US2581979A - Method and apparatus for locating well fluid loss - Google Patents

Description

1952 M. B. STANDING ETAL, 2,581,979

METHOD AND APPARATUS FOR LOCATING WELL FLUID LOSS 2 SHEETS-SHEET 1 Filed July 18, 1949 RECORDER INVENTORS 1 Marshall B. Slanding -'Harry S.Yaplee Malcolm Macaulay FIG. 3

ATTORNYS METHOD AND APPARATUS FOR LOCATING WELL FLUID LOSS Filed July 18, 1949 Jan. 8, I M. a. STANDING ET AL 2 SHEETSSHEET 2 INVENTORS Marshall B. Slanding Harry S Yaplee Malcolm Macaulay 'A ATORY Patented Jan. 8, 1952 METHOD AND APPARATUS FOR LOCATING WELL FLUID LOSS Marshall B. Standing, Harry S. Yaplee, and Mal- 1 colm Macaulay, Whittier, Calif., assignors to California Research Corporation, San Francisco, Calii'., a corporation of Delaware Application July 18, 1949, Serial No. 105,354

8 Claims. 1

This invention relates to a method and apparatus for investigating liquid flow conditions in deep wells, such as oil wells, and particularly refers to the location of a formation intersected by the well bore through which liquid from the bore is leaving the well.

The rotary method of drilling wells utilizes a circulating liquid, commonly designated "mud fluid, made from water, a gel material to impart viscosity and thixotropy, and a finely-divided substance of high specific gravity to give added density. When a large quantity of fluid is lost from the well bore into the formation so as to reduce materially the returns to the surface, the condition is generally designated "lost circulation. This may occur either at the bottom of the hole, for example, when the drill bit first penetrates avery porous stratum, or may occur at points along the well bore due to failure of the mud to form an adequate seal against porous formations. The location of this point of lost circulation by presently available procedures so that remedial steps may be taken, for example, cementing or the like, is time-consuming and costly.

It is an object-of this invention to provide an improved method and apparatus for investigating the flow of liquid, usually drilling mud, in a well from which the drill pipe and bit have been removed, and from which liquid is being lost to a formation penetrated by the well bore.

Anotherobject is to provide a method and apparatus which will give a positive indication at the top of the well of the interval at which mud fluid is being lost from the bore, by introducing a restricted quantity of a liquid which may be designated an electrolyte, having a different electrical resistivity from the liquid in the well bore, and observing whether or not it travels downwardly from the point of introduction.

Another object is to provide an apparatus for controllably introducing into the liquid already present in the well a separate restricted quantity of electrolyte having dissimilar electrical characteristics and at the same time continuously measuring the electric resistivity of the well fluid at points both above and below that at which the electrolyte is introduced.

These and other objects and advantages of this invention will be further apparent from the following description of an example and from the attached drawings describing and illustrating the method and apparatus as applied to locating a zone of lost circulation in a well.

In the drawings, Figure 1 is a diagrammatic 2 longitudinal sectional view of a well in whichis placed an example of apparatus for carrying out this procedure. Figure 2 is a longitudinal sectional view of the upper portion of the liquid-releasing and resistance measuring apparatus shown in Figure 1. Figure 3 is a longitudinal sectional view of the lower or electrolyte storage portion of the apparatus shown in Figures 1 and 2. Figure 4 is a connection diagram illustratinga form of valve control and particularly the power supply signal-generating and signal-transmitting equipment, which comprises the electrical components of this example.

Referring to the drawings and particularly to Figure 1, reference numeral l0 designates a con-.- ventional well bore, the upper end of which is cased at H and the lower end of which extends downwardly through subsurface formations designated l2, l3 and It. The drilling and hoisting equipment therefor is not illustrated, but the well is designated as standing full of drilling fluid l5, which may be a slurry of clay, water, weight material, and, in some cases, viscosity-modifying chemicals such as phosphates, tannins and the like. Various non-aqueous or oil-base drilling fluids may also be employed. As stated above, one purpose of this drilling fluid is to form a thin, impervious sheath or cake l6 along that part of bore I0 below casing I l.

