US2210205A - Water intrusion location in oil wells - Google Patents

Description

Aug. 6, 1940. R. o. ELLIOTT WATER INTRUSION LOCATION IN OIL WELLS Filed March 30, 1939 11v VENTOR Rama/v0 [7. ELL/arr xwm A TTORNE Y Patented Aug. 6 1940 UNITED STATES PATENT OFFlCE WATER INTRUSION LOCATION IN OIL WELLS.

Raymond D. Elliott, Long Beach, Calif., assignor to Lane-Wells Company, Los Angeles, Calif., a corporation of Delaware Application March 30, 1939, Serial No. 265,056

' 13 Claims. (Cl. 175-183) vMy invention relates to water intrusion locawithin the well-bore taken substantially through tion in oil wells, that is, to a method and ap- 22 of Figure 1; and

paratus for locating the point at which water is Figure 3 is a diagrammatical view of a modientering oil wells so that steps may -be taken fied form of the apparatus.

to correct or stop the intrusion of water. Among The apparatus employed in my invention in- 5 the objects of my invention are: cludes a cable I preferably comprising a weight- First, to provide a method and apparatus of supporting sheath 2 and a single conductor 3. this character which may be employed while the The lower end of the cable is provided with a well is flowing, or. under any condition, either cable head 4 connected through a link 5 (prefin a flowing or non-flowing well, in which the erably covered with insulation). to a fitting 6. 10 formation pressure of the water-bearing strata The fitting 6 is screwthreaded to one end of a in question at the time of testing is greater than sleeve I of uniform diameter and having circuthe hydrostatic head within the well-bore. lation ports 8 and 9 at its upper and lower ends Second, to provide'a method and apparatus of respectively. US this character which eliminates extensive and Supported within the sleeve, on an insulated time-consuming preliminary operations forstem II, is an electrode I2, preferably centrally merly required to condition a well in order to disposed with respect to the ends of the sleeve! make a test of water intrusion; ,and electrically associated with the conductor 3 Third, to provide a method of this character of the cable. The sleeve 1 is electrically.assowherein only a small quantity of conditioning ciated with the sheath 2 of the cable.

material applied only in the zone in question Thelower end of the sleeve 1 is attached to need be introduced into the well fluid, the quana nipple l3 having a bore I 4 therein controlled tity of conditioning material being sufficiently by a suitable valve l5 having an aperture of small that it may be contained in a baileror predetermined area. The lower end of the nipple other suitable device attached to the measur- I3 is screwthreaded into a shell l6 which, in

' ing electrode and lowered therewith on an electurn, is secured to a check valve housing I! tric cable into the zone to be investigated; which carries a check valve l8 adapted to permit Fourth, to provide a method and apparatus downward flow of fluid through the shell l6, but of this character wherein only one round-trip of to prevent upward flow therethrough. The check the apparatus need be made, that is, it is merely valve housing I! is connected by a coupling I9 30 necessary to lower the electrodes and conditionto 'a trip valve housing 20 which is provided with ing material into the zone to be treated, move a bore 2| therethrough, controlled by a trip the electrode assembly through said zone only valve 22 normally tending to prevent downward a few times to obtain several records for check, flow of fluid through the bore 2I.- The trip valve 45 one against the other, then withdraw the appa- 22 is provided with a stem 23 which extends ratus from the well; through and protrudes beyond a nose piece 24 Fifth, to provide a method and apparatus of attached to the lower end of the valve housing this character wherein, if desired, several tests The Stem 23 is p v w S e latch may be run in sequence, either to investigate vmeans 5 so t t wh f r pw r y a p the same or difierent sections of the well-bor determined distance the latch means prevents 40 without reconditioning or otherwise re-treating return f f f' of the Valve 22, as shown by the well between tests; and dotted lmes m I Sixth, to provide a method of this character The Pnductor 3 c d through a which employs to an advantage certain condi able resistance 3| and milllammeter 32, to the tions heretofore existing as a detriment in the 1s bridged by a resistor 34 having an ad ustable :2 fmetilods 2 E S detectmg tap 35 connected with the sheath 2 of the cable. p0 Wa er en W m 0 an 0 A voltmeter 36 is connected across the conductor With the above and other ob ects in view; as 3 and sheath 2 preferably beyond the resistor will appear hereinafter, reference is d to the 3|. The milliammeter is preferably associated 50 l p y f i in which v i in a conventonal manner with a recording mech- F ll 1 l essentiallye dia em i View anism so as to measure variations in the curof the apparatus employed; rent flowing between the electrode l2 and sheath Figure 2 is an enlarged fragmentary longitu- I, and associated metal'parts 6 and I3. dinal sectionalview of the apparatus lowered My method of locating water intrusion is as 55 negative side of a battery 33. The battery 33 45 peratures of operation, it being borne in mind that the well'temperatures may reach as high as the boiling point of .water. The apparatus, as

