scholarly journals What Factors Control Shale-Gas Production and Production-Decline Trend in Fractured Systems: A Comprehensive Analysis and Investigation

SPE Journal ◽  
2016 ◽  
Vol 22 (02) ◽  
pp. 562-581 ◽  
Author(s):  
HanYi Wang
Keyword(s):  
Shale Gas ◽  
Gas Production ◽  
Reservoir Model ◽  
Reservoir Properties ◽  
Gas Reservoir ◽  
Gas Well ◽  
Field Development ◽  
Shale Gas Reservoir ◽  
Decline Curve ◽  
Realistic Prediction

Summary One of the most-significant practical problems with the optimization of shale-gas-stimulation design is estimating post-fracture production rate, production decline, and ultimate recovery. Without a realistic prediction of the production-decline trend resulting from a given completion and given reservoir properties, it is impossible to evaluate the economic viability of producing natural gas from shale plays. Traditionally, decline-curve analysis (DCA) is commonly used to predict gas production and its decline trend to determine the estimated ultimate recovery (EUR), but its analysis cannot be used to analyze which factors influence the production-decline trend because of a lack of the underlying support of physics, which makes it difficult to guide completion designs or optimize field development. This study presents a unified shale-gas-reservoir model, which incorporates real-gas transport, nanoflow mechanisms, and geomechanics into a fractured-shale system. This model is used to predict shale-gas production under different reservoir scenarios and investigate which factors control its decline trend. The results and analysis presented in the article provide us with a better understanding of gas production and decline mechanisms in a shale-gas well with certain conditions of the reservoir characteristics. More-in-depth knowledge regarding the effects of factors controlling the behavior of the gas production can help us develop more-reliable models to forecast shale-gas-decline trend and ultimate recovery. This article also reveals that some commonly held beliefs may sound reasonable to infer the production-decline trend, but may not be true in a coupled reservoir system in reality.

scholarly journals Analysis of the Influence of Different Fracture Network Structures on the Production of Shale Gas Reservoirs

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Ming Yue ◽  
Xiaohe Huang ◽  
Fanmin He ◽  
Lianzhi Yang ◽  
Weiyao Zhu ◽  
...  
Keyword(s):  
Finite Element ◽  
Shale Gas ◽  
Flow Direction ◽  
Fracture Network ◽  
Gas Production ◽  
Low Flow ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Shale Gas Reservoir ◽  
Gas Seepage

Volume fracturing is a key technology in developing unconventional gas reservoirs that contain nano/micron pores. Different fracture structures exert significantly different effects on shale gas production, and a fracture structure can be learned only in a later part of detection. On the basis of a multiscale gas seepage model considering diffusion, slippage, and desorption effects, a three-dimensional finite element algorithm is developed. Two finite element models for different fracture structures for a shale gas reservoir in the Sichuan Basin are established and studied under the condition of equal fracture volumes. One is a tree-like fracture, and the other is a lattice-like fracture. Their effects on the production of a fracture network structure are studied. Numerical results show that under the same condition of equal volumes, the production of the tree-like fracture is higher than that of the lattice-like fracture in the early development period because the angle between fracture branches and the flow direction plays an important role in the seepage of shale gas. In the middle and later periods, owing to a low flow rate, the production of the two structures is nearly similar. Finally, the lattice-like fracture model is regarded as an example to analyze the factors of shale properties that influence shale gas production. The analysis shows that gas production increases along with the diffusion coefficient and matrix permeability. The increase in permeability leads to a larger increase in production, but the decrease in permeability leads to a smaller decrease in production, indicating that the contribution of shale gas production is mainly fracture. The findings of this study can help better understand the influence of different shapes of fractures on the production in a shale gas reservoir.

scholarly journals Development Evaluation and Optimization of Deep Shale Gas Reservoir with Horizontal Wells Based on Production Data