In this example, that part of sheath l6 opposite a highly pervious or even fractured or cavernous formation I3 is insuflicient to prevent water or drilling mud from flowing outwardly into formation l3 under the hydrostatic head existing on drilling fluid I5 in the well and from that portion of the body of drilling fluid which is above the point or interval of "lost circulation. In order to identify which formation is receiving the fluid, the locator device generally designated I1 is lowered into the well on a multi-conductor insulated. cable after the drill stem and bit are removed, and is sequentially positioned opposite various strata to determine where the slow downward flow of the drilling fluid ceases,-du to'outward leakage into the formation. At all points below this interval, the drilling fluid will be static, and this condition will be positively indicated by the method and means to be described. I

The upper end of multi-conductorcable It passes over a pulley or hoisting mechanism l9 and leads through a recording device generally designated 20 to a control panel 2| in which certain of the circuits to be described below are contained for controlling the operation of the locator I1, and for indicating the electrical conditions in 3 the body of drilling fluid I5, to which it is adapted to respond.

Referring to Figures 2and 3, the locator I! there shown consists of a generally cylindrical member 22, to the upperand lower ends of which are threaded metal tubes 23 and 24, respectively, to form a housing. Each of these last-named tubes is covered substantially throughout its length with an electrically insulating coating 25 and 26, respectively, for example, rubber or Neoprene, suitably bonded to the tubes. Desirably, but not necessarily, the inner surfaces may also be so coated. The upper end of tube 23 may be threaded as at 21 and provided with an upper cap 28 to secure a closure or head 29 to tube 23. Electrical connecting means of any desired type generally designated 30 to receive the lower end of multi-conductor cable l8 are secured to head 29 by a second cap and. sealing means 3|. The bottom of lower tube 24 is desirably closed by an end member 32.

Within the lower tube 24 and extending downwardly from member 22 is a cylindrical liner 33 through which a sealed piston 34 is adapted to move under the force exerted by a helical spring 35, the latter centered on a stud 36 on the upper face of member 32. A liquid passage 31 leads upwardly from the space above piston 34 in liner 33 to a T .38 threadedly connected to the top of member 22. The side outlet 39 of T 38 is provided with a check valve 40, the inlet of which is accessible from outside of upper tube 23 throu h port 4| in that tube. By the arran ement -just described, it is possible to introduce through the inlet of check valve 40, T 38, and liquid passage .31. a quantity .of' liquid electrolyte 42 into the space above piston 34 in liner 33 against the force exerted by spring 35.

The upper end of T 38 is connected to an enclosed solenoid-actuated valve generally designated 43, the outlet of which leads through tube 44 to a liquid passage 45 in member 22. A plurality of radial passages 46 leads from passage 45 to circumferentially spaced distributors 41 mounted in an annular recess 48 surrounding member 22. By this arrangement, when solenoid valve is actuated, the liquid 42, which is maintained under pressure by the piston and spring arrangement just described, is discharged slowly through distributors 41 into the space surrounding the locator l! at substantially the midpoint of the latter. Ports H and II i in tubes 23 and 24 permit well. fluids to enter the housing and maintain hydrostatic equilibrium inside and outside the latter.

Liquid electrolyte 42' is chosen to have a substantially lower electrical resistivity than that of the aqueous or non-aqueous drilling fluid I! present in the well bore H), but is desirably of substantially the same density and viscosity and of such a chemical nature that it will not flocculate or otherwise modify the properties of the drilling fluid into which it is introduced as just described. For example, if the drilling fluid has a specific resistivity of from 100 to 400 ohmcms., the resistivity of the liquid 42 is desirably adjusted to be from to 50 ohm-ems. A specific example of a formulation is given below which proved quite successful in locating a zone of lost circulation ina well at Montebello, California, using a clay-water mud to which large quantities of swelling bentonite had previously been added in an attempt to plug the porous formation. After locating the lost circulation zone, it was cemented and circulation was estab- 4 lished without difficulty. The electrolyte in that case consisted of the following materials in the proportions given:

Parts by weight This electrolyte had an electrical resistivity of approximately 30 ohm-ems.

