Coalbed Methane: Current Evaluation Methods, Future Technical Challenges

Clarkson, Christopher R.; Bustin, Marc

doi:10.2118/131791-ms

Cited by 25 publications

(11 citation statements)

References 109 publications

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“…In fractured rock, such as coal, the majority of the surface 276 area exists in the porous matrix blocks (Clarkson and Bustin 2010). It is therefore assumed that the 277 matrix continuum provides all of the adsorption capacity, so that equations (19) and (20) become: 278…”

Section: Chemical Reactions 256mentioning

confidence: 99%

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A dual porosity model of high-pressure gas flow for geoenergy applications

2018

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7This paper presents the development of a dual porosity numerical model of multiphase, 8 multicomponent chemical/gas transport using a coupled thermal, hydraulic, chemical and mechanical 9 formulation. Appropriate relationships are used to describe the transport properties of non-ideal, 10 reactive gas mixtures at high pressure, enabling the study of geoenergy applications such as geological 11 carbon sequestration. Theoretical descriptions of the key transport processes are based on a dual 12 porosity approach considering the fracture network and porous matrix as distinct continua over the 13 domain. Flow between the pore regions is handled using mass exchange terms and the model includes 14 equilibrium and kinetically-controlled chemical reactions. A numerical solution is obtained with a 15 finite element and finite difference approach and verification of the model is pursued to build 16 confidence in the accuracy of the implementation of the dual porosity governing equations. In the 17 course of these tests, the time splitting approach used to couple the transport, mass exchange and 18 chemical reaction modules is shown to have been successfully applied. It is claimed that the modelling 19 platform developed provides an advanced tool for the study of high pressure gas transport, storage and 20 displacement for geoenergy applications involving multiphase, multicomponent chemical/gas 21 transport in dual porosity media, such as geological carbon sequestration. 22

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Section: Chemical Reactions 256mentioning

confidence: 99%

“…Theoretical features relating to the coupled hydraulic, chemical, gas and mechanical 90 behaviour have been included in the formulation presented. An example is the swelling of coal in 91 response to gas adsorption, which can have a considerable feedback effect on the porosity and 92 permeability (Clarkson and Bustin 2010). 93…”

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confidence: 99%

A dual porosity model of high-pressure gas flow for geoenergy applications

2018

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“…The abandonment condition is the minimum reservoir pressure that can be reached through dewatering. To estimate the desorbed gas volume, the Langmuir volumes at initial reservoir pressure and at current pressure need to be measured (Clarkson, 2010).…”

Section: Dewatering and Gas Desorptionmentioning

confidence: 99%

Smart De-Watering and Production System through Real-Time Water Level Surveillance for Coal-Bed Methane Wells

Han

Ling

2015

SPE Digital Energy Conference and Exhibition

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In the past few decades, Coal-Bed Methane (CBM) has become an important source of energy especially in North America. The methane adsorbed within the coal is in a near-liquid state. The open fractures in the cleats are commonly saturated with water. In developing the CBM reservoir, water in the fracture spaces and coal seam must be continuously pumped off from coal seam. This reduces pressure and desorbs gas from matrix.Although operators desire to produce hydrocarbon quickly, a too fast dewatering rate can irreversibly damage matrix desorption process, which can lead to an unfavorable ultimate recovery. Further, the aggressive production rate can potentially release the coal fines and drive them into pump, which increases maintenance effort and cost. Even worse, the de-watering process fluctuates because of the rock porosity and permeability changes resulting from the brittle coal seam and pressure reduction. Therefore, it is critical to adjust the pump operating parameters in a timely manner to maintain a continuous/intermittent production.The 10 CBM wells at study locate in a mountain with difficult access. Previously engineers had to evaluate well performance and optimize the pump on-site, which is limited by a monthly basis. We firstly developed an automatic data processing system using the advanced Echosounders, which can measure the water level in real time. The reservoir pressure can be then monitored dynamically through interpreting the detected water level. With an automatic-wireless data transferring system installed on-site and a closed-loop control program to receive, process, and interpret data, the pump operating parameters can be changed in real time through remote control. This system not only identifies the downhole problems in real time, but also reduces the pump maintenance frequency from 40 days to 75 days statistically and numbers of trip to well site. Further, the gas production rate has been averagely improved by 30% for the 10 wells.The authors firstly developed an automation data processing and control system in the favor of advanced echosounders. Based on the interpreted reservoir pressure, we can avoid aggressive production by adjusting the pump operating parameters in real time, which eventually results in a better ultimate recovery. The developed workflow (automatic echosounder data acquisition, real filed data transferred to central office, data processing, interpretation, and simulation in computational system, adjustment commands to operating system) is especially valuable for the locations difficult to access.

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“…In a CSG well, once critical desorption pressure is achieved, mine gas will be desorbed from the matrix and flow upward in the annulus, which causes new problems such as violent degassing, foaming and noise from the high gas rate for annular liquid level determination [20]. For the violent degassing and foaming condition, McCoy et al have introduced a mathematical formulae method of foam-free liquid level determination based on surface acoustic liquid level by measuring data acquired within the narrow time window available for closing the casing valves [21].…”

Section: Introductionmentioning

confidence: 99%

A Novel Acoustic Liquid Level Determination Method for Coal Seam Gas Wells Based on Autocorrelation Analysis

Zhang

Fan

et al. 2017

Energies

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Abstract:In coal seam gas (CSG) wells, water is periodically removed from the wellbore in order to keep the bottom-hole flowing pressure at low levels, facilitating the desorption of methane gas from the coal bed. In order to calculate gas flow rate and further optimize well performance, it is necessary to accurately monitor the liquid level in real-time. This paper presents a novel method based on autocorrelation function (ACF) analysis for determining the liquid level in CSG wells under intense noise conditions. The method involves the calculation of the acoustic travel time in the annulus and processing the autocorrelation signal in order to extract the weak echo under high background noise. In contrast to previous works, the non-linear dependence of the acoustic velocity on temperature and pressure is taken into account. To locate the liquid level of a coal seam gas well the travel time is computed iteratively with the non-linear velocity model. Afterwards, the proposed method is validated using experimental laboratory investigations that have been developed for liquid level detection under two scenarios, representing the combination of low pressure, weak signal, and intense noise generated by gas flowing and leakage. By adopting an evaluation indicator called Crest Factor, the results have shown the superiority of the ACF-based method compared to Fourier filtering (FFT). In the two scenarios, the maximal measurement error from the proposed method was 0.34% and 0.50%, respectively. The latent periodic characteristic of the reflected signal can be extracted by the ACF-based method even when the noise is larger than 1.42 Pa, which is impossible for FFT-based de-noising. A case study focused on a specific CSG well is presented to illustrate the feasibility of the proposed approach, and also to demonstrate that signal processing with autocorrelation analysis can improve the sensitivity of the detection system.

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Coalbed Methane: Current Evaluation Methods, Future Technical Challenges

Cited by 25 publications

References 109 publications

A dual porosity model of high-pressure gas flow for geoenergy applications

A dual porosity model of high-pressure gas flow for geoenergy applications

Smart De-Watering and Production System through Real-Time Water Level Surveillance for Coal-Bed Methane Wells

A Novel Acoustic Liquid Level Determination Method for Coal Seam Gas Wells Based on Autocorrelation Analysis

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