Fully Automated Fluid Level Measurement Tool

Abstract

The fully automated fluid level measurement tool was developed recently. The paper describes the technical features of the tool and shows via case study the results of the field tests on various Electrical Submersible Pumps -ESPs and sucker rod pumps -SRP, running with and without Variable Speed Drive -VSD.The unique feature of this system is its fully automated and purely electronic functioning. The measuring device is enclosed, mounted on the casing valve, has a pressure rating of 350 bar (5000psi) and works with zero emissions on the environment (no outlet of casing gas).Compared with a conventional downhole pressure sensor, mounted on an ESP, the system is insensitive to high well fluid temperatures and simple to maintain due to its easy access on surface location. It additionally has a sampling rate of down to one measurement per minute. The measured fluid level data can be transmitted via SCADA system.The measurement tool enables to run a pump in a more safe way. It can be used to avoid pump off conditions and the resulting equipment damage. It can also be used to control a VSD to keep the fluid level in a well at a specific depth to avoid bottomhole flow conditions below the bubble point pressure. Due to the availability of online fluid level data, all kind of pumps (e.g. ESP, Sucker Rod, PCP, Jet Pump) can be operated safely at more aggressive production rates in order to mobilize more oil.Furthermore the vision and corresponding thoughts of acoustic well diagnosis, also a feature of the tool which is currently under investigation, are presented. IntroductionWhereas in free flowing wells it is relatively easy to get downhole pressure measurements, there are significant difficulties in wells which are on artificial lift. Compared to gas wells, in which memory gauges can be placed via slickline or wireline technology downhole through the tubing, this is not possible in sucker rod pumped oil wells because of the moving rods within the tubing.However, to measure bottomhole pressure also at artificially lifted wells is of special interest for both reservoir and production engineers. Conventionally the reservoir pressure and the well flowing pressure are calculated from the fluid level, which in turn is measured indirectly via acoustic method. An acoustic event is produced at the opened casing valve. Depending on the height of the available casing gas pressure, this event can be produced in different ways. If there are several bars of casing gas pressure available, the casing can be vented shortly to the atmosphere and closed immediately thereafter. So gas comes to flow at first. This flow is suddenly stopped, by closing a valve as shown in Fig. 1, which produces noise. If there is not enough casing gas pressure available, an external pressure source like a nitrogen gas bottle is connected to the casing valve. A short flow of pressured nitrogen is established into the casing and stopped suddenly, which produces noise once again.The acoustic wave propagates down the annulus and is reflected at every obstacle lik...

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