It will be appreciated from the foregoing that if locator I1 is positioned at a predetermined point in the well and the drilling fluid i5 is bein lost through a lower formation, the electrolyte 42, which is ejected in a restricted amount and during a short period, will form a substantially annular sheath around locator l1 and will be carried downwardly along its outer surface by the motion of drilling fluid i5. If the locator I1 is below the point at which the circulation is being lost, the slug of electrolyte will remain substantially at the point of ejection from the distributors 41, due to its comparable density and viscosity.

In order to determine electrically the direction of travel of this liquid sheath, upper electrodes 49 and 50 and lower electrodes 5i and 52 are positioned in electrical contact with a short length of the well liquid and around the insulating coverings 25 and 26, respectively, of locator H, the electrodes being desirably equidistant from distributors 41. Separate insulated leads generally designated 53 are provided from each of the electrodes and are connected to corresponding insulating bushings generally designated 54 in the cap 55 of a fluid tight housing 56 positioned in the upper tube 23 of locator l1. In addition to providing electrical connections for electrodes 49 to 52, inclusive, a pair of such insulating bushings are also provided for the electrical connections 51 of solenoid valve 43 described above.

Figure 4 illustrates a connection diagram and a desirable example of control and signal transmitting circuits, most of which may be contained within housing 56, with suitable connections to cable M which will transmit the controlimpulses and the resulting signals to recorder 20 at the top of the well. Letters A, B, C, D, E and F represent the several conductors in multi-conductor cable IS, with the. portions above the broken lines in each of the conductors indicating that part of the circuit connected to the recorder 20 and the control panel 2! at the top of the well through cable .18. -'Ihe remainder of the equipment connected to conductors A, B, C and D, as well as that connected to electrodes 49, 50, 5| and 52 is adapted to be inserted in housing 53 of locator l1.

As indicated'in the drawing, a source of DC potential is applied as an operating source for the equipment through conductor C which in turn is connected'to line 58. While not shown in the present arrangement, it will be apparent that through a suitable resistance, the heater voltages for the various tubes may be provided from line 53. Since it is desirable to use only AC across theelectrodes 43 and 50 or 5| and '52 to avoid the polarization effects that would result it direct current were used between the elec-- trodes, an alternating current generator, such as an oscillator, indicated generally as 59, is proatone-1e vided by tube 88 which is of thepenio'de type and a phase inverting network provided by resistors 8|, 82 and and condensers 84, 88 and 88. By the proper proportioning oi the condensers 84-, 85 and 86 and the resistors 8|, 82 and 83. tube 88 may be caused to oscillate in a manner well known in the art since the plate 81 and grid 88 of tube 88 will be substantially 180 out of phase. In order to provide the desired operating potential to the screen grid 2 and plate 61 of the tube, resistors 89 and 18 are respectively provided for connecting the screen grid and the plate to the source of DC potential. As shown, grid biasing is provided by cathode resistor 1| and a by-pass condenser 12 is provided between cathode 13 and the circuit ground which is isolated from the housing of locator I1 and returned to the surface by conductor D to avoid polarization efi'ects. In order to amplify the output of the alternating current signal from tube 88, the output of plate 81 is coupled tothe grid 14 of tube 15 through the coupling condenser 88. Tube 18 is likewise of the pentode type and is provided with grid biasing by cathode resistor 18 connected between cathode 11 and ground.- Plate 18 of tube 15 isconnected to the primary winding 19 of a power output transformer 88.

