Modeling of pressure dissolution, proppant embedment, and the impact on long-term conductivity of propped fractures

Luo, Zhifeng; Zhang, Nanlin; Zhao, Liqiang; Liu, Fei; Liu, Pingli; Li, Nianyin

doi:10.1016/j.petrol.2019.106693

Cited by 17 publications

(11 citation statements)

References 21 publications

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“…These changes allow proppant to embed deeper into the fracture surface and reduce the conductivity of the fracture. Reducing fracture conductivity could impede or even prevent flow in the fractures, leading to significant reductions in overall production, e.g., thus, enhanced dissolution of calcite cement in response to high ionic strength hydraulic fracturing fluid may preclude using hydraulic fracturing fluids formulated from formation water . The dissolution of calcite could be minimized by ensuring that hydraulic fracturing fluid contains sufficient calcium to remain saturated with respect to calcite at reservoir temperature.…”

Section: Discussionsupporting

confidence: 86%

“…Reducing fracture conductivity could impede or even prevent flow in the fractures, leading to significant reductions in overall production, e.g., thus, enhanced dissolution of calcite cement in response to high ionic strength hydraulic fracturing fluid may preclude using hydraulic fracturing fluids formulated from formation water. 69 The dissolution of calcite could be minimized by ensuring that hydraulic fracturing fluid contains sufficient calcium to remain saturated with respect to calcite at reservoir temperature. In contrast, the dissolution of calcite cement in the rock adjacent to the fracture may increase porosity and permeability in the rock; however, we do not have sufficient data to assess the extent to which calcite dissolution penetrated into the rock.…”

Section: Discussionmentioning

confidence: 99%

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Ionic Strength and pH Effects on Water–Rock Interaction in an Unconventional Siliceous Reservoir: On the Use of Formation Water in Hydraulic Fracturing

et al. 2021

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Hydraulic fracturing employs a mixture of freshwater and chemical additives. Substituting produced formation water for freshwater conserves freshwater resources, but formation water possessing a high ionic strength may damage formations and inhibit production. Hydrothermal experiments were conducted at reservoir conditions (115 °C, 35 MPa) to evaluate geochemical interactions between reservoir rock and hydraulic fracturing fluid synthesized using formation water. The specific hypotheses tested are (1) progressively greater ionic strength and acidity enhance the solubility of carbonate and aluminosilicate minerals and (2) acidity is more important than ionic strength for carbonate solubility but ionic strength is more important for aluminosilicate mineral solubility. Experiments replicated a shut-in well in the Wall Creek Member of the Cretaceous Frontier Formation, Powder River Basin, Wyoming , an important unconventional reservoir composed of low permeability sandstones interbedded with organic-rich mudstones. The core was reacted for ∼650 h (27 days) with (1) acidic hydraulic fracturing fluid (pH ∼ 2.3) mixed from formation water spanning two orders of magnitude ionic strength (0.016, 0.16, and 1.13 mol/kg) and (2) hydraulic fracturing fluid (ionic strength 0.11 mol/kg) of circumneutral pH (7.3). Reaction with hydraulic fracturing fluid of progressively greater ionic strength increased calcite solubility, but acidity was more important to calcite solubility than ionic strength. Trends of aqueous silica, potassium, and magnesium are consistent with the dissolution of feldspar and/or quartz and the precipitation of clay. Ionic strength was more important than acidity for feldspar–clay equilibrium, the predominant aluminosilicate mineral reaction. Hydraulic fracturing fluid with a progressively greater ionic strength contained larger amounts of aqueous silica, enhancing the potential importance of secondary clay mineralization. Mineralogic evidence for dissolution was limited to calcite and feldspar; no secondary clay was observed. Formation water may be used for hydraulic fracturing fluids, provided that the potential benefits and deleterious effects of calcite and feldspar dissolution and secondary clay mineralization are assessed on a case-by-case basis.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Ionic Strength and pH Effects on Water–Rock Interaction in an Unconventional Siliceous Reservoir: On the Use of Formation Water in Hydraulic Fracturing

et al. 2021

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“…Luo et al 23 proposed a new long-term proppant fracture conductivity model by considering the stress sensitivity of artificial fractures. The model results show that high effective stress in the reservoir leads to proppant fracture, fine formation migration, as well as fracturing fluid damage, and finally, the conductivity of supporting fractures will gradually decrease.…”

