Analysis of borehole collapse and fracture initiation positions and drilling trajectory optimization

Wei-dong, Zhang; Gao, Jiajia; Kai, Lan; Liu, Xinhua; Feng, Guangtong; Qingtao, MA

doi:10.1016/j.petrol.2014.08.021

Cited by 40 publications

(8 citation statements)

References 44 publications

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“…However, recent studies have reported present-day normal faulting to strike-slip transitional stress state from the onshore Nile Delta (Leila et al, 2021). Based on the inferred geomechanical parameters, we employed Mohr-Coulomb failure criteria to decipher the shear failure gradient (SF) which denotes the minimum required mud weight for avoiding compressive failures (Zhang, 2013;Zhang et al, 2015):…”

Section: Methodsmentioning

confidence: 99%

Geomechanical assessment of the Lower Turonian AR-F limestone Member, Abu Gharadig Field, Egypt: Implications for unconventional resource development

Farouk

Sen²,

Abu-Alam

et al. 2022

Front. Earth Sci.

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This study evaluates the unconventional reservoir geomechanical characteristics of the Lower Turonian Abu Roash-F (AR-F) carbonates from the Abu Gharadig field, onshore Egypt, which has not been attempted before. The interval dominantly consists of planktic foraminifera and micrite matrix. The AR-F marine carbonate is organic-rich (0.59–3.57 wt% total organic carbon), thermally mature (435–441°C Tmax) and falls within the oil generation window. The studied interval is very tight with up to 2.6% porosity and 0.0016–0.0033 mD permeability with the wireline log-based brittleness index ranging between 0.39–0.72 which indicates a less brittle to brittle nature. AR-F exhibits a hydrostatic pore pressure gradient with minimum horizontal stress (Shmin) varying between 0.66–0.76 PSI/ft. Safe wellbore trajectory analysis was performed for deviated and horizontal wells to infer the mud pressure gradients required to avoid wellbore instabilities. Based on the inferred in-stress magnitudes and considering an NNE regional maximum horizontal stress orientation, none of the fractures are found to be critically stressed at present day. To produce from the AR-F, hydraulic fracturing is necessary, and we infer a minimum pore pressure increment threshold of 1390 PSI by fluid injection to reactivate the vertical fractures parallel to regional minimum horizontal stress azimuth.

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Section: Methodsmentioning

confidence: 99%

Geomechanical assessment of the Lower Turonian AR-F limestone Member, Abu Gharadig Field, Egypt: Implications for unconventional resource development

Farouk

Sen²,

Abu-Alam

et al. 2022

Front. Earth Sci.

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“…According to (19), (20), and (21), the shear stress is 0 in the disc center, and the stresses σ x and σ y are the minimum principal stress σ 3 and the maximum principal stress σ 1 , respectively. By combining (22), the term for experience failure criteria can be expressed as…”

Section: Analysis Of Anisotropic Tensile Strength Of Layered Shalementioning

confidence: 99%

“…Mohr-Coulomb and Hoek-Brown [21] applied the shear failure strength criteria to the borehole stability analysis associated with a homogeneous linear poroelastic model, which ignored the influence of the intermediate principal stress on rock failure. Based on borehole stress solutions, Zhang et al [22] analyzed the influencing factors, such as Poisson's ratio and shear stress, but the solutions were all derived from the homogeneous linear poroelastic theory. Sun et al [23] thought that shear failure, plastic deformation, and the coupling effect near the fracture tip play an important role in the fracture initiation and propagation, and a new coupled model is presented.…”

Section: Introductionmentioning

confidence: 99%

Fracture Initiation Model of Shale Fracturing Based on Effective Stress Theory of Porous Media

Jia

2018

Geofluids

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Unconventional oil and gas are important resources of future energy supply, and shale gas is the focus of the development of unconventional resources. Shale is a special kind rock of porous medium, and an orderly structure of beddings aligned in the horizontal direction where causing the strong elastic anisotropy of shale is easy. A new model has been established to calculate the fracture initiation pressure with the consideration of mechanical characteristics of shale and the anisotropic tensile strength when judging rock failure. The fracture initiation model established in this paper accurately reflects the stress anisotropy and matches well with the actual situation in porous media. Through the sensitivity analysis, the results show that σv/σH, Ev/EH, υv/υH, m/s, and A/B have a certain impact on the tangential stress when the circumferential angle changes, and there is a positive relationship between the initiation pressure and the above sensitive factors except for A/B. The results can provide a valuable and effective guidance for the prediction of fracture initiation pressure and fracture propagation mechanism under special stratum conditions of shale.

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“…A number of engineering studies have been conducted on rock creep deformation, including theoretical, experimental, and numerical methods [14][15][16][17][18][19][20][21]. A borehole stability analysis mainly uses the linear elastic-brittle or porous elastic theory, and when the stress around a borehole violates a particular rock failure criterion, it is assumed that the borehole has collapsed [22][23][24][25]. Based on further research on an analytical method of the creep deformation of circular holes, the rheological constitutive model of surrounding rock underwent the development from a less-viscous viscoelastic model to a more rational visco-elastoplastic model [26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Borehole diameter shrinkage rule considering rheological properties and its effect on gas extraction

2020

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To study the shrinkage rule of borehole diameter and its effect on gas extraction, a viscoelastoplastic model for boreholes considering strain softening and the dilatancy characteristic was established to obtain the expressions of the coal stress, variation in diameter, and pressure relief range. The stress distribution and pressure relief effect of the boreholes in soft and hard coal seams were comparatively analyzed. The shrinkage rule of the borehole diameter was studied. The reasons for the rapid reduction in the extraction concentration of the borehole in soft coal seams were described. A technology of improving the gas extraction effect in soft coal seams was developed. The research results showed that the radius of the plastic softening zone is 0.405 m for a borehole in a soft coal seam and 0.224 m for that in a hard coal seam. This indicates that the borehole in a soft coal seam has a better pressure relief effect. The boreholes in both hard and soft coal seams will incur a shrinkage phenomenon; however, the soft coal seam has low strength and a weak ability to resist damage, and thus the surrounding coal will have a more intense creep deformation, leading to an instability failure during a short period of time and thus, a blocking of the extraction channel, thereby causing a rapid reduction in the gas extraction concentration. The borehole in a hard coal seam also shows a shrinkage phenomenon, but remains in a stable state without a blockage; thus, high-concentration gas can be extracted from this borehole for a long period of time. The geo-stress and coal strength are the two main factors controlling the amplitude of borehole shrinkage. From an increase in stress, the borehole in a hard coal seam shows a more intense creep deformation in a deep mine, which may lead to blockage. The key to improving the gas extraction effect in soft coal seams is to maintain a smooth extraction channel. The full screen pipe is installed through the drill pipe to retain an extraction channel, leading to an average gas extraction increase from 0.043 m 3 /min to 0.12 m 3 / min, an increase of 2.77 times. These research results are consistent with actual production, and can provide theoretical guidance for determining the gas extraction parameters.

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Analysis of borehole collapse and fracture initiation positions and drilling trajectory optimization

Cited by 40 publications

References 44 publications

Geomechanical assessment of the Lower Turonian AR-F limestone Member, Abu Gharadig Field, Egypt: Implications for unconventional resource development

Geomechanical assessment of the Lower Turonian AR-F limestone Member, Abu Gharadig Field, Egypt: Implications for unconventional resource development

Fracture Initiation Model of Shale Fracturing Based on Effective Stress Theory of Porous Media

Borehole diameter shrinkage rule considering rheological properties and its effect on gas extraction

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