Fracturing in the Oil-Sands Reservoirs

Yuan, Yanguang; Yang, B.; Xu, Bin

doi:10.2118/149308-ms

Cited by 15 publications

(13 citation statements)

References 8 publications

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“…The sand grains are about 160 lm in diameter on average and unrestricted by each other, i.e., they are not directly in contact, resulting in a loose and unconsolidated microstructure. The Alberta oil sand has a reported dilation angle of 48° (Samieh 1995;Yuan et al 2011b), while that of the most common Karamay oil sand is only 25°(derived from the triaxial data of the regular oil sand in this study). Currently, the understanding and prediction of the injection-induced dilation remain unclear for the Karamay oil sand and therefore impede the progress of the field fracturing work.…”

Section: Introductionmentioning

confidence: 69%

“…8) over the zone and worm-like tensile microcracks at the borehole wall (Kry et al 1992). Note that the tensile microcracks described by Kry et al (1992) were from repeated image logs on a fractured wall (Yuan et al 2011b). The visual characteristics of tensile microcracks are unavailable in this study due to limitations of the SEM tests in the stress control of the specimens.…”

Section: Regular Oil Sandmentioning

confidence: 99%

“…The dense Alberta oil sand has been simulated as such a material in the literature (e.g., Yale et al 2010;Yuan et al 2011b), mostly based on the linear Drucker-Prager model. Using this model, the tensile parting causes the oil sand to expand elastically at the locations close to the wellbore.…”

Section: Implications For the Field And Simulation Workmentioning

confidence: 99%

“…In this regard, the term ''hydraulic fracturing'' is more appropriately described as ''water injection'' for the case concerned. The dilated zone is created by (1) shear dilation-rolling of sand grains over each other when sheared and (2) tensile parting-when the increased injection pressure reduces the effective stresses at the locations close to the wellbore and creates tensile microcracks (Yuan et al 2011b). Consequently, the effective water mobility of the stimulated zone (mostly by shear dilation) is substantially increased.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the influence of stress path on the dilation in triaxial shear over a range of mean effective stresses was discovered to be negligible. Provided the mechanical parameters determined from the aforementioned studies, other researchers (e.g., Settari and Walters 2001;Yuan et al 2011b) used the Drucker-Prager model to simulate the deformation of the Alberta oil sand reservoirs due to shear dilation.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation on Dilation Mechanisms of Land-Facies Karamay Oil Sand Reservoirs under Water Injection

et al. 2015

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The success of steam-assisted gravity drainage (SAGD) is strongly dependent on the formation of a homogeneous and highly permeable zone in the land-facies Karamay oil sand reservoirs. To accomplish this, hydraulic fracturing is applied through controlled water injection to a pair of horizontal wells to create a dilation zone between the dual wells. The mechanical response of the reservoirs during this injection process, however, has remained unclear for the land-facies oil sand that has a loosely packed structure. This research conducted triaxial, permeability and scanning electron microscopy (SEM) tests on the field-collected oil sand samples. The tests evaluated the influences of the field temperature, confining stress and injection pressure on the dilation mechanisms as shear dilation and tensile parting during injection. To account for petrophysical heterogeneity, five reservoir rocks including regular oil sand, mud-rich oil sand, bitumen-rich oil sand, mudstone and sandstone were investigated. It was found that the permeability evolution in the oil sand samples subjected to shear dilation closely followed the porosity and microcrack evolutions in the shear bands. In contrast, the mudstone and sandstone samples developed distinct shear planes, which formed preferred permeation paths. Tensile parting expanded the pore space and increased the permeability of all the samples in various degrees. Based on this analysis, it is concluded that the range of injection propagation in the pay zone determines the overall quality of hydraulic fracturing, while the injection pressure must be carefully controlled. A region in a reservoir has little dilation upon injection if it remains unsaturated. Moreover, a cooling of the injected water can strengthen the dilation potential of a reservoir. Finally, it is suggested that the numerical modeling of water injection in the Karamay oil sand reservoirs must take into account the volumetric plastic strain in hydrostatic loading.

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Section: Introductionmentioning

confidence: 69%

Section: Regular Oil Sandmentioning

confidence: 99%

Section: Implications For the Field And Simulation Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation on Dilation Mechanisms of Land-Facies Karamay Oil Sand Reservoirs under Water Injection

et al. 2015

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Hydraulic Connection Model in Squeeze Preprocessing SAGD Start-Up

Zhang¹,

Wang²,

Chen³

et al. 2018

Springer Series in Geomechanics and Geoengineering

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Porothermoelastic response of an oil sand formation subjected to injection and micro-fracturing in horizontal wells

et al. 2020

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Stimulation of unconsolidated formations via horizontal wells has seen its vast implementation in the recent development of heavy oil reservoir to save the time and cost of preheating the reservoir before the steam-assisted gravity drainage (SAGD) process. A mathematical approach was proposed in this research that fully couples the hydraulic, mechanical and thermal responses of unconsolidated sandstone formations and also applies failure criteria for describing either shear dilation or tensile parting mechanism that generates microcracks. The approach was implemented to predict the porothermoelastic response of a pair of SAGD wells subject to injection and subsequent micro-fracturing using hot water. It was found that the predicted bottom hole pressures (BHPs) match closely with the field observed data. An elliptical dilation zone developed around the dual wells with relatively high pore pressure, porosity, permeability and temperature, implying good interwell hydraulic communication between both wells. The activation of microcracks dramatically accelerated the dissipation of pore pressure across the entire formation depth and also facilitated heat convection in between the dual wells, though to a lesser extent. In summary, the approach provides a convenient means to assist field engineers in the optimization of injection efficiency and evaluation of interference among multiple horizontal wells.

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Fracturing in the Oil-Sands Reservoirs

Cited by 15 publications

References 8 publications

Experimental Investigation on Dilation Mechanisms of Land-Facies Karamay Oil Sand Reservoirs under Water Injection

Experimental Investigation on Dilation Mechanisms of Land-Facies Karamay Oil Sand Reservoirs under Water Injection

Hydraulic Connection Model in Squeeze Preprocessing SAGD Start-Up

Porothermoelastic response of an oil sand formation subjected to injection and micro-fracturing in horizontal wells

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