Efficient Modeling of Unconventional Well Performance with Millions of Natural and Hydraulic Fractures Using Embedded Discrete Fracture Model EDFM

2021 ◽  
Author(s):  
Wei Yu ◽  
Anuj Gupta ◽  
Ravimadhav N. Vaidya ◽  
Kamy Sepehrnoori
Keyword(s):  
Fractured Reservoirs ◽  
Horizontal Wells ◽  
Development Planning ◽  
Fracture Model ◽  
Computational Time ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Well Performance ◽  
Discrete Fracture Model ◽  
Discrete Fracture

Abstract The complexity of dynamic modeling for naturally fractured reservoirs has increased in recent years to incorporate more data and physics, as well as to handle advanced completion designs and development scenarios. While these complex models can provide more insight to difficult problems, they come with higher computational costs. Such a limitation prohibits an asset team from working with a large number of well/fracture scenarios that correctly represent geological uncertainty. This study presents a powerful non-intrusive Embedded Discrete Fracture Model (EDFM) method to efficiently handle millions of natural and hydraulic fractures with hundreds of horizontal wells, which has never been modeled in the literature. Specifically, we built a 3D geological model using a black oil reservoir simulator with 100 square miles in the horizontal area and 11 layers of 165 ft thickness. The total number of matrix cells without considering fractures is over 3 million. In total, 400 horizontal wells with well length of 6000 ft were modeled in two target layers. Each layer contains 200 wells. Each well has 112 hydraulic fractures with cluster spacing of 50 ft. The total number of hydraulic fractures is 44,800. In addition, we generated three cases with 10K, 100K and 1 million 3D natural fractures with dip angle from 70 to 90 degrees. For the case with 1 million natural fractures, the total number of cells is over 42 million. Well performance for the field example, with and without natural fractures, was investigated. This work adds significant value to the well and fracture spacing optimization process during field development planning. The non-intrusive EDFM method has been proven to be an efficient fracture modeling tool for simulating million-level complex hydraulic/natural fractures, which significantly improves accuracy and reduces computational time.

Three-Dimensional Projection-Based Embedded Discrete-Fracture Model for Compositional Simulation of Fractured Reservoirs

SPE Journal ◽  
2020 ◽  
Vol 25 (04) ◽  
pp. 2143-2161 ◽  
Author(s):  
Olufemi Olorode ◽  
Bin Wang ◽  
Harun Ur Rashid
Keyword(s):  
Fractured Reservoirs ◽  
Unconventional Reservoirs ◽  
Fracture Model ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Compositional Simulation ◽  
Discrete Fracture Model ◽  
Fracture Surfaces ◽  
Discrete Fracture ◽  
Simulation Results

Summary Most unconventional oil and gas reservoirs are known to have several natural fractures in different orientations, which are consistent with the prevailing stresses when they were created. The accurate and efficient modeling of natural and hydraulic fractures presents a significant computational challenge. In this work, we show the limitations of the embedded discrete-fracture model (EDFM) and present the first 3D projection-based EDFM (pEDFM) algorithm and compositional simulation studies with realistic fracture networks in a fully 3D space. The simulation results from this work indicate that the pEDFM presented can model realistic fractured unconventional reservoirs accurately and efficiently. To validate the model, we present some simplistic fracture cases that can be meshed and modeled easily using explicit-fracture modeling in commercial-reservoir simulators. From the cases studied, we observe that using progressively finer grids near the hydraulic-fracture surfaces helps to improve model accuracy because this allows us to capture the sharp pressure drops expected near these fracture surfaces. The simulation results show that, unlike EDFM, the robust pEDFM algorithm presented here is accurate even at the low fracture-conductivity values expected in many of these ubiquitous natural fractures. In this paper, we present the first full 3D compositional modeling with pEDFM. We demonstrate that our model can accurately and efficiently model multiply fractured horizontal wells in unconventional reservoirs, which have complex networks of thousands of fractures at various orientations.

