US2228623A

US2228623A - Method and means for locating perforating means at producing zones

Info

Publication number: US2228623A
Application number: US342320A
Authority: US
Inventors: George H Ennis
Original assignee: ROBERT V FUNK
Current assignee: ROBERT V FUNK
Priority date: 1940-06-25
Filing date: 1940-06-25
Publication date: 1941-01-14
Anticipated expiration: 1958-01-14

Description

G. H. ENNIS Jan. 14, 1941.

METHOD AND MEANS FOR LOCATING PERFORATING MEANS AT PRODUCING ZONES Filed June 25, 1940 4 Sheets-Sheet 1 050265 /1 f/v/v/s INVENTOR.

ATTORNEY G. H. ENNIS Jan. 14, 1941.

METHOD AND-MEANS FOR LOCATING PERFORATING MEANS AT FRODUCING ZONES 4 Sheets-Sheet 2 Filed June 25, 1940 FIRING J com-Rm. /46 1344 37 135 IN VENT OR.

A TTORNE Y Jan. 14, 1941. H, N 2,228,623

METHOD AND MEAN$ FOR LOCA'I'ING PERFORATING MEANS AT PRODUCING ZONES Filed June 25, 1940 4 Sheets-Sheet 3 Fzg' "4 III! 79 650/265 /7. f/wv/s,

I N VEN TOR.

ATTORNEY e. H. ENNIS 2,228,623

METHOD AND MEANS FOR LOCATING PERFORATING MEANS AT PRODUCING ZONES Jan. 14, 1941.

Filed June 25, 1940 4 Sheets-Sheet 4 IN VEN TOR.

' ATTORNEY Patented Jan. 14, 1941 PATENT OFFICE METHOD AND MEANS FOR IDCATING PERFOBATING MEANS AT PRODUC- ING ZONES George H. Ennis. Long Beach, Calif., assignor of one-half to Robert V. Funk, Long Beach, Calif Application June 25, 1940, Serial No. 342.3%

17 Claims.

My invention relates broadly to method and means for establishing positions within deep wells, and relates in particular to a method and apparatus for use in bringing a well into production.

In the present art of producing oil from subterranean formations, it has now become accepted practice to drill the well into or through one or more oil bearing formations, to set the casing in the well and then perforate the casing to permit entry of oil from one or more of the formations. For the purpose of perforating casing after it has been set in a well, several different types of equipment have been developed, including mechanical perforators having spikes or blades which are forced by heavy pressure out through the wall of the casing, and gun perforators by which bullets are shot through the casing wall. In the use of either of these types of perforators, the perforating device is lowered into the casing on the lower end of a suspension member, either tubing or cable. As the device is lowered into the well the length of the suspension member lowered into the well is measured, for the purpose of determining the distance of the device from the top of the well at any time. This determination of the position of the perforator is only approximate, in view of different factors involved. The suspension member, although it is made from steel, is elastic, and stretches in accordance with the load applied thereto. Accordingly, when any device, such as a perforating tool, is lowered into a well by means of a cable, the methods at present used do not dependably indicate the distance of the device below the surface of the ground, even though corrections have been made in footage tabulations in accordance with the involved theoretical factors of deviation.

How the foregoing presents a problem in the perforating of oil well casings will be seen from the following. The log of a well may indicate that an oil sand is positioned between levels which are indicated as being at different distances from the top of the well. These distances shown by the log of the well, as a general rule are found to be inaccurate. The operator of the perforating device, using the log as a guide, must position the perforating device in the well by measuring the length of the suspending cable paid out during the lowering of the device, and making corrections to compensate for factors of variation including cable stretch and flotation. The errors of dimensions indicated on the log of the well and the errors involved in the positioning of the perforating device by means of a cable may be cumulative. with the result that when the perforator is actuated it will fail to perforate the casing between the levels constituting the limits of the oil sand, or the perforations may entirely miss the oil sand and, further, may connect the interior of the casing with a water bearing stratum. It is an object of the present invention to eliminate uncertainty in the locating of a device of this type in a well by providing a method and apparatus whereby the device may be very accurately positioned in a well with relation to a specified zone or position.