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Wuguang Li ◽  
Hong Yue ◽  
Yongpeng Sun ◽  
Yu Guo ◽  
Tianpeng Wu ◽  
...  
Keyword(s):  
Shale Gas ◽  
Production System ◽  
Target Position ◽  
Horizontal Wells ◽  
Gas Production ◽  
Well Performance ◽  
Gas Reservoir ◽  
Horizontal Section ◽  
Technical Problems ◽  
Shale Gas Reservoir

The implementation of horizontal wells is a key to economic development of the deep shale gas reservoir. In order to optimize the key parameters for drilling, stimulation, and the production system, the development effect of a horizontal well in deep shale gas formations was investigated from various aspects in this study. The drilling, fracturing, and production performances of this well were analyzed combining with the geological characteristics. The main technical problems and key factors that restrict the gas well performance and estimated ultimate recovery (EUR) were clarified. Through the integrated study of geology and engineering, the optimization strategies for increasing gas production and EUR are provided. The Z2 area, where the Z2-H1 well is located, has good reservoir physical properties, which bring a high drilling efficiency. However, there are still some problems during its development, such as poor fracture extension both horizontally and vertically, limited stimulated reservoir volume (SRV), rapid production declining, large water production, and serious liquid accumulation. In this study, a comprehensive approach was proposed that can improve single-well production and EUR by optimizing the target position, horizontal section length, pathway, spacing, new drilling and fracturing technology, and production system.

scholarly journals Numerical Simulation of Gas-Water Two-Phase Flow in Deep Shale Gas Reservoir Development Based on Mixed Fracture Modeling

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Sidong Fang ◽  
Cheng Dai ◽  
Junsheng Zeng ◽  
Heng Li
Keyword(s):  
Shale Gas ◽  
Horizontal Well ◽  
Stress Sensitivity ◽  
Gas Production ◽  
Gas Reservoir ◽  
Two Phase ◽  
Discrete Fracture Model ◽  
Shale Gas Reservoir ◽  
Discrete Fracture ◽  
The Matrix

Abstract In this paper, the development of a three-dimensional, two-phase fluid flow model (Modified Embedded Discrete Fracture Model) to study flow performances of a fractured horizontal well in deep-marine shale gas is presented. Deep-marine shale gas resources account for nearly 80% in China, which is the decisive resource basis for large-scale shale gas production. The dynamic characteristics of deep shale gas reservoirs are quite different and more complex. This paper uses the embedded discrete fracture model to simulate artificial fractures (main fractures and secondary fractures) and the dual-media model to simulate the mixed fractured media of natural fractures and considers the flow characteristics of partitions (artificial fractures, natural fractures, and matrix). Gas desorption is considered in the matrix. Different degrees of stress sensitivity are considered for natural and artificial fractures. Aiming at accurately simulating the whole production history of horizontal well fracturing, especially the dynamic changes of postfracturing flowback, a postfracturing fluid initialization method based on fracturing construction parameters (fracturing fluid volume and pump stop pressure) is established. The flow of gas and water in the early stage after fracturing is simulated, and the regional phase permeability and capillary force curves are introduced to simulate the process of flowback and production of horizontal wells after fracturing. The influence of early fracture closure on the gas-water flow is characterized by stress sensitivity. A deep shale gas reservoir of Sinopec was selected for the case study. The simulation results show it necessary to consider the effects of fractures and stress sensitivity in the matrix when considering the dynamic change of production during the flowback and production stages. The findings of this study can help for better understanding of the fracture distribution characteristics of shale gas, shale gas production principle, and well EUR prediction, which provide a theoretical basis for the effective development of shale gas horizontal well groups.

scholarly journals Ensemble-based optimization of hydraulically fractured horizontal well placement in shale gas reservoir through Hough transform parameterization

2021 ◽  
Author(s):  
Liang Xue ◽  
Shao-Hua Gu ◽  
Xie-Er Jiang ◽  
Yue-Tian Liu ◽  
Chen Yang
Keyword(s):  
Simulation Model ◽  
Shale Gas ◽  
Horizontal Well ◽  
Gas Production ◽  
Design Parameters ◽  
Hydraulic Fractures ◽  
Gas Reservoir ◽  
Well Drilling ◽  
Shale Gas Reservoir ◽  
Fractured Horizontal Well

