Pressure-transient analysis of infinite-conductivity fractured gas wells producing at high-flow rates

Nashawi, Ibrahim Sami

doi:10.1016/j.petrol.2008.10.001

Cited by 8 publications

(4 citation statements)

References 56 publications

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“…(1) and (2). Therefore, methane rate at production start (QP), percent decline (PD), end of possible production period (END), and production rate at start of forecast period (QFC) were selected as primary variables to be simulated with surface elevation (ELEV).…”

Section: Selection Of Primary Variablesmentioning

confidence: 99%

“…As mining advances under the venthole, the strata that surround the well deform and establish preferential pathways for the released methane, mostly from the coal seams within the fractured zone, to flow towards the ventholes [1]. The properties of fractured zones, mainly permeability, are determined through conventional pressure-and rate-transient well test analyses techniques that are used systematically and routinely for oil and gas [2][3][4][5][6]. Results showed that permeabilities of bedding plane separations can be as high as 150 Darcies, with average permeabilities (including fractures and intact formations) within the slotted casing interval of GGVs varying between 1 Darcy and 10 Darcies [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

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Sequential Gaussian co-simulation of rate decline parameters of longwall gob gas ventholes

Karacan¹,

Olea²

2013

International Journal of Rock Mechanics and Mining Sciences

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Gob gas ventholes (GGVs) are used to control methane inflows into a longwall mining operation by capturing the gas within the overlying fractured strata before it enters the work environment. Using geostatistical co-simulation techniques, this paper maps the parameters of their rate decline behaviors across the study area, a longwall mine in the Northern Appalachian basin. Geostatistical gas-in-place (GIP) simulations were performed, using data from 64 exploration boreholes, and GIP data were mapped within the fractured zone of the study area. In addition, methane flowrates monitored from 10 GGVs were analyzed using decline curve analyses (DCA) techniques to determine parameters of decline rates. Surface elevation showed the most influence on methane production from GGVs and thus was used to investigate its relation with DCA parameters using correlation techniques on normal-scored data. Geostatistical analysis was pursued using sequential Gaussian co-simulation with surface elevation as the secondary variable and with DCA parameters as the primary variables. The primary DCA variables were effective percentage decline rate, rate at production start, rate at the beginning of forecast period, and production end duration. Cosimulation results were presented to visualize decline parameters at an area-wide scale. Wells located at lower elevations, i.e., at the bottom of valleys, tend to perform better in terms of their rate declines compared to those at higher elevations. These results were used to calculate drainage radii of GGVs using GIP realizations. The calculated drainage radii are close to ones predicted by pressure transient tests.

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Section: Selection Of Primary Variablesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sequential Gaussian co-simulation of rate decline parameters of longwall gob gas ventholes

Karacan¹,

Olea²

2013

International Journal of Rock Mechanics and Mining Sciences

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“…Transient well test analysis methods, such as rate drawdown, interference, and pressure build-up tests, are developed for and applied in the petroleum and natural gas industry for both conventional reservoirs and coalbed methane reservoirs (Matthews and Russell 1967;Earlougher 1977;Dake 1978;Lee 1982;King et al 1986;Mohaghegh and Ertekin 1991;Kuchuk and Onur 2003;Engler and Tiab 1996;Nashawi 2008;Kuchuk and Onur 2003;Valvatne et al 2003;Escobar et al 2007;Sheng 2009). These techniques can assist in understanding the characteristics of the gob reservoir and the interaction of GGVs with the gob and mining environment.…”

Section: Challenges In Gob and Ggv Characterizationmentioning

confidence: 99%

Monte Carlo Simulation and Well Testing Applied in Evaluating Reservoir Properties in a Deforming Longwall Overburden