It is an object of the invention to provide a method and apparatus whereby a marker is established and/or identified with relation to a selected zone which is intersected by the well, and whereby this marker is employed to locate a tool or device in a desired positionrelative to the zone, by direct reference to the marker, thereby avoiding the errors resulting from the locating of the tool or device with reference to the top of the well.

It is an objectof the invention to provide a method and apparatus whereby a device of the general type above mentioned may be positioned accurately with relation to a selected position or zone below the surface of the ground, and wherein a marker is established in proximity to the zone or location, the establishing of this marker involving determination of the distance from the marker to the zone or position, and then locating the device certainly and accurately in the selected zone or position through employment of the simple expedient of placing the device in a desired distance relation to the marker.

A further object of the invention is to provide a method and apparatus whereby a casing perforator is lowered into a well and is actuated when it is in a selected position relative to a marker established at a distance below the surface of the ground, thereby making it possible to assure practical accuracy in locating the perforations in the casing opposite a selected oil sand or in a selected production zone.

It is an object of the invention to provide a process and apparatus whereby a perforator may be accurately located relative to a selected production zone by establishing a marker in relation and proximity to the production zone, then lowering a perforator into the casing, and also lowering into the casing a marker locating means capable of producing an indication sensible to an operator stationed at the top of the well when it is brought to a position coinciding with the marker, and thereafter moving the perforator into such position relative to the located marker as to lie in the production zone. It will be recognized that this marker may be above or below, or within the limits of, the production zone, and the accurate positioning of the perforator is simply accomplished by spacing it a required distance from the marker, which distance may vary from zero value to a value of several hundred feet.

It is an object of the invention to provide a method such as set forth in the preceding paragraph wherein the marker locating means is connected to the perforator so as to move therewith,

- and wherein the combined marker locating and perforating assembly is lowered into the well casing to the point at which the marker is located, and is then moved from this location the distance required to bring the perforator into the selected production zone.

It is an object of the invention to provide a method and apparatus for accurately locating a device in a well by first establishing below the surface of the ground a marker in known relation to a selected stratum, moving the device down the well to a marker position, and then moving the device from this marker position the prescribed or computed distance necessary to bring the device accurately into the final position thereof. The term "marker position employed in the foregoing is any position adjacent or close to the marker which may be determined by suitable locating means of one of the various types to be hereinafter described.

Further objects and advantages of the invention will be brought out in the following part of the specification.

Referring to the drawings which are for illustrative purposes only.

Fig. 1a is a schematic view showing a portion of a casing extending through strata, one of which comprises an oil sand from which production of oil is desired.

Fig. 1b is a representation of a log obtained prior to the placing of the casing in the well.

Fig. 1c is a representation of another log of the well section shown in Fig. 1a after the casing is set.

Fig. 1d is an electrical log or stratagraph taken after installation of the casing in the well section shown in Fig. 1a in conjunction with the location and operation of a perforator in the well casing.

Fig. 2 is a partly sectioned view showing the details of the testing device which is connected to the upper end of the perforator.

Fig. 3 is a schematic illustration showing a practice of my invention wherein radio active materials are employed as markers.

Fig. 4 is a schematic view showing another method of practicing my invention.

Fig. 5 is a schematic view showing my invention in use for accurate location in a well of a device other than a perforator.

Fig. 6 is a schematic view of a section of the well showing a manner in which markers may be positioned in sands.

Fig. '7 is a sectional view of diagrammatic character showing a cementing device which may be used in the exploration of a cased well.

