US1786196A - Method and apparatus for determining the location of water strata in wells - Google Patents

Description

G. H. ENNIS Dec. 23, 1930.

METHOD AND APPARATUS FOR DETERMINING THE LOCATION OF WATER STRATA IN WELLS 2 Sheets-Sheet l Original Filed Jan. 9, 1926 NOR/VIAL FLUID LEVEL CoA/NA rf o/L SAND wArfR smv@-P Dec. 23, 1930. G. H. ENNls 1,786,195

METHOD AND APPARATUS FOR DETERMINING THE LOCATION OF WATER STRATA IN WELLS Original Filed Jan. 9, 1926 2 Sheets-Sheet 2 CON/YA Y! I N VEN TO R. G50/Q65 H. Mv/s A TTORNE Y.

Patented' Dec. z3, 1930 GEORGE H. ENNIS, 0F LONG ,PATENT oFFlcE d BEACH, CALIFRNIA, .ASSNOR 0I' ONE-HALF T0 ROBERT V. FUNK, OF ANAHEIM, CALIFORNIA x nnTnon AND APPARATUS non DTEBNINING THE LOCATION or WATER sTnATA rrry WELLS Application led January 9, 1926, Serial No. 80,160. Renewed December 28, 1929.

This invention relates to method and apparatus for determining. the location of water strata in wells.

The general object of the invention is to provide an improved method and apparatus whereby the location of the strata of water in the well can be accurately determined.

The method in common use for locating 'water strata in oil wells includes washing the well by inserting a tubing in the well and passing fresh water downward through the tubing into the lower portion of the Well. When the overflow from the top of the well-is found to be fresh, the washing is stopped and the tubing withdrawn. A pair of spaced electrodes is then lowered to the bottom of the well and raised again, a uniform potential of electric current being imposed .upon these electrodes. During the lowering and raising of the electrodes, the resistance of the water to the passage of the current between the electrodes is recorded by a Wheatstone bridge. If this resistance shows a marked 'variation at any depth in the well, it is known that connate water is still present in the well at this depth and after the electrodes have been withdrawn, the tubing must be again lowered to a point near the bottom of the well and the y washing continued.

This washingl must be repeatedV until the resistance of the water isfound practically uniform at all points in the well. The level of liquid in the well is then lowered by bailing until somewhat below normal level. This ter.

causes connate water to iow into the fresh water in the well from the water strata which communicate with the well. Connate water is almost invariably saline and therefore a better electrical conductor than the fresh wa- The electro-des are now lowered through the well and the .resistance to flow of current between the electrodes recorded at various depths in the well. Wherever the connate water is entering the well, the resistance will decrease greatly and this will be indicated on the record graph by a distinct peak.

Many difficulties are met with in carrying out the above `outlined method, not the least of which ,is the necessity of repeatedlylowel-l ing and raising a string of tubing practically throughout the length of the well.

It is an object of my invention to provide a method for the location of water strata in oil wellsin which the lowering of tubing into the well for displacing the contents 'of the well with .another liquid is unnecessary.

In thus displacing the liquid in the well by another liquid, itis necessary that the lower end of the tubing be disposed Several hundred feet above the bottom of the well in order to prevent the tubin being sanded up or embedded in sand p aced in circulation by the force of the jet of liquid leaving the tube. Thus, the liquid in the well below the lower end of the tube is not materially affected by the washing process so that any resistance recorded when the electrodes are in this extreme bottom 'portion of the well is practically meaningless as far as indicating the location of water strata is concerned.

It is another object of my invention to provide a method for the location of water strata in oil wells in which water strata may be accuratel located in the extreme lower part of a well 1n the same operation in which water strata opening into the remainder of the well are located.

In different -wells the salinity of the connate waters varies in strength so that when the variation in resistances between one liquid and the connate waters is relied upon to record the 'locations of water strata, this y record often wrongly indicates the relative iiows from lvarious Strata.

It is a still further object of my invention to provide a method for the location of water strata in oil wells in which the degree of salinity of the connate waters is practically` a negligible factor in determining the character of the record. Y

In the old process referred to above, practically the entire well must be treated or at least all of the well forfa given distance down from the upper end thereof.

It is an object of my invention to provide a method for the location of water strata in oil wells in which a given zone may be tested exclusive of the remainder of the well.

Yet another object of my invention is to provide a novel apparatus for carrying out the method of my invention.

