The Influence of Drilling Variables on Barite Sag

Bern, P.A.; Zamora, Mario; Slater, Kenneth; Hearn, P.J.

doi:10.2118/36670-ms

Cited by 57 publications

(36 citation statements)

References 12 publications

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“…Hanson et al (2) have investigated the phenomenon and found that most of the sagging occurs while the mud is circulating. The same conclusion was reached by Bern et al, (3) the sagging tendency is highest at low annular velocities. Zamora and Jefferson (4) presented a method for tracking drilling fluid density variations, which helps to detect, but not to predict drilling mud instability.…”

Section: Introductionsupporting

confidence: 83%

“…It was shown by Bern et al (3) that rotation of the drill pipe will counteract barite separation. When the particles are brought to the high side of the borehole through rotational flow they will settle towards the centre of the borehole, i.e., in the opposite direction of the transported particles.…”

Section: Introductionmentioning

confidence: 99%

“…In static, inclined conditions, a gel will develop, but experience shows that separation occurs nevertheless, which indicates that the gel strength cannot be a good indicator for predicting sagging tendencies. Some operators and service companies (3) are basing evaluation of static sagging on the 3 and 6 rpm shear stress readings. The low shear rate yield point is defined by (3) Since the relative error is large at such low shear stress readings, it was decided to apply the plastic viscosity and yield point in our investigations.…”

Section: Introductionmentioning

confidence: 99%

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Barite Segregation In Inclined Boreholes

Skalle

Backe

Lyomov

et al. 1999

Journal of Canadian Petroleum Technology

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Settling and sagging of barite in inclined boreholes may lead to safety and operational problems. To study the effect of rheology on settling, a laboratory tool was designed, consisting of two connected tubes, one inclined and one vertical. The hydrostatic pressure was measured at the bottom of each pipe. Stable and unstable muds can clearly be differentiated through their pressure behaviour. Several muds were studied at simulated static and dynamic conditions. The results show that sagging is most severe during laminar flow and also indicate that the rheological parameters may be used for predicting stability problems. Introduction In weighted drilling mud barite tends to segregate slowly. In directional drilling operations the settling process is accelerated. Barite settles in the lower side of the borehole and starts sliding when the borehole has an inclination above 30 °. This phenomenon is known as barite sagging. Sagging can lead to drilling and completion problems; a density variation or non-linear hydrostatic pressure gradients which can lead to pressure control problems, while thick and tight barite beds can lead to high torque and drag, stuck pipes and plugged boreholes, and even lost circulation. The sag problem is related to the so called Boycott effect(1), first described in 1920. Hanson et al.(2) have investigated the phenomenon and found that most of the sagging occurs while the mud is circulating. The same conclusion was reached by Bern et al.,(3) the sagging tendency is highest at low annular velocities. Zamora and Jefferson(4) presented a method for tracking drilling fluid density variations, which helps to detect, but not to predict drilling mud instability. Jamison and Clements(5) developed a test method to characterise settling and sag tendencies in static drilling fluids, however their equipment was not able to distinguish between settling and sliding. They also found that their data, based upon standard API rheological parameters like PV and YP, were unsuitable for prediction of sagging behaviour. It is apparent from previous works that the most difficult part of the problem is the prediction of drilling mud instabilities for both static and flowing drilling fluids. To date there are no API test procedures for sag testing. A new simple laboratory tool was therefore designed for the purpose to study and develop a method to predict sagging. Drilling Mud Separation Settling of Particles In vertical wells the settling of weighting material is generally not a problem due to the long settling distance. In horizontal wells the distance to the lower side of the wall is only about 0.2 m, which leads to rapid generation of solids beds. The settling velocity of a single spherical particle, vs,l, in a fluid is expressed by Stoke's law(6): Equation 1 (available in full paper) A barite particle (ρp = 4,200 kg/m3) with a diameter (dp) of 20 µm in a fluid of density (ρfluid) 1,500 kg/m3 and a viscosity (µ??of 40 cP will settle at a rate of 53 mm/h.

