Enhanced Coalbed Methane Recovery Research Articles

Coal characterization for ECBM recovery: Gas sorption under dry and humid conditions, and its effect on displacement dynamics

Enhanced Coal Bed Methane (ECBM) recovery is a technique under investigation as a possible approach to the geological storage of CO2 in a carbon dioxide capture and storage (CCS) system. This technology allows enhancing the recovery of coal bed methane by injecting CO2 in the coal seam at supercritical conditions. Through an in situ sorption/desorption process the displaced methane is produced and the adsorbed CO2 is permanently stored. In the case of coal, the uptake of CO2, CH4 and N2 is a combination of adsorption on its surface and penetration (absorption) into its solid matrix, the latter resulting in coal’s swelling. These two processes act simultaneously, making the coal a challenging material to be studied, in particular with respect to the understanding of the fundamental aspects of gas adsorption. High pressure sorption data of CO2, CH4 and N2 on a coal sample from Australia are presented; the interpretation of the experimental data takes into account the dual nature of the sorption process and a Langmuir-like model is applied to the sorption data, by fitting the isotherm parameters to the experimental values. The results confirm that this equation is a valuable option to describe gas sorption on coal. Moreover, a one-dimensional mathematical model previously derived is used to perform numerical simulations on the performance of ECBM recovery in coal beds. Important insights are obtained regarding the gas flow dynamics during displacement and the effects of gas sorption on the ECBM operation.

Implementation of horizontal well CBM/ECBM technology and the assessment of effective CO2 storage capacity in a Scottish coalfield

In this study the theoretical and effective methane recovery and CO2 storage potential of four coal seams within a well characterised section of a CBM license in Scotland are estimated, considering different horizontal well patterns, the effect of permeability heterogeneity and the composition of the injected fluid. The study concerns the Airth area of the Clackmannan coalfield in the Scottish Midland Valley. The effort on building the static earth model and the history match results of the pre-existing vertical and newly drilled horizontal wells is briefly described. Initial simulations of the horizontal well primary methane production and CO2/flue gas enhanced recovery enabled the length, configuration and alignment of the horizontal wells to be optimised for the long-term simulations. This configuration was then used to estimate the Effective Capacity of a selected area within the Airth field for CBM, ECBM and CO2 storage. To evaluate the impact of permeability heterogeneity and uncertainty on reservoir performance and Effective Capacity for methane recovery and CO2 storage, multiple realisations of possible permeability distributions across the selected area were geostatistically generated. Initially, primary production runs were performed using 100 permeability distributions with a median value of around 1 mD. A number of realisations with different median permeabilities were then selected and used for flue gas (13 % CO2/87 % N2) and mixed gas (50 % CO2/50 % N2) enhanced CBM recovery and CO2 storage runs.

2-1-2 Proposal on Combined System of Enhanced CBM Recovery and CO2 Storage in Coal-bearing Formation : Part 2, Case Study

2-1-2 Proposal on Combined System of Enhanced CBM Recovery and CO2 Storage in Coal-bearing Formation : Part 2, Case Study

2-1-1 Proposal on Combined System of Enhanced CBM Recovery and CO2 Storage in Coal-bearing Formation : Part 1, Simulator Development

2-1-1 Proposal on Combined System of Enhanced CBM Recovery and CO2 Storage in Coal-bearing Formation : Part 1, Simulator Development

Simulation of CO2-geosequestration enhanced coal bed methane recovery with a deformation-flow coupled model

