ORCID Profile
0000-0003-1722-4265
Current Organisation
The University of Auckland
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Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 06-2022
Publisher: Research Square Platform LLC
Date: 30-11-2022
DOI: 10.21203/RS.3.RS-1525036/V4
Abstract: Hydraulic fracturing is a coupled multi-physics and scale-dependent process requiring an extensive numerical-laboratory appraisal to assess feasibility in the field. Developing a robust model of hydraulic fracture propagation requires knowledge of the time evolution of the fracture’s geometrical attributes, e.g., width/aperture and length/radius. However, it is inherently challenging to directly measure even the simplest fracture attribute (i.e., radius) within a rock s le subjected to in-situ stresses in the laboratory, let alone in the field. In this study, an analytical model ( R d ) is developed based on Poiseuille’s law. Scaling laws and dimensional analysis are used to define propagation regimes and non-linear hydro-mechanical coupling is accounted for the near-tip region. This model aims to predict the time evolution of radius for a homothetic penny-shaped hydraulic fracture when the fracture opening, and internal pressure gradient are known. Based on the available experimental data from literature, we quantify the growth of the fracture radius using linear elastic fracture growth model ( R E ) tip asymptotic solutions ( R V and R T ) semi-analytical solutions ( R S ) and the model R d . A comparison of the four analytical models with published experimental data reveal that (i) the asymptotic solutions are limited to linearly elastic and homogeneous materials, i.e., PMMA (ii) the semi-analytical solutions ( R S ) is only suitable for late-time propagation (iii) the performance of the linear elastic model ( R E ) poorly matches the experimental data, especially for unstable propagation situations (iv) the new R d model takes advantage of a robust reconstruction of the temporal radius growth of hydraulic fracture problems under realistic stress conditions, and including multiscale propagation regimes, cohesive effects, as well as stable and unstable propagation regimes of geomaterials.
Publisher: California Digital Library (CDL)
Date: 18-02-2023
DOI: 10.31223/X5PH0S
Abstract: Understanding the propagation of hydraulic fracture (HF) is essential for effectively stimulating the hydrocarbon production of unconventional reservoirs. Hydraulic fracturing may induce distinct failure modes within the formation, depending on the rheology of the solid and the in-situ stresses. A brittle-to-ductile transition of HF is thus anticipated with increasing depth, although only scarce data are available to support this hypothesis. Here we carry out laboratory hydraulic fracturing experiments in artificial geomaterials exhibiting a wide range of rheology: cubic s les 50x50x50 mm3 in size are subjected to true triaxial stresses with either a low (σv = 6.5 MPa, σH =3 MPa, and σh =1.5MPa), or a higher (15 MPa, 10 MPa, and 5MPa) confinement. The 3D strains induced by hydraulic fracturing are monitored and interpreted X-ray Computed Tomography (CT) imaging is used to document the HF geometry and viscoelastic modelling of the tested materials is also conducted to explain the distinct geometry of hydraulic fracture subjected to the stress state. Finally, a correlation between the normalized fracture area (AFN) and the brittleness index (BI) of tested s les is introduced. Our results reveal that: (i)The intermediate stress plays a profound role in hydraulic fracture propagation subjected to the normal faulting regimes (i.e., the transitional intermediate strain observed from brittle to ductile s les) (ii) The orientation angle of hydraulic fracture is highly inclined to the maximum horizontal σH (or vertical σv) stresses in brittle/semi-brittle s les as BI decreases, the angle inclination is reduced for that of semi-ductile s les, finally reaches to zero (parallel to σH and σv) in ductile s le. (iii) The normalized fracturing area (AFN) decreases as the decrease of BI among different s les under either low or higher confinement. The results of viscoelastic modelling explain the distinct characteristics of hydraulic fracturing induced deformation among the tested s les subjected to true triaxial stress state. This study reveals the importance of understanding the underground brittle-to-ductile behaviour of hydraulic fracture prior to the field implementation.
