BALKANTRIB O5 5 th INTERNATIONAL CONFERENCE ON TRIBOLOGY JUNE Kragujevac, Serbia and Montenegro

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1 BALKANTRIB O5 5 th INTERNATIONAL CONFERENCE ON TRIBOLOGY JUNE Kagujeva Sebia and Montenego ESTABLISH THE RELIABILITY OF PISTON-CYLINDER COUPLE OF DOWNHOLE PUMPS Razvan Geoge Rieanu Petoleum-Gas Univesity of Ploiesti Romania aeanu@ug-loiesti.o Abstat Piston-ylinde oule is one of the main omounds of down-hole ums. Piston-ylinde oule woks in sevee abasive and oosive onditions. Pae esents eimental tests made in stati and dynami onditions develo to establish wea laws fo diffeent iston-ylinde mateials at diffeent medium temeatues and essues. It is esented the devies used to establish oosive omound of wea and the devie used fo abasive wea. Wee obtained some oml wea laws fo eah mateial oule deending of medium temeatue essue and omosition and of um wok aametes suh as the dee in well uming veloity et al. With the wea laws obtained it was eated an oiginal inteative omute ogam deending on um tye and woking aametes in ode to establish the lifetime fo istonylinde oule. The duability of iston-ylinde oule is vey imotant beause the um eliability deends on it. The esults obtained with the ogam eated wee onfimed by industial atie. KEY WORDS: ums oosive wea iston-ylinde oule ude oil. 1. INTRODUCTION Oil lifting is mainly made by dee-well uming with iston down-hole ums. 40% fom failues of odution wells ae aused by ums failue and um eliability deends on iston-ylinde and ball valve oule duability. Fo eamis ball valve oule um eliability deends only of iston-ylinde duability. Cude oil ontains an imotant quantity of highly minealized wate ih gases with a geat eent of CO 2 gains of sand fom etolifeous bed. Down-hole ums maniulated by tubing s ae osed to oml wea tis as abasion eosion and oosion. Reliability dietly deends of mateials behavio of istons skits o long ylindes. Main atual dietion to ise woking life of down-hole ums in abasive and oosive medium is to use mateials with high hadness and esistant at oosion as hadhomium lating steel fo ylinde o iston abonitided and nitided ylinde and metalli abide layes tye METCO fo istons in ode to esist at heavy duty ondition. Pae uose is to esent the methodology used to establish wea laws in ode to edit iston-ylinde duability. Beause wee many fatos involved the eiments wee leaded in ode to establish eah fato influene. 2. EXPERIMENTAL RESULTS 2.1 Coosion wea in stati onditions Fom istons and skits we eae samles whose dimensions ae esented in figue 1. At utting and olishing we avoid to ass thew C to not modify metallogahi stutue and the level of intenal stess. The inative faes wee oveed with syntheti esin stabile in fomation wate at maximum testing 435

2 temeatue. Afte eaing seimens wee weighted with analytial balane with 01mg eision. Also wee eaed two witness samles to detemine the esin wate absotion. In figue 2 is shown devie diagam fo oosion testing unde CO 2 essue at diffeent temeatues. Gavimeti indie K g o oosion ate v o was alulated with elation [5]: M k g = vo = g/m 2 h A t wee M- mass loss g; A- ative samle aea mm 2 ; t- time hou. Fig.1: Samle dimensions fo oosion ate a-ylinde; b-iston; SA-ative sufae Seimens wee immesed in fomation wate utted in nonmetalli glasses. Heating was made in a themostati bath. CO 2 babotage was made with CO 2 ylinde and essue edue. Samles osed to oosion in diffeent onditions had the following aea: Piston: A=620mm 2 ; Cylinde: homium-lated A=640mm 2 ; abonitided A=680mm 2 ; nitided A=620mm 2. Testing onditions to detemine oosion ate wee: - temeatue and 50 0 C; - atmoshei essue with and without CO 2 ; - essue of CO and 5 MPa. Fig.2: Stati oosion devie diagam 1- samle; 2- ative anode; 3- glass with fomation wate; 4- essue ontaine; 5- heating bath; 6- themostat; 7-CO 2 essue gauge; 8- needle valve; 9- heate; 10- tansfome; 11- CO 2 ylinde. In table 2 is esented the oosion ate esults fo oule iston metal sayed with home lated ylinde [4]. Table 1. Coosion ate fo oule iston metal sayed-home lated ylinde Tests onditions Time Mass loss mg Coosion ate g/m 2 h Temeatue o C Pessue CO 2 ba h Piston Cylinde Piston Cylinde babotage babotage babotage babotage

