A density-diffusivity approach for the unsteady state analysis of natural gas reservoirs

Ye, Peng; Ayala, Luis F.

doi:10.1016/j.jngse.2012.03.004

Cited by 36 publications

(15 citation statements)

References 28 publications

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“…In order to investigate the effect of pressure-dependent fluid properties on transient responses, pseudo-variables are needed to be implemented in unsteady state analysis. Recently, Ye and Ayala [57] proposed a density-based approach to analyze the unsteady state responses for natural gas reservoirs. This approach emphasized the significance of viscosity-compressibility changes from the pressure depletion based on the following depletion-driven dimensionless variables:…”

Section: Derivation Of the Pseudo-functionsmentioning

confidence: 99%

“…In another case, a larger rate decline and smaller cumulative production can be obtained when neglecting the desorption effect. These results are compared in the same figure against the unmodified density-based solution of Ye and Ayala [57], which did not incorporate desorption corrections, yielding a poor prediction. For example, for a reservoir with a length of 150 m and width of 110 m, the rigorous solution predicts a rate decline from 8700 to 1000 m 3 in 6.46 years.…”

Section: Effects Of Depletion-driven Fluid Propertiesand Gas Desorptionmentioning

confidence: 99%

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Rate Decline Analysis of Vertically Fractured Wells in Shale Gas Reservoirs

et al. 2017

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Based on the porous flow theory, an extension of the pseudo-functions approach for the solution of non-linear partial differential equations considering adsorption-desorption effects was used to investigate the transient flow behavior of fractured wells in shale gas reservoirs. The pseudo-time factor was employed to effectively linearize the partial differential equations of the unsteady flow response. The production performance of vertically fractured wells in shale gas reservoirs under either constant flow rate or constant bottom-hole pressure conditions was analyzed using the composite flow model. The calculation results indicate that the non-linearities that develop in the gas diffusivity equation have significant effects on the unsteady response, leading to a larger pressure depletion and rate decline in the late-time period. In addition, gas desorption from the shale acts as a recharge source, which relieves the gas production rate of decline. Greater values for the Langmuir volumes or Langmuir pressures provide additional pressure support, leading to a lower rate decline while the flowing well bottom-hole pressure is maintained. The reservoir size mainly affects the duration of the pressure depletion and rate decline. In the case of ignoring the non-linearity and adsorption-desorption effect in the differential equation, a greater rate decline under constant bottom-hole pressure production can be obtained during the boundary-dominated depletion. This work provides a better understanding of gas desorption in shale gas reservoirs and new insight into investigating the production performances of fractured gas well.

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Section: Derivation Of the Pseudo-functionsmentioning

confidence: 99%

Section: Effects Of Depletion-driven Fluid Propertiesand Gas Desorptionmentioning

confidence: 99%

Rate Decline Analysis of Vertically Fractured Wells in Shale Gas Reservoirs

et al. 2017

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“…Using depletion-driven dimensionless variables k and b, they successfully decoupled pressure-dependent effects from pressure depletion. Ye and Ayala (2012) were accordingly able to show that the dimensionless gas rate solutions under constant bottomhole pressure can be rescaled from their liquid counterparts with depletion-driven dimensionless variables k and b. Zhang and Ayala (2014a) subsequently provided rigorous derivation for the rescaling approach. The relationship is written by Zhang and Ayala (2014a) as follows:…”

Section: Rate-time Forecast Of Naturally Fractured Gas Reservoirsmentioning

confidence: 99%

“…For the case of single-porosity systems, Ayala (2012, 2013), and Ye (2012, 2013) had proposed a density-based approach for decline curve analysis. With depletion-driven dimensionless variables k and b, Ye and Ayala (2012) was able to rescale dimensionless gas rate solution under constant bottom-hole pressure from their liquid counterparts, which thereupon facilitates the decline curve analysis based on density. Zhang and Ayala (2014a) provided rigorous derivation for the density-based approach and improved the methods for analyzing data at variable pressure drawdown/rate at decline stage (Ayala and Zhang 2013;Zhang and Ayala 2014b).…”

Section: Introductionmentioning

confidence: 99%

Decline curve analysis using a pseudo-pressure-based interporosity flow equation for naturally fractured gas reservoirs

