scholarly journals Prediction of high-quality coalbed methane reservoirs based on the fuzzy gray model: An investigation into coal seam No. 8 in Gujiao, Xishan, North China

2020 ◽  
Vol 38 (4) ◽  
pp. 1054-1081
Author(s):  
Huang Bo ◽  
Qin Yong ◽  
Wanhong Zhang ◽  
Qiming Zheng ◽  
Songlin Shi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Coal Seam ◽  
Coalbed Methane ◽  
Low Permeability ◽  
Gray Model ◽  
High Quality ◽  
The North ◽  
Reservoir Permeability ◽  
Geological Factors ◽  
Coalbed Methane Production

Coalbed methane (CBM) resources are abundant in the Gujiao block, Xishan coalfield, China. However, few studies have been conducted on the coalbed methane geology of the Gujiao block. In the present study, based on logging responses and numerical simulations, the coal structures of coal seam No. 8 of this block were identified, and the mechanical properties of the coal and its roof/floor were calculated. The geological factors influencing the coalbed methane reservoir were quantitatively characterized according to the fuzzy gray model. High-quality coalbed methane reservoirs in the No. 8 coal were predicted and classified using the model, and some suggestions on rational exploitation were determined. Reservoirs of the No. 8 coal are dominated by the III-type, followed by the II- and IV-types. The III-type reservoirs are the most common, and primarily developed at the Xiqu, Zhenchengdi, Malan, and Tunlan coal mines in the north of the studied area. The III-type reservoirs represent low coalbed methane contents, high thickness proportions of granulated-mylonitized coal, and low burial depths. The II-type reservoirs are primarily developed close to the axis of the Malan syncline and in the south and northwest of the studied area, and have low permeability, less significant differences between the mechanical properties of coals and their roofs and floors, and low reservoir pressure gradients. The IV-type reservoirs have a scattered development, dominance of granulated-mylonitized coal, and low permeability, indicating low potential to improve reservoir permeability. Targeted exploitation technology and drainage systems corresponding to the different types of coal reservoirs should be proposed to improve coalbed methane production.

scholarly journals Influence of Migration and Plugging of Nanoparticles on Coal Permeability in Coal Reservoirs

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xiaopeng Zhai ◽  
Weihong Chen ◽  
Yun Xu ◽  
Yishan Lou ◽  
Shuhong Xu ◽  
...  
Keyword(s):  
Pressure Difference ◽  
Coalbed Methane ◽  
Pressure Oscillation ◽  
Working Fluid ◽  
Low Permeability ◽  
Coal Permeability ◽  
The North ◽  
Theoretical Support ◽  
Coal Reservoir ◽  
Selection Of

The plugging of nanopores in low-permeability coal reservoirs is an important factor that affects productivity reduction. However, the mechanism of plugging of the nanopores in coal reservoirs remains unclear. In this study, the coal samples from the Anze coalbed methane block of the North China Oilfield are used as the research object. Experiments are conducted on the mechanism of nanopore plugging by the variation of nanopore permeability based on the pressure oscillation method and the nanopore (scanning electron microscope) method. The research shows that the foreign working fluid invades a coal sample; the sample changes from being hydrophobic to being water absorbent within a certain period. The instability caused by the expansion of coal clay mineral particles promotes the dispersion and shedding of particles, and the migration of particles is accelerated under the shear stress of the working fluid. In addition, the viscosity and pressure difference of the working fluid are important factors that affect particle plugging. The viscosity of the fluid increased by two times, and permeability decreased by 1.21 times. As the pressure difference increases by two times, permeability can be reduced by up to two orders of magnitude. The findings of this study can help for better understanding of the mechanism of plugging of the nanopores in coal reservoirs and the reasons of production reduction in low-permeability coal reservoirs. Such findings provide theoretical support for the selection of the working fluid, and reasonable production pressure difference can effectively reduce the damage on coal permeability in a low-permeability coal reservoir.

Dynamic Variation Character of CBM Reservoir Permeability during Depletion of High-Rank Coalbed Methane

2011 ◽  
Vol 233-235 ◽  
pp. 2267-2271
Author(s):  
Gui Zhong Li ◽  
Ze Deng ◽  
Bo Wang ◽  
Meng Geng
Keyword(s):  
Coalbed Methane ◽  
Geological Structure ◽  
Initial Permeability ◽  
Rapid Decline ◽  
Low Permeability ◽  
Late Development ◽  
Dynamic Variation ◽  
Permian System ◽  
Reservoir Permeability ◽  
Production Wells

China is rich in CBM resources, but so far, some production wells present low production and rapid decline trend. In addition to these objective factors such as low permeability and complexity of geological structure of CBM reservoir, there is still the most important problem during the exploitation techniques that is the lack of understanding to dynamic variation character of CBM reservoir permeability, which leads to the unreasonable work of depletion for coalbed methane.Using P&M model and parameters from 3# coal seam of Shanxi Formation, Permian system in Qinshui basin, the permeability variations of this block (first decline, then ascend, reaching 2.8 times of initial permeability at the end) were analyzed, revealing good depletion prospect of this CBM field, and pointed that the higher Young's modulus is, the more obvious matrix shrinkage is and the higher gas saturation is, the more favor for permeability improvement through sensitivity analysis. Finally, two suggestions were proposed, (1) add the 'permeability variations' to the parameters for CBM block select, which may find the "innate" in the late development of the poor condition of properties easy to improve, develop potential for larger blocks. (2) Adjust and optimize the depletion method (amplitude and frequency of bleeding, pressure reduction) according to the permeability variation characters discussed in this paper

