Patent Application
20140144226
The oil and gas industry is very dependent on well bore measuring techniques to provide information about what is actually happening deep in a well bore. Many surveys are done before oil or gas is produced, including seismic and rock porosity, water content and micro seismic. However, there are few methods of obtaining data which gives a broad measurement of the behaviour of the well over its whole length.
Point pressure and temperature sensors have been in commonplace use since the 1940's and production logging tools are also now in common use. It is quite common in the oil and gas industry to run optical distributed temperature sensing systems into oil wells to measure the temperature profile over the complete length of the well bore.
The point sensors only provide indications of what is happening at the position of the sensor. Logging tools measure the complete well bore, but not in real time and they can only be run periodically. Logging tools are also difficult to run when there are pumps in the well bore. Distributed temperature measurement is limited by the fact that, while the temperature profile can be interpreted to give information about other behaviour in the well bore, the temperature information in its raw state is not immediately useful in terms of determining the fluid produced (or injected), or more importantly the fluid flow rates.
The oil and gas industry is under pressure to achieve greater efficiency and increase production rates, all of which requires more understanding of reservoir storage and production behaviour. This has created a need for more 2-dimensional and 3-dimensional measurements of reservoir behaviour.
It is therefore an aim of the present invention to address one or more of the above issues.
In a first aspect of the invention there is provided an elongate device for performing distributed fluid velocity measurement, comprising along its length:
Using such a device it is possible to measure heat loss from the core to its environment from, for example, the temperatures before and after a period of heating using the heated core.
Said distributed temperature sensor may comprise a fibre-optic distributed temperature sensor. Said distributed temperature sensor may be coiled helically around said heated core. Said distributed temperature sensor may be embedded within an insulation layer around said core. There may be at least one intervening layer between said insulation layer having said distributed temperature sensor embedded therein and said heated core. The insulation layer having the distributed temperature sensor embedded therein may be said outer layer of the device, or else said outer layer may be additional to this insulation layer comprising the distributed temperature sensor.
Said device may comprise a cable.
Said heated core may comprise a resistance wire.
Said device may further comprise control and processing means for controlling the heating of the heated core and processing the results obtained from the distributed temperature sensor.
Said device may further comprise a distributed fluid identification device for identifying a fluid that said device is immersed in at each of a plurality of measurement points of said device.
Said device may further comprise a distributed fluid identification device for identifying a fluid that said device is immersed in continuously over the length of said device.
Said device may be operable to: measure the ambient temperature of a fluid that it is immersed in at a plurality of measurement points along its length; turn on the heated core for a predetermined heating period, and take temperature measurements again at the same measurement points. Said device may be further operable to use obtained or pre-installed knowledge of the appropriate fluid characteristics so as to process said results obtained from the distributed temperature sensor to obtain distributed and/or point fluid velocity measurements for the fluid passing over the surface of said device. Said device may be further operable to determine real-time distributed and/or point fluid flow information from said distributed and/or point fluid velocity measurements. Said device may be further operable to use obtained or pre-installed knowledge of a number of fluid characteristics to identify which of said number of fluids it is immersed in at any one measurement point directly from the measured temperature at said particular measurement point after said predetermined heating period.
Said device may comprise a semi rigid construction to allow injection into well bores; for example said device may comprise a rigid element such as carbon fibre along its length.
in a second aspect of the invention there is provided a plurality of said devices operable to provide a 3-dimensional array of measurement points within a fluid in which said plurality of devices is immersed.
In a further aspect of the invention there is provided a method of performing distributed cooling measurements using the device, or plurality thereof, according to either of the above aspects of the invention, comprising the steps of:
immersing said device in one or more fluids along its length;
measuring the ambient temperature of said fluid or fluids at a plurality of measurement points along its length;
turning on the heated core for a predetermined heating period; and
measuring the temperature again at the same measurement points.
Said method may be further comprise using obtained or pre-installed knowledge of the appropriate fluid characteristics so as to process said distributed cooling measurements so as to obtain distributed and/or point fluid velocity measurements for the fluid or fluids passing over the surface of said device. Said method may comprise the further step of determining the real-time distributed and/or point fluid flow information from said distributed and/or point fluid velocity measurements.
Said method may comprise obtaining information to identify said fluid or fluids at the same time as performing said distributed cooling measurements.
Said method may comprise using obtained or pre-installed knowledge of a number of fluid characteristics to identify which of said number of fluids it is immersed in at any one measurement point directly from the measured temperature at said measurement point after said predetermined heating.
Said method may comprise deploying said device in a well bore, in a pipeline where it can be used to detect and/or locate leaks and/or branches, or in a fluid storage facility such as a tank, reservoir, separator etc. in the latter case, multiple devices may be installed as per the second aspect of the invention.
Embodiments of the invention will now be described, by way of example only, by reference to the accompanying drawings, in which:
a and 2b show the cable based sensor of
a-4c show three examples of how a cable based sensor array may be installed in a well bore;
The cable based sensor array 110 is shown in greater detail in
The heated core 200 can comprise any heat source means (including a heated fluid), but in a main embodiment comprises a current carrying wire heated by resistance heating. Using a resistance wire simplifies temperature control compared to other heating methods, and also provides for a substantially uniform heat rise above ambient along its length.
The fibre optic sensor array 230 may be any of the types known in the art The use of intrinsic fibre optic sensors to provide distributed temperature sensing over very large distances is well known. For example, temperature can be measured by using a fibre that has evanescent loss that varies with temperature, or by analyzing the Raman scattering of the optical fibre. The fibre optic sensor array 230 is located between the heated wire core 200 and the outside surface of the device, along the sensing length of the device.
The cable based sensor array 110 operates by measuring the cooling effect resultant from the fluid or gas flowing over the surface of the cable. It does this, in one operational embodiment, by first measuring the ambient well bore temperature at each optical measurement point being considered, followed by switching the heated core on for a predetermined heating period, and then taking temperature measurements again at the same optical measurement points. The temperature rise caused by the heated core at each measurement point is dependent on the thermal cooling of the walls of the cable at that point, which in turn is dependent on, and therefore allows the measurement of, the fluid velocity characteristics around the cable surface at that point. The principle of fluid velocity measurement using cooling of a heated object is well proven and documented uses date back to 1904.
Of course, to obtain the of fluid velocity measurement from the cooling information, the nature of the fluids must be known since the cooling resultant from each fluid is different.
The cable based sensor array 110 can also be used without any further sensors to determine the type of fluid present, provided that sufficient information on the thermal conductive character of the fluid present is known. If so, then the absolute temperature of the surface at the end of the predetermined heating period will be indicative of the nature of the fluid flowing. This is easily appreciated by considering the fact that gases typically will cool the surface of the sensor much less than liquids will. By using set values and having pre-observed the temperature rises created by different flowing fluids, the type of fluid can be determined directly from the final temperature reading.
a-4c show three examples of how such a cable based sensor array may be installed in a well bore.
The cable based sensor array 110 has many applications other than the measurement of fluid and gas flow characteristics over the length of an oil or gas well and the providing of information on the fluid being produced in each rock formation as already described.
While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, features of the invention, such as those for processing, may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.
The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1018382.0 | Nov 2010 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB2011/052086 | 10/26/2011 | WO | 00 | 6/14/2013 |
