The Importance of Extended Leak-Off Test Data for Combatting Lost Circulation

Okland, D.; Gabrielsen, Glenn; Gjerde, Jørn; Sinke, Koen; Williams, Ernest H.

doi:10.2523/78219-ms

Cited by 7 publications

(5 citation statements)

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“…Furthermore, the leak-off test only recorded pressures for 3 min after the pumps were switched off, and it is impossible to reliably measure FCP in such a brief period. Indeed, the 16.4 ppg (19.27 MPa/km) pressure reported by Sawolo et al (2009) as 'fracture closure pressure' most likely represents the fracture propagation pressure (FPP) and is not a value used to estimate formation strength by any industry standards (Jørgensen and Fejerskov, 1998;Økland et al, 2002;Raaen et al, 2006;van Oort and Vargo, 2008).…”

Section: What Pressure Could the Well Tolerate?mentioning

confidence: 97%

“…In determining the leak-off pressure (LOP), industry accepted practice is to take the inflexion point on a pressure build-up curve (Bell, 1996;Enever et al, 1996;Addis et al, 1998;Jørgensen and Fejerskov, 1998;Økland et al, 2002;Raaen et al, 2006;van Oort and Vargo, 2008). Based upon the pressure versus time plot (their figure 11), using this method the leak off was 15.8 ppg (18.57 MPa/km).…”

Section: What Pressure Could the Well Tolerate?mentioning

confidence: 99%

See 1 more Smart Citation

Sawolo et al. (2009) the Lusi mud volcano controversy: Was it caused by drilling?

Davies

Manga

Tingay

et al. 2010

Marine and Petroleum Geology

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Section: What Pressure Could the Well Tolerate?mentioning

confidence: 97%

Section: What Pressure Could the Well Tolerate?mentioning

confidence: 99%

Sawolo et al. (2009) the Lusi mud volcano controversy: Was it caused by drilling?

Davies

Manga

Tingay

et al. 2010

Marine and Petroleum Geology

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“…In the early 1990's, the concept of adding granular particles to drilling mud to seal fractures around the wellbore was presented 8,9 . The basic idea is to increase the fracture gradient by increasing the wellbore hoop stress artificially [10][11][12][13][14][15][16][17][18] . In a depleted formation there is not enough fracture resistance in the weak zones to balance the mud weight.…”

Section: Depletion Induced In-situ Stress Changesmentioning

confidence: 99%

Managing Geomechanics Principles for Proper Handling of Wellbore-Stability Problems in Shale and Depletion Effects on Formations While Drilling

Meng

Fuh

Spencer

2010

SPE Annual Technical Conference and Exhibition

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This paper describes two types of hole problems and wellbore stability solutions for drilling operations in North Sea fields: (1) severe shale cavings and wellbore collapse; (2) drilling through cap rock and reservoir formations impacted by large pressure depletion and reservoir compaction effects.Field cases of wellbore collapses and failures in shale formations during high-angle drilling are presented along with a systematic program of comprehensive geomechanics investigation and evaluation necessary to prevent such events. The program includes analyzing drilling and log data analysis for rock strength and earth stress model construction, laboratory triaxial stress-strain tests on well core samples considering bedding plane inclination effects, 3D analytical modeling and 3D elastic-plastic numerical modeling analysis for determining optimum mud-weight (MW) windows for secure and stable well drilling.Continuous well production can also present problems for in-field drilling as the severe pressure depletion and reservoir compaction will cause significant reduction in stresses and formation fracture gradient. These effects may occur not only in the reservoir, but may also extend significantly upward into the cap rock formations depending on the reservoir/formation stiffness contrast, reservoir size, thickness and depth, etc. Therefore, the optimum MW must be examined and recalculated based on the insitu stresses that can be altered by this effect. In summary, this paper will include the following:1. Analysis of actual drilling cases of severe shale caving and wellbore collapses/failures; 2. Laboratory triaxial stress-strain tests on well cores considering bedding plane effects; 3. Effective drilling guidelines based on modeling analysis of troublesome shale formations; 4. Coping with reduced stresses and formation fracture gradient due to reservoir depletion and compaction effects; 5. Use of wellbore strengthening material for drilling (and possible reduction in number of casing strings); 6. Case histories of severe wellbore instability and lessons learned. IntroductionWellbore stability is affected by many issues, such as the in-situ stresses, pore pressure, rock properties, formation strength, mud fluid properties, reservoir depletion, well azimuth and inclination, and drilling operations. Most of the drilling problems have occurred in the overburden, especially in the shale formations. These instabilities which are encountered during exploration through development drilling may be affected by the properties of both shale (in-situ stress, mineralogy, strength) and the drilling fluid-shale interactions (fluid density, salinity, ionic concentration and swelling) 1,2,3 . Micro-fracture, fissures and weak bedding planes will also destabilize shale as drilling fluid penetrates the formations. The penetrated fluid will increase pore pressure, reduce effective stress and reduce shale formation strength. Shale stability should take into account both mechanical instability induced by stress and strength, and complex dril...

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“…It is important that the down hole pressures never exceed the fracturing pressure or enter pressure areas vulnerable for hole instability issues. The accessible pressure window is estimated from geological analyses and is modified by a series of formation strength tests [1] as the drilling proceeds.…”

Section: Introductionmentioning

confidence: 99%

Annular Frictional Pressure Losses for Drilling Fluids

Saasen¹,

Ytrehus²

2021

Preprint

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In the paper, it is demonstrated how a Herschel-Bulkley fluid model, where the parameters are selected from relevant shear rate range of the flow and are parametrically independent, can be used for pressure loss calculations. The model is found to provide adequate pressure loss predictions for axial flow in an annulus where the inner cylinder does not rotate. It is described how one can simplify a slot model approximation of the annulus pressure loss using the Herschel-Bulkley fluid model (Founargiotakis model). This simplified model gives approximately the same accuracy as does the full Founargiotakis model. It is shown that the use of such a parallel plate model gives reasonably good fit to measured data on laminar flow of oil-based drilling fluids if the viscous data are measured at relevant shear rates for the flow. Laboratory measurements indicate that the use of the simplified pressure loss model is also valid for turbulent flow. However, the predictions should be adjusted for the surface roughness in the well.

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The Importance of Extended Leak-Off Test Data for Combatting Lost Circulation

Cited by 7 publications

References 0 publications

Sawolo et al. (2009) the Lusi mud volcano controversy: Was it caused by drilling?

Sawolo et al. (2009) the Lusi mud volcano controversy: Was it caused by drilling?

Managing Geomechanics Principles for Proper Handling of Wellbore-Stability Problems in Shale and Depletion Effects on Formations While Drilling

Annular Frictional Pressure Losses for Drilling Fluids

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