US3209823A

US3209823A - Core orientation

Info

Publication number: US3209823A
Application number: US24924A
Authority: US
Inventors: David E Winkel
Original assignee: CREIGHTON A BURK
Current assignee: CREIGHTON A BURK
Priority date: 1960-04-27
Filing date: 1960-04-27
Publication date: 1965-10-05
Anticipated expiration: 1982-10-05

Description

D. E. WINKEL CORE ORIENTATION Oct. 5, 1965 4 Sheets-Sheet 1 Filed April 27, 1960 Fig.

David E. Winkel INVENTOR.

Attorneys D- E. WINKEL.

CORE ORIENTATION Oct. 5, 1965 4 Sheets-Sheet 2 Filed April 27, 1960 David E. Winke/ INVENTOR. BY%,;

Attorneys Oct. 5, 1965 D. E. WINKEL 3,209,823

CORE ORIENTATION Filed April 27, 1960 4 Sheets-Sheet s David E. Winkel INVENTOR.

wwwiow Attorneys Oct. 5, 1965 D. E. WINKEL 3,209,823

CORE ORIENTATION Filed April 27, 1960 4 Sheets-Sheet 4 MAGNETIC NORTH Fig.20.

David E. Wmke/ IN V EN TOR.

Attorneys E I l United States Patent 0 3,209,823 CORE ORIENTATION David E. Winkel, Laramie, Wy0., assignor of thirty-five percent to Creighton A. Burk, ten percent to Thomas J. Fagan, and ten percent to James W. Fagan, all of Casper, Wyo.

Filed Apr. 27, 1960, Ser. No. 24,924 14 Claims. (Cl. 166-4) This invention relates to the determination of the orientation of core samples taken from the earths crust and particularly to a method for utilizing the earths magnetic field in making such determination and to apparatus employed for this purpose.

Core drilling is employed in various fields and paiticularly in the mining and petroleum industries in order to secure samples of the earths crust at predetermined depths to secure subsurface geological data for the purpose of analysis and study. Full knowledge of the characteristics of a subsurface formation can be obtained only if the precise location and orientation of the core sample before it was taken can be determined. Many devices, methods and techniques have been employed for this purpose. Some are complicated and time-consuming, some are of limited accuracy, and others have not been entirely satisfactory for various reasons.

Some of these methods for core orientation have utilized the earths magnetic field in effecting the determination of the position of the core sample. One such method employs cementitious material in a fluid state having finely divided particles of ferromagnetic material mixed therein, the mixture being deposited in a small cavity drilled in the bottom of the bore to be cored. While the mixture is still in a fluid state, the particles align themselves with the earths magnetic field and are then locked in their position of alignment upon solidification of the cementitious material. Thereafter the core is drilled and taken with the body of solidified mixture remaining in position in the cavity at the top of the sample and a magnetometer is employed to determine the polarity of the magnetic particles in the core.

The present invention provides novel methods and apparatus constituting improvements on the methods and apparatus of the type for determining the orientation of core samples by employing a fluid mixture of solidifiable material and magnetic particles.

It is an object of the present invention to provide an improved method utilizing a mixture of magnetic particles and a solidifiable fluid for determining the original orientation of objects removed from inaccessible places.

It is another object of this invention to provide an improved method for determining the orientation of a core sample as it was prior to its removal and which employs a mixture of solidifiable material and magnetic particles and utilizes the earths magnetic field for orientation of particles. I

It is another object of this invention to provide a simple and effective method for determining the orientation of a core sample while employing standard drilling equipment and with minimum interference with the normal drilling or coring procedures.

It is another object of this invention to provide an improved method for effecting the positive determination of the orientation of a core sample and which employs simple and relatively inexpensive equipment.

It is a further object or" this invention to provide an improved material comprising a mixture of solidifiable liquid and fine magnetizable particles for location on and adherence to rock and rock-like structures.

It is a further object of this invention to provide an improved apparatus for effectively determining the magnetic polarity of small fragments of matter.

3,209,823 Patented Oct. 5, 1965 "Ice It is a further object of this invention to provide an improved method for emplacing a solidifiable magnetic mixture on Well bottoms or other remotely located surfaces.

It is a further object of this invention to provide an improved device for emplacing a solidifiable magnetic mixture on a well bottom or other remotely located surface.

It is a still further object of this invention to provide an improved portable and rugged instrument for accurately determining the magnetic polarity of small fragments of magnetized material.

Briefly, in carrying out the objects of this invention in one embodiment thereof a mixture of epoxy resin and finely divided ceramic magnetic material together with an agent for effecting solidification at the end of a predetermined period is provided and before use the ceramic particles are magnetized by subjecting them to a relatively strong magnetic field. The material is then lowered to the bottom of a well or drill hole and is discharged so that it spreads over the bottom and the drilling or emplacing equipment is then removed to take away any magnetic elements thereof. The magnetic particles in the liquid mixture then align themselves with the earths magnetic field and at the end of the predetermined period the mixture solidifies, locking the particles in their aligned positions and affixing the solidified mass securely to the rock. The core sample is then taken with a drilled-out portion of the solidified mixture adhering tightly thereto.

At the surface the core sample ismarked to provide an identifying line and a small fragment including an identifiable part of the marking is removed, floated on a liquid in a uni-directional magnetic field, and the direction of magnetization or polarity of the particles is determined. The core sample is then marked with the direction of the magnetic field indicating the direction of the north magnetic pole of the earth, this being determined by the known position of the fragment with respect to the core prior to its removal. One embodiment of the instrument for determining the polarity of the fragment removed from the sample comprises a magnet structure mounted within a case and providing a gap between the opposite magnetic poles within which is arranged a vessel for holding liquid on which the fragment of the solidified material may be floated. An optical system including a reticle for alignment with the markings on the fragment is rotatably mounted about a vertical axis centrally of the vessel and includes an azimuth ring for indicating the angular difference between the direction of the magnetic field of the aligned magnetic particles and the orientation line of the fragment.

