US2203720A - Apparatus for detecting water intrusion in boreholes - Google Patents

Description

APPARATUS FOR DETECTING WATER INTRUSION IN BOREHOLES,

June l1, 1940.

Filed Dec. l0, 1934 2 Sheets-Shea?I 1 June 11, 1940. Q Rn DALE 2,203,720

APPARATUS FOR DETECTING WATER INTRUsIoN IN BOREHOLES Filed Dec. 10, 1934 2 Sheets-Sheet .2

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Patented June 11, 1.940

UNITED STATES PATENT OFFICE APPARATUS FOR DETEOTING WATER INTRUSION IN BOREHOLES Clarence R. Dale, Los

Angeles, Calif., assignor,

Application December 1o, 193i, serial No. 756,765

1` Claim.

As is well known when an oil well is drilled, water bearing strata are often encountered, necessitating the shutting oil? of these strata. It is generally very dicult to ascertain the exact location of the intrusion point 4without resort to special water detecting means. Having found the point or points of water intrusion, a string of casing is run down to below the water strata and cemented in place by well known methods.

After the cement has set, it is desirable and often required by government regulations that the water shut off be tested. For this purpose also special water detecting means can be used. Having effected a satisfactory water shut oil" the well is carried down by drilling through the casing with drilling tools of smaller diameter. In carrying down a well several water shut offs may be necessary 'before the oil sand is reached. Besides encountering water strata above the oil sand, water strata between oil sands and below them are often encountered necessitating the ascertaining of its source and its shutting oi from the borehole.

Even after a well is completed and has been producing for some time water will appear in the oil produced from the well in such quantities that it is necessary to nd its location and shut it oil".

It will thus be readily seen that the accurate locating of points of intrusion of water into boreholes is of the utmost importance in order that the necessary remedy can be applied eifectively.

Several methods have been devised for locating the points of intrusion of the water. One method for rampie primarily consists in placing an electrolyte in the hole, lowering spaced electrodes into the hole and reading the voltage registered on a voltmeter at the well head. The point of intrusion will be indicated by a lowering of the E. M. F. by reason of the dilution of the electrolyte by the water.

Another method consists in replacing the mud or other liquid in the well by fresh Water, generating an alternating current at the well head and lowering two spaced electrodes into the well.

lThe resistance of the water is measured at the (Cl. 'Z3-51) provides a positive method for ascertaining the point of water intrusion.

In brief, my invention contemplates the ascertaining of the point of Water intrusion by photoelectric means.

The vaccompanying drawings illustrate by way of example the method and means by which my invention may be carried into eiect.

Referring .to these drawings:

Fig. I is a longitudinal sectional View of the detector.

Fig. II is a diagrammatic section of a borehole in condition for test.

Fig. III is a diagrammatic section of the borehole shown in Fig. II but with the detector in lowered position in the hole.

Fig. IV is a chart showing results of tests made according to my method and with my apparatus.

Referring in particular to Fig. I the detector in the main comprises three sectionsz-an upper section I by which a cable is securely attached, called the cable attaching section; a middle section 2 inwhich is housed an electric battery, called the battery section; and a lower section 3 containing a source of light and a photo-electric cell called the light section. The three sections are assembled one on top of the other 4by screwing them together.

The cable attaching section I has a hole l along its longitudinal axis of suicient size to accommodate a two wire electric cable 5. A- segment of the side wall S of the cable attaching section is removable and is held in position by suitable bolts I so that it, together with the complementary part of the cable attaching section forms an effective clamp for the cable 5.

TheV upper end of the cable attaching section is tapered so that the instrument `will not be so likely to catch on any obstruction in the boreholes into which it is designed to be lowered as is hereinafter explained. The lower part of the cable attaching section is tubular and houses the end of the cable 5 and the couplings 8 for connecting the endsof the insulated wires 9 of the cable to the insulated wires 40 leading into the battery section 2. This latter section is tubular and contains an electric battery which may for example, consist of three cylindrical cells I0, II and I2 connected in series in the usual manner. The bottom of the lowermost cell I2 is grounded to the body of the instrument, The central electrode of the uppermost cell I0 contacts an insulated metallic button I3. From this button I3 an insulated wire I4 leads into the light section 3. This light section consists in the main of an open ended tube I5 having mounted therein an inner cylinder I6. At the upper end of this cylinder I6 is Vmounted a photo-electric cell I1 with its light sensitive part facing downward. A lens I8 is positioned in front of the cell I1. Facing the lens I8 but at a short distance therefrom is a second similar lens I9. Below this second lends I9 an electric light bulb 20, for example, an ordinary flashlight bulb, is mounted in a suitable holder 2|. A metallic plug 22 seals the lower end of the cylinder I6. IA groove 23 is cut in the outside wall of the cylinder |6 from the plug end to a point between the two lenses I8 and I9.

A traverse passageway 24 between the two lenses I8 and I9 is provided at right angles to groove 23. It should be here noted that the lenses are so arranged that their faces protrude slightly into the passageway for reasons which will hereinafter appear.

'Ihe outer tube I5 is screw threaded into position over the cylinder I6. An opening 23 in this outer tube I5 coincides with the end of the lateral passageway 24 opposite the passageway 23.

'I'he insulated wire I4 from the battery section 2 is connected to the light bulb holder 2|. Thecircuit is completed by screwing in a set screw in the end plug 22 thus grounding one of the contacts `of the light bulb 20.

