8-张8

NEW MACHINERY AND EQUIPMENT DESIGN OF A PUMPING UNIT WITH HYDROSTATIC TRANSMISSION FOR WELL CEMENTATION E. S. Ibragimov UDC 622.245.42:621.65-112 Cementation of oil and gas wells is carried out with special equipment which includes pumping units which are designed for pumping mud into the hole. During cementation, be- cause of the limited time available before the initial setting of the cement slurry, the pumping units must work at full power throughout the operation. However, their pressure and delivery are not constant. The pressure is determined by the difference in hydrostatic columns of slurries of different density in the casing string and in the annulus (between the casing and the walls of the well), and also by the hydraulic resistances dependent on the velocity of the slurries in the hole, while pump delivery at constant power varies inversely with pressure. Thus, during cementation of a hole of depth L, drilled with a bit of diameter d3, and cased with pipes having an outer diameter d 2 and an inner diameter d I using a drilling and squeeze fluid of density YI and a cement slurry of density 72, the pressure of the pumping units at the initial instant, when the cement slurry is just beginning to enter the casing, is (Fig. la), pl =Zph =/)h. s in~-Ph.cl -~Ph.a I where Ph.s Ph.cl, and Ph.al are pressure losses in overcoming hydraulic resistances during the movement of the cement slurry in the lines connecting the pumping units with the well- head, and of the drilling fluid in the casing and in the annulus, respectively~ In accordance with the data in [i] Ph s 05 k f61Y~lv2~i - -8 ,1 ~-~lJTJQ-~ �9 do id~ ' Ph.cl:O,05 Lc] 7~L~'~< --8,1 Zci 1,~LO~d~_~_; Ph a1:0,05 ~'al u ----8,1 tal'ftQ~L -" d3- -d2 (d~--d._,) '~ (d :~+dj 2 ; the total pressure losses being y~LQ~Ik~ v2la~ d~ ] where Is Ici, and ial are the coefficients of the respective hydraulic resistances; do, s and i are the diameter, length and number of the lines from the pumping units to the well- head, respectively; ~s Vcl, and Val are the slurry velocities in the casing and annulus, m/sec; Q is the delivery of the pumping units, dm3/sec. The expression in square brackets is the reduced coefficient of hydraulic resistances Ire I. Then we can write pl----8,1 ~rel yILQ~ ~T-- For a useful power N (total) of the pumping units used in the operation, delivery is QI = N/Pl and consequently the pressure losses can be expressed as :2~$/ krel ~,',LN z pl V Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 9, pp. 1-5, September, 1992. 0009-2355/92/0910-0527512.50 �9 1993 Plenum Publishing Corporation 527 ~n.-+-, - - |~ l -m+l - m.-~- i -m~ -m'+ ' a Fig. 1. b . i - ~2 -I- C -i - - fl Diagram of the cementation steps. K-- yILN2 Denot ing - -~ , we obta in p l=2~re~K - ( in th i s express ion ~l i s in g/cm 3, L in m, and dl in cm). As cement slurry with a density greater than that of the drilling fluid is pumped into the casing, the difference in hydrostatic pressure between the columns of fluid in the casing and the annulus increases. As a result, the pressure of the pumping units falls, despite some increase in the hydraulic resistances due to the increase (for constant power of the pumps) in the delivery of the cement slurry and in the velocity of the fluids in the hole. Only after pumping the whole volume of cement slurry, during its motion in the casing, the pump pressure and delivery are stabilized and remain unchanged until the cement slurry passes into the annulus. For the full volume of cement slurry in the casing string W I (Fig. Ib), the pressure of the pumping units is P2=P~L@ZPh2 , where &t=0.01hl(u is hydrostatic pressure of the columns of cement slurry, drilling and squeeze fluids; h=W~/O.785d~ is height of the column of cement slurry in the casing (expressing ~,----hl/i, we obtain pd-~-O.OIBIL(7i--u ); 2Ph2 is pressure losses in overcoming the hydraulic resistances during the motion of the squeeze fluid in the lines from the pump- ing units to the wellhead (Ph.s and in the casing (Ph.c2), and also of the cement slurry in the casing pipes (Ph.a2) and of the drilling fluid in the annulus (Ph.a3), i.e., ZPh 2 ----Ph.s or = ~ ^Z2 ~ -~t c3 ~ l ..~a2(da.d=)a (daq_d2)Zj �9 We denote the expression in square brackets by Ire 2, then Epc 2= 8,1 Zre2 ?ILQ~. 2 p2=O,O L (w--w)+810 re ,Q2] d~ The corresponding delivery is Q2 = N/P2. Substituting it into the expression for P2, we obtain p23--p~0,01 ~, (?, --?~) L =8,45 ~re2 v,LN ~ or 3 2 p2--p20,Olh,(21--Y~) =8,45XregK- The cub ic equat ion obta ined on the bas is of the recommendat ions in [2] is so lved by substituting into it the expression 528 ;. MPa I I i / g 2 # g /< kW . . . . . ] !