Another object of the invention is to provide an improved construction of elements for use with water locating'apparatus.

A further object of the invention is to provide a novel means for recording variations in potential difference between elements which are suspended at varying depths in wells.

Other objects of the invention will be apparent from the following description taken in connection with the accompanying draw in s, wherein:

ig. 1 is a diagrammatic section of an oil well showing a chemical cartridge being lowered therein;

Fig. 2 is a view similar to Fig. 1 showing a bailer in operation;

Fig. 3 is a similar view showing elements being lowered therein;

Fig. 4 is an elevation 'of the element or plate assembly;

Fig. 5 is a view similar to Fig. 4 with the top portion in section;

Fig. 6 is a cross section taken on line 6-6 of Fig. 4;

Fig. 7 is a diagrammatic view showing a wiring diagram and associate parts, and

Fig. 8 is a view of a chart made with my device.

In the following description I will describe my method and apparatus as used in connection with oil wells where it is of particular use in determining the 'location ofy water bearing strata. In order that an oil well may produce a good grade of crude oil, it is necessary that the water be cemented oli'. To do this, it is first necessary that the water strata be located before the water may be excluded from the well.

Referring to the drawing by reference characters, I have shown an oil well generally at 10. I This wellis shown as provided with a casing 11 which may be suitably anchored in the casing head 12. Another casing is shown at 14 and this case supports, at its lower end, a string of perforated casings 15.

The normal fluidlevel is indicated at 16 while the connate oil sands are indicated at 17. A gas sand is shown at 18 and a connate water strata is indicated at 19. The

roblemwhich my invention solves is the ocating of this last mentioned strat-um 19 which bears the objectionable water.

In carrying out m' invention I may arrange a frame 20 adjacent the casing head 12. Upon this frame I mount a cable drum 21. which may be operated in any desired manner. A

, In the preferred practice of my invention I employ a cartridge-like casing 24, the sides of which are made of reticulated mesh. This casing is adaptedto be lowered in the Well.

It' is first lled with a suitable material, which when dissolved in the fluid in the Well, will form an electrolyte. I have found reel (not shown) and by means of the bailer I lower the normal fluid level a desired amount to cause connate oil and connate water to enter the well.

My testing apparatus also includes an elemental device 25. This elemental device is suspended by a cable 26 which includes two leads 27 and 28. The cable 26 has one end fastened to the cable drum 21 previously described and has the other end fastened to the elemental device 25.

This elemental device includes a top portion 29 having a bail 30 thereon to which the cable 26 is secured by means of a clamp 31. This clamp 31 may engage a compression member 32 although the specific details of securing the cable to the elemental device may vary.

The elemental device also includes a bottom portion 33 on which a weight 34 is arranged. The top portion 29 and the bottom portion` 33 are provided with insulating members 35 and through these insulated members a central insulating rod 36 extends.

, About the rod 36 I arrange, preferably in a helicalform, a pair of spaced elements 37 and 38. One of the elements, for instance 37, may be made of zinc While the other element 38 may be made of copper. In lieu of these elements others may be used so long as they will possess the necessary characteristics. The elements are shown as connected at their upper ends to the leads 27 and 28 as shown at 39 and 40 in Fig. 5.

The elements are spaced apart suitable distances and are insulated from each other so that variations in potential difference will exist between the two elements when they are lowered in the electrolyte by unrolling the cable 26. f l

The elemental member 25 is provided with l guard members 41 to prevent injury to the elements and with vanes 42 at the top and bottom. These vanes 42. are arranged in a direction reverse to the direction of the elements 37 and 38 so that the members will counteract each other, thus preventing rotation of the elemental member while it is being lowered in the well. The curvature of the elements causes them to keep clean in use.

The cable 26 passes over a pair of idlers 44 and over a drum 45 so that as the cable is unwound and wound when it is lowered in the well and lifted in the well, the drum will be turned by the friction of the cable.

This drum 45 is connected by means of'aflexible shaft 46 with a shaft 47 on which a. pair of beveled gears 48 and 49 are connected for sliding action. Eithei` one of these gears is adapted to be thrown into engagement with a beveled gear 50 by actuating a pivoted rocking arm 51. The gear 50 is mounted on the shaft 51 of a paper supporting drum 52. From the foregoing description it will be apparent that continuous movement of the paper 52 in the same direction may be effected by shifting the lever 51 when the direction of the movement of the cable 26 is changed.

