US2414862A

US2414862A - Well surveying apparatus

Info

Publication number: US2414862A
Application number: US352815A
Authority: US
Inventors: Fearon Robert Earl
Original assignee: Well Surveys Inc
Current assignee: Well Surveys Inc
Priority date: 1940-08-15
Filing date: 1940-08-15
Publication date: 1947-01-28
Anticipated expiration: 1964-01-28

Description

Jat 28, 1947. R FE-ARON 2,414,862

WELL SHURVEYING APPARATUS Filed Aug. 15, 1940 4 shee'ts-sneet Jn. 28, 1947. F`EARON 2,4I4,862

WELL SURVEYING APPARATUS Filed Aug. 15, 19440 I 4 Sheets-Sheet 2 Jan. 28, 1947.' R. E.`FEARON 2,44',s62

WELL SURVEYING APPARATUS Filed Aug. 15, 1940 4 Sheets-Sheet 3 a& /07

INVENTOR.

. I i o V %ta ATTORNEYJ' Jan. 28, 1947.

R. E; FEARON WELL SURVEYING APPARATUS Filed Aug. 15, 1940 4 Sheets-'Sheet 4 INVENTOR.

' oeri E Ramiz 3 Www ATTORNEYJ Patenta! Jan. 28,' 1947 2314362 I wEL. suavsma APPABATUS Robert Earl Fearon; Tlsa,kla., asslgnor to a Well Surveys. Incorporat'ed, Tulsa, Ohio., a

corporation of Delaware 4 Application August s, mo, Serial No.-35z,`s5

-, a Claims. (CL 73 -154) This invention relates to an apparatus for' seo-4 Physical prospecting, particularly for obtaining indications of the nature oi subsurface strata lying adjacent an opening in the earth such 'as a dr'ill hole. More speciflcally the present invenability of the strata to absorb heat.

' has been considerably raised or lowered depending upon whether the fluid' is at a higher or lowe temperature than the surrounding strata. Theref after the fluid at that point will not change temperature as rapidiy' as the' fluid at some point removed from the point of entry and the tem-'- 6 tion relates to an apparatus !or diflerentiating perature'of the fluid applied at some point re-' 4 between subsuriace strata on the basis ot the moved from the' point of entry will not'be the same as that oi the fluid applied at'the point Many devices have been proposed for use in oi entry because' the temperature oi' this fluid determining the nature oi strata that lie adja-` 10 will have changed due to its contact with' the cent drill holes and the like without the neceswalls of thedrill hole, prior to its reaching its sity oi' actually sampling the strata and bringing final location. Thiis in the practice of a process 4 the samples to the surface. such devices have such as has been j'ust described numerous diidifl'erentiated between the various strata on the flculties are encountered in attempting to obtain basis of their electrical conductivity, their magaccurate results and is not very satisfactory in netic permeability, their radioactivity, their reacpractice. tions to radioactivity and their reactions to heat. Other apparatuses for determining the temsince the apparatuses vary with the characi perature characteristics of surrounding .strata teristic of the strata upon which they make their utilize means for applying heat at a point in a -distinction it is obvio s that the distinction made well bore and means for measuring the temperaby one device will not always correspond exactly ture rise `at one or more points above or belowto the distinctions made by another device but the point of application oi the heat. This gives this is desirable rather than otherwise since it an indication oi the rate at which heat travels tends to prevent,the same errors from entering through the strata but is afiected considerably by into measurements made by diflerent devices and 2 any longitudinally extending conductor oi heat, 'permits comparison oi the results oi two or more such for example as a well casing or the fluid devices with a resultant gain in information that in the well. i It is also aflected strongly. byany makes the conclusions reached as to the nature movement oi' fluid in the well that tends to carry of the strata at various levels more deiinite and heat from the source to the measuring instru more accurate. It is therefore not the purpose ment. v of the present inventionto provide a device which i There has also beenproposed apparatus which v will entirely supplant all previous well surveying comprises' means for continuously lowering or devices, although the present devices can be used raising in a well bore a source oi heat and therealone with good results and considerable accuh after at a deflnite time interval lowering past the racy, but, on the other hand, it is the purpose of heated areas a 'temperature measuring instruthis invention to provide a device that will give ment that will measure the relative temperature on the basis of the heat absorption characterisdrop between the time of application oi the heat tics of the various strata, an accurate indication and the time oi the measurement. such a device of the nature of subsuriace formations.- gives interesting results but the results are af- Prior to this invention it has been proposed to 40 fected considerably by' differences in temperature measure the heat absorption of the various at various levels within the well bore prior to strata penetrated by a drill hole in several diflerthe measuringprocess, and gives only one tem-V ent` ways. One way was to pump hot or cold liqperature reading for each location which temuid into a well bore and then after an interval, r perature reading is indicative only of the total to measure the temperatures at various levels absorption of heat over a fixed period rather than thus obtaining an indication of the relative raa more complete picture of the rate of absorption pidity of heat radiation or absorption to or from of the heat over a longer period. the fluid in the well bore from or to the sur- Accordingly, the present invention is directed rounding strata. In such 'a process the heat beto an apparatus for measuring the rate of heat gins to be absorbed at first at-the point at which absorption at' a plurality` of points within a well the liquid enters the well bore and by the time bore in such a manner that a more complete pican appreciable portion of the well bore has been ture of the rate of heat absorption is obtained !or filled with liquid the temperature of the strata each location. This is done in a manner that persurrounding the point of entrance of the fluid mits the ready comparison of the measurements made at various levels 'to give the ultimate infor- &414382 mation about the characteristics of the various earth and means for measuring at the same time the temperature changes at each of these points during the applicationof the heat. As a result there is obtained for each point at which'a measurement is made a temperature, temperature change or heat absorption curve for the surrounding strata which curve is characteristically different for difierent types of formations. Obviously, a surrounding casing will change the form of the curve but the curves for various formations will still differ and the formations can be differentiated on the basis of these curves even though a casing is-present.-

