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Complete solution for unconventional wells
According to the latest Energy Information Administration data, between 2010 and 2020 the number of horizontal wells in the U.S. increased from 4.4% to 16.9%, and production from unconventional wells in the Permian Basin increased to 75% by 2021, which indicates the high potential of unconventional wells. Despite their great potential, unconventional wells pose a large number of challenges for conventional production methods:
- A rapidly changing well-flow rate; for example, in four months well productivity can drop from 1,749 bopd to 189 bopd;
- High GLR from 600 scf/bbl; and
- High sand content.
At the moment, the main methods of mechanical production for wells with flow rates below 300 bopd are:
- Operation of the ESP unit in Start-Stop mode; and
- Replacement with a sucker-rod pump (SRP) instead of an ESP.
Each of the current technologies has advantages and disadvantages:
It should also be taken into account that according to the analysis when switching from ESP to the sucker-rod pump, the oil flow rate decreases. The dependence is shown in Figure 1.
Figure 1: Comparison of ESP and SRP flow rates
Triol Corporation offers a unique EP01 solution for unconventional wells with flow rates below 240 bopd.
The uniqueness of the EP01 for unconventional wells can be summarized as follows:
1. Continuous operation under minimum flow rate conditions;
2. Operation with a GLR of over 600 scf/bbl; and
3. Working with mechanical particles.
Because the EP01, like the SRP, has a large control range of cycles per minute and plunger stroke length, it is possible to produce less than 10 bopd, unlike the ESP, which has a limitation on motor frequencies.
The presence of the submersible telemetry unit and the algorithm for regulating the number of cycles per minute allows, in contrast to SRP, one to control in real time the intake pressure and automatically maintain it (Figure 2).
Figure 2: Maintaining the intake pressure by regulating the number of cycles
The SRP has low efficiency when operating with a high GLR. As a consequence, gas plugs form in the pump. ESP is less affected by gas but requires the installation of an additional gas separator. The high gas content leads to a reduction in flow and, consequently, overheating of the motor. The EP01 unit is capable of handling a large GLR even without a gas separator, and the system successfully fights gas increases inside the pump.
а)
b)
c)
Figure 3: Example of gas operation without a gas separator
а) dependence of the motor temperature on the intake pressure
b) dynamogram of not filling the pump on the upstroke (Phase I, 3a)
c) dynamogram of the pump's total filling (Phase II, 3a)
In Figure 3a of phase I, you can see how the motor temperature begins to increase and the pressure at the intake decreases, and in Figure 3b, the force on the upstroke decreases. This means that a large amount of gas has collected in the pump, while there is no overheating of the motor because the control system automatically reduces the current as a result of the reduction of the load on the upstroke (Figure 4).
After the pump intake pressure increases by 30 psi (Figure 3a phase II), the operation of the unit stabilizes, which can also be seen in the dynamogram in Figure 3c, and the motor temperature decreases (Figure 3a phase II).
Production in unconventional wells is accompanied by constant sand emissions from the bottom of the well.
For ESP, the presence of a large amount of sand leads to rapid wear of impellers. The use of a standard filter can remove only part of the mechanical particles, and the use of a fine filter at the pump intake can lead to clogging of the filter and the complete absence of flow.
A separate auxiliary module acts as a filter for the SRP, which leads to:
- increased installation time;
- higher installation costs; and
- filter clogging during operation (similar to ESP).
The EP01 design provides a separate intake module (similar to the SRP), which, unlike the SRP, is located on top of the pump, allowing filtration before the mechanical impurities increase to the pump intake. The intake module has an enlarged area to minimize the risk of clogging the filter grid.
Even if the filter grid becomes clogged, the design includes back-up valves that open after the intake grid is completely clogged, allowing the unit to continue to operate without additional measures.
Summary. The EP01 unit is a complete solution for automated production from unconventional wells, while increasing the average operating time of the equipment (MTBF).
