Effect of the vertical stress on CO₂ flow behavior and permeability variation in coalbed methane reservoirs

Abstract

Given that in situ stress evolution is of great importance in characterizing coalbed methane reservoirs during gas production, CO2 sequestration, and reservoir fracturing, a series of laboratory measurements were conducted to investigate the role of the vertical stress on gas flow behavior and permeability evolution of San Juan Basin coal. Due to the difficulty in maintaining a steady‐state flow when testing coals with tight structure, the pressure transient technique was employed and experiments were conducted under different boundary conditions: uniaxial strain condition and lateral stress‐controlled condition. The results indicated that the vertical stress has a negative role in permeability enhancement. To verify this finding, one more set of experiments under the vertical stress‐controlled condition was carried out. In addition, the application of CO2 injection on reservoir fracturing was theoretically analyzed. The results indicated that both CO2 injection and the vertical stress can exert positive effects on reservoir fracturing. This study contributes to the understanding of the effect of the vertical stress on permeability variation during CO2 injection, which has practical significance for permeability modeling and reservoir fracturing operation in the field.

Monitoring and correction of the stress in an anchor bolt based on Pulse Pre‐Pumped Brillouin Optical Time Domain Analysis

“…Bolts are vital to the advancement of underground excavation in engineering work, such as subway tunnels and coal mines, as they connect broken rock mass, enhance the stability of underground coal mine roadways and surrounding rock, and reduce the occurrence of rock burst . In countries such as China where huge amount of coal is mined, problems of roof falling (roof collapse), land subsidence, and collapse result in a series of secondary disasters, directly threatening production, and life safety . Monitoring and evaluation of the anchoring performance is an important basis to judge the effectiveness of bolts, and hence, to ascertain the safety of the underground coal mine roadways.…”

Study on the Mechanism and Control of Rock Burst of Coal Pillar under Complex Conditions

“…In the effect detection method, the microseismic monitoring system, acoustic emission monitoring system, and electromagnetic emission monitoring system can process the vibration signal, acoustic signal, and electromagnetic radiation signal to reflect the degree of deformation, fracture, and energy release in the coal and rock mass [25][26][27][28][29][30]. The drilling television system can directly reflect the effect of roof cutting and precracking after blasting [31,32].…”

Large Deformation Mechanics of Gob‐Side Roadway and Its Controlling Methods in Deep Coal Mining: A Case Study

“…Many scholars have investigated the instability mechanism of deep mining roadways and stability control techniques for surrounding rocks [45][46][47][48][49][50][51][52][53][54]. However, the research on the large deformation controlling method of gob-side roadway occurring in the deep coal mine is still needed, including the mechanical model of the gob-side roadway and the methods to deal with this unfavourable displacement.…”