Page 15 - Acoustic Fluid Level Measurements

Applications of Fluid Level Measurement to Pumping Wells 8-1

Petroleum Extension-The University of Texas at Austin
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Applications of Fluid Level Measurements to Pumping Wells

In this chapter:
• Total monitoring of pumping system operation and wellbore fluid and pressure distribution
• Rod-pumped wells
• Well pressure survey
• Correlation of fluid level with dynamometer measurements
• ESP and PCP wells
• Recommended procedures and special considerations for quality control and analysis

Throughout the world, the most commonly used method and cannot displace liquid into the bottom of
to artificially produce oilwells is by sucker rod lift and the tubing at the rate that the formation could
has been since the early times of the industry. Efficient deliver it to the wellbore.
application of all types of well pumping systems re- • The pumping system’s theoretical displacement
quires knowledge of the position of the liquid in relation capacity equals or exceeds the formation produc-
to the intake of the pump. This quantity is defined as tivity, but the pump is operating inefficiently at
the pump submergence, and its determination was the a lower effective displacement rate, which in
primary reason for the early development of acoustic turn limits the liquid inflow from the reservoir.
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fluid level instruments, as discussed in detail in chapter
4. The refinement of this technology and the advent of Experience has shown that the majority of pump-
portable computers have expanded the application of ing wells experience the second situation listed above,
fluid level measurements for optimization of the total where the low pump volumetric efficiency is the con-
pumping system through detailed analysis of the pres- trolling factor.
sure and fluid distribution in the well. The “First Law of Pumping” may be stated as: In a
Most operators want wells to produce at or near well that is artificially lifted by pumping, the reservoir
their capacity. When a well is producing at a maximum cannot produce more liquid into the wellbore than the
rate (defined as its potential), the producing bottomhole pump can displace from the wellbore into the tubing.
pressure (PBHP) will be very low compared to the static Fluid production (oil, water, and gas) from the forma-
bottomhole pressure (SBHP), which is equivalent to tion is controlled by the pump displacement, which means
the static reservoir pressure. If the PBHP is larger than that at stabilized conditions, the formation produces fluid
15% of the static reservoir pressure, then the current at the rate that fluid is removed from the wellbore by the
production may be significantly lower than what the pumping system. Depending on formation productivity,
formation is able to provide, indicating the reservoir is the PBHP will stabilize at a specific level and remain
not being produced efficiently. constant as long as the pump liquid displacement rate
Inefficient reservoir production by pumping may remains constant. In the annulus of the wellbore, the
be caused by one of two reasons: vertical distribution of produced fluids is controlled by
• The pumping system is operating efficiently at gravity, with gas overlaying a column of fluid generally
its maximum capacity, but is under-designed consisting of a mixture of gas and liquid. For a given

For distribution by Petroleum Extension-The University of Texas at Austin
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