The features of novelty which characterize the invention are pointed out with particularly in the appended claims. The invention itself, however, both as to its organization and method of operation, may best be understood upon reference to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a sectional view of a well drill assembly at the bottom of the well in position during emplacement of liquid in accordance with the method of this invention;

FIG. 2 is a View similar to FIG. 1 showing the tool assembly withdrawn from position after emplacement of the liquid;

FIG. 3 is an illustration of the same portion of the well with the tool assembly removed and the coring bit in position during the coring operation;

FIG. 4 is an enlarged view of the liquid charged container employed in the equipment of FIG. 1;

FIG. 5 is an enlarged sectional view of the lower portion of the charged container in FIG. 4;

FIG. 6 is a view similar to FIG. showing the container during discharge of the liquid;

FIGS. 7, 8 and 9 are views similar to FIGS. 1, 2 and 3, respectively, illustrating coring equipment provided with a liquid charged container embodying the invention shown during three steps in the method of the invention;

FIG. 10 is an enlarge-d view partly in section of the coring bit and container of FIG. 1;

FIG. 11 is an enlarged sectional view of the lower portion of the container;

FIG. 12 is a plan view of the bottom of the well bore having the solidified orientation material of the invention in position thereon and illustrating characteristics of the invention;

FIG. 13 is a view similar to FIG. 12 showing the top of the core after removal and illustrating a step in the method of the invention;

FIG. 14 illustrates a magnetic device for determining the orientation of particles in accordance with the invention;

FIG. 15 is a view similar to FIG. 13 illustrating the marking of a core in accordance with its determined orientation;

FIG. 16 is a perspective view partly in section of an instrument for facilitating the determination of the magnetic polarity of particles with a portion of the instrument removed for purposes of illustration;

FIG. 17 is a perspective view partly in section of the optical system and azimuth ring for the instrument of FIG. 16;

FIG. 18 is a sectional view along the line 18-18 of FIGS. 16 and 17 illustrating the optical system in position on the instrument;

FIG. 19 is a plan view showing the top of the instrument of FIG. 18; and

FIG. 20 is a chart for use in the method of the invention for determining the angular correction required for cores taken from deflected bores.

In the drawings the invention has been illustrated in connection with apparatus suitable for placing a charge of solidifiable liquid mixture including a dispersion of magnetic particles at the bottom of the well bore. The liquid is selected to solidify at the end of a known period of time and all magnetic materials are removed from the vicinity of the bottom of the well before the end of this time so that the magnetic particles in suspension in the liquid will align themselves only with the earths magnetic field prior to solidification of the liquid. After solidification, a core sample is taken, the top end of the sample having the solidified liquid securely adhering thereto.

Various liquid mixtures may be employed in practicing the invention and the particular mixtures and solidification times are selected depending upon the depth of the bore hole and the nature of the reservoir formation or rock surface on which the liquid is to be solidified and to which it must adhere securely when solidified. Coloring may also be added to facilitate recognition of the solidified liquid on the core. The solidified liquid must have the characteristic of adhering securely to the rock or other material to be cored. Various liquids are suitable for mixture with magnetized particles and may be selected depending upon the requirements of the specific application. It has been found that highly satisfactory results may be secured by employing epoxy resins with a polyamine as the crosslinking or solidifying agent; these resins have the property of wetting rock surfaces and are admirably suited for securing good attachment of the solidified material to the core. Furthermore, while various magnetic materials can be employed and give usable results, it has been found that ceramic magnetic materials commonly known as ferrites are especially useful in the practice of this invention. These ceramic magnetic materials have a high coercive force so that after being magnetized they cannot be demagnetized or remagnetized easily and thus provide substantially permanent records of their alignment after solidification of the liquid. Furthermore, the density of the ceramic materials is substantially lower than that of metallic magnetic substances such, for example, as iron and Alnico particles, and as a result the ceramic materials provide magnetic particles which do not settle as readily in the liquid and therefore may be kept more uniformly distributed in the liquid and provide more uniform and reliable results. Furthermore, the ceramic materials are easily powdered and are particularly suitable to use in a finely divided state which provides the added advantage of greater sensitivity to alignment.

The nature, size and concentration of the magnetized particles are, as indicated, varied to meet the particular drilling conditions. For some applications the particles may be of visible size and may be sufficiently large for direct observation; for the purpose of direct observation the particles may be suitably colored or otherwise marked and relatively large particles may be marked by color or shape to indicate their polarity. However, for most of the applications herein contemplated, the particles will be of small size and direct visual observation of their orientation is not required.

In order to secure accurate and reliable placement of the liquid mixture at the bottom of the well to be cored, charged containers are provided which include the solidifiable liquid and the magnetizable particles mixed therein. The container is preferably charged with a gas under pressure. When liquids such as epoxy resins are employed, the solidifying or cross-linking agent such as a polyamine may be isolated within the charged vessel by a frangible capsule or diaphragm which may be broken at the time it is to be mixed with the resin, the solidifying time running from the time of breaking the capsule or diaphragm. The magnetizable particles may be magnetized at any time. However, it is preferred for most applications not to magnetize the particles until they are about to be used, whereupon they can be magnetized by passing them through a magnetic field. The concentration of the magnetic particles may be varied according to the requirements of the particular application. However, for general purposes it has been found that a low concentration of magnetic particles provides a very practical type of mixture and avoids a tendency to obscure alignment with the earths field which may result from magnetic interaction between the particles when they are in excessive abundance. For example, a solidifiable substance for the core orienting method of this invention may comprise an epoxy resin with a polyamine solidifying agent (preferably a higher polyamine) comprising the liquid and finely powdered ceramic magnetic material having a concentration of one-tenth to one gram per liter of the liquid. With this mixture, when a solidified fragment is taken from the core it has been found that this fragment may be as small as ten cubic millimeters and still provide an adequate indication of the orientation or polarization of the mass of particles produced by alignment with the earths magnetic field.