It is expedient to supply the heat in the well bore by means of an electrical heating element or plurality of heating elements Suspended in themore of the heating elements and perform the heating in .their particular locality at a higher rate if desirable. for exam le. when it is known that some particular formation has a verv high right magnitude to be useful and yet not get curves of too great or too little a magnitude at other points.

Alonaslde of each heating unit in the well bore is placed an *element that' can be used to measure temperature and each of these is arranged to be connected to a recorder on the surface so that a conti uous or substantia ly continuous record of its fi dings may be made.

Many specific arrangements of detailed systems of armarats may be made to carry ot the rincip es of this invention as herein set forth. These pos ib ities and many advanta es that have not heretofore been mentioned will be ap arent from a considration of the appended drawings and the following detailed description.

Fi ures 1 and 2 taken together constitute `a dia ramma ic illustration of a device w ich .is substantiellv com lete in detail and which is suitable for field work;

Figura 3 is a dia rammatic illustrationpf a p rt of t e device of Figure 2 illustrating a possible mo ification thereof.

Fi ure 4 is a further modification of the present invention which illustrates the use of a 'stop filter between the power pack and the cable.

Figures 5 and 6 taken together constitute a diagrammatic ilustration of a device showing the manner in which varied currents can be supplied to t e heaters through the circuits of Figura: 1 a d 2 and'Fie'ure 7 is a diagrammatic showing of the manner in which the cold .iunctions can be connected into the circuits of Fi ures 1 and 2.

In the fol owing detalled description of the invention reference will be made to the various figures of the drawings in which the same reference characters are used in the different figures to denote the same elements. As illustratedin Figure 1 the-measuring instrument proper consists of a casing 40 adapted to be lowered into a we l at the end of a cable 4I and to have suspended from it a heater element 42 which extends along the whole formation being investigated and a series of thermocouples 43. Thermocouples 43 shown in Figures 1 and 2 and thoseshown in Figure 6 are slmilarly spaced. The cable 4| that supports the casing in the well also serves to convey the heater rate of heat absorption. or a very low rate of heat absorption and it is desired to get curves of the V heater 42.

current through the casing 40 and on downward to the heating element 42. In addition to this, the cable 4l serves to carry to the surface currents indicative of the measurements made to the thermocouple and to bring from the surface to the casing a current that causes a switching mechanism to operate whereby one after another of the thermocouples is selected so that its reading will be transmitted to the surface while the other thermocouples are disconnected so that readings from them will not be transmitted simultaneously.