3 Simila esults wee obtained fo oules iston metal sayed- ylinde abonitided and nitided [3]. 2.2 Wea of iston- ylinde oules Wea abasion oess was eseah on a testing mahine designed and omleted fo that uose. In figue 3 is esented inemati diagam of the devie. On vetial od 1 is fixed the samle tye iston 2. Samle tye skit 3 slotted is tighten on iston with a flible able 4 tensioned with weight set 5. Altenative movement of the iston is ovided by ank and onneting-od assembly 6 moved by eleti moto 11. Pistonylinde system is omletely immesed in fomation wate fom tank 9. To maintain in susension sand we have a unhed late 10. wee: µ is dynami fluid visosity Pa.s; v m iston aveage seed m/s; v m =S.n/30 S- iston stoke m; n- double stoke e. min.; f fition oeffiient; N load N; j adial leaane µm. Metal Say -ed Table 1. Piston-skit wea Mateial Wea mg oule Piston Skit Piston Skit 15'30' 45' 60' 15' 30' 45' 60' Metal Chomium Say -ed lated Metal Cabo Say - -ed nitided Nitided Piston seimens esented in figue 4 wee mahined fom eal istons. Fig.3: Cinemati diagam of the devie Fo wea tests it was used fomation wate with 3% sand fom down-hole ums with gain size smalle than 63 µm. Testing onditions wee: - able load 50N; - double stoke e. min. 54; - temeatue 20 0 C; - babotage of CO 2 ; In table 2 ae esented the iston-ylinde wea esults with CO 2 babotage [3]. To fix eimental load was fixed the essue between iston and ylinde in eal onditions fo a um and a ude oil tye [2]: 2290 µ v = f j m N N/m 2 Fig. 4: Piston seimen Cylinde samles esented in figue 5 wee mahined fom eal ylindes. Fig. 5: Cylinde seimen 2.3 Wea laws Analyzing oosion eimental esults with CuveExet ogam was establish a oelation between oosion ate and temeatue: 437

4 d t vo = a b e g/m 2 h wee: a b d ae oeffiients deending of iston () and ylinde () mateials oule and of testing onditions [4]. In figue 6 is esented the vaiation of oosion ate vesus temeatue fo metal sayed iston with homium lated ylinde. Viteza de ooziune g/m2h Fig. 6: Coosion ate vesus temeatue With CO 2 essue was estabilish a oelation as: 2 3 vo = a + b + + d + e 4 g/m 2 h wee a b d e ae oeffiients deending of iston () and ylinde () mateials oule and of testing onditions [4]. In figue 7 is esented the vaiation of oosion ate vesus CO 2 essue fo metal sayed iston with homium lated ylinde. Viteza de ooziune g/m2h Fig. 7: Coosion ate vesus CO 2 essue Analyzing esults fo wea with DataFit ogam was establish the elation: = a x b u + S = = Temeatua gade C S = = Pesiunea CO2 ba wee u is wea mg; x- time min.; a b - oeffiients deending of iston () and ylinde () mateials oule and of testing onditions [4] In figue 8 is esented the vaiation of wea vesus time fo metal sayed iston with homium lated ylinde [4]. Fig.8: Piston-ylinde wea S=139 R 2 = PISTON-CYLINDER DURABILITY To obtain otimum um effiieny the umulate linea wea of iston and ylinde must not ass a etain value: h max j max -j i mm wee: h max is umulate linea wea mm; j max - maximum leaane between iston and ylinde mm; j i - initial leaane mm. h max = h + h mm wee: h - linea iston wea u vm h = 10 3 mm ρ A f vm h linea ylinde wea u v m h = 10 3 mm ρ Af vm u u gavimeti iston and ylinde wea mg; ρ ρ sufae iston ylinde density kg/m 3 ; A f A f fition aea fo iston ylinde m 2 ; A f = π d N l ; A f =π D N (l +C ); d N = D N nominal diamete fo iston ylinde mm; v m - aveage um iston seed C n vm = 30 m/s; v m aveage eimental iston seed C n vm = m/s;

