Page 14 - Acoustic Fluid Level Measurements

Applied Well Testing (Pressure Transient) 7-1

Petroleum Extension-The University of Texas at Austin

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Applied Well Testing for Pressure Transient Data Acquisition

In this chapter:
• Automatic acoustic determination of formation pressure
• Factors that influence pressure transient testing
• Programmed fluid level surveys
• Data acquisition and processing background
• Recommended procedures for optimum quality of recorded data
• Examples of well surveys from the field

Proper reservoir management and production optimi- are produced through artificial lift pumping systems.
zation require up-to-date information about forma- Therefore, it is necessary to monitor and analyze the
tion pressure, permeability, and wellbore skin factor. performance of these systems. The principal tools that
Pressure transient tests using wireline-conveyed or are used in the field to determine indicators that influence
permanently installed surface readout pressure gauges production rates—such as reservoir pressure, formation
are commonly run into flowing wells. However, the permeability, productivity index, pump efficiency, and
presence of artificial lift equipment complicates and skin factor—include:
often precludes the use of wireline-conveyed devices. • Flowing BHP surveys
Thus, conventional pressure transient tests are seldom • Pressure buildup tests
performed in these wells. The result is poor reservoir • Pressure drawdown tests
and production management.
Since the 1980s , the oil and gas industry has relied • Inflow performance analyses
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on programmable equipment to calculate bottomhole These techniques are widely used in flowing wells and
pressure (BHP) from surface pressure and acoustically some gas lift wells, where the pressure information is
measured liquid level data in pumping wells. Over the easily obtained from wireline-conveyed BHP recorders.
years, advances in electronics, computer software, and In rod-pumped wells, the presence of sucker rods
transducer technology have vastly improved the data essentially precludes the practical, routine, and direct
quality and usability of this equipment. In fact, because measurement of BHP, thus eliminating the single most
the equipment provides real-time data with the quality important parameter for well analysis. Permanent in-
that is necessary for pressure transient analysis, this stallation of surface-indicating BHP gauges is not yet
method is considered to be a reliable and cost-effective cost-effective for wells with low production rates. As
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way to determine BHP. discussed in chapter 6, one solution to this problem
From a management perspective, the industry’s is to calculate the BHP from the casinghead pressure
primary objective is to achieve maximum production measurement and then determine the annular fluid head
efficiency with minimum engineering and technical from echometric surveys that yield the depth of the gas/
labor. The majority of onshore oilwells in the U.S. liquid interface and the gradient of the annular fluids .
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