For further purposes of illustration and not by way of limitation, another example of a practical mixture suitable for use in the method of this invention comprises an epoxy resin identified as resorcinol diglycidyl ether with a hardening agent sold by the Dow Chemical Co. as X2654.4. This composition may be employed effectively with ceramic magnetic materials such as one sold under the trade name Indox-l and the chemical composition of which is BaFe12019- For storage purposes the charged containers may be kept cool, which increases the viscosity of the liquid and minimizes or prevents agglomeration of the contained particles. It is particularly desirable to use low temperature storage to keep the viscosity high when the particles have been magnetized before storage.

The solidification time for the liquid mixture may be changed selectively by varying the type or amount of epoxy resin or solidifying agent to provide periods from a fraction of an hour to many hours depending upon the application in which it is to be employed. In the case of charged containers provided with breakable capsules or diaphragms each container may be marked to indicate its solidification period, which will depend on the nature of the resin and solidifying agent employed and the temperature within the particular well bore.

Referring now to the drawings, FIG. 1 illustrates a drill collar 21 carrying a drilling bit 22 within a well bore defined by walls indicated at 23, the bit 22 resting against the bottom of the bore indicated at 24. Within the collar 21 there is positioned a standard well survey tool 25 including a hollow anchor 26 and a landing shoe 27 secured to the bottom end of the anchor and resting in position against a bafiie plate 28 at the top of the bit 22. This particular arrangement of the survey tool in the drilling equipment is commonly known as the bottom-landing type. The devices for emplacing the orienting substance herein described are equally applicable without modification in the survey tool arrangement known as the toplanding type, where the body of the survey tool passes through the plate and is arrested when an enlarged member of the top of the tool contacts the baflie plate.

The hollow anchor is provided with a charged container and in FIG. 1 a body of liquid mixture 29 has been shown during its discharge through a fluid port 30 in the bit 22. The liquid is discharged through the landing shoe 27 in a manner to be described below. After the liquid has been deposited as indicated in FIG. 1, the drill assembly is removed from the area as indicated in FIG. 2, the distance of removal being suificient to prevent any interference with the effect of the earths magnetic field on the magnetic particles within the discharged liquid.

In carrying out the method of the invention as illustrated in FIGS. 1, 2 and 3, the drill assembly is removed completely from the well or bore and a coring bit is then employed as illustrated in FIG. 3 to remove a core including a portion of the liquid 29 after it has solidified and has attached itself to the bottom of the bore hole 24. As shown in FIG. 3, a coring bit 32 is being operated to remove a core 33 from the bottom of the hole with a portion of the now solidified liquid 29 remaining on the top of the core. The coring bit 32 is attached to an outer core barrel 34 in the usual way and an inner core barrel 35 is provided in the usual way to receive and retain the core 33. The material 29 remains securely aflixed to the top face of the core after having been solidified with the magnetic materials dispersed therein. These materials are aligned by the earths magnetic field and provide a substantially permanent record for test purposes. After the core has been brought to the surface it may be positioned in accordance with the previously secured well data and oriented about its axis by the method of this invention as more fully described later herein.

The construction and arrangement of the charged container within the anchor section 26 of the standard type well survey tool is clearly shown in FIGS. 4, 5 and 6 where the anchor section is shown containing a charged vessel or pressurized cartridge 36. The cartridge 36 and anchor 26 are preferably constructed of a non-magnetic material which may, for example, be a molded synthetic resin or plastic. Other suitable materials include aluminum, magnesium, and plastics having glass fibers incorporated in them, all of which may be drilled away should they lodge in the bore. The cartridge is filled to a predetermined level with the solidifiable liquid 37 and is sealed with a volume of gas under pressure above the liquid. The cartridge may be fitted with a standard pneumatic valve 36' through which compressed air or other gas may be admitted to charge the container to the desired pressure.

Before the cartridge is sealed, a frangible or shatterable capsule, diaphragm or other container 41 filled with suitable solidifying or cross-linking agent for the resin or other liquid 37 is positioned in the cartridge and attached to the wall of the cartridge well below the surface of the liquid. This capsule has been shown unbroken in FIG. 4, although in normal use when the cartridge is inserted in the anchor section the capsule would have been broken and the catalyst mixed with the liquid 37 in order to start the solidification period. The capsule 41 may be broken by a sharp blow against the container.

The lower end of the cartridge is provided with an arrangement for breaking a wall portion of the cartridge and discharging the liquid when the tool strikes the bottom of the hole. In cartridges having the frangible capsule or diaphragm attached to or near the bottom wall portion of the cartridge to be broken, the solidifying agent will be mixed with the solidifiable fluid during the interval of fluid discharge. The details of construction of the wall piercing and fluid discharging device are shown in FIGS. 5 and 6. As shown in these figures, the landing shoe 27 has a central passage 38 within a tubular fitting 39 which is threaded into the upper portion of the shoe as indicated at 40. The shoe is provided with external threads 42 at its upper end so that it can be threaded into corresponding internal threads at the bottom end of the anchor section 26. When the cartridge 36 is to be placed in the anchor section the shoe 27 is unscrewed and the upper pointed end of the tube 39, in dicated at 43, is pressed into a fitting 44 molded as an integral part of the cartridge. The fitting 44 is provided with a central opening or chamber below a bottom wall portion 45 of the cartridge and is provided with intermediate and

bottom restrictions

46 and 47, respectively, which have central openings slightly smaller than the external diameter of the tube 39. The plastic material of the fitting is snfiiciently flexible to be deformed and afford passage for an annular wedge member 48 on the tube 39 which thus enters the lower chamber formed between the

restrictions

46 and 47. The pointed end 43 extends into the upper chamber and lies just below the cartridge wall 45. A second annular wedge 49 is provided on the tube 39 in a position to lie outside just below the fitting 44.

