scholarly journals The Application of Integrated Assisted History Matching and Embedded Discrete Fracture Model Workflow for Well Spacing Optimization in Shale Gas Reservoirs with Complex Natural Fractures

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Qiwei Li ◽  
Jianfa Wu ◽  
Cheng Chang ◽  
Hongzhi Yang ◽  
Chuxi Liu ◽  
...  
Keyword(s):  
Shale Gas ◽  
Reservoir Simulation ◽  
History Matching ◽  
Fracture Model ◽  
Natural Fractures ◽  
Gas Reservoirs ◽  
Discrete Fracture Model ◽  
Shale Gas Reservoirs ◽  
Well Spacing ◽  
Discrete Fracture

An appropriate well spacing plan is critical for the economic development of shale gas reservoirs. The biggest challenge for well spacing optimization is interpreting the subsurface uncertainties associated with hydraulic and natural fractures. Another challenge is the existence of complex natural fractures. This work applied an integrated well spacing optimization workflow in shale gas reservoirs of the Sichuan Basin in China with both hydraulic and natural fractures. The workflow consists of five components: data preparation, reservoir simulation, estimated ultimate recovery (EUR) analysis, economic calculation, and well spacing optimization. Firstly, the multiple realizations of thirteen uncertain parameters of matrix and fractures, including matrix permeability and porosity, three relative permeability parameters, hydraulic fracture height, half-length, width, conductivity, water saturation, and natural fracture number, length, and conductivity, were captured by the assisted history matching (AHM). The fractures were modeled by the embedded discrete fracture model (EDFM) accurately and efficiently. Then, 84 AHM solutions combining with five well spacing scenarios from 517 ft to 1550 ft would generate 420 simulation cases. After reservoir simulation of these 420 cases, we forecasted the long-term gas production for each well spacing scenario. Gas EUR degradation and well interference would imply the critical well spacing. The net present value (NPV) for all scenarios would be calculated and trained by K -nearest neighbors (KNN) proxy to better understand the relationship between well spacing and NPV. In this study, the optimum well spacing was determined as 793 ft, corresponding with a maximum NPV of 18 million USD, with the contribution of hydraulic fractures and natural fractures.

An Integrated Assisted History Matching and Embedded Discrete Fracture Model Workflow for Well Spacing Optimization in Shale Gas Reservoirs

2021 ◽  
pp. 1-29
Author(s):  
Qiwei Li ◽  
Rui Yong ◽  
Jianfa Wu ◽  
Cheng Chang ◽  
Chuxi Liu ◽  
...  
Keyword(s):  
Shale Gas ◽  
History Matching ◽  
Essential Element ◽  
Fracture Model ◽  
Gas Reservoirs ◽  
Discrete Fracture Model ◽  
Shale Gas Reservoirs ◽  
Well Spacing ◽  
Discrete Fracture ◽  
Assisted History Matching

Abstract Optimum well spacing is an essential element for the economic development of shale gas reservoirs. We present an integrated assisted history matching (AHM) and embedded discrete fracture model (EDFM) workflow for well spacing optimization by considering multiple uncertainty realizations and economic analysis. This workflow is applied in shale gas reservoirs of the Sichuan Basin in China. Firstly, we applied the AHM to calibrate ten matrix and fracture uncertain parameters using a real shale-gas well, including matrix permeability, matrix porosity, three relative permeability parameters, fracture height, fracture half-length, fracture width, fracture conductivity, and fracture water saturation. There are 71 history matching solutions obtained to quantify their posterior distributions. Integrating these uncertainty realizations with five well spacing scenarios, which are 517 ft, 620 ft, 775 ft, 1030 ft, and 1550 ft, we generated 355 cases to perform production simulations using the EDFM method coupled with a reservoir simulator. Then, P10, P50, and P90 values of gas estimated ultimate recovery (EUR) for different well spacing scenarios were determined. Additionally, the degradation of EUR with and without well interference was analyzed. Next, we calculated the NPVs of all simulation cases and trained the K-Nearest Neighbors (KNN) proxy, which describes the relationship between the NPV and all uncertain matrix and fracture parameters and varying well spacing. After that, the KNN proxy was used to maximize the NPV under the current operation cost and natural gas price. Finally, the maximum NPV of 3 million USD with well spacing of 766 ft was determined.

