US1555802A - Apparatus for locating water-bearing strata in bore holes of flowing wells - Google Patents

Description

Sept. 29, 1925.

F. W. HUBER APPARATUS FOR LOCATING WATER BEARING STRATA IN BORE HOLES 0F FLOWING WELLS Filed Sept. 2, 1924 [N VEN TOR. FreaPr/Z'K H4 Haber A TTORNE Y.

Patented Sept. 29, 1925.

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APPARATUS FOR LOGATING WATER-BEARING STBATA. IN BORE HOLES OF FLOWING To all whom it may camera:

Be it known that I, FREDERICK W. HUBER,-

a citizen of the United States, residin at Riverside, in the county of Riverside, tate of California, have invented a new and useful Apparatus for Locatin Water-Bearm Strata in Bore Holes of F owing Wells, 0 which the following is a specification.

This invention relates to a method for 10- eating water bearing strata in bore holes n oil or gas bearing formations and the mam object of the invention is to provide a means and method whereby the location of such water bearing strata may be positively determined without interrupting the operation of the well.

In the operation of 011 wells it often occurs that after the oil has been flowing for some time either under natural pressure or with the assistance of pumping, there is a tendency for water (so-called ed e water) to enter the well from water bearing strata adjac ent to the bore hole, this tendency increasing as the gas pressure in the well diminishes and often result-ing eventually in the abandonment of the well. In some cases, also, it is not possibile to start production of oil, because of flow of water into the well.

My invention provides for determining the location of water bearing strata while the well is in operation or before it starts into operation so that steps can be taken promptly to cement out such strata so as to exclude water from entering the Well. from such strata and to start or maintain the well in productive operation.

My invention provides for introduction within the bore hole of a flowing well a means for producing at any one of the desired levels in the well a zone of fresh water or water of relatively different salinity and further introducing into the well a means for measuring the salinity of the liquid adjacent to such fresh water zone in such manner that any variation of such salinity due to proximity-of the strata bearing salt water will result in a corresponding variation in electrical measurement thereby determining the location of the water bearing stratum. The salinity of the liquid is referably measured by introducing electro e means, connected to a source of (preferably alternating) current of substantially uniform Application filed September 2, 1924. Serial No. 735,330.

voltage into the well in such manner that such electrode means are exposed to the liquid inthe well and measurin the resist ance of the liquid so exposed to t e electrode means in any suitable manner.

The accompanying drawings illustrate the manner in which my invention may be carried out and referring thereto:

Fig. 1 1s a diagrammatic vertical section of-a well with the measuring appliances in place therein.

Fig. 2 is a section of the exploration tube and a side elevation of the resistance meas uring appliance with the electrical circuits therefor shown diagrammatically.

Flg. 3 is a Vertical section of the electrodes.

Referring to Fig. 1 a well casing is shown at 1, said casing being assumed to constitute the oil string which extends down .into the 011 sands and which is perforated in the usual manner as indicated at 2 for inflow of oil. 3 indicates the water string which is assumed to be cemented in the usual manner so as to shut off all water strata above the oil sands, and casing 1 is further provided at its upper end with the usual means for carrying off the oil for example through delivv ery pipe 4.

The measuring means used according to my.1nvent1on comprises a conductor cable 5 or self supporting cable means which is providedwith electrodes 6 and7 at its lower end and is flexibly connected at its upper end to a suitable measuring circuit as hereinafter described. This conductor cable 5 carrying the electrode, is mounted within a vertical exploration tube 8 which is formed as a string of suitable tube sections in the usual manner in the art so as to enable it to reach from the top of the well down to the level of the oil sands. This tube may be supported by an suitable elevator means such as indicate at 10 so as to be raised and lowered at will and if necessary is passed through a stufling box 13 in the casing head 14 in such manner that the lower endof the tube member may be raised and lowered throughout the height represented by the perforated portion of the oil string. The cable 5 is also mounted for vertical movement within the pipe 8, for example by means of a sleeve 16 mounted 45. transformer whose primary winding 15 is .water of low saline concentration.

on said cable and sliding through a stufiing box 17 on the head 18 at the upper end of said pipe 8. Said head 18 may e provided with a flexible pipe connection 20 leading to a source of supply of fresh water or Electrodes indicated at 6 and? may be mounted in any suitable manner for example within a cylinder 9 which may be of insulat ng material, the electrodes in any case belng insulated from one another and being mounted a definite distance apart and the cylinder being open and preferably being open at both ends so as to allow free access of liquid to said electrodes. The said electrodes 6 and 7 are connected respectively to wires or conductors 22 and 23 within the said cable 5. The conductors 22 and 23 are preferably formed as steel wires or cables,

for the sake of strength and in that case are self-supporting, being either embedded in insulation to form a single conductor cable or being separately insulated and extending side by side to form two conductor cables.

