Optimization and Field Application of CO2 Gas Fracturing Technique for Enhancing CBM Extraction

Self Cite

Most coal seams in China are characterized by high‐gas pressure and high‐gas content, which seriously threaten the safety of coal mines. Gas extraction is an effective measure for preventing gas disasters. However, the drilling process in soft coal seams is inefficient; it is difficult for the boreholes to reach the design length. The rate of penetration (ROP) plays an important role in determining drilling efficiency and borehole length in soft coal seams. In this study, we establish a simplified ROP model for soft coal seams and evaluate the maximum ROP of Hebi No. 6 coal mine. First, the drill cutting transport capacity of the drilling system and drill cutting quantity generated during the drilling process are analyzed. By simplifying drill cutting transport and coal seam properties, the ROP model is established. Second, the Rock Failure Process Analysis software is used to analyze the deformation region of boreholes, which has a great influence on the drill cutting transport space. Finally, a field test is implemented in Hebi No. 6 coal mine in Henan Province, China, to verify the model, and we propose a measure to control the ROP below the maximum value to increase the length of the borehole. The test results indicate that the model has high accuracy, with errors less than 15%, and the lengths of boreholes in air‐return and transportation roadways are increased to 60 and 80 m, respectively, and the increase rate is greater than 50%.

Section: Introductionmentioning

confidence: 99%

Evaluating the maximum rate of penetration for drilling borehole in soft coal seam

Yang

Wen

Yan

et al. 2020

Self Cite

“…In recent years, the regional gas extraction technologies such as pre-extraction through surface vertical well, 11 surface horizontal well, 12,13 cross-seam boreholes, 14,15 in-seam boreholes, 16 and gas pre-extraction in protected seam 17 have been popularized and applied in different mining areas, which promoted gas extraction, utilization, and production safety of coal mine. Meanwhile, for low-permeability coal seams with high risk of outburst, various stimulation methods such as deep-hole blasting, hydraulic flushing, 15,18,19 hydraulic slotting, [20][21][22] hydraulic fracturing, 23,24 CO 2 fracturing, 25,26 and high-pressure air blasting 27 have been proposed and applied, which could enhance the gas extraction efficiency and shorten the gas extraction period.…”

Section: Introductionmentioning

confidence: 99%

In‐site investigation of regional outburst prevention in coal roadway strip of a deep mine using an improved method

Yang

Wang

Zhang

et al. 2020

Self Cite

“…21,22 Among the depressurizing techniques, the boreholes are preferred in the coal mine industry due to the following reasons. [14][15][16][17][18][19][20][23][24][25] First, it is operationally fast to drill the boreholes; thus, the productivity of longwall mining can be maintained. Other methods usually cause a notable delay of the retreat of longwall panels.…”

Section: Introductionmentioning

confidence: 99%

“…15 This is because the borehole parameters not only affect the effectiveness of the stress transfer but also affect the structural integrity of the surrounding rocks. 14,25 For instance, overspaced boreholes might damage the structural integrity of roadway, resulting in the instability issues. On the contrary, it is less effective to transfer the stresses when the boreholes are insufficiently spaced, which does not reduce the roadway deformation satisfactorily.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Depressurizing boreholes for mitigating large deformation of the main entry

Wang

Zheng

Shen

et al. 2019

The main entries in longwall coal mine frequently encounter large deformation, depending on the stress environment. Depressurizing boreholes are applicable to reduce the large deformation; however, it is difficult to determine the proper parameters (diameter and spacing) for an effective implementation. This study aims to propose feasible design criteria for the quantification of those parameters. We first developed a rigorous numerical model, for a roadway in Zhangshuanglou coal mine, using the rock mechanical properties determined from extensive laboratory measurements and analyses. We then investigated the dependency of the stress transfer and roadway deformation on the ratio of borehole diameter and spacing (D/R and D/I). The symbols of D, R, and I represented the diameter, row spacing, and interspacing of the boreholes, respectively. We found that (a) D/R has to be between 1:6 and 1:2; and (b) D/I has to be between 1:6 and 1:4, for sufficient depressurization in the surrounding rocks. The optimized borehole diameter and spacing parameters were applied in the field where the deformation of roadway was significantly reduced. Finally, we proposed a criterion to determine those parameters of depressurization boreholes for application in other geological and mining conditions.