The study of fracture propagation in pre-acidized shale reservoir during the hydraulic fracturing

Zhao, Xing; He, Enjie; Guo, Jianchun; Zhu, Hehua; Wang, Hehua; He, Wei

doi:10.1016/j.petrol.2019.106488

Cited by 14 publications

(5 citation statements)

References 32 publications

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“…It means a lower injection flow rate may cause a fracture network with less fractures and narrow channels for water flowing through, whereas a higher injection flow rate may lead a developed fracture network that water could easily flow through. These results are in agreement with previous studies 8,30,33,39‐42 …”

Section: Discussionsupporting

confidence: 94%

Experimental and numerical studies on hydraulic fracturing characteristics with different injection flow rates in granite geothermal reservoir

Cheng

Zhang

et al. 2020

Energy Science & Engineering

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Geothermal energy has been widely proposed as a potential renewable energy to replace traditional fossil fuel energy. Hot dry rock (HDR) reservoirs were the main geothermal energy resources and usually consist of low‐permeability hard granite without fluid. Developing HDR requires water cyclically flowing between injection and production wells to extract heat energy. Hydraulic fracturing, as a key reservoir stimulation technology, can create the path of fluid cyclically flowing. However, few studies have investigated hydraulic induced artificial fractures in HDR geothermal formations. This paper investigated HDR geothermal reservoir stimulation characteristics and fracture patterns under different injection flow rates. Numerical simulations were conducted to model the laboratory tests. Results showed they were in good agreement, and this indicated the possibility of numerical simulation to predict hydraulic fracturing behavior under different injection flow rates. With the increase of injection flow rate, the fracture initiation pressures and breakdown pressures increased, and the propagation times and postfracturing pressures decreased. The fracture geometries were observed and analyzed, mean injection power was proposed, and results showed that it could be used to roughly estimate the fracture total lengths. Moreover, the fracture permeabilities based on the pressure data were calculated. These results can provide some reasonable advice for implementing reservoir stimulations on application to field‐scale HDR operation.

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Section: Discussionsupporting

confidence: 94%

Experimental and numerical studies on hydraulic fracturing characteristics with different injection flow rates in granite geothermal reservoir

Cheng

Zhang

et al. 2020

Energy Science & Engineering

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“…Acidic dissolution may have a positive influence in this process. On one side, acidic dissolution-induced pores and microfractures contribute to increase the porosity of a rock, which causes the chemical damage of the rock, resulting in the reduction of the uniaxial tensile strength [80,81]. Equation (4) shows a chemical damage variable dependent on porosity (D ∅ ), which reflects the chemical damage due to the interaction between acidic fluids and shale [82,83].…”

Section: Increment Of the Density Of Fracture Networkmentioning

confidence: 99%

New Insight into Enhancing Organic-Rich Shale Gas Recovery: Shut-in Performance Increased through Oxidative Fluids

Cheng¹,

You

Jia

et al. 2023

Energies

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Oxidizing stimulation of organic-rich shale reservoirs, as a supplement of hydraulic fracturing, was proposed to enhance shale gas recovery. Previous publications revealed that the interaction between organic-rich shale and oxidative fluids causes the components’ dissolution, which induces lots of pores and microfractures, resulting in rock microfracturing without confined pressure and associated increments of the matrix permeability, and improving unpropped fracture conductivity. However, the enhancement of shale gas recovery with oxidative fluids still lacks an implementation clue targeted for specific engineering problems. In recent years, water–rock interaction inducing microfractures indicates a positive effect of retained fracturing fluid on the stimulation after the fracturing operation, which sheds light in the enhancement of shale gas production by shut-in. The objectives of this study are to provide a new perspective whereby the shut-in performance to enhance shale gas recovery could be increased by the injection of oxidative fluids into the formation during the fracturing operation. Firstly, the mechanisms of shut-in performance increased by oxidative dissolution, which illustrate the increment of the density of fracture networks, the improvement of fracture network conductivity, and the promotion of gas desorption and diffusivity, are demonstrated. Then, the feasibility of using oxidative fluids to increase shut-in performance, which follows the geological and engineering characteristics of organic-rich shale reservoirs, is evaluated. Finally, according to the analysis of production performance for two typical types of shale gas wells, in which one is a low gas production and a high fracturing fluid recovery (LGP-HFR) and the other is a high gas production and a low fracturing fluid recovery (HGP-LFR), a shut-in strategy with oxidative fluids to enhance shale gas recovery is developed. This indicates that the injection of oxidative fluids during the fracturing operation may become a promising and cost-effective approach to enhance shale gas recovery.

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“…The first phase of hydraulic fracturing (Figure ) is comprised of injecting a highly acidic “spearhead” fluid (7.5–15% HCl, pH < 0) intended to clean out the wellbore and dissolve reactive minerals (e.g., carbonates) in the near wellbore region to create pore openings that aid in fracture propagation. ,, High flow rates with associated small fracture apertures result in Pe ≫ 1 while the low-pH oxic environment results in extraordinarily high Da for reactive minerals. Acid from the initial spearhead is consumed and diluted over the steps of the fracturing operation, reducing its efficacy away from the wellbore, thereby resulting in a decrease in Da .…”

Section: The Hydraulic Fracturing Processmentioning

confidence: 99%

A Critical Review of the Physicochemical Impacts of Water Chemistry on Shale in Hydraulic Fracturing Systems

Khan

Spielman-Sun

Jew

et al. 2021

Environ. Sci. Technol.

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Hydraulic fracturing of unconventional hydrocarbon resources involves the sequential injection of a high-pressure, particle-laden fluid with varying pH’s to make commercial production viable in low permeability rocks. This process both requires and produces extraordinary volumes of water. The water used for hydraulic fracturing is typically fresh, whereas “flowback” water is typically saline with a variety of additives which complicate safe disposal. As production operations continue to expand, there is an increasing interest in treating and reusing this high-salinity produced water for further fracturing. Here we review the relevant transport and geochemical properties of shales, and critically analyze the impact of water chemistry (including produced water) on these properties. We discuss five major geochemical mechanisms that are prominently involved in the temporal and spatial evolution of fractures during the stimulation and production phase: shale softening, mineral dissolution, mineral precipitation, fines migration, and wettability alteration. A higher salinity fluid creates both benefits and complications in controlling these mechanisms. For example, higher salinity fluid inhibits clay dispersion, but simultaneously requires more additives to achieve appropriate viscosity for proppant emplacement. In total this review highlights the nuances of enhanced hydrogeochemical shale stimulation in relation to the choice of fracturing fluid chemistry.

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The study of fracture propagation in pre-acidized shale reservoir during the hydraulic fracturing

Cited by 14 publications

References 32 publications

Experimental and numerical studies on hydraulic fracturing characteristics with different injection flow rates in granite geothermal reservoir

Experimental and numerical studies on hydraulic fracturing characteristics with different injection flow rates in granite geothermal reservoir

New Insight into Enhancing Organic-Rich Shale Gas Recovery: Shut-in Performance Increased through Oxidative Fluids

A Critical Review of the Physicochemical Impacts of Water Chemistry on Shale in Hydraulic Fracturing Systems

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