US2596437A - Method and apparatus for detecting fluid movement in well bores - Google Patents

Description

May 13, 1952 G. H. RoHRBAcK ETAL 2,596,437

l METHOD AND APPARATUS FOR DETECTING FLUID MOVEMENT IN WELL BORES Filed Feb. 16, 1951 Patented May 13, 1952 IJIETHOD AND APPARATUS FOR DETECTING FLUID MOVEMENT IN WELL BORES Gilson H. Rohrback, Whittier, Robert A. Stoner, Fullerton, and Malcolm Macaulay and William T. Cardwell, Jr., Whittier, Calif., assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware Application February 16, 1951, Serial No. 211,304

(Cl. F75- 182) 9 Claims.

The present invention relates to method and apparatus for detecting the movement of fluids in a well bore, and more particularly relates to determination of the direction of fluid flow in a well bore, whether said ilow is due to the entrance of contaminating fluids into the well or due to the loss of well fluid to an earth formation through which the well bore passes.

Heretofore, in the art of detecting the influx or ingress of contaminating fluids into a well bore, such as the entrance of water into a producing cil well at an unknown level, it has been common practice to provide a pair of electrodes in the well bore with at least one electrode at the level to be investigated. The electrical resistance between that pair of electrodes is then measured by the application of an external current source of either A. C. or D. C. potential. Changes in the electrical resistance are then correlated with the depth of the electrodes to locate the elevation at which water is entering the well. In some instances it has been proposed that the iluid in the well be entirely replaced by a testsolution prior to making these resistance measurements. Another method proposed in the prior art is that of introducing an electrolyte solution into the well to create a voltaic cell between a pair of electrodes of dissimilar materials to Vgenerate a potential. Movement of well fluid may then displace the electrolyte to vary the potential measured between the electrodes.

While the foregoing apparatus and methods have been fairly satisfactory in detecting water ingress into a producing oil well, each of these systems requires either the application of annexternal source of current or the introduction of modifying fluids into the well bore. Accordingly each requires the use of quite complex equipment in the well bore. Additionally, apparatus constructed in accordance with the prior art has not been directly applicable to the problem of detecting the level at which drilling fluid is lost during the drilling of oil wells by conventional rotary methods. One satisfactory type of apparatus which has been useful in locating the position in a well bore where uid is being lost is disclosed in the copending application of Marshall B. Standing, Harry S. Yaplee and Malcolm Macaulay, Serial No. 105,354, filed July 18, 1949, now Patent No. 2,581,979. However, this apparatus likewise requires means for introducing an electrolyte iluid capable of changing the resistance characteristics of the drilling fluid.

It is an object of the present invention to provide a method of detecting fluid movement in a well bore without the necessity of` introducing electrolyte solutions to change the electrical characteristics of the well fluid.

It is another object of the invention to provide a method of detecting fluid movement in a' well bore wherein it is unnecessary to externally energize a set of test electrodes.

It is a further object of this invention to provide a method and apparatus which is capable of detectingmovement of uid either into or out of a bore hole.

`Still a further object ofthe invention is to provide means for detecting the direction of movement ofwell iluids to determine the elevation in a well bore where uidwithin the borehole is either being contaminated by the influx of water from a formation or the well fluid is being lost to such a formation.

Still another object of the invention is to `provide a simplified method and apparatus for determining the fluid iiow at a pre-determined level in a well bore utilizing a minimum number of electrical cable leads between the testing 'unit and the earths surface.

Briefly, the presentinvention contemplates a method of detecting relative movement of fluid in a well bore by measuring the potential between a pair of electrodes `positioned in the well bore and correlating the direction of movement with the location of the electrode pair in the well bore.

Further objects and advantages `of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing which forms an integral part of the specification.

In the drawing:

Fig. l is a schematic representation of one form of apparatus useful in performing the method of the present invention;

Fig.`2 is a cross-sectional view of a portion of the down-hole apparatus shown in Fig. l. taken in the direction of arrows 22;

Fig. `Il is a cross-sectional view of the apparatus of Fig. l taken in the direction of arrows 3 3;

Fig. 4 illustrates another form of apparatus which may be used in carrying out the method of the present invention; and

Fig. 5 is a bottom-plan View of the down-hole test instrument shown in Fig. 4.

Referring now to the drawing, and in particular to Fig. 1, an elongated housing or casing means, designated generally as |0,.which may be an elongated cylinder or pipe, is preferably provided with threaded ends Il and I2 which are receive an expanded end I9 of a conventional 4 well-logging cable 29. Cap nut 2l is adapted to engage the threads on ilange I1 to secure'. ex-

panded portion I9 of cable 20 to endclosure I5.

