scholarly journals The Investigation of Fracture Networks on Heat Extraction Performance for an Enhanced Geothermal System

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1635
Author(s):  
Linkai Li ◽  
Xiao Guo ◽  
Ming Zhou ◽  
Gang Xiang ◽  
Ning Zhang ◽  
...  
Keyword(s):  
Fracture Network ◽  
Production Performance ◽  
Heat Extraction ◽  
Geothermal System ◽  
Enhanced Geothermal System ◽  
Thermal Flow ◽  
Discrete Fracture Model ◽  
Complex Fracture ◽  
Thermal Breakthrough ◽  
Complex Fracture Network

Hydraulic fracturing is usually employed to create a complex fracture network to enhance heat extraction in the development of an enhanced geothermal system. The heat extraction depends on the heat conduction from the rock matrix to the flowing fractures and the heat convection through a complex fracture network. Therefore, the geometries of the fracture network have important influences on the thermal breakthrough. In this paper, a hydro-thermal coupling mathematical model considering a complex fracture network is established. The embedded discrete fracture model is adopted to explicitly model the individual fracture on the mass flow and heat transfer. The model is validated by analytical solutions. Fracture network parameters are changed systematically to investigate the effects of fracture network distribution including regular and complex shape on the thermal production performance. The results show that the increase of producing pressure differential, fracture number, and conductivity will cause an early thermal breakthrough. The strong variation in fracture conductivity, as well as spacing and orientation, will cause thermal flow channeling and decrease the efficiency of heat extraction. A modified connectivity field is proposed to characterize the spatial variation of fracture network connectivity, which can be used to infer the thermal flow path.

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.

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.

Semianalytical Production Simulation of Complex Hydraulic-Fracture Networks

SPE Journal ◽  
2013 ◽  
Vol 19 (01) ◽  
pp. 06-18 ◽  
Author(s):  
Wentao Zhou ◽  
Raj Banerjee ◽  
Bobby Poe ◽  
Jeff Spath ◽  
Michael Thambynayagam
Keyword(s):  
Fracture Network ◽  
Production Performance ◽  
Real Field ◽  
Well Drilling ◽  
Hydrocarbon Production ◽  
Complex Fracture ◽  
Reservoir Solution ◽  
Complex Fracture Network ◽  
Unconventional Resource ◽  
Semianalytical Method

Summary The application of horizontal-well drilling and multistage fracturing has become a norm in the industry to develop unconventional resources from ultratight formations. A complex fracture network generated in the presence of stress isotropy and pre-existing natural fractures immensely extends reservoir contact and improves hydrocarbon production. A semianalytical method is presented in this paper to simulate the production from such a complex fracture network. This method combines an analytical reservoir solution with a numerical solution on discretized fracture panels. The mathematics is briefly introduced. Numerous case studies are presented, from a simple planar fracture to a real-field example from the Barnett shale. Production behavior and the key flow regimes are discussed. With its simplicity, yet capturing the physics of the transient-production performance, this approach provides an accessible tool for people from multiple disciplines in unconventional-resource development to rapidly evaluate treated-well productivity and stimulation effectiveness.

Numerical Simulation of Complex Fracture Network Development by Hydraulic Fracturing in Naturally Fractured Ultratight Formations

2013 ◽  
Author(s):  
Hannes Hofmann ◽  
Tayfun Babadagli ◽  
Günter Zimmermann
Keyword(s):  
Fracture Network ◽  
Natural Fracture ◽  
Fracture Networks ◽  
Network Development ◽  
Complex Fracture ◽  
Fracture Patterns ◽  
Fracture Systems ◽  
Fracture Development ◽  
Complex Fracture Network ◽  
Treatment Designs

The creation of large complex fracture networks by hydraulic fracturing is imperative for enhanced oil recovery from tight sand or shale reservoirs, tight gas extraction, and Hot-Dry-Rock (HDR) geothermal systems to improve the contact area to the rock matrix. Although conventional fracturing treatments may result in bi-wing fractures, there is evidence by microseismic mapping that fracture networks can develop in many unconventional reservoirs, especially when natural fracture systems are present and the differences between the principle stresses are low. However, not much insight is gained about fracture development as well as fluid and proppant transport in naturally fractured tight formations. In order to clarify the relationship between rock and treatment parameters, and resulting fracture properties, numerical simulations were performed using a commercial Discrete Fracture Network (DFN) simulator. A comprehensive sensitivity analysis is presented to identify typical fracture network patterns resulting from massive water fracturing treatments in different geological conditions. It is shown how the treatment parameters influence the fracture development and what type of fracture patterns may result from different treatment designs. The focus of this study is on complex fracture network development in different natural fracture systems. Additionally, the applicability of the DFN simulator for modeling shale gas stimulation and HDR stimulation is critically discussed. The approach stated above gives an insight into the relationships between rock properties (specifically matrix properties and characteristics of natural fracture systems) and the properties of developed fracture networks. Various simulated scenarios show typical conditions under which different complex fracture patterns can develop and prescribe efficient treatment designs to generate these fracture systems. Hydraulic stimulation is essential for the production of oil, gas, or heat from ultratight formations like shales and basement rocks (mainly granite). If natural fracture systems are present, the fracturing process becomes more complex to simulate. Our simulation results reveal valuable information about main parameters influencing fracture network properties, major factors leading to complex fracture network development, and differences between HDR and shale gas/oil shale stimulations.

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