Impact of Complex Fracture Networks on Rate Transient Behavior of Wells in Unconventional Reservoirs Based on Embedded Discrete Fracture Model

2021 ◽  
pp. 1-12
Author(s):  
Jiazheng Qin ◽  
Yingjie Xu ◽  
Yong Tang ◽  
Rui Liang ◽  
Qianhu Zhong ◽  
...  
Keyword(s):  
Flow Regimes ◽  
Natural Fracture ◽  
Fracture Model ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Fracture Networks ◽  
Discrete Fracture Model ◽  
Complex Fracture ◽  
Discrete Fracture ◽  
The Impact

Abstract It has recently been demonstrated that complex fracture networks (CFN) especially activated natural fractures (ANF) play an important role in unconventional reservoir development. However, traditional rate transient analysis (RTA) methods barely investigate the impact of CFN or ANF. Furthermore, the influence of CFN on flow regime is still ambiguous. Failure to consider these effects could lead to misdiagnosis of flow regimes and underestimation of original oil in place (OOIP). A novel numerical RTA method is therefore presented herein to improve the quality of reserves assessment. A new methodology is introduced. Propagating hydraulic fractures (HF) can generate different stress perturbations to allow natural fractures (NF) to fail, forming various ANF pattern. An embedded discrete fracture model (EDFM) of ANF is stochastically generated instead of local grid refinement (LGR) method to overcome the time-intensive computation time. These models are coupled with reservoir models using non-neighboring connections (NNCs). Results show that except for simplified models used in previous studies subjected to traditional concept of stimulated reservoir volume (SRV), in our study, the ANF region has been discussed to emphasis the impact of NF on simulation results. Henceforth, ANF could be only concentrated around the near-wellbore region, and it may also cover the whole simulation area. Obvious distinctions could be viewed for different kinds of ANF on diagnostic plots. Instead of SRV-dominated flow mentioned in previous studies, ANF-dominated flow developed in this work is shown to be more reasonable. Also, new flow regimes such as interference flow inside and outside activated natural fracture flow region (ANFR) are found. In summary, better evaluation of reservoir properties and reserves assessment such as OOIP are achieved based on our proposed model compared with conventional models. The novel RTA method considering CFN presented herein is an easy-to-apply numerical RTA technique that can be applied for reservoir and fracture characterization as well as OOIP assessment.

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 Discrete Fracture Model for Hydro-Mechanical Coupling in Fractured Reservoirs

2021 ◽  
Author(s):  
Xupeng He ◽  
Tian Qiao ◽  
Marwa Alsinan ◽  
Hyung Kwak ◽  
Hussein Hoteit
Keyword(s):  
Fractured Reservoirs ◽  
Fracture Model ◽  
System Of Nonlinear Equations ◽  
Fracture Permeability ◽  
Coupled Flow ◽  
General Applicability ◽  
Discrete Fracture Model ◽  
Mechanical Coupling ◽  
Flux Approximation ◽  
Discrete Fracture

Abstract The process of coupled flow and mechanics occurs in various environmental and energy applications, including conventional and unconventional fractured reservoirs. This work establishes a new formulation for modeling hydro-mechanical coupling in fractured reservoirs. The discrete-fracture model (DFM), in which the porous matrix and fractures are represented explicitly in the form of unstructured grid, has been widely used to describe fluid flow in fractured formations. In this work, we extend the DFM approach for modeling coupled flow-mechanics process, in which flow problems are solved using the multipoint flux approximation (MPFA) method, and mechanics problems are solved using the multipoint stress approximation (MPSA) method. The coupled flow-mechanics problems share the same computational grid to avoid projection issues and allow for convenient exchange between them. We model the fracture mechanical behavior as a two-surface contact problem. The resulting coupled system of nonlinear equations is solved in a fully-implicit manner. The accuracy and generality of the numerical implementation are accessed using cases with analytical solutions, which shows an excellent match. We then apply the methodology to more complex cases to demonstrate its general applicability. We also investigate the geomechanical influence on fracture permeability change using 2D rock fractures. This work introduces a novel formulation for modeling the coupled flow-mechanics process in fractured reservoirs, and can be readily implemented in reservoir characterization workflow.

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