Karacan

Goodman

2010

Transp Porous Med

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During longwall mining, the intact strata start to deform and fracture as the mining face progresses. Gob gas ventholes (GGVs) are drilled from the surface over a longwall panel before mining to capture methane from the fractured zone. Due to fracturing and bedding-plane separations, reservoir properties change extensively. This poses a major problem for venthole designers and methane control engineers and may become a safety and health concern for underground work force due to unexpected methane emissions: it is difficult to predict the location of major strata separations and their temporal magnitudes to best locate the ventholes. Measurements obtained at different times during longwall mining may not be helpful for this purpose as strata deformation is a dynamic process and the results from different tests may not be lumped together to analyze the data collectively. This article uses a combination of Monte Carlo (MC) simulation and well testing methods to analyze multiple data sets obtained from a GGV at different longwall face locations. The aim was to determine the magnitude of average strata separation before conducting well test analyses to determine the properties of a deformed reservoir. MC simulation was used to process cross-correlated and uncertain data distributions obtained from measurements to generate a set of normally distributed values for each data type. These values were further used to project the amount of strata separation to the timing of well test. Finally, well-test analyses were used to interpret test data and to evaluate reservoir properties. h Net pay (m, ft) k Permeability (md, md) kh Flow capacity (md.m, md.ft) k/μ Mobility kh/μ Transmissivity P Pressure (kPa, psia) w Channel thickness (m, ft) q j jth flow rate (m 3 /d, bbl/d) q n nth flow rate (m 3 /d, bbl/d) r e External radius or radius of investigation (m, ft) r w Wellbore radius (m, ft) s Apparent skin factor t Time (h, h) t a Pseudo-time (h, h) t n nth flow period or superposition time Pseudo-pressure for gas (kPa 2 /Pa.s, psia 2 /cp)

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“…Many scholars have overlooked the permeability of soil layers (especially when rock permeability is low) due to the significant role that fractures play in water transport, focusing solely on the flow capacity of fractures (referred to as “one region flow,” i.e., clear flow in fractures). In the early days, the fluid transport study in the fractured porous medium primarily focused on the flow capacity of a single fracture, examining the effects of fracture aperture (Méheust & Schmittbuhl, 2000; Zheng et al., 2008; Lenci, Putti, et al., 2022; Lenci, Méheust, et al., 2022), surface roughness (Boutt et al., 2006), and fluid properties (Felisa et al., 2018; Lavrov, 2014) on the flow capacity of a single fracture through theoretical deductions (Nashawi, 2008; Pouya et al., 2020), numerical simulations (Miyoshi et al., 2003; Xie et al., 2015), and laboratory experiments (Qian et al., 2005, 2007). The description of the flow capacity of a single fracture was initially based on the cubic law (Witherspoon et al., 1980).…”

Section: Introductionmentioning

confidence: 99%

A Semi‐Analytical Solution for the Equivalent Permeability Coefficient of the Multilayered Porous Medium With Continuous Fracture

Zhang,

Liu

2024

Water Resources Research

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Fractures significantly alter the permeability characteristics of the natural porous media, especially for the multilayered porous medium system. The most direct and effective approach to assess the hydraulic conductivity of a multilayered porous medium with continuous fracture is to determine its equivalent permeability coefficient (EPC). A mathematical model with second‐order accuracy is established to analysis the permeability characteristics of the multilayered porous medium incorporating a continuous fracture. The Navier‒Stokes equation is used to govern the clear fluid motion in the continuous fracture, and the seepage fluid motion in the multilayered porous matrix is governed by the Brinkman‒Darcy equation. The semi‐analytical solutions for the velocity profile and EPC of the present model are derived under the conditions of the jumping stress at the fracture‐matrix interface and the continuous velocity at the matrix(i)‐matrix(i +1) interface. The Lattice Boltzmann method, finite element method, and one domain method simulations are conducted to verify the deduced semi‐analytical solutions of the velocity profile. Furthermore, the calculated EPC of the present multilayered model is in good agreement with that of the existing classic models (i.e., one region: fracture, two regions: fracture‐matrix, three regions: fracture‐matrix1‐matrix2, and multilayered porous medium without fracture). Parameter sensitivity reveals that increasing the thickness, dip angle, and porosity of the fractured porous media increases the flow velocity, while an increase in the stress jump coefficient can result in the opposite effect. This implies that porous layers containing fracture are more susceptible to erosion, particularly under conditions of steep dip angle and strong permeability.

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Pressure-transient analysis of infinite-conductivity fractured gas wells producing at high-flow rates

Cited by 8 publications

References 56 publications

Sequential Gaussian co-simulation of rate decline parameters of longwall gob gas ventholes

Sequential Gaussian co-simulation of rate decline parameters of longwall gob gas ventholes

Monte Carlo Simulation and Well Testing Applied in Evaluating Reservoir Properties in a Deforming Longwall Overburden

A Semi‐Analytical Solution for the Equivalent Permeability Coefficient of the Multilayered Porous Medium With Continuous Fracture

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