A Geomechanics-Coupled Embedded Discrete Fracture Model and its Application in Geothermal Reservoir Simulation

2019 ◽  
Author(s):  
Xiangyu Yu ◽  
Philip Winterfeld ◽  
Shihao Wang ◽  
Cong Wang ◽  
Lei Wang ◽  
...  
Keyword(s):  
Reservoir Simulation ◽  
Geothermal Reservoir ◽  
Fracture Model ◽  
Discrete Fracture Model ◽  
Discrete Fracture ◽  
Geothermal Reservoir Simulation

Development of an Embedded Discrete Fracture Model for Field-Scale Reservoir Simulation With Complex Corner-Point Grids

SPE Journal ◽  
2019 ◽  
Vol 24 (04) ◽  
pp. 1552-1575 ◽  
Author(s):  
Yifei Xu ◽  
Kamy Sepehrnoori
Keyword(s):  
Case Studies ◽  
Reservoir Simulation ◽  
Corner Point ◽  
Slight Modification ◽  
Fracture Model ◽  
Hydraulic Fractures ◽  
Field Scale ◽  
Discrete Fracture Model ◽  
Model Complex ◽  
Discrete Fracture

Summary Corner-point grids have the capability to model complex geological features, such as faults and irregular reservoir boundaries. As an industry standard, they are widely used to simulate different types of reservoirs, including conventional and unconventional reservoirs. It is necessary to effectively simulate natural or hydraulic fractures in such reservoirs. In this work, a discrete fracture model is developed to conveniently simulate fractures in geologically complex reservoirs represented by corner-point grids. The method is an extension of the embedded discrete fracture model (EDFM). We first present the difficulties in terms of geometrical calculations pertaining to corner-point grids, including the irregularity and degeneracy of block geometry and irregular connections between fracture segments. A general-purpose geometrical algorithm is developed to find the intersections between the matrix and fractures in corner-point grids. This algorithm properly handles the intersection between a general polyhedron and a general polygon, in which both the polyhedron and the polygon can be convex or concave. Transmissibility-factor formulations are also further developed for connections and intersections between fractures. The calculation of effective well indices in different situations is also discussed in detail. Several case studies are presented to illustrate the accuracy and applicability of the developed model in standard black-oil or compositional simulators. The accuracy of the developed model is demonstrated by comparing its simulation results with those of local-grid-refinement (LGR) models. It is also found that the accuracy of the EDFM is not sensitive to matrix gridding when the average size of gridblocks is similar. Field-scale studies using synthetic and realistic reservoir models are presented to illustrate the significance of fractures during secondary recovery. Existing simulators can directly be used in conjunction with the proposed approach with slight modification in simulation input, if the simulators have nonneighboring-connection (NNC) functionality. Through the case studies, the algorithms and methodology developed in this work are shown to be highly effective for the modeling of fractures in field-scale reservoir-simulation studies with complex corner-point grids.

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.

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