- I 735 - - [ ' I N /2 /4, t, mln Fig. 2. Changes in power N, pressure p and delivery Q of pumping units in time t of cementation. a p2=g- - O,Olh , (?~- -Y2) -=g 3 ' where y is the roots of the incomplete cubic equation. As the cement slurry passes into the annulus the pump pressure again rises (because of the fall in hydrostatic pressure) and the delivery, and consequently also the hydraulic resistances in the casing--annulus system declines. At the instant when the heights of the columns of cement slurry h 2 in the casing and the annulus are the same (Fig. Ic), the losses of pressure in the pumping units are Ps := Epha ----= Ph. Z3@Ph.c , - t -Ph .cs+Ph.a a ~J- P h.a4 " Here, the losses of pressure in overcoming the hydraulic resistances during the motion of of the fluids are as follows: Ph.s for the squeeze fluid in the lines from the pumping units; Ph.c4 and Ph.cs for the squeeze fluid and cement slurry in the casing; Ph.aa and Ph.a4 for the cement slurry and drilling fluid in the annulus. The pressure of the pumping units can be represented in the form: p3=8,1 --d"7[~.% 3 i-~f~ @-Lc~([--~32)-~-)'c5fi2 ~-, + ?t where l J2=h~/L; h2=W, /0 ,785 2 2 (d, + d3- - d$). We denote the reduced coef f i c ient o f hydrau l i c res i s tance by Xrea ; in th i s case ~-re3 y,LQ~ p3=8,1 &-~--- - The corresponding delivery of the pumping units is Q3 = N/Pa, then p3 = ~ = 21/~ re3 K. At the instant when the whole volume of cement slurry W I passes into the annulus (Fig. id) and rises to height h3, the pressure of the pumping units is p4=pr where Pc2 = 0,01h3(y2--yl) is the hydrostatic pressure; ~Ph4 is pressure losses in overcoming the hydraulic resistances during the motion of the squeeze fluid in the lines from the pumping units to the wellhead (Ph.L~) and in the casing (Ph.cs), and also of the cement slurry (Ph.as) and the drilling fluid (Ph.as) in the annulus. In expanded form y,Lq~f ~. ld~ ~3y2d~ d 5' >2ph. : 8,1 - -~ l [ s 43 @ kc6~- )~a57; (d3_d2)3 (d3+d2)2 @- ~as( l - - ~3) (d3--d~) ~ i'd3+d~-T] ' where P3- -h3/L . 529 p: MPa i 80 l ~ - -h ....... V I \ X ,;' 0 I \ i ~ L 0 ?,7 2g 3~'J 40 ~ dm~/sec Fig. 3. Characteristics of pumping units: respectively, with hydrostatic delivery and UNBI-400 • 40, diameter of plunger 70 (I), ii0 (3), and 140 (2, 4) mm. We denote the reduced coefficient of hydraulic resistances by kre~, then Wph4=8,1%re 4.7~LQ.~24 d? ' The pressure of the pumping units is p4-~O,Olf13 (y2--Y,) ~-8,1 ~re4 v'LQ] d? The pump delivery is Q4 = N/P4; substituting it into the expression for P4, we obtain p~--p~O,Olh:~ (V2--Y~) --~8,45)~re4 A'. This equation is solved by substitutin B into it the expression P4-~-Y4" JO,Ol /b(] '2- - ] '~) ---~-y ,-~- a -74-a , 0 We determine the time corresponding to each of the cementation steps considered. For this purpose, we proceed from the average pump deliveries for the given step. The time for pumping the full volume of cement slurry W I into the easing is -~!(~-~ W2- ~ 0,0026 otha (d~- d~) p, p=, l~-~ Oavl '60 N(p~+p~) where a is the coefficient that takes into account the presence of cavities in the hole (we assume that a = 1.05-1.3). The time for pumping squeeze fluid of volume W:=:O.785d~(L--h~) is 10~2 =O.OOi[~ (LIhl) d~P2 t'2 ~ Q~. 60 N The time for pumping a part of squeeze fluid with a volume W3=O.785d~(h~--h~), which displaces the cement slurry by one level in the casing and annulus is ta= Oav2.60 =o.oo25 . N (p2+p3) The time for displacement of the cement slurry volume (W z 10 a (t~, -- Wa) 0 0096 h2d~pap4 Q ava -60 N (P3+PO -- W 3) in the annulus is 530 Fig. 4. Pumping unit with hydrostatic transmission: I) truck chassis; 2) unit; 3) measuring tank; 4) oil cooling system; 5) oil tank; 6) hydraulic motor; 7) high-torque hydraulic motor; 8) high-pressure pump. We consider how the pressure and delivery of the pumping units change in time in the specific case of cementation of a hole with a depth of L = 2000 m and a diameter d 3 = 21.4 cm. It is cased with pipes with an outer diameter d 2 = 14.6 cm and an inner diameter d i = i2.2 cm; the dril l ing and squeeze fluids used had a density of ~i = 1.23 g/cm 3 and the cement slurry with a density of ~2 = 1.83 g/cm ~ rose to a height h 3 = 500 m. The total useful power of the pumping units N was 235 kW, and the pumps were connected to the wellhead by one line (i = i) with a length ~ = 20 m and a diameter d o = 5 cm. The volume of the cement slurry is ~ = 0,785~h~(d~-- d~) = 0,785.1,25. 