US2528955A

US2528955A - Radio-activity logging of wells

Info

Publication number: US2528955A
Application number: US774945A
Authority: US
Inventors: John T Hayward
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-09-19
Filing date: 1947-09-19
Publication date: 1950-11-07
Anticipated expiration: 1967-11-07

Description

Nov. 7, 1950 J. T. HAYWARD 2,528,955

RADIO-ACTIVITY LOGGING 0F WELLS Filed Sept. 19, 1947 I 2 Sheets-Sheet 1 Du max-5% 5. 2"

FlG.l FIG.2

F 3 PROGRAM CLOCK. MECH.

IN VEN TOR. JOHN T. HAYWARD Aauk ATTORNEYS 1950 .1. T. HAYWARD 2,528,955

RADIO-ACTIVITY LOGGING 0F WELLS Filed Sept. 19, 1947 2 Sheets-Sheet 2 PROGRAM C LOCK M ECH (I m D 1! Q U m (1 FIG. 5

INVENTOR. JOHN T. HAYWARD ATTORNEYS Patented Nov. 7, 1950 UNITED STATES PATENT OFFICE- RADIO-ACTIVITY LOGGING F WELLS John T. Hayward, Tulsa, Okla. Application September 19, 1947, Serial No. 774,945

Claims. I

The present invention is directed to logging wells drilled by the rotary method in which a circulating stream of fluid is used for removal of the cuttings and, in particular, to the logging of such wells by measuring the radioactivity of the formations-traversed.

Methods for logging wells have already been proposed inwhich measurement of the radioactivity of a formation traversed by the bore hole is made. The method commonly employed is one in which a Geiger-Muller counter is lowered-into the hole. This method has the limitation that in order'to prepare a log of the well, drilling must be suspended and the tools withdrawn from the hole. As this is a lengthy operation and involves expensive-delays, the radioactivity survey is usually postponed until several thousand feet of hole have already been drilled. The present method is directed toward giving a log that is continuously current during the drilling and without interfering in any 'manner with the progress of the drilling operation.

Methods for logging wells by radioactivity and utilizing the mud stream have also been proposed and involve measurement of the radioactivity of the flowing mud stream by placing some sort of radiation detector, such as a Geiger- Muller counter or an ionization chamber, in or adjacent to the mud stream. Attempts along these lines have proven generally unsuccessful in practice for the following reasons: The circulating fluid is composed of water which may comprise 50 to 80 per cent of the fluid and which is obtained from various sources, such as surface supply wells, and which may of itself have considerable radioactivity. In addition, the mud fluid contains various materials that are added to it at the surface in order to give it the weight and viscosity suitable for proper drilling. These materials generally consist of finely divided bentonitic shales, barytes and other mud heaviers, etc, the natural radioactivity of which is usually considerably in excess of the formations being drilled and these materials usually comprise 5 to 20 per cent by weight of the circulating fluid. In addition, the mud fluid contains finely ground material obtained from the action of the bit on formations higher up the hole and which have been circulated numbers of times around the system. These materials also may comprise up to 20 percent by weight of the circulating fluid. Lastly, the circulating fluid as it issues from the hole carries with it cuttings made by the bit in pulverizing the core actually being drilled. These cuttings seldom amount to as much as one I cuttings.

per cent by weight of the fluid. It will be seen, therefore, that upon measurement of the total radioactivity of the mud stream or any unclassified portion thereof, variations in the radioactivity of a formation actually being drilled, since they will only affect less than one percent of the stream, will'be entirely masked by the nonsignificant radioactivity of the rest of the stream.

The principal object of the present invention is to obtain a log of the well as it is being drilled by measuring the radioactivity of only that part of the material carried by the stream which wasadded to it in its last passage past the bit and which consists of an-actual sample of the formation drilled and dispersed in the mud stream as the bit pulverizes the core being drilled. In order to accomplish this, the circulating fluid issuing from the well is continuously screened. The mesh of the screen is so chosen that the materials added at the surface to condition the mud will easily pass through it and only the coarser portions of the core drilled up by the bit, the so-called cuttings, will be retained upon it.

