Wells – Processes – With indicating – testing – measuring or locating
Patent
1991-09-30
1993-05-25
Melius, Terry Lee
Wells
Processes
With indicating, testing, measuring or locating
175 48, E21B 4700
Patent
active
052131599
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to the sensing of fluid parameters in wells, for example oil wells.
Oil wells usually have an outer casing down which is lowered a production string for the passage to the surface of the oil produced by the well. In certain wells it is necessary to have an artifical lift system to bring oil to the surface usually up the production tubing, either because of the lack of sufficient natural reservoir pressure to produce the well or to enhance production from a well that produces under natural pressure. A common system of artificial lift is to place an electrical submersible, or submergible, pump (ESP) down the well casing on the end of the production tubing to pump fluid from the casing up the production tubing. The installation of an ESP on the end of the production tubing eliminates the possibility of carrying out logging or other operations in the well below the production tubing with tools, unless a by-pass system is used to enable tools to be passed through the production tubing and into pump by-pass tubing by means of a Y-crossover sub, known as a Y-tool. Below the Y-tool there thus are two strings:
1) A pump string which produces the well, discharging fluid through the Y-tool into the production tubing to surface.
2) A by-pass tubing string which enables tools from the production tubing to go down past the pump and enter the well below the pump for logging or other operations.
When operating the well it is useful to know a parameter of fluid at the intake to the pump, pressure being the most common as it gives an idea of the fluid level in the well; and it is common practice to determine the value of the intake pressure by a sensor located at the bottom of the pump/motor assembly, power to the sensor and the signal from the sensor being carried by an electrical cable running to the surface, which may be the power cable. Other parameters such as temperature, flow or density may be similarly sensed.
It would also be useful to know a corresponding parameter on the discharge side of the pump, for example the pressure in order to give an indication of the efficiency of the pump.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a method of monitoring parameters of fluid being pumped from a well, for example an oil well, comprising sensing a fluid parameter on the intake side of the pump, characterized in that a corresponding fluid parameter is also sensed on the discharge side of the pump or in the production string. It would be very expensive to run a pressure discharge sensor down the well on the end of a separate cable and the intake and output discharge parameters are preferably transmitted to the surface by the same route. More preferably signals indicative of the intake and discharge parameters are generated at a common location.
According to a second aspect of the present invention there is provided sensing apparatus for use with a downhole pump in a well, for example, an oil well, comprising a sensor arranged to sense a fluid parameter, for example pressure or temperature, of fluid in the annulus, i.e. on the intake side of the pump, characterized in that a further sensor is arranged to sense a corresponding parameter of fluid on the discharge side of the pump or in the production string.
In one embodiment of the present invention the sensing apparatus may be mounted on the Y-tool, which is preferably provided with a further arm to accommodate the sensing apparatus and which thus takes on the general form of a letter "H", such a modified Y-tool subsequently being referred to as an H-tool. The sensing apparatus is thus afforded a protected environment and an extended working life. Moreover, the positioning of the sensor on a modified Y-tool, and preferably on an H-tool, allows not only the parameters of fluid in the annulus to be sensed but additionally such parameters of fluid entering the tool from the by-pass string or from the pump discharge also to be sensed directly.
Although the electrical conne
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The Oil and Gas Journal, vol. 74, No. 9, Mar. 1, 1976, pp. 114, 118.
Melius Terry Lee
Reynolds Florence U.
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