The leads 27 and 28 in the cable 26 pass from the drum 21 through contacts thereon to wires shown in a wiring diagram in Fig. 7. The lead 27 is in circuit with a terminal 51b of a pole changing, four Way switch 51c as shown in Fig. 7.

The lead 28 is in circuit with a contact 52a of the pole changing switch 51, previously mentioned. The other two terminals of the switch are shown at 58 and 54 in Fig. 7. The terminal 54 is connected by means of a lead 55 with a lead 56 which is in turn connected to a terminal on a recording voltmeter 57. This voltmeter has an indicating pointer or indi` cator arm 58 which is provided with suitable marking material thereon so that it will mark on the paper arranged on the drum 52 previously described. p

The terminal 58 is connected by a lead 60 with a rheostat 61, The rheostat is connected to a battery 62. This battery 62 is connected to another rheostat 63 which is also connected to the lead 56. The rheostat is connected by a lead 64 to a battery 65 whence a lead 66 passes to the other terminal 69 of the voltmeter.

The lead 68 is connected with the lead 60 by means of a lead 70 and the construction y of parts is such that by shiftingv the rheostat controls the ,voltage produced by the batteries may be made to correspond to the potential differences across the elements of the elemental members 25 so that the indicator needle 58 may be made to read zero. l

A sheet of paper adapted foruse with my invention is shown at 75. This paper is ruled with transverse lines 76 to indicate depth. The paper is also ruled with longitudlnal lines as at 7 7 to provide an arbitrary marking for indicating variations'in potential differ' ence. The paper may be mounted on the drum 52 in any desired manner.

In using my apparatus the fluid level is i determined by lowering the elemental member 25 in the well. The point at which the elements are immersed in the fluid will be indicated by the needle 58. The rheostat controls are then moved so that the E. M. F. of the batteries 62 and 65 and the elemental well.

member 25 are balanced thereby causing the needle 58 to assume a position at the zero mark as shown at 80 in Fig.' 8.-

The drum 21 is then operated and the elemental memberlowered to the bottom of the The member 51 is then reversed and the cable is withdrawn. The operation of the gears causes the paper roll to revolve in the same direction so that a graph is made as the elements go up and down. If the well has been properly washed the needle 58 will assume a position at zero or nearly so, which would show the fluid to be substantially the same throughout the depth of the well.

The next step is to lower the cartridge-like casing 24 filled with ammonium chloride or other suitable material into the well thereby making an electrolyte. The elemental member 25 is then again lowered into the well. As soon as the elements are immersed in the electrolyte, the batteries and elements are again balanced and then lowered to the bottom and returned as before. If the charge of electrolyte has been complete the needle 58 will assume a position at zero or nearly so, during this operation. If charge is not complete a curve on the chart will show the exact depth that the electrolyte is weak. The cartridge casing 24 is then lowered to the zone or zones indicated as weak on the chart, and raised and lowered in that zone until the fluid is changed. The elements are then again lowered, and this process is repeated until the reading on the chart is zero or nearly so. v

Next the electrolyteis lowered below the fluid level by bailing. The amount should be just enough yto start the'formation fluids entering the well. Another run of the elemental member 25 is then made. The fluid entering the well from the various strata will be indicated by the change in the electrolyte opposite the oil zones and formations containing water. This will throw the instrument out of balance causing the needle 58 to register a curve 81 on the chart to the right or left of zero depending onthe chemical action of the electrolyte on the elements. After the elemental member has been lowered some distance, it may enter the water bearing areas so that the varying potential we-ll and the member 51 has bcn reversed, the

next graph will make a curve 84 which will correspond approximately with the curve 82. Several subsequent runs of the elements will be made, the fluid level being lowered each time by hailing prior to each run. Calcula tions based. on the peak of the curves 82 and 84 will then indicate the exact point 4of en- Cil trance of the water so that it can be cemented ofi".

If the electrolyte becomes diffused with salt Water more chemical can be lowered in the well to strengthen the electrolyte.

The renewal of the electrolytic solution is thus seen to be a very simple and inexpensive operation quickly accomplished'by the lowering of the chemical cartridge 24 in'to the area where the electrolyte has been diluted, and raising and lowering this cartridge until the electrolytic solution is restored. In order to check the uniformity of the electrolytic solution at any time, the cartridge 24 need merely be withdrawn from the well on its cable and the elemental device 25 lowered for a test record. This requires only a small fraction of the time required in the old process for lowering and raising a tube from the bottom of a well several thousand feet deep in the washing of the well. In the old process thirty-six hours is usually consumed in merely completing the washing step, while. in the extensive use of my process, I have uniformly completed the entire survey of the well in from twelve to twenty-four hours.