To accomplish this the individual lead wires from the various thermocouples are connected to the fixed contacts of a selector switch 44 and a lead wire 45 from the movable' contactor of the. i

tinuous wave generated by the oscillator. This wave preferably has a frequency of around 250 cycles but may have any desired frequency instead. From the oscillator 48 the modulated continuou's wave passes through a filter 49 and into the cable 4| which extends to the surface. The filter 49 is of the band pass type passing only frequencies in the immediate neighborhood of that of the carrier current. i. e. 250 cycles.

At the surface as shown in Figure 2 the cable 4i extends over a measuring wheel 50 and is wound up on a cable reel SI driven' by a source of power not shown so as to raise and lower the measuring instrument in the well. The measuring wheel 50 carries a counter 52 attached to one end of its shaft and this counter serves to re iste! the de th to which the measuring instrument is lowered. At the cable reel BI the conductors in the cable 4| are connected to slip rin s 53 which in turn make contact with brushes 54.

A generator 55 is connected through an ammeter 56 to these brushes 54 so that current is sup lied to the cable for the operation of the Also connected to the brushes 54 through a filter 51 is an am l fler 58. The filter 51 passes the same band of frequency as does the filter 49 in the osc llator circuit at the measuring instrument. Therefore the carrier waves generated in the well pass through the filter 51 and thevamplifier. 58.r One lead 59 from the amplifler 58 passes directly to a recorder mechanism 60, and the other lead passes through a sele tor switch Gi to one of five points along a resistanceGZ, depending upon the setting of the selector switch. From whichever point on the resistor receives it the current passes through the resistor `to the other lead of the recording mechanism 60. Across the resistor is a battery 63 which furnishes a constant potential drop across the resistor. A part of this potential is thus in series with the output of the amplifler 58, the amount depending upon the setting of the selector switch SI Thus as the selector switch SI is rotated the potential drop will change in steps, each step causing the needle of the recording mechanism to make a step of movement across the recording tape 64 of the recorder. The recording tape is driven by a clock motor E! so as to correlate the rccordings it makes with time. The recorder is also such a type that the needle will lift from the paper when the circuit is open( sheet together with the same amount of added potential each time a record is made. This causes a separate record, spaced from the others, to be made for each thermocouple.

unwanted current must then be placed in the line between the cable 4| and the power pack 13.

No source of power has been shown on the surface of the earth for the generator s or the amplifler 58 but this would appear unnecessary since it is a simple matter to obtain power from any suitable source on the surface wherepower is so easily This is done by v means of a clock motor 66 which drives the selector` switch 6| in a step by step relation moving it from one contact to the next, allowing it to rest 'for a deflnite length of time and'then advancing it to the next contact. Atthe same tine 'the clock mechanism 66 drives the second selector switch 61, also at the surface, and having its fixed contacts ofiset as compared with selector switch SI so that when the selector switch Gl is closed on one of the fixed contacts the,selector switch 61 is open. Then as the selector switch Gl ro-. tates to the next fixed contact. the selector switch 51 is momentarily closed. All of the fixed contacts of the selector switch 01 are electrically connected together so that when the movable contact member contacts any one of them it merely closes .the circuit to* the selector switch 61.

The closing of this switch places an oscillator` 88 in a circuit through a filter 69 a ross the brushes 54 which lead tothe supporting cable 4 I. The filter sa is constructed so that it will pass a narrow band of frequencies different both from the carrier frequency on which the information to be recorded is sent to the surface and'from the frequency, if any, ?of the heater power. A frequency of around 70 cycles has been found satisfactory for this purpose. 'When the switch 61 is closed the 70 cycle wave is sent down through the supporting cable 4| into the measuring instrument where it is taken from the cable through a filter 'III which is 'arranged to pass that frequency, to an amplifler 'Il and from there to an actuating motor 12 that is arranged to advance the selector switch 44 one position. Thus, every time the clock motor 66 advances the selector switch s on the surface, the circuit completed through the switch 61 also advances the selector accessible. g

Although it is the intention of this inventor to use any or al parameters that may be obtained .by comparing temperature with time by the general methods set forth it has been found that the rate of increase of temperature with' time,-in other words, the derivative of temperature with respect to time is likely to give quite important indications of the nature of the adjacent strata. Therefore there has 'been 'illustrated in Figure 3 a derivating circuit that may be placed between the filter 51 and the ampiifler 58 on the surface of the earth to convert what would otherwise be a measurement 'of temperature to a measurement ,of a time derivative of temperature. This derivating circuit consists of a condenser. 'I4 having a very small capacity connected in series with a resistor 15 having a relatively small resistance, a vacuum tube amplifier 'IS with itsinput connected across the resistor 1 5 and the usual output resistor 11 and output condenser 18. The sources of fllament and plate potential have not been shown since they can be supplied from any suitable source, for example the same source that Supplies power to the amplifler.

