GB2137963A - Liquid Sampler for Oil Well - Google Patents

Abstract

A sampler for oil wells has an elongate sampling vessel which has valves spring-biassed toward the closed position but held open as the sampler is inserted into the well. An associated device monitors temperature and pressure and relays these to a surface station. When the monitored conditions correspond to those selected for the taking of the sample a signal is sent to a release mechanism which releases the valves and traps a sample in the sampling vessel, and sends a confirmatory signal to the surface station.

Description

SPECIFICATION Well Sampler This invention relates to a sampling apparatus for sampling fluid from oil wells.

One widely used method of sampling oil well fluid involves the use of an elongate sampling tube which has spring-loaded, gas and liquid tight valves at each end. As the tube is lowered into the well, fluid flows through the tube. When the spring-load is released, the valves snap shut trapping the sample in the tube. Release of the spring-loaded valves is effected by provision of a clockwork timing mechanism adapted to release the spring after a period set on the mechanism before the sampler is lowered into the well. It is to be noted, therefore, that in this traditional method, sampling is time-dependent and once the sampler is lowered into the well there is no human control over the release of the snap-shut valves.

Disadvantages of the known system are that the sample may be taken at the wrong depth if there have been operational difficulties which have delayed the lowering of the sampler, or it may be taken while the well is in a state of unstable flow, and also, well conditions such as reservoir temperature and pressure may not be known with sufficient accuracy to permit optimal interpretation of the analysis of the samples taken. In addition, it cannot be detected at surface whether the valves have successfully closed: they may, for example jam in the open or part-open position.

An object of the present invention is to obviate or mitigate one or more of the aforesaid disadvantages.

According to the present invention there is provided a well sampler including a surfacelocated control station and a down-hoie elongate tubular sampling vessel having electrically operable valve means for entrapping a fluid sample therein, means for detecting closure of the valve means and transmitting a confirmatory signal to the surface station.

Further according to the present invention, there is provided a well sampler including a surface located control station, a down-hole elongate tubular assembly insertible endwise into a well and electrical cable for receiving and transmitting power and signals between the control station and the down-hole assembly; the assembly including; a monitoring probe responsive at least to temperature and pressure and electronic circuitry for transmitting corresponding signals from the probe to the surface station; a sampling vessel having electrically operable valve means for entrapping a fluid sample therein; and electronic control circuitry for selectively switching power from the probe circuitry to the valve means in response to a surface-initiated signal and including means for detecting successful operation of the valve means and transmitting a confirmatory signal to the surface station.

There are several means for detecting closure of the valves. The most preferred is an electromechanical system in which the valves are actuated by an electric motor and a switch is provided in the power supply to the motor, the switch being held in one position by the open valves and is movable to the other position when the valves close, movement of the switch being indicative of valve closure.

Preferably the valve means are spring-loaded snap-shut valves held in an open position by a retaining pin and releasable by removal of the pin.

In its most preferred embodiment the motor drive shaft, which passes through a reduction gearbox to produce a speed of rotation of about one revolution in 20 seconds, terminates in a conical cam having an axial slot therein. A valve actuator in the form of an elongate finger is spring-biassed to bear on the sloping face of the cam so that on rotation the finger engages in the slot. The actuator is operatively connected to the retaining pin which is thus moved to its release position enabling the valves to snap shut. Preferably, the side walls and floor of the slot are coated in electrically insulating material and is thus able to act as the switch referred to above.

The surface control station preferably includes data and event-logging apparatus, power supply for the sampler and switchgear for operating the sampler from the surface.

The most preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawings of which: Figure 1 is a schematic drawing of the overall layout of a well sampler in accordance with this invention; and Figure 2 is a sketch of the coupling and interactive switch arrangement of the sampler.

Figure 3A is a true section on line A-A shown in Figure 2 and Figure 3B is the same drawing after rotation of the motor.

Figure 4A is a true section on line B-B shown in Figure 2 and Figure 4B is the same after release of the valves.

Figure 5 is a circuit diagram of a power switching circuit for diverting power from the probe to the sampler.

Figure 1 of the drawings is a schematic illustration of a mid-section of a sampler of this invention. A pressure/temperature probe 1 and a sampling vessel 2 are elongate tubular structures and only the adjacent ends are shown: they are joined by a coupling barrel 3 shown in section.

Within the coupling barrel there is located an electric motor 4 of the shaft 5 of which terminates at one end in a coupling 6 and an interactive switch arrangement 7 which is described in detail later.

The sampling vessel 2 has, proximate the end shown, a number of valve ports 8 and there are similar ports near the opposite end not shown in the drawing. Valve closure shields (not shown) have strong spring bias to the closed position.

Within the sensing probe 1 there are located, and indicated in broken lines in Figure 1, a sensor 9, a first electronic circuit 10 which operates the sensor 9 and a second circuit 11 which is shown in detail in Figure 5 and which will be described later.

