Thedownhole subsystem is composed of the Concentric Tubing String (CTS), themodified jet pump with a flow diverter and a down nozzle, etc.
as shown in Fig.2. Inprinciple, the working fluid, i.e.
, water, is boosted by the plunger pump onthe surface, injected into the downhole jet pump through the annulus of theCTS, and then divided into two parts by the flow diverter, as shown in Fig. 2.The jet pump nozzles are used to convert the high pressure head of the workingfluid into the high velocity head.
One part of the working fluid flows throughthe down nozzle to impact the coal particles, form the coal particles carrierfluid. The high velocity of the carrier fluid will accelerate to stir up thecoal particles at the bottom of the wellbore and carry them upwards to thethroat of the jet pump via the suction chamber. The other part of the workingfluid flows through the up nozzle of the pump, generates high velocity andlowers the pressure at the bottomhole to suck the carrier fluid together with thecoal particles into the pump. Then, the above mentioned fluid–solid stream andthe power fluid are mixed in the throat of the jet pump and enhanced pressurein the diffuser, thus, lifted upwards to the surface via the inner tubingstring. Return fluids are routed to a gas/water/solids separation tank. Any gasreturns are routed to the recovery facility.
The fluids in the separation tankare filtered and to be recirculated to the fluid pumps. Case1 Description of Problem New kudupump 76K1200 was installed in well on 11th May 2015 with pumpsetting depth at 928m below all perforations and ran continuously till 9thJune , 2015 despite increasing torque up to 115% limit.Whilestarting the pump at 100 RPM, the water level was 18m and the torque was 11.3%.On 8th June 2015, the water level had gone up to 412m, while torquehad gone up to 54.2%, The TDS of water was 2250 ppm while temperature of wateron surface was found to be 53 oC.
No sand production was reportedduring entire period. Inference drawn out Thetorque rise was seen suddenly during start-up of the well it may be due toelastomer swelling or stator choked with sand. As sand production was notreported so it can be ruined out. The temperature of surface water was noted 53o C so the elastomer swelling is possible due to high temperature. Recommendations:- Ø Useunder sized rotor.
Ø Changethe stator. Case 2 Description of Problem The100 TP 1200 PCP was started after work over on 1st June, 2015 withinitial torque 32% and water flow rate 14 lpm. The variation in current andtorque values started from the next day and current variation from 25 to 31A,while torque variation from 36 to 54% due to stick slip effect. Initially, sandproduction of around 1 kg/day was observed in this well for two days, but afterthat the sand production ceased. The pump ran continuously till 2ndOctober, 2015 with RPM ramped up to 140, while water level staying around 700m.
There were no major changes in current and torque values.On thewell site visit on 2nd October, 2015, no water flow was observedwith torque variation between 12-45% and current variation between 14 and 16A.The water level was recorded to be 679m. The PCP was stopped and again startedon the next day, while also ramping up the RPM till 300. The Current variedfrom 21 to 28A, while the torque varied from 15-40%.
Water production was notobserved on the surface. Inference Drawn Out Thepump was running normally from 1st June till 1st October.Since the torque variation observed during the site visit on 2ndOctober was low and no water production was reported, this could be due totubing puncture in the tubing string. Uncentralized rod string could be a rootcause for the Tubing Puncture. No water production was observed because as weproduce water through the tubing string, the water being produced falls backinto the annulus due to the tubing puncture. Recommendations Ø Workover job in order to change the tubing Ø Centralizerscould be inserted in the rod string in order to minimize tubing- sucker rodcontact.
Case 3 Description of Problem Thewell was completed with new 70K900 KUDU pump on 26th April, 2015with pump intake depth at 352m and run till 19th May, 2015. Afterthat it was started on 10th June, 2015 by self-flow.Beforeroutine start up on 16th July, 2015 water level was 284m at 470 psi.
When the PCP was started at 11:50 hours at 100 RPM without opening the tubingvalve, the torque was found to be 9.8%, while current was 13.4A.
the torqueincrease was not observed through the tubing valve was not opened. At12:15 hours, the RPM was ramped up to 150 with closed tubing valve and observedfor 10 minutes but the torque was only 10.8% at 13.
6A. at 12:20 hours, the RPMwas ramped up further to 200 and observed for 10 minutes. But no increase intorque was observed- the torque was 9.3% at current of 13.
4A. Interference Drawn Out Fromthe above case it can be interpreted as the torque observed was very less andthere was a negligible rise in the torque values on ramping up the RPM. Thiscould be a reason of sucker rod unscrewing or tubing unscrewing. The unscrewingof sucker rod or tubing was the main reason for low torque values at high RPM. RecommendationsØ Callfor a Work over job.