It will be obvious that if the total stream is passed through the'screen before it enters the well, any material retained upon the screen must have been picked up on the last journey through the well. Mechanical vibrating screens are readilyavailable for the extraction of these As an alternative to the screen, or shale-shaker, a large settling pit can be used. In such a pit the velocity of the fluid is low and ample time is available'for the deposition of the cuttings. Inthis case also, therefore, the coarser pieces in the issuing mud must have been picked up during the last trip and if some fraction of the issuing stream is then screened in a device such as that discussed later, material-retained in it must have come from the formation drilled when the corresponding increment of mud passed the bit.

An additional object of the present invention is to provide a methodand apparatus for the production at the top of a bore hole during the drilling thereof of a log of the radioactivity of the formations traversed by the bore hole.

Further objects and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate several embodiments of apparatus which may be employed for successfully practicing the logging method in accordance with thi invention. a

pipe I2 to the bottom of the we'llwhere it passes through'the usual openings in the head of the bit into the annular space between the drill pipe and the wall of the well. As drilling fluid l3 passes the bit it receives the cuttings being currently cut from the formation being drilled by the bit and carries these cuttings upwardly 1 through said annular space and out of the well. through side outlet H. The stream of drilling fluid containing the cuttings is discharged from outlet H and passed in its entirety through a sloping screen 14 of the conventional vibrating type, commonly known in oil field parlance as a .shale shaker." The mesh of screen I4 is selected .to, pass all of the -mud fluid except cuttings. of the desired size, the latter being caught on the upper surface .of the screen which, by virtue of its slope andvibratory movement, will continuously ,dischargethese cuttings, indicated at I5, from off the lower end thereof and cause them to collect in a suitable receptacle I6 positioned below the lower end of the screen. The cuttings l5 thus collectedin receptacle l6 are thereby made available for further handling in the mannerto be described hereinafter. The drilling fluid passing through screen-l4 after removal of cuttings J5 is dischargedinto a trough ll-through whichthe fluid is discharged to a conventional suction pit (not, shown) from which the fluid is picked up by mud pumps and returned to drill pipe [2 to complete the cycle in;the usual manner. The stream of 'drilling fluid thus returned to the well, will, of course, be free of the cuttings'removed by the screen so that the next group of cuttings carried, by the next increment .of the exiting drilling fluid stream which will be caught on the screen will represent a succeeding increment of the formations being traversed by the bit. The cuttings thus separated from successive increments of the drilling fluid and collected in receptacle It may be continuously related to the earth formations or strata from which theycame in accordance with the method described in detail in Hayward U. S. Patent No. 2,214,674, September 10, 1940. In this manner, the subsequently described tests performed upon the cut tings samples may be related to the depths of the parent formations or stratafor constructa ing the desired log of 'thewell. The aforemen tioned .Haywa-rd patent describes a method for continuously correlating the; successiveincrements of the drilling fluid and the contained core; fluids with the depths of the, originating strataandsincethe solid cuttings normally do, not travel up the bore hole at exactly the same rate as the fiuid,. a correction factor must be introduced, preferably by the use of a so-called itell-tale. Such a tell-tale generallyconsists of pieces of solid matter which are chosenso as toresemble the cuttings as nearly as possible both-as to size and density. The tell-tale is inserted in the drill pipe and the number of pump strokes required to cause its re-arrival at the surfacenoted, the tell-taleparticles being caught on the shaker screen along with the cuttings.

,collected'in receptacle l6.

4 From this number, a calculated number of pump strokes to cause the tell-tale to travel from the surface to the bit is deducted. It has been found in calculating this number that it may be safely assumed that the cuttings and the fluid move downwardly in the drill pipe at the same velocity. The time of travel from the surface to the bit in any case is only a small part of the total time for the complete circuit. Broken pieces of tile and colored concrete have been found to be very suitable materials for tell-tales.

Reference may now be made to Fig. 2 which represents a form of apparatus suitable for manualOperation in performing the step of determining the natural radioactivity of the cuttings A cylindrical container l8, which may be made of, for instance,

brass, has removably' installed in it a tubular wire mesh screen i9.