'shown in Figure 1, is lowered to a point opposite the region under investigation, usually to the bottom of the well. When the apparatus is set on bottom the stem 23 is forced-upwardly, opening the valve 22 so that as the apparatus is drawn upwardly the ferric chloride, or other oxidizing agent, may drain out at a predetermined rate from the shell 16, it being noted that the check valve I8 is responsive to the slight differential pressure. Ferric chloride has a melting point at approximately 98 Fahrenheityit may,

- creasing effect is readily ascertained by change' Several therefore, be introducedas a solid and permitted to dissolve or mix with the water as it enters. After the region in question has been treated with the oxidizing agent, by reason of its dis charge into the well fluid through openings in the end plug 24, the apparatus is again lowered.

Any movement of the apparatus, of course, causes flow of fluid through the interior of the sleeve 1 around the electrode l2. The electrode [2 is connected to the negative side of the circuit; consequently there is a tendency for particles of hydrogen gas to collect on its surface, causing what is known as a polarizing effect which, as the effective surface is diminished by reason of the presence'of the hydrogen bubbles, increases the resistance of the circuit. The presence of the oxidizing agent in the well fluid, however, tends to prevent the accumulation of the hydrogen bubbles, that is, tends to depolarize the electrode l2. However, the treated region of the well is being continually diluted by the intrusion of the water to be detected. By reason of suchdilution, the oxidizing agent is less effective opposite the point of water entry, and this dein the current flowing in the circuit. runs past the area so affected by water intrusion may be made.

It is preferred to use stainless steel or other non-corroding material for the electrode l2. It

is not necessary that the fitting 6, sleeve 1 or nipple l3 be connected to the return side of the circuit; a second electrode positioned above the insulated section 5 may be used, or the cable sheath itself may sufli'ce. Still further, the return side may be the casing lining the well-bore.

The electrode I2 is preferably quite small in area; an area of approximately two square inches has been found satisfactory. Also, it ispreferred to use quite low voltages to avoid excessive decomposition of the electrolyte in the water column; voltages below 1.7 are preferred. Also, a very low current is preferably employed, 30 to 400 microamperes being found satisfactory. A comparatively small quantity of oxidizing agent is suflibient to treat a relatively long section of casing; for example, about 5 pounds of ferric chloride (solid) is suflicient to'treat 200 feet of 6 casing.

In'some instances it is not necessary to carry a quantity of electrolyte in the apparatus asso ciated with the electrode; if sodium chloride is present in the well-bore, it may be decomposed electrically to liberate a chlorine oxidizing agent suitable for the purposes of my method. An arrangement to accomplish this is shown in Figure 3. In this arrangement a large graphite negative electrode corresponding to electrode I2 is provided, separated by insulation 42 from a positive "electrode 43, both suspended from the cable I, the negative electrode 4i being connected to the conductor 3, while the positive electrode 43 is connected to the sheath 2. At the surface a circuit such as shown in Figure 1 is provided, except that there is interposed between the cable and suchcircuit a double pole, double throwswitch 44 which may be connected to a direct current source 45 of greater potential. In operation, the electrode assembly is moved through the region to be investigated while the switch 44 is connected to the source of high direct current, so that the electrolyte, such as salt water, within the well-bore, is decomposed and an oxidizing agent, namely, free chlorine, is released. The switch 44 is then connected to the measuring circuit and while the chlorine is active the test is made. Of course, in such event there will be a drift, or gradual over-all decrease in its effectiveness as the free chlorine re-combines, nevertheless superposed on such change will be that change due to the inflow of water.

In other words, the oxidizing agent may be either carried down with the'electrodes or generated in situ; in either case the oxidizing agent is established in the fluid just prior to making the test. By reason of the fact that there is always present in the oil well material with which the oxidizing agent will combine, a time interval varying from a few minutes to a few hours,.depending on the oxidizing agent employed, may be sufficient for the oxidizing agent to combine and restore conditions as they existed before the test. Consequently, repeated tests may be made without special preparation between tests.