Zhang

2016

J Petrol Explor Prod Technol

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Significant amounts of oil and gas are trapped in naturally fractured reservoirs, a phenomenon which has attracted growing attention as production from unconventional reservoirs starts to outpace production from conventional sources. Traditionally, the dual-porosity model has been used in modeling naturally fractured reservoirs. In a dual-porosity model, fluid flows through the fracture system in the reservoir, while matrix blocks are segregated by the fractures and act as fluid sources for them. This model was originally developed for liquid flow in naturally fractured systems and it is therefore inadequate for capturing pressuredependent effects such as viscosity-compressibility changes in gas systems in its original form. This study presents a rigorous derivation of a gas interporosity flow equation that accounts for the effects of such pressure-sensitive properties. A numerical simulator using the gas interporosity flow equation is built and demonstrates a significant difference in system response from that of a simulator implementing a liquid-form interporosity flow equation. For this reason, rigorous modeling of interporosity flow is considered essential to decline curve analysis for naturally fractured gas reservoirs. In this study, we also show that the use of the proposed gas interporosity flow equation eliminates latetime decline discrepancies and enables rigorous decline curve analysis. The applicability of density-based approach in dual-porosity gas systems is investigated, and the approach reveals that gas production can be forecast in terms of a rescaled liquid solution that uses depletion-driven parameters, k and b. Application of this approach demonstrated that, at the second decline stage, gas production profile shifted from its liquid counterpart is identical to gas numerical responses with gas interporosity flow equation in effects. The production rates from the pseudo-function approach and those from simulations implementing the gas interporosity flow equation for the synthetic reservoirs are compared against each other, which demonstrated good matches during decline.

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“…[7] Flow of compressible and slightly compressible fluids (water or oil) in fractured reservoirs has been studied extensively with applications in prediction of production rates and well testing [Warren and Root 1963;Kazemi et al, 1976;Zimmerman et al, 1993Zimmerman et al, , 1996Civan and Rasmussen, 2002;Penuela et al, 2002;Bogdanov et al, 2003;Lu and Connel, 2007;van Heel et al, 2008;Mora and Wattenbarger, 2009;Hassanzadeh et al, 2009;Ranjbar and Hassanzadeh, 2010;Mourzenko et al, 2011;Ranjbar et al, 2012;Ye and Ayala, 2012]. As an example, Hoteit and Firoozabadi [2005] developed a discrete fracture model to simulate the flow of compressible fluids in homogeneous, heterogeneous and fractured porous media.…”

Section: Introduction and Previous Studiesmentioning

confidence: 99%

Semianalytical solutions for release of fluids from rock matrix blocks with different shapes, sizes, and depletion regimes

Ranjbar

Chen

2013

Water Resources Research

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[1] Dual-porosity (DP) models have been extensively used to simulate the flow of fluids (water or gas) in aggregate soils and fractured porous media. The fluid exchange between the rock matrix blocks and the fracture network is very important in DP models. In this study, we present semianalytical solutions for release of a single-phase liquid or gas from cylindrical and spherical matrix blocks with various block size distributions and different pressure depletion regimes in the fracture. The nonlinear pressure diffusivity equations for flow of gas and air are solved analytically using an approximate integral method. It is shown that this solution can be simplified to model flow of slightly compressible fluids like water in DP media. The effect of variable block size distribution on the release rate for different block geometries is studied. Practically it is not feasible to model a large-scale fractured reservoir based on a fine grid approach due to the requirement of large computational time. The presented semianalytical model can be incorporated into numerical models for accurate modeling of the amount of transferred fluid between matrix and fractures using a DP approach. It is shown that the results calculated by the developed model match well with those from fine grid numerical simulations. Furthermore, the developed model can recover the available solutions in the literature for slightly compressible fluids such as water or oil. It can be used to calculate two-or threedimensional flows in matrix blocks bounded by two or three sets of fractures, respectively.Citation: Ranjbar, E., H. Hassanzadeh, and Z. Chen (2013), Semianalytical solutions for release of fluids from rock matrix blocks with different shapes, sizes, and depletion regimes, Water Resour.

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A density-diffusivity approach for the unsteady state analysis of natural gas reservoirs

Cited by 36 publications

References 28 publications

Rate Decline Analysis of Vertically Fractured Wells in Shale Gas Reservoirs

Rate Decline Analysis of Vertically Fractured Wells in Shale Gas Reservoirs

Decline curve analysis using a pseudo-pressure-based interporosity flow equation for naturally fractured gas reservoirs

Semianalytical solutions for release of fluids from rock matrix blocks with different shapes, sizes, and depletion regimes

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