Referring now to Figures 2, 3A, 3B, 4A and 4B, an electric motor 4 is insulated from the barrel 3 of the sampler, power being supplied via a conductor (not shown). The motor drive shaft 12 passes through a reduction gearbox 13 and then terminates in a conical cam 14 which has an axial slot 1 5 therein.

The operating spindle 1 6 of the snap-shut valves of the sampling vessel has on the end thereof, an actuator 1 9 which is a bifurcated member pivotted on pivot 17 on the spindle near the end of the bifurcation. The end of the spindle 1 6 is spring biassed in the direction indicated by arrow Z in Figure 2 against a retaining pin 18 extending between the bifurcations. The actuator 1 9 has an elongate finger 20 bearing on the conical cam 14. The actuator is spring-biassed in the direction of arrow X in Figure 2.

When the motor 4 is activated the cam 14 rotates and the actuator finger 20 springs into engagement in the axial slot 1 5 moving the retaining pin 1 8 out of engagement with the valve spindle 1 6 thus allowing the valves to snap shut.

The "ioaded" position of the cam 14 and actuator finger 20 is shown in Figure 3A and the position after closure of the valves is indicated in Figure 3B. The "loaded" position of the valve spindle 1 6 and retaining pin 18 is shown in Figure 4A and the position after closure is shown in Figure 4B.

The arrangement shown in Figure 2 is the "loaded" position: the valves are held open by the retaining pin 18 of the actuator 19 which is urged in direction Z by the valve springs to cause the actuator finger 20 to bear on the conical cam 14.

The sloping surface of the cam 14 forces the actuator 19 upward to abut the sampler wail and this locks the valves in the open position.

As already stated the motor 4 is electrically insulated from the barrel of the sampler. Power is supplied through a single power supply line, the motor being earthed via the cam 14, and actuator 19 to the sampler wall. Thus the motor will be activated by supply of power via the single conductor. The slot 15 in the cam 14 is electrically insulated so that when the actuator finger 20 springs into the insulated slot 1 5 the connection to earth is broken and the motor 4 stops. (This is detected at a surface station by the motor current dropping to zero.) An event-iogger recognises a zero voltage as confirming closure of the valves and logs this event.

In Figure 1 , the probe control electronics are indicated by 10. The part 11 indicates electronic control circuitry for selectively switching power from part 10 to the motor 4. The circuit 10 is shown in Figure 2 of the drawings. The circuit 11 operates to supply a suitable voltage (around 14 volts) to run the probe electronics 10.To actuate the motor 3 from the surface, the voltage of the power supply is increased at the surface station to around 35-40 volts which is the operating voltage of the motor, Zennerdiode ZD1 passes current to the gate of thyristor THY1 which opens to pass power to the motor and shut off power to the probe electronics held on circuit 1 0. The switch S1 is held in the closed position by the shaft of the motor, that is, S1 in the closed position is (Figure 2) finger 20 contacting conical cam 14 on its non-insulated portion and, in the closed position is finger 20 contacting the insulated slot 1 5 of cam 14. When the valves have successfully closed S1 opens and shuts off the motor simultaneously causing the current to drop to zero. The current is monitored by the surface station and the drop to zero is recorded.

The opening of S1 simultaneously restores power to the probe electronics.

Claims (6)

1. A well sampler including a surface-located control station and a down-hole elongate tubular sampling vessel having electrically operable valve means for entrapping a fluid sample therein, means for detecting closure of the valve means and transmitting a confirmatory signal to the surface station.

2. A well sampler including a surface located control station, a down-hole elongate tubular assembly insertible endwise into a well and electrical cable for receiving and transmitting power and signals between the control station and the down-hole assembly; the assembly including; a monitoring probe responsive at least to temperature and pressure and electronic circuitry for transmitting corresponding signals from the probe to the surface station; a sampling vessel having electrically operable valve means for entrapping a fluid sample therein; and electronic control circuitry for selectively switching power from the probe circuitry to the valve means in response to a surface-initiated signal and including means for detecting successful operation of the valve means and transmitting a confirmatory signal to the surface station.

3. A well-sampler as claimed in Claim 1 or 2, in which the means for detecting valve closure is an electro-mechanical system in which the valves are actuated by an electric motor and a switch is provided in the power supply to the motor, the switch being held in one position by the open valves and is movable to the other position when the valves close, movement of the switch being indicative of valve closure.

4. A well-sampler as claimed in Claim 2, in which the valves are spring-loaded snap-shut valves held in an open position by a retaining pin and releasable by removal of the pin.

5. A well-sampler as claimed in Claim 3 or 4, in which the motor has a drive shaft terminating in a conical cam having an axial slot therein, a valve actuator in the form of an elongate finger is spring-biassed to bear on the sloping face of the cam so that on rotation the finger engages in the slot and the actuator is operatively connected to the retaining pin which is thus moved to its release position enabling the valves to snap shut.

6. A well-sampler as claimed in any preceding claim including also data and event-logging apparatus, power supply for the sampler and switchgear for operating the sampler from the surface.