A Study of Horizontal-Wellbore Failure

Hsiao, Chi-Mei

doi:10.2118/16927-pa

Cited by 22 publications

(10 citation statements)

References 3 publications

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“…The presence of steps not only contributes to the abnormally high fracture-propagation pressure, but also may lead to a premature sandout. The analysis performed by Hsiao (1988) confirmed Daneshy's results, where shear stress plays an important role in the stability of horizontal wells that are at an angle to the direction of minimum stress.…”

Section: Reorientation Of Fractures and Reorientation Radiussupporting

confidence: 77%

“…the formation of "steps" because of shear failure. Soliman and Boonen (Hsiao 1988) presented a fairly comprehensive review of the rock-mechanics aspects of horizontal wells, both stimulated and unstimulated. Owens et al (1992) presented another approach for calculating the breakdown pressure of an arbitrarily oriented horizontal well.…”

Section: Fracturing Failure Criteria For Transverse Fracturesmentioning

confidence: 99%

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Geomechanics Aspects of Multiple Fracturing of Horizontal and Vertical Wells

Soliman

East

Adams

2008

SPE Drilling &Amp; Completion

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Summary Although unstimulated horizontal wells have been successful in naturally fractured reservoirs and in reservoirs with gas- or water-coning problems, fracturing a horizontal well may be a viable option in certain situations. Because of the dependence of fracture orientation on well direction with respect to the stress field, the possibility of fracturing a horizontal well must be considered before the well is drilled. The appropriate contingency plans should be made to anticipate the possible low production from an unstimulated well. It should be remembered that fracturing a horizontal well may also dictate how the wellbore may be completed or oriented. Fracturing a horizontal well may take place in one of the following situations:Restricted vertical flow caused by low vertical permeability or the presence of shale streaks.Low formation productivity because of low formation permeability.The presence of natural fractures in a direction different from that of induced fractures. Thus, induced fractures have a high chance of intercepting the natural fractures.Low stress contrast between the pay zone and the surrounding layers. In this case, a large fracturing treatment of a vertical well would not be an acceptable option because the fracture would grow in height as well as length. Drilling a horizontal well and creating either several transverse or longitudinal fractures would allow rapid depletion of the reservoir through the fractures. Although fundamentally similar to fracturing vertical wells, fracturing horizontal wells has its unique aspects that require special attention to secure successful treatment. Differences between horizontal and vertical wells exist in areas of rock mechanics, reservoir engineering, and operational aspects. To start with, the basic rock-mechanics aspects are examined.

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Section: Reorientation Of Fractures and Reorientation Radiussupporting

confidence: 77%

Section: Fracturing Failure Criteria For Transverse Fracturesmentioning

confidence: 99%

Geomechanics Aspects of Multiple Fracturing of Horizontal and Vertical Wells

Soliman

East

Adams

2008

SPE Drilling &Amp; Completion

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“…Therefore a fracture will initiate at the top and bottom of the wellbore. 5 This is confirmed by the image logs, which show drilling induced fractures (breakout occurs90 degrees from the induced fractures and is associated with high stresses and underballanced drilling) at both the top and bottom of the hole. The optimal perforation design for this stress scenario would be to orient 0 o /180 o phasing to preferentially align the perforations with the preferred fracture plane.…”

Section: Perforationsmentioning

confidence: 52%

A Field Study Optimizing Completion Strategies for Fracture Initiation in Barnett Shale Horizontal Wells

Ketter

Daniels

Heinze

et al. 2006

SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Barnett shale is an unconventional gas reservoir that is currently estimated to extend over 54,000 square miles. In an effort to improve well economics and to reduce the number of surface locations in populated areas, there has been a rapid increase in the number of horizontal wells being drilled and completed. With this change in development strategy, operators and service companies alike have had to search for innovative solutions to overcome challenges faced in horizontal completions.Inefficient fracture initiation is the largest reoccurring problem seen when completing horizontal Barnett shale wells. These difficulties are manifested as high fracture initiation and propagation pressures, which lead to low injection rates and high treating pressures. These losses reduce the efficiency of proppant placement and stimulation. As drilling activity has increased over the past couple of years, fracture initiation problems have represented a substantial source of expense and downtime.This field study examines 256 horizontal Barnett shale wells in an effort to identify the causes of these near-wellbore issues and to offer corrective solutions for future completions. The goal of this study is to recommend an optimized completion strategy to minimize these near-wellbore problems, increase stimulation coverage and decrease unplanned completion expenses.In 2005, 19% of the stages in horizontal wells examined encountered near-wellbore difficulties. This field study inspects the major contributors to fracture initiation, specifically focusing on cemented versus uncemented laterals, horizontal stress anisotropy, perforation strategy, cementing strategy and stimulation design.The paper offers statistics on which changes have had the greatest effect on stimulation placement. These problems can cost operators upwards of an additional 25% per stage. Using these optimized strategies has reduced the number of stages where fracture initiation difficulties have been encountered by 74%.