As shown, the upper end of cable 20.desirably Y passes, over a pulley member 22 at the earths.

Pulley 22 may be driven by any conventional means such as an electrical motor- (not surface.

shown), and is preferably inter-connected Ito an elevation, or level, recordingmeans to be de-.

scribed hereinafter.

In Vthe embodiment shown in Fig. 1, casing means I is preferably divided into three compartments designated generally as electrode compartments 23 andY 24 and shutter-drive compartment 25. Since vshutter-drive. compartment 25 provides a mounting means 26.for an electric motor 21, a pair `ofend wall members 29 and 39 are arranged to seal on. compartment 25v from the fluid present in the remainder of housing I0 during the operation ofthe equipment. As shown, motor.. 21 may be. energized from .the surface through cable 29 and lines 2,8. It will be noted that the shaft of motor 21 is .provided with a spur gear 3| which is adapted to drivably engage gear 32.r Gear 3.2, is mounted upon shaft 33 which has a semi-circular shutter member :54` positioned atqthe opposite end which isadapted torotate in the hemispherical space delined by end member I5'. Shaft 3,3; is rotatably mounted upon a. concentric, hollow, tubular shaft which interconnects jbore I3. of ange `I1 with compartment 25.V sdthkat the electrical leads 28 4of cable 2l)` may be eni.nreeteri-v to motor. 21.. .One end of Shaft 3.5. is supported; in; bere 36.1.1.1. end. member lfwhile the Aopposite en@ is Supported by ameuninabreeket 3.1- suitably positioned in chamberV 25.

Meter means. 2f' is shown .te Jee` connected 'Y threuehgleads 28,-.cabie-20endrs1ip rinemeans 45 toa source of D. C.potent ial.v B y. this arrangement metery 2.-? is; adanted. to. Continuously drive shutter means; 34: in. the Seme, direction Hewever, it willbfe apparent that switch means (not shown) may be provided so that motor means 21 'may be selectively reversed or stopped. In this the. shutter means-may be positioned in any desired location. Another means for accomplishingr this positioning control ofthe shutter would be to employ a selsyn-type motor lin place of motor 21 for the driving of shutter means 34.

best seen in Fig. 3, a pair of metal electrodes 38V and- 39 which are preferably, but not necessarily, formed of the saine material, are respectively positioned in compartments 23 and 24. These electrodes in turn are insulated from housing I0 and transverse wall 42 by rubber, VBakelite o r similar mounting strips 4 0 and 4I. Electrodes 38 and 3.9, are connected to surface indicating means through-cable leads 43 and 44 which pass through wall 42 into compartment 25 and-then through hollow shaft 3,5 to. cable 20. Cable leads 43 and 44 are thenfconnec-ted through slip-ring assembly 45 to potential, or'rcurrent, responsive Vmeans, such as amplifier 46 and recording millivolt meter 4.1. i

It will be noted that the upper end closure member I5 is preferably provided-with a pair of openings designated generally as 48 and 49 which v I6. .'49, pass Vthrough chamber 24 and thus through Vthe test instrument.

In the operation of the embodiment shown in Figs. 1 to 3, it will be apparent that housing I0 may be lowered by means of cable 20 and pulley 2.2 into a well bore in which it is desired to detect the movement'of fluid. As contemplated by the present invention, the testing of the directionof-luid movement is normally conducted with the well shut in, that is, when iiuid is neitherr being added nor withdrawn from the well, and only the normal hydrostatic pressure, or head, exists atthe top of the well. However, under these conditions there may be a displacement of normal-well fluid due to therpressure existing' in a formation traversed by the bore hole being either higher'or lowerV than thepressure in the well opposite that formation.V When the condition to .be remedied is that of lost circulation, the well fluid will move downwardly from thetop of the well to the lower pressure formation to which duid is being lost. At the same time, there will be virtually no movement of fluid in the bore below that level.