Fig. 1a is illustrative of a condition met in the drilling of wells. The well casing l0 intersects a stratum II of shale, below which there lies an oil bearing stratum or oil sand I2, An electrical graph or log l3, prepared prior to the setting of the casing Ill shows that the upper and lower limits of the shale II are respectively at 10,853 feet and 10,901 feet below the top of the well, and that the upper and lower limits of the oil sand l2 are respectively 11,050 and 11,120, the distance from the bottom of the shale to the top of the oil sand being 149 feet (11,05010,901=149) The excursions I3b, Nb, and I51) of the curve I3 clearly identify the position of the shale II on the log Fig. 1b, and on this log the excursions Ito and I lb clearly indicate the limits of the oil sand I2. The log Fig. 10, comprising a graph or curve I8, is placed adjacent the graph I3 so that the excursions I30, I40, and I50 indicating the shale II, will lie opposite the corresponding portions of the graph I3. When this is done, it will be found that the excursions I60 and Ho lie adjacent the excursions IBb and Nb of graph I3. Although the graphs I3 and I8 agree in the portions thereof indicating the shale II and the oil sand I2, the graph I8 shows these indications at a different distance from the top of the well, than is shown by graph l3. For example, the lower limit of the shale II is indicated by graph I3 as being at a level of 10,901, but in graph I8 the point I50 indicating the lower level of the shale II occurs at the measurement 10,880 or 21 feet above the point I5b of graph I3. All of the points of interest on the graph l8 appear to be 21 feet above the positions indicated for them on the graph I3. For example, the upper limit of the oil sand I2, appearing at 11,050 on graph I3 is to be found at 11,029 on graph I8, and the lower limit -of the oil sand I2, appears to be raised from 11,120 to 11,099. It is to be noted, however, that in each of the graphs l3 and I8 the thickness of the shale II is indicated as 48 feet, the thickness of the oil sand I2 is indicated as 70 feet, and that the distance from the point I5c to the point He of graph I8 is the same as the distance from point I5b to the point Nb of graph I3, namely, 219 feet, establishing that the distance from the lower limit of the shale II to the lower limit of the oil sand I2 is of this value. Furthermore, the logs represented by the curves I3 and I8, correlated with the drillers log of the well, both clearly show the distance from the lower limit of the shale II to the upper limit of the oil sand I2 to be 149 feet, regardless of the fact that the charts I3 and I8 show the shale and the oil sand at different levels from the top of the well.

Due to changes in cable lengths and other sources of error, the logs shown in Figs. lb and 1d do not establish the distances of the selected shale and oil bearing strata from the surface of the ground, but they definitely establish, either by themselves or in combination with drillers records, the correlative positions of the limits of the shale and oil bearing strata. If an operator were to now lower a perforating device down into the casing l0, computing the necessary amount of cable 20 which must be fed into the well to bring the perforating device to a position adjacent the oil sand l2, he would have no assurance that the perforating device is in this intended position, for this operation would be subject to all the factors of error encountered in the lowering of the device into a well by means of a suspension member such as a cable or string of tubing.

My present invention provides a simple method and apparatus whereby all error in the location of the device relative to the oil sand I2 is substantially eliminated. I accomplish this valuable result by establishing a marker in proximity to the oil bearing formation i2, which marker may be readily located at any time and may be used as a guide for the positioning of the perforator. In the present instance the graphs i3 and H3, or either of them singly, establish the shale stratum II as a marker which may be readily located at any time either before or after the setting of the casing [0. Accordingly, I lower a perforating device such as a. perforating gun 2| down into the casing ID, in association with a marker locating means 22, to locate the shale II, or in this instance the lower limit thereof, after which the perforating gun 2| may be moved down into the zone defined by the upper and lower limits of the oil sand l2 and there actuated. In Fig. 2 I have schematically shown a combined marker locating and perforating means I! consisting of the gun perforator 2| and the locating means 22 of Fig. 1a. The gun 2| may be of any desired type such as now employed in the perforating of casing. Such a gun, as now well known to the art, has one or more gun barrels with associated powder chambers to carry the projectiles and firing charges, with means for setting off the powder charges at a desired time. In Fig. 2 I show the cable 28 as having an insulated conductor 24 extended therethrough. The lower end of this conductor 24 is carried into the top of the gun perforator and connected to a terminal 25 of the firing switch 23 of the gun, and the metal sheath 21 of the cable is connected to the upper part of the body of the gun as indicated by dotted lines 28.