The cartridge with the landing shoe and tube 39 assembled in the fitting 44 is then inserted in the anchor section 26 and the shoe screwed into place at the bottom of the section. The assembly is then dropped or lowered into the drilling tools where it becomes positioned for discharge as shown in FIG. 1. When the survey tool and anchor 26 strike the baffle plate 28, the momentum of the cartridge presses the wall 45 against the pointed tube which then pierces the wall, the wedge 48 entering the upper shoulder of the fitting and the wedge 49 entering the lower, as indicated in FIG. 6. The shape of the annular wedges prevents their being withdrawn from the cartridge and holds the cartridge and tube in discharging position. The gas under pressure then forces the liquid downwardly through the tube and discharges it onto the surface at the bottom of the well as indicated by the arrows in FIGS. 1 and 6. Before dropping or lowering the survey tool and combined cartridge into position for emplacement of the liquid it may be necessary or desirable to circulate the drilling fluid to clear any chips or debris from the bottom of the bore.

After emplacement of the liquid the tool assembly is raised, as stated heretofore, to remove all magnetic material, and when the equipment has been raised the magnetic particles in the liquid are influenced solely by the earths magnetic field and align themselves with the field. When the liquid has solidified the particles are locked in their aligned position and provide a positive indication of the direction of the earths field through the zone at the bottom of the bore, and thus after coring provide this indication on the core which indication is not affected by any turning or twisting of the core during removal.

In the above described embodiment of the invention the liquid emplacing device has been employed with a standard surveying tool lowered in the usual manner through the drill stem or collar and it is thus not necessary to provide a modification of the standard drilling equipment.

The method of this invention may also be practiced in connection with standard coring tools by utilizing the pressurized cartridge and without modifying the coring tools for this purpose. FIGS. 7, 8 and 9 illustrate the same three steps of the method as FIGS. 1, 2 and 3 but with standard coring tools in all steps. In these figures a standard coring tool comprising an outer core barrel 34a having a coring bit 32a is employed, an inner core barrel 35a being arranged to receive the core in the usual manner. A suitable core catching and retaining means such as resilient stepped or shouldered fingers 51 are provided in the usual manner at the lower end of the inner barrel to grip and retain the core.

In this arrangement the charged container or cartridge is constructed substantially in the form of a standard core barrel plug or core marker so that it fits the coring tool and may be locked in place until the emplacement of the liquid has been effected. As shown in FIG. 7, a pressurized cartridge 52 is positioned and locked in the lower end of the coring tool and extends a substantial distance beyond the bit. The cartridge is provided with a discharge device 53 which is actuated upon striking the bottom of the bore 24a and deposits the liquid 29a in a manner similar to that of the first embodiment. The impact on striking the bottom also breaks the lock and allows the cartridge to move back into the core barrel 35a as indicated in FIG. 8 showing the coring bit raised. after deposit of the liquid 29a. Then when the well is cored as indicated in FIG. 9 the spent cartridge is moved upwardly in the core barrel in the usual manner of a core marker by the core 33a which is being drilled.

The details of construction of the cartridge and discharge mechanism are shown in FIGS. and 11. As shown in FIG. 10 the cartridge comprises a hollow container of plastic such as polyethylene or other easily drillable and non-magnetic material which is shaped to be adapted to the particular type of coring tool with which it is employed. In the illustrated arrangement the core catcher 51 is provided with recesses which receive integral shearing pins 54 formed on the outer wall of the container 52; these pins lock the container in position and prevent its displacement until the unit strikes the bottom of the bore whereupon the contained fluid is ejected, as more fully described hereafter, and the pins are sheared off. The cartridge is charged with a solidifiable liquid 55 such as an epoxy resin and a quantity of magnetized ceramic magnetic particles and charged with gas under pressure, as through a pneumatic valve, in the same manner as that of FIG. 4. The cartridge is also provided with a longitudinal frangible diaphragm 56 separating the solidifiable fluid 55 from the solidifying agent 55. For purposes of charging, two standard pneumatic valves 52 may be mounted at the top of the cartridge one in communication with a respective chamber on each side of the diaphragm. Thus the liquids are discharged under pressure when the device 53 strikes the bottom of the well bore.

As shown in FIG. 11, the device 53, comprises a tube 57 having upper and lower wedge-shaped ends 58 and 59 both of which have perforations providing open communication at the two ends of the tube. The upper wedge 58 is fiat and is positioned transversely of the diaphragm 56 so that it will cut into both sides of the diaphragm and release both liquids. The tube is secured in position by a collar 61 threaded onto a boss or fitting 62 threaded or otherwise secured to the bottom of the container 52. The upper wedge 58 fits in the central opening of the fitting 62 with its point below the wall 65 of the container and with its base resting on the collar 61 which holds it in position.

The tube is also provided with a suitable ridge or key (not shown) to fit a complementary recess (not shown) at the side of the opening through the collar and prevent rotation of the tube. A compression spring 63 may be mounted about the tube between the cone 59 and the collar 61 to hold the cone 58 against the collar 61 and minimize the likelihood of accidental puncture of the cartridge.

