reservoir damage during fracturing. This paper introduces many breakers for cleaning fracturing fluid. And the performances of those breakers have been evaluated in the condition of low temperature. On the base of research, the breaker for clean fracturing fluid is recommended for coalbed gas in the shallow part. The breaker can break clean fracturing fluid completely in low temperature of 25°C. At the same time, the degree of damage caused by fracturing fluid is evaluated. The damage rate of fracturing fluid is only 11%. The system of cleaning fracturing fluid has been applied in Qinshui Basin of Shanxi Province. The field experiment has achieved good results.

Highlights

Fracturing is an important measure to improve the productivity of unconventional reservoirs such as coalbed methane and shale gas
Present, there are three kinds of fracturing fluids being applied in the field, such as active water fracturing fluid, polymer fracturing fluid and viscoelastic surfactant fracturing fluid
The concept of recessive breaker is introduced in the system, so that the fracturing fluid is completely broken when the CBM reservoir temperature is below 35 ̊C, which solves the problem that the clean fracturing fluid cannot be broken in the fracturing process because of lack of free water or liquid hydrocarbon, especially under the low temperature in coalbed gas in the shallow part

Summary

Introduction

Fracturing is an important measure to improve the productivity of unconventional reservoirs such as coalbed methane and shale gas. Clean fracturing fluid is the kind of solution based on viscoelastic surfactant, which has strong shear resistance and good sand carrying capacity. The breaking mechanism of clean fracturing fluid is as follows: The polar material is absorbed on the worm-like micellar network structure, which leads to the reduce of the network structure relaxation time by 3 to 4 nn e other hand, some part chains of the polymer wraps around the surface of the micelle. The concept of recessive breaker is introduced in the system, so that the fracturing fluid is completely broken when the CBM reservoir temperature is below 35 ̊C, which solves the problem that the clean fracturing fluid cannot be broken in the fracturing process because of lack of free water or liquid hydrocarbon, especially under the low temperature in coalbed gas in the shallow part. This system can be used for the CBM reservoir in the shallow part fracturing

Experiment and Discussion of VES Gel Breaker

Formation Damage Assessment

Findings

Field Application

Conclusion