High-Resolution Numerical Modeling of Complex and Irregular Fracture Patterns in Shale-Gas Reservoirs and Tight Gas Reservoirs

Olorode, Olufemi; Freeman, C. M.; Moridis, George J.; Blasingame, Thomas Alwin

doi:10.2118/152482-pa

Cited by 76 publications

(46 citation statements)

References 14 publications

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“…At this point, the improved model shows the transition indicating a boundary has been reached, but does not fall into a boundary dominated flow regime. This regime was also been observed by Olorode et al (2013) using high resolution simulation approach, and studied further by Bello (2011) who adopted reservoir simulation techniques investigating unit slopes in hydraulically fractured tight carbonate reservoirs. In terms of cumulative production the improved model matches the numerical reference solution with a maximum deviation of 3 to 9% for oil and generally less than 3% for gas flow.…”

Section: Model Validationmentioning

confidence: 63%

Efficient Semi-Analytical Engine for Performance Prediction of Unconventional Reservoirs

Olalotiti-Lawal

Friedel²

2015

SPE Eastern Regional Meeting

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Reliable and fast prediction of fractured well performance is vital for asset evaluation and prudent field development decision making in unconventional, low permeability oil and gas reservoirs. Simple low cost techniques such as decline curve analysis are ill suited of properly accounting for extended transient flow regimes. Numerical simulation techniques on the other hand are unrivaled in capturing geological details and high accuracy in fluid flow description. However, they suffer from high computational expense and often too little relevant data is available. Our objective is to develop an efficient semi-analytical solution that combines the advantages of speed and accuracy from both techniques for forecasts on single well, pad and even field level.Contrary to conventional oil and gas reservoirs, the tight reservoir characteristics allow for the application of analytical solutions to predict the behavior of fractured wells. The depth of investigation is small with spatial property variations having limited influence considering the large local pressure gradients. Fluid flow is mainly of transient nature and less dominated by multi-phase flow effects within the reservoir. Moreover, the typical configuration of an individual well with multiple fracture stage, entire pads with multiple wells or even entire assets allow the application of the superposition in space, providing a cheap means for accurate solution for multi-well problems.This paper presents a transient semi-analytical model based on a tri-linear formulation. It accurately captures fluid flow to a single or multiple fractured wells over the entire life cycle of production, from early linear flow to pseudo-steady boundary driven flow. It is applicable to oil or gas reservoirs with permeabilities ranging from nano-Darcies to approximately one milli-Darcy. It is capable of handling both the vertical and horizontal well type, with either single or multiple fracture stages respectively. Well-bore, stage and pad configurations can be freely parametrized. A tubing head pressure boundary condition is incorporated to model production from those wells more realistically. For shale type reservoirs, a desorption process is incorporated.The model is particularly suitable for quantitative evaluation of field development alternatives involving a large number of fractured wells. The accuracy compared to a high resolution numerical simulation model generally exceeds 90% with a computation speedup factor in the order of one hundred or more. Besides conventional benchmarking with a numerical reservoir simulator, actual field production data from the Marcellus and Eagleford shale wells shows the utility of the new solution. Being both fast and accurate, the technique presented in this paper is ideal for supporting high quality, cost efficient decision making which is crucial in the current low oil price environment.

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Section: Model Validationmentioning

confidence: 63%

Efficient Semi-Analytical Engine for Performance Prediction of Unconventional Reservoirs

Olalotiti-Lawal

Friedel²

2015

SPE Eastern Regional Meeting

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“…The benefits of high-resolution modeling of the detailed fracture patterns in shale by numerical methods include [29]: (1) accurate estimation of reserves and recoverable resources, (2) validation of analytical models, and (3) optimization of fracture and completion designs. The effect of natural fractures (positive/negative) on the stimulation of unconventional reservoirs has been well documented [30][31][32].…”

