GB2322846A

GB2322846A - Bore sampler for high-temperature fluid

Info

Publication number: GB2322846A
Application number: GB9704387A
Authority: GB
Inventors: Nigel Halladay; Brian Piper
Original assignee: CSM ASSOCIATES Ltd
Current assignee: CSM ASSOCIATES Ltd
Priority date: 1997-03-03
Filing date: 1997-03-03
Publication date: 1998-09-09
Anticipated expiration: 2017-03-03
Also published as: WO1998039552A1; GB9704387D0; GB2322846B

Abstract

A high-temperature fluid sampler, for bore-hole fluids, has a sample chamber 3 separated from a working-fluid chamber 6 by a movable piston 4, and an annular space 8 around the sample chamber 3 into which working fluid is forced by the piston 4 to cool the sample. The fluid enters via a non-return valve 9 with a high-temperature plastics seat and the filling is initiated by a bursting disc/needle mechanism with a double-latch trigger action (Fig 1B).

Description

IMPROVEMENTS IN OR RELATING TO SAMPLERS FOR HIGH-TEMPERATURE FLUIDS This invention relates to sampling apparatus for fluids at high temperatures. It is especially applicable to the sampling of borehole fluids at 3000C or above.

Two types of fluid-sampler are already known for such fluids and may be designated the through-flowt type and the vacuums type respectively.

The flow through type can be likened to a tube which has both ends open and allows fluid to pass through as it is lowered down the borehole. When the selected position is reached(depth in the borehole) the ends of the tube are closed and the fluid inside trapped. This is then recovered to surface for analysis. The fluid inside the sampler will be a mixture of the fluid that the sampler has recently passed through and not necessarily representative of the fluid chemistry at that point in the borehole.

The vacuum type consists of a closed tube which is opened at the desired location allowing fluid to enter. It is then closed and recovered to surface as before. It is described as a vacuum type because the pressure in the closed tube is either atmospheric or indeed a vacuum, both of which are very low pressures compared to the borehole pressure. The result of this low pressure is that the hot fluid entering the sampler will boil and its geochemistry alter.

The above types have been used for sampling of fluids at up to 3000C.

For lower temperatures (9200 C) a different type of sampler has been developed, the Controlled Displacement Sampler (CDS). In this type there are two chambers inside the tool body. The first is split into two sections by a movable piston which on set up is located at the top of the upper chamber. Underneath the piston the remainder of the upper chamber is filled with water and is referred to as the working fluid. Between the two chambers a throttling valve is located. The lower chamber is empty and at atmospheric pressure. When the sampler is opened to allow fluid to enter, it does so at the top of the upper chamber above the piston. Due to the throttle and the working fluid, the pressure in the sampled fluid remains high as the piston can only move slowly down the upper chamber as the working fluid, pressurised by the piston and sampled fluid, leaks away into the lower chamber. Hence a controlled displacement of the piston occurs. The problem with CDS tools is that dynamic seals are required and are temperature limited (1800C max).

We have now developed a fluid-sampler which can be used at 4000C and which is a variation on the CDS system, with special features to allow heat-dissipation from the hot fluid so that piston and seals can function at a lower temperature.

The invention consists of a fluid-sampler for high-temperature fluids, comprising a generally-cylindrical heat-insulated casing, containing a non-return fluid inlet valve leading to a fluid-sample chamber separated, by a movable piston, from a working-fluid chamber which communicates with an annular space around the sample-chamber, whereby working fluid displaced by the piston flows into the annular space and acts as a cooling medium for the sample.

Preferably the casing is surrounded by an evacuated double-walled vessel of the DEWAR type.

Preferably the working fluid is water or an aqueous solution of suitable salts.

Preferably the sampler is opened to the hot fluid by means of a bursting - disc/needle combination which is controlled by ball-latch mechanisms which allow a very powerful spring to fire the needle, but a small force to actuate the mechanism (about 100th of the spring-release force).

The non-return valve preferably uses a high-temperature-resistant plastic material as an insert between a metal valve-stem and seat.