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Section: Introductionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Barite Segregation In Inclined Boreholes

Skalle

Backe

Lyomov

et al. 1999

Journal of Canadian Petroleum Technology

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“…A high density and acid-soluble option is Mn 3 O 4 (Bern et al 1996). Svendsen et al (1995) introduced Mn 3 O 4 to potassium formate drilling fluid to increase its density to 106 lbm/ft 3 (1698 kg/ m 3 ).…”

Section: Weighting Agents In Drilling Fluidsmentioning

confidence: 99%

Formation Damage Caused by Improper Mn3O4-Based Filter-Cake-Cleanup Treatments

Moajil

Nasr‐El‐Din

2013

Journal of Canadian Petroleum Technology

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Summary Cleanup of filter cake is a difficult task and becomes more challenging when dealing with weighting materials [e.g., manganese tetraoxide (Mn3O4)]. Mn3O4 is a strong oxidizing agent and can be used as a catalyst because of its active phase, a nonstoichiometric Mn3O4 composed of an octahedral Mn2O3 phase and a tetrahedral MnO phase, which will result in complex interactions with most cleaning fluids. The reaction of selected organic acids and chelating agents with Mn3O4 particles as a function of time and temperature was studied. Solubility and compatibility tests of Mn3O4 particles with cleaning fluids were conducted using a high-pressure/hightemperature (HP/HT) see-through cell. Reaction kinetic tests were conducted using a three-neck round-bottom flask. Atomic absorption was used to measure manganese concentration, and X-ray diffraction was used to analyze solids remaining after the reaction. A white precipitate of manganese citrate was produced following the reaction of citric acid with Mn3O4 up to 284°F. The amount of precipitate was increased with temperature and initial acid concentration. An amino polycarboxylic acid chelating agent derived from L-glutamic acid (GLDA) (a chelant) reacted with Mn3O4 particles completely at 190°F. However, a large amount of a white was precipitate produced. Similarly, a white precipitate was observed with oxalic and tartaric acids. The reaction of diethylene triamine pentaacetic acide (DTPA) (a chelate) with Mn3O4 particles in a glass reactor produced Mn (silicates) at 212 and 284°F. The results of the present study will help drilling/completion engineers avoid using such cleaning fluids to prevent formation damage after filter-cake-removal treatments.

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“…Bern et al 10 presented a comprehensive analysis of these important variables and provided recommendations in key areas involving well planning and operational practices. Several important findings from this study were later verified by Dye et al 9,11 Both studies identified a critical annular velocity of 100 feet per minute, above which dynamic barite sag is reduced.…”

Section: Introductionmentioning

confidence: 99%

Drilling Processes: The Other Half of the Barite Sag Equation

Dye

Mullen

Gusler

2003

SPE Asia Pacific Oil and Gas Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractBarite sag is a well recognized, but poorly understood phenomenon in the drilling industry. Historically it has been associated with a static well environment; consequently test devices and rheological measurements were originally based on static conditions. Dynamic barite sag is now recognized as the major contributor to sag-related drilling problems. There are two prominent variables conducive to creating dynamic sag; 1) low shear rate conditions (drilling process-related) and 2) insufficient ultra-low shear rate viscosity (drilling fluidrelated). Dynamic sag is not entirely a mud-related problem and, under certain conditions, will occur despite appropriate control of drilling fluid viscosity.Barite sag is typically attributed to the mud system and the traditional approach to manage barite sag is to modify (increase) certain rheological properties of the mud system. These efforts are often frustrating because; 1) the proposed solution is ineffective, 2) the solution creates a new problem such as ECD management and 3) expectations are not met. This paper proposes that dynamic sag is related to both the drilling process and drilling fluid, and that these two variables cannot be treated independently from one another.

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The Influence of Drilling Variables on Barite Sag

Cited by 57 publications

References 12 publications

Barite Segregation In Inclined Boreholes

Barite Segregation In Inclined Boreholes

Formation Damage Caused by Improper Mn3O4-Based Filter-Cake-Cleanup Treatments

Drilling Processes: The Other Half of the Barite Sag Equation

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