It is desired to point out that the submerging of the copper and zinc Ielectrodes 37 and 38 in the solution of ammonia chloride forms a voltaic or galvanic cell which chemically sets up a difference of potential between these electrodes. The variation in this potential is the basis of the testing of the strength of the solution and this is particularly desirable as it is practically independent of the saline content of the well water.

Having thus described my invention, I claim: c

A 1. The method of locating water bearing strata in a well, comprising: dissolving an ionizable chemical in the water in said well; lowering plates into said solution of a character to form a voltaic cell when disposed in said solution; moving said plates through said solution while held in spaced relation;

and recording the potential difference between said plates during said movement.

2. The method of locating water bearing strata in a well, comprising: dissolving an ionizable'chemical in the water in said well having different electro-chemical qualities from that possessed by a principal solute already in said water to form a uniform solution of said chemical in a given zone of said well lowering the pressure of said solution in said well; and testing the liquid at various points in said zone to determine the degree to which said electro-chemical qualities are present in said liquid.

3. The method of locating water bearing strata in a well, comprising: lowering a relatively concentrated ionizable chemical into a well to form a practically uniform solution in the water already in said well; reducing the hydrostatic head of said solution on said well; allowing the well to rell substantially to its former level by the natural ingress of lwater; and electrochemically testing said points -to determine where y Water flowing into the 'strata in a well, comprising: lowering a relatively concentrated ionizable chemicalinto a column of water in a well; mixing said chemical with said water in al zone of said column to form a relatively uniform electrolytic solution of said chemical in said zone; reducing the pressure of said solution on said well; and electrochemically testing said solution at various pointsfto determine where it has been diluted by connate fluid flowing into the well.

5. The method of locating water bearing strata in a well, comprising: lowering an ionizable chemical into a column of water in a well; mixing said chemical with the water in a zone of said column to form a practically uniform solution of said chemical in said zone; lowering plates into said solution of a character to form a voltaic cell when disposed in said solution; moving said plates through said solution while held in spaced relation; and recording the potential difference between said plates during said movement.

6. In an apparatus of the class described: a pair of dissimilar electrode elements adapted to be freely moved within a well; a pair of leads connected to said elements and adapted to extend to the top of a well; an electro potential producing means capable of functioning at the top of said well to produce a variable potential dillerence which may be made to balance the potential difference generated between the said dissimilar metallic elements; and an indicating means electrically connected to said leads and said potential producing means and capable of registering as a function of the dilerence in potential existing between said leads and said potential producing means.

7. A method of testing a well to determine the location of any strata at which a fluid enters said well, said method including the steps of: providing said well with a body of electrolyte; lowering electrodes into said electrolyte, of a character to form a voltaic cell when disposed in said electrolyte; moving said electrodes through said electrolyte while held in -spaced relation; and measuring the potential dierence between saidelectrodes.

8. A method of testing a well to determine the location of any strata at which a fluid enters said well, said method including the steps of: providing said'well with a-body of electrolyte; forming a voltaic cell in said electrolyte; moving said voltaic cell in said electrolyte; and measuring the voltage produced by said voltaic cell.

9. A method of testing a well to determine the location of any strata at which a fluid enters the Well, said method including the steps of: providing said Well with a body of electrolyte; causing iuid to How into said Well from the surrounding strata, said fluid changing the strength of said electrolyte at the point of entrance of said fluid; moving a pair of space electrodes through said electrolyte, said electrodes being of a character to cooperate With adjacent electrolyte to form a voltaic cell; and measuring the potential difference between said electrodes as they move through said electrolyte.

10. A method of testing a Well to determine the location of any strata at which a fluid enters the Well, said method including the steps of: providing said Well With a body of electrolyte; reducing the hydrostatic pressure in said Well in order to reduce the pressure against the strata surrounding said Well; moving a pair of space electrodes through said electrolyte, said electrodes being of a character to cooperate with adjacent elec-i trolyte to form a voltaic cell; and electrochemically testing said electrolyte at various points to determine where it has been diluted,

by fluid entering said well.

In testimony whereof, I hereunto aiiix my signature.

GEORGE H. ENNIS.

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