Coal bed methane (CBM) recovery and CO2 sequestration into coal seams coupled with enhanced CBM recovery have been recognized as an economically effective and environmentally friendly technology to improve the utilization of coal reserves. However, implementation of CBM and CO2 enhanced CBM (CO2-ECBM) production involves complex deformation-flow interactions in the coal. These aspects and their fundamental understanding remain as major concerns for CBM/ECBM modeling. Increasing interest in CBM and potentially in CO2-ECBM technology requires accurate predictive modeling to minimize investment risks. This paper proposed a deformation-flow coupled model to address aspects of model improvement. This model was developed based on nonlinear elastic deformation mechanics and gas percolation theory and implemented using an established computer program named F-RFPA2D - 2D Flow-coupled Rock Failure Process Analysis code. The numerical simulations of this model were carried out according to a CO2 capture and sequestration (CCS) integrated underground coal gasification (UCG) process designed for Zhongliangshan coal mine in southwest China. The individual operations comprising (1) conventional CBM recovery and CO2 sequestration into coal and (2) the integrated operation of CBM recovery with CO2 enhancement were numerically investigated, respectively. The results show that CO2 sequestration into the coal bed promotes rapid transport of CBM towards the gas producer wells with a longer production period and can enhance coal bed methane recovery by up to 80% under the conditions of using this this study.

Enhanced Coalbed Methane Recovery with Respect to Physical Properties of Coal and Operational Parameters

Abstract Modelling desorption-controlled reservoirs is a difficult matter owing to the complex nature of hydrocarbon transport processes. The complexity of enhanced coalbed methane (ECBM) recovery is not only caused by desorption-controlled behaviour of coalbed reservoirs, but also the interaction between coal media and the injected CO2/N2 gas mixture, which changes the coal properties with respect to injection time. In addition, the characterization of coal reservoirs and the determination of in situ coal properties related to the transport mechanism of methane are complicated, as there is a lack of standard procedures in the literature. In considering these difficulties, this study took the approach that relationships between rank and physical properties of coal be used for evaluation purposes. Parametric simulation studies with rank classification provided more representative results for coal reservoirs rather than univariate analysis. Besides coal rank, simulation cases were run for different reservoir types, well patterns, molar compositions of injected fluid and well types. The shrinkage/swelling process was taken into account by making use of the extended Palmer/Mansoori model. As a result, ECBM recovery was studied in field-scale with rank-dependent coal properties and different operational parameters in order to provide an overview. Introduction In the literature, there are parametric simulation studies(1–3) investigating the effect of each coal property on primary and enhanced coalbed methane recoveries. The trend has been generally to change a model parameter in a given range and to observe its impact on total methane recovery. In our previous study, however, a new approach was followed during preparation of input data for a commercial compositional simulator: Computer Modelling Group's GEM module(4, 5). Instead of using a real field or a hypothetical data set, rank-dependent coal properties in the literature were gathered to create a database. This database enabled us to acquire more realistic outputs from the simulator. In this paper, however, the rank-dependent database was used to simulate the effects of different coal properties and operational parameters on ECBM recovery. The following section gives information about these cases. Simulation Cases In this study, four different vertical well cases were run to observe the behaviour of our data set(5). In addition, horizontal well cases were simulated and compared to vertical well cases. All simulations started with the primary recovery of methane (CBM) which takes 10 years. After 10 years, the ECBM recovery technique was used for all cases except the methane-saturated dry coal case. The aim of 10 years primary recovery is to decrease the water saturation in the cleat system and to increase the relative permeability of the gas before the injection of the CO2 or CO2/N2 mixture. As there is initially no water in the fractures of methane-saturated dry coals, ECBM recovery is applied at the beginning. As for other modelling parameters, depth and thickness of the coal seam are taken as 915 m (3,000 ft) and 6.1 m (20 ft), respectively. The average geothermal gradient is about 2.5 to 3 °C/100 m. Initial reservoir temperature is calculated as 45 °C.