The bottom wall of the container is relatively thin as indicated at 65, and when the device 53 strikes the bottom of the well bore the upper wedge 58 pierces the wall 65 and ruptures the diaphragm 56 and allows the liquids 55 and 55' to be discharged by the gas pressure, the liquids flowing through the tube, mixing therein, and out onto the rock surface. The broad base of the wedge 58 holds the wedge within the container during discharge against the pressure in the container which tends to force the tube outwardly.

The modifications of the invention described above may be employed with standard types of equipment as described. In some applications it may be desirable to drop or otherwise deposit a charged container or cart-ridge into the well after the drilling equipment has been removed and then to lower the coring tools, break the cartridge in position at the bottom thereby releasing the liquid, then withdrawing the tools as before and, after solidification of the liquid, drilling the cores, the cartridge casing being of drillable material and being drilled away in the coring process. The cartridges for this method of operation may, for example, be one of the cartridges 52 of FIG. 7 with the ejection device 53 removed as it is not required when the cartridge is to be broken by the drill. Other forms or shapes and sizes of the charged cartridges may be employed and, for example, may be relatively small spherical cartridges a plurality of which are dropped into the well or admitted with the drilling fluid. Such capsules may also be constructed with sufficient weight added that they will sink through the circulating medium or drilling fluid and settle to the bottom rapidly after the circulation has stopped. These containers which are to be broken by the drilling equipment need not be pressurized. However, pressure ejection and the forced discharging of the liquid will help in many cases to etfect better emplacement of the liquid on the surface of the rock to be cored. Also when employing the plurality of small cartridges, some may contain the resin and ceramic magnetic powder while others contain the solidifying agent, the mixing being effected upon breaking of the cartridges at the bottom of the well.

After the core sample has been taken with the solidified liquid affixed to its end, it is necessary to determine the direction or polarity of the aligned particles. FIG. 12 illustrates the bottom of a well bore 24a with the solidified magnetic-particle mixture 29a covering a portion of the bottom. For purposes of illustration the earths magnetic field at the bottom of the bore hole has been indicated by a plurality of parallel arrows 66 pointing in the same direction toward magnetic north and the particles have been shown as short lines 67 in the material all parallel to the magnetic field or arrows. As mentioned heretofore, the particles may be visible and may even be colored or otherwise marked to indicate their north pointing poles; however, for most applications the magnetic particles will be in minute or powder form. The short straight lines of FIG. 12 nevertheless serve to illustrate the action with either type of particle.

The alignment of the particles may be determined by testing a very small fragment of the solidified plastic as already mentioned. In FIG. 13, which is a plan view of the central portion of the same rock formation as FIG, 12 after being cut and removed as a core, the core has been shown after the solidified mixture has been marked and is ready for the removal of a circular fragment 68. The core has been marked by drawing a straight line 69 across the top of the solidified plastic and a second short parallel line 70 close to it. The fragment 68 is cut so that the line 70 extends only a short distance across it to serve as a position indicator. This short line thus identifies the position of the fragment on the core and facilitates correct placing of the fragment when it is re turned to the core after determination of its polarity. The fragment is preferably cut or otherwise removed so that it is taken from a plane substantially at right angles to the axis of the core.

After the fragment has been cut from the body of ma terial it is tested in a simple magnetic device a basic form of which is shown in FIG. 14. The device provides a body of liquid 72 in a non-magnetic cup or vessel 73 which rests between north-attracting and south-attracting

pole pieces

74 and 75, respectively, of a U-shaped magnet 76. The fragment 68 is floated on the liquid and remains substantially at the middle of the vessel due to surface tension forces of the liquid. The fragment is free to rotate and aligns itself with the relatively strong magnetic field of the magnet, the north-seeking pole of the fragment, as determined by the alignment of the contained magnetized particles, pointing toward the north-attracting pole of the magnet as represented by the arrow 77 indicated on the the water surface. The angle between the straight lines on the fragment and the direction of the field is then measured as by observing a protractor (not shown) placed across the rim of the cup 73. For purposes of illustration the fragment 68 is shown in FIG. 15 replaced to its original position on the core and the magnetic north line 77 marked at the measured angle with respect to the line 69. In actual practice, however, only the angular difference between the

lines

69 and 77 as described need be transferred to the core; the fragment need not be replaced. Any suitable system of marks or method of marking may be employed, the parallel lines being shown as one suitable and simple method by way of example.

An instrument for facilitating the more precise determination of the direction of alignment or polarity of the particles is shown in FIGS. 16 through 19. The instrument comprises a rectangular box having a base 79 of non-magnetic material on which are supported northattracting and south-attracting

magnetic pole pieces

80 and 81, respectively, and a return magnetic path comprising the four

side walls

82, 83, 84 and 85 of the case. The

poles

80 and 81 are spaced apart and a vessel or Vial 87 is mounted centrally in the space between the poles, a circular recess 86 being provided in the base 79 to receive the vessel. The case is completed by a non-magnetic cover or top 88 having a circular central opening 89 which receives the upper end of the vessel 87. A ring 91 is fixed to the top 88 concentric with the opening 89 and acts as a seat or retainer for an optical system shown in FIG. 17.

The optical system comprises a vertical tube 92 having a flange 93 which fits on the ring 91 as shown in FIG. 18. The tube and flange have been shown as molded from a single piece of transparent material, the lower face of the flange being stepped or rabbeted to fit over the ring 91. A 360 azimuth ring or plate 94 is secured by a small screw 94 to the flange 93 at the stepped portion so that the azimuth ring may be read through the transparent plastic. A north index line or member 95 is secured to the top of the case at the center line of the northattracting magnet so that it may register with the marking on the azimuth ring. The optical system is thus mounted so that it may be rotated about a vertical axis coinciding with the central vertical axis of the vessel 87.

