Analysis of the vertical borehole stability in anisotropic rock formations

Jin, Yan; Yuan, Jianbo; Hou, Bin; Chen, Mian; Lu, Yunhu; Li, Song; Zou, Zhipeng

doi:10.1007/s13202-012-0033-y

Cited by 14 publications

(5 citation statements)

References 6 publications

(5 reference statements)

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“…() and Amadei ()) and the initiation and growth of hydraulic fractures (e.g., Aghighi and Rahman (); Vahid and Ahmad (); and Waters, Lewis, and Bentley ()); to predicting the stability of boreholes drilled through such formations (e.g., Jin et al . (); Jia et al . (); Ong and Roegiers (); Gaede et al .…”

Section: Introductionmentioning

confidence: 99%

Static and dynamic pressure sensitivity anisotropy of a calcareous shale

Ong

Schmitt

Kofman

et al. 2016

Geophysical Prospecting

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Optimizing the productivity of nonconventional, low‐permeability “shale” reservoirs requires detailed knowledge of the mechanical properties of such materials. These rocks' elastic anisotropy is acknowledged but usually ignored due to difficulties in obtaining such information. Here we study in detail the dynamic and static elastic properties of a suite of calcareous mudstones from the nonconventional Duvernay reservoir of Alberta, Canada. The complete set of transversely isotropic elastic constants is obtained from strategically oriented ultrasonic transducers to confining pressures of 90 MPa. Wave speed anisotropies of up to 35% are observed at even the highest confining pressures. Furthermore, the stress sensitivity of the wave speeds, and hence moduli, is itself highly dependent on direction with speeds taken perpendicular to the bedding plane being highly nonlinearly dependent on pressure, whereas those along the bedding plane show, unexpectedly, nearly no pressure dependence. These observations are in qualitative agreement with the preferentially oriented porosity and minerals seen in scanning electron microscope images. These results may be significant to the interpretation of sonic logs and azimuthal amplitude versus offset for principal stress directions, for the concentration of stress within such formations, and for estimation of static engineering moduli from sonic log wave speeds.

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Section: Introductionmentioning

confidence: 99%

Static and dynamic pressure sensitivity anisotropy of a calcareous shale

Ong

Schmitt

Kofman

et al. 2016

Geophysical Prospecting

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“…The stress distribution around wellbore also can be expressed by in situ stresses (σ H , maximum horizontal stress; σ h , minimum horizontal stress; σ v , vertical stress) through a number of coordinate transformations. The detailed transformations can be found in previous studies [36,37].…”

Section: Methods Of Determining Correlation Between Drilling Fluid De...mentioning

confidence: 99%

A Quantitative Evaluation Method of Anti-Sloughing Drilling Fluid Inhibition for Deep Mudstone

Jin

et al. 2022

Energies

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Wellbore instability resulting from deep mudstone hydration severely restricts the development of oil and gas resources from deep reservoir in western China. Accurate evaluation of drilling fluid inhibition properties plays an important role in selecting drilling fluid that can control deep mudstone hydration and then sustain wellbore stability. The previous evaluations are conducted by qualitative analysis and cannot consider the influence of complex hydration conditions of deep mudstone (high temperature, high pressure and flushing action). The study proposes a quantitative method to evaluate drilling fluid’s inhibition property for deep mudstone under natural drilling conditions. In this method, the cohesive strength of mudstone after hydration is adopted as the inhibition index of the tested drilling fluid. An experimental platform containing a newly designed HPHT (High pressure and high temperature) hydration experiment apparatus and mechanics characterization of mudstone after hydration based on scratch test is proposed to obtain the current inhibition index of tested drilling fluid under deep well drilling environments. Based on the mechanical–chemical wellbore stability model considering strength weakening characteristics of deep mudstone after hydration, a cross-correlation between drilling fluid density (collapse pressure) and required inhibition index (cohesive strength) for deep mudstone is provided as the quantitative evaluation criterion. Once the density of tested mud is known, one can confirm whether the inhibition property of tested mud is sufficient. In this study, the JDK mudstone of a K block in western China is selected as the application object of the proposed evaluation method. Firstly, the evaluation chart, which can demonstrate the required inhibition indexes of the tested fluids quantitatively with various densities for JDK mudstone, is constructed. Furthermore, the experimental evaluations of inhibition indexes of drilling fluids taken from two wells in K block are conducted under ambient and deep-well drilling conditions, respectively. In order to show the validity and advantage of the proposed method, a comparison between the laboratory evaluation results and field data is made. Results show that the laboratory evaluation results under deep-well drilling conditions are consistent with the field data. However, the evaluation under ambient conditions overestimates the inhibition property of the tested fluid and brings a risk of wellbore instability. The developed quantitative method can be a new way to evaluate and optimize the inhibition property of drilling fluid for deep mudstone.

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“…When combined with the analysis of the elastic modulus data of the Longmaxi shale derived from triaxial compression experiments [47], the maximum degree of anisotropy on the elastic modulus becomes approximately 1.25. It is known that anisotropic elasticity behavior has a relatively small impact on the stress distribution, especially when the degree of anisotropy is low (<1.25) [48,49]. The model used in this paper is a 2D model.…”

Section: Geofluidsmentioning

confidence: 99%

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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Analysis of the vertical borehole stability in anisotropic rock formations

Cited by 14 publications

References 6 publications

Static and dynamic pressure sensitivity anisotropy of a calcareous shale

Static and dynamic pressure sensitivity anisotropy of a calcareous shale

A Quantitative Evaluation Method of Anti-Sloughing Drilling Fluid Inhibition for Deep Mudstone

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

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