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European Journal of Applied Sciences – Vol. 10, No. 5
Publication Date: October 25, 2022
DOI:10.14738/aivp.105.12881. Gareyev, A. A. (2022). Method of Periodic Operation Mode Forecasting. European Journal of Applied Sciences, 10(5). 149-156.
Services for Science and Education – United Kingdom
Method of Periodic Operation Mode Forecasting
А. А. Gareyev
Due to natural depletion of developed or new fields with poor reservoir features placed under
production, the number of wells equipped with electric centrifugal pumps (ESPs) running in
the periodic operation mode, is growing. Similar properties are intrinsic to hard-to-recover
fields, which actually the Bazhenov (shale) suites are.
Obviously, oil producers are facing the problem of providing upstream exploration and
production from low-permeable (shale) reservoirs, characterized by low flowrate (less than 15
m3/d) at dynamic fluid levels over 2,000 m. Exploitation of such fields using low-capacity ESPs
leads to MTBF drop of the latter. ESP failures occur due to salt deposition in the centrifugal
pump chamber (further referred to as “R-0”). The author came up with the solution of the first
problem [1] about 15 years ago, but - one might wonder why - it was ignored by the experts.
This paper is aimed at the search of the ways of improving the efficiency of ESP’s control
running in the auto-reclosing mode, in order to simplify the task for field production engineers,
dealing with routine operations.
Figure 1. NIZHNESORTYMSKNEFT NGDU well stock running on an intermittent basis in 2022.
Oil fields are numerated as 1,2 ... 25. The majority of wells (478) of the ESP stock running in
periodic mode, refer to the North Labatyugansk oil field.
Figure 2 shows an example of operation on the well No. 3348 of the North Labatyugansk oil
field in the periodic mode.
The well is equipped with ESP 5-30-2200 at the depth of 2,368 m and is running with a flowrate
of about 8 m3/d at the dynamic fluid level of 1,585 m. The ESP’s suction pressure changes from
78 MPa to 82 MPa. Producing water cut amounts to 36%.
178
11
55
149
109
12 9 1
56
127
11 8 4 12 21
478
2
51
2 3 5 23 18 29
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Well stock running on an intermittent basis
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 5, October-2022
Services for Science and Education – United Kingdom
Figure 2. A copy of the “Stock Progress” report related to the well No. 33548 of the North
Labatyugansk oil field. The ESP unit suction pressure changes from 78 atm to 82 atm. Rundown
time is 30 minutes, accumulation time – 2 hours.
Fluid rundown time is 30 minutes, accumulation time – 2 hours. In general, the unit runs for 4.8
hours a day and stays in the accumulation mode for 19.2 hours.
The previous ESP 5-20-2350 with 538 days of TBF was lifted after its failure due to “R=0” of the
“cable-motor” system. Operation parameters: flowrate – 13 m3/d at the dynamic fluid level of
2,145 m; depth of the ESP installation – 2,372 m. Upon disassembly, it was discovered that the
decrease in the ESP’s electric resistance took place due to the cable-extension failure, which is
evidence of the pump’s temperature rise over 230 °С (working temperature of the cable
extension and its thermal-resistant flat portion). The ESPs of the intermittently running well
stock are equipped with thermomanometric sensors (ТМS). The data is transferred to the
control station. Figure 3 shows the graph of electric current variance, centrifugal pump’s
suction pressure variation and corresponding performance factors (cos
).
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Gareyev, A. A. (2022). Method of Periodic Operation Mode Forecasting. European Journal of Applied Sciences, 10(5). 149-156.
URL: http://dx.doi.org/10.14738/aivp.105.12881
Figure 3. Change of well operation rates during periodic operation. At present, a process
engineer is unable to analyze and make effective decisions on operation of centrifugal pumps in
order to gain the best economic outcome.
Currently there is no adequate theoretical basis for designing a periodic mode of well operation.
Therefore, the solution of the set task usually proceeds from the fact of an ESP’s failure, e.g.,
using the operational data of the previous ESP, which failed due to “R-0” after 538 days of
running (TBF). The gained TBF value is the result of combined operation, i.e., with switch-over
from the periodic mode (240 days) to continuous mode (300 days), which proves that the pump
was affected by high temperature while running. The working temperature of the cable
extension tраб = 230 °С. The ESP unit failed due to the decrease of electric resistance of the cable
extension isolation, thus, the temperature inside the running pump exceeded the working
temperature of the cable extension by 50 °С and even more. The operation parameters of the
ESP 5-20-2350 unit are as follows: at AC frequency of
47.5 Hz, the fluid flowrate Qж = 13
-16 m3/d, the dynamic fluid level Ндин – 2,105 m. Producing water cut amounted to 25%.
Electric current
variance
Pump’s suction
pressure
variation Рпр
Change of cos (f)
(performance factor)
Accumulation tнак
Pumping-out tотк
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 5, October-2022
Services for Science and Education – United Kingdom
Figure 3. The ESP unit failed due to “R-0” of the cable line (cable extension) with the working
temperature of 2300С. The cable extension failure shows that the temperature of the pump
section exceeded 2300С. In fact, the pump temperature exceeded 3000С (the temperature of
leakage current spikes in the cable extension).
For the purpose of the ESP unit design, let’s first determine the ultimate dynamic head, at which
the pump’s temperature will rise up to 230 °С.
The parameters of the ESP unit and the reservoir required for this calculation, are shown in
Table 1.