The use of an innovative wireless bottom hole pressure/temperature telemetry acquisition system in artificial lift operations can dramatically improve efficiency and optimize fluid producing rates in those wells. The tool is installed into the producing well in the vicinity of the perforations, measuring and transmitting the producing bottom hole pressures and temperatures to the surface for instantaneous control of the surface pumping motor speed. This insures the lowest possible fluid level back pressures, thus allowing for the highest possible fluid entry into the wellbore from that reservoir's capacity. Operating costs per barrel are lowered since the maximum oil production can now be realized from existing wells.
The telemetry tool is deployed with standard slickline equipment and is installed inside a well in a manner similar to ordinary pressure recorder tools. Several unique advantages of the tool are:
no moving parts;
no wireline to the surface;
real time measurement of bottom hole data; and
slickline retrievable.
Future versions of the acquisition system tool will improve operating efficiency in the following ways:
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Temperature monitoring and control of perforation scaling, tubular waxing, and tubular hydrating plugs.
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Provide data necessary to create diagnostically predictive IPR curves through monitoring of reservoir in-flow rates.
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Enabling early warning of water encroachment or lensing through fluid resistivity monitoring.
A field demonstration of the application of the bottom hole pressure data, as received from Real Time Diagnostics' wireless pressure transmission system, improved the efficiency of PanCanadian Petroleum Limited's 8A-19-38-01-W4m well in the North Bodo field of northeast Alberta, Canada. An illustration of servicing a typical North Bodo slant well on a pad of wells is shown in Fig. 1. The Telemetry Acquisition Tool (PAT) device, developed by Real Time Diagnostics (RTD), was installed in the production tubing below the producing zone perforations, where it was able to measure and accurately transmit bottom hole production pressures and temperatures of the well's producing horizon to the surface. The real time pressure data was relayed into a voltage loop and a surface computer which contained software designed to output an analog process signal. This signal was then sent to the Wermac Electric Limited's Variable Frequency Drive (VFD), which controls the speed and torque of the electric motor powering the bottom hole progressive cavity pump (PCP) system. PanCanadian was able to both increase the oil production and decrease the lifting costs per barrel by utilizing the actual bottom hole pressure response of the reservoir fluids flowing into the wellbore to optimize the daily rate of production.
Basic theory of signal transmission through electromagnetic wave propagation is not unique or novel; in fact, it has been around for many years. A typical oil field telemetry system includes a downhole frequency transmitter, which contains measurement sensors and a receiver located at the surface. A specially modulated electromagnetic frequency signal, representative of the measurements performed by the sensors located in the downhole transmitter, is injected into the formation where it propagates upward to the surface along the outside of the casing string, essentially creating a two wire path for the current flow to follow. By example, the casing represents one wire and the earth represents the return path or second wire. The electric signal is collected at the surface receiver system by measuring a voltage potential between the surface wellhead and a remote ground reference. The voltage potential is then amplified significantly and filtered to eliminate or reduce other electrical noises, which can be man-made or naturally occurring.
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