Secondary windin 8| of the output transformer 88 is connected across the terminals of a Wheatstone bridge circuit comprising impedance elements, such as resistors 82 and 83 and the impedance of the well fluid measured between electrodes 99 and' 58 and 5| and 82. The interconnection from secondary 8| of transformer is provided by line 84 which is connected to a common point between resistors 8-2 and 83. Likewise, line 85 is connected between the other side of secondary 8|, and both of the top electrodes 49 and 5| of the upper and lower pairs of electrodes respectively on the locator I1. Since the output of the opposite pair of terminals of the Wheatstone bridge circuit formed by the electrodes and resistors 82 and 83 may be relatively small, the output is connected to suitable amplifying means through the primary winding 88 of transformer 81. Secondary winding 88 of transformer 81 is in turn connected through two stages of amplification provided by tubes 89 and 98 to the primary 9| of output transformer 92. In order to provide the desired amplification with a phase shift of 180 between the secondary winding 88 of transformer 81 and the primary 9| of transformer 92, primary winding 9| is connected between the cathode 93 of the tube 98 and ground instead of through the usual plate grid coupling as between tubes 89 and 98. The resistor and condenser couplin between tubes 89 and 98 are proportioned to obtain a.zero phase shift of the signal between the tubes and thereby -maintain the desired 180 phase shift produced by tube 89. The purpose of this 180 phase shift through the amplifier will beexplained more fully hereinafter in the description of the operation of the circuit. I

, In order to provide a reference AC voltage to the outputof the circuit, transformer-94 is connected with its primary winding 95 parallel with secondary winding 8| of transformer 88. Secondary windings96 and 91 of transformers 94 and 92, respectively, are connected to synchronous rectifier means'indicated generally as 98. Synchronous rectifier means 98 preferably comprises a pair of rectifiers 99 and I88, a volt- 8 age-dividing potentiometer |8I ,and an impedance element, such as resistance I82 having an impedance approximately equal to the impedance of secondary winding 91, to which are connected the operating Ivoltages obtained from secondaries 98 and 91 of the two transformers 94 and 92, respectively. For balancing potentiometer I8| when there is no input signal from the amplifying means, an adjustable center terminal I89 isconnected to one side of secondary 98, opposite the common connection of resistance I82 with secondaries 98 and 91.

As shown in the drawing, indicating means such as a DC zero center meter I88 is provided across the terminals of rectiflers 89 and. I88 and the potentiometer I8I. It will be apparent that meter I84 is only representative of the recorder Indicated generally in Figure 1 as recorder 28.

Operation ofthe circuit is as follows: Before electrolyte 82 is introduced into the well'by momentary actuation of the solenoid. through operation of the switches in lines E and F, the resistance between electrodes 49 and 88 is approximately equal to the resistance between electrodes 8| and 82, and since the resistors 82 and 93 are selected to balance the bridge circuit pro vided by these resistors and the resistance of the well fluid across the. electrodes, there will be a zero voltage generated across primary 88 of trans.- former 81, and accordingly there will be no voltage across the secondary winding 91 of'transformer 92. Thus, the only current flowing through synchronous rectifier .98 is that produced by the current flow through transformer 98. Due to the reference potential obtained from transformer 88 and by properly positioning center terminal I83 on potentiometer |8|, it will be apparant that the current flow through the left-hand portion of potentiometer |8I andthe right-hand portion of the potentiometer will the equal on opposite half-cycles of the alternating current and the current through meter 184 may be arranged to read zero under these conditions. However, when the slug of resistance modifying liquid has been introduced into the well and permitted to flow in accordance with the direction of flow of the circulating'fluid, it will be apparent that a change in the impedance, or resistance,