500(0,2142 - - --0,1462)----12 m 3. The heights of the columns of cement slurry are: h I = 1027.05 m; h 2 = 388.38 m; co- efficients 61 = 0.513; $2 = 0.194; 63 = 0.25. The coefficients of hydraulic resistances in accordance with the data of [3] for a turbulent regime of motion of the fluids in cases of generalized Reynolds numbers Rec* 3000 and Rea* ~ 2000 can be assumed to be: in the casing i s in the annulus ia=0.12/~Rec~0,04. The reduced coefficients of hydraulic resistances are Ire I = 0.084; Ire 2 = 0.08; Ire ~ = 0.062; Ire 4 = 0.077; parameter K = 502.657. Then the pressure of the pumping units in the different steps of cementation are: pz = 7 MPa; P2 = 5.42 MPa; P3 = 6.3 MPa; P4 = 8.2 MPa~ The corresponding deliveries are Ql = 33.57 dm3/sec; Q2 = 43.32 dm3/sec; Q~ = 37.3 dm3/sec; Q4 = 28.66 dm3/sec. The time of pumping the slurries is tl = 5.17 min; t 2 = 4.34 min; t 3 = 3.06 min; t4 = 2.28 min. On the basis of the calculation results, we plotted a graph showing the changes of pressure and delivery of the pumping units in time (Fig. 2). The nature of the change in the parameters corresponds to the operation of the pumps with constant uti l ization of full power during the whole cementing operation. This mode of operation can be ensured by pump- ing units with stepless or multispeed transmission that allow regulation of delivery over a wide range of pressures. Pumping units such as the UNBI-400 x 40 and UNBI-160 • 40 have four-speed transmissions. They consist of one high-pressure pump and a low-pressure pump for supplying water to the mixer during preparation of the cement slurry. These pumping units only use full power in four modes (see Fig. 3). In the other modes, their power is underutil ized, and this reduces their eff iciency and may make it necessary to use additional pumping units. Pumping units for cementation manufactured abroad generally have hydromechanical or 10-15 speed transmissions. The units comprise two high-pressure pumps. 531 It should be noted that, while multistage transmissions allow sufficiently full uti- lization of installed power, they are, at the same time, complicated to control (especially remotely). Switching the transmission involves interruption of the power flow and loss of time in raising pump speed. Over a certain range, hydromechanical transmissions ensure stepless and automatic change in pump delivery and permit remote control from a console located at a distance. However, this type of transmission has a relatively low efficiency. Better results can be obtained by using high-efficiency hydrostatic transmission which permits stepless and automatic regulation of the mode of operation of the pumping unit over a fairly wide range, with full power utilization, together with remote control by one op- erator from a centralized console. The hydraulic lines connecting hydraulic pumps with hydraulic motors do not impose restrictions on the mutual arrangement of the components of the pumping unit on the mounting platform and make it possible to drive each high-pressure pump from any of the motors in the unit and, if necessary, to drive two pumps from one motor. The utilization of two high-pressure pumps in pumping units is highly effective. This doubles the delivery, makes it possible at the start of operation to supply water to the mixer with one pump and to pump the cement slurry into the hole with the second one, to improve the reliability of the operation (if one pump fails, operation can be continued with the other), and renders standby pumping units unnecessary. The new pumping unit for well cementation has hydrostatic transmission and two high- pressure pumps with a useful power of 350 kW, a maximum pressure of i00 MPa and a maximum delivery of 50 dm3/sec. Technical Characteristics Pumping unit .................... New UNBI-400 x 40 Useful power, kW .................... 350 280 Maximum pressure, MPa .............. I00 40 Maximum ideal delivery, dm3/sec ..... 50 37 High-pressure pump: number ........................... 2 1 maximum pressure, MPa ............ i00 40 delivery, dm3/sec ................ 25 37 Motor: type ............................ YaMZ-238D V2-500AV-SZ full power, kW ................... 240 370 Transmission ....................... Hydrostatic, Mechanical, stepless four-speed Capacity of measuring tank, m 3 ...... 5 5.5 Diameter of nominal bore of mani- fold, rmn: intake ........................... i00 i00 delivery .......................... 