Discrete fracture model with multi-field coupling transport for shale gas reservoirs

2017 ◽  
Vol 158 ◽  
pp. 107-119 ◽  
Author(s):  
Cheng Cao ◽  
Qianping Zhao ◽  
Chao Gao ◽  
Jianbo Sun ◽  
Jie Xu ◽  
...  
Keyword(s):  
Shale Gas ◽  
Fracture Model ◽  
Gas Reservoirs ◽  
Discrete Fracture Model ◽  
Field Coupling ◽  
Shale Gas Reservoirs ◽  
Discrete Fracture

scholarly journals A Novel Optimization Workflow Coupling Statistics-Based Methods to Determine Optimal Well Spacing and Economics in Shale Gas Reservoir with Complex Natural Fractures

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3965
Author(s):  
Cheng Chang ◽  
Chuxi Liu ◽  
Yongming Li ◽  
Xiaoping Li ◽  
Wei Yu ◽  
...  
Keyword(s):  
Shale Gas ◽  
History Matching ◽  
Net Present Value ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Shale Gas Reservoir ◽  
Shale Gas Reservoirs ◽  
Well Spacing

In order to account for big uncertainties such as well interferences, hydraulic and natural fractures’ properties and matrix properties in shale gas reservoirs, it is paramount to develop a robust and efficient approach for well spacing optimization. In this study, a novel well spacing optimization workflow is proposed and applied to a real shale gas reservoir with two-phase flow, incorporating the systematic analysis of uncertainty reservoir and fracture parameters. One hundred combinations of these uncertainties, considering their interactions, were gathered from assisted history matching solutions, which were calibrated by the actual field production history from the well in the Sichuan Basin. These combinations were used as direct input to the well spacing optimization workflow, and five “wells per section” spacing scenarios were considered, with spacing ranging from 157 m (517 ft) to 472 m (1550 ft). An embedded discrete fracture model was used to efficiently model both hydraulic fractures and complex natural fractures non-intrusively, along with a commercial compositional reservoir simulator. Economic analysis after production simulation was then carried out, by collecting cumulative gas and water production after 20 years. The net present value (NPV) distributions of the different well spacing scenarios were calculated and presented as box-plots with a NPV ranging from 15 to 35 million dollars. It was found that the well spacing that maximizes the project NPV for this study is 236 m (775 ft), with the project NPV ranging from 15 to 35 million dollars and a 50th percentile (P50) value of 25.9 million dollars. In addition, spacings of 189 m (620 ft) and 315 m (1033 ft) can also produce substantial project profits, but are relatively less satisfactory than the 236 m (775 ft) case when comparing the P25, P50 and P75 values. The results obtained from this study provide key insights into the field pilot design of well spacing in shale gas reservoirs with complex natural fractures.

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

2020 ◽  
Author(s):  
Bin Wang
Keyword(s):  
Numerical Modeling ◽  
Open Source ◽  
Shale Gas ◽  
History Matching ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Gas Reservoirs ◽  
Pressure Drops ◽  
Shale Gas Reservoirs ◽  
Fracture Models

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.

scholarly journals Efficient Modeling of Hydraulic Fractures with Diamond Boundary in Shale Gas Reservoirs

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Mingyi Gao ◽  
Wen Zhou ◽  
Jian Zhang ◽  
Cheng Chang ◽  
Chuxi Liu ◽  
...  
Keyword(s):  
Shale Gas ◽  
Hydraulic Fracture ◽  
History Matching ◽  
Total Surface Area ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Well Performance ◽  
Production Forecast ◽  
Discrete Fracture Model ◽  
Discrete Fracture