The optical system includes a reticle 96 comprising a transparent disc marked with a plurality of spaced lines 97 parallel to the -180 axis of the azimuth ring as shown in FIG. 19. A magnifying lens 98 is provided for viewing the reticle when aligning the lines 97 with marks on objects such as a floating fragment indicated at 68a which is similar to the fragment 68 of FIGS. 13 to 15. The lens 98 is held on the tube 82 by a threaded collar 100 and the reticle 96 is secured to the lower end of the tube 92 by a threaded collar or retainer 101.

The liquid in the vessel 87 is selected to provide the required buoyancy of the objects to be floated, and in the case of plastic fragments may be water. The body of liquid fills the vessel to a level fairly close to the posi-- tion of the reticle to facilitate the registering of the reticle lines with identifying marks such as the line 69a on the fragment 68a. In the illustrated position of FIG. 19 the reference line 69a of the magnetized framment is at 45 to the center line of the magnetic poles and 81; thus, during solidification of the liquid, the earths magnetic field is indicated to have passed through the core from which the fragment 68a was taken at an angle of 45 to the reference line marked on the core. The true line representing the direction of the earths magnetic field on the core in its original position in the formation may now be marked on the core by drawing a line 45 to the original reference line 69a, essentially the same as the north arrow 77 of FIG. 15, the direction of the 45 polarity line being determined with respect to the fragments original position on the core.

The azimuth ring 94 includes a concentric slot 102 to receive the attachment screw 94', which slot permits adjustments in the position of the azimuth ring to allow for min-or corrections of alignment with the reticle lines and to compensate for the local declination of the earths magnetic field if desired. Such declination adjustments are usual in survey tools and allow for direct determination of true north rather than magnetic north; however, such adjustments can be used only with cores taken from essentially vertical well bores.

This instrument provides a simple, rugged and accurate device for determining the polarity or magnetic field direction of small fragments of solid material.

In the foregoing description of the methods and apparatus for determining the orientation of cores taken from the earths crust, it has been assumed that the core was taken from a substantially vertical well bore. In practice the bore or well may lie at very substantial angles of deflection from the vertical. Because the earths magnetic field may also be inclined below the horizontal by widely different angles depending on the location on the earths surface, it becomes necessary whenever the deflection of a bore hole exceeds say 5 from the vertical to introduce a correction in the determination of core orientation by the method of this invention.

It is common practice in survey-ing bore holes to determine the amount of deflection from the vertical and the direction of such deflection. This information is thus available from the standard well surveys. The amount of correction required for deflected bores may be determined as an angle with respect to the horizontal at which the orientation polarity line, determined as fully described heretofore, marked across the flat end of a core must be set to effect correct orientation of the core. The correction factor can be computed for any magnetic dip and any angle and direction of the bore hole deflection for use with the orientation method of this invention by means of the following formula:

Where:

C=desired correction angle in degrees I=deflection in degrees of bore hole from vertical near depth of cored rock D=dip in degrees of earths magnetic field below horizontal at location of well S=magnetic direction of bore hole deflection, es-

tablished as:

0 at east and west, at north, and +90 at south.

FIG. 20 is a chart prepared by using the above equation and indicates the correction factors for a location where the earths magnetic dip or inclination is 70. The chart has been drawn in four quadrants, east of north, west of north, east of south and west of south, respectively. The radial lines thus represent the magnetic compass direction of the deflection of the well bore. The amount of deflection of the bore is indicated in degrees by concentric circles and on this chart bore deflections up to 30 are indicated, as designated along the horizontal axis of the chart. The correction factors in degrees as calculated by the formula are indicated by the curved lines. In utilizing these correction factors, the core is positioned according to the data obtained from the well survey and, where the bottom of the bore is deflected in the western two quadrants, the core and the north end of the polarity line are rotated clockwise below the horizontal by the amount of the positive correction factor and counterclockwise above the horizontal by the amount of the negative correction factor. Conversely, Where the bottom of the bore hole is deflected in the eastern two quadrants, the core and north end of the polarity line are rotated counterclockwise below the horizontal for positive correction factors and clockwise above the horizontal for negative correction factors. This positions the north end of the polarity line at the proper rotational position according to the direction of the bore hole deflection with respect to the vertical northsouth magnetic plane. The zero correction or horizontal position of the polarity line on the core is represented by a curved line marked zero in the central part of the upper two quadrants of FIG. 20. All correction factors within these zero arcs are negative and those outside positive.

By way of illustration, a line 105 has been drawn on FIG. 20 representing a bore deflected north 62 east, The deflection of the bore as determined from well survey data is assumed to be 18, the line thus terminating at the 18 circle. This point is about halfway between the +20 and +30 correction curves so that a correction factor of +25 will be necessary to correct for the deflected bore hole. The orientation polarity line, for example 77 of FIG. 15, is determined as described in detail heretofore and the core is positioned in the attitude of the bore hole as determined from the usual well survey. Since the bore hole is deflected in an eastern quadrant and the correction factor is positive, the core is then rotated counterclockwise about its axis so that the north end of the polarity line is directed 25 below the horizontal, thus completely orienting the core in the position it occupied at the bottom of the deflected bore hole used as an example.

The somewhat egg-shaped zone about the intersection of the north radial line and deflection circle is an area of substantial coincidence of the inclination or dip of the earths magnetic field and the bore hole deflection so that the lines of the earths field run substantially along the core and no reliable indication of direction or orientation of the core may be secured in this zone. When survey data indicate that the well bore is within this zone, it is, of course, necessary to determine the orientation of the core by other methods than relying on the earths magnetic field.