between one pair of electrodes, say BI and 52,-

may be reduced sufficiently below the impedance, or resistance, between electrodes'89 and 88 to cause a greater amount of currentto flow in the lower arm of the bridge; Under these conditions the primary 88 of transformer 81 will be energized with an alternating current potentialeither in phase with that of secondary-8| of transformer 88 or out of phase with secondary-8|; -The direction of polarization of transformer 81 will be dependent, of course, upon the resistance characteristics of the fluid introduced into the well bore and the resultant output will be determined by the sameproperties'." The output signal from the electrodes, of course,'=app'ears across the secondary 91 of'transformer 92, and it will be noted that secondaries 98 and 91 of transformers 92 and 98 are connectedin series across rectifier 99 and the left-hand portion of potentiometer |8| through the center terminal connection, I83. In this way it is possible for the signal derived from the electrodes to-be either in phase with the. reference voltage from secondary 98 or 188 out of phasewith this voltage, thereby causing the signal across the left-hand portion of potentiometer |8| to be either in- *slst eti p i s creas'edby' the additive'factionpf the signal volt- {age froin transformer 92 ordetaeased, depending upon theflirection of flow bf the=iiuid between the electrodes. 11, *foij example,fit-"is assume:i that the direction of the instantaneous A. C.

pulses through the-transformers are as shown the drawing, it apparent that the po- '=te'i1tial'ac'ross'thefleft handportibn of 'IDI will be decreased and hencethe D. ottoman across meter I will be such'tiiat'ciirrent' flows from B 'to'h' thi'ough 'th'meter; 'EQn'the other hand,

ifthe-"poteritial" appearing atfseoondary winding '01 r tramm mer ez-is-fir' fpna 'ewith that nowing throu'fg'h winding ,Qfifth'ecurrent across the left an section or potentiometer t will be increased and the voltage across the right-hand w h! qit he me awa ts-W 11. b greater t fi .8 fil lm q jhe transforiner 92.

nenca m pow 'b' froiriterininal a to terminalBandthe direction of fl'ectiifin' of meter [Ill will be reversed; It w ll, therefore be apparent that the deflection ofjthemeter' will b an' indi- .[I n indica n p 'thgratewoflfiowjof the elec- 'olyte is? aesiredsue i'r'itervjal between' the ,nera 'qnlqi efiqidract et diyalve. a d the deflection; of. meter. .j u ay, be "measured, and 'diyid'ed h'y' the distahcefbetweenj distributors .41 Land th'lelectrodes. n

wmie further, modiilcat'i ohsiand changes will be appareiit toitli ose skilled the art, all such 'inodiflcationsandbhang that fallwithin the of }.the'. appended claims are' embraced applfatusJordetermining-that -.location is; welljatl lwhich fluidfisfbeingI-lost .to 'a formation including an elongated housing having a noneconducting outer forat least a porii f?! t a ndaflerted. t qw r n ls-Pr a multi-wadscter, --.in a a l m ans forminga liquidreservoip-in said housing, liquid m su slms new n -r se a 1 1 9 wfletint med a tee-e dea i housmg! E P QW i Z Q d u let, an electrically,aotuatedyalye-in said passage,

ai a l a ep e t b ctua ed-t o said .cablato release;.a,ch arge f liquidfrom said insylatedgleetrodes on said 1 v side'ofsaid liquid outlet, and tricalmeansiri housing connected to said' electrodes .seid cable for converting ghanges, in electrdcagl refsistance between either 'p'ffsiiid electrode pairs due to, presence of said e l-$ 38 p ced ii li i h r efih bs i a -931? current signs thr ugh said cable to 'o'f' jell"an z. dicato'rconhle. c. t e a l ,1 in wh h era s a PI Y- s1!- e fi auy emcee-mas. t steam sub,- sfi flai li lsr'c a ss 9 ll iii e ia 3. Apparatus fordeterrpinin 'lhe'location: in a sawbmrri aa n.- s'at s ho si hav n lass Ofifs su s and tw eni t 99 5 113: we .mu tb sl qitl s ble 'Q Y -,-;st e m ns 'sateness r s tiz n an ig elect oly i n-s id ra e-m a FEXQQ eQWPQQ eJmmthes a e mi Sa d eams .?2 :e wt,:0lyte m 881d storage; said holeytwo pairs of electrodes adapted to be bridged-by said electrolyte equallyspaced above and below the point at whiclrsaid electrolyte is expelled, and electrical means for indicating the direction of flow of said electrolyte, said electrical means comprising a source of direct current, and A. C. signal-generator energized by said source, means for connecting said source, means for connecting said generator across the terminals of a bridge circuit including a pair of impedance elements and said pairs of electrodes, amplifying means connected between the opposite terminals of said bridge circuit, synchronous rectifier means having the output of said amplifying means and said generator so connected thereto that the phase of the signals from said amplifying means and said generator may be compared, and indicating means'connected to said'synchronous rectifier means to detect the phase of said amplifying means'and thereby identifythe pair 0! electrodes between whichsaid electrolyte is present;

