A Semianalytical Approach To Model Two-Phase Flowback of Shale-Gas Wells With Complex-Fracture-Network Geometries

SPE Journal ◽  
2017 ◽  
Vol 22 (06) ◽  
pp. 1808-1833 ◽  
Author(s):  
Ruiyue Yang ◽  
Zhongwei Huang ◽  
Gensheng Li ◽  
Wei Yu ◽  
Kamy Sepehrnoori ◽  
...  
Keyword(s):  
Shale Gas ◽  
Two Phase Flow ◽  
Fracture Network ◽  
Production Performance ◽  
Phase Flow ◽  
Water Production ◽  
Two Phase ◽  
Diagnostic Plots ◽  
Complex Fracture ◽  
Complex Fracture Network

Summary Two-phase flow is generally significant in the hydraulic-fracturing design of a shale-gas reservoir, especially during the flowback period. Investigating the gas- and water-production data is important to evaluate stimulation effectiveness. We develop a semianalytical model for multifractured horizontal wells by incorporating the two-phase flow in both shale matrix and fracture domains. The complex-fracture network, including both primary/hydraulic fractures and secondary/natural fractures, is modeled explicitly as discretized segments. The node-analysis approach is used to discretize the networks into a number of fracture segments and connected nodes, depending on the complexity of the fracture system. The two-phase flow is incorporated by iteratively correcting the relative permeability to gas/water for each fracture segment and capillary pressure at each node with the fracture depletion. The accuracy of the proposed model is confirmed by the numerical model. Subsequently, the early-time gas- and water-production performance is analyzed by use of various fracture geometries and network configurations. The model was also used to history match an actual multistage hydraulically fractured horizontal well in the Marcellus Shale during the flowback period. The research findings have shed light on the factors that substantially influence the gas- and water-production behavior during the flowback period. We also investigate the effects of fracture-network geometries and complexities on the gas/water-ratio (GWR) diagnostic plots. The results depict that the GWR behavior on the diagnostic plots is highly dependent on fracture-network geometry, configuration, and connectivity, which could assist in deriving the critical fracture properties affecting the production performance. This work extends the semianalytical approach previously proposed for modeling single-phase to two-phase flowback problems in unconventional reservoirs with various fracture-network geometries. The method is easier to set up and is less data-intensive than use of a numerical reservoir simulator, and is capable of providing a straightforward and flexible way to model complex-nonplanar-fracture networks in a multiphase-flow environment.

Numerical Simulation of Shale Gas Development Based on Complex Fracture Network Growth

2014 ◽  
Author(s):  
D.. Ye ◽  
C.. Yin ◽  
Y.. Li ◽  
S.. Wang ◽  
G.. Qin ◽  
...  
Keyword(s):  
Shale Gas ◽  
Hydraulic Fracture ◽  
Large Scale ◽  
Fracture Network ◽  
Production Performance ◽  
Network Growth ◽  
Stimulated Reservoir Volume ◽  
Well Production ◽  
Complex Fracture ◽  
Complex Fracture Network

Abstract Micro-seismic result has shown that compared to conventional reservoir, more complex fracture network will be generated in shale gas reservoirs after hydraulic fracturing stimulations, which provides key channels for shale gas to flow in economic rate. It is vitally important to recognize complex fracture network and model such complex system to better understand gas develop process, optimize hydraulic fracturing design, and determine development plans of shale gas reservoirs. Our proposed model enable realistic modeling of complex fracture network growth even with some uncertainty (SPE 157411), but it is possible to represent large-scale fracture network distribution in reservoir modeling and numerical simulation of shale gas development. In this paper, we used this proposed model to generate hydraulic fracture network distribution in shale formation, taking into account interaction between hydraulic fracture and actual large-scale natural fractures. Integrating hydraulic fracture network results and natural fractures in non-stimulated area, highly constrained unstructured gridding and a connection list are constructed, using the Discrete Fracturing Modeling (DFM) method. This model can effectively predict production performance. With real-world well data, the simulation system calibration is done, and the simulated well production performance has good agreement with real-world producing data. Using this simulation system, effective stimulated reservoir volume (ESRV) is also predicted. The proposed approach is capable of modeling complex fracture network propagation and predicting well producing rate, if information data on multi-scale pre-existing natural fracture is available. This approach provide one opportunity to predict well production performance and effective stimulated reservoir volume (ESRV), which is also significant for shale gas development plan.

scholarly journals A New Approach for Automatic Optimization of Complex Fracture Network in Shale Reservoirs

