Analysis and Distribution of Proppant Recovered From Fracture Faces in the HFTS Slant Core Drilled Through a Stimulated Reservoir

Elliott, Sara J.; Gale, Julia

doi:10.15530/urtec-2018-2902629

Cited by 13 publications

(5 citation statements)

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“…Image logs in both horizontal wells reveal a consistent set of steeply dipping, conjugate fractures, with the primary population striking NW. A similar distribution of natural fractures is also observed in the core samples from well 6TW [19]. In addition to the natural fractures, E-W striking hydraulic fractures are also observed in post-stimulation core.…”

Section: Fracture Observationssupporting

confidence: 74%

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Stratigraphically Controlled Stress Variations at the Hydraulic Fracture Test Site-1 in the Midland Basin, TX

Kohli

Zoback

2021

Energies

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We investigated the relationship between stratigraphy, stress, and microseismicity at the Hydraulic Fracture Test Site-1. The site comprises two sets of horizontal wells in the Wolfcamp shale and a deviated well drilled after hydraulic fracturing. Regional stresses indicate normal/strike-slip faulting with E-W compression. Stress measurements in vertical and horizontal wells show that the minimum principal stress varies with depth. Strata with high clay and organic content show high values of the least compressive stress, consistent with the theory of viscous stress relaxation. By integrating data from core, logs, and the hydraulic fracturing stages, we constructed a stress profile for the Wolfcamp sequence, which predicts how much pressure is required for hydraulic fracture growth. We applied the results to fracture orientation data from image logs to determine the population of pre-existing faults that are expected to slip during stimulation. We also determined microseismic focal plane mechanisms and found slip on steeply dipping planes striking NW, consistent with the orientations of potentially active faults predicted by the stress model. This case study represents a general approach for integrating stress measurements and rock properties to predict hydraulic fracture growth and the characteristics of injection-induced microseismicity.

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Section: Fracture Observationssupporting

confidence: 74%

“…Pre-existing fractures at HFTS-1 are documented in image logs in wells 6SU, 6SM, and 7SU and the post-stimulation core recovered in well 6TW. A detailed description of the core and fractures are provided by Gale et al (2018) and Elliot and Gale (2018) [18,19]. Figure 7 shows the fracture data in the UW and MW units.…”

Section: Fracture Observationsmentioning

confidence: 99%

Stratigraphically Controlled Stress Variations at the Hydraulic Fracture Test Site-1 in the Midland Basin, TX

Kohli

Zoback

2021

Energies

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“…where Q f is the pump rate of the fracturing fluid, m 3 /s; Q p is the pump rate of the proppant, m 3 /s; ρ p and ρ f are densities of proppant and fracturing fluid, respectively, in kg/m 3 ; µ f is the fluid viscosity, Pa•s; d is the averaged diameter of the proppant, m; and w is the fracture width, m. The fracture width is the only unknown parameter that is presumably set to a value of 50 × d max (d max is the largest diameter of injected proppant), referring to the result from slant-core drilling through a stimulated shale reservoir [42] and numerical simulations [43]. When pure fluid is injected (alternative injection of proppant and pure fluid), the injection of pure fluid may rebalance the proppant dune, which may be calculated from [44] H…”

Section: Summary Of Numerical Models For Feature Extractionsmentioning

confidence: 99%

Emergency Pump-Rate Regulation to Mitigate Water-Hammer Effect—An Integrated Data-Driven Strategy and Case Studies