Any suitable circuit means may be provided for applying the electric current or potential to the wires leading to the electrodes so as to measure the resistance of the medium presented between the electrodes, for example, as shown in Fig. 2, said electric measuring means may comprise a Wheatstone bridge 21 of usual construction, which is connected to a source of current or electric potential described below and to the circuit wires 22 and 23. It is essential to the present invention that alternating current should be used in measuring the electrical resistance so as to avoid errors which would result from polarization in case direct current were used, and it is also important that no ground connections should be present, and in order to satisfy these requirements I prefer to use as a source of current a connected to any suitable alternating current supply circuit, either single phase or polyphase, and whose secondary winding 24 is connected by wires 25 and 26 to opposite terminals of the Wheatstone bridge 21. The intermediate terminals of the Wheatstone bridge are connected in, the usual manner to a null point indicator 27 which is of a type adapted for operation by alternating current. Said null point indicator may be provided with energizing circuit connections 28 and 29, including resistance or lamp 30, for the field magnet coil thereof, so as to apply say 110 volts to such coil, to produce a magnetic field which operates upon an armature coil connected by circuit wires 31 and 32 to the intermediate terminals of the Wheatstone bridge in the usual manner of such alternating current measuring means. Any other electrical measuring means, responsive to alternating current may, however, be used. The transformer used may be of the iron core type, transforming for example from 110 to 6 volts, the latter voltage bein applied to the wires leading to the electro e means. By maintaining only about 6 volts in the lines leading to the electrodes I ensure operation of the system even when the cable insulation has become damaged by oil or otherwise as long as there-is no actual short circuit.

In order that the electrode means shall operate effectively under the conditions existing in the column of liquid in the test operation as hereinafter set forth it is necessary that the surface of the electrodes which are in contact with the liquid not be wetted by oil but only by water and saline solutions. For this purpose I have found it desirable to coat the surface of the metal body or conductors forming the electrodes with a gelatinous substance and I have found that either gelatinous silica or agar may be used advantageously for this purpose. The gelatinous silica is however only applicable to latinum or gold electrodes or to their aci resisting alloys. To coat such an electrode I allow water glass of about 1.15 sp. gr. to harden in a thin film upon the electrode and then immerse it in a-very dilute solution of mineral acid, which in the course of a few hours will form a gelatinous coating of silicic acid. This is then washed free of electrolytes and kept in a water saturated atmosphere until ready for use.

lVith the baser metals such as nickel which I prefer to use in actual field work) I simply coat the cleaned electrode surface with a thin film of agar dissolved (dispersed) in hot distilled water, by dipping the electrode in the agar infusion and allowing to set, repeating the dipping and setting until a uniform and thin film is obtained over the entire electrode surface. The elec trode after the agar has set (forming a stiffjelly-like mass), is kept in water until wanted for use. It is also of advantage to first cover the cleaned electrode with a fine cambric cloth and then saturate this cloth with hot agar infusing and building up on this covering a fine glaze of set agar. It is also of advantage, for particularly severe usage, to harden the agar by a hardening agent such as formaldehyde or alum. But this is generally not necessary.

The operation of the invention is as follows:

Assuming that a flowing oil well has been in producing operation and that the presence of water with the oil produced indicates intrusion of water into the well, the location of the water bearing stratum or strata is determined by inserting the measuring device above described into the oil well and operating it in the following manner. The

exploration tube 8 havin been brought to osition, for example wit its lower end adacent the bottom of the oil strin fresh water is forced down through sai pipe so that said pipe and the lower portion of the liquid column in the well as far as possible.

