US1889889A - Method of testing open wells - Google Patents

Description

Dec. 6, 1932'. G, H, ENNls 1,889,889

METHOD OF TESTING OPEN WELLS Filed Feb. 3. 1930 2 Sheets-Sheet l v ELECTROLYTE [NI/ENTaR' ear e H [121219 A TragggEX Dec.'6, 1932. a. H. ENNIS ,3

' METHOD OFTESTING OPEN WELLS File d Feb. 3. 1930 2 Sheets-Sheet 2 sz' 725/5. $514. I

Patented Dec. 6, 1932 YEUNITED STATES" PATENT. OFFICE:

Gannon H. ENNIS, or LONG amen, cannroimm, ASSIGNOR or ONE-HALF 'ro ROBERT v. 1

JUNE, OF LONG BEACH, CALIFORNIA rmrnon or trnsrineoran warms l Application filed February 3, 1930. Serial No. 425,521.

My invention relates to the testing of a well for determining. the point at which water enters the well, and it further relatesto an improved electrolytefor use in such tests.

i In the drilling of an oil well it invariably occurs that water bearing strata are penetrated before the oil sands are reached. The

water bearing strata must be sealed from the well; otherwise,the water will run thereinto, forming an emulsion, and in some'instances reducing the oil yield of the well tothe extent that the operation of the well is impractical.

According to present practice, the well is drilled and .various' casings are set in place. If it is found that water is leaking into the well, the point of leakage must be found and the water bearing strata mustbe sealed off. This sealing operation is usually ''accomplished by extending a casing down to a shale or rock stratum below the water bearing strata and cementing the casing thereto. The last casing usually installed in a well is known as the oil 'string- The lower end of the oil stringis extended into the oilsands and is perforated to allow the oil'to enter. a

The upper end of the oil is above the surface of the ground and is connected to piping for conveying away the oil. Some-* times water bearing strata are located adj acent the oil sands,and a portion of the perforated pipe passes therethrough, this allowing the ingress of water into the well. When this condition exists, thewater bearing-strata must be found and cemented from the well.

The foregoing outlines the procedure of installing casing and cementingcasing in a well when water leakages are" encountered.

. There are processes at-present for locating the leakage of water into the well after the caslng strings have been set, and such a process is disclosed in my patent entitled Method and apparatus for determining the location of water strata in wells, No. 1,786,196, issued Dec. 23, 1930. Y

During the" period of drilling and setting the casing, the well is kept full of rotary mud, which serves a number of purposes, such as holding the formations in place, preventing cave-ins and preventing premature flows of and the rotarymud removed from the well,

so that the hydrostatic head is reduced suf ficiently' so that the pressure against the formations is insufiicient to restrain an inward flow. At this time if there are any I openings in or around the casing adjacent to or in communication with the water strata, the'water will start to leak into the well.

It will therefore be seen that ordinarily the operator of the well has no way 0f.kn0wing whether'or not there will be water leakages into the well until after all the casings have been installed and the rotar mud removed from the well so that the hy rostatic head is reduced. Many thousands of dollars are sometimes spentin installing a casingin a well, and then when the rotary mud is removed, it is found that water still leaks into the well.

It is the purpose of my present invention 1 to provide a method whereb the well may be tested for water leakages efore all of, the

casings have been setand' before the rotary mud has been removed, thus enabling the water leakages to be located and then sealed from the well by cementing or by the installation of the next casing. My invention further makes it possible to test a well for water leakages before any flow of oil has been started. I

The preferred method of my invention includes the placing of an electrolyte in the well near the leakagepoint, if it can be estimated from the log of the well, or throughout the entire wellif nece ssary, moving a pair of electrodes through the electrolyte, the electrodes cooperating with the surrounding portion of the electrolyte to provideta voltaic'cell, and measuring the potential difi'erencebetween the electrodes as they are moved through different positions in the well. As water seeps into the well, the electrolyte is weakened, which will change the potential difference between the'electrodes and thus indicate to the operator whereat the leakage occurs. In performing my method inan open hole.

portion is unprotected by easing, the rotary imud 1S maintained in the hole for a number of reasons, as pointed out above. In order to test the well to locate the water strata, an electrolyte must be introduced into the well.

This electrolyte which is to be used must possess all of the qualities of the rotary mud, such as pointed out heretofore, as well as its electrochemical qualities. It is further neeessar that the electrolyte have qualitieswhic prevent it from stratifying and prevent it from being driven into the formations by the hydrostatic head in the well.

My invention provides an electrolyte which has the essential qualities as specified above,

which renders the method of testing in an open hole a success, by preserving the condition of the well during the testing.