AbstractShale gas reservoirs have been successfully developed due to the advancement of the horizontal well drilling and multistage hydraulic fracturing techniques. However, the optimization design of the horizontal well drilling, hydraulic fracturing, and operational schedule is a challenging problem. An ensemble-based optimization method (EnOpt) is proposed here to optimize the design of the hydraulically fractured horizontal well in the shale gas reservoir. The objective is to maximize the net present value (NPV) which requires a simulation model to predict the cumulative shale gas production. To accurately describe the geometry of the hydraulic fractures, the embedded discrete fracture modeling method (EDFM) is used to construct the shale gas simulation model. The effects of gas absorption, Knudsen diffusion, natural and hydraulic fractures, and gas–water two phase flow are considered in the shale gas production system. To improve the parameter continuity and Gaussianity required by the EnOpt method, the Hough transformation parameterization is used to characterize the horizontal well. The results show that the proposed method can effectively optimize the design parameters of the hydraulically fractured horizontal well, and the NPV can be improved greatly after optimization so that the design parameters can approach to their optimal values.

scholarly journals A Two-Phase Flowback Model for Multiscale Diffusion and Flow in Fractured Shale Gas Reservoirs

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Huimin Wang ◽  
J. G. Wang ◽  
Feng Gao ◽  
Xiaolin Wang
Keyword(s):  
Shale Gas ◽  
Fracture Network ◽  
Gas Diffusion ◽  
Gas Production ◽  
Gas Reservoir ◽  
Two Phase ◽  
Fractured Zone ◽  
Shale Gas Reservoir ◽  
Diffusion Mechanisms

A shale gas reservoir is usually hydraulically fractured to enhance its gas production. When the injection of water-based fracturing fluid is stopped, a two-phase flowback is observed at the wellbore of the shale gas reservoir. So far, how this water production affects the long-term gas recovery of this fractured shale gas reservoir has not been clear. In this paper, a two-phase flowback model is developed with multiscale diffusion mechanisms. First, a fractured gas reservoir is divided into three zones: naturally fractured zone or matrix (zone 1), stimulated reservoir volume (SRV) or fractured zone (zone 2), and hydraulic fractures (zone 3). Second, a dual-porosity model is applied to zones 1 and 2, and the macroscale two-phase flow flowback is formulated in the fracture network in zones 2 and 3. Third, the gas exchange between fractures (fracture network) and matrix in zones 1 and 2 is described by a diffusion process. The interactions between microscale gas diffusion in matrix and macroscale flow in fracture network are incorporated in zones 1 and 2. This model is validated by two sets of field data. Finally, parametric study is conducted to explore key parameters which affect the short-term and long-term gas productions. It is found that the two-phase flowback and the flow consistency between matrix and fracture network have significant influences on cumulative gas production. The multiscale diffusion mechanisms in different zones should be carefully considered in the flowback model.

Understanding Shale Gas Flow Behavior Using Numerical Simulation

SPE Journal ◽  
2015 ◽  
Vol 20 (01) ◽  
pp. 142-154 ◽  
Author(s):  
Hao Sun ◽  
Adwait Chawathé ◽  
Hussein Hoteit ◽  
Xundan Shi ◽  
Lin Li
Keyword(s):  
Mass Transfer ◽  
Organic Matter ◽  
Shale Gas ◽  
Inorganic Material ◽  
Gas Transport ◽  
Knudsen Diffusion ◽  
Gas Production ◽  
Gas Reservoir ◽  
Shale Gas Reservoir ◽  
Flow Mechanisms

