US2273215A

US2273215A - Well surveying method and apparatus

Info

Publication number: US2273215A
Application number: US331039A
Authority: US
Inventors: Neufeld Jacob
Original assignee: Well Surveys Inc
Current assignee: Well Surveys Inc
Priority date: 1940-04-22
Filing date: 1940-04-22
Publication date: 1942-02-17
Anticipated expiration: 1959-02-17

Description

Feb. 17, 1942. J, NEUFELD WELL SURVEYING METHOD AND APPARATUS Filed April 22, 1940 Patented Feb. 17, 1942 WELL SURVEYING METHOD AND APPARATUS Jacob Neufeld, Tulsa, Okla., assignor to Well Surveys, Incorporated, Tulsa, Okla., a corporation of Delaware Application April 22, 1940, Serial No. 331,039

7 Claims.

This invention relates to geophysical prospecting and more particularly to a method of determining the point of entry intoa well bore and the nature of connate fluids from formations which lie adjacent a well bore.

It has already been suggested that data of this type be obtained by taking a-series of resistivity versus depth parameters of the fluid in the well bore, and reducing the hydrostatic pressure between the taking of parameters to cause more of the fluid under investigation to enter between the taking of parameters. United States Patents 2,184,338, granted December 26, 1939, to George H. Ennis, and 1,555,800 and 1,555,801, granted September 29, 1925, to Frederick'QW. Huber, and British Patent 452,076, accepted August 17, 1936, describe processes of this kind.

These methods are satisfactory in many instances, but often it is desirable to distinguish between the entering fluid and the fluid already in the well or entering from some other point, on different basis than resistivity, because there is not suiiicient difference in resistivity to permit the necessary distinctions to be made. Also, occasionally, upon a reduction of the hydrostatic pressure fluid will come out of a formation behinda casing wall, pass up or down the wall and eventually find an opening into the casing. It is desirable, if possible, not only to find the opening but also the formation that is the source of the fluid.

The present invention has for its primary object the accomplishment of both of these things. By its use distinction can often be made between fluids of the same resistivity and the formation from which the fluid originated can often be located even though the fluid passes up or down behind the casing before entering it.

Briefly, this invention comprises taking a series of radioactivity versus depth parameters, and reducing the hydrostatic pressure between the. taking of parameters. Such a process distinguishes between fluids on the basis of their radioactivity and will detect the fluids even though they are separated from the measurin instrument by a steel casing'wall.

For the purpose of taking the radioactivity parameters any known type of device that will measure radioactivity in a well bore and correlate the measurements with indications of depth, may be used. It is preferred to use a John C. Bender; in United States Patent 2,133,- 776, granted October 18, 1939, or those shown in application Serial Number 239,781, filed by Robert E. Fearon, on November 10, 1938; application Serial Number 323,239, filed by this inventor on March 9, 1940; application Serial Number 325,880, filed by Robert E. Fearon on March 25, 1940; 323,981, filed by Robert E. Fearon on March 14, 1940; application Serial Number 324,687, filed March 18, 1940, by Jacob Neufeld; application Serial Number 326,510, filed March 28, 1940, by Robert E. Fearon, may be used.

The device described in application Serial Number 277,964 comprises a high pressure ionization chamber, a source of potential and an amplifier, enclosed in a fluid-tight casing and adapted to be lowered into a well. Gamma-radiations or the like change the ionization of the chamber, resulting in a change of current. fiow therethrough and the amplifier is controlled by If a series of these parameters are made and fluid removed from the well between'their mak ing, the parameters will show progressively accentuated peaks at the points where the fluid enters, due to the entry of more and more fluid. If the fluid is more radioactive than the fluid in the well, the peaks will be in a positive direction, if less, they will lie in the other direction.-

A peak that starts at one point and then flattens out and reappears at a spaced point will indicate fiuid entry behind a casing at the first 'point and entry into the casing at the second point.

The attached drawing and the following detailed description thereof will give a more complete and detailed understanding of the principles and advantages of the invention. The sole figure of the drawing -is a diagrammatic illustration of a device for making surveys according to the principles of this invention.

The device illustrated in the drawing is a relatively simple form of a surveying instrument for the present purpose but -it is to be understood device of the type described in this inventors application SerialNumber 277,964, filed June '7,

that this device can be modified in accordance with the teachings of any of the patents or applications mentioned above and information of the type obtainable according to those patents application Serial Numberand applications can be used for the same gen eral purpose and the information that can be obtained by the relatively simple type of device here illustrated.