I will now describe my invention in detail,

and during the course of the following description reference will he hadto the accompanying drawings in, which:

Fig. 1 is a view illustrating a drilled well which is ready to be tested by my invention. Fig. 2 is a view similar to Fig.1 showing the testing apparatus in the well, which testing apparatus is of a type capable of performing my invention. a

Fig. 3 is an enlarged sectional view showing a portion of the well with the electrolyte of my invention therein showing the manner in which the water leakage occurs to-dilute the electrolyte.

Fig. 4 is a section through the electrode carrier used in performing my invention. 4

Fig. 5 is a section'taken on the line 55 of Fig. 4. v

Fig. 6 is a chart showing a series of tests actually made on a well of the Associated Oil Company in southern California.

'Referring particularly to Fig. 1, the numeral 11 represents the well. According to customary methods well casings 12 and 13 are installed in the upper end of the well and cemented in place, as indicated at 14. The numerals 15'and 16 represent shale or rock formation. The numeral 17 represents a water bearing formation, and the numeral 18 represents the oil sand. Fig. 1 shows the well after drilling operations have ceased and before the final casing is set. The well at this time is filled with rotary mud 19 in order that the lower open portion 20 of the well will receive the necessary reinforcement to prevent cave-ins, and'in order that there will be no flow of oil prior to the installation of the final casing and the necessary preparation at the surface of the well.

If any of the rotary mud is removed from the well at this time, the hydrostatic head mud, such as holding the preventing bridging, lubricating the walls will be reduced, and thewalls of the open hole may cave 1n. It is the usual practice to install the various casings in the well immediately after the drilling operations have been completed and to then-remove the r0 tary mud from the well. If the siibterranean The first step in the process of my inven tion is performed when the well is in the condition shown in Fig. 1;thatis to say, drilling operations have been completed and the well is full of rotary mud, as shown.

The'first step consists in introducing an electrolyte into the well. The electrolyte, which is indicated by the numeral 21 in Figs. 2 and 3, maybe introduced at certain portions of the well so that the well may be tested by stages, or the entire well may be filled with this electrolyte.

The electrolyte which is used in the process must serve all of the purposes ofrotary of the well, preventing cave-ins, controlling the pressures, controlling the water, controlling the oil, controlling the gas, and holding angle formations in tion to this, the electro te must have its electrochemical characteristics and function as a part of a voltaic cell. The electrolyte which I use includes a number of substances to endow it with the necessary characteristics.

For the'electrochemical qualities .1 may use a solution of ammonium chloride, which isstrongly ionizable, or an equivalent ionizable materiag which will retain its electrochemical qualities in the presence of the other substances the electrolyte.

I may also use as an electrochemical material a solution which includes ammonium sulfate, sodium sulfate, and a colloidal material in a solution which is acid, with sulfuric acid and chromic acid. The colloidal material which I prefer to use is alcohol fermentation product of waste molasses after the removal of the alcohol therefrom. It is known teehnicallyas slop. This electrochemically active solution may be made as follows:

#1 Slop solution ormation in place,

lace; and in addiwhich comprise a part of cold water.

\ weight) 66 Be. sulfuric acid.

#2 Ammonium sulfate solution f tilizer grade ammonia) in 60 gallons of [#3 Sodium biahromate solution 3% parts ("by weight) water, 3 parts by weight) sodium bichromate, 1 part 'Mia-ing Take 90 gallons ammoniumv sulfateof A solution. Make up 150 gallons of sowell by patented dose distributor.

amount of solution used is 1 gallon of sumv tionapproximately to each 48 gallons of terial, or colloidal mineral, which is dium bichromate or B solution. Mix 4 parts by volume of A solution and 6 parts of B solution, making 250 gallons of chemical solution to be distributed in fluid contents1 lof e liquid in the well. 7

To endow the electrolyte with the necessary weight qualities which are essential to'the electrolyte in order that it may support the walls of the holeand holdback the flow of oil, a heavy mineral in finely divided form is included in the electrolyte. As a weight material I prefer to use barium sulfate, BaSO and in some instances I add to'the barium sulfate a glutinous or colloidal mineral, such as bentonite clay or other colloidal clays. The purpose of the bentonite clay, or the colloidal ineral, is to prevent the electrolyte from ing driven by the hydrostatic head into the formation and to prevent stratis -fi cation of-the different substances which compose the electrolyte.