Publisher: Springer Science and Business Media LLC
Date: 20-08-2019
Publisher: Society of Petroleum Engineers (SPE)
Date: 30-06-2021
DOI: 10.2118/206710-PA
Abstract: Applying the realistic cementation exponent (m) in Archie’s equation is critical for reliable fluid-saturation calculation from well logs in shale formations. In this study, the cementation exponent was determined under different confining pressures using a high-salinity brine to suppress the surface conductivity related to the cation-exchange capacity of clay particles. A total of five Ordovician shale s les from the Canning Basin, Australia, were used for this study. The shale s les are all illite-rich with up to 60% clay content. Resistivity and porosity measurements were performed under a series of confining pressures (from 500 to 8,500 psi). Nuclear magnetic resonance (NMR) was used to obtain porosity and pore-size distribution and to detect the presence of residual oil. The complex impedance of s les was determined at 1 kHz to verify the change in pore-size distribution using the POLARIS model (Revil and Florsch 2010). The variation of shale resistivity and the Archie exponent m at different pressures is caused by the closure of microfractures at 500 psi, the narrowing of mesopores/macropores between 500 and 3,500 psi, and the pore-throat reduction beyond 3,500 psi. This study indicates that unlike typical reservoirs, the Archie exponent m for shale is sensitive to depth of burial because of the soft nature of the shale pore system. An equation is developed to predict m under different pressures after microfracture closure. Our study provides recommended experimental procedures for the calculation of the Archie exponent m for shales, leading to improved accuracy for well-log interpretation within shale formations when using Archie-based equations.
Publisher: Research Square Platform LLC
Date: 15-07-2022
DOI: 10.21203/RS.3.RS-1525036/V3
Abstract: Hydraulic fracturing is a coupled multi-physics and scale-dependent process requiring an extensive numerical-laboratory appraisal to assess feasibility in the field. Developing a robust model of hydraulic fracture propagation requires knowledge of the time evolution of the fracture’s geometrical attributes, e.g., width/aperture and length/radius. However, it is inherently challenging to directly measure even the simplest fracture attribute (i.e., radius) within a rock s le subjected to in-situ stresses in the laboratory, let alone in the field. In this study, an analytical model is developed to predict the time evolution of the radius for a penny-shaped hydraulic fracture. This model ( R d ) predicts the fracture opening and internal pressure gradient using Poiseuille’s law and assuming a self-similar propagation. Scaling laws and dimensional analysis are used to define propagation regimes and non-linear hydro-mechanical coupling is accounted for in the near-tip region. We also quantify the growth of the fracture radius using linear elastic fracture growth model ( R E ) and tip asymptotic solutions ( R V and R T ). A comparison of the three analytical models with published experimental data reveal that (i) the asymptotic solutions are limited to linearly elastic and homogeneous materials, i.e., PMMA (ii) the performance of the linear elastic model ( R E ) poorly matches the experimental data, especially for unstable propagation situations (iii) the new R d model takes advantage of a robust reconstruction of the temporal radius growth of hydraulic fracture problems under realistic stress conditions, and including multiscale propagation regimes, cohesive effects, as well as stable and unstable propagation regimes of geomaterials.
Publisher: Elsevier BV
Date: 04-2022
Publisher: Elsevier BV
Date: 04-2021
Publisher: Wiley
Date: 28-08-2021
DOI: 10.1002/GHG.2118
Abstract: Understanding wettability of clay minerals is crucial in assessing primary migration of hydrocarbon and evaluating CO 2 storage capacities and containment security. In spite of recent efforts, there is considerable uncertainty of experimental data and theoretical predictions are lacking. We, therefore, developed new correlations to predict the advancing and receding contact angles of three different clay minerals (i.e., montmorillonite, Illite and kaolinite) as a function of gas density. To do so, we first measured clay minerals advancing and receding contact angles for helium, nitrogen, argon and carbon dioxide/brine systems at various pressures (5, 10, 15 and 20 MPa) and a constant temperature of 333 K. The statistical analysis shows that the developed correlations are capable of predicting the contact angles of the three clay minerals with very high accuracy (i.e., R 0.95, for all the newly developed correlations). We thus conclude that the wettability of these clay minerals can be computed from knowledge of the gas densities, using these new empirical correlations. This work has important implications for improving wettability predictions, and thus reducing risks related to subsurface operations, such as CO 2 storage or hydrocarbon recovery. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.
No related grants have been discovered for Runhua Feng.