8-6-2 コールベッドメタンの分子モデリング(8-6 エネルギー需給1,Session 8 エネルギー評価・経済(エネルギー学含む),研究発表)

8-6-2 コールベッドメタンの分子モデリング(8-6 エネルギー需給1,Session 8 エネルギー評価・経済(エネルギー学含む),研究発表)

A Multicomponent, Two-Phase-Flow Model for CO2 Storage and Enhanced Coalbed-Methane Recovery

Summary Injection of CO2 into deep unminable coal seams is an option for geological storage of CO2. Moreover, injection of CO2 may enhance the recovery of CH4 in these systems, making coal reservoirs interesting candidates for sequestration. New analytical solutions are presented for two-phase, three-and four-component flow with volume change on mixing in adsorbing systems. We analyze the simultaneous flow of water and gas containing multiple adsorbing components. The displacement problem is solved by the method of characteristics. Mixtures of N2, CH4, CO2, and H2O are used to represent enhanced coalbed-methane (ECBM) recovery processes. The displacement behavior is demonstrated to be strongly dependent on the relative adsorption strength of the gas components. In ternary systems, two types of solutions result. When a gas rich in CO2 displaces a less strongly adsorbing gas (such as CH4), a shock solution is obtained. As the injected gas propagates through the system, CO2 is removed from the mobile phase by adsorption, while desorbed gas propagates ahead of the CO2 front. The adsorption of CO2 reduces the flow velocity of the injected gas, delaying breakthrough and allowing for more CO2 to be sequestered per volume of CH4 produced. For injection gases rich in N2, a decrease in partial pressure is required to displace the preferentially adsorbed CH4 and a rarefaction solution results. In quaternary displacements with injection-gas mixtures of CO2 and N2, the relative adsorption strength of the components results in solutions that exhibit features of both the N2-rich and CO2-rich ternary displacements. Analytical solutions for ECBM recovery processes provide insight into the complex interplay of adsorption, phase behavior, and convection. Improved understanding of the physics of these displacements will aid in developing more efficient and physically accurate techniques for predicting the fate of injected CO2 in the subsurface.

Economic assessment of enhanced Coalbed Methane recovery for low rank coal system

Abstract Enhanced Coalbed Methane Recovery (ECBMR) is usually targeted for the bituminous coals, for the methane content in such coals is rather high and it leads to the higher profit by methane sales. Generally, methane content of low rank coals is small. However, adsorption ratio of CO 2 /CH 4 is high for low rank coal. It suggests that the CO 2 adsorption volume of low rank coal is large. Moreover, some low rank coal seams have high permeability. Low rank coal seams have advantage of high CO 2 adsorption volume and high permeability, and disadvantages of low methane content, possibility of large swelling from the viewpoint of ECBMR. When the carbon credit is expected, CO 2 storage in low rank coal systems is very promising due to their high CO 2 storage capacity. At the same time we must consider negative effect of CO 2 storage on the decrease of permeability caused by large swelling (CO 2 adsorption). A case study of economic assessment was made for low rank coal seams with sensitivity analysis. Well type of five spot patterns was employed. Well spacing, CO 2 concentration of injected gas and carbon credit is the parameter of sensitivity analysis. The results showed CO 2 concentration was the most important factor to determine the economy of the project affecting the permeability and the CO 2 storage rate. By selecting the optimum CO 2 concentration of the injected gas, the low rank coal would be one of the options for underground CO 2 storage under certain carbon credit.

Modeling of ECBM recovery from Amasra coalbed in Zonguldak Basin, Turkey

Zonguldak coal basin is the only productive hard coal basin of Turkey. The eastern part of the basin is called as Bartin–Amasra District, which has deeper coal seams. The depth and difficulty of mining these coal seams make this district an important candidate for coalbed methane (CBM) recovery. However, there is not enough reservoir data for modeling purposes. In this study, the lithologic information collected for coal mining industry was used to determine the correlations and the continuity of the coal seams. The lithologic information was examined and the depths of the coal seams and the locations of the exploration boreholes were used to perform a reliable correlation using a new method. As a result of the correlation study, 63 continuous coal layers were found. A statistical reserve estimation of each coal layer for methane was made by using Monte Carlo simulation method. The initial methane in place found in the coal layers both in free and adsorbed states were estimated using probabilistic simulations resulted in possible reserve (P10) of 2.07 billion m3, probable reserve (P50) of 1.35 billion m3 and proven reserves (P90) of 0.86 billion m3. Among the determined continuous coal layers, coal layer #26 was selected for a preliminary investigation of the applicability of enhanced coalbed methane (ECBM) recovery and CO2 storage. The scarcity of coal seam reservoir data required a sensitivity study for the effects of reservoir parameters on operational performance indicators. The effects of adsorption, coal density, permeability, cleat porosity and permeability anisotropy parameters were examined using the Computer Modeling Group's (CMG) GEM module.

