An Alternative Approach to Predicting Reservoir Performance in a Coalbed Methane (CBM) Well Flowing Under Dominant Matrix Shrinkage Effect

Upadhyay, Rajeev; Laik, Sukumar

doi:10.1007/s11242-017-0904-2

Cited by 6 publications

(7 citation statements)

References 9 publications

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“…Several studies have established the relationship between coal cleat porosity and pressure by combining coal geomechanics with sorption-induced coal swelling/shrinkage. ,− In this study, the Palmer and Mansoori model is used to relate cleat porosity with pressure. Using matchstick geometry model, a cubic relation can be established between cleat permeability and porosity . Later on, to account for the heterogeneity of the cleat network, Upadhyay and Laik , and Neelu et al incorporated the n th exponent relationship between cleat permeability and porosity. Here, k i and φ i represent the initial cleat permeability and porosity, respectively, and α is a constant given by . The changes in cleat porosity and permeability with pressure depletion as established by eqs and , which lead to pressure-dependent diffusivity, can be accounted for in CBM flow equations by substituting k = αφ n in eq . Neelu et al presented a new pressure-transform, , in the form of stress-dependent adjusted pressure (SDAP) that reduces eq to a single-phase diffusivity equation.…”

Section: Mathematical Modelmentioning

confidence: 99%

A Novel Alternative Method of Compositional Simulation: A Semi-Analytical Approach for Predicting and Evaluating Reservoir Performance of a Multicomponent Coalbed Methane (CBM) Well

Upadhyay,

Kagdi,

Parida

2024

ACS Omega

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Coalbed methane (CBM) reservoirs are naturally fractured formations with cleats surrounding the coal matrix. Analyzing and predicting CBM production performance is challenging because of the complex fracture networks and gas−water two-phase flow, along with the permeability and porosity variation and time-dependent desorption. During depletion, pressure decreases and consequently stress increases, thereby decreasing cleat aperture and permeability, while the matrix shrinkage effect increases cleat width and permeability. The two effects compete with one another, and dominance depends on coal's geomechanical properties and the change in reservoir properties. In addition, though the gas composition from CBM wells predominantly consists of methane, it contains traces of other gases like ethane, carbon dioxide, nitrogen, etc. The combined effects of pressure-dependent diffusivity, time-dependent desorption, and multicomponent sorption in a two-phase flowing CBM well make the flow dynamics in CBM reservoirs complex. A modified semi-analytical mathematical model is developed to characterize the time-dependent desorption and pressure-dependent diffusivity phenomena, also considering the dynamic variation of composition and multicomponent desorption for two-phase flow of CBM wells producing under semi-steady state conditions. The novelty of the model presented in this study lies in manifesting multicomponent sorption effects in the form of an equivalent single-component sorption phenomenon by establishing new transforms. A fully coupled mathematical model is developed that integrates multicomponent sorption effects in CBM reservoirs with pressure-dependent diffusivity and time-dependent desorption effects. The Article presents a new method to intertwine the desorption material balance of individual components with fully coupled flow equations and gives a workflow to predict and evaluate the production performance of a producing CBM well. The study reveals that a multicomponent, two-phase coalbed methane system can be represented in the form of an equivalent single-component singlephase system, thus paving the way for application of CBM flow equations valid for a single phase and single component. The results of the model have been verified using a CMG-GEM numerical simulator as well as in-field production data. This study brings out a novel computational approach for the compositional simulation of the CBM wells, which is unconditionally stable and involves less complexity than commercial simulators, without compromising the accuracy of the results. The findings of this study can help improve the understanding of the complex flow behavior of CBM reservoirs, where multiple phenomena occur simultaneously, like multicomponent sorption, two-phase flow, pressure-dependent diffusion, and time-dependent desorption.