4. Apparatus for determining the location in a drill hole at which fluid is being lost to a formation comprising an elongated housing having a portion of its surface insulated and adapted to be lowered into said hole'by a multi-conductor insulated cable, electrolyte storage means within said housing. pressurizing means for expelling electrolyte from said means, relay means actuatable from the surface to permit said pressurizing means to' expel electrolyte from said storage means into" said hole, two pairs of electrodes equally spaced above and below the point at which electrolyte is expelled and adaptedto'be bridged by said electrolyte, and electrical means for indicating the direction of flow of said electrolyte, said electrical means comprising an A. C. signal source, means for connectingsaid generator across a bridge circuit including said electrode pairs and a pair of resistances similar to the resistance of said electrode pairs when bridged by the fluid being lost, amplifying means for the output of said bridge, synchronous rectifier means comprising a potentiometer, a pair of rectifier 5 elements connected to the ends of said potentiometer, and a pair of impedance elements connected in series with the opposite terminals of said rectifiers, one of said elements being an, output load for said amplifying means, said A. C.

signal source being connected between the midpoint 'of said potentiometer and the junction of said impedance elements to provide a phase comparison for the output signal from said amplifyi'ng means, and indicating means connected across said potentiometerto indicate the phase of-thevoltage from said bridge circuit and thereby g t m pair ofhelectrqdes bridged by S id electrolyte- I .5,- -A a paratus, fer determinin h direction Q0 tr m r flu,id. in -a,---well bore comprising an nating current,-- a Wheatstone bridge "connected to-said source -an arm-of said bridge being pro- .videdtby a pair of longitudinally spaced electrodes T0 mounted-upon said housing below said electrolyte introducing means, said electrodes being insulated fromaisaid housing, and. means" for detecting a change 'of impedance-,iri=said' arm -due to said electrolyte flowing" downwardly to bridge said :5 e1ectrodes;'=::.-said' "last -named means including amplifying means, a synchronous rectifier connected to said amplifying means and said source of alternating current so that the unbalanced voltage from said bridge will be in phase or 180 out of phase with said source and potential indicating means connected to said rectifier to indicate an unbalanced condition in said arm.

6. In a method of testing a well from which there is a movement of liquids out of said well into a formation through which said well passes. the steps of introducing into the liquid in said well at a predetermined level a restricted charge of an electrolyte fluid having a viscosity and density substantially the same as the liquid already in said well to vertically displace a volume of said liquid with said electrolyte fluid, said electrolyte fluid having an electrical resistivity differing from that of said liquid, continuously measuring the electrical impedance of a volume of liquid at a level below said predetermined level and recording the measurement of said impedance to indicate the displacement of said well liquid by said electrolyte fluid and thereby detect movement of said well fluid with respect to said predetermined level.

7. A method according to claim 6 in which said introduced charge of fluid has an electrical resistivity of less than about 25% of that of the well liquid.

8. A method according to claim 6 in which said introduced charge of fluid has an electrical resistivity differing from that of the well liquid by a factor of not less than four.

MARSHALL B. STANDING. HARRY S. YAPLEE. MALCOLM MACAULAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Kinley June 5, 1945

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