Mechanism of CO2 enhanced CBM recovery in China: a review

Abstract Permeability of coal reservoirs in China is in general low. Injection of CO 2 into coal seams is one of the potential approaches for enhancing coalbed methane (CBM) production. The feasibility of this technology has been investigated in China since the 1990s. Advances in mechanism of CO 2 enhanced CBM recovery (CO 2 -ECBM) in China are reviewed in light of certain aspects, such as the competitive multi-component gas adsorption, sorption-induced coal swelling/shrinkage and its potential effect on CBM production and numerical simulation for CO 2 -ECBM recovery. Newer investigations for improving the technology are discussed. It is suggested that a comprehensive feasibility demonstration in terms of geology, technology, economics and environment-carrying capacity is necessary for a successful application of the technology for CBM recovery in China. The demonstration should be carried out after more investigations into such facets as the control of coal components and structure to a competitive multi-component-gas adsorption, the behavior and essence of supercritical adsorption by coal of gas, environmental and safe feasibility of coal mining after CO 2 injection and more extensive pilot tests for CO 2 -ECBM recovery.

Flue-Gas Carbon Capture on Carbonaceous Sorbents: Toward a Low-Cost Multifunctional Carbon Filter for “Green” Energy Producers

A low-pressure Carbon Filter Process (patent pending) is proposed to capture carbon dioxide (CO2) from flue gas. This filter is filled with a low-cost carbonaceous sorbent, such as activated carbon or charcoal, which has a high affinity (and, hence, high capacity) to CO2 but not to nitrogen (N2). This, in turn, leads to a high CO2/N2 selectivity, especially at low pressures. The Carbon Filter Process proposed in this work can recover at least 90% of flue-gas CO2 of 90%+ purity at a fraction of the cost normally associated with the conventional amine absorption process. The Carbon Filter Process requires neither expensive materials nor flue-gas compression or refrigeration, and it is easy to heat integrate with an existing or grassroots power plant without affecting the cost of the produced electricity too much. An abundant supply of low-cost CO2 from electricity producers is good news for enhanced oil recovery (EOR) and enhanced coal-bed methane recovery (ECBMR) operators, because it will lead to higher oil and gas recovery rates in an environmentally sensitive manner. A CO2-rich mixture that contains some nitrogen is much less expensive to separate from flue-gas than pure CO2; therefore, mixed CO2/N2-EOR and CO2/N2-ECBMR methods are proposed to maximize the overall carbon capture and utilization efficiency.

A Review on Recent Advances in the Numerical Simulation for Coalbed-Methane-Recovery Process

Summary The recent advances in numerical simulation for primary coalbed methane (CBM) recovery and enhanced coalbed-methane recovery (ECBMR) processes are reviewed, primarily focusing on the progress that has occurred since the late 1980s. Two major issues regarding the numerical modeling will be discussed in this review: first, multicomponent gas transport in in-situ bulk coal and, second, changes of coal properties during methane (CH4) production. For the former issues, a detailed review of more recent advances in modeling gas and water transport within a coal matrix is presented. Further, various factors influencing gas diffusion through the coal matrix will be highlighted as well, such as pore structure, concentration and pressure, and water effects. An ongoing bottleneck for evaluating total mass transport rate is developing a reasonable representation of multiscale pore space that considers coal type and rank. Moreover, few efforts have been concerned with modeling water-flow behavior in the coal matrix and its effects on CH4 production and on the exchange of carbon dioxide (CO2) and CH4. As for the second issue, theoretical coupled fluid-flow and geomechanical models have been proposed to describe the evolution of pore structure during CH4 production, instead of traditional empirical equations. However, there is currently no effective coupled model for engineering applications. Finally, perspectives on developing suitable simulation models for CBM production and for predicting CO2-sequestration ECBMR are suggested.