50 50 Mounting platform (truck) ........... KrAZ-260G KrAZ-250 A possible composition of the pumping unit is shown in Fig. 4. The unit is mounted on a truck chassis KrAZ-260G. Two high-pressure pumps are driven by controlled high-torque hydraulic motors which are directly connected to the main shaft of each pump. Behind the pumps are reducers with the working and feed hydraulic pumps (pressure of 32 MPa) connected to them and the oil tank. Here also are the the control console and the measuring tank with remote-controlled bottom valves. The reducers are kinematically connected: one with the truck engine and the other with an on-board diesel motor YaMZ-238D. The system for cooling the hydraulic system oil is common with that of the diesel motors. The pumping unit mani- fold is so designed that fluid can be taken in from the measuring tank and also from the outside (especially from the tank with the cement slurry). The delivery line is separate, and is fitted with valves with ball plugs and with multi-action safety valves. The unit is equipped with an information system which monitors the parameters and warns the operator of deviations from normal operating conditions, and also provides diagnostic information. Figure 3 shows changes in delivery for the new pumping unit as a function of pressure, and also for the series-produced unit UNB1-400 x 40. As can be seen, the use of hydrostatic transmission does in fact ensure stepless regulation of the operating conditions of the unit. 532 Io 2. 3. LITERATURE CITED E. S. Ibragimov, "A method for determining the number of pumping and mixing units needed for well cementation," Neftyanoe khozyaistvo, No. 12, 19-23 (1971). G. Korn and T. Korn, A Manual of Mathematics for Scientists and Engineers [in Russian], Nauka, Moscow (1984), pp. 43-44. B. I. Mitel'man, Pressure Losses in the Circulation Systems of Drilling Rigs [in Russian], TsNllT~neft', Moscow (1957). STEPLESS UNIVERSAL PIPE WRENCH A. A. Khalilov UDC 622.24.053.6:621.883.6 One of the most important and laborious tasks in oilfield operation is underground repair of oil wells. The repair work mainly involves lowering and raising of pipes, drill rods and well pumps. The lowering-raising operations are carried out very frequently in a cyclic manner. Thus, even a small reduction in the time taken for any individual opera- tion during lowering or raising of the parts has a significant effect on the time taken for the entire process. About 60-65% of the time taken for lowering and raising of pump-compressor pipes during underground repairs involves work with a wrench (fitting the wrench, screwing or unscrewing of pipes, removing the wrench). The wrench is the main tool used continuously by the worker for manual or mechanized screwing and unscrewing of pipes, couplings and rods~ Thus, labor productivity depends upon the design of the wrench. Therefore, it is important to develop a reliable and convenient tool for screwing and unscrewing pump-compressor pipes, couplings of pump pipes, and parts of well pumps during underground repair of oil wells. The wrench should be suitable both for manual and for mechanized work and should be of universal de- sign (to grip pipes of different diameters). The chain wrenches and individual wrenches of different designs used earlier had sig- nificant disadvantages. Considerable time was wasted in fitting and removing the wrenches from the pipes, because they were heavy, inconvenient to use, and unreliable in operation. A separate wrench of specific size was required for each size of pipe, coupling and rod. These disadvantages have been eliminated in the wrench developed by the author (Khalilov wrench, Inventor's Certificate No. 249,303). Production of the Khalilov wrench was taken up for the first time at the Volodarski Baku machine-building plant. Currently, these wrenches are mass produced by the Khadizhensk machine-building plant and the Bakinskii Rabochii machine-building plant. The kinematic design of the new wrench (see Fig. I) is based on the principle of grip- ping the external diameter of the pipe at three points. This design enables stepless grip- ping of pipes within a predetermined range of diameters (D and d represent the maximum and minimum diameter of the pipes to be gripped). In practice, the pipes, rods, and couplings usually have external diameters from 20 to 132 mm. It is convenient to cover this diameter range with three wrench sizes which can be used to screw and unscrew pipes of all sizes. The first size covers diameters from 20 to 48 mm, the second from 48 to 89 mm, and the third from 89 to 132 mm. Taking into account wear in operation and manufacturing errors in the pipes and couplings, each size of wrench has been designed to handle diameters 2 mm more or less than the respective nominal maximum and minimum diameters. Thus, the three sizes of wrenches can, in effect, be used for pipes with external diameters from 18 to 135mm. Technical Characteristics of the Wrenches Type ................................... KTKh20-48 KTKh48-89 Maximum torque, kN'm ................... 2 4 Nominal diameter of pipes to be screwed or unscrewed, n~n ...................... 20-48 48-89 KTKh89-132 6 89-132 Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 9, pp. 5-7, September, 1992. 0009-2355/92/0910-0533512.50 �9 1993 Plenum Publishing Corporation 533