A Fully Three Dimensional Semianalytical Model for Shale Gas Reservoirs with Hydraulic Fractures

Li, Yuwei; Zuo, Lihua; Yu, Wei; Chen, Youguang

doi:10.3390/en11020436

Cited by 20 publications

(12 citation statements)

References 48 publications

(54 reference statements)

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“…U e i is defined as the elastic energy of the i-th hysteresis loop in the cyclic loading and unloading process. The damage variable of any i-th cycle can be determined by Equation (5). In order to obtain the cumulative rock damage variable D after n cycles, we should accumulate the single damage variable of all cycles.…”

Section: Characteristics Of Rock Stress-strain Curve During Pulsatimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Hydraulic fracturing, as one of the most effective stimulation methods to exploit oil and gas, plays an important role in the development of different type of reservoirs worldwide. [1][2][3][4][5][6][7][8][9][10][11] As an emerging technology for the enhancement of well production, pulsating fracturing shows its outstanding potential in the exploitation of unconventional oil and gas reservoirs (such as coal bed methane formation). Compared with the traditional hydraulic fracturing technology, pulsating fracturing is more likely to cause damage to the rock, reduce the strength of the rock, [12][13][14] and facilitate the propagation of fractures in the rock.…”

Section: Introductionmentioning

confidence: 99%

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Rock damage evolution model of pulsating fracturing based on energy evolution theory

Zhao²,

Tang

et al. 2019

Energy Science & Engineering

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Pulsating fracturing, as a new technology for unconventional oil and gas exploration, enables to enhance stimulated reservoir volume (SRV) effectively, which further helps to improve well performance. It is of great importance for the evaluation of fracturing performance and optimization of fracturing parameters by accurately calculating variables from formation impairment during pulsating fracturing treatment. Based on the principle of conservation of energy, a novel theoretical model describing the evolution of rock damage was proposed by analyzing energy evolutionary characteristics from the hysteresis loop of rock stress‐strain curve while the treatment. This model was in a good agreement with experimental data. In this paper, our study indicates that the rock damage is caused by the accumulation of damage in each cyclic loading and unloading process during pulsating fracturing. Moreover, the cumulative rock damage would increase with the increment of the number of cyclic loading and unloading. Conversely, the rock strength is negatively correlated with cyclic number. The cumulative damage variable approximates to one as the rock breaks. Additionally, the frequency and the stress level of pulsating fracturing have an obvious impact on the evolution of rock damage. The optimization of these parameters can help to accelerate the rock damage and reduce the corresponding rock strength. The speed of rock damage can be accelerated with the enhancement of the stress level at the later period of the step loading, which facilitates the increment of cumulative damage variable. Our new model provides a guideline for predicting the initial rock damage during pulsating treatment.

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Section: Characteristics Of Rock Stress-strain Curve During Pulsatimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Rock damage evolution model of pulsating fracturing based on energy evolution theory

Zhao²,

Tang

et al. 2019

Energy Science & Engineering

Self Cite

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show abstract

“…The analytical method dates back to 1970s, where the line-source fundamental solution is derived for simple fracture geometry such as single bi-wing hydraulic fractures and pseudo-pressure is applied to linearized the non-linear real gas equation (Gringarten et al, 1974, Cinco et al, 1978and Agarwal 1979. Recently, the analytical method is extended into semi-analytical method to consider complex fracture networks and shale gas storage mechanism based on the boundary element method (Zuo et al, 2016, Chen et al, 2015, 2016, 2017Yang et al, 2016a, 2017, 2017and Li et al, 2018. Although analytical-based method is fast and accurate, it is difficult to handle rock heterogeneity, multi-phase, multi-compositional and strong non-linear transport mechanisms in shale gas flow problems (Houze et al, 2010 andOlorode et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

MRST-Shale: An Open-Source Framework for Generic Numerical Modeling of Unconventional Shale and Tight Gas Reservoirs

