Experimental analysis on the effect of tectonically deformed coal types on fines generation characteristics

Zheng, Youye; Cao, Daiyong; Wei, Yingchun; Li, Xiaoming; Wang, Xiaoliang; Zhang, Xiaoyu

doi:10.1016/j.petrol.2016.05.041

Cited by 60 publications

(33 citation statements)

References 24 publications

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“…These fines have detrimental impacts on CSG production, such as formation damage and pump failures (Marcinew and Hinkel, 1990;Nimerick et al, 1990). A small portion of coal fines naturally exists in virgin coal cleats; while a large portion is generated mainly by fluid flushing and pressure disturbance (Yao et al, 2016). During the CSG production process, when different flow regimes take place (e.g.…”

Section: Accepted Manuscript 1 Inmentioning

confidence: 99%

Experimental investigation on the impact of coal fines generation and migration on coal permeability

Bai

Chen

Aminossadati

et al. 2017

Journal of Petroleum Science and Engineering

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Measurements of the coal fines production and the impact of these fines on the permeability of two coals from the Bowen Basin, Australia, were performed at different flow conditions (single-phase water or gas, two-phase water and gas) and pressure conditions. The fines collected from each coal samples ranged in size from 1 µm to 14 µm. For both coal samples, during the first 50 hours, the permeability decreases from 0.005 mD and 0.048 mD by 60.9% and 85%, respectively, followed by gradual decline with fluctuations. By the end of water injection, the permeability drops by 88% and 89%, respectively. This phenomenon is attributed to the counteraction between formation damage (cleats plugging and coal fines settlement) and breakthrough of coal fines from the samples (widened cleats). It was found that coal fines volumetric production is proportional to the third power of flow velocity once the flow paths for coal fines are established. The critical flow velocities of coal fines production for both samples were also obtained. For hydrophobic coal, water-drive-gas two-phase flow introduces abrupt permeability loss due to coal fines generation and migration. Furthermore, pauses (well shut-in) in the experiments cause slight permeability drops. A comparison between the two samples indicates that narrower and less connected cleating system results in more frequent coal fines generation and migration, resulting in significant permeability fluctuations with general decreasing trend. Tortuosity of the cleats can enhance the deterioration in permeability by coal fines behaviours. This study delivers fundamental understandings of coal fines generation and migration during the CSG production process, and useful guidelines are suggested to be implemented in the field to minimize production loss induced by coal fines behaviours.

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Section: Accepted Manuscript 1 Inmentioning

confidence: 99%

Experimental investigation on the impact of coal fines generation and migration on coal permeability

Bai

Chen

Aminossadati

et al. 2017

Journal of Petroleum Science and Engineering

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“…Researches including theory modeling, experiment exploration and production analysis have established the fundamental of coal fine generation in coal (Han et al 2015;Yao et al 2016). The generation mechanism of coal fine during drilling, fracturing and CBM production has been well summarized, and its impacts on production performance of CBM wells have also been preferably considered.…”

mentioning

confidence: 99%

Modeling of Coal Fine Migration During CBM Production in High-Rank Coal

Zhu

Peng

et al. 2017

Transp Porous Med

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During CBM (coalbed methane) production, the interaction of coal fracture surface with water flow commonly generates and starts coal fine flow. Part of flowing coal fines deposit in coal fracture system due to water production reduction and methane production increase. The fine sedimentation results in the reduction of coal permeability and well productivity. Despite the increasing awareness of the importance of fine migration, limited research has been carried out on the flow model of coal fine coupled with water and gas. In this paper, a flow model of coal fine is established coupled with water and gas flow, taking coal fine generation, migration and sedimentation process into consideration. Then, case simulations are conducted to illustrate effects of water production schedule, permeability performance and gas content on production performance in flow model. The simulation results indicate that methane rate with the lowest initial water rate is observed to have the highest production in late production period. This is mainly due to the reason that the low water flow cannot generate and start the flow of coal fine. Further, the case with high initial water production has faster gas and water flow rate, thus higher coal fine generation rates, which can improve well productivity at earlier production period. As water production declines quickly, both permeability and production performance decrease, which leads to the loss of well productivity. Meanwhile, higher gas content will lead to a faster water production decline at late production period. This indicates that a portion of coal fines plugged in the fracture as water production deceases and the CBM reservoir with high gas content should not adopt a high initial water production schedule.

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“…Getting a high production of gas from tectonically deformed coal (TDC) is very difficult. The occurrence of TDC has caused many problems, such as poor permeability [3][4][5][6], coal fine blockage and rapid productivity degradation [7,8]. Therefore, the accurate interpretation of TDC zones is of importance in the productivity evaluation of CBM wells.…”

Section: Introductionmentioning

confidence: 99%

Productivity Evaluation of Coalbed Methane Well with Geophysical Logging-Derived Tectonically Deformed Coal

et al. 2019

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Tectonically deformed coal (TDC) has a significant influence on coalbed methane recovery. Well-logging is a reliable and efficient way to predict the development of TDCs for understanding the role of TDC on the productivity of coalbed methane (CBM) wells. However, there has been insufficient research regarding both the static physical properties and dynamic invasion of mud-filtrate related to TDCs. Therefore, a new TDC-detecting approach using two indicators of the relative physical properties and fluid attributes was proposed. Through the data normalization and optimization of correlation coefficients and factor analysis, five logs were chosen to construct the two indicators, and three types of TDC were recognized: I—undeformed or cataclastic; II—granulated; and III—mylonitized. It was found out that the identification error rate decreased from 30% to 15%. Furthermore, the thickness ratio of a well-preserved coal layer derived from TDC interpretation was adopted to correlate the gas production of a coal seam. An application in the Hancheng block demonstrated that the thickness ratio of 60% is an explicit threshold value to distinguish between high-yield well (>1000 m3/d) and low-yield one (<750 m3/d). The development of granulated and mylonitized coals mainly exerts negative influence on CBM well production.

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Experimental analysis on the effect of tectonically deformed coal types on fines generation characteristics

Cited by 60 publications

References 24 publications

Experimental investigation on the impact of coal fines generation and migration on coal permeability

Experimental investigation on the impact of coal fines generation and migration on coal permeability

Modeling of Coal Fine Migration During CBM Production in High-Rank Coal

Productivity Evaluation of Coalbed Methane Well with Geophysical Logging-Derived Tectonically Deformed Coal

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