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“…They found that these stresses could lead to borehole failure in some cases. Hsiao [1988] used a similar approach and analyzed the influence of poroelasticity for a horizontal well. Detournay and Chang [1988] and Cui [1995] Comparisons with early models are made to show that accounting for water and solute fluxes is important to correctly predict wellbore stability in shales.…”

Section: Literature Reviewmentioning

confidence: 99%

Chemical and Thermal Effects on Wellbore Stability of Shale Formations

Chen

Chenevert

et al. 2001

SPE Annual Technical Conference and Exhibition

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A new three-dimensional wellbore stability model is presented that takes into account thermal stresses and the flux of both water and solutes from drilling fluids (muds) into and out of shale formations. Mechanical stresses around a wellbore placed at any arbitrary orientation in a 3-dimensional stress field are coupled with changes in temperature and pore pressure due to water and solute fluxes. The radial and azimuthal variation in the stress distribution and the "failure index" are computed to check for wellbore failure. This model accounts for the hindered diffusion of solutes as well as the osmotically driven flow of water into the shale. The model for the first time allows a user to study the role of solute properties on wellbore stability. Results from the model show that a maxima or minima in pore pressure can be obtained within a shale. This leads to wellbore failure not always at the wellbore wall as is most commonly assumed but to failure at some distance inside the shale. Since the fluxes of water and solute, and temperature, are time dependent, a clearly time dependent wellbore failure is observed. The time to wellbore failure is shown to be related to the rate of solute and water invasion. Comparisons with experiments conducted with a variety of solutes on different shales show excellent agreement with model results. It is shown in this study that the solutes present in the mud play an important role in determining not only the water activity but also in controlling the alteration of pore pressures in shales. To account for this phenomenon a model is presented to compute the flux of both water and solutes into or out of shales. The relative magnitudes of these fluxes control the changes in pore pressure in the shale when it is exposed to the mud. The effect of the molecular size of the solute, the permeability of the shale and its membrane efficiency are some of the key parameters that are shown to determine the magnitude of the osmotic contribution to pore pressure. A range of behavior is observed if the solute is changed while the water activity is maintained constant. This clearly indicates the importance of the solute flux in controlling the pore pressure in shales. Critical mud weights are obtained by inspecting the stability of the wellbore wall and the entire near wellbore region. Pore pressures at different time and position are investigated and presented to explain the model results. It is shown in this study that the critical mud weights are strongly time dependent. The effects of permeability, membrane efficiency of shale, solute diffusion coefficient, mud activity and temperature changes are presented in this work. The collapse and fracture effects of cooling and heating the formations are also presented. A powerful tool has been developed which can be used to perform thorough investigations of the wellbore stability problem. A user-friendly interface has been developed to ease usage. Introduction Shale instability is a costly problem for the oil and gas industry. Over-gauged boreholes induced by borehole collapse failure, the loss of drilling fluid into the formation due to borehole breakdown failure, and consequent hole cleaning and well control problems are typical occurrences when shales experience failure. These problems are primarily caused by the rock stress exceeding the rock strength as the borehole is drilled.

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A Study of Horizontal-Wellbore Failure

Cited by 22 publications

References 3 publications

Geomechanics Aspects of Multiple Fracturing of Horizontal and Vertical Wells

Geomechanics Aspects of Multiple Fracturing of Horizontal and Vertical Wells

A Field Study Optimizing Completion Strategies for Fracture Initiation in Barnett Shale Horizontal Wells

Chemical and Thermal Effects on Wellbore Stability of Shale Formations

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