Fundamental Mechanisms Involved in Enhanced Coal Bed Methane Recovery for CO2 Storage

Fundamental Mechanisms Involved in Enhanced Coal Bed Methane Recovery for CO₂ Storage

Study of Parameters Affecting Enhanced Coal Bed Methane Recovery

Laboratory and field scale trials conducted so far indicate that injection of CO2 and N2 into deep coalbeds has the potential to enhance coalbed methane (ECBM) recovery while simultaneously sequestering CO2. The work has identified that the fundamental processes involved in CO2 sequestration/CBM recovery in deep coalbeds are not fully understood and further research is needed to advance this technology. ECBM is affected by several parameters; prominent among them are coal characteristics, in-situ conditions prevailing in deep coalbeds, and changes arising from the interaction of coal with various fluids. These parameters do not act independently, thereby making it difficult to isolate their impacts separately. An attempt has been made in this article to classify these parameters and understand their role in ECBM. Past work in this area is reviewed and the future work that is critical for an improved understanding of ECBM recovery is discussed.

Overview: Unconventional Recovery (August 2006)

I was inspired by a recent broadcast of All Things Considered on Natl. Public Radio and began to think of our industry and what could possibly make a difference in the world—if we, like Bill Gates, had an optimistic belief in technology and management combined with the vast resources of the petroleum industry. Is it possible for us to eliminate some of the top energy-related "diseases"? The production of greenhouse gases certainly would be high on the list, regardless of whether you believe it is responsible for the recent global-warming trend. (Most of us would agree that it is at least a contributing factor.) So, is it "naïve overreaching" to think that we can affect such a gargantuan problem with current or near-future technology? I think we can help. In this issue, the focus is on technologies that hold at least a promise of a solution, either by offering an alternative to dirtier fuels or by eliminating or reducing some greenhouse gases directly. Although expensive to produce and technologically challenging, coalbed methane (CBM) is a clean-burning fuel with tremendous potential for replacing some of the more conventional and "dirtier" resources. CBM is found in nearly every sedimentary basin, and current production is limited only by economics, which is negatively affected by water disposal and low production rates. New advances in recovery methods, such as the use of horizontal production and injection wells, could yield huge increases in CBM production. CO2 storage in deep underground reservoirs is not a new idea, but until recently, very little was known about the storage capacity and viability of such a practice. Recent computer modeling has led to an increased understanding of the trapping mechanisms and suggests optimal injection practices. CO2 sequestration in gas hydrates may offer a viable long-term storage solution while liberating methane gas to use as fuel. Although still in its infancy, this unconventional technology holds tremendous potential for the industry—and the environment. I hope you will enjoy reading these paper highlights; and with an optimistic belief in our technology and management and with our vast resources, I know we can make a difference! Unconventional Recovery additional reading available at the SPE eLibrary: www.spe.org SPE 100021 "A Screening Model for CO2 Flooding and Storage in Gulf Coast Reservoirs Based on Dimensionless Groups" by D.J. Wood, U. of Texas at Austin, et al. SPE 100584 "Evaluation of the Technical and Economic Feasibility of CO2 Sequestration and Enhanced Coalbed-Methane Recovery in Texas Low-Rank Coals" by G.A. Hernandez, SPE, Texas A&M U., et al. SPE 97266 "Depressurization-Induced Gas Production From Class 1 Hydrate Deposits" by G.J. Moridis, SPE, Lawrence Berkeley Natl. Laboratory, et al.