I also prefer to maintain a hydrostatic pressure inthe water su ply pipe 8 sufficient to just balance the fluid pressure in the well, so as to provide substantially a static column of li uid in the well and permit the diffusion of sa t from surrounding water sands to take place even while no water is flowing from the sand. If at this time there is present a water bearing stratum adjacent the perforated portion of the oil string and adjacent this fresh water column there will be diffusion of salt from such water stratum into the body of fresh water in said column directly opposite such water stratum, resulting in a zone of relatively high saline concentration adjacent the stratum bearing salt water. The said water column may then be explored by lowering the pipe 8 to different positions so that the lower end of said-pipe is presented, at different levels in said column and after each of said lowering operations the measurement of saline concentration at or adjacent to the lower end of the pipe is made by means of the electrical devices above described, the cable 5 being assumed to be in position to cause the electrodes 6 and 7 to be exposed tothe liquid directly below the lower end of the pipe 8, and the resistance of the liquid between said electrodes being then measured b operation of the Wheatstone bridge in we] known manner or by any other suitable de-. vice for measuring electrical resistance. While the pipe 8 is being brought to position or is being lowered to the bottom of the well the carrier member 9 for the electrodes 6 and 7 may be withdrawn within said pipe (by raising sleeve 16 and cable 5) soas to be protected and said carrier member may be lowered below the lower end of the pipe only when measurement is to be made. In some cases I prefer to momentarily relieve the hydrostatic pressure on the water supply tu e 8 just prior to or simultaneously wit each conductivity measurement so as to cause the liquid in the well adjacent the lower portion of such tube to be forced upwardly within the same 'a short distance and ensure that the electrodes are surrounded by such liquid "diffusion of salt into the zone a rather than by fresh water from the water supply tube. B making a series of measurements at di erent levels throughout the range of vertical hei hts represented by the per orated portion 0 the oil string, and plotting the resistance measurements so obtained at various de ths the depth of any stratum through whic sa t water is penetrating the well will be indicated by a corres lplondmg low point in the resistance curve. e position of the water bearing stratum or strata having been determined in this manner the proper steps can be taken to'seal or cement off such water bearing stratum from-the well so as to enable the well to continue in operation in the production of oil.

Alternatively to the above described method of operation my invention may be carried out as follows: The pipe 8 having been lowered to near the bottom of the oil strin suflicient fresh water is assed throng said pipe to displace the oiFand salt water from only the lower portion of the oil string adjacent the lower end of ipe 8, and a resistance reading is then ta en as above ,described, the electrodes 6 and 7 being lowered slightly below the pipe 8 for that purpose, andthe column of liquid being preferabl preserved in a static condition during sue measurement, by shutting off the flow of oil from the well and balancing the pressure by the hydrostatic head in the water supply ipe as above described. In some cases the ydrostatic pressure in the tube 8v may be momentarily relieved at the time of making a conductivity measurement, for the purpose above described. The pi 8 is then ralsed a suitable distance and another reading taken and this operation of successive elevation of the pipe and resistance reading being continued until the lower end of the pipe 8 reaches the upper limit ofthe perforated portion of theoil string. In this case, as before, the presence of any water bearing stratum will be indicated by an increase in conductivity or decrease in resistance of the liquid opposite such stratum by reason of jacent such stratum. This method of operation last described however has the advantage that the.

measurement is made immediately after the introduction of fresh water at the measured part of the liquid columin so that more uniform as well as more accurate results are obtained in some cases. In some cases, when.

the water entering the borefi 'hole from the water stratum has relativelylow salinity, it will be desirable to introduce into the well (instead of fresh water) water of relatively high salinity, thereading for a zone opposite such a water stratum thus indicatm relatively high resistance, and in gener my invention provides for establishing in the bore hole a ,water column of different saline concentration from that of the water in the water bearing stratum to located, and then determining the location in such a water column of any zone difl'ering in salmity from the normal salinity of such water column.-

The novel electrode described herein is claimed in a copending case 756,156, filed December 15,1924.

What I claim is:

1. In combination with an oil well a ipe independent of the oil well casin exten ing into said well and provided wit means for passing water therethrough into the well, means for raising and lowering said ipe insulated conductor means exten ing through said ipe and provided with electrodes adapted to be ex osed to the liquid in the well, and electrica circuit means connected to said conductor means and provided with means for measurin the resistance of the liquid between said e ectrodes.

2. An apparatus as set forth in claim 1 in i which said insulated conductor means is movably mounted in a vertically movable pipe through which it extends to permit of the electrode means being withdrawn within or projected below said pipe.

3. An a phance for measuring the resistivity of the liquid at difi'erent levels in a well,,comprisin' a vertically movable pipe, independent of t e well casm such movable pipe bein provided wit means for forcing water herethrou h, insulated conductor means extending t gh said pi and provided with electrodes adapted to b: exposed to the liquid in the well, and electrical circuit means connected to said conductor means and provided with means for measurin the resistance of the liquid between sai electrodes.

4. A. combination as set forth in claim 3 in which said insulated conductor means is movably mounted in the pipe throu h which it extends, to permit of the electr e means being withdrawn within or projected below said pipe.

In testimony whereof I have hereunto subscribed my name this 21st day of August FREDERICK W. HUBER.

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