Conversely, when Water is entering a producing well or a bore hole either through a break in the casing or from a higher pressure formation in an Accordingly, in either case it is desirable to locate the level where relative movement of' well iluids Voriginates under such static. or shut in well .Conditions p Forthe purpose of detecting this relative move- -ment of well fluid, we have found that a pair of electrodes, such as electrodes 38 and39, may be Y selectively subjected to the relative movementA of the-'well fluids and that movement Vmay be detectedthereby when only one of the electrodes is placed in themoving fluid stream, while the other electrode is merely in conductive relation to the same iluid stream, but not subjectedl tothe move- Vment of liuid particles over the electrode. Accordingly, in the embodiment shown in Fig. 1, 4 means are provided for selectively permitting well `fluid to pass through chambers 23 and 24 while maintaining both chambers in communication with the well fluid so that electrodes 38 and 39 are continuously in conductive relationship. to each other aswell as to the well fluid. 'Ihis is accomplished by energizing motor 21 which in turnV rotates the shutter means 34'to successively open and' close passageways, or ports, 48. and 49. With shutter 34 Yin the position shown in Fig. 2, it will be apparent that fluid may flow in the direction ofthe. dotted lines in Fig. 1. Under this condition there will beA substantially an equal flow of -fluid through chambers 23'. and 24, and consequently, there will be substantially no potential generated between the electrodes 38v and 39. However. when' shutter means 34 is rotated counter-clockwise 'from the position shown in Fig. 2, so that port 48 will be substantially closed, then, only electrode 39. will be traversed by uid passing throughv the housing I9. .When this ocasse-.437'

curs, we have found that the potential of electrode 39 changes with respect to electrode 38, and accordingly a potential difference is created between the two electrodes. This potential is found to exist even when both electrodes are of substantiallythe same material. While we are not presently sure of the exact reason for the generation of this potential, it is believed that this electrode potential is created in thefollowing manner.` When an electrode is placed in a fluid which is atleast partially conductive, i. e. containing some free ions, the electrode develops a potential dependent upon the concentration of ion species involving or affecting that-electrodesreaction with the surrounding liquid. Especially is this electrode potential dependent upon the concen` tration of that ion species very close to the electrode surface. Accordingly, even a very low velocity flow over the electrode surface results in a change in this ion concentration and produces a change in electrode potential. `The magnitude and direction of this potential change is dependent both on the nature of the liquid and the electrode metal. rWith such metals as zinc, brass, copper and silver as electrodes, this potential change is in the order of millivolts for a liquid velocity of a few feet per minute.

It will be apparent that when the shutter means A 34 is rotated to such a position that both ports 48and49 are closed, there will again be substantially zero potential generated between the electrode pair. However, upon continued turning of shutter means 34, port 48 is opened so that fluid may ilow through compartment 23 and hence over electrode 38. In this way, electrode 38 changes potential compared to electrode 39 and accordingly reverses the direction of the potential transmitted to indicating means 41.

Referring now to the embodiment illustrated in Figs. 4 and 5, it will be noted that an openbottomed, bell-shaped housing 58 is provided with a flange 5| adjacent the closed end. Flange 5I in turn is provided with exterior threads 52 which are adapted to engage with a cap nut 53. Preferably flange 5l has a central bore 54 into which expanded end 55 of cable 56 is adapted to fit and thereby provide means for lowering and raising the housing 58 within a well bore. Cable 5B is supported preferably by pulley 51 which may be rotated by any conventional prime mover.

Housing 58 may be formed by deep drawing a metal blank to form the bell-shaped configuration. If housing 50 is formed in this manner, it is necessary to insulate band, or ring type electrode 58, from the housing by means of rubber sleeve 59 which may completely surround the exterior of housing 5D. For the purpose of preventing ring electrode 58 from contacting the walls of the well bore or the well casing, sleeve 59 is preferably provided with a recessed portion into which electrode 58 fits.

In order to place the other electrode of the necessary pair in electrical contact with the Well fluid, but not subject to contact with the flowing` liquid, electrode 8| is mounted upon an elongated insulating bushing 62 inside housing '58. To further insure that electrode 6l is in-a quiescent location,` housing 5|] is preferably provided with a side wall which is at least as long as the diameter of the housing 50. As best shown by Fig. 5, the lower or open end of housing 5U may be further protected from the possibility of eddy currents due to liquid flow over housing 50 from sweeping the interior of the housing'by an eggcrate, or honey-comb, straightener 63. Since the 6 housing is adapted to be lowered in the well bore with the closed end of the housing in an upward position, it is essential that well fluid vbe permitted to enter the interior of housing 50 so that the fluid may make electrical contact with electrode Bl. For this purpose, a small bleed hole, such as bore `64, is provided adjacent the upper or `closed end of housing 50. However, the diameter of bore 64 is so proportioned that there will be no appreciable fluid flow through housing 58. To insure this, electrode 8l may be positioned, as

` shown in Fig. 4, near the center of cylinder 50,

away from bleed hole 64. Alternatively, the housing may be filled with a conducting solution prior to its introduction into the well bore. Likewise,` "it is possible to cover the lower or open end of housing 5U with a permeable membrane, such as fritted glass or porous porcelain, and then fill the housing with an electrically conducting fluid which may or may not be of the same cornposition as vthe well fluid. As stated above, electrodes 58 and 6l may be constructed either of similar or different materials.