Abstract The effects of hydraulic fractures with complex boundaries on the well performance of a shale gas well, considering a more realistic corner point geological model, have rarely been studied previously. In this study, the nonintrusive embedded discrete fracture model (EDFM) method was employed to investigate the effects of different boundary shapes of hydraulic fracture, coupling a network of sophisticated natural fractures discrete fracture network (DFN) on well performance. First, by implementing the powerful EDFM technology, concepts of two categories (rectangle and diamond) of hydraulic fracture with different boundaries were designed. Next, the geometric equations defining vertices of multiple rectangular- or diamond-shaped hydraulic fractures in arbitrary coordinate systems were derived. Subsequently, the horizontal well with multistaged hydraulic fractures and sophistically oriented 3D natural fractures was inputted into the reservoir model to perform history matching. After history matching, the results were further analyzed to compare the production forecast from the two categories. The results show that 20-year cumulative gas productions for rectangle- and diamond-shaped fractures are approximately 1.237×108 m3 and 1.486×108 m3, respectively. In other words, the diamond category can produce 20.1% more gas than the rectangle category. For cumulative water production, the diamond category produces 3.8×104 m3, as against the 3.0×104 m3 produced by the rectangle category (or 26.7% more). This implies that the diamond-shaped fractures have the potential to reach the far field region of the reservoir away from the wellbore. This means that more intersections with natural fractures DFN can be achieved, and more drainage area is unlocked. The visualization of pressure distributions and drainage volume was easily shown, and these results further confirm that the extent of fluid drainage by the diamond fracture is larger compared to that by the rectangular fracture given the same total surface area.

scholarly journals Investigation of the Effect of Natural Fractures on Multiple Shale-Gas Well Performance Using Non-Intrusive EDFM Technology

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 932 ◽  
Author(s):  
Wei Yu ◽  
Xiaohu Hu ◽  
Malin Liu ◽  
Weihong Wang
Keyword(s):  
Shale Gas ◽  
History Matching ◽  
Natural Fracture ◽  
Fracture Density ◽  
Natural Fractures ◽  
Well Performance ◽  
Two Phase ◽  
Gas Well ◽  
Discrete Fracture Model ◽  
Well Spacing

The influence of complex natural fractures on multiple shale-gas well performance with varying well spacing is poorly understood. It is difficult to apply the traditional local grid refinement with structured or unstructured gridding techniques to accurately and efficiently handle complex natural fractures. In this study, we introduced a powerful non-intrusive embedded discrete fracture model (EDFM) technology to overcome the limitations of exiting methods. Through this unique technology, complex fracture configurations can be easily and explicitly embedded into structured matrix blocks. We set up a field-scale two-phase reservoir model to history match field production data and predict long-term recovery from Marcellus. The effective fracture properties were determined thorough history matching. In addition, we extended the single-well model to include two horizontal wells with and without including natural fractures. The effects of different numbers of natural fractures on two-well performance with varying well spacing of 200 m, 300 m, and 400 m were examined. The simulation results illustrate that gas productivity almost linearly increases with the number of two-set natural fractures. Furthermore, the difference of well performance between different well spacing increases with an increase in natural fracture density. A larger well spacing is preferred for economically developing the shale-gas reservoirs with a larger natural fracture density. The findings of this study provide key insights into understanding the effect of natural fractures on well performance and well spacing optimization.

scholarly journals Model Optimization of Shale Gas Reservoir Volume Fracturing Dissolved Gas Simulation Adsorbed Gas

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Hao Dong ◽  
Yi Zhang ◽  
Zongwu Li ◽  
Chao Jiang ◽  
Jiaze Li ◽  
...  
Keyword(s):  
Shale Gas ◽  
Fracture Model ◽  
Natural Fractures ◽  
Dissolved Gas ◽  
Gas Reservoir ◽  
Discrete Fracture Model ◽  
Shale Gas Reservoir ◽  
Basic Model ◽  
Adsorbed Gas ◽  
Discrete Fracture

Shale reservoirs have some natural fractures with a certain density and connectivity. The basic percolation model of shale gas reservoir: the black oil model of gas-water phase is used as the basic model, and the dissolved gas is used to simulate adsorbed gas. Accurate description of natural fractures: random distributed discrete fracture model is used as the basic model to describe natural fractures. By comparing the calculation results of single medium (including random distributed discrete fracture model) and double medium model, the model for predicting shale gas productivity is optimized.

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