A radiation detector 20, which may be of the conventional Geiger-Muller or ionization chamber type is concentrically inserted in wire screen I9. This radiation detector is connected to a preamplifier 2 I, frequency meter 22, and an indicator 23, all of which are of conventionalconstruction, the details of which are well known and form no part of the present invention Cuttings l5, obtained from receptacle Hi, are inserted in the annular space between the screen [9 and the walls of the container l8. The screen serves to protect the walls of the radiation detector which are purposely made thin in order to. be transparent, particularly to beta radiation, which is the type of radiation most easily and efliciently detected. The counts shown by the frequency meter over a predetermined period ,of time, for example, in one-half to, two minutes, are characteristic of the sample in 'thecontainer-and the figure so obtained is related to the formation to which it corresponds by the methods disclosed in the aforesaid Hayward PatentNo. 2,214,674, modified in the manner previously noted.

;By thus measuring the natural radioactivity of samples of the cuttings as they are continuously separated from successive increments of the drilling fluid leaving the well, a continuous log of the well may be made in terms of the radioactivity of the successive strata penetrated by the drill without interference with the drilling operation and the operator may thus be continuously informed of the nature of the strata being currently penetrated by the drill.

Since, as. noted previously, the entire stream of drilling; fluid is'continuously screened as it leaves the, well and all of the cuttings larger than the selected mesh of the screen areremoved from the fluid before it is returned to the well, the cuttings will, in every case, represent only the formations being currently out by the drill bit, and the radioactivity log constructed therefrom in the manner described will accurately represent the currently traversed earth strata and will be free of error arising from the inclusion in the test samples of any extraneous or non-significant material -in any manner otherwise introduced into the stream of circulating drilling fluid.

Fig. 3and 4 illustrate a form of apparatus ,by a screen 25 of a mesh suitable for retaining within the trap cuttings of th desired size. A low baffle or weir 26 is positioned on the bottom of outlet pipe H on the downstream side of trap 24 transversely to the path of flow of drilling fluid I3 and serves to slow the velocity of the drilling fluid as it passes over the mouth of trap 24. A sloping trough or mud ditch 21 is positioned below trap 24 and the outer end of outlet pipe H to receive the drilling fluid discharge from either or both of these exits. The lower end of trap 24 is provided with a flap valve 28, hinged at one side, as at 29, for opening and closing the bottom of trap 24. Opening and closing movements of flap valve 28 are controlled by means of an electric motor 30 which is connected to an operating extension 3| of the flap Valve by means of a conventional worm-gear and quadrant mechanism indicated by the numeral 32. Flap valve 28 has mounted therein a radiation detector 33 of the well known Geiger- Muller or ionization chamber type, having its detection face extending above the upper surface of flap valve 28 into the interior of trap 24. Leads 34 extend from the radiation detector for connection to the usual radiation amplifying and indicating system such as that shown diagrammatically in Fig. 2. A pair of leads 3535 connect motor 39 to a program clock mechanism 36, of any suitable and conventional design, which is supplied with alternating current from a suitable sourc indicated at 31. A pair of

electrical contacts

38 and 39 are mounted in the bottom of trough 21 and spaced slightly apart vertically for purposes to be later described. Contact 38 is connected to ground and contact 39 is connected by a lead 40 in series with a battery 4i and the coil 42 of a relay, indicated generally by the numeral 43, and thence to ground. Armature 44' of relay 43 is connected by a lead 45 to program clock mechanism 36 and has connected thereto a suitable source of alternating current 46. An electrical contact 41 arranged for contact by armature 44 is connected by a lead 48 to program clock mechanism 35.

