Analysis of wellbore stability considering the effects of bedding planes and anisotropic seepage during drilling horizontal wells in the laminated formation

Zhou, Jianting; He, Shiming; Tang, Ming; Huang, Zhen; Chen, Yulin; Chen, Jun; Zhu, Yu; Pan, Yuan

doi:10.1016/j.petrol.2018.06.052

Cited by 44 publications

(17 citation statements)

References 33 publications

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“…Characterizations of BP Realization. It is believed that the characterizations of BPs play a critical role on the response of stratification shale reservoirs to fluid injection [14,15]. The explicit representation of BPs with realistic characterizations is thus important in the numerical modeling.…”

Section: Simulation Models Of Hydraulic Fracturingmentioning

confidence: 99%

“…35 MPa was obtained using the Mohr-Coulomb criterion based on the data obtained from the direct shear experiment in the literature [47]. Then, we can obtain the microscopic mean values of strength f micro (input value of numerical calculation) using equation (15), which are 200.18 MPa and 201.66 MPa, respectively. In order to facilitate the calculation, a value of 200 MPa was used during the calculation and analysis of the model.…”

Section: Geofluidsmentioning

confidence: 99%

“…Chenevert and Mclamore [8][9][10] reported that the compressive strength of layered rock such as shale was a function of the confining pressure and the orientation of the anisotropic plane (BP or cleavage plane). Large quantities of NFs and BPs may change the initiation, propagation, and geometry of HF in a completely different way from those in isotropic and homogeneous media [11][12][13][14][15][16]. NFs and BPs may cause hydraulic fractures to extend along or through the structure surfaces [11,17,18].…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Bedding Planes and Permeability Coefficient on Fracture Propagation of Horizontal Wells in Stratification Shale Reservoirs

et al. 2020

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The complexity of hydraulic fractures (HF) significantly affects the success of reservoir reconstruction. The existence of a bedding plane (BP) in shale impacts the extension of a fracture. For shale reservoirs, in order to investigate the interaction mechanisms of HF and BPs under the action of coupled stress-flow, we simulate the processes of hydraulic fracturing under different conditions, such as the stress difference, permeability coefficients, BP angles, BP spacing, and BP mechanical properties using the rock failure process analysis code (RFPA2D-Flow). Simulation results showed that HF spread outward around the borehole, while the permeability coefficient is uniformly distributed at the model without a BP or stress difference. The HF of the formation without a BP presented a pinnate distribution pattern, and the main direction of the extension is affected by both the ground stress and the permeability coefficient. When there is no stress difference in the model, the fracture extends along the direction of the larger permeability coefficient. In this study, the in situ stress has a greater influence on the extension direction of the main fracture when using the model with stress differences of 6 MPa. As the BP angle increases, the propagation of fractures gradually deviates from the BP direction. The initiation pressure and total breakdown pressure of the models at low permeability coefficients are higher than those under high permeability coefficients. In addition, the initiation pressure and total breakdown pressure of the models are also different. The larger the BP spacing, the higher the compressive strength of the BP, and a larger reduction ratio (the ratio of the strength parameters of the BP to the strength parameters of the matrix) leads to a smaller impact of the BP on fracture initiation and propagation. The elastic modulus has no effect on the failure mode of the model. When HF make contact with the BP, they tend to extend along the BP. Under the same in situ stress condition, the presence of a BP makes the morphology of HF more complex during the process of propagation, which makes it easier to achieve the purpose of stimulated reservoir volume (SRV) fracturing and increased production.

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Section: Simulation Models Of Hydraulic Fracturingmentioning

confidence: 99%

Section: Geofluidsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Influence of Bedding Planes and Permeability Coefficient on Fracture Propagation of Horizontal Wells in Stratification Shale Reservoirs

et al. 2020

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“…Wellbore engineers combine a constitutive stress equation, which shows the stress distributions around the wellbore, with an accurate rock failure criterion to determine successfully the critical mud weight (Chen et al 2015; Gholami et al 2013;Martemyanov et al 2017;Zhou et al 2018). The rock failure criterion states the condition of principal stresses at the point when rocks fail.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Collapse Gradient of Deep Water Horizontal Wellbore and the Effects of Mud Chemical Activity and Variation in Water Depth