Wang¹

2020

Preprint

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We present a generic and open-source framework for the numerical modeling of the expected transport and storage mechanisms in unconventional gas reservoirs. These unconventional reservoirs typically contain natural fractures at multiple scales. Considering the importance of these fractures in shale gas production, we perform a rigorous study on the accuracy of different fracture models. The framework is validated against an industrial simulator and is used to perform a history-matching study on the Barnett shale. This work presents an open-source code that leverages cutting-edge numerical modeling capabilities like automatic differentiation, stochastic fracture modeling, multi-continuum modeling and other explicit and discrete fracture models. We modified the conventional mass balance equation to account for the physical mechanisms that are unique to organic-rich source rocks. Some of these include the use of an adsorption isotherm, a dynamic permeability-correction function, and an embedded discrete fracture model (EDFM) with fracture-well connectivity. We explore the accuracy of the EDFM for modeling hydraulically-fractured shale-gas wells, which could be connected to natural fractures of finite or infinite conductivity, and could deform during production. Simulation results indicates that although the EDFM provides a computationally efficient model for describing flow in natural and hydraulic fractures, it could be inaccurate under these three conditions: 1. when the fracture conductivity is very low. 2. when the fractures are not orthogonal to the underlying Cartesian grid blocks, and 3. when sharp pressure drops occur in large grid blocks with insufficient mesh refinement. Each of these results are very significant considering that most of the fluids in these ultra-low matrix permeability reservoirs get produced through the interconnected natural fractures, which are expected to have very low fracture conductivities. We also expect sharp pressure drops near the fractures in these shale gas reservoirs, and it is very unrealistic to expect the hydraulic fractures or complex fracture networks to be orthogonal to any structured grid. In conclusion, this paper presents an open-source numerical framework to facilitate the modeling of the expected physical mechanisms in shale-gas reservoirs. The code was validated against published results and a commercial simulator. We also performed a history-matching study on a naturally-fractured Barnett shale-gas well considering adsorption, gas slippage & diffusion and fracture closure as well as proppant embedment, using the framework presented. This work provides the first open-source code that can be used to facilitate the modeling and optimization of fractured shale-gas reservoirs. To provide the numerical flexibility to accurately model stochastic natural fractures that are connected to hydraulically-fractured wells, it is built atop other related open-source codes. We also present the first rigorous study on the accuracy of using EDFM to model both hydraulic fractures and natural fractures that may or may not be interconnected.

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“…To characterize the transient performance for shale gas reservoirs, many scholars have made some efforts to simulate the fluids flow and transport behaviors in such complexly-structured fracture network through analytical and semi-analytical solutions [7][8][9][10]. These solutions are mostly proposed in the terms of multi-porosity model and multi-linear model.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Coupled Multifracture and Multicontinuum Models for Shale Gas Simulation by Use of Semi-Analytical Approach

et al. 2018

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Abstract:Combining the advantages of multicontinuum and multifracture representations provides an easy-to-use tool to adequately capture the characteristic of the multiscaled fracture system in shale gas reservoir. A hybrid model is established on the basis of simplified conceptual productivity assumption, where the matrix volume is divided into two sub-domains (triple-porosity model and dual-depletion flowing model) and the fracture volume is represented by discrete finite conductivity fracture. In addition, the mechanisms of instant desorption, viscous flow and dual-depletion in matrix are taken into account. The rate transient responses are then obtained by use of semi-analytical approach. Based on the model, type curves are plotted and verified by comparing with alternative reliable methods. Different flow regimes in shale gas reservoirs can be identified and detected. The Generalized Likelihood Uncertainty Estimation methodology, based on probabilistic aggregation theory, is employed to integrating those two productivity models together such that the production can be predicted more accurately. A field example is applied to validate the applicability of this new model. Finally, it is concluded that the proposed model can predict the rate and cumulative rate more easily and practically.

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A Fully Three Dimensional Semianalytical Model for Shale Gas Reservoirs with Hydraulic Fractures

Cited by 20 publications

References 48 publications

Rock damage evolution model of pulsating fracturing based on energy evolution theory

Rock damage evolution model of pulsating fracturing based on energy evolution theory

MRST-Shale: An Open-Source Framework for Generic Numerical Modeling of Unconventional Shale and Tight Gas Reservoirs

Hybrid Coupled Multifracture and Multicontinuum Models for Shale Gas Simulation by Use of Semi-Analytical Approach

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