Nanopores to megafractures: Current challenges and methods for shale gas reservoir and hydraulic fracture characterization

The complex fracture network formed by volume fracturing of shale gas reservoir is very important to the effect of reservoir reconstruction. The existence of bedding interface will change the propagation path of the hydraulic fracture in the vertical direction and affect the reservoir reconstruction range in the height direction. The three-point bending test is used to test and study the mechanical parameters and fracture propagation path of natural outcrop shale core. On this basis, a two-dimensional numerical model of hydraulic fracture interlayer propagation is established based on the cohesive element. Considering the fluid-solid coupling in the process of hydraulic fracturing, the vertical propagation path of hydraulic fracture under different reservoir properties and construction parameters is simulated. According to the results, the strength of the bedding interface is the weakest, the crack propagation resistance along the bedding interface is the smallest, and the crack propagation path is straight. When the crack does not propagate along the bedding interface, the fracture propagation resistance is large, and the fracture appears as an arc propagation path or deflection. The difference between vertical stress and minimum horizontal stress difference, interlayer stress difference and interface stiffness will have a significant impact on the propagation path of vertical fractures. Large injection rate and high viscosity fluid injection are helpful for vertical fractures to pass through the bedding interface, and low viscosity fracturing fluid is helpful to open the bedding interface. This research work is helpful to better understand the characteristics of bedding shale and the interlayer propagation law of vertical fractures, and to form the stimulation strategy of shale gas reservoir.

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Development of Production-Forecasting Model Based on the Characteristics of Production Decline Analysis Using the Reservoir and Hydraulic Fracture Parameters in Montney Shale Gas Reservoir, Canada

Geofluids ◽

10.1155/2021/6613410 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Hyeonsu Shin ◽

Viet Nguyen-Le ◽

Min Kim ◽

Hyundon Shin ◽

Edward Little

Keyword(s):

Shale Gas ◽

Hydraulic Fracture ◽

History Matching ◽

Forecasting Model ◽

Gas Reservoir ◽

Shale Gas Reservoir ◽

Production Forecasting ◽

Fracture Parameters ◽

Decline Rate ◽

Cumulative Production

This study developed a production-forecasting model to replace the numerical simulation and the decline curve analysis using reservoir and hydraulic fracture data in Montney shale gas reservoir, Canada. A shale-gas production curve can be generated if some of the decline parameters such as a peak rate, a decline rate, and a decline exponent are properly estimated based on reservoir and hydraulic fracturing parameters. The production-forecasting model was developed to estimate five decline parameters of a modified hyperbolic decline by using significant reservoir and hydraulic fracture parameters which are derived through the simulation experiments designed by design of experiments and statistical analysis: (1) initial peak rate ( P hyp ), (2) hyperbolic decline rate ( D hyp ), (3) hyperbolic decline exponent ( b hyp ), (4) transition time ( T transition ), and (5) exponential decline rate ( D exp ). Total eight reservoir and hydraulic fracture parameters were selected as significant parameters on five decline parameters from the results of multivariate analysis of variance among 11 reservoir and hydraulic fracture parameters. The models based on the significant parameters had high predicted R 2 values on the cumulative production. The validation results on the 1-, 5-, 10-, and 30-year cumulative production data obtained by the simulation showed a good agreement: R 2 > 0.89 . The developed production-forecasting model can be also applied for the history matching. The mean absolute percentage error on history matching was 5.28% and 6.23% for the forecasting model and numerical simulator, respectively. Therefore, the results from this study can be applied to substitute numerical simulations for the shale reservoirs which have similar properties with the Montney shale gas reservoir.

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Hydraulic Fracture Design with a Proxy Model for Unconventional Shale Gas Reservoir with Considering Feasibility Study

Energies ◽

10.3390/en12020220 ◽

2019 ◽

Vol 12 (2) ◽

pp. 220 ◽

Cited By ~ 1

Author(s):

Kyoungsu Kim ◽

Jonggeun Choe

Keyword(s):

Hydraulic Fracturing ◽

Shale Gas ◽

Hydraulic Fracture ◽

Robust Regression ◽

Economic Feasibility ◽

Gas Reservoir ◽

Horizontal Drilling ◽

Shale Gas Reservoir ◽

Proxy Model ◽

Reservoir Simulator

Shale gas is a natural gas trapped in shale formation and is being actively developed in North America. Due to the low permeability of a shale gas reservoir in the range from 10−8 to 10−6 Darcy, horizontal drilling and multi-stage hydraulic fracturing are needed for its development. This paper presents a fast and reliable proxy model to forecast shale gas productions and an optimum hydraulic fracturing design for its development. The proxy model uses a robust regression scheme and can replace a commercial reservoir simulator. The proxy model proposed can determine the influence of impact factors on the production at each production time. The calculation speed of the proposed proxy model is about 1.4 million times faster than that of a reservoir simulator compared. The most economical hydraulic fracture design using the proxy model has a length of 168 m at each stage, which is determined by examining a large number of hydraulic fracturing designs considering economic feasibility.

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