annual 2010/2011 of the croatian academy of engineering - HATZ

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42 LUBRICANTS Annual 2010/2011 of the Croatian Academy of Engineering Friction reduction can be achieved by using a drilling uid with good lubricating qualities such as oil-base uids, polymer uids, and glycol-derivative systems [4]. Oil-based uids often are chosen for extended reach wells because they are highly inhibitive and exhibit good lubrication properties. Unfortunately, their use in environmentally sensitive areas is discouraged or even prohibited [5]. There are also a large number of lubricant additives available; these should be tested for uid and formation compatibility as some of them can have detrimental effects. In general, lubricants may be of a mechanical nature (beads, nut plug, etc.), general borehole or lm lubricants, or extreme-pressure (metal-to-metal) lubricants. Natural grease and oils abandoned because of cheaper oxidant stable mineral oils, are now, because of ecological aspect, used again. Rape oil and castor oil are used in production of biodegradable lubricants. Rape oil has also other favorable properties: good lubricity, high viscosity, good adhesion on metal surfaces and very good load bearing. Problems on high and low temperatures and with foaming can be solved by adding additives. When added in water based mud (WBM) such problems are solved with the use of emulsiers, antifoaming agents and for warehouse purposes pour point depressants. Lubricants are designed to reduce torque to increase horsepower at the bit by reducing the coefcient of friction. In water based drilling uids certain oils, graphite powder, glycols and soaps are used for this purpose. To be economic, a drilling uid lubricant must reduce torque and drag, and operating costs by performing the following functions: • reduce possibilities of twist-offs, • shorten trip time, • lessen the conditions for differential sticking, and • lower the amount of energy necessary to run the rig. Depending on their chemical composition and state of dispersion or solubility in the base drilling uid, lubricants: • can coat metal surfaces, reducing the adhesion of steel to the lter cake; • can be incorporated into the lter cake and provide better uid-loss control (resulting in thinner cakes); and • can be incorporated into the lter cake to reduce the yield stress of the cake. In many uid systems, it was found that the most effective additives are those operating by more than one of the above mechanisms. LABORATORY TESTS AND RESULTS Laboratory tests of the effect of two commercially available lubricants L1 and L2, and new developed lubricant Horma-138 [7] on rheological, ltration and lubricating properties of selected drill-in uids were carried out. They are water-dispersible lubricants designed to decrease the coefcient of friction in all water-base muds, reducing torque and drag. They also have a unique wettability characteristic which lowers the potential of BHA balling [7]. Inuence of addition different concentrations (0%, 2%, 3%) of three lubricants on rheological and ltration properties in different drill-in uids were carried out according API standard using Fann viscometer and API lter press. The three unweighted, water based
Annual 2010/2011 of the Croatian Academy of Engineering 43 drill-in uid systems were tested. Fluids are designated as WBM 1, WBM 2 and WBM 3 (Table 1). Lubricating properties were studied using the Lubricity Tester. Briey a steel test block that simulates the wall of the hole is pressed against the test ring by a torque arm. The torque is measured by the intensity of current that is required to turn the ring at a constant rotation when immersed in the uid that is tested. The API procedure (RP 13B) was followed for the tests, in laboratory tests the rotational velocity was 60 min-1 (60 rpm) and the force applied was 16,95 Nm (150 lb/inch). Results are given as a torque value that can vary from 0 to 50. The lower the value, the better the lubricating properties. The coefcient of friction is calculated from torque reading using adequate formulas. Table 1. Effect of various lubricants on mud properties and lubricating ability It is obvious that adding of HORMA-138 lubricant has the greatest inuence on plastic viscosity and yield point in comparison to uid without lubricants. For all three lubricants there is an signicant reduction of coefcient of friction (COF). Fig. 3 is an illustration of the inuence of lubricant concentration on COF in selected water based muds.
Page 1: ANNUAL 2010/2011 OF THE CROATIAN AC
Page 4 and 5: Published by Croatian Academy of En
Page 6 and 7: Mario Žagar, Ivica Crnkovi, Darko
Page 8 and 9: 8 2011 Annual 2010/2011 of the Croa
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Page 20 and 21: 20 CONCLUSION Annual 2010/2011 of t
Page 50 and 51: 50 Typical example of Commands’ r
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Page 72 and 73: 72 References Annual 2010/2011 of t
Page 82 and 83: 82 Bidlingmaier et al. (1999) Ziehm
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92 Annual 2010/2011 of the Croatian
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100 Annual 2010/2011 of the Croatia
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122 5.0 Conclusion 6.0 References A
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124 2 The Community of Raša Annual
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178 4 EXPERIMENTAL EVALUATION Annua
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194 and lubricant. Annual 2010/2011
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206 4 Results and discussion Annual
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Podupirajui lanovi: Arhitektonski f
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