5 h max = u ρ A C effetive iston stoke [1] C = k C λ m; k oveload oeffiient [1] ( H n) k = λ - od sting tension [1] λ= H 2 α m; α - tension oeffiient m/m 2 ; H deth of lunge m; n n double stoke e. min. at uming unit esetive eimental; l iston woking length m; C sufae stoke m. f C n C n 3 u C n mm ρ A C n Relaing u and u and notating a ij b ij - oeffiients fo iston i in oule with ylinde j and a ji b ji - oeffiients fo ylinde j in oule with iston i fo time life x was obtained the following elation: x= π d N l C n b ji ρi h 10 3 max b ij+ C n ρj C + 1 ρi l aji a ij+ ρj C + 1 ρi l To establish j max was used the ondition of minimum sufae effiieny η=065 [5]. Piston-ylinde effiieny it is [4]: η η = = η ηsm ηsf wee η = is stokes aot; η sm =0746 taveling valve effiieny; η sf = standing valve effiieny. Fom um ate leakage elation [5 ]: Q = π d H 4 N jmax ν l wee ν is inemati visosity St. f m 3 /24h Aoding to test ondition fo a oosive and abasive medium initial leaane it is eommended j i =50µm and thus h max =97µm. In table 3 it is esented the time life fo iston-ylinde oule at 20 0 C and 011MPa atial essue of CO 2. Te esults obtained show that the best oule is metal sayed metal land home lated ylinde. Table 3. Duability fo iston-ylinde oule Mateials oule Duabilit R 2 Piston Cylinde y days Metal Chome lated sayed Metal Cabonitided sayed Metal sayed Nitided In ode to onside the temeatue and CO 2 essue influene above the istonylinde duability it was definite the gavimeti wea ind fo the iston i whih wok with ylinde j as: K uij =v uij 10-3 / A. g/m 2 h wee v uij is gavimeti wea ate fo iston i whih wok with ylinde j mg/m 2 h; A. - iston aea at wea tests. In the same way was definite K uji. Obseving that v oij / K uij =m ij =t. and v oji / K uji =m ji =t. wee v oij oji is the oosion ate deending on temeatue and CO 2 essue fo iston i whom wok with ylinde j esetive fo ylinde i whih wok with iston j. It was obtained the oelation between wea ate and oosion ate: v uijuji = v oij oji (t CO2 ) A 10 3 /(m ijji 60) Beause wea ate eesents wea deivative with time the a ij ji oeffiients fom wea law obtained at eimental tests ae: a ij ji = v oij oji (t CO2 ) A 10 3 /(m ijji 60) [mg/min] In VisualFoxPo ogamming language was eated an oiginal omute ogam in ode to evaluate lifetime fo diffeent istonylinde mateial oule and fo diffeent 439

6 woking onditions. In figue 9 is esented the ogam window simulation. Fig. 9: Duability alulus window ogam simulation 4. CONCLUSIONS Exeimental tests establish that wea ise with temeatue. With CO 2 essue the influene above wea is diffeent deending on the CO 2 essue value. Beause at CO 2 essue tests was used only CO 2 gas the CO 2 essue value is the same with atial essue of CO 2. The maximum oosion ate was obtained fo 8 10 ba CO 2 essue when the ondutivity of tested fomation wate was maximum. Comute ogam eated emits evaluation of lifetime fo um iston-ylinde oules in diffeent woking onditions. Lifetime evaluation eo is smalle than 12% and ogam auay was onfimed by industial atie in oil fields. 5. REFERENCES [1] Pete N. Chitu-Militau N Extatia titeiului in omaj u ajini Ed. Tehnia. Buuesti.51-60; [2] Juh A. et al New onetion suke-od um design SPE 2172; [3] Rieanu R.G. Tudo I Reseah egading downhole ums wea whih woks in ude oil wells with high CO 2 atio The Annals of Univesity "Dunaea de Jos" of Galati Fasile VIII Tibology vol. I Galati ; [4] Rieanu R.G Ceetai ivind esteea duabilitatii ulei ilindu-iston din omonenta omelo de tatie Ph.D. thesis Petoleum-Gas Univesity of Ploiesti ; [5] Tudo I. Rieanu R.G Ingineia ooziunii vol. 1 and 2 Ed. Univesitatii din Ploiesti and