Figures 5 and 6 taken together show a modiflcation of a complete surveying system. Figure 5 shows diagrammatically the surface equipment while Figure 6` shows diagrammatically the sub-surface equipment. Generators llll to !05 supply power at difl'erent frequencies through the variable resistors 85 to 89, filters IOS to conductors III and I !2, and the cable 4| to .the heater elements 80 to 84, respectively, through the filters il: to H'I. Theheating elements 80 to 84 inclusive are respectively placed adjacent the pyrometers IS toits, By this arrangement it is possible to separately control the heat emitted by the heating elements. One terminal of each of the pyrometers !5 to 19 is connected to a common conductor 20 which joins conductor 46, that in turn 'is connected to the input of amp'lifier 41. The other terminals of the pyrometers |5 to s, are respectively connected to conswitch 44 in the well one position. The recording measuring instrument itself. This power is sup-' ductors !I to 25. These conductors lead to the selector switch 44. The' contactor of the selector switchis connected through conductor 45 to the other terminal at the input of the amplifier 41.

The amplied signals from ampliiier 41 are transmitted to the surface over the cable 4| in the same manner as described above in connecton with Figures 1 and 2.

In Figure 7 there is shown the manner in which 'the cold junctions can be connected in the circuits of Figures 1 and 2. In this circuitdia-` gram conductor s may be of Constantan or like plied bya power pack 13 of the ordinary type used in radio which power pack gets its original power from the cable 4l, using a part of the power supplied by the generator 55 for the heater element. As a possible alternative the power for this power pack may be supplied at a frequency different from that supplied from the generator 55 and placed in the cable 4l through appropriate filters such as is illustrated at' a in Figure 4. In such a case a filter to prevent the passing of material. The junction a between the Constantan conductor 'and the copper conductors of the rest of the system is made in a Dewar flask !20. The temperature inside the Dewar flask may be maintained colder than the junctions at l2| to 'zs, or it may be maintained hotter, as desired. In this figure, 48' is an oscillator and 48 is the modulator; The amplifler at 41 is obviously a D. C. amplifler, while that at !28 is an A; C. tuned amplifler. g

The surface equipment shown in Figure 'I smesso 7 diifers'further in that a rectiiler R is connected in the circuit after the ampi fler u.

I claim:

v i. Apparatus for geophysical prospecting that comprises a casing adapted to be lowered into a drill hole, a cabe adapted to support said casing in the dril hole and connect the mechanism in said casing electrically with the surface of the earth, means to lower said cable into the earth and withdraw it therefrom, means to measure ment and connected through said selector switch in se'quence, an i'nplifler in said casing to which said temperature responsive elements are sequentially connected, a generator of a fixed i'requency carrier wave diiferent from the frequencies of the alternating current and heater currents already mentioned and modulated by the output of the amount of cable lowered into the earth, an e A elonzated heater element Suspended below said casing in the drill hole, means on the surface of the earth for generating electricaicurrent for said heater element, a circuit conecting said generating means with said supporting cable at the vanced by said receiving means in response to said alternating current, a series of temperature responsive elements suspended below said' casing at various depth: aiongside of said heating ele said amplifler, means for imposing the output of said carrier wave generator on said supporting cable, means on the surface of the earth for receiving and amplifying said carrier frequency to the exclusion of the altemating current and heater currentaIready mentioned, and means, also on the surface of the earth, for recording the temperaure indications superimposed on said carrier fre'quencies in correlation with time.

2. A device as described in claim 1 in which means are further provided for derivating the temperature indications with respect to time prior to recording.

3. A device as described in claim 1 in which means are further provided to variously bias the recording means as it records the temperature indications of the various temperature responsive elements in order to 'cause the recordings to be 'made on diflerent portions of the record sheet 'of the recording means.

ROBERT EARL FEARON.