The embodiment illustrated in Figs. 3 and 4, asdescribed above, is operated in the following manner for logging a well in the terms of the radioactivity of the cuttings. With flap valve 28 in the closed position shown in Fig. 3, cuttings will drop out of the fluid flowing over the top of trap 24 and will be trapped and held therein by screen 25, the screened fluid passing through the screened perforations in the wall of trap 24 and discharging into trough 21 where it rejoins the major portion of the fluid stream discharging further down the trough from the end of outlet pipe H. As the cuttings accumulate in trap 24, they gradually close off successively higher perforations in the trap wall until all of the perforations have been sealed off, whereupon the'flow of screened fluid into trough 2? from the trap will cease. The cessation of flow into the upper end of the trough lowers th level of liquid flowing therein sufficiently to break the fluid connection between

contacts

38 and 39. The breaking of this contact closes relay 43 which will cause program clock mechanism 36 to start a new cycle. After a period of time, depending upon the type of radiation detector used, the clock operated mechanism will start motor 30, which opens flap valve 28 and discharges the cuttings deposited in trap 24 on the face of the flap valve and above and about th detector face of the radiation detector 33 into trough 21. Fluid from the stream passing through outlet pip II of the counter,

will, of course, follow the cuttings and wash them completely from the face of the flap valve and of the radiation detector. After a suitable interval necessary to accomplish this operation, the

mechanism of program clock mechanism 36 will cause motor 30 to reverse and close flap valve 28 in order that a new group of cuttings may deposit in trap 24, to begin a new test cycle.

During the interval between the breaking of the circuit at

contacts

38 and 39 and starting of motor 33 by program clock mechanism 36, radiation detector 33 will, of course, be receiving the radiations from the cuttings in the trap and will transmit this indication to the indicating or re cording apparatus connected to the detector;

The quantity or increment of the mud stream from which the group of cuttings thus examined are deposited will be correlated with the depth of the formation from which the cuttings came in the manner previously described in connection with the embodiment of Figs. 1 and 2. By repeating the operation described, the radiation characteristics of the cuttings of successive increments of the drilling fluid may be determined and a continuous log made of the formations. The mud fluid leaving trough 27 flows to a conventional settling pit of relatively large area in which the cuttings will have sufficient time to settle out so that cuttings-free liquid will be returned by th mud pumps in the usual manner to the well and. again, as in the previously described embodiment, the cuttings appearing in trap 24 will represent the cuttings from the formations being currently out by the bit.

Fig. 5 illustrates another embodiment of apparatus by which a continuous log of the radioactivity of the cuttings ma be obtained automatically. A modified form of Geiger-Muller counter, indicated generally by the numeral 53, comprises a generally cylindrical chamber 5|, constructed of some suitable material such as brass, which has extending axially therethrough, a tube 52 which serves as a radiation window, and is, constructed of very thin metal, or other suitable material of well known character designed to readily pass radiations into the interior of chamber 5|. The lower end of tube 52 is open and the upper end is provided with funnel-shaped mouth 53. The interior of tube 52 is concentrically lined with a screen 54, slightly spaced therefrom to protect the normally fragile tube from being torn or punctured by the cuttings particles from which radiations are received. Tube 52 and chamber 5! form the usual anode The cathode comprises a plurality of thin wires 54a concentrically disposed between the wall of chamber 5! and the exterior of tube 52 and vertically suspended from a ringshaped conductor support 55. The anode (chamber 51 and tube 52) and the cathode (wires 54a) are connected through leads 56 and 51, respectively, and a conventional electrical circuit to an amplifier 58 which is connected by leads 59, 60 to a conventional frequenc meter 6!, the output of which drives the pen arm 62 of a conventional strip chart recorder 33. A normally open switch 64 is interposed in lead 59 and is controlled by a relay 35 which is, in turn, controlled by a program clock mechanism 66 of well known design driven from a suitable source of A. C. 14. posed on opposite sides of mouth 53 of tube 52 is a light source 61 and a cooperating photo-electric cell 68. The latter is suitably and conventionally connected to an amplifier 69, the output of which actuates a relay 1!! which controls a normally open Disswitch H, the contacts of which are connected by leads 12, 13 to program clock mechanism 65. Alternating current source 74 is connected into lead 12.

