Laboratory Evaluation of Static and Dynamic Sag in Oil-Based Drilling Fluids

Ofei, Titus Ntow; Kalaga, Dinesh V.; Lund, Bjørnar; Saasen, Arild; Linga, Harald; Sangesland, Sigbjørn; Gyland, Knud Richard; Kawaji, Masahiro

doi:10.2118/199567-pa

Cited by 14 publications

(4 citation statements)

References 24 publications

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“…More advanced methods using rotational rheometers have also been tested [4,16,29,44]. Whereas most authors have attempted to correlate sag to rheological data [24,30,31,39,48], others also investigated the relationship between drilling operating parameters and sag [21,28,35,41,47].…”

Section: Introductionmentioning

confidence: 99%

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Rheology assessment and barite sag in a typical North Sea oil-based drilling fluid at HPHT conditions

Ofei

N’gouamba

Opedal

et al. 2023

Korea-Aust. Rheol. J.

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The occurrence of barite sag in drilling fluids has relatively often been the cause for gas kicks in oilwell drilling. The subsequent absorption of gas into drilling fluid could lower the density and reduce the viscosity of the drilling fluid, thereby aggravating both pressure control and hole cleaning. In this paper, we present experimental measurements of rheological properties and barite sag in a typical North Sea oil-based drilling fluid at downhole pressure and temperature conditions. A new experimental apparatus was setup for barite sag measurements at static condition with operational temperature and pressure capabilities up to 200 °C (392°F) and 1000 bar (14,503.8 psi), respectively. Rheometry measurements were conducted on fluid samples with and without barite particles at operating conditions up to 90 °C and 100 bar. We observed that at a typical shear rate of 250 s−1, which is experienced in 8.5″ hole annulus, the viscosity of fluid sample with barite increased nearly three times as that of the fluid sample without barite as the temperature and pressure increased. However, temperature effect on viscosity dominates at high shear rates compared to pressure effect. Furthermore, the fluid samples showed more shear-thinning effect with increasing yield stress as the temperature increased. On the other hand, barite sag measurements revealed that whereas fluid samples under high pressure are less prone to sag, high temperature fluid samples, however, promote sag significantly. The data from this study are useful to validate extrapolations used in computational models and to improve understanding and operational safety of sag phenomena at downhole conditions. We also discuss the importance of this study in optimizing drilling operations.

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Section: Introductionmentioning

confidence: 99%

“…Drilling fluids are commonly formulated and analyzed according to the American Petroleum Institute (API) standards and at elevated temperatures [31]. A few studies have investigated the effect of elevated downhole temperature or pressure on the rheological properties and barite sag in drilling fluids.…”

Section: Introductionmentioning

confidence: 99%

Rheology assessment and barite sag in a typical North Sea oil-based drilling fluid at HPHT conditions

Ofei

N’gouamba

Opedal

et al. 2023

Korea-Aust. Rheol. J.

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“…Many studies are available to determine the viscous parameters of HFFs via steady shear measurements; however, little information is available on the elastic behavior of the fluids during rheological characterization. Conventional viscometric readings commonly used for rheology characterization using viscometers are only reliable for reproducing the flow parameters of Newtonian and pseudoplastic fluids but insufficient to determine the fluid’s viscoelastic properties such as the storage modulus, loss modulus, and dynamic and complex viscosity. − The storage modulus ( G ′) measures the energy stored when the fluid begins to flow, while the loss modulus ( G ″) measures the energy lost or dissipated upon shear deformation. The use of suitable and more efficient rheological instruments to characterize the properties of a fracturing fluid (storage modulus, loss modulus, and phase angle) is a needed prerequisite to accurately determine the potentials of the WBFs.…”

Section: Introductionmentioning

confidence: 99%

Rheological and Viscoelastic Property Characterizations of Amino Acid-Based Hydraulic Fracturing Fluids