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Haibo Wang ◽  
Tong Zhou ◽  
Fengxia Li
Keyword(s):  
Shale Gas ◽  
Flow Model ◽  
Optimization Method ◽  
Fracture Network ◽  
Gas Reservoirs ◽  
Fracture Length ◽  
Complex Fracture ◽  
Shale Gas Reservoirs ◽  
Automatic Optimization ◽  
Complex Fracture Network

Abstract Shale gas reservoirs have gradually become the main source for oil and gas production. The automatic optimization technology of complex fracture network in fractured horizontal wells is the key technology to realize the efficient development of shale gas reservoirs. In this paper, based on the flow model of shale gas reservoirs, the porosity/permeability of the matrix system and natural fracture system is characterized. The fracture network morphology is finely characterized by the fracture network expansion calculation method, and the flow model was proposed and solved. On this basis, the influence of matrix permeability, matrix porosity, fracture permeability, fracture porosity, and fracture length on the production of shale gas reservoirs is studied. The optimal design of fracture length and fracture location was carried, and the automatic optimization method of complex fracture network parameters based on simultaneous perturbation stochastic approximation (SPSA) was proposed. The method was applied in a shale gas reservoir, and the results showed that the proposed automatic optimization method of the complex fracture network in shale gas reservoirs can automatically optimize the parameters such as fracture location and fracture length and obtain the optimal fracture network distribution matching with geological conditions.

The Research on Steering Fracture Numerical Simulation

2013 ◽  
Vol 734-737 ◽  
pp. 1488-1492
Author(s):  
Zhen Yu Liu ◽  
Li Hong Yao ◽  
Hu Zhen Wang ◽  
Cui Cui Ye
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Finite Element ◽  
Three Dimensional ◽  
Simulation Method ◽  
Production Performance ◽  
Phase Flow ◽  
Water Production ◽  
Two Phase ◽  
Fractured Well

The fractures after artificial steering fracturing appear in shades of curved surface. Aiming at the problem of steering fracture, in the paper, numerical simulation method under the condition of three-dimensional two-phase flow is presented based on finite element method. In this method, of steering fracture was achieved by adopting surface elements fractures and tetrahedron elements to describe formation. By numerical simulation, the change rule of oil and water production performance of steering fractures can be calculated, and then the steering fracture parameters can be optimized before fracturing. A new method was supplied for the numerical simulation of artificial fractured well.

scholarly journals Iterative Analytical Solutions for Nonlinear Two-Phase Flow with Gas Solubility in Shale Gas Reservoirs

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Xiaoji Shang ◽  
J. G. Wang ◽  
Zhizhen Zhang
Keyword(s):  
Capillary Pressure ◽  
Analytical Solutions ◽  
Shale Gas ◽  
Nonlinear Term ◽  
Two Phase Flow ◽  
Gas Production ◽  
Phase Flow ◽  
Gas Solubility ◽  
Production Rates ◽  
Two Phase

The governing equations of a two-phase flow have a strong nonlinear term due to the interactions between gas and water such as capillary pressure, water saturation, and gas solubility. This nonlinearity is usually ignored or approximated in order to obtain analytical solutions. The impact of such ignorance on the accuracy of solutions has not been clear so far. This study seeks analytical solutions without ignoring this nonlinear term. Firstly, a nonlinear mathematical model is developed for the two-phase flow of gas and water during shale gas production. This model also considers the effects of gas solubility in water. Then, iterative analytical solutions for pore pressures and production rates of gas and water are derived by the combination of travelling wave and variational iteration methods. Thirdly, the convergence and accuracy of the solutions are checked through history matching of two sets of gas production data: a China shale gas reservoir and a horizontal Barnett shale well. Finally, the effects of the nonlinear term, shale gas solubility, and entry capillary pressure on the shale gas production rate are investigated. It is found that these iterative analytical solutions can be convergent within 2-3 iterations. The solutions can well describe the production rates of both gas and water. The nonlinear term can significantly affect the forecast of shale gas production in both the short term and the long term. Entry capillary pressure and shale gas solubility in water can also affect shale gas production rates of shale gas and water. These analytical solutions can be used for the fast calculation of the production rates of both shale gas and water in the two-phase flow stage.