Various changes and alternate arrangements may be made within the scope of the appended claims, iri which it is my intention to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim: 1. A method of detecting the point of intrusion of a fluid into a well-bore, characterized by: providing an oxidizing agent in the'well fluids throughout the region to be tested; moving an i electrode through said region while applying direct current thereto; and measuring polarization effects on said electrode as said oxidizing agent becomes diluted with incoming fluids.

2. A method of detecting the point of entry into a well, of liquids having electrolytic properties, characterized by: providing throughout the region to be tested, an oxidizing agent in the liquids contained in the well; moving an electrode through said region while applying a negative potential thereto; and measuring the changes in polarization at said electrode as the oxidizing agent becomes diluted with incoming liquid.

3. A method of detecting the point of entry into a flowing well, of liquids having electrolytic properties, characterized by: establishing a distribution of an oxidizing agent throughout the region to be tested; immediately, during the active period of said oxidizing agent, moving an electrode through said region while applying a negative potential thereto; and measuring the polarization effect on said electrode as changed by dilution of said oxidizing agent by the liquids entering the well.

4. A method of detecting the point of entry of a fluid into a well wherein the liquid within the well exhibits electrolytic properties, characterized by: conditioning the well liquid throughout the region to be tested with an oxidizing agent capable of inhibiting polarization of an electrode subject to a negative potential; moving such electrode through said region while subjected to a negative potential; and measuring changes in an electrical circuit incorporating said electrode as induced by changes in polarization of said electrode due to dilution of the oxidizing agent by incoming liquids.

5. A method, as set forth in claim 4, wherein the oxidizing agent is lowered simultaneously with said electrode to the region to be tested, distributed throughout said region, and said electrode immediately employed while said oxidizing agent is active.

6. A method, as set forth in claim 4, wherein said oxidizing agent is generated by electrolysis of the well fluid caused by application of substantial direct current thereto, and said electrode is employed immediately following such application of direct current and during the active period of said oxidizing agent.

'7. A method of detecting water intrusion in an oil well, characterized by: conditioning the region to be investigated with an oxidizing agent; moving an electrode subject to a negative potential through said region during the active period of said oxidizing agent with such potential below 1.7 volts; and measuring changes in the circuit associated with said electrode caused by changes in polarization of said electrode as said oxidizing agent is diluted by incoming water.

8. A method, as set forth in claim 7, wherein said region is conditioned by an oxidizing chemical lowered into said region simultaneously with said electrode and distributed therein immediately prior to conducting the test.

9. A method, as set forth in claim '7, wherein the electrolyte within the well-bore is subjected to active electrolysis to generate an oxidizing agent in said region immediately prior to conducting said test. V

10'. An apparatus for locating the point of water entry into a well-bore, comprising: a distributing bailer and an electrode suspended from a cable; means for operating said bailer to distribute its contents along a predetermined region of said well-bore; an electrical circuit for said electrode to establish a negative potential; and means in said circuit for measuring variations in said circuit caused by changes in polarization of said electrode.

11. An apparatus for locating the point of water entry into a well-bore, comprising: an electrode assembly; a cable for lowering said assembly into a well; a charging circuit associated with said electrode assembly adapted to generate by electrolysis an oxidizing agent from the electrolyte within the well-bore as said electrode assembly is moved along the region to be investigated; and a measuring circuit adapted to be employed immediately following generation, of said oxidizing agent, for detecting changes in the polarization effect on said electrode.

12. A method of detecting the point of entry into a well, of liquids having electrolytic properties, characterized by: introducing into the region to be tested an initially solid oxidizing agent having a melting point below the temperature of said region; distributing said agent through said region as it melts; and'thereafter during the active period of said oxidizing agent, moving an electrode through said region while subjected to a negative potential; and measuring the polarizing efiect on said electrode as incoming liquids dilute said oxidizing agent.

'13. A method of detecting the point of entry into a well, of liquids having electrolytic properties, characterized by: introducing into the region to be tested a solid oxidizing agent soluble in the fluids present in said region; distributing said agent through said region as it dissolves; and thereafter during the active period of said oxidizing agent, moving an electrode through said region while subjected to a negative potential; and measuring the polarizing effect on said electrode as incoming liquids dilute said oxidizing agent.

RAYMOND D. ELLIOTT.

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