The two wires 40 leading from the cable are connected to the terminals of the photo-electric cell I1. In the above disclosure it should be borne in mind that various items such as packing glands, gaskets et cetera for rendering the desired parts watertight and means for adding weight to the detector have not been rshown or particularly described as such will be apparent to those skilled in the art.

In order to illustrate one use to which my detector can be put, reference is made to Fig. II and Fig. III as well as Fig. I; Fig. 1I represents a drilled well in which the water string 26 has been successfully cemented in place just above an oil sand 21 as is a usual practice.

Water is known to be entering the hole; itis assumed for example, that'it is necessary to ascertain its location in order that it may be sealed off before completing the well.

Having obtained a uniform concentration of mud 34 throughout the hole for example, by circulating mud down through the drill pipe and bit, (not shown), the tools are withdrawn from the hole.

In many cases the pressure in the water strata is not high enough to force its water into the hole in sufficient quantities to enable the point of intrusion to be detected when the hole is full of liquid owing to the high hydrostatic head. Therefore, in order to produce an appreciable flow of water into the hole, the level of liquid in the hole is reduced by bailing as for example, has been done for a considerable number of years to test the water shut off after the cementing of casing. When the liquid in the hole is at the desired level the current to the light bulb of the detector is turned on and the detector lowered into the hole by means of the cable 5, part of which is shown in section in Fig. I. The cable is gradually payed out from a drum 28 at the surface.

The uppermost ends of the two insulated wires 9 in the cable are arranged to contact the leads 29 of a micro-ammeter 30.

As the detector is lowered through the muddy water, a stream thereof continually passes through the passageway 23 of the detector (see Fig. I) across the instrument between the lenses I8 and I9 and out through the opening 25. As little or no light will reach the photo-electric cell during the time the detector is passing through the uniformly muddy water 34, little or no current will be registered on the micro-ammeter 30; As the point of water intrusion is approached, which for the sake of illustration is shown indicated at 3| in the strata 32 between two oil sands 21 and 33, the opaqueness of the muddy water passing between the lenses will be reduced gradually due to the diluting of the muddy water by the water seeping into the hole from 3|. More light will therefore reach the photo-electric cell I1 which in turn will generate more current, resulting in a greater reading on the microammeter 30.

At the point of water intrusion the water may be perfectly clear producing a considerable increase in the reading of the microammeter. On lowering the detector past the point of water intrusion the reading on the microammeter suddenly decreases as the muddy water is not diluted below the'point of intrusion.

Having a record of the length of cable lowered into the hole, the point of intrusion is thus readily ascertained.

In some cases, it is not practical to previously circulate the mud in the hole and in some cases an opaque liquid can often be made uniform enough byv running a bailer or the detector itself up and down the well several times so that an improvised stirring is effected.

'I'he detector can also be used in owing wells as the opaqueness of the crude oil is suicient to render an appreciable contrast with the entering water.

However, it is preferable to displace the liquid in the hole. from the bottom up with a cloudy aqueous liquid for example, a rotary drilling mud of about 63 lbs. per cubic foot has been Very satisfactory.

I have found in practice that with the selenium photo-electric cell I am now using, that it is necessary to amplify the current by the use of flashlight batteries in series with the microammeter. These may either be located in the instrument or at the surface.

In detecting water intrusion at considerable depths it may sometimes be desirable to amplify the variations in current produced by the photoelectric cell before transmitting them to the surface as the initial current may not be of sufficient amplitude to show an'appreciable reading on the meter at the surface.

In using the detector in boreholes containing oilit is desirable to coat the lenses I8 and I9 -J with a transparent colloid which will prevent the adhesion of oil to the lenses, for example, I have found agar agar to be satisfactory although it should be remembered that I may also use glycerine or any other substance which will produce the desired effect.

By arranging the lenses`|8 and I9 so that their faces protrude slightly into the stream of liquid I passing between them the likelihood of oily or other material adhering to the lenses is greatly reduced.

By means of my detector it is possible to locate l ascenso readings taken in testing a well for water intrusion in southern California.

As it had been previously ascertained that a certain intensity`of light gave a particular read'- the hydrostatic head on the strata.

Run B indicates a point at depth of 4375 feet, at which the water is clearest denoting intrusion in this area. The detector was next run up and down the well several times fairly rapidly in the vicinity of the yleak to render the opaqueness uniform in this area. The detector was then withdrawn to a point considerably above the intrusion area i. e. 'to the 3000 ft. level and a period of about fifteen minutes allowed to lapse.

Test C was' thereafter made. The object of the above mixing by running the detector up and down was to narrow down the area of intrusion indicated in test B. i

A final test D was made to verify the results of tests B and C. It will be noted that by the time test D was made the area of appreciable dilution had increased in size, owing to the greater amount of clear water that had come into the borehole.

It should be understood that I do not limit myself to the particular example of my invention as above described and that I may" make any changes therein within the scope of the appended claim.

It should be particularly noted that instead of using muddy water or crude oil in the borehole to provide an opaque liquid medium, I may fill the borehole with clear water and thereafter provide a uniform opaqueness of the liquid by dissolving a dye in the water by running a bailer containing the dye up and down the length of the hole. The dye can also be added to the water before it is placed in the borehole.

I claim as my invention:

Apparatus for detecting water intrusion in a borehole comprising a casing, a photo-electric cell traversely mounted in said casing, a source of light in said casing, an L-shaped open passageway passing from the end of said casing between said source of light and said photo-electric cell and emerging through the side wall of said casing. meansf for raising and lowering said casing assembly in a borehole filled with liquid, a microammeter on the surface of the earth and leads electrically connecting said photo-electric cell to said microammeter.

CLARENCE R. DALE.

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