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OFS INFLUENCE OF TEMPERATURE GRADIENT ON DDM ELASTOMER STABILITY DURING SIMULATION OF TRIPPING PROCESSES THE ARTICLE IS DEVOTED TO THE EXPERIMENT ON EVALUATION OF STABILITY OF THE DOWNHOLE DRILLING MOTOR ELASTOMER UNDER THE INFLUENCE OF TEMPERATURE GRADIENT DURING SIMULATION OF TRIPPING PROCESSES. THE CHANGES OF DIAMETER OF IRP-1226 RUBBER SPECIMENS IN THE PRESENCE OF DIFFERENT DISPERSION MEDIUMS, AS WELL AS THEIR WEAR RATE AFFECTED BY CUTTER WERE INVESTIGATED. THE RELEVANCE OF DEVELOPMENT OF THEORETICAL APPROACH TO DESCRIPTION OF THE PROCESSES OCCURRING IN ELASTOMER UNDER THE INFLUENCE OF DOWNHOLE CONDITIONS AT DIFFERENT STAGES OF THE DOWNHOLE DRILLING MOTOR OPERATION WAS CONFIRMED. IT WAS NOTED THAT IMPROVEMENT OF SPECIMENS WEAR RESISTANCE DURING LONG-TIME EXPOSURE TO TEMPERATURE IN SALT BRINE COULD BE USED TO INCREASE THE STATOR LIFE DURATION UDC 622.24 KEY WORDS: elastomer, DDM, well, drill mud, down hole motor. Anton V. Epikhin, Senior Lecturer at the Department of Well Drilling, Institute of Natural Resources, National Research Tomsk Polytechnic University Roman E. Shcherbakov, student of the Department of Borehole Drilling, Institute of Natural Resources, National Research Tomsk Polytechnic University Over the past ten years the downhole drilling motors have evolved into an effective technical device for oil and gas well drilling and servicing ensuring high technical and economic indices. In every oil sector at specific drilling intervals the downhole drilling motors have provided a severalfold increase of penetration per run in comparison with turbodrill at a slight decrease in drilling rate, leading to a significant increase in drilling speed per run and decrease in cost per 1 meter of penetration. Solving problems of servicing the wells of different categories has become much easier and cheaper; workover technical capabilities have been expanded making it possible to include the long-term suspended emergency wells into the number of producing ones in some cases [1, 2]. PS is one of the names of power section of the downhole drilling motor. That is the detail that defines the main energy parameters of the down hole motor, as well as its lifetime and mean time before failure. With all its advantages, a disadvantage of the downhole drilling motor is the rapid wear of power section. Engine real operating time is 150 – 200 hours to the estimated operating time of 400 – 500 hours [3]. In the process of the downhole drilling motor operation, different types of wear of working surfaces of rotor and stator, depending on the mode of operation, properties and composition of conveyed fluid are observed. Analysis of operating conditions and nature of operating device worn parts demonstrates the combination of more than one type of wear. In the main the engine malfunction is related to wear of the stator elastomer insert [3 – 5]. Friction of the profile metal rotor over the conjugated screw surface of the stator elastomer insert causes one-sided friction wear of the operating device surfaces – on the left side of the rotor teeth or on the right side of the stator profile branch, viewed from the side of fluid inlet into the operating devices. Increase in load (pressure) and sliding velocity (speed of rotation) result in higher level of parts friction wear and premature failure of power section [4]. The elastomer operability depends on the combination of the elastomer insert strain-stress state and 34 ~ Neftegaz.RU [3]
OFS conveyed fluid corrosive properties. Therefore, during the downhole drilling motor operation it is necessary to pay special attention to the selection of appropriate drill mud. The elastomer as technical material should have a low gas impermeability and water tightness, as well as chemical resistance. However, most elastomers are able to absorb gas and lightly corrosive fluids. The following are typical changes the elastomers are subjected to: swelling, shrinkage, solidification, softening [2, 4, 5]. Furthermore, the bottomhole temperature is a limiting factor for engine operation. Series-production domestic engines are designed for long-term operation at the bottomhole temperature up to 100°С. At the rise in temperature in IRP-1226 rubber (used in most domestic engines) irreversible changes of mechanical properties occur leading to faster wear of the stator elastomer insert, performance deterioration