The locating means 22 comprises a sleeve of insulating material, having an opening'therethrough of such size that it may he slipped over the cable 20, a metal elctrode 3| disposed centrally upon the sleeve 30, and

sleeves

32 and 33 which surround the sleeve 30 above and below the electrode 3|. A conductor 34 is connected to the electrode 3| and is carried down between the sleeve 33 and the lower portion of the sleeve 38 to the lower end of the locating means 22. The lower portion of the conductor 34 is carried through a suitable seal or packing device 35 at the upper end of the body of the gun 2| and as indicated by dotted lines 36 is connected to the terminal 25, so as to be then in connection with the conductor 24.

' As diagrammatically shown in the upper part of Fig. 2, the conductor 24 may be connected to a movable switch member 31 adapted to be brought into engagement with a contact 38 which is connected with an electrical recorder 39 having a ground circuit consisting of a conductor 48 which leads to a contact 4|, a movable switch member 42 and a ground connection 43 which may be connected to the earth or to the casing III. A contact 44 ,is placed in spaced relation to the contact 38 and is connected to the firing control 45 by means of a conductor 43, and from the firing control 45 a conductor 41 is extended to the sheath 2|.of the cable 28 to complete the firing control circuit for the gun 2|.

The manner of operation of the combined locating and perforating means is as follows. The assembly comprising the gun 2| and the locating means 22 is lowered down through the well and through the casing Ill, and as the level of the stratum II is approached, the movable switch members 31 and 42 are moved into engagement with the contacts 38 and 4| thereby closing the recording circuit which includes the stratagraph recording device 33 which will scribe a graph or curve 43 of the general character shown in Fig. 1d. As the electrode 3| moves downward within the casing Hi, the electro-potential changes in the recording circuit will produce a record or graph which may be correlated with the graphs i3 and I8. It is found that with present equipment, the existence of the casing |ll between the electrode 3| and the formation may under some conditions have a damping effect on the electrical changes in the recording circuit and that the graph obtained thereby will not be as complete in detail as a graph made by the open hole method, for example, a graph such as shown at l8.

However, the graph obtained as the result of the operation of equipment of the character shown in Fig. 2, within the casing of a well, will clearly distinguish certain types of formation, such for example, as shale. Therefore, the shale II has been established as the marker in the present instance. As the electrode 3| approaches the upper level of the shale H the curve will move leftward as indicated at 58, and a point will be formed at |3d corresponding to the point |3b and |3c of the graphs l3 and I8. Likewise, excursions l3d, 4d, and |5d will be formed, thereby definitely locating the marker Ii. When the electrode 3| reaches a position at the lower limit of the shale H, as shown in Fig. la, the scribing needle of the recorder 39 will be at the point or excursion l5d, thereby bringing to the operator at the top of the well knowledge that the electrode 3| is in a starting position, or in an initial position from which the assembly of elements 2| and 22 may be moved to bring the gun 2| into cooperation with the oil sand I2. Ordinarily the electrode 3| is lowered some distance below the shale so that'the portion 43' of the graph 49, below the point I512, will be scribed. The correlation of the points |3d, Md, and |5d to similar excursions found in the graphs i3 and I8 having been recognized, the assembly of members 2| and 22 will be at this time moved upward to retrace the lower portion 43' of the graph 43 in reverse direction, the upward movement of the cable 20 being stopped when the point I512 is reached, thereby assuring that the marker, in this instance the lower level of the shale- II, has been located and that the perforating gun 2| is in "marker position. By marker position is meant that the gun 2| is in a known relation to the marker and that it is ready for such movement as will bring it into the proper position for firing. Accordingly, if the lowermost barrel 52 of the gun 2| is 10 feet below the electrode 3|, the downward movement of the gun 2| to bring this barrel 52 to a position adjacent the lower limit of the oil sand |2 will be 10 feet less than the distance from the marker to the lower limit of the oil sand, or, namely, 209 feet. The change in the length of the cable 20 during the movement thereof through a distance of 209 feet will be so small that the barrel 52 may be readily located with practical accuracy at the point desired, and the gun 2|, as indicated by dotted lines 2 la in Fig. 1a, may, with reference to the marker comprising the lower limit of the shale, be very accurately positioned at any point relative to the marker, within the limits of 500 or 1000 feet above or below the same, without having actual knowledge of the distance of the gun 2| from the top of the well. Under some conditions the active stratum may serve as its own marker in the positioning of a fluid entry means, but it is often found that an electrically prepared graph taken after the setting of the casing, does not dependably indicate oil sands; whereas, other strata are clearly indicated.