Evaluation of Void Fraction Correlations for the Statistical and Numerical Analysis of Two-Phase Flows Inside Producing Geothermal Wells

2008 ◽  
Author(s):  
A. A´lvarez del Castillo ◽  
E. Santoyo ◽  
O. Garci´a-Valladares ◽  
P. Sa´nchez-Upton
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Temperature Gradients ◽  
Production Performance ◽  
Phase Flow ◽  
Two Phase ◽  
Precise Knowledge ◽  
Geothermal Wells ◽  
Gas Void Fraction

The modeling of heat and fluid flow inside two-phase geothermal wells is a vital task required for the study of the production performance. Gas void fraction is one of the crucial parameters required for a better prediction of pressure and temperature gradients in two-phase geothermal wells. This parameter affects the correct matching between simulated and measured data. Modeling of two-phase flow inside wells is complex because two phases exist concurrently (exhibiting various flow patterns that depend on their relative concentrations, the pipe geometry, and the mass flowrate). A reliable modeling requires the precise knowledge of the two-phase flow patterns (including their transitions and some flow parameters). In this work, ten empirical correlations were used to estimate the gas void fraction in vertical-inclined pipes, and to evaluate their effect on the prediction of two-phase flow characteristics of some Mexican geothermal wells. High quality downhole pressure/ temperature logs collected from four producing geothermal wells were studied [Los Azufres, Mich. (Az-18); Los Humeros, Pue. (H-1), and Cerro Prieto, B.C. (M-90 and M-201)]. The pressure/ temperature gradients were simulated using an improved version of the wellbore simulator GEOPOZO, and the gas void fraction correlations. The simulated results were statistically compared with measured field data.

scholarly journals Experimental Investigation on the Hydraulic Characteristics of the Two-Phase Flow in the Intersecting Rock Fractures

Geofluids ◽  
2022 ◽  
Vol 2022 ◽  
pp. 1-14
Author(s):  
Chen Wang ◽  
Lujie Zhou ◽  
Yujing Jiang ◽  
Xuepeng Zhang ◽  
Jiankang Liu
Keyword(s):  
3D Model ◽  
Two Phase Flow ◽  
Rock Fracture ◽  
Flow Characteristics ◽  
Inertial Force ◽  
Fracture Network ◽  
Phase Flow ◽  
Hydraulic Characteristics ◽  
Two Phase ◽  
Flow Experiment

An appropriate understanding of the hydraulic characteristics of the two-phase flow in the rock fracture network is important in many engineering applications. To investigate the two-phase flow in the fracture network, a study on the two-phase flow characteristics in the intersecting fractures is necessary. In order to describe the two-phase flow in the intersecting fractures quantitatively, in this study, a gas-water two-phase flow experiment was conducted in a smooth 3D model with intersecting fractures. The results in this specific 3D model show that the flow structures in the intersecting fractures were similar to those of the stratified wavy flow in pipes. The nonlinearity induced by inertial force and turbulence in the intersecting fractures cannot be neglected in the two-phase flow, and the Martinelli-Lockhart model is effective for the two-phase flow in intersecting fractures. Delhaye’s model can be adapted for the cases in this experiment. The turbulence of the flow can be indicated by the values of C in Delhaye’s model, but resetting the appropriate range of the values of C is necessary.

scholarly journals A Hybrid Model for Simulating Fracturing Fluid Flowback in Tight Sandstone Gas Wells considering a Three-Dimensional Discrete Fracture

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Suran Wang ◽  
Yuhu Bai ◽  
Bingxiang Xu ◽  
Yanzun Li ◽  
Ling Chen ◽  
...  
Keyword(s):  
Production Rate ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Gas Production ◽  
Production Performance ◽  
Phase Flow ◽  
Fracture Permeability ◽  
Tight Sandstone ◽  
Two Phase ◽  
Discrete Fracture

Abstract Two-phase (gas+water) flow is quite common in tight sandstone gas reservoirs during flowback and early-time production periods. However, many analytical models are restricted to single-phase flow problems and three-dimensional fracture characteristics are seldom considered. Numerical simulations are good choices for this problem, but it is time consuming in gridding and simulating. This paper presents a comprehensive hybrid model to characterize two-phase flow behaviour and predict the production performance of a fractured tight gas well with a three-dimensional discrete fracture. In this approach, the hydraulic fracture is discretized into several panels and the transient flow equation is solved by the finite difference method numerically. A three-dimensional volumetric source function and superposition principle are deployed to capture the flow behaviour in the reservoir analytically. The transient responses are obtained by coupling the flow in the reservoir and three-dimensional discrete fracture dynamically. The accuracy and practicability of the proposed model are validated by the numerical simulation result. The results indicate that the proposed model is highly efficient and precise in simulating the gas/water two-phase flow and evaluating the early-time production performance of fractured tight sandstone gas wells considering a three-dimensional discrete fracture. The results also show that the gas production rate will be overestimated without considering the two-phase flow in the hydraulic fracture. In addition, the influences of fracture permeability, fracture half-length, and matrix permeability on production performance are significant. The gas production rate will be higher with larger fracture permeability at the early production period, but the production curves will merge after fracturing fluid flows back. A larger fracture half-length and matrix permeability can enhance the gas production rate.

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