LOCATION: PERMIAN BASIN, NEW MEXICO TIMING: EARLY JUNE 2015 – END MAY
- Major operator suffered a (conventional) ESP failure within 3 weeks of installation due to sand erosion / pump plugged with frac sand.
- The 288 stage ESP was replaced by a 40 stage V-Pump™ and a similar motor.
- The V-Pump operated trouble-free for one year.
- V-Pump continued to operate through extreme gas slug conditions
- Pump was eventually pulled due to ESP cable failure.
|TUBING||2 ⅞ “|
|PUMP INTAKE DEPTH||4,163ft MD; 4,163ft TVD|
|SENSOR||4,213ft MD; 4,213ft TVD|
|KICK OFF POINT (KOP)||4,900ft|
|HORIZONTAL SECTION||4,000ft long|
|TOTAL DEPTH||9,601ft MD; 4,831ft TVD|
|WELL TYPE||Unconventional well, Fractured with 100mesh sand|
KEY SUCCESS FACTORS (ATTRIBUTED TO THE V-PUMP):
- The V-Pump quickly produced 60% more fluid than the conventional ESP
- The V-Pump survived sustained high sand production for one year.
- The V-Pump was occasionally shut down for operational reasons; the V-Pump always restarted; there was no pump plugging due to sand ‘fall-back’.
- No Gas-Locking: The V-Pump continued reliably pumping throughout these periodic gas slugs. The ‘Gas Slug’ regime persisted for more than 10 months of the installed life of the pump. (Conventional ESPs gas-lock repeatedly, typically several times per day in this type of well and typically need to be restarted on each occasion after 1 – 2 hours lost production.)
WHY WAS THE V-PUMP SELECTED?
The V-Pump was selected by the operator due to its sand resistance and gas handling capabilities.
WHAT HAS BEEN THE EXPERIENCE?
The previous ‘conventional, centrifugal ESP’ failed in just 3 weeks. The V-Pump has produced at higher rate & survived gas and sand slugging for a year (recovered due to cable failure). The V-Pump did not fail but will need a full service / rebuild before the next installation.
ARE THERE ANY LEARNINGS FROM THIS?
The V-Pump has operated successfully in a high sand, high gas well for a year. High sand or gas will often fail a conventional ESP very quickly. The V-Pump will withstand the 2 main ESP killers.
V-PUMP WELL COMPLETION
STEADY-STATE OPERATION OR TRANSIENT OPERATION? (GAS / LIQUID SLUGGING)
Most unconventional wells operate in a continuously transient flow pattern for much of their life. In simple terms, the flow is constantly changing through any 2 or more of the following regimes: liquid; bubble flow; dispersed mist; wet gas. In many cases, the transition appears to be directly liquid to wet gas then back to liquid.
This has several important outcomes as follows:
- Modelling the well behavior based on daily production figures is often unrepresentative. The pump system is required to deal with a much wider, more extreme range of fluid conditions from liquid through to wet gas.
- Conventional ESPs will usually be specified to deal with production conditions derived from daily production data. These conditions might only prevail for 1% of the life of the completion. 99% of pump operation must deal with the constantly transient conditions of gas, followed by liquid slug, followed by gas. The V-Pump thrives in these conditions; conventional ESPs may struggle and gas-lock.
The V-Pump does not require a gas separator. Figure 2 shows the onset of gas / liquid slugging in the well.
The illustration shows the onset of gas / liquid slugging from the horizontal part of the well. Slugging is evident when GVF rises above 20% (based on daily production figures).
The slugging is evident as Pump Intake Pressure (PIP) variations reflecting the fluid density variation in the vertical part of the well, between the horizontal portion and the pump intake.
Figure 3 illustrates the progressive development of PIP swing due to ever larger, more segregated slugs from the horizontal section of the well. Note that the motor load (Amps) respond in the opposite direction to PIP
Figure 4 illustrates the fully developed cyclic gas / liquid slugging from the horizontal section. Figure 4 represents just one day of operation at a steady, long term 58Hz.
At 56Hz, motor cooling was inadequate and the pump would trip on each cycle due to high motor temperature. At speeds higher then 58Hz, motor temperature cycles were progressively reduced.
Steady, cyclic operation similar to figure 4 continued for many months of operation. After a time, an adjacent well treatment occurred, increasing the liquid production rate of the well (water) and reducing the gas / liquid slug cycling.
The cycling appears to demonstrate the following:
HIGH GVF (GAS) = HIGHER PIP = LOWER MOTOR LOAD (AMPS)
LOW GVF (LIQUID) = LOWER PIP = HIGHER MOTOR LOAD (AMPS)
GVF = Gas Vapour fraction (at pump intake)
PIP = Pump Intake pressure