and premature failure of the down hole motor power section. As a result, it was decided to carry out the experimental researches on evaluation of stability of IRP-1226 rubber specimens at engine temperature rise under the influence of different mediums. During this experiment the process of drill-string running was simulated; running speed was assumed to be 1.5 m/s. The following parameters were determined as the design basis: total vertical depth – 2,670 m, geothermal gradient – 3°С/100 m, drillpipe stand length – 30 m (deemed time for making a connection – 4 min). The following items were calculated in accordance with the initial parameters: experiment duration – 384 min, engine end temperature – 80°С. Simulation of drill-string running and consequently the rise of drill mud temperature were carried out in a desiccator. Test specimens were made in the shape of cylinder with diameter up to 43 mm and thickness up to 11.5 mm. They were kept in plastic containers with total immersion into the liquid medium. Processing the experiment results, the changes of the specimen weight and its diameter at the temperature rise in the liquid medium were assessed. Initial measurement of input parameters was made at the temperature of 25°С; further measurements were made after every 5°C rise in temperature, simulating then the drill-string running for 165 m (23.5 min of the experiment). Reaching the depth of 1,680 m, the specimen parameters were measured after every 10°С rise in temperature, simulating then the drill-string running for 330 m (50 min of the experiment). Processing and analyzing the obtained data, the following correlations were exposed. After completion of the experiment, the weight reduction was observed for all specimens. Nevertheless, in the temperature range of 25 to 50°С most specimens had no expressed tendency towards weight variation; its random variation was observed. The exceptions were the specimens immersed in the salt brine; these specimens demonstrated the tendency towards the weight reduction throughout the experiment. The specimens immersed in solution based on diesel fuel, oil and multigrade lowtemperature hydraulic oil (see Table 1) were subjected to maximum relative weight variation. The weight reduction can be attributed to the washing-out of rubber plasticizer from IRP-1226 specimens. For all specimens, it was recorded the growth in diameter as the temperature became closer to 80°С. The temperature range of 25 to 40 – 50°С has no clear tendency towards an increase or reduction in size of the specimens which is illustrative of the potential danger for elastomer. The maximum relative diameter change was demonstrated by the specimens immersed in multigrade lowtemperature hydraulic oil, salt brine and oil. The specimens placed in the alkaline solution (see Table 1) were subjected to the minimum relative diameter change. Thus, the whole temperature interval studied for the analyzed dispersing mediums may have a negative impact on the DDM stator. Uncontrolled variation of engine performance can occur within the range of 25 – 50°С due to the change of gap width and consequently the tightness FIG. 1. Dependence of IRP-1226 specimen diameter change from temperature in the presence of different dispersing mediums [3] Neftegaz.RU ~ 35
Page 1: 10 years FISHBONE HORIZONTAL WELLS
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Page 13 and 14: RUSSIA main Russia needs technologi
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Page 30 and 31: OFS HORIZONTAL WELLS WITH MULTI-STA
Page 32 and 33: OFS nine-points development pattern
Page 34 and 35: OFS FIG. 6. Oil flow rate decline c
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Page 49 and 50: DRILLING Well design 520 mm borehol
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Page 53 and 54: DRILLING stabilization of near-well
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Page 60 and 61: EQUIPMENT FIG. 4. Diagram of the mi
Page 62 and 63: EQUIPMENT CEMENTING OF CASING STRIN
Page 64: EQUIPMENT SUMMIT INTERNATIONAL: Sol
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Page 69 and 70: SPECIAL SECTION Classifier DRILLING
Page 71 and 72: PRODUCTION flooding do not allow ac
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Page 87 and 88: SPECIAL SECTION Classifier ROLLING
Page 89 and 90: A.Parshikov, A.Fedin T. Rott A.Skvo
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