It will be apparent that electrodes 58 and 6i are connected through leads 65 and 66, respectively, and cable 56 toa slip ring arrangement 51 in the cable winding drum. In this manner the electrodes may be connected to an amplifying means B8 and a recording millivolt meter B9. A chart drive means for recording the output of millivolt meter 69 is provided by a reduction gearing 10 connected to the drive shaft of pulley 51. By this arrangement, a chart 1I is positioned in accordance with the position of the housing 58 within the well bore, so that changes in electrical potential between electrodes '58 and 6 1 at that level may be recorded and correlated with depth.

In operation of the embodiment shown in Figs. 4 and 5, it will be apparent that electrode 6| is in electrically conducting relationship to the well fluid, but in a quiescent zone. At the same time, the movement of fluid over electrode 58 creates a potential difference between the two electrodes wholly dependent upon the relative velocity of fluid passing over electrode 58, as explained hereinbefore. In this embodiment, when the housing 50 is positioned at a predetermined level in the well, any movement of well fluids over electrode 58 will produce a potential difference between the electrodes which may be indicated by meter means 69 and recorded on chart 1|. While such movement of fluid over electrode 58 will not indicate the direction in which fluid is moving, this may be determined by moving the housing either upwardly or downwardly relative to the original pre-determined position and noting whether the potential difference increases or decreases when such movement of the housing is made.. If the potential difference increases; it will be apparent that the direction of flow of the well fluid is opposite to the movement of the housing. On the other hand, if the potential difference decreases, the movement of the housing is in the same drection as the movement of the fluid due to the reduction in relative velocity between electrode 58 and the well fluid.

` Onemethod of operating the apparatus shown in Figs. 4 and 5 is provided by driving pulley 51 at a constant, predetermined speed to either lower or raise housing 50 through the zone of the well bore which is` to be investigated. At this constant velocity, changes in direction of potential will be noted during a traverse of the well bore by housing 50. For example, in locating a zone of lost circulation, the fluid level in the well will progressively move 'downwardly` to that zone.

relative movement between uid iiowing. downv wardly and` the'housing, the potential'will'rise abruptlyy whenfhousing fpasses into a zone where there is no movement of well fluid.A At that point, the depthof theformation to which fluid is being. lost. may` be. identied. Additionally, .it

`willV be apparentv that by notingk the 'rate' of lowering where the potentialapproaches a minimum, this methodV of. operationl permits the exact deter-J mination ofv the 'velocity of the" well fluid in the bore hole. `Y f From the foregoing, it will be apparent that, broadly, there haveV been 'established diierent relative vvelocities or movements of the well iiuid with respect to one electrode than tothe other f electrode, andthe potential diierences thusrpro.- duced vare indications of the direction and magnitude of .the relative uid velocities.

While a theory of operationv of the present invention has been set forth hereinabove, it is not our intentionV to limitv the invention to the correctness ofV that theory, but rather, the best methods.r and apparatus for Vcarrying out the. objects ofthe invention, irrespective of the merits of` that theory, have been described in f ull in accordance with the patent statutes Y l From the foregoing description ofthe two distinct embodimentsV of apparatus which maybe employed in the. practiceofrthe method of the present invention, it will be apparent to those skilled. in` the` art that numerous modilications and changes may bemade in such apparatus without. departing.` from the teachings .of the invention. Accordingly, all suchmodificationsk and changes as fall. within'the scope of the appended claims are thereby intendedv to b e included.

rWe claim:

l/A 'method of detecting` the movement`r of Y ilvuids. in a well. borecomprising the steps o f posi-f tioning a pair of electrodes in said well-V and in electrical contact with said fluids, establishing adiiere'nt relative movement of saidy fluid with respect to one electrode than to the otherelectrodefand. measuring the electricalV potential generated betweensaid pair of. electrodesdue to said relative movement as an indicationof the direction offlow of said: fluids in said well.

2. A method of determining the 'direction of fiuid yiiow ina .well bore Vcomprising'. the steps of Vlocating Vat least aA pair, ofA electrodesin said well bore Yat a zone wherethe direction "oi Iiow. is to be4 determined, saidelectrodes being in electrically conducting.Y relationship to. the. fluid, in said borei'establi'shing a l'different relative movement of one of said electrodesl than the otherof. said electrodes with respect to said-'huid while, said uid and one. of: said electrodes are movingisubstantially vertically with respectJ to `each other, and measuring the change. in electrical potential between said pair of electrodes generated by said relative.l movement whereby the directionvof. .llow of said fluids in said well. may be` determined.