The lower end of tube 52 is closed by a conical plug valve 15 mounted on the upper end of hollowstem 16 the bore of which communicates with a plurality of passageways ll extending through the body of plug valve 15 to the upper surface thereof. The lower end of stem 78 carries a piston 18 slidably mounted in a piston chamber 79. A coil spring 80 is mounted in compression between the lower end of piston 18 and. the bottom wall of piston chamber 19 and is adapted to normally urge the piston in the upward direction. A stufiing box 8| on the upper end of piston chamber 19 forms a fluid tight seal about stem 76. Piston 18 and the bottom wall of piston chamber 19 are provided with leak ports 82 and 8.3, respectively. A passageway 84 provides communication between the bore of stem l and the exterior thereof and is so positioned in the stem that it is enclosed within sturling box 8i when t .e piston and stem are in their upwardly extended position, as shown in solid lines in Fig. 5, and is in communication with the interior of piston cham-' ber 19 when the piston is in the retracted position, as shown in broken lines in Fig. 5, A pipe 85, connected to a suitable high pressure water supply (not shown), communicates with the interior of piston chamber l9 above piston 78 and is fitted with conventional solenoid operated valve 86 adapted to be opened and closed b means of a solenoid 81, connected by a pair of

leads

88, 89 to a normally open switch 98. A current source 9! is connected into lead 88. Switch 93 is controlled by a relay 92 which is connected by leads 93, 94 to program clock mechanism 85.

The above described apparatus is employed to obtain automatically a continuous radio-activity log of a well in the following manner. The radiation detector 58 is disposed relativeto the end of the screen 95'of a shale shaker so that the cut-v tings discharging from the lower end of the screen will fall through a hopper 96 controlled by an electrically operated diversion valve 91 suitably actuated by relay 10 through leads 93 and A. C. supply 14. The cuttings will pass through hopper 96 and fall into mouth 53 of tube 52 out of the path of the light beam passing between light source 61 and photoelectric cell 68. Plug valve 15 will be in the closed position against the lower end of tube 52 and the tube will fill with cuttings until a level is reached, as indicated by the broken line 96a, at which the light beam from source 6'! will be interrupted. The circuit in amplifier 69 is so arranged that upon interruption of the light beam, relay 10 will be energized to close switch H connecting program clock mechanism .56 to alternating current source M tarting the cycle of v theclock mechanism. At the same time diversion valve 91 will be moved to the position shown in broken lines, temporarily diverting the cuttings fromtube 52. Starting of the program clock cycle will 'first energize relay 65 to close switch 64, whereupon the impulses from radiation de stream of high pressure water through pipe into the upper portion of piston chamber 19, where the water pressure forces piston 18 downwardly against the pressure of coil springBll and pulls plug valve 15 downwardly and opens the 'lower end of tube 52. The collected cuttings will then fall out of the tube to clear it for the reception of a succeeding sample of the cuttings. As stem 15 moves downwardly under the pressure of the water, passageway 84 moves down into the interior of piston chamber 19. Water will then flow through passageway 84 into the bore of stem 56 and thence through passageways T! which will emit jets of water under sufiicient pressure to clear tube 52 and the surface of plug valve 15 of any remaining cuttings particles. Program clock mechanism 65 then completes its cycle and initial conditions are restored. At the same time com munication is restored between light source El and photoelectric cell 53, whereupon the circuit of amplifier 69 reopens switch H and opens diversion valve 9?, returning the stream of cuttings to tube 52. The temporary diversion of cuttings during the relatively short intervals occupied by the cycles of the program clock mechanism will not significantl affect the continuity value of the log obtained by this apparatus.

7 Chart recorder 63 may be of the form disclosed in Hayward U. S. Patent No. 2,404,132 issued July 16, 1946 for Apparatus for Use in Logging Wells, so that the curve of radio-activity traced on the chart by means of pen arm 62 will be automatically correlated with the depth of the well to produce directly the desired radio-activity log of V the well.

It will be understood that'various changes and alterations may be made in the method and apparatus heretofore described without departing from the scope of the appended claims but within the spirit of this invention.

' \Vhat I claim and desire to secure by Letters Patent is:

1. In the drilling of a well by the rotary method employing a circulating stream of drilling fluid, the method of logging the well, comprising, separating from the stream of returning drilling fluid the formation cuttings in the order in which they are deposited in said stream by the drill, and measuring the radio-activity of the so separated cuttings.