Dosunmu

Nwonodi

Ekeinde

2020

Studia Geotechnica Et Mechanica

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Wellbore collapse is an instability-event that occurs at low mud density and leads to unfavorable economic project, reaching billions of US dollars. Thus, it is important to accurately determine its value, especially in deepwater horizontal wellbores. The main reasons for nontrivial problems with such wellbores are evident: the shale encountered are anisotropic in nature and possess planes of weakness; they react with water-based mud, generate osmotic stresses, swell, and fall unto the wellbore bottom, thereby increasing the non-productive time. To this end, salts are added to reduce the collapse tendency, but it is not currently known what amount of salt addition maintains stability, and does not lead to wellbore fracture; in deepwater, the current trend in global warming means there is a future concern to the industry. As the climate temperature increases, more ice melts from the polar region, the seawater expands and the sea level rises. How to incorporate the corresponding effect on collapse gradient is scarcely known. This study captures the major concerns stated above into wellbore stability analysis. Following the classical approach for geomechanical analysis, Mogi-Coulomb criterion was combined with a constitutive stress equation comprising contributions from mechanical and osmotic potentials of mud and shale. A sophisticated industry model was used to consider the deepwater effect. The results show significant reduction in collapse gradient as the water depth increases, also, larger difference between the mud and shale chemical activities represents higher complexities in the wellbore. In addition, the reduction in the chemical activities of mud limited to 37.5% of the initial value can be practically safe.

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“…Thus, the evolution and effectiveness of fracture networks are related to the changing stress ratio [29,41]. However, most of these studies focused on the hydraulic fracturing and the impact of stress ratio on nitrogen fracturing has not been well studied.Furthermore, anisotropy is one of the most distinctive characteristics of the shale due to the existence of bedding planes [42,43]. Compared to the shale matrix, the bedding plane has weak cementing force and high compressibility, which affects the mechanical deformation, fracture parameters, failure strength, and fracture behavior in bedding shales [21,27,39,40,[44][45][46].…”

mentioning

confidence: 99%

Numerical Study of Fracture Network Evolution during Nitrogen Fracturing Processes in Shale Reservoirs

et al. 2018

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This paper develops a numerical model to study fracture network evolution during the nitrogen fracturing process in shale reservoirs. This model considers the differences of incompressible and compressible fluids, shear and tensile failure modes, shale heterogeneity, and the strength and permeability of both shale matrix and bedding planes through the coupling of mechanical-seepage-damage during fracturing fluid injection. The results show that nitrogen fracturing has a lower breakdown pressure and larger seepage zone than hydraulic fracturing under the same injection pressure. Tensile failure was identified as the major reason for the initiation and propagation of fractures. Ignoring the effect of bedding planes, the fracture initiation pressure, breakdown pressure, and fracturing effectiveness reached their maxima when the stress ratio is 1. Under the same strength ratio, the propagation path of the fractures was controlled by the stronger effect that was casused by the bedding angle and stress ratio. With increasing the strength ratio, the fracture number and shearing of the bedding plane increased significantly and the failure pattern changed from tensile-only mode to tensile-shear mode. These analyses indicated that the fracture network of bedding shale was typically induced by the combined impacts of stress ratio, bedding angle and strength ratio.Energies 2018, 11, 2503 2 of 22 more effective if N 2 is applied for the hydraulic fracturing [22,23]. Different fracturing fluids lead to the different pore pressure distributions during fluid flow due to the various properties such as viscosity and compressibility. According to the principle of effective stress, the difference in pore pressure distribution induces the difference in the stress distribution in rocks, which plays an important role in fracturing behavior during the fracturing process [24][25][26][27]. Lower breakdown pressure, larger seepage zone and more complex fracture network were observed during nitrogen fracturing [24][25][26][27]. However, these studies were performed on simple rock samples and the influence of other factors during nitrogen fracturing has not been well evaluated. It is essential to investigate fracture network evolution during the nitrogen fracturing process.Several numerical models have been developed to investigate fracture behaviors during the hydraulic fracturing process. These models include the boundary element method [28], finite element method [29][30][31], and discrete element method [32,33]. Wang et al. [29] applied a new mathematical model to investigate fracture network evolution of multi-stranded fractures with pre-existing natural fractures. Shalev and Lyakhovsky [31] studied the damage evolution and seismicity phenomenon in hydraulic fracturing using an improved damage model based on the finite element method. However, there are still only a few studies on a numerical model for nitrogen fracturing and the comparison between water fracturing and nitrogen fracturing. On the other hand, shale reservoirs occur at di...

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Analysis of wellbore stability considering the effects of bedding planes and anisotropic seepage during drilling horizontal wells in the laminated formation

Cited by 44 publications

References 33 publications

The Influence of Bedding Planes and Permeability Coefficient on Fracture Propagation of Horizontal Wells in Stratification Shale Reservoirs

The Influence of Bedding Planes and Permeability Coefficient on Fracture Propagation of Horizontal Wells in Stratification Shale Reservoirs

Analysis of the Collapse Gradient of Deep Water Horizontal Wellbore and the Effects of Mud Chemical Activity and Variation in Water Depth

Numerical Study of Fracture Network Evolution during Nitrogen Fracturing Processes in Shale Reservoirs

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