Influence of Coal-Seam Water on Coalbed Methane Production: A Review

2015 ◽  
Vol 51 (2) ◽  
pp. 207-221 ◽  
Author(s):  
Jinxuan Han ◽  
Zhaozhong Yang ◽  
Xiaogang Li ◽  
Jian Zhang
Keyword(s):  
Coal Seam ◽  
Methane Production ◽  
Coalbed Methane ◽  
Coalbed Methane Production

scholarly journals Investigation on the CBM Extraction Techniques in the Broken-Soft and Low-Permeability Coal Seams in Zhaozhuang Coalmine

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Zhaoying Chen ◽  
Xuehai Fu ◽  
Guofu Li ◽  
Jian Shen ◽  
Qingling Tian ◽  
...  
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Coalbed Methane ◽  
Research Result ◽  
Horizontal Stress ◽  
Gas Production ◽  
Vertical Stress ◽  
Low Permeability ◽  
Coal Seams

To enhance the coalbed methane (CBM) extraction in broken-soft coal seams, a method of drilling a horizontal well along the roof to hydraulically fracture the coal seam is studied (i.e., HWR-HFC method). We first tested the physical and mechanical properties of the broken-soft and low-permeability (BSLP) coal resourced from Zhaozhuang coalmine. Afterward, the in situ hydraulic fracturing test was conducted in the No. 3 coal seam of Zhaozhuang coalmine. The results show that (1) the top part of the coal seam is fractured coal, and the bottom is fragmented-mylonitic coal with a firmness coefficient value of less than 1.0. (2) In the hydraulic fracturing test of the layered rock-coal specimens in laboratory, the through-type vertical fractures are usually formed if the applied vertical stress is the maximum principal stress and is greater than 4 MPa compared with the maximum horizontal stress. However, horizontal fractures always developed when horizontal stress is the maximum or it is less than 4 MPa compared with vertical stress. (3) The in situ HWR-HFC hydraulic fracturing tests show that the detected maximum daily gas production is 11,000 m3, and the average gas production is about 7000 m3 per day. This implies that the CBM extraction using this method is increased by 50%~100% compared with traditional hydraulic fracturing in BSLP coal seams. The research result could give an indication of CBM developing in the broken-soft and low-permeability coal seams.

Application of Gravity-Assisted Wellbore Segregation to Wireline Sampling Operations. A Low Permeability Case Study

2021 ◽  
Author(s):  
German Garcia ◽  
Hadrien Dumont ◽  
Tunde Akindipe
Keyword(s):  
Sampling Interval ◽  
High Rate ◽  
Low Permeability ◽  
Sampling Station ◽  
Annular Space ◽  
Low Velocity ◽  
High Quality ◽  
The North ◽  
North Slope Of Alaska ◽  
Recent Developments

Abstract A common challenge in exploration in the North Slope of Alaska is the formation evaluation of low-permeability formations when near-wellbore damage is caused by water-based muds (WBM). This study describes the novel application of existing technology to collect high-quality hydrocarbon samples efficiently in these challenging conditions. The concept was tested with a wireline formation tester in a well with severe formation damage caused by WBM. The procedure and hardware used are discussed and an example of the effectiveness of the proposed technique is shown. Due to the unfavorable mobility ratio, WBM filtrates tends to move preferentially while attempting oil sampling in low permeability rock leading to long station times during wireline formation testing operations. To overcome this challenge, a target sampling interval was subjected to high drawdown using a 3D radial probe to move the target phase closer to the wellbore. Once hydrocarbon was detected in the fluid analyzer, the 3D radial probe was retracted, and the string repositioned to cover the same interval with a straddle packer assembly. Straddle packers provide wellbore annular space for filtrate and hydrocarbon to segregate after the flow period is resumed. When hydrocarbons are again seen in the fluid analyzer, a simultaneous two-pump flow is used to collect them and discard the filtrate. The combination of 3D radial probe and straddle packer assists with displacing the mud filtrate, bringing the target hydrocarbons to the wellbore, and enables the collection of segregated samples with exceptional quality. After pumping at one sampling station using the 3D Radial probe, the maximum hydrocarbon fraction observed was 5%. When the straddle packer was positioned at the same interval, the fluid analyzer showed that the low velocity in the annular space between tool's mandrel and wellbore enabled hydrocarbon segregation from the filtrate due to the existing density contrast. When the hydrocarbon in the wellbore reached the straddle packer inlet, the lower pump was used to flow most of the filtrate in the down direction at high rate. Meanwhile, the hydrocarbon was "skimmed off" and placed in sample containers at a much lower rate using the upper pump. Laboratory results confirmed that the samples collected with the traditional sampling method contained 95% filtrate whereas the samples collected with our technique contained 90% hydrocarbon. Downhole fluid segregation using single-inlet, wireline straddle packer and dual-pump action has not been found in the literature. Recent developments in wireline formation testing use dual inlets in straddle packer modules to enable downhole segregation. We consider that the technique described here innovatively uses the capabilities of current formation testers to collect high-quality hydrocarbon samples in low permeability conditions. With minor adjustments, this technique can also be applied in gas or water sampling in wells drilled with oil-based muds.