' The proportions of the electrochemical material and the weight material, which is preferably barium sulfate,'and the glutinous m:-

' erably bentonite clay, is used in accor ance withthe requirements of the well. In some wells the formation is such that the specific gravity of. the electrolyte may be lower than in other instances, and likewise in some wells it is desirable to use more or less colloidal mineral ingredients with the tendency of the electrolyte to penetrate the strata. In some instances the colloidal material may beeliminated, but I havefound that the most satisfactory electrolyte is formed when at least a small percentage of colloidal mineral is used, due to the fact that the colloid'al'min- ,eral acts as a suspender and prevents the different substances of the electrolyte from stratifying. j

As an example of the proportions which I may use toform the electrolyte of my in- 1 vention, I give the following formula. It

hours.- Siphon 51! 10 Dissolve 300# of ammonium sulfate (fershould be understood, however, that this formula is illustrative only, and I do not intend to limit myself to the proportions stated.

Per cent The electrolyte may be introduced into the well. in various manners. One way of introducing the electrolyte is to use the distributor disclosed in my patent for dosedistributor,

No. 1,725,979, patented Au ust' 27, 1929.

Another met lyte' is to extend into the well 11 a pipe or tube 25 which is connected to a pump 26 which draws the electrolyte from a source of supply. The electrolyte is pumped through the pipe 25 into the well, the lower end of the pipe extending to the lower end of the well or to i a point where the electrolyte is to be introduced. By this means the entire well or a portion of the well may be filled with electrolyte. If'desired, it is practical to test the well in sections, filling different portions of the well with electrolyte, so that it is not necessary to use a large amount of the electrolyte. In Fig. 2-the electrolyte 21 is shown as placed between the lower andupper bodies of rotary mud 30 and 31 respectively. It is sometimes possible to locate the ingress of water by the use of a charge of electrolyte which isproperly placed according to indications given to the driller during the drilling operation. a

In the step of introducing the electrolyte into the well it is absolutely essential to maintain a hydrostatic head-which is sufiicient to prevent cave-insand to prevent a premature flow of oil. The two methods outlined are iatisfactory ones for introducing the electro-- yte.

0d of intro ucing the electro- Thenext stepin the process isto make a test of the well to determine the-uniformity of the electrolyte which has been introduced.

This is accomplished byusing the testing device shown in Figs, 2, 4, and 5.

The testing device consists of a frame '32 having a guide means 33 at the lower end thereof and having a cable 34 attached to the upper end thereof. Supported in theshell 32 is an insulation block 35 having a central opening 36, which insulation block 35 supports a. pair of relatively spaced electrodes 37 and 38.

The electrodes 37 and 38 must be made of such material aswill cooperate with the electrolyte to form avoltaic cell.. It is well known in the art what metals may be used'for this purpose. In my device, I find it electrical conductors 40 and 41 which may be extended to the surface of the ound through the cable 34. The cable 34 extends over a guide sheave 42 and may be wound on a suitable drum 43. The conductors 40 and 41 are joined to rings 44 and 45 which are engaged by brushes 46 and 47 respectively. The

ushes are included in conductors 49 which are joined to a millivoltmeter 50. The testing device, which will be generally indicated by the numeral 51, is lowered by means of the cable 34 through the electrolyte 21. When- I passing through the electrolyte 21, themillivolemeter 50 should give a constant reading and usually 'ves a reading of about 200 oints which is about 10 millivolts. If it is ound that the electrolyte is uniform, the next step in the process is conducted. If a nonuniform reading is obtained, a redistribution of the electrolyte must be performed.

' The next step in theprocess is to cause the flpw of fluid into the well from the surroundin formation. This is preferably accompllshed by reducing the hydrostatic head in the well. A bailer may be extended into the upper end of the well, and a relatively small amount of the rotary mud or of the electrolyte removed from the top of the well. When the hydrostatic head is thus reduced, the pressure of the electrolyte tending to hold the fluid -in the formation is reduced and will permit an inflow into the well. As shown best in Fig. 3, the electrolyte adjacent to the water bearing formation will be diluted or' weakened, as indicated at 60, by the inflow of water. u

' The testing apparatus is again moved through the electrolyte in the manner just described. 'Where the electrolyte is undiluted, thereading will be the same as prior to the step just described of causing fluid to flow into the well from the surrounding formation. Where the fluid has flowed into the well, however, the strength of the electrolyte will be reduced and the millivoltmeter will show a lower reading. Another way of expressing the same function is that when the two electrodes 37 and 38 are in the unadulterated electrolyte, the potential difference will remain constant. When the. electrodes move to that portion of the electrolyte which has been diuted and Where the electrochemical action has been reduced, the potentialdifference between the electrodes will be reduced in a certain proportion.

It is usually desirable to retest a well two or three times by performing the two preceding steps. In other words, the hydrostatic head is reduced to permit the flow of fluid into the well, and the test is'made; then the hydrostatic head is again reduced to cause a flow of additional Water into the well.