In Fig. 1a I have shown an embodiment of my invention wherein a selected stratum is estab- I lished as a marker. In Fig. 3 I show a form of the invention wherein establishment of a marker includes the placing of the marker in the formation or in a structural member of the well, such as the casing. In Fig. 3 I have shown a casing 50 having a shoe 8|, with a casing member or liner 82 projecting downward from the casing 88 to be used as a marker, a small body 83 of radio active material may be connected to the lower part of the casing 88, for example, the body 83 may be held in a recess in the shoe 6|. Likewise, a body of radio active material 54 may be placed in the formation as desired. For example, the body 54 may be a projectile which has been shot into the formation by use of a gun, preferably before the casing is set. Either of the

markers

83 or 84, or both of them, may be correlated with a selected stratum, such as the oil sand 65, by information taken from the drillers log or from an electro-log 86 made prior to the setting of the casing 82, so as to show the strata below the shoe BI and to relatively accurately show the distances between the

markers

83 and 64 and the upper and lower limits of the stratum 65. In this instance, a stratum 51 of radio active material may be employed as a marker and this marker may be correlated with the

markers

63 and 64, making it possible to very accurately locate a gun or other device 88 in the well, by employing in conjunction with the gun a locating means comprising a device 68 which is sensitive to radio active emissions, the device 58 being connected through conductors l8 and II with a sensitive recording device I2 in accordance with the general teachings of the U. S. Patent No. 2,133,776, granted October 18, 1938, to J. C. Bender.

A body of metal may be placed in the earth 5 and established as a marker. Such body of meal may be a block of iron, or may be a portion of a casing member. In Fig. 4 I show an outer casing I8 having an iron shoe II which may be established as a marker by correlating it with the strata, and I show a liner or casing 12 having collars such as indicated at I3, and a bottom I4 formed by a plug I5, which by proper correlation with the strata may be established as markers which may be readily located.

In Fig. 4 I have diagrammatically shown an induction device for locating a marker, this induction device including a coil I8 connected in circuit through conductors l1 and 18 with a recording device I8. The coil I6 is wound upon a c-shaped field member or core 80. As the coil I5 is moved within the casings I and 12, in association with a device such as a perforating gun 8!, the concentration of the magnetic field will be changed by the presence of any body of magnetic material encountered, with a resulting change in the inductance of the coil 15 and a change in the flow of current through the connected electro-responsive parts of the recording device I8. In Fig. 4 I have shown adjacent the

casing members

10 and 12 an open-hole graph taken after the setting of the casing 18 and prior to the placing of the liner or casing 12, the portion 83 of the graph 82 definitely establishing the position of the shoe II as a marker in correlation with the strata. After setting of the casing member 12, the upper end 84 thereof, the shoe I I, and the collars 13 of the casing member 12 may be employed as markers, for they may be all esablished as such with relation to the formation. For example, in the making up of the casing member 12, the pipe sections forming the same may be measured so that the distances between all of the collars I3 will be known. Accordingly, thereafter the position of each collar 13 relative to the oil sand 86 may be be readily computed, with reference to the shoe ll the distance of which from the oil sand 88 is definitely established.

In Fig. 4 I have shown a graph 8'! representative of the graph scribed on a strip of paper by the needle of the recording device 18 as the coil I6 is lowered in the casing members Ill and I2. When the coil I reaches the upper end of the cashing member I2 there will be a rightward excursion of the graph at 88 and a further excursion at 88 as the coil 16 passes the shoe ll. Thereafter an excursion of the graph such as shown at 80 will locate each collar 13. By use of the general principles disclosed relative to Figs. 1 and 3, the arrangement shown in Fig. 4 may be employed to accurately position a device, such as the device 8! opposite a selected stratum, such as the oil sand 86, and an especial advantage of the apparatus and method disclosed is that in the perforating of the casing member 12 the collars 13 may be employed as markers in locating the gun and also as a means for locating the collars 13 so that they may be avoided in perforating the casing.

