Wells – Processes – Sampling well fluid
Reexamination Certificate
2001-09-24
2004-03-09
Bagnell, David (Department: 3672)
Wells
Processes
Sampling well fluid
C166S060000, C166S066000, C166S250010, C175S059000, C073S152280, C073S152330
Reexamination Certificate
active
06702017
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a well fluid sampling tool and to a well fluid sampling method.
The invention particularly, though not exclusively, relates to a so-called single phase or monophasic sampling tool, and related method.
BACKGROUND OF THE INVENTION
There are many circumstances where it is desirable to sample a fluid material, whether as a gas, a liquid, or a mixture of the two, and determine its nature, for example, its physical and chemical composition, to determine information about the body of fluid from which the sample was taken. On some such occasions the sample may be obtained under one set of ambient conditions—of pressure and temperature, say—and thereafter removed to a quite different set for analysis such that, if unprotected, the sample's state—e.g. its physical and chemical form—may change during this removal until it is no longer sufficiently representative of the original fluid. One typical example of this situation occurs when sampling fluids issuing from geological formations into which a well, such as an oil/gas well, has been drilled. At the bottom of the well, which may be several miles deep, pressure and temperature are high—possibly several hundred atmospheres, and in the low hundreds of degrees Celsius. Whilst the formation fluid may under these ambient conditions be a single phase fluid, nevertheless a sample of this fluid transported to quite different ambient conditions of the surface (specifically of pressure and temperature—often referred to as NAP, Normal Atmospheric Pressure, or as NTP, Normal Temperature and Pressure), where it is to be analysed to reveal useful information about the well, may easily separate into two or more distinct phases—for example, a liquid phase, a gas phase (originally dissolved in the liquid), and a solid phase (originally suspended or in solution in the liquid).
As such, the separated sample is no longer truly representative of the original fluid—or, at least, not in an easily-understood way—and so has lost much of its value. Indeed in some circumstances it may be impractical to reconstitute the original fluid sampled.
Single phase sampling tools are known. For example, WO 91/12411 (OILPHASE SAMPLING SERVICES) discloses a well is fluid sampling tool and method for retrieving single-phase hydrocarbon samples from deep wells. In that document the sampling tool is lowered to the required depth, an internal sample chamber is opened to admit well fluid at a controlled rate, and the sample chamber is then automatically sealed. The well fluid sample is subjected to a high pressure to keep the sample in its original single-phase form until it can be analysed. The sample is pressurised by a hydraulically-driven floating piston powered by high-pressure gas acting on another floating piston. Once sampling is initiated e.g. by an internal clock, the entire sequence is automatic.
GB 2 252 296A (EXAL SAMPLING SERVICES) discloses an arrangement which is pressure compensated, so that as the container is lifted to the surface, and the ambient pressure and temperature drop, firstly the sample itself is sealed off to prevent it expanding (and separating) under the reduced pressure, and secondly the original ambient pressure is positively maintained despite any temperature change seeking to cause a corresponding pressure change (so that temperature-induced pressure drop and phase separation is avoided). This end is attained by a sampler wherein the sample chamber, in which the sample itself is received and stored, is sealingly closed at one end by a moveable partition to the other side of which is applied either directly or indirectly (via a buffer fluid) a source of suitably pressured gas.
The aforementioned sampling tools essentially use compensation techniques, i.e. the pressurised gases act on the sample to compensate for pressure drop in the sample due to temperature drop. These sampling tools, therefore, require the provision of a gas reservoir and complicated mechanisms to apply pressure to the sample to compensate for temperature reduction induced pressure changes.
SU 368 390 (MAMUNA et al) discloses a device for withdrawing samples of formation oil, including a body, a receiving chamber with a piston, and an inlet valve, wherein the receiving chamber is fitted with an electric heater connected to a thermometer mounted in the piston, with the aim of preserving the properties of the formation oil in the sample withdrawn.
WO96/12088 (OILPHASE SAMPLING SERVICES) discloses a well fluid sampling tool and method for retrieving reservoir fluid samples from deep wells. In this document the sampling tool is lowered to the required depth, an internal sample chamber is opened to admit well fluid at a controlled rate, and the sample chamber is then automatically sealed. The temperature of the sampled well fluid is maintained at or near initial as sampled temperature to avoid the volumetric shrinkage otherwise induced by temperature reduction, mitigate precipitation of compounds from the sample, and/or maintain the initial single phase condition of the sample. The sample chamber is thermally insulated, provided with a storage heater, electrically heated, given a high heat capacity, and/or pre-heated to sample temperature.
A problem with prior art single phase sampling tools is that the tool must be lowered, in use, down within a is drillstring. The tool must, therefore, be of less than a predetermined outer diameter. However, the tool should also be as short as possible, for example, to seek to avoid the tool becoming stuck or “hanging-up” within the drillstring.
It is an object of at least one aspect of the present invention to obviate or mitigate one or more of the aforementioned problems in the prior art.
It is a further object of at least one aspect of the present invention to seek to provide an optimum sized sample chamber within a tool of particular outer dimensions (outer diameter and length).
SUMMARY OF THE INVENTION
These objects are addressed by the general solution of providing a well fluid sampling tool with an evacuated chamber surrounding at least part of a sample chamber, an outer wall of the evacuated chamber being adjacent to or preferably forming an outer wall of the tool.
According to a first aspect of the present invention there is provided a well fluid sampling tool having, at least in use, a sample chamber at least partly contained within an at least partially evacuated jacket, an outermost wall of the jacket being adjacent to or forming an outermost wall of the tool.
In such a tool the evacuated jacket acts to maintain the sample as originally retrieved, e.g. in single phase form (at original temperature).
Advantageously the sample chamber is substantially contained within the evacuated jacket.
Preferably, the evacuated jacket comprises first and second tubular bodies, the first tubular body comprising the outermost wall of the jacket and the second tubular body being provided within the first tubular body, an evacuated chamber being provided between the two bodies.
Advantageously, the evacuated chamber is formed by a longitudinal annular space between the bodies.
The pressure in the annular space may be approximately between 10
−7
PSI and 10
−11
PSI and typically around 10
−8
PSI.
Preferably, the first and second bodies are formed in one piece, being joined at least one end.
Preferably also, the sample chamber is provided with a third tubular body which is at least partly provided within the second tubular body.
Advantageously, sample temperature maintenance means are provided, preferably between the second and third tubular bodies.
Preferably, the temperature maintenance means include a plurality of heaters spaced longitudinally between the second and third tubular bodies.
Advantageously the heaters are sized to seek to compensate for heat loss at their respective locations.
Advantageously first and second heaters provided at first and second ends of the third tubular body are more powerful than heaters provided distal from the first and second ends. This arrangeme
Corrigan Neil David
Morgan Quentin Peter William
Smith William Lawson
Expro North Sea Limited
Gay Jennifer H
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
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