Research on the Controlling Factors and Grate Prediction of the Output of Pulverized Coal in Hancheng Block, Eastern Ordos Gas Field

2013 ◽  
Vol 734-737 ◽  
pp. 1460-1463 ◽  
Author(s):  
Xian Yue Xiong ◽  
Dai Yong Cao ◽  
Ming Xun Jie ◽  
Yong Bai ◽  
Xue Shen Zhu ◽  
...  
Keyword(s):  
Coal Seam ◽  
Mechanical Strength ◽  
Coalbed Methane ◽  
Controlling Factors ◽  
Pulverized Coal ◽  
Comprehensive Treatment ◽  
Root Mean Square Amplitude ◽  
Gas Field ◽  
Coalbed Methane Production ◽  
Coal Petrography

According to the 2012s workover treatment statistic in the Hancheng block, the eastern Ordos gas field, the workover caused by pulverized coal accounts for 41.8% of the total, which has seriously affected the continuous and stable drainage. This is one of the main factors which constraint coalbed methane production yield. In this paper, geological factors including the composition of coal petrography, the mechanical strength of coal petrography and coalbody structure destruction and engineering factors including drilling, fracturing and drainage were analyzed to study on the controlling factors on the output of pulverized coal. We conclude that the determinant on output of pulverized coal is the nature of coal seam, however engineering factors cause the output of pulverized coal directly. The root-mean-square amplitude attribute analysis was first used to display the mechanical strength of coal seam. Based on the result, we made the prediction about the possibility of the output of pulverized coal and divided the studying area into four grades. The research on the controlling factors and the prediction of the output of pulverized coal could provide the basis for the prevention and comprehensive treatment of pulverized coal.

scholarly journals A Thermo-Hydro-Mechanical-Chemical Coupling Model and Its Application in Acid Fracturing Enhanced Coalbed Methane Recovery Simulation

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 626 ◽  
Author(s):  
Chaojun Fan ◽  
Mingkun Luo ◽  
Sheng Li ◽  
Haohao Zhang ◽  
Zhenhua Yang ◽  
...  
Keyword(s):  
Coal Seam ◽  
Coalbed Methane ◽  
Coupled Model ◽  
Coupling Model ◽  
Gas Production ◽  
Methane Recovery ◽  
Acid Fracturing ◽  
Enhanced Coalbed Methane Recovery ◽  
Reservoir Permeability ◽  
Enhanced Coalbed Methane

The reservoir permeability dominates the transport of gas and water in coal seam. However, coal seams rich in gas usually contain various pores and fractures blocked by a large amount of minerals, which leads to an ultra-low permeability and gas extraction rate, and thus an increase of drilling workload. We first propose a thermo-hydro-mechanical-chemical coupled model (THMC) for the acid fracturing enhanced coalbed methane recovery (AF-ECBM). Then, this model is applied to simulate the variation of key parameters during AF-ECBM using a 2D geometry. The effect of different extraction schedules are comparatively analyzed to give an insight into these complex coupling responses in coal seam. Result confirms that the AF-ECBM is an effective way to increase the reservoir permeability and improve the gas production using the proposed model. The range of permeability increment zone increases most dramatically in the way of acid fracturing, followed by none-acid fracturing and acidizing over time. The gas production in order is: acid fracturing (AF-ECBM) > fracturing (F-ECBM) > acidification (A-ECBM)> direct extraction (D-CBM).

Analysis of Distribution of Coalbed Methane and Geological Controlling Factors in Huanghebei Mining Area

2013 ◽  
Vol 448-453 ◽  
pp. 3757-3761
Author(s):  
Yan Ru Meng ◽  
Zeng Xue Li ◽  
Hai Yan Liu ◽  
Nan Jiang ◽  
Juan Liu
Keyword(s):  
Coal Seam ◽  
Coalbed Methane ◽  
Mining Area ◽  
Controlling Factors ◽  
Methane Content ◽  
Burial Depth ◽  
Distribution Characteristics ◽  
Deep Well ◽  
Hydrogeological Conditions ◽  
Geological Factors

Distribution characteristics of coalbed methane in Huanghebei mining area were studied and influence of geological factors such as faults, lithology of coal seam roof and floor, magmatic activities, burial depth and upper bedrock thickness of coal seam and hydrogeological conditions on occurrence of coalbed methane were deeply discussed in this paper. Coalbed methane content of mining area increased gradually from southeast to northwest. Coalbed methane in deep well points of mining area is dominated by methane and that in shallow parts contained higher content of nitrogen.

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