外文翻譯--最新技術(shù)進(jìn)展使有桿抽油系統(tǒng)比esp系統(tǒng)效率更高（譯文）

1、 SPE 136880 Latest Technological Advances in Rod Pumping Allow Achieving Efficiencies Higher than with ESP Systems Gabor Takacs, SPE, Hadi Belhaj, SPE, The Petroleum Institute Copyright 2010, Society

2、 of Petroleum Engineers This paper was prepared for presentation at the Abu Dhabi International Petroleum Exhibition illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright

3、. Abstract Two of the most important artificial lift methods applied in oil wells are sucker-rod pumping and electrical submersible pumping with thousands of installations all over the world. Their operational features

4、 and application ranges are quite different but in many cases any of them can be used in a given well. The final selection of the proper method has to be based on their energy efficiency and the one requiring the least

5、 amount of surface power input is selected. This paper provides the necessary background for evaluating the effectiveness of the two lift methods investigated and for pinpointing the requirements of achieving maximum p

6、ower efficiency of artificial lifting. The power flow in the pumping system is investigated and the sources of power losses along with their usual ranges are described. The overall power efficiency of the system is def

7、ined by a simple formula that provides the necessary insight into the main components of the power losses occurring in different system elements. A thorough investigation of the efficiency ?????????????????????????????

8、???????????????????????????????????????????????????????????????wer requirement. As shown in the paper, the most important requisite of achieving maximum effectiveness is the proper choice of the pumping mode, i.e. the

9、combination of plunger size, stroke length, and pumping speed. The calculation of energy losses in the components of the ESP system is detailed and the relative importance of the individual losses is shown. Since the c

10、omponents of the ESP system are connected in series, a relatively simple formula can be used to describe the effect of electrical and hydraulic losses on the efficiency of the total system. The terms of the final formu

11、la were investigated for their importance and for their contribution to the overall effectiveness of the ESP system. Results of this investigation provide crucial information on how to design an ESP system to provide th

12、e highest power efficiency. The practical use of the proposed calculation models is illustrated by presenting an example case where a relatively high liquid rate (1,300 bpd) from the same well is produced by rod pumpi

13、ng and ESP. Detailed installation designs resulted in several different operation modes for both sucker-rod pumping and ESP. The paper proves that using the latest technologies like high-strength sucker-rod connections

14、, sucker-rod pumping can successfully compete with ESP installations by attaining higher energy efficiencies. Introduction When production of large liquid rates from deeper wells is desired, the use sucker-rod pumping

15、installations is usually ruled out and ESP or gas lifting is considered only. The main reason for this attitude is the well-known limitation on the strength of steel sucker rods. Steel rods are heavily loaded by their

16、own weight alone so pumping from greater depths imposes loads and stresses that rods do not tolerate and break. This situation is the basic driver for the introduction of stronger and stronger rod materials for rod pum

17、ping. The strength of sucker rods is best defined by their fatigue endurance limit because most sucker rod breaks are fatigue failures occurring at stresses well below the ultimate tensile strength or even the yield st

18、rength of the steel used. Material fatigue is a plastic tensile failure due to repeated stresses like the pulsating tension loading of the rod string. Typical failures start at some stress raiser (a surface imperfectio

19、n like a nick, a corrosion pit, etc.) on the surface of the rod, and slowly progress at right angles to the direction of the stress, i.e. across the rod material. The load carrying cross section is thus progressively r

20、educed until the remaining metal area is overloaded and breaks. The industry witnessed a continuous technological development as the wooden hickory rods originally used in the early pumping wells were replaced by stron

21、ger and stronger steel rods. API Grade D rods, being the strongest a few decades ago, are being replaced by special high-strength rod materials like Norris 97, Trico 66, etc. The latest development is a premium rod SPE

22、136880 3 PRHPP hydr lift ? ?(2) where: Phydr = hydraulic power used for fluid lifting, HP, PRHP = polished rod power required at the surface, HP. Surface mechanical efficiency Mechanical energy losses occurring in t

23、he drive train cover frictional losses arising in the pumping unit, in the gearbox, and in the V-????????????????????????????????????????????????????????????????????????????????????????????Pmot, is always greater than

24、the polished rod power, PRHP. It is easy to describe these losses by a single mechanical efficiency: mot mech PPRHP ? ?(3) where: Pmot = mechanical power required at the motor shaft, HP. Motor efficiency To represent

25、all losses in the electric motor, an overall efficiency factor can be used, that allows the calculation of the average electric power drawn from the po????????????????????????????????????????????????????????????????????

26、??? emot mot PP ? ?(4) where: Pe = required electrical power input, HP. Maximizing system efficiency Since system efficiency is defined by a three-term formula (Eq. 1) the investigation of those individual terms allow

27、s one to draw important conclusions on the possible ways of attaining maximum energy efficiencies in rod pumping operations. Average values of the surface mechanical efficiency are high, usually over 90% in favorable c

28、onditions; i.e. for a properly maintained pumping unit and gearbox. There is a consensus in the technical literature that this efficiency increases as gearbox loading approaches the rated capacity of the unit. As regar

29、ds motor efficiencies, electric motors used in pumping service may have full load efficiencies close to 90% under steady loads. Actual values, however, belong to load ranges between 30% and ???????????????????? ???????

30、???????????????????????????????? Lea et al. [ 2 ] present motor efficiencies of 78% - 91% for NEMA D motors of 5 HP ? 60 HP sizes. As shown, possible values of the surface mechanical efficiency, ?mech, and the motor ef

31、ficiency, ?mot, vary in quite narrow ranges. At the same time, their values can be maximized if the right size of gearbox and electric motor are selected. A properly maintained pumping unit with a gearbox operated near

32、 its torque capacity ensures mechanical efficiencies greater than ?mech = 90%. A properly selected electric motor can also provide relatively high ?mot values. Thus the combined efficiency of the drive train and the mo

33、tor (?mech ?mot) can lie in the range of 67% - 88%, as given by McCoy et al. [ 3 ]. In contrast to the usual ranges of the above efficiencies, lifting efficiency, ?lift, can vary in very broad ranges depending on the p

34、umping mode (plunger size, stroke length, and pumping speed) selected. At the lower end of possible values, consider the case of a worn-out pump producing a very low amount of liquid achieving a negligible hydraulic pow

35、er, Phydr, while still consuming a definite power at the polished rod, adding up to a lifting efficiency value of almost nil. On the other hand, wells with big size pumps and low pumping speeds can require little more

36、than the hydraulic power at the polished rod under ideal conditions. For example, Takacs [ 4 ] reports lifting efficiencies between 94% and 38%; according to Gault [ 5 ] considerable improvements on lifting efficiencie

37、s can be realized by selecting the optimum pumping mode i.e. the combination of pump size, polished rod stroke length, pumping speed, and rod string design. In summary, the basic requirement for achieving high overall

38、system efficiencies is to find the maximum possible value of the lifting efficiency. Since this is accomplished by the proper selection of the pumping mode, the choice of the right combination of pump size, polished ro

39、d stroke length, and pumping speed is of prime importance. When designing a new pumping system or improving the performance of an existing installation, this must be the primary goal of the rod pumping specialist's

40、 efforts. The pumping mode of a sucker-rod pumping system is defined as the combination of pump size, polished-rod stroke length, pumping speed, and rod string design. The number of available combinations of these para

41、meters is enormous if one considers that API standards contain: (a) more than 10 plunger sizes, (b) about 20 stroke lengths, (c) six sucker rod sizes, and (d) pumping speeds can be anywhere below 20 SPM. For producing