Subsea Multiphase Pumping System X Gas Lift: An Exergo-Economic Comparison
Subsea Multiphase Pumping System X Gas Lift: An Exergo-Economic Comparison
Subsea Multiphase Pumping System X Gas Lift: An Exergo-Economic Comparison
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Gas
Oil
GL SMPS-00 SMPS-60
Year 2000 2001 2010 2020 2000 2001 2010 2020 2000 2001 2010 2020
P (bar_g) 68 67.3 70.7 74.1 51.9 62 53 43.7 29 35 29.5 30
V (m3/h) 180 187.5 165.9 167.1 146.5 173.9 128.3 109.6 347.3 438.1 276.1 171.8
FVG 0.65 0.68 0.59 0.59 0.57 0.66 0.47 0.38 0.73 0.79 0.65 0.49
Vgl (Sm3/h) 4167 1667 4167 5833 - - - - - - - -
∆P (bar) - - - - 13.6 2.5 18.8 37 60 60 60 60
W (kW) - - - - 83.1 33.5 99.1 174.3 645.1 822 519.1 346
conditions for the three cases. All these petroleum processing. Which means that
values refer to the production line position maximum or minimum rotation, power and
where the SMPS will be installed. flow rate were ignored. For all the simulations,
some parameters were considered fixed:
2200 - Platform feed pressure: 21.6 barg;
2000 - Gas pressure at platform outlet: 172.6 barg;
SBMS - Oil pressure at platform outlet: 67.6 barg;
Oil flow rate (Sm3/d)
1800
1600
- Well outlet flow’s specific cost of: 1.0 $/kWh.
GL
1400
The specific costs were calculated for the
1200
years of 2000, 2001, 2010 and 2020. These
1000
years were chosen because the oil is
800 considered the main petroleum product and,
600 as shown in fig. 4, the oil production has two
2000 2005 2010 2015 2020 distinct tendencies: one, between 2000 and
Year
2010, where the production is kept almost
Figure 4: Volumetric oil flow: GL e SMPS-60 constant, and the other, between 2010 and
(BARUZZI et al. [1]). 2020, where there is a linear reduction in the
oil flow. The year of 2001 was simulated
Production data because it is predicted a sudden increase in
Well production data with the use of artificial GVF in the first years which differs from the
lift methods were reported by Baruzzi et al. tendency of continuous decrease of the
[1]. In the report the 7-MRL-72D-RJS well following years. With this increase the
operating with SMPS or GL was simulated. multiphase pump have to deal with a higher
SMPS discharge conditions and absorbed volumetric flow rate and, in the GL case, there
power were calculated by using a is a lower necessity of lift gas. In this way, the
thermodynamic model for twin-screw behavior of the systems suffers a
multiphase pumps developed recently considerable change, which must be taken
(NAKASHIMA [8] or NAKASHIMA, OLIVEIRA into account in the comparisons.
and CAETANO [9]). Geometric parameters of
SBMS-500 were used for this purpose. SMPS Results: Heat and electricity
electrical motor efficiency was set to 0.8 Table 4 shows the total energy (heat and
during calculations. This low value is due to electricity) consumed in each case. These
the canned conception adopted for subsea results show that heat consumption with the
operation. The GL compressor adiabatic GL is slightly higher. This is due to the higher
efficiency was taken as 0.75. Heat exchange gas flow rate, a consequence of the lift gas
between ducts and environment was not recirculation. The difference is somewhat
considered, nor was the electricity lower in 2001, because there is a decrease in
transmission efficiency of the SMPS energy the necessity of lift gas, and rise a little again
cable. In this paper no operational limits were in the following years. The heat consumption
considered for any equipment involved in the with the SMPS-60, which should be the
Table 4: SMPS & GL – Heat and electricity consumption.
SMPS-00 GL SMPS-60
Year Electricity Heat Electricity Heat Electricity Heat
(kW) (kW) (kW) (kW) (kW) (kW)
2000 908.9 1330.3 1302.8 1581.4 2139.2 1170.6
2001 1154.1 1402.5 1319 1510.8 2900.1 1025.3
2010 779.3 1591.7 1173.5 1856.4 1693.1 1562.8
2020 551.9 1939.2 1066.6 2276.4 946.6 2038.3
highest values due to the high oil and gas flow instead of the GL. With the GL, part of the
rates, have a reduction in the first years owing produced gas will be burned to generate
to the higher shaft speed and friction power electricity that will be used to compress the
inside the pump. In 2020 the volumetric flow gas again. The compressed gas is, then, re-
decreases with the consequent reduction in injected downhole in the well in order to
the shaft speed and friction power and the reduce the specific weight of the petroleum. In
heat consumption raises. this case, besides the losses caused by
successive conversions of energy, part of the
The electricity consumption of the GL is driven gas is being processed (separated and
mainly by the compressors consumption, compressed) in a redundant way since this
which is large and approximately constant due gas, after previous processing, is re-
to the lift gas. Despite its variation, the compressed and mixed again with petroleum.
electric power of the pumps is a small part of Related to this aspect, the SMPS-00 has an
total power and its influence is not significant. advantage because has no material (gas)
The electricity consumption of the SMPS goes
along with the gas volumetric flow, which Feed
explains, in both cases, the initial increase 1.008
followed by a reduction of the consumed 1.007
electricity. With the SMPS-60, however, the
Specific cost ($/kWh)
SMPS-00
1.006
SMPS-60
electricity consumption is much higher. In this 1.005 GL
case, there is a considerable increase in the 1.004
mass flow of liquid and gas owing to the 1.003
reduction in the well head pressure. The 1.002
increase in the volumetric flow, however, is 1.001
much higher due to gas expansion. The large 1
2000 2005 2010 2015 2020
volumetric flow, together with the elevated Year
differential pressure, causes a higher power
consumption as seen in table 4. Figure 5: SMPS x GL – feed specific costs.
SMPS-00
1.0120
SMPS-00 cases, the resulting specific costs SMPS-60
show that the SMPS-00 allows lower feed and 1.0100 GL