Summary Shale gas has changed the energy equation around the world, and its impact has been especially profound in the United States. It is now generally agreed that the fabric of shale systems comprises primarily organic matter, inorganic material, and natural fractures. However, the underlying flow mechanisms through these multiporosity and multipermeability systems are poorly understood. For instance, debate still exists about the predominant transport mechanism (diffusion, convection, and desorption), as well as the flow interactions between organic matter, inorganic matter, and fractures. Furthermore, balancing the computational burden of precisely modeling the gas transport through the pores vs. running full reservoir scale simulation is also contested. To that end, commercial reservoir simulators are developing new shale gas options, but some, for expediency, rely on simplification of existing data structures and/or flow mechanisms. We present here the development of a comprehensive multimechanistic (desorption, diffusion, and convection), multiporosity (organic materials, inorganic materials, and fractures), and multipermeability model that uses experimentally determined shale organic and inorganic material properties to predict shale gas reservoir performance. Our multimechanistic model takes into account gas transport caused by both pressure driven convection and concentration driven diffusion. The model accounts for all the important processes occurring in shale systems, including desorption of multicomponent gas from the organics' surface, multimechanistic organic/inorganic material mass transfer, multimechanistic inorganic material/fracture network mass transfer, and production from a hydraulically fractured wellbore. Our results show that a dual porosity, dual permeability (DPDP) model with Knudsen diffusion is generally adequate to model shale gas reservoir production. Adsorption can make significant contributions to original gas in place, but is not important to gas production because of adsorption equilibrium. By comparing triple porosity, dual permeability; DPDP; and single porosity, single permeability formulations under similar conditions, we show that Knudsen diffusion is a key mechanism and should not be ignored under low matrix pressure (Pematrix) cases, whereas molecular diffusion is negligible in shale dry gas production. We also guide the design of fractures by analyzing flow rate limiting steps. This work provides a basis for long term shale gas production analysis and also helps define value adding laboratory measurements.

4D multi-physical stress modelling during shale gas production: A case study of Sichuan Basin shale gas reservoir, China

2018 ◽  
Vol 167 ◽  
pp. 929-943 ◽  
Author(s):  
Haiyan Zhu ◽  
Xuanhe Tang ◽  
Qingyou Liu ◽  
Kuidong Li ◽  
Jialin Xiao ◽  
...  
Keyword(s):  
Shale Gas ◽  
Sichuan Basin ◽  
Physical Stress ◽  
Gas Production ◽  
Gas Reservoir ◽  
Shale Gas Reservoir

scholarly journals Simulation Study to Evaluate the Impact of Fracture Parameters on Shale Gas Productivity

2020 ◽  
Vol 39 (2) ◽  
pp. 432-442
Author(s):  
Abdul Majeed Shar ◽  
Waheed Ali Abro ◽  
Aftab Ahmed Mahesar ◽  
Kun Sang Lee
Keyword(s):  
Shale Gas ◽  
Gas Production ◽  
Simulation Software ◽  
Production Performance ◽  
Gas Reservoirs ◽  
Gas Reservoir ◽  
Shale Gas Reservoir ◽  
Fracture Parameters ◽  
Shale Gas Reservoirs ◽  
The Impact

The production from shale gas reservoirs has significantly increased due to technological advancements. The shale gas reservoirs are very heterogeneous and the heterogeneity has a significant effect on the quality and productivity of reservoirs. Hence, it is essential to study the behavior of such reservoirs for accurate modelling and performance prediction. To evaluate the impact of fracture parameters on shale gas reservoir productivity using CMG (Computer Modelling Group) stars simulation software was the main objective of this study. In this paper, a comprehensive analysis considering an example shale gas reservoir was conducted for production performance analysis considering uniform and non-uniform fractures configurations. Several simulations were performed by considering the multi-stage hydraulically fractured reservoir. The sensitivities conducted includes the different cases of moderate and severe heterogeneity along with variable fractures half-length, effect of changing fracture spacing, variable fracture conductivities. The simulation results showed that by increasing conductivity of fracture increases the gas production rate significantly. Moreover, cases of reservoir permeability heterogeneity were analyzed which show the significant effect on gas rate and on cumulative gas production. The results of this study can be used to improve the effectiveness in designing and developing of shale gas reservoirs and also to improve the accuracy of analyzing heterogeneous shale gas reservoir performance.

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