The sampler is opened by perforating a thin bursting disc with a timer-controlled needle. The needle mechanism uses two inline ball latch mechanisms in order to allow a very powerful spring to fire the needle but a very small force to actuate it. The small force is required as a magnetic couple transfers the actuation force through a pressure bulkhead, there being no direct contact as the latch mechanism is in an oil filled system that is at the same pressure as the borehole and the motor drive system is at atmospheric. The motor is battery-driven and so only low forces are required to minimise the battery load. The whole tool is memory based, there being no communication with the surface as at the temperature of operation there are no wireline cables available (electromechanical cables) so simple steel wire ropes are used.

The invention offers the benefit that the seals on the piston are passing over metal which has not been exposed to the hot borehole fluid, and is being cooled by the working fluid surrounding the sample-chamber.

The invention will be further described by reference to the accompanying schematic drawings wherein.

Figure 1A is a section through a sampler according to the invention.

Figure 1B is a section through a heat insulation plug through which the fluid enters the sampler.

Figure 2 shows a section through a non-return inlet valve, through which the fluid enters the sample chamber.

Figure 3 shows a section through a mechanism for releasing a needle to penetrate a bursting-disc, to provide fluid feed to the sampler, via the inlet valve.

With reference to Figure 1A, a casing 1 is surrounded by a double-walled evacuated vessel (DEWAR) 2 and contains a sample-chamber 3, a piston 4 with a ceramic head 5, and working-fluid chambers 6 and 6A separated from the sample chamber by the piston 4/5. Hot fluid enters the sample chamber 3 via non-return valve 7 and forces the piston 4 to expel working fluid from chamber 6 into subsidiary chamber 6A via narrow passages. From 6A the fluid flows into the annular space 8 where is helps to cool the sample in chamber 3.

With reference to Figure 1B, the heat plug has an inlet bursting-disc 1, a particle filter 2, a small-bore thin-walled inlet tube 3 which is insulated with glass wool 4, contained within a stainless steel tube 6, and a heat-sink 5, leading to inlet-valve (7) (see Figure 1A) to admit hot fluid into the sample-chamber.

With reference to Figure 2, the inlet valve has an inlet passage 1, a valve-stem 2, a high-temperature-plastic valve-seat 3, a valve-spring 4, against the pressure of which the sample is forced through the valve, flowing around valve-seat 3, and exiting via outlet passage 5.

With reference to Figure 3, the needle-firing mechanism has a magnetic actuator 1, two ball-latch mechanisms 2 and 3 located within sliding sleeves 4 and 5, which actuate a powerful compression spring 6 to release the needle 7 to perforate the bursting disc (not shown in Figure 3 but shown in Figure 1B).

In order to fill the sampler, the needle-release mechanism is triggered by activating magnetic actuator 1, (Figure 3) and the needle penetrates bursting disc 1 (Figure 1B) allowing hot fluid to reach the inlet valve 7 (Figure 1A) of the sampler. From here, the sequence is as described for Figure 1A. Once the sampler is filled it is withdrawn by means of a wire-rope from the bore-hole.

Claims

1. A fluid-sampler, for high-temperature fluids, comprising a generally-cylindrical heat-insulated casing containing a non-return fluid-inlet valve leading to a fluid sample chamber, separated by a movable piston from a working-fluid chamber which communicates with an annular space around the sample-chamber, whereby working-fluid displaced by the piston flows into the annular space and acts as a cooling medium for the sample.

2. A fluid-sampler as claimed in claim 1 wherein the casing is surrounded by an evacuated double-walled vessel of the DEWAR type.

3. A sampler as claimed in claims 1 or 2 wherein the working fluid is water, or an aqueous solution of suitable salts.

4. A sampler as claimed in claims 1-3 wherein the sampler is opened to the hot fluid by means of a bursting dise perforated by a needle, controlled by ball-latch mechanisms which allow a powerful spring to fire the needle, but a small force to actuate the mechanism.

5. A method of sampling a high-temperature borehole fluid at 3000-4000C, comprising flowing hot fluid via a non-return valve into a sample chamber, separated by a piston from a working-fluid chamber, driving working fluid from the chamber, by the piston, into an annular space surrounding the sample chamber, cooling the sample by means of the working fluid in the annular space, and with-drawing the sample.

6. A fluid-sampling apparatus substantially as hereinbefore described with reference to Figure 1A, 1B, 2 and 3 of the drawings.