Section: Discrete Fracture Network Models and Limitationsmentioning

confidence: 99%

“…Another shortcoming is that such Cartesian grids cannot effectively represent complex and non-planar fracture networks. The latter can be better captured using unstructured grids to define Voronoi cells [29,45,46]. Some gains in computational time can be achieved using coarse scale parameters from numerical homogenization to upscale the non-transient regions in the reservoir model [47].…”

Section: Discrete Fracture Network Models and Limitationsmentioning

confidence: 99%

“…Further, reduction of computation time is typically achieved by applying so-called stencils to represent a multiple fractured well system by collocation of repetitive flow cells around a single or a small subset of the hydraulic fractures. The justification of such simplification typically were based on older completion techniques with well spacing of 120 m (394 ft), which reduced the effect of frac interference [29,44]. However, with today's tight frac spacing reduced to 1/10th (or even 1/20th in 2018 fracture treatments) of the spacing used in the cited studies, frac interference effects occur early in the well-life and preclude the use of stencils.…”

Section: Discrete Fracture Network Models and Limitationsmentioning

confidence: 99%

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Shale Reservoir Drainage Visualized for a Wolfcamp Well (Midland Basin, West Texas, USA)

Weijermars¹,

Harmelen²

2018

Energies

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Closed-form solution-methods were applied to visualize the flow near hydraulic fractures at high resolution. The results reveal that most fluid moves into the tips of the fractures. Stranded oil may occur between the fractures in stagnant flow zones (dead zones), which remain outside the drainage reach of the hydraulic main fractures, over the economic life of the typical well (30-40 years). Highly conductive micro-cracks would further improve recovery factors. The visualization of flow near hypothetical micro-cracks normal to the main fractures in a Wolfcamp well shows such micro-cracks support the recovery of hydrocarbons from deeper in the matrix, but still leave matrix portions un-drained with the concurrent fracture spacing of 60 ft (~18 m). Our study also suggests that the traditional way of studying reservoir depletion by mainly looking at pressure plots should, for hydraulically fractured shale reservoirs, be complemented with high resolution plots of the drainage pattern based on time integration of the velocity field.

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“…Freeman et al used numerical sensitivity studies to show the effect of mechanisms and factors on the performance of multifractured horizontal well [26][27][28]. Olorode et al employed numerical method to study the effect of fracture angularity and nonplanar fracture configurations on well performance [29]. Yu et al conducted numerical simulation to investigate the impact of fracture patterns, matrix permeability, cluster spacing, and fracture conductivity [30].…”

Section: Introductionmentioning

confidence: 99%

Pressure Transient Behavior of Horizontal Well with Time-Dependent Fracture Conductivity in Tight Oil Reservoirs

et al. 2017

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This work presents a discussion on the pressure transient response of multistage fractured horizontal well in tight oil reservoirs. Based on Green's function, a semianalytical model is put forward to obtain the behavior. Our proposed model accounts for fluid flow in four contiguous regions of the tight formation by using pressure continuity and mass conservation. The time-dependent conductivity of hydraulic fractures, which is ignored in previous models but highlighted by recent experiments, is also taken into account in our proposed model. We also include the effect of pressure drop along a horizontal wellbore. We substantiate the validity of our model and analyze the different flow regimes, as well as the effects of initial conductivity, fracture distribution, and geometry on the pressure transient behavior. Our results suggest that the decrease of fracture conductivity has a tremendous effect on the well performance. Finally, we compare our model results with the field data from a multistage fractured horizontal well in Jimsar sag, Xinjiang oilfield, and a good agreement is obtained.

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High-Resolution Numerical Modeling of Complex and Irregular Fracture Patterns in Shale-Gas Reservoirs and Tight Gas Reservoirs

Cited by 76 publications

References 14 publications

Efficient Semi-Analytical Engine for Performance Prediction of Unconventional Reservoirs

Efficient Semi-Analytical Engine for Performance Prediction of Unconventional Reservoirs

Shale Reservoir Drainage Visualized for a Wolfcamp Well (Midland Basin, West Texas, USA)

Pressure Transient Behavior of Horizontal Well with Time-Dependent Fracture Conductivity in Tight Oil Reservoirs

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