From the foregoing it is readily apparent that the method of this invention together with the apparatus thereof provides a simple, quick and reliable method for determining core orientation which requires minimum interruption of the operation of the standard drilling or coring procedures or equipment. This method greatly shortens the time for determining core orientation and is readily adaptable to use in the field.

While the invention has been described in connection with specific forms of the method and embodiments of the apparatus, various modifications and other applications will occur to those skilled in the art. Therefore it is not desired that the invention be limited to the specific methods and constructions illustrated and described and it is intended by the appended claims to cover all modifications which fall within the spirit and scope of the invention.

I claim:

1. The method of utilizing the earths magnetic field for determining the orientation of a core taken in core drilling which comprises mixing a mass of finely divided magnetic particles having high coercive force in a liquid having the characteristic of solidifying Within a predetermined period of time and having a further characteristic of adhering securely to rock surfaces, placing a body of the liquid mixture on the bottom of the hole to be cored, withdrawing from the zone of the bottom of the hole all magnetic material other than that in said mixture whereby the magnetic particles are allowed to align with the earths magnetic field, allowing the liquid to solidify, coring the hgle, removing the core with the solidified mixture adhering thereto, placing an identifying mark on the surface of the solidified mixture, removing a fragment from the solidified mixture bearing a portion of the identifying marking, magnetically determining the direction of alignment of the magnetized particles held in said fragment of the material, and utilizing said identifying marking on said core and on said fragment for locating the direction of the earths magnetic field with respect to said core to determine the original orientation of the core prior to removal from the earth.

2. The method for determining the orientation of a core as set forth in claim 1 wherein said identifying marking is made to include a straight line extending across the material at the end of the core and including the step of marking said material on said core with a second straight line at an angle to said first-mentioned straight line to indicate the direction of the earths magnetic field through said material and said core in its position prior to coring.

3. The method for determining the orientation of a core as set forth in claim 1 wherein said magnetic particles are mixed with said liquid prior to their magnetization and including the step of magnetizing the particles before placing said mixture on the bottom of the bore hole.

4. The method for determining the orientation of a core as set forth in claim 1 including the step of confining the mixture of liquid and magnetic particles in a con tainer under pressure, disposing the container in the hole adjacent the bottom thereof, and opening the container to effect discharge of the mixture under pressure into its position on the surface to be cored.

5. The method for determining the orientation of a core as set forth in claim 1 including the step of confining the mixture of liquid and magnetic particles in a closed container, disposing the container in the hole in a position adjacent to the bottom thereof, and opening the container to discharge the contents and place the liquid on the bottom of the hole.

6. The method for determining the orientation of a core as set forth in claim 5 wherein said container is constructed of drillable material and said step of opening the container is effected by breaking the container at the bottom of the hole.

7. The method for determining the orientation of a core taken in core drilling at a substantial angle to the vertical and including mixing particles of a magnetic material of high coercive force in a solidifiable liquid having the characteristic of adhering firmly to rock upon solidification, placing a quantity of the liquid mixture on the rock at the bottom of a bore hole, said method further including the step of magnetizing the particles before placing the liquid on the rock, removing all magnetic material from the Zone of the emplaced liquid, allowing the liquid to solidify thereby retaining the magnetic particles in positions of alignment with the earths magnetic field, coring the hole, placing an identifying mark on the solidified material of the removed core, utilizing a portion of the material including the identifying mark for determining the direction of the component of the earths magnetic field normal to the axis of the core at the location of the coring, marking the core with a straight line indicating the direction of said component of the earths magnetic field therethrough, and determining the correction angle C for positioning the north end of said straight line with respect to the horizontal by the following formula:

(sin 1) (tan D) tan C (cos I) (tan S)+ cos S Where:

tablished as:

at east and west, -90 at north, and +90 at south,

positioning the core in accordance with its deflection as determined by well survey and rotating the core to position the north end of said straight line at said angle C with respect to the horizontal in its proper rotational position according to the direction of the bore hole deflection with respect to the vertical north-south magnetic plane.

8. The method for determining the orientation of a core taken in core drilling which comprises providing a mixture of magnetized particles of a material of high coercive force in a liquid having the characteristic of adhering firmly to rock upon solidification, placing a quantity of the liquid on the rock at the bottom of a bore hole, removing all other magnetic material from the zone of the liquid and allowing the liquid to solidify to retain the magnetic particles therein in positions of alignment with the earths magnetic field, removing the core and placing an identifying mark on the surface of the solidified liquid, removing a fragment from the solidified mixture bearing a portion of the identifying marking, floating said fragment on a liquid in a relatively strong magnetic field to determine the orientation of the magnetic particles in said fragment, and utilizing the identifying marking on said core and on said fragment for locating the direction of the earths magnetic field with respect to said core and thereby determining the original orientation of the core before removal from the earth.

9. The method of utilizing the earths magnetic field for determining the orientation of a core taken in core drilling which comprises providing a mixture of a mass of finely divided magnetized particles of a ceramic material having high coercive force in a liquid having the characteristic of solidifying within a predetermined period of time and having a further characteristic of ad- =hering securely to rock surfaces, placing a body of the liquid mixture on the bottom of the hole to be cored, withdrawing from the zone of the bottom of the hole all magnetic material other than that in said mixture whereby the magnetic particles are allowed to align with the earths magnetic field, allowing the liquid to solidify, coring the hole, removing the core with the solidified mixture adhering thereto, placing an identifying mark on the surface of the solidified mixture, removing a fragment from the solidified mixture hearing a portion of the identifying marking, magnetically determining the direction of alignment of the magnetized particles held in said fragment of the material, and utilizing said identifying marking on said core and on said fragment for locating the direction of the earths magnetic field with .respect to said core to determine the original orientation of the core prior to removal from the earth.