Section: Results and Discussionmentioning

confidence: 99%

Pressure Drawdown Management Strategies for Multifractured Horizontal Wells in Shale Gas Reservoirs: A Review

Liu

et al. 2022

ACS Omega

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The flow capacity of shale gas reservoirs is easily impaired during the depletion process due to strong stress sensitivity. Thereby, an adequate production system, namely, the managed pressure drop method, has been widely introduced to the industrial practice application by decelerating the wellbore pressure drop rate and ultimately improving the long-term production process. This work presents a review of the pressure drawdown management mechanisms for shale gas formations. However, clarifying the water–shale interaction physical chemistry process and developing a mathematical model that accurately describes the water–shale interaction mechanism remain a challenge. Moreover, different classifications of the managed production simulation research approaches are discussed in detail. Each approach has its own merits and demerits. Among them, numerical simulations are commonly seen in cognizance of characterizing the managed pressure drawdown production period but are found to be relatively time-consuming and also computationally expensive. An optimized theoretical model is therefore essential because it can lead to a precise estimation of the ultimate long-term production and capture instantaneously the actual shale gas reservoir depletion phenomenon with various production systems compared to other available methods. The key influence of managed pressured production for single wells in shale reservoirs is elaborated as well. As observed from the current review, an accurate description of the pressure drop management mechanism is crucial for the theoretical model of the pressure control production process for shale gas wells. The influence of water–rock interaction on the managed pressure drawdown mechanism cannot be ignored. There have thus been works to improve and enhance it for use in theoretical models for shale formations. On the other hand, the advancement of theoretical models presents an opportunity for better representation of the managed pressure drop production process.

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“…However, several mechanisms may result in the loss of fracture conductivity, such as fines migration, proppant diagenesis, proppant crushing, − and proppant embedment, which is defined as proppant particles being embedded into the rock mass under pressure, causing a reduction in the fracture width and conductivity . Among these mechanisms, proppant embedment has been investigated via experiments, − numerical simulation, − and analytical modeling. − However, as has been confirmed by a larger number of laboratory experiments conducted with proppants to reproduce the in situ fracturing process, laboratory observations greatly overestimate the conductivity of real wells. , This great discrepancy may arise because in these studies, the underground rocks are often regarded as elastic/elastoplastic. , However, increasing reservoir depth, high temperature, high pressure, and high stress may result in extreme geological conditions, which may transform the mechanical properties of reservoir rocks from elastic to viscoelastic or viscoplastic . Hard rocks can also exhibit time-dependent deformation , under such extreme conditions.…”

Section: Introductionmentioning

confidence: 99%

Numerical Modeling of Proppant Embedment in Viscoelastic Formations with the Fractional Maxwell Model

et al. 2021

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Hydraulic fracturing is often used to exploit unconventional hydrocarbons, and proppants are usually added during hydraulic fracturing to keep the fractures induced open. Nevertheless, time-dependent proppant embedment has often been neglected in previous studies. In this survey, the fractional Maxwell model is first proposed to describe the viscoelastic deformation of tight sandstones. Then, the fractional rheological model is incorporated into the finite element framework in ABAQUS to establish a numerical model to investigate the time-dependent embedment of proppants in viscoelastic formations. Parameter sensitivity studies are also performed to investigate the influences of the mechanical characteristics of proppants and formation on the embedment depth. Several factors that influence proppant embedment are also discussed.

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Modeling of pressure dissolution, proppant embedment, and the impact on long-term conductivity of propped fractures

Cited by 17 publications

References 21 publications

Ionic Strength and pH Effects on Water–Rock Interaction in an Unconventional Siliceous Reservoir: On the Use of Formation Water in Hydraulic Fracturing

Ionic Strength and pH Effects on Water–Rock Interaction in an Unconventional Siliceous Reservoir: On the Use of Formation Water in Hydraulic Fracturing

Pressure Drawdown Management Strategies for Multifractured Horizontal Wells in Shale Gas Reservoirs: A Review

Numerical Modeling of Proppant Embedment in Viscoelastic Formations with the Fractional Maxwell Model

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