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Section: Mathematical Modelmentioning

confidence: 99%

A Novel Alternative Method of Compositional Simulation: A Semi-Analytical Approach for Predicting and Evaluating Reservoir Performance of a Multicomponent Coalbed Methane (CBM) Well

Upadhyay,

Kagdi,

Parida

2024

ACS Omega

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“…In instantaneous desorption models, the implicit assumption is that the desorption/diffusion process is sufficiently rapid in comparison with the fluid flow through the fractures, and thus, the kinetics of the desorption can be neglected. Upadhyay and Laik , presented a modified method to describe the diffusivity equation for CBM reservoirs in the case of instantaneous desorption.…”

Section: Diffusivity Equation For Two-phase Fluid Flow In the Cbm Res...mentioning

confidence: 99%

“…However, considering the level of heterogeneity of the pore structure within the cleat network, the cubic relationship presents an oversimplification of the geometry. To overcome this aspect, Upadhyay and Laik , incorporated the n th exponent relationship of cleat porosity to permeability. Thus, …”

Section: Diffusivity Equation For Two-phase Fluid Flow In the Cbm Res...mentioning

confidence: 99%

“…Though the model of Burgoyne and Shrivastava made a significant contribution to overcoming the difficulties in reliably characterizing the stress-dependent effects, the model is limited to the formulation of a transport equation in the coal cleats (macropores) only, thus lacking the desorption/diffusion phenomenon in coal matrices. In this regard, Upadhyay and Laik , made some improvements by describing pressure-dependent diffusivity that incorporates the transport phenomenon in both macropores (coal cleats) and micropores (desorption/diffusion in coal matrices). Salmachi et al introduced the approach of permeability ratio function to construct the time-lapse pressure transient analysis.…”

Section: Introductionmentioning

confidence: 99%

“…Salmachi et al introduced the approach of permeability ratio function to construct the time-lapse pressure transient analysis. However, the models presented by Upadhyay and Laik , and Salmachi et al are limited by two aspects – (1) they present an equilibrium desorption model and thus lack the time-dependent desorption characteristics, and (2) they are valid for single-phase flow conditions only.…”

Section: Introductionmentioning

confidence: 99%

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A New Approach to Evaluate and Predict the Reservoir Performance of a Two-Phase Flow Coalbed Methane Well with Fully Coupled Time-Dependent Desorption and Pressure-Dependent Diffusivity Effects

2022

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In coalbed methane (CBM) reservoirs, permeability changes dynamically throughout the life of the reservoir as the pressure depletes due to production. The dynamic variation of coal permeability mainly depends on the combined effect of effective stresses and coal matrix shrinkage caused by gas desorption. Under the conditions of pressure-dependent diffusivity in coal reservoirs, the flow mechanism in CBM reservoirs complicates the solution of the two-phase diffusivity equation. In this study, the authors present a new approach to describe the CBM reservoir diffusivity equation in a form that fully couples the pressure-dependent diffusivity and time-dependent desorption effects in the transport mechanism of CBM reservoirs. This paper presents a semi-analytical solution of the fully coupled diffusivity equation under pseudo-steady state flow conditions. The proposed solution is then leveraged to predict the performance of a two-phase CBM well using an approach that is alternative to the conventional method for CBM reservoirs. The proposed semi-analytical model presents a computational method not only to predict the performance but also to evaluate the performance of a producing CBM well. The model presented in this study has been used to investigate the impact of pressure-dependent diffusivity and time-dependent desorption on the production behavior of CBM wells producing under pseudo-steady state conditions. The results of the semi-analytical solution have been verified using numerical simulator CMG-GEM as well as actual in-field data.

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Impact of pressure-dependent diffusivity on transient pressure analysis of a dry Coalbed Methane (CBM) wells: A new approach

Upadhyay

Gupta²,

Rajak³

2023

J Earth Syst Sci

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An Alternative Approach to Predicting Reservoir Performance in a Coalbed Methane (CBM) Well Flowing Under Dominant Matrix Shrinkage Effect

Cited by 6 publications

References 9 publications

A Novel Alternative Method of Compositional Simulation: A Semi-Analytical Approach for Predicting and Evaluating Reservoir Performance of a Multicomponent Coalbed Methane (CBM) Well

A Novel Alternative Method of Compositional Simulation: A Semi-Analytical Approach for Predicting and Evaluating Reservoir Performance of a Multicomponent Coalbed Methane (CBM) Well

A New Approach to Evaluate and Predict the Reservoir Performance of a Two-Phase Flow Coalbed Methane Well with Fully Coupled Time-Dependent Desorption and Pressure-Dependent Diffusivity Effects

Impact of pressure-dependent diffusivity on transient pressure analysis of a dry Coalbed Methane (CBM) wells: A new approach

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