3. A methodA of deteetingthe movement of electrically conductive, luidin' a well4 bore. comprising the stepsI o tpositioningf. both of a pair of elec,-v

en desde."

49Al method ot detecting themovement o fl fluids. in a wellY bore comprising the steps o f Positioning o Poirfoi electrodos ooiistruotod of,

Siilstoiiftisliy. thol somo. material' at, oY predeterminedzone in saidwell and-in electricalcontact iii/"ith` saidv iluids, successively exposing first o ne oodthoii both electrodos to, woifiiiid moving. relatively thoioto, oiidvdotorminiiis tho.v potential difference Abetween said ele ctrodes when only.

saidL one lectrode is exposed to said owingfluid and when both of. saidelectrofdes aifeso exposed to, dotoiioioo. thofdirootion of flow ot soidi Prodotoiiiiiriodoooe.

Vd Asteroids. forloootirie tho level in o.. boro,

hole where fluid isentering Ao r leaving saidl b ore hole-comprising andelongated housing adapted; to DQDDSOned il? Said b oe hole' longitudinally. @X1 tending wall means within said'housingdelining a.`i..1e3SUaDa1`.Qf Qhmbers end ClOSllefQl- S@ housing having openings-therein communicatingwith seid Chambers, shutter mosiisfor solootively Qpezing and QlQSIlg Siid; endllsllretp REY/ent flow, of: duid through. orio of, said Chambers; and roriii-itiioid iioW throushoiiothor ofsold. cham,- bois.A electrodo mooiisoositioiiod in oooh offsaid chambers, means lconnecting 'said` electrodes to a potential responsive means at the surface whereby the, diiootion of fluid now Ywith rosseot .tossici olootrodos maybe measure. f

6. ApparatusY for `locating the level in a'well bore where welliluidisV being` lostto an earth formatienv comprising causing means. constructed andarranged to be positioned in said well bore, oofblsmoaos iol' lowering; and raising` said cosine, vertically, extending passageway moons, within said cosine. on. electrodo positioned within, each of Sold .passageway VrriofiiisL said electrodos boing, oorioootodthrough said oablemeonsto, potential indicating moans et, tho ooiths siilfooo. sind moons-.-foifssolootiyolyopening ono and closing anotherv of said passoeeways to osrmituid idowiiis downwardly in said wollv boite altmateix to traverseV said` passageways and be retained'therein andY contact said electrodes whereby the movemoiitofilid'fiow'may be detected asapotential diierence between said electrodes. 7; An.` apparatus for detecting the-movement; of electrically conductiveuid in awell bore, comprising aw pair of'electrodes adaptedtojbe lowered iiito. soiduboio. ooblo modos for supporting seid electrodes and having a separate conductor -fpr each` electrode, one of said electrodes being xposed to,V well fluid. moving relatively thereto, means for selectively isolating a quantityof-uid in` electrical' contact with the other electrode from motion relative thereto and froml fluid flowing.insaid bore, andpotential responsivemeans connected to. said conductors for measuringfposaidicasing inj a well bore, avfrst electrode mounted. within said casing adjacent the closedY end thereof to. prevent. iiuid flowing over. saidcasing from flowing over. said electrode, means ,forad mitting fluid to said casing through said open end to place said first electrode in electrical contact with said well uid, a second electrode mounted on said casing exteriorly thereof and electrically insulated therefrom, means for lowering said cable and said casing at a predetermined rate, and indicating means connected to said electrodes whereby the potential between said electrodes may be measured when said fluid and said casing are moving relative to each other.

9. A method of detecting the movement of electrically conductive fluid in a Well bore, comprising the steps of positioning both of a pair of electrodes in conductive relation to said iiuid, establishing a diierent relative movement of said fluid with respect to one electrode than to the other electrode, and measuring the resultant potential difference between said electrodes.

GHJSON H. ROHRBACK. ROBERT A. STONER. MALCOLM MACAULAY. WILLIAM T. CARDWELL, JR.

` REFERENCES CITED The following references are of record in the 10 iile of this patent:

UNITED STATES PATENTS Number Name Date 2,184,338 Ennis Dec. 26, 1939 15 2,388,896 Aiken Nov. i3, 1945 2,475,353 D011 July 5, 1949 2,517,603 Silverman Aug. 8, 1950

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