Analytical Modeling of Flow Behavior for Wormholes in Naturally Fractured–Vuggy Porous Media

In the past few decades, scholars have made great breakthroughs in the study of well test analysis of carbonate rock. The previous studies are based on horizontal wells, straight wells, fractured wells, and inclined wells. With the development of fracturing technology, acid fracturing technology is considered to be the most effective measure to develop carbonate reservoirs. As the carbonate rock is easily dissolved in carbonic acid, multi-branched fractures will be produced near a vertical well. This article presented a semi-analytical model for multi-branched fractures in naturally fractured-vuggy reservoirs for the first time, which laid a theoretical foundation for solving well test analysis for finite conductivity multi-branched fractures. The model can quantify the wellbore flow pressure and applied to obtain more parameters reflecting comprehensive flow characteristics through using history matching procedure. The results were compared with numerical simulation and the existing analytical solutions of a single fracture model. Then in this paper, flow characteristics are recognized and there are five flow regimes found in the type curves, e.g. bi-linear flow region, linear flow region, inter-porosity flow region between vugs and fractures, inter-porosity region between matrix and fractures, and radial flow region. Finally, the influence factors analysis shows fracture number will mainly affect flow behavior of bi-linear flow and linear flow. The angle analysis showed that as the fractures were closer, their interaction became stronger. The conductivity would seriously affect the flow behavior in the early time. Linear flow cannot be observed when the conductivity is less than 1 and bi-linear flow cannot be observed when the conductivity is more than 20. And the effect of fracture length on flow behavior occurs in the early time. Bi-linear flow and linear flow characteristics cannot be observed when the fracture length is reduced.

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“…Some reservoir models for vertical wells in carbonate reservoirs have been studied 4 , 5 , 23 , 34 . Figure 1c shows the flow process.…”

Section: Mathematical Modelsmentioning

confidence: 99%

“…In 2014, Wang et al . 34 presented a multi-branched model with an infinite conductivity, however, the flow in the fractures was not considered in their model so that the regime in the early time was not observed. In this paper, a finite conductivity multi-branched fractures model for carbonate reservoirs was studied in details.…”

Section: Introductionmentioning

confidence: 99%

A Novel Semi-Analytical Model for Multi-branched Fractures in Naturally Fractured-Vuggy Reservoirs

Wang

Chen

Xia

2018

Sci Rep

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“…Shaoul et al [32] proposed a numerical model of a vertical fractured well with multiple hydraulic fractures and investigated the pressure behavior of a vertical fractured well. Restrepo and Tiab [33] and Wang et al [34] established semi-analytical models of a vertical fractured well with multiple infinite-conductivity hydraulic fractures. Ren and Guo [35] and Luo and Tang [36] proposed semi-analytical models of a vertical fractured well with multiple finite-conductivity hydraulic fractures.…”

Section: Introductionmentioning

confidence: 99%

Transient-Flow Modeling of Vertical Fractured Wells with Multiple Hydraulic Fractures in Stress-Sensitive Gas Reservoirs

Guo

Sun

Peng³

et al. 2019

Applied Sciences

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Massive hydraulic fracturing of vertical wells has been extensively employed in the development of low-permeability gas reservoirs. The existence of multiple hydraulic fractures along a vertical well makes the pressure profile around the vertical well complex. This paper studies the pressure dependence of permeability to develop a seepage model of vertical fractured wells with multiple hydraulic fractures. Both transformed pseudo-pressure and perturbation techniques have been employed to linearize the proposed model. The superposition principle and a hybrid analytical-numerical method were used to obtain the bottom-hole pseudo-pressure solution. Type curves for pseudo-pressure are presented and identified. The effects of the relevant parameters (such as dimensionless permeability modulus, fracture conductivity coefficient, hydraulic-fracture length, angle between the two adjacent hydraulic fractures, the difference of the hydraulic-fracture lengths, and hydraulic-fracture number) on the type curve and the error caused by neglecting the stress sensitivity are discussed in detail. The proposed work can enrich the understanding of the influence of the stress sensitivity on the performance of a vertical fractured well with multiple hydraulic fractures and can be used to more accurately interpret and forecast the transient pressure.

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“…Jia et al [14] developed a flowing model of well test analysis for porous-vuggy carbonate reservoirs. After that, a analytical model for wormholes in fractured-vuggy carbonate reservoirs is developed by Wang et al [15]. Chen et al [16] used boundary Well in Fractured-Vuggy Carbonate Reservoirs element method for modeling of fractured-vuggy reservoirs with large-scale caves and obtained the PTA type curves.…”

Section: Introductionmentioning

confidence: 99%

“…According to above mentioned models in fractured-vuggy carbonate reservoirs, two main models are used to describe and study the flow process in fractured-vuggy carbonate reservoirs: (1) triple porosity and single permeability model [15], [19]. The model considers the vug system as a continuum medium, treats fracture system as pathways directly connected to the wellbore, and considers the matrix and vug systems connect to the fracture system.…”

Section: Introductionmentioning

confidence: 99%

Pressure Transient Analysis for Finite Conductivity Multi-staged Fractured Horizontal Well in Fractured-Vuggy Carbonate Reservoirs

Wei¹

2016

OGCE

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Transient pressure analysis has been considered as a robust method to identify the flow behaviors, estimate reservoir parameters and hydraulic fracturing parameters. Compared with conventional clastic reservoirs, complex pore systems in fractured-vuggy carbonate reservoirs are posing significant research challenges. Although pressure transient analysis(PTA) models for different style wells in carbonate reservoirs have been widely studied, limited study has been conducted for multi-fractured horizontal well (MFHW) in these reservoirs. Thus, this paper is an investigation on PTA for MFHW of fractured-vuggy carbonate reservoirs. Based on source function theory, mirrors reflection and superposition principle,, the finite conductive MFHW's bottom-hole pressure solution for fractured-vuggy carbonate reservoirs is obtained by the Laplace transform and the Stehfest inversion method. Log-log type curves are drawn by numerical algorithms and eight flow regimes are identified. Finally the influences of sensitivity parameters such as fracture number, fracture spacing, half length of fracture, storativity ratio, inter-porosity flow coefficient on unsteady flow behaviors of MFHW are discussed in depth.

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Analytical Modeling of Flow Behavior for Wormholes in Naturally Fractured–Vuggy Porous Media

Cited by 30 publications

References 30 publications

A Novel Semi-Analytical Model for Multi-branched Fractures in Naturally Fractured-Vuggy Reservoirs

A Novel Semi-Analytical Model for Multi-branched Fractures in Naturally Fractured-Vuggy Reservoirs

Transient-Flow Modeling of Vertical Fractured Wells with Multiple Hydraulic Fractures in Stress-Sensitive Gas Reservoirs

Pressure Transient Analysis for Finite Conductivity Multi-staged Fractured Horizontal Well in Fractured-Vuggy Carbonate Reservoirs

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