2022

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In this paper, we present the results of the rheometric properties of a guar-based fracturing fluid containing amino-acid clay stabilizers. Four amino acids, glycine, proline, alanine, and arginine were selected for the study. KCl, a conventional clay stabilizer, was also used for comparison. The fracturing fluid was prepared using tap water (97.3 wt %), guar gum (0.4 wt %), ethylene glycol (0.1 wt %), potassium carbonate (0.2 wt %), and a clay stabilizer (2 wt %). A Discovery Hybrid rheometer with a bob-in-cup measuring system was used to determine the fluids’ viscoelastic and temperature-dependent properties under both static and dynamic oscillatory conditions. The static tests were employed at varying shear rates of 0.001–1000 s–1 from 25 to 90 °C, mimicking both room and reservoir conditions. For the oscillatory measurements, amplitude and frequency sweep tests were done at a strain ranging from 0.001 to 100% and a frequency ranging from 0.01 to 100 rad/s. The rheological characterizations of the fracturing fluids confirmed that amino acids did not negatively affect the base fluid’s viscoelasticity, flow behavior, shear-thinning properties, and pumpability, including its damping factor. Glycine and alanine enhanced the shear-thinning property of the base fluid by 4 and 5%, respectively. All the stabilized fluids displayed significant upsurges in their elasticity as the frequency was increased from 0.01 to 100 rad/s. Proline, glycine, and alanine improved the base fluid elasticity by reducing its damping factor value by 0.37, 0.20, and 0.14, respectively. Alanine on the other hand increased the base fluid’s damping factor value by 0.12. This study provides new insights into the rheological abilities of hydraulic fracturing fluids containing amino acid additives and how their presence in the fracturing fluid contributes to the effective transportation and dropping of proppants. These insights are necessary for evaluating the effects of additives on the fracturing fluid gel structure, proppant carrying and packing capacity, gelling time, temperature stability, and, more importantly, its structural stability.

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“…As density of the heavy minerals is much higher than the fluid density, gravitational force acts on these particles making them segregate and finally settle out of the fluid. A review of the phenomenon, better known as weighting material sag, and possible measurement methods is found by consulting Ofei et al [1]. The sagging effect occurs both in water-based and oil-based drilling fluids.…”

Section: Introductionmentioning

confidence: 99%

Gel Pills for Downhole Pressure Control during Oil and Gas Well Drilling

et al. 2020

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During drilling of petroleum or geothermal wells, unforeseen circumstances occasionally happen that require suspension of the operation. When the drilling fluid is left in a static condition, solid material like barite may settle out of the fluid. Consequently, the induced hydrostatic pressure that the fluid exerts onto the formation will be reduced, possibly leading to collapse of the borehole or influx of liquid or gas. A possible mitigation action is placement of a gel pill. This gel pill should preferably be able to let settled barite rest on top of it and still transmit the hydrostatic pressure to the well bottom. A bentonite-based gel pill is developed, preventing flow of higher density drilling fluid placed above it to bypass the gel pill. Its rheological behavior was characterized prior to functional testing. The designed gel pill develops sufficient gel structure to accommodate the settled barite. The performance of the gel was tested at vertical and 40° inclination from vertical. Both conventional settling and the Boycott effect were observed. The gel pill provided its intended functionality while barite was settling out of the drilling fluid on top of this gel pill. The barite was then resting on top of the gel pill. It is demonstrated that a purely viscous pill should not be used for separating a high density fluid from a lighter fluid underneath. However, a bentonite or laponite gel pill can be placed into a well for temporary prevention of such intermixing.

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Laboratory Evaluation of Static and Dynamic Sag in Oil-Based Drilling Fluids

Cited by 14 publications

References 24 publications

Rheology assessment and barite sag in a typical North Sea oil-based drilling fluid at HPHT conditions

Rheology assessment and barite sag in a typical North Sea oil-based drilling fluid at HPHT conditions

Rheological and Viscoelastic Property Characterizations of Amino Acid-Based Hydraulic Fracturing Fluids

Gel Pills for Downhole Pressure Control during Oil and Gas Well Drilling

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