In Fig. 5 I show a casing 8|, set in a well and which has been perforated at 82 for the purpose of exploration. The perforation 82 has been formed, as by the shooting of a projectile therethrough, at a prescribed distance from an established marker such as a collar 13', the upper or lower end of the casing 8| or the shoe 'II' at the lower end of an outer casing so as to establish communication with the sand stratum 83 to determine if oil may be obtained therefrom. It having been found that the production from the stratum 83 comprises water, the form of my invention shown in Fig. 5 makes it possible to readily close the perforation 82 by the application of cement. A cementing head 84, having expansible sealing or packing means 85 and 86 above and below outlet ports 87 in the cylindrical wall thereof, is connected to the lower end of a string of tubing 88 by means of a short section 88, this section having a stop or shelf I08 near the lower end thereof and being of non-magnetic metal, such as brass. When the cementing head has been lowered substantially to the position of the selected marker, for example, the collar I3, a. locating means of inductive character, as disclosed in Fig. 4, is lowered into the tubing 88 by means of a cable I82 having a conducto therein, and this inductive type of locating means 16' is brought to rest in a known position in engagement with the stop I08. The assembly of parts comprising the head 84 and the marker locating element 16' is then moved within the casing 8i until the marker 13 is located, thereby bringing the cementing head 84 into a known position, which may be referred to as the marker position. With the location of the cementing head 84 relative to the perforation 82 thus known, the head 84 is then lowered the desired distance from its marker position to bring it into a position of cooperation with the aperture 82, as shown in Fig. 5, after which the locating device may be withdrawn from the tubing 38 and a suitable amount of cement mixture may be pumped down through the head and out through the perforation 82 to close the same, leaving the well in condition for further exploration proceedings consisting in the shooting of projectiles through the wall ofthe casing 3| into other strata and inspecting the production from such strata, and closing such of the perforations which are found to make connection with nonproductive strata.

An important advantage of my present invention is that it provides a means for a thorough exploration of a well to discover and bring into production oil sands which under ordinary circumstances are neglected. In one practice of the invention markers may be established prior to the setting of the casing, by placing selected marker means in selected formations. In Fig. 6 I show a bore hole prior to the setting of a casing, this bore hole intersecting a number of sands IIO, III, and H2. During the drilling process, or when the same is completed prior to the setting of'the casing, markers may be placed in these sands so that after the casing is set each of the sands may be readily located and tested in the manner set forth in the description of Fig. 5. As shown in Fig. 6, a combined testing and perforating device IQ of the character shown in Figs. 1 and 2 is lowered into the hole I00 and an electrometrlc log or graph such as shown at I8 in Fig. 1c is prepared. On such log many sands are indicated, but it is not always possible to determine from the log itself whether these sands are oil sands or water sands. However, the gun 2| is operated at proper times to fire into each of the sand formations a projectile I I3 of or containing an active material, such as a radio active material which will make possible the accurate location of each projectile or marker at a later time, for example, after the casing is set.

After the setting of the casing a perforating gun 68, with an associated marker locating means 60, such as shown in Fig. 3, may be lowered into the casing and any one of the markers II3 may be located and one or more projectiles may be fired through the casing to perforate the casing adjacent the oil sand containing the selected marker. Then the necessary steps may be taken to determine the type of fiuid, if any, contained in the selected sand, and if the selected sand should contain water instead of oil, the perforations made thereat for the purpose of test may be closed by the application of cement, and at the position indicated by another of the markers 3 other test perforations may be made in the casing. By a repetition of the process discussed in the foregoing the well may be carefully explored. It.wil1 be recognized that the placing of the radio active markers I I2 may be performed after the setting of the casing. For example, the combined perforating and testing or marker 10- cating device I9, shown in Fig. la, may be employed to'first shoot a radio active bullet, or several of them, through the wall of the casing into the formation. The formation may be tested through the openings thus formed and if an oil production is obtained other perforations may be made in the casing at the production stratum thus discovered, or if an oil production is not obtained from this stratum, the radio active bullets may be employed as markers whereby the test perforations may be located and then closed, as by the application of cement.