10. The method of determining the original orientation of a core taken in core drilling which comprises providing a liquid having the characteristics of solidifying within a predetermined period of time and of adhering securely to rock surfaces and having therein a dispersion of finely divided magnetized particles of high coercive force, placing the liquid on the rock at the bottom of the hole to be cored, removing from the bottom Zone of the hole any magnetic material other than that in said liquid, allowing the particles to become aligned with the earths magnetic field and after the end of said predetermined time and the solidification of the liquid coring the hole and removing the core with the solidified liquid thereon, marking the surface of the solidified mixture to indicate an axis transverse to that of the core, cutting from the solidified mixture a fragment bearing an identifiable portion of the marking, providing a magnetic field of high intensity, suspending the fragment for free rotation within the field on an axis transverse to the marked surface thereof and to the direction of the field, then when the fragment is stationary in the field determining the angle between the direction of the field and the indicated axis of the marking and thereby determining the direction of the earths magnetic field with respect to the core in its original position and thus the original orientation of the core.

11. The method of determining the original orientation of a core taken in core drilling as set forth in claim 10 wherein said magnetized particles are selected to have a low density as compared with that of iron.

12. The method of determining the original orientation of a core taken in core drilling which comprises providing a liquid having the characteristics of solidifying within a predetermined period of time and of adhering securely to rock surfaces, providing a mass of finely divided particles of magnetic ceramic material having high coercive force, forming a mixture of the liquid and a quantity of the ceramic particles in a proportion of the order of .1 to 1 gram per liter of the liquid, placing the liquid on the rock at the bottom of the hole to be cored, said method further including the step of magnetizing said particles prior to the placing of the liquid on the rock, removing from the bottom of the hole any magnetic material other than that in the liquid, allowing the magnetized particles to become aligned with the earths magnetic field and after the end of said predetermined time and the solidification of the liquid coring the hole and removing the core with the solidified liquid thereon, marking the surface of the solidified mixture to indicate an axis transverse to that of the core, cutting from the solidified mixture a fragment bearing an identifiable portion of the marking, providing a magnetic field of high intensity, suspending the fragment for free rotation Within the field on an axis transverse to the marked surface thereof and to the direction of the field, then when the fragment is stationary in the field determining the angle between the direction of the field and the indicated axis of the marking and thereby determining the dierction of the earths magnetic field with respect to the core in its original position and thus the original orientation of the core.

13. The method of determining the original orientation of a core taken in core drilling which comprises placing on the rock at the bottom of a well bore a quantity of liquid having the characteristics of solidifying within a predetermined period of time and of adhering securely to rock surfaces and having therein a dispersion of finely divided magnetized particles of a material of high coercive force, allowing the liquid to solidify and retain the particles in a condition of magnetic alignment with the earths magnetic field, coring the rock and removing the core with the solidified material adhering thereto, suspending at least a portion of the material for free rotation about an axis representative of the longitudinal axis of the core, subjecting the suspended material to a magnetic field of high intensity and transverse to said axis, and utilizing the aligned position of the material in the field for determining the original orientation of the core.

14. The method of determining the original orientation of a core taken in core drilling as set forth in claim 13 wherein said magnetized particles are of a ceramic material having a low density as compared with that of 10 2 310 543 iron and wherein the quantity of material is small with respect to the volume of liquid.

References Cited by the Examiner UNITED STATES PATENTS Vacquier 1'7544 X Jones 16629 Downs et al. 25262.5 Leverenz et a1 252--62.5 Marchand et a1. 32414 Rothacker 32414 Brady 175-44 Martinez 17544 CHARLES E. OCONNELL, Primary Examiner.

Claims

1. THE METHOD OF UTILIZING THE EARTH''S MAGNETIC FIELD FOR DETERMINING THE ORIENTATION OF A CORE TAKEN IN CORE DRILLING WHICH COMPRISING MIXING A MASS OF FINELY DIVIDED MAGNETIC PARTICLES HAVING HIGH COERCIVE FORCE IN A LIQUID HAVING THE CHARACTERISTIC OF SOLIDIFYING WITHIN A PREDETERMINED PERIOD OF TIME AND HAVING A FURTHER CHARACTERISTIC OF ADHERING SECURELY TO ROCK SURFACES, PLACING A BODY OF THE LIQUID MIXTURE ON THE BOTTOM OF HE HOLE TO BE CORED, WITHDRAWING FROM THE ZONE OF THE BOTTOM OF THE HOLE ALL MAGNETIC MATERIAL OTHER THAN THAT IN SAID MIXTURE WHEREBY THE MAGNETIC PARTICLES ARE ALLOWED TO ALIGN WITH THE EARTH''S MAGNETIC FIELD, ALLOWING THE LIQUID TO SOLIDIFY, CORING THE HOLE, REMOVING THE CORE WITH THE SOLIDFIED MIXTURE ADHERING THERETO, PLACING AN IDENTIFYING MARK ON THE SURFACE OF THE SOLIDFIED MIXTURE, REMOVING A FRAGMENT FROM THE SOLIDFIED MIXTURE BEARING A PORTION OF THE IDENTIFYING MARKING, MAGNETICALLY DETERMINING THE DIRECTION OF ALIGNMENT OF THE MAGNETIZED PARTICLES HELD IN SAID FRAGMENT OF THE MATERIAL, AND UTILIZING SAID IDENTIFYING MARKING ON SAID CORE AND ON SAID FRAGMENT FOR LOCATING THE DIRECTION OF THE EARTH''S MAGNETIC FIELD WITH RESPECT TO SAID CORE TO DETERMINE THE ORIGINAL ORIENTATION OF THE CORE PRIOR TO REMOVAL FROM THE EARTH.