As shown in the drawing the device may consist of a cylindrical casing l0 adapted to be hermetically sealed and to enclose the necessary measuring equipment. This casing is suspended in the well bore by means of a cable I l which also serves to convey the measuring currents to the surface of the earth.

Within the casing I0 is an ionization chamber I2 in which is positioned a rodshapecl electrode l3 surrounded by a second electrode [4 preferably of sheet metal and in the shape of an open ended cylinder. The chamber is filled with an inert gas, preferably argon, under around 1500 to 2000 pounds per square inch pressure and connections from the electrodes extend through the walls of the chamber to the outside and, of course, are insulated from the chamber wall.

Outside of the chamber, but within the casing ID, a relatively high resistance 15 and a battery or other source of electrical potential 16 are connected in series across the electrodes. Preferably the negative pole of the battery is connected to the cylindrical electrode l4 and the positive pole is connected through the resistance Hi to the center electrode l3. It has also been found desirable to ground the positive pole of the battery to the main casing ID. The battery will preferably have a potential of around 150 volts and the resistor a resistance of around 10 ohms. Across the resistor I5 an amplifier I1 is connected which serves to amplify the potential drop across the resistor and send a current indicative thereof to the surface through the cable ll.

In operation the intensity of the radiations reaching the inside of the ionization chamber l2 governs the internal resistance of the. ionization chamber and hence the current flow through the resistor l5. This in turn governs the potential drop across the resistor and hence the signal sent to the surface by the amplifier.

At the, surface the cable ll passes over a measuring wheel l8 and is wound into a cable reel IS. The currents from the cable pass onto slip rings 20 on the cable reel from which they are taken by brushes 2| and passed to an amplifier 22. From the amplifier -22 they E0 to a recorder 23, the tape of which is driven in accordance with the movements of the casing l0 up and down in the well so as to record the measurements in correlation with determinations of the depth at which they are taken.

To accomplish the driving of the recorder tape in accordance with the movements of the casing In in the well the recorder is connected to the measuring wheel l8 through a mechanical or electrical transmission system 24. In actual practice it has been found desirable to use an electrical transmission system of the type known as the Selsyn transmission system.

4 In practicing the present invention the cable this process the hydrostatic pressure in the well is changed by any desired method, such for example, as removing a part of the fluid from the well, and thereafter a new parameter'is taken.

This process can be repeated as many times as is necessary and upon comparison of the parameters, if a fluid differing in radioactivity from that originally in the well enters from some strata along the well bore this will be apparent by progressively increasing peaks in the several parameters. As already indicated the peak may be in either a positive or a negative direction depending upon whether the fluid which enters the well is more or less radioactive than the fluid already in the well.

While it is intended that this invention be applied particularly to wells filled with liquid and to the determination of entering liquids it is also possible to apply this invention to wells filled with gases and to the entering of gases and under some circumstances it is even possible to apply the principles of this invention to a well filled with liquid but into which gas will enter when hydrostatic pressure is reduced or to a well filled with gas and into which liquid will enter when pressure is reduced.

Since numerous modifications within the scope of the general principles of this invention will immediately be apparent to those skilled in the art it is to be understood that this invention is not limited to the specific embodiment shown or described but only as indicated by the scope of the appended claims.

Iclaim:

1. A method of determining the point of entrance of fluid into a well bore that comprises taking a radioactivity versus depth parameter of the fluid in the well, reducing the hydrostatic pressure of the fluid in the well and taking a second parameter of radioactivity versus depth oi the fluid in the well.

2. A method of determining the point of entrance of a fluid into a well bore that comprises measuring at various depths in the well bore the radioactivity of the fluid in the well bore, simultaneously determining the position of each measurement and recording the determination of position and the measurement in correlation, reducing the hydrostatic pressure on the fluid in the well bore, repeating the measurements and recording and comparing the recordings mad prior to and after the reduction of the hydro" static pressure.

3. A method of determining the pointof entrance of fiuid into a well bore that comprises alternately taking radioactivity versus depth parameters of the fluid in the well bore and reducing the hydrostatic pressure of the fluid in the well bore, and comparing the parameters so m the liquid in the well, reducing the hydrostatic ducing the hydrostatic pressure on the liquid in the well bore, repeating the measurements and recording and comparing the recordings made prior to and after the reduction of the hydrostatic pressure.

6. A method of determining the point of entrance of liquid into a well bore that comprises alternately taking radioactivity versus depth parameters of the liquid in the well bore and reducing the hydrostatic pressure of the liquid in the well bore, and comparing the parameters so obtained.

7. The methodiof determining the point of en-