In Fig. 7 I have shown diagrammatically a combined testing, cementing and marker locating device I20, comprising a casing I2I secured to the lower end of a tubular cementing head I22, having packing means I23 at the ends thereof, or I respectively above and below cement outlet ports. 5 'I24 in the side wall thereof. The casing I2I has a cell I25 which is responsive to a selected character of electronic emanation, in accordance with the type of material employed in a projectile I28 by which a perforation I21 has been previously made in acasing I28. For example, the projectile I20 may comprise a radio-active or activateble material. The cell I2! is connected by conductors I30 and I3I with contacts I32 and I32 disposed within the cementing head I22. After this combined cementing and marker locating device I20 is lowered in the casing I28 to approximately the level of the marker I28, circuit forming means I35 may be lowered through the tubing I38 by which the device I20 has been lowered in the casing I28. This circuit forming means I35 comprises a bar or weight I31 carried at the lower end of a cable I38 which has conductors I38 and I40 extending therethrough. At the lower end of the member I31 annular contacts I and I42 are carried in such positions that when the member I31 reaches the bottom of the cementing head I22, these contacts MI and I42 will engage the contacts I32 and I33, thereby connecting the conductors I30 and I3I with the cable conductors I30 and I40, with the result that the responsive element I25 will be placed in circuit with the electrical parts of a recording instrument 12' located at the top of-the well to which the conductors I39 and I40 are connected.

The combined cementing and marker locating device may be then moved within the casing I28 until the recording device 12' indicates that the responsive element I25 is in the horizontal plane defined by the marker I20. The operator, having knowledge of the distance from the responsive element I25 to the center of the cementing head I22 may then lower the device I20 a sufilcient distance to bring the cementing head I22 into centralized relation to the perforation I21; whereupon, the circuit forming means I35 may be withdrawn. The pressure in the tube I38 may be then reduced to make a test through the opening I21, and if the formation is found to be nonproductive, cement may be forced down through the tubing I38 and out through the openings I24 of the cementing head I22 of the perforation I21. If the formation is found to be productive, the

device I20 will be withdrawn from the casing I28 5 and a perforating device of the type herein disclosed may be employed to increase the number of perforations in the casing I28 communicating with the productive formation, using the proiectile I28, or other marker, as a guide for this operation.

I claim as my Invention:

1. In a method of producing a fiuid from the earth, the steps of forming in the earth a bore relation of said production stratum and said marker, whereby said perforating will connect the interior of said casing with said production stratum.

2. In a method of producing a fluid from the earth, the steps of: forming in the earth a bore hole which intersects a production stratum; preparing a log of the formations intersected by said bore hole, said log showing said production stratum, said log including an electrometric record of the formations intersected by said bore hole; establishing a stratum as a marker below the surface of the earth and in a known relation to said production stratum; setting a casing in said bore hole so as to intersect said production stratum; locating said marker by electrometric means; and then perforating said casing in a position correlated with said marker and determined in accordance with said known relation of said production stratum and said marker, whereby said perforating will connect the interior of said casing with said production stratum.

3. In a method of producing a fluid from the earth, the steps of: forming in the earth a bore hole which intersects a production stratum; establishing a marker below the surface of the earth and in a known relation to said production stratum; setting a casing in said bore hole so as to intersect said production stratum; locating said marker; and then perforating said casing in a position correlated with said marker and determined in accordance with said known relation of said production stratum and said marker, whereby said perforating will connect the interior of said casing with said production stratum.

4. A method of producing a fluid from the earth wherein a well intersects a production stratum, a marker is established in a known relation to said production stratum independently of the location of said production stratum relative to the top of the well, and a fluid entry means is moved into the well and located in a position correlated with said marker in accordance with the known relation of said marker and said production stratum, whereby said fluid entry means will coincide with said production stratum.

5. A method of producing fluid from the earth wherein a well intersects a production stratum, comprising: establishing a marker in proximity to and at a known distance from said production stratum independently of the computed distance of said production stratum from the top of the well; moving a fluid entry means into the well and locating the same in a position coinciding with said production stratum, said locating step being accomplished by placing said fluid entry means at said known distance from said marker independently of the computed distance of said production stratum from the top of the well.