. In Fig. 6, the test chart shows four tests was made before the hydrostatic head had been reduced. Test No. 2 was made after the h drostatic head had been reduced once. Test 0. 3 was made after the hydrostatic head had been reduced. twice, and Test No. 4 was made after the hydrostatic head had been reduced a third time. At the upper end of the separate readings, the numerals 20, 40, 60, etc. to 200, represent calibrations on the millivoltmeters. The cross-hatched portions of the chart represent the reading given by the millivoltmeters at the various depths mdicated on the left side. of Fig. 6. In Test No. 2 it is shown that the electrolyte was diluted at a depth of 8250 to 8270 feet. Test No. 3 shows that the electrolyte H at 8260 to 827 0 feet'was diluted the most. As

more water had entered the well, however,

the water spread slightly so that the dilution ofthe electrolyte commenced at 8190 feet. In Test No. 4, a complete bridgin of,

the water occurred at 8270 feet. The ilution of the electrolyte extended up to 8040 feet. The chart shown in Fig. 6 has been .made from readings taken during the test of a well in southern California.

' The step just described in connection with Fig. 6 completes the" method of my invention. The location of the water entry has been found, and, as indicated by the chart referred to, the water in that particular well entered at a level of 8250 to 8270 feet. The next activity in the well is to seal the water bearing stratum from the well. This may be done by extending a casin' downward to the shale or rock stratum, suc as 16, located below .the water bearing formation 17. The casing is then cemented in place, which completely, seals the water from the well. some cases the leakage ma forming a cement plug in til drilling through it.

e well and then In be arrested by The operator will then install the oil string and prepare the equipment at the surface of'the ground for accommodating the oil. The rotary mud is then removed. If the well is. a flowing well, the oil will commence to flow. If not, pumping apparatus must be installed and the oil pumped to the surface of the ground. '1

My invention is not limited to use in o n hole's but may be used after all casing his been set and either before or after the rotary mud has been removed. I claim as my invention:

1. A method of testing a well to find water leakages, prior to the removal of rotary mud from the well, said method comprising: placing a body of electrolyte in said well between layers of rotary mud; bailing rotary mud from the upper end of the well to allow an ingress of water; and electrochemically testing said electrolyte to determine whether or not it has been diluted.

65 which 'were made on a well. Test No. 1 2. A method of testing a well to'find water leakages, prior to the removal of rotary mud from the well, said method comprising: incorporating a weight material in an electrolyte; placing a body of said electrolyte in said well between layers of rotary mud; bailing rotary mud from the upper end of the Well-to allow an ingress of water and electrochemically testing said electrolyte to determine whether or not it has been diluted.

3. A method of testing a wellto find water leakages, prior to the removal of rotary'nuld ,from the well, said method comprising: in-

, leakages, prior to the removal of rotary mud from the well, said method comprising: iu-

corporating a weight material and a glutinous material in an electrolyte placing a body of said electrolyte in said well between layers of rotary mud; bail-ing rotary mud from the upper end of the well to allow an ingress of water; and electrochemically testing said electrolyte to determine whether or not it has been diluted:

5. A method of testing a well to find water leakages, prior to the removal of rotary mud from the well, said method con'iprising: incorporating a weight material and a colloidal clay in an electrolyte; placing a body of said electrolyte in said well between layers of rotary mud; bailing rotarymud from the upper end of the well to allow an ingress of water; and electrochemically testing said from the well, said method comprising: forming an electrolyte of substantially the same glutinous characteristics as said rotary mud; placing a body of said electrolyte in said well between layers of rotary mud; bailing rotary mud from the upper end of the well to allow an ingress of water; and electrochemically testing said electrolyte to determine whether or not it has been diluted. 9. A method of testing a well filled with a liquid, said method comprising: incorporating a weight material in an electrolyte to make it of substantially the same specific gravity as said liquid; placing said electrolyte in said well between two layers of liquid; bailing said liquid from said well, and electrochemically testing said electrolyte- In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 28th day of January, 1930.

Y GEORGE H; ENNIS.

electrolyte to determine whether or not it has been iluted. I I

6. A method of testing a well to find water leakages, prior'to the removal of rotary mud from the well, said method comprising: a

forming an electrolyte of substantially the samedensity as sai rotary mud, placing a body of said electrolyte in said well between layers of said rotary mud; bailing rotary mud from the upper end of the well to allow an ingress of water; and electrochemically testing said electrolyte to determine whether or not it has been diluted.

'7. A method of testing a well to find water leakages, prior to the removal of rotary mud from the well, said method comprising: forming'an electrolyte of substantially the same viscosity as rotary mud; placing a body of said electrolyte in said well between layers of rotary mudibailing rotary mud from the upper end 'of the well to allow an ingress of water; and electrochemically testing said electrolyte to dotern'line whether or not it.

has been dilutdd.

8. A method of testing a well to find water

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