A pressure drop model of post-fracturing shut-in considering the effect of fracturing-fluid imbibition and oil replacement

WANG, Fei; Ruan, Yingqi; CHEN, Qiaoyun; Zhang, Shicheng

doi:10.1016/s1876-3804(21)60300-2

Cited by 13 publications

(3 citation statements)

References 25 publications

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“…The shale reservoir numerical simulation method − comprehensively considers the multiscale flow of shale oil, the stress-sensitive effect, and the coupling of the fluid flow and geomechanics in the shale reservoir. It can simulate the imbibition mechanism in the fracturing production process based on the finite difference method. − During numerical simulation, the imbibition effect in the reservoir matrix may be characterized by setting the capillary pressure and relative permeability. However, it is still difficult to take into account the influence of the chemical osmotic pressure in the simulation software.…”

Section: Methodsmentioning

confidence: 99%

Imbibition Mechanisms of Fracturing Fluid in Shale Oil Formation: A Review from the Multiscale Perspective

et al. 2023

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The breakthrough of shale oil in North America led to a worldwide energy revolution. Shale reservoirs show multiscale properties and a large proportion of nanopores compared to conventional reservoirs, which makes the imbibition mechanisms of fracturing fluids within shale reservoirs exceptionally complicated. For instance, the fracturing fluid shows a distinct imbibition behavior at different scales. Traditional models face significant challenges in imbibition characterization. Understanding the imbibition mechanisms in shale oil formations from a multiscale perspective can help to make full use of the positive effect and enhance oil recovery. We review imbibition mechanisms in shale reservoirs from the nanoscale to the reservoir scale. The imbibition principles in a single nanopore and the improvement of the traditional characterization models are clarified. Then, at the pore scale, we elaborate on the imbibition laws obtained from the microfluidic chip, pore network model, and direct simulations. We also outline the imbibition dynamics at the core scale, the influences of capillary forces and osmotic pressure, and the variations of the pore structure. Finally, the imbibition behavior at the reservoir scale and field examples considering the imbibition effect are introduced. We analyze the existing problems on each scale and discuss the future trends in this area. This work is expected to help readers systematically understand the mechanisms and behavior of fracturing fluid imbibition in shale oil reservoirs at different scales and accelerate the exploitation of shale resources.

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Section: Methodsmentioning

confidence: 99%

Imbibition Mechanisms of Fracturing Fluid in Shale Oil Formation: A Review from the Multiscale Perspective

et al. 2023

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“…Extensive studies have been conducted, which can be mainly divided into the following two aspects according to the distribution of fracturing fluid: (1) Due to capillary imbibition [4], osmotic pressure [5] and clay hydration [6] in matrix system, fracturing fluid is difficult to flow back after invading the micro and nano pores of the reservoir under the above single or multiple mechanisms, resulting in lower flowback rate. Some scholars believe that fracturing fluid retention underground is conducive to productivity, as the fluids will displace more oil and gas into fractures when they infiltrate the matrix [7,8]. However, there are also views that the retention fluids will form a filtration trap near hydraulic fractures, reducing oil phase permeability, and not conducive to long-term productivity [9,10].…”

Section: Introductionmentioning

confidence: 99%

Flowback Characteristics Analysis and Rational Strategy Optimization for Tight Oil Fractured Horizontal Well Pattern in Mahu Sag

Tian,

Liao,

Liu

et al. 2023

Processes

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With the deep development of tight reservoir in Mahu Sag, the trend of rising water cut during flowback concerns engineers, and its control mechanism is not yet clear. For this purpose, the integrated numerical model of horizontal well pattern from fracturing to production was established, and its applicability has been demonstrated. Then the flowback performance from child wells to parent wells and single well to well pattern was simulated, and the optimization method of reasonable flowback strategy was discussed. The results show that the formation pressure coefficient decreases as well patterns were put into production year by year, so that the seepage driving force of the matrix is weakened. The pressure-sensitive reservoir is also accompanied by the decrease of permeability, resulting in the increase of seepage resistance, which is the key factor causing the prolongation of flowback period. With the synchronous fracturing mode of well patterns, the stimulated reservoir volume (SRV) is greatly increased compared with that of single well, which improves the reservoir recovery. However, when the well spacing is less than 200 m, well interference is easy to occur, resulting in the rapid entry and outflow of fracturing fluid, and the increased water cut during flowback. Additionally, the well patterns in target reservoir should adopt a drawdown management after fracturing, with an aggressive flowback in the early stage and a slow flowback in the middle and late stage. With pressure depletion in different development stages, the pressure drop rate should be further slowed down to ensure stable liquid supply from matrix. This research can provide a theoretical guidance for optimizing the flowback strategy of tight oil wells in Mahu sag.

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“…Wang et al investigated the flow pattern of oil-water two phases in calcite pores through molecular dynamics and found that liquid-liquid slip existed at the oil-water interface (Yang, 2016;You et al, 2018). Tong et al used molecular dynamics to study the fluid behavior and flow in clay pores and concluded that the fluid properties in clay pores would affect the efficiency of oil recovery, indicating that diffusion, viscosity reduction and other factors are the main mechanisms affecting enhanced oil recovery (Tong et al, 2021;Wang et al, 2021). Shale fracturing has formed a complex porousfracture dual medium, in which the fluid flow state is still unclear (Ma, 2018;Ma et al, 2019;Zhai, 2021).…”

Section: Introductionmentioning

confidence: 99%

Fracturing fluid flow characteristics in shale gas matrix-fracture system based on NMR method

Wu,

Yang,

et al. 2023

Front. Energy Res.

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To understand the occurrence state of fracturing fluid in shale gas matrix-fracture system, an experimental method for evaluating fracturing fluid flow characteristics in matrix-fracture system was established. By using Nuclear Magnetic Resonance method, the flow characteristics of fracturing fluid were investigated from three processes of filtration, well shut-in and flowback. The T2 spectrum of fracturing fluid flow process and fracturing fluid saturation in matrix-fracture core model were clarified. The results demonstrate that the peak area of T2 spectra increases gradually during the filtration process, and the fracturing fluid quickly fills the fractures and matrix pores. During the well shut-in process, the fracturing fluid gradually flows from the fracture space to the matrix pores, and the signal of the matrix pores increases by 50.5%. During the flowback process, fracturing fluid flows out of the matrix and fracture. And when it reaches a stable state, the peak signal in the fracture decreases by 64.5% and the matrix signal reduces by 18.8%. The better the porosity and permeability characteristics of the core, the more likely the fracturing fluid is to stay in the formation and cannot be discharged. This paper would contribute to basic parameters for shale gas fracturing design and production strategy optimization.

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A pressure drop model of post-fracturing shut-in considering the effect of fracturing-fluid imbibition and oil replacement

Cited by 13 publications

References 25 publications

Imbibition Mechanisms of Fracturing Fluid in Shale Oil Formation: A Review from the Multiscale Perspective

Imbibition Mechanisms of Fracturing Fluid in Shale Oil Formation: A Review from the Multiscale Perspective

Flowback Characteristics Analysis and Rational Strategy Optimization for Tight Oil Fractured Horizontal Well Pattern in Mahu Sag

Fracturing fluid flow characteristics in shale gas matrix-fracture system based on NMR method

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