6. A method of accurately positioning a member'within a well with relation to a part of the well spaced at such distance from the top of the well that accuracy of measurements from the top of the well cannot be relied upon, comprising: establishing a marker in proximity to andat a known distance from the position desired for said member; moving said member into the well and locating the same in said desired position, by placing said member at said known distance from said marker independently of the computed distance of said desired position from the top of the well.

7. A method of accurately positioning ameniber within a well with relation to a part of the well spaced at such distance from the top of the well that accuracy of measurements from the top of the well cannot be relied upon, comprising: establishing a marker in proximity to and at a known distance from the position desired for said member; moving a marker locating means into the well to a known position relative to said marker; and then by using said known position of said marker locating means as a guide, placing said member at said known distance from said marker.

8. A method of accurately positioning a member within a well with relation to a part of the well spaced at-such distance from the top of the well that accuracy of measurements from the top of the well cannot be relied upon, comprising: establishing a radio active marker in proximity to and at a known distance from the position desired for said member; moving a marker locating means which is responsive to radiations into the well to a known position relative to said marker; and then by using said known position of said marker locating means as a guide, placing said member at said known distance from said marker.

9. A method of accurately positioning a member within a well with relation to a part of the well spaced at such distance from the top of the well that accuracy of measurements from the top of the well cannot be relied upon, comprising: establishing a marker of magnetic material in proximity to and at a known distance from the position desired forsaid member; moving a marker locating means which is responsive to said magnetic material into the well to a known position relative to said marker; and then by using said known position of said marker locating means as a guide, placing said member at said known distance from said marker.

10. A method of producing fluids from the earth, comprising: forming a'bore hole in the earth so that the same will intersect a plurality of production strata; placing a marker in proximity to each of said strata; setting a casing in the bore hole; locating said markers; and using said markers as guides, perforating said casing at selected production .strata.

11. A method of exploring a well having 8. casing which intersects a production stratum, comprising: flring a projectile through a selected part of said casing to provide communication with an adjacent stratum, said projectile being so formed that it may be located by a. locating device lowered into the well; making a test to determine if a desired fluid has entered said casing through the hole formed by said projectile; locating said projectile; and using the location of said projectile as a guide for the application of means to close said opening.

12. In means for perforating a casing in a well, the combination of: a perforator; means for moving said perforator within said casing; marker locating means connected to said perforator so as to move therewith; and means for actuating said perforator.

13. In means for perforating a casing in a well wherein a geophysical marker has been established in a known relation to a production stratum, the combination of: a perforator; means for moving said perforator within said casing; marker locating means comprising an electrometric strata logging device having a recording means outside the well and a testing element connected to said perforator so as to move therewith; and means for actuating said perforator.

14. In means for exploring a well, the combination of: electrometric means to indicate changes in and characteristics of strata in the earth; means for depositing a marker below the surface of the ground; and means for. moving the aforesaid electrometric means and depositing means in correlation in the well.

15. In means for exploring a well, the combination of: electromagnetic means to indicate changes in the characteristics of strata in the earth; a gun of a size to move in said well; a radio active projectile carried by said gun; means for firing said projectile from said gun at a desired time; and means for moving said electrometric means and said gun in correlation in said well.

16. In means for accurately positioning a member in a well in which a marker has been established, the combination of: electrometric means for locating said marker, said electrometric means comprising a sensitive element adapted to be lowered into the well to the position 0! said marker and means outside said well to indicate to an observer when said sensitive element is positioned adjacent said marker; and means for moving in said well said sensitive element and the member which is to be positioned.

17. In means for cementing an opening in a well in which a marker has been established in a known relation to said openings, the combination of: electrometric means for locating said marker, said electrometric means comprising a sensitive element adapted to be lowered into the well to the position of said marker and means outside said well to indicate to an observer when said sensitive element is positioned adjacent said marker; cement applying means; and means for moving said cement applying means and said sensitive element, in correlative position, in said well whereby said marker may be first located and said cement applying means then positioned in a desired relation to said marker.

GEORGE E. ENNIS.