Techbits: Coalbed-Methane Recovery and CO2 Sequestration Raise Economic, Injectivity Concerns

Representing Australia, the U.S., Canada, and Europe, 40 engineers and geologists attended an SPE Applied Technology Workshop (ATW) focused on the viability of enhanced coalbed-methane (ECBM) recovery and CO2 sequestration in coalbeds. The workshop “Enhanced Coalbed-Methane Recovery and CO2 Sequestration,” held in Denver from 27–29 October 2004, was led by Scott Reeves, Executive Vice President of Advanced Resources Intl., and the program committee included Bill Gunter, Research Officer of the Alberta Research Council; Mike McGovern, Senior Staff Engineer of Burlington Resources; Henk Pagnier, Program Manager-SUS Energy, TNO-Netherlands Inst. of Applied Geosciences; and Pablo Tejera Cuesta, Reservoir Engineer for Shell Intl. E&P. The ATW featured six sessions focusing on different aspects of ECBM recovery and CO2 sequestration, providing an excellent snap-shot of research and pilot programs in this topic area. Session 1, moderated by Reeves, introduced the workshop and reviewed the state of ECBM-recovery technology. During his introduction, Reeves noted that ongoing work in ECBM recovery is very research oriented and is driven by CO2 sequestration. Cuesta continued the session with an introduction to ECBM-recovery technology, stating that coalbed methane is a significant part of the global hydrocarbon resource base. He reviewed the reservoir characteristics of coal (classified as a continuous-type reservoir) in which gas storage is dominated by adsorption. Major points of discussion highlighted economic considerations, including the cost of injectant required for ECBM-recovery operations as well as the separation, capture, and storage of CO2. Lessons Learned Gunter moderated Session 2, focusing on pilot projects and emphasizing results and lessons learned and noting that experience with ECBM recovery and CO2 sequestration in coal includes one large-scale project in the Allison Unit of the San Juan basin and a series of single-well micropilots in Canada, Poland, and China. These pilot programs have focused on coal of bituminous-through-anthracite rank, and major issues being addressed include geomechanics, permeability, matrix swelling, and fracture porosity. McGovern presented the results of CO2 flooding in the Allison Unit, motivated by the desire to recycle CO2 produced from Fruitland coal while enhancing CBM production. Within the Allison Unit, CO2 was injected continuously for more than 5 years. During the project, approximately 4.7 Bcf of CO2 was injected, and approximately 4.2 Bcf of CO2 was sequestered. Incremental methane recovery during the project was approximately 1.5 Bcf, and the ratio of CO2 injected to methane produced was approximately 3.1:1.0. David Law of the Alberta Research Council presented results of micropilot programs in Mannville coal of the Western Canada sedimentary basin and the No. 3 coal of China’s Qinshui basin. In the pilot areas, Mannville coal is of highly volatile B bituminous rank, and the No. 3 coal is of anthracite rank. Well testing in these micropilots included multiple production and injection-falloff tests. The Mannville micropilot is notable because a variety of gases were injected, including pure CO2, flue gas, pure N2, and CO2-enriched flue gas. The Qinshui basin contains the first pattern of commercial CBM wells drilled in China and contains the highest-rank coal developed for CBM to date. Well testing in the Qinshui basin confirms that sequestration potential exists in anthracite and that permeability can exceed 12 md.

Enhanced Coalbed-Methane Recovery by Use of CO2

This article is a synopsis of paper SPE 48881, "Enhanced Coalbed-Methane Recovery Using CO2 Injection: Worldwide-Resource and CO2- Sequestration Potential," by Scott H. Stevens, SPE, and Denis Spector, Advanced Resources Intl. Inc., and Pierce Riemer, IEA Greenhouse Gas R&D Programme, originally presented at the 1998 SPE International Oil and Gas Conference and Exhibition in China, Beijing, 2-6 November.