Measuring and testing – Borehole or drilling – Fluid flow measuring or fluid analysis
Patent
1997-09-04
1998-09-08
Chilcot, Richard
Measuring and testing
Borehole or drilling
Fluid flow measuring or fluid analysis
E21B 4900
Patent
active
058047140
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a flowmeter designed to find areas containing currents in a hole bored in rock.
In searching rocks via measurements in deep bore holes, a serious problem is the slowness of the measurements. Measuring only the vertical current at a given depth in a hole provides practically no information about chinks at different depths in the rock or the magnitude and direction of currents flowing in them. On the other hand, making accurate measurements e.g. by sections of a few hundred meters over the whole length of the hole to obtain the flow rates and directions for the section is a very slow process in long holes going to depths as large as thousands of meters.
As the bore hole may contain long stretches of solid rock without any fissures or currents, the object of the invention is to produce a new type of flowmeter which makes it possible to search even deep holes and locate the areas containing currents for more elaborate further investigation.
As for the features characteristic of the invention, reference is made to the claims.
SUMMARY OF THE INVENTION
The flowmeter of the invention comprises suitable flexible and elastic parting elements by means of which the section to be measured is separated from the hole substantially pressure-tightly. In other words, the parting elements are made of an elastic material that is pressed against the surfaces of the hole under measurement, such that they are tightly pressed against the hole without any inflatable or expandable structures activated by means of a pressure medium. Moreover, the flowmeter is provided with an open flow duct forming a free flow connection past the section under measurement delimited by the parting elements, so that currents occurring in other parts of the hole will not produce any pressure differences against the parting elements and these will, with a relatively low pressure, sufficiently seal off the hole section to be searched. In addition, the flowmeter comprises a measuring duct leading from the section under measurement to a point outside it and provided with measuring instruments by means of which the total flow of currents flowing into or out of the section can be measured.
The flexible and elastic parting elements used are preferably plate-shaped or ring-shaped rubber or plastic discs with a free external diameter somewhat larger than the diameter of the hole to be searched. Moreover, in a hole measured from a direct radial direction, the rubber or plastic discs preferably have a shape turned or curved somewhat upwards, permitting easy descent of the flowmeter down the hole by the agency of its own weight. At the measuring depth, the flowmeter is pulled back up through a small distance, causing the discs to buckle into a different position. In this condition, the internal tension of the parting element itself presses it against the hole surface, increasing its tightness.
The rubber discs of the invention acting as parting elements cannot withstand a very large pressure. On the other hand, in this type of measurement the pressure level in the section under measurement is the same as in the rest of the hole, so there is no need for a high pressure-tightness. However, to ensure tightness, both parting elements are made up of several, e.g. three successive rubber discs. The prototype of the flowmeter of the invention was implemented using three rubber discs, which can withstand the pressure of a 11/2-meter water column and therefore provide a sufficient tightness in all relevant measurement circumstances.
Especially when relatively large and sloping holes are being searched, the flowmeter's own weight may press the rubber discs to one side, causing the sealing to leak on the other side. In such applications it is preferable to use separate disc-shaped, plug-shaped or other similar rigid centering elements which, having a diameter nearly equal to that of the hole, prevent significant radial motion of the flowmeter in the hole.
The measuring equipment preferably includes a suitable i
REFERENCES:
patent: 4800752 (1989-01-01), Piers
patent: 4928758 (1990-05-01), Siegfried, II
patent: 5178006 (1993-01-01), Wicks, III et al.
patent: 5184677 (1993-02-01), Dobscha et al.
patent: 5226485 (1993-07-01), Dobscha et al.
patent: 5337821 (1994-08-01), Peterson
Aryis Jewel V.
Chilcot Richard
Posiva Oy
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