US2590814A

US2590814A - Deep well treatment

Info

Publication number: US2590814A
Application number: US88802A
Authority: US
Inventors: Paul H Cardwell; Jr Albert W Coulter; Harry H Jones
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1949-04-21
Filing date: 1949-04-21
Publication date: 1952-03-25
Anticipated expiration: 1969-03-25

Description

Patented Mar. 25, 1952 DEEP WELL TREATMENT Paul H. Cardwell, Albert W. Coulter, Jr., and Harry H. Jones, Tulsa, Okla., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Application April 21, 1949, Serial No. 88,802

2 Claims. (Cl. 166-21) The invention relates to Vmethods of treating deep wells, such as those drilled into the earth for oil or other fluid. It more particularly concerns an improved method of preventing the intermixing of a liquid agent which is heavier than, and immiscible with another liquid on which it is superimposed on being introduced into a well through the usual tubing string.

In the construction and maintenance of a deep well, particularly one drilled for oil, it is sometimes desirable or necessary to deliver a charge of a liquid agent of one kind or another into the well through the usual tubing string without mixing the liquid agent with another liquid already in the tubing string or introduced thereinto ahead of the liquid agent.

Liquid agents that are lighter than those on which they are superimposed in a well tubing string generally remain in their same relative positions While standing in or traversing the bore of the tubing string without special precautions being taken to prevent intermixing. On the other hand, liquid agents that are heavier than and immiscible with those on which they are superimposed in a well tubing string become intermixed on standing in or traversing the bore of the tubing string unless special precautions are taken to prevent it.

Heretofore, in attempting to keep two superimposed liquids separated from ea-ch other in the tubing string in a well, when the upper liquid is heavier than and immiscible with the lower one, a more or less resilient cylindrical plug, usually of rubber, that makes a sliding sealing t in the tubing bore, has been used. In use, the plug is inserted in the tubing string ahead of the heavier liquid to be kept separated from the lighter one below it. However, this method of separating the heavier liquid from the lighter one has certain disadvantages which limit its usefulness. One of the disadvantages is that the plugs available do not always conform to all the irregularities encountered on traversing the bore of a tubing string. As a result by-passing of liquid occurs around the plug, thus allowing the one liq uid to mix with the other. In some instances, the plugs become damaged in traversing the bore of the tubing string, as when passing from one tubing length to another across the collars connecting each length of tubing in the string. After being damaged, the plugs usually do not prevent the one liquid from being intermixed with the other. In addition to the foregoing disadvantages, the conventional tubing plug has the disadvantage often-times of being in the way after having served its purpose and a removal operation is thereby necessitated as by drilling.

In so far as we are aware, there is no satisfactory commercially available method of preventing the intermixing of a liquid which is heavier than an" immiscible with another on which it is superimposed on being introduced into a well through the usual tubing string. Accordingly, it is the principal object of the invention to provide a method fullling this need.

We have discovered that by introducing into the tubing string, ahead 'of the liquid agent to be supported on a column of a lighter liquid therein with which the liquid agent is immiscible, another liquid that is heavier than and immiscible with the liquid agent and miscible with the liquid of the liquid column intermixing of the liquid` agent with the liquid of the liquid column is prevented.

For example, in an oil well provided with the usual tubing string containing a column of oil, a quantity of a relatively heavy oil-miscible liquid is introduced into the tubing string onto the oil column therein ahead of