Radiant energy – Geological testing or irradiation – With sampling
Patent
1998-04-29
2000-08-01
Hannaher, Constantine
Radiant energy
Geological testing or irradiation
With sampling
250301, 2504581, 2504591, 2504611, G01N 2164
Patent
active
060970278
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to method and techniques for identifying oil columns by determining whether a rock that is capable of oil entrapment has had or presently contains oil, for example, in a site suspected of containing an oil column. The invention also allows the determination of the location of various boundaries between different parts of a site, including parts that have never retained oil, parts that have previously retained oil or parts that currently retain oil. In particular, the invention makes use of two different analytical techniques (GOI and FOI; defined below) and has particular application with test drilling and exploration for oil columns, but can also be used during commercial drilling and re-exploration operations.
BACKGROUND ART
In exploration for oil columns, for example offshore (subsea) oil columns, when a potential column has been identified, (ie. using standard geological exploration techniques), it is usual practice to test-drill the site to ascertain whether the site contains oil (or could contain oil other than at the point of drilling).
Test drilling is typically expensive and is performed by stringing together pieces of pipe and drilling through, usually, a shale crust until a reservoir (eg. of sandstone or limestone) suspected of containing oil is reached. The rate of penetration of drilling increases when such a reservoir is reached, and this signifies that testing for oil in the reservoir can commence. Mud and cuttings from the drilling operation eventually reach the drill rig at the ocean surface (eg. in offshore exploration) and these are analysed in order to determine the presence or absence of oil. The techniques of cuttings analyses are collectively referred to as "shows". Known show techniques include detecting hydrocarbon gases in the mud by flame ionisation or thermal conductivity, detecting oil fluorescence by ultraviolet illumination of the mud, and oil stain, oil odour and oil cutting (adding of solvent) techniques etc. However, the existing techniques can be subject to false and/or ambiguous results. For example, heavy mud used to seal around the drill string during drilling may include hydrocarbon and this can also reach the surface during testing giving false results.
It would be advantageous if a show technique could be provided that reliably indicates oil presence (or absence) in a reservoir, either now or in the past, for example, during test-drilling and/or drill site re-exploration to assist in the location of an oil column.
SUMMARY OF INVENTION
In a first aspect the present invention provides a method of using natural oil inclusions in rock that is capable of oil entrapment to determine whether that rock has had, or presently contains, oil comprising the steps of: inclusion(s), or the number of regions that do not contain oil inclusion(s), as against the total number of regions selected; and the determination to be made as to whether or not the rock has had or presently contains oil.
Because the method makes use of the natural fluid inclusions within minerals in rocks that are capable of oil entrapment, it can be practiced in a highly reliable manner so that the contamination effects of other show techniques are ameliorated or eliminated. By determining a ratio in the manner as defined, and comparing that ratio against standard rock samples, the method can be standardised and, in some forms, automated so that an immediate result as to the existence or absence of oil, whether now or in the past, can be obtained (eg. in situ).
For example, when the ratio determined by the method is at or greater than a certain threshold level (eg. as determined from the standard rock samples from commercial oil columns) this can provide an indication that the sample has come from a site: recoverable quantities of oil; or containing recoverable quantities of oil (eg. due to displacement, at some time in the past, of oil from the site either by gas or water).
The result obtained in either case can indicate that an oil column is present a
REFERENCES:
patent: 4856351 (1989-08-01), Smith
patent: 5241859 (1993-09-01), Smith
patent: 5543616 (1996-08-01), Eadington et al.
T. Allen "Particle Size Measurement" (Third Ed.) 1981, Chapman and Hall Ltd. (London) pp. 115-119.
Derwent Abstract No. 93-241317/30 (Gubkin Geology Inst) Jul. 23, 1992-SU 1749877.
G. Clark "The Encyclopedia of Microscopy" Reinhold Publ. Corp. (Baltimore) 1961 pp. 462-477.
Eadington Peter John
Krieger Francis William
Lisk Mark
Commonwealth Scientific and Industrial Research Organisation
Hannaher Constantine
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