Hou,

Gong,

Sun

et al. 2024

Energies

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Pump-rate regulation is frequently used during hydraulic fracturing operations in order to maintain the pressure within a safe range. An emergency pump-rate reduction or pump shutdown is usually applied under the condition of sand screen-out when advancing hydraulic fractures are blocked by injected proppant and develop wellhead overpressure. The drastic regulation of the pump rate induces water-hammer effects—hydraulic shocks—on the wellbore due to the impulsive pressure. This wellbore shock damages the well integrity and then increases the risk of material leakage into water resources or the atmosphere, depending on the magnitude of the impulsive pressure. Therefore, appropriate emergency pump-rate regulation can both secure the fracturing operation and enhance well-completion integrity for environmental requirements—a rare mutual benefit to both sides of the argument. Previous studies have revealed the tube vibration, severe stress concentration, and sand production induced by water-hammer effects in high-pressure wells during oil/gas production. However, the water-hammer effect, the induced impulsive pressures, and the mitigation measures are rarely reported for hydraulic fracturing injections. In this study, we present a data-driven workflow integrating real-time monitoring and regulation strategies, which is applied in four field cases under the emergency operation condition (screen-out or near screen-out). A stepwise pump-rate regulation strategy was deployed in the first three cases. The corresponding maximum impulsive pressure fell in the range of 3.7~7.4 MPa. Furthermore, a sand screen-out case, using a more radical regulation strategy, induced an impulsive pressure 2 or 3 times higher (~14.7 MPa) than the other three cases. Compared with the traditional method of sharp pump-rate regulation in fields, stepwise pump-rate regulation is recommended to constrain the water-hammer effect based on the evolution of impulsive pressures, which can be an essential operational strategy to secure hydraulic fracturing and well integrity, especially for fracturing geologically unstable formations (for instance, formations near faults).

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“…During the calculation, the fracture width is the only unknown parameter that is presumably set to a value of 100 × d max (d max is the largest diameter of injected proppant) referring to the result of slant core drilling through a stimulated shale reservoir (Elliott and Gale, 2018). For an alternate pumping schedule (injecting pure fluid and slurry alternatively), the results of the Velocity model are discrete and are all treated as zeros as pure fluid is injected.…”

Section: Features For Proppant Transportmentioning

confidence: 99%

Evaluating essential features of proppant transport at engineering scales combining field measurements with machine learning algorithms

Hou¹,

Wang²,

Geng³

2022

Preprint

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The behaviours of the particle settlement, stratified flow and inception of settled particles are essential features that determine the proppant transport in low-viscosity fracturing fluids. Although great efforts have been made to characterize these features, limited research work is performed at field scales. To test the laboratory outcomes, we propose a machine-learning-based workflow to evaluate the essential features using the measurements obtained from shale gas fracturing wells. Over 430,000 groups of fracturing data (1 s time interval) are collected and pre-processed to extract the particle settlement, stratified flow and inception features during fracturing operations. The GRU and SVM algorithms, trained by these features, are applied to predict fracturing pressure. Error analysis (the root mean squared error, RMSE) is carried out to compare the contributions of different features to the pressure prediction, based on which the features and the corresponding calculations are evaluated. Our result shows that the stratified-flow feature (fracture-level) possesses better interpretations for the proppant transport, in which the Bi-power model helps to produce the best predictions. The settlement and inception features (particle-level) perform better in cases where the pressure fluctuates significantly. The features characterize the state of proppant transport, based on which the development of subsurface fracture is also analyzed. Moreover, our analyses of the remaining errors in the pressure-ascending cases suggest that (1) an introduction of the alternate-injection process, and (2) the improved calculation of proppant transport in highlyfilled fractures will be beneficial to both experimental observations and field applications.

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Analysis and Distribution of Proppant Recovered From Fracture Faces in the HFTS Slant Core Drilled Through a Stimulated Reservoir

Cited by 13 publications

References 0 publications

Stratigraphically Controlled Stress Variations at the Hydraulic Fracture Test Site-1 in the Midland Basin, TX

Stratigraphically Controlled Stress Variations at the Hydraulic Fracture Test Site-1 in the Midland Basin, TX

Emergency Pump-Rate Regulation to Mitigate Water-Hammer Effect—An Integrated Data-Driven Strategy and Case Studies

Evaluating essential features of proppant transport at engineering scales combining field measurements with machine learning algorithms

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