2. In the drilling of a well by the rotary method employing a circulatory stream of drilling fluid, the method of logging the well, comprising, separating from the stream of returning drilling fluid the formation cuttings in the order in which they are deposited in said stream by the drill, correlating the successive groups. of separated outtings with the depths of the formations from which they came, and measuring the radio-ac tivity of the so-separated cuttings.

3. In the drilling of a well by the rotary method employing a circulating stream of drillingfluid, the method of logging the well, comprising, passing the entire stream of returning drilling fluid through a screen to separate from the stream all of the formation cuttings in the order in which they are deposited in said stream by the drill, correlating the successive groups of separated outtings with the depths of the formations from which they came, and measuring the radio-activity of the so-separated cuttings.

4. In the drilling of a well by the rotary method employing a circulating stream of drilling fluid, the method of logging the well, comprising, continuously diverting from the returning stream of posited in said stream by the drill, continuously correlating the successive groups of separated cuttings with the depths of the formations from which they came, and measuring the radio-activity of the so-separated cuttings.

In the drilling of a well by the rotary method employing a circulating stream of drilling fluid, the method of logging the well, comprising, continuously diverting from the returning stream of drilling fluid a portion thereof together with the formation cuttings carried thereby, continuously separating from said diverted portion said formation cuttings in the order in which they are deposited in said stream'by the drill, continuously correlating the successive groups of separated cuttings with the depths of the formations from which they came, measuring the radio-activity of the separated cuttings, thereafter remixing said diverted portion of said stream with the remainder of said stream, separating said formation cuttings from the entire re-mixed stream, and returning the stream to the well.-

6. In the drilling of a well by the rotary method employing a circulating stream of drilling fluid, the method of logging the Well, comprising, separating from the stream of returning drilling fluid the formation cuttings in the order in which they are depositedin said stream by the drill, measuring the radio-activity of the so-separated cuttings, and returning to the well only drilling fluid from which said cuttings have been removed.

'7. In the drilling of a well by the rotary method employing a circulating stream of drilling fluid, the method of logging the well, comprising, separating from the stream of returning drilling fluid the formation cuttings in the order in which they are deposited in said stream by the drill, correlating the successive groups of separated cuttings with the depths of the formations from which they came, measuring the radio-activity'of the so-separated cuttings, and returning to the well only drilling fluid from which said cuttings have been removed.

3. In the drilling of a Well by the rotary method wherein a stream of drilling fluid is circulated through the well and cuttings particles of the earth formations traversed by the bit are con tinuously introduced into said fluid in the order in which the bit traverses said earth formations during the drilling operation, the method of log ging the well, comprising, continuously separating from successive increments of the exiting stream of said fluid cuttings particles as successively de posited-therein by the bit, and measuring the radio-activity of the so-separated cuttings particles.

9. In the drilling of a well by the rotary method wherein a stream of drilling fluid is circulated through the well and cuttings particles of the earth formations traversed by the bit are continuously introduced into said fluid in the order 'in which the bit traverses said earth formations during the drilling operation, the method of logging the well, comprising, continuously correlating the successive increments of the exiting stream of said fluid and their contained cuttings particles with the depths of the formations to which they relate,'continuously separating from said successive increments said cuttings particles, and measuring the radio-activity of the soseparated cuttings particles.

10. In the drilling of wells by the rotary method wherein a stream of drilling fluid is circulated through the well and cuttings particles of the earth formations traversed by the bit are. continuously introduced into said fluid in the order in which the bit traverses said earth formations during the drilling operation, the method of logging the well, comprising, continuously correlat ing the successive increments Of the exiting stream of said fluid and their contained cuttings particles with the depths of the formations to which they relate, continuously separating from said successive increments said cuttings particles, measuring the radio-activity of the so-separated cuttings particles, and returning to the well only drilling fluid from which said cuttings particles have been removed. JOHN T. HAYWARD.

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

UNITED STATES PATENTS Number Name Date I 2,206,922 Smith July 9, 1940 2,214,674 Hayward Sept. 10, 1940 2,289,687 Stuart July 14, 1942 2,302,996 Lilligren Nov. 24, 1942 2,346,203 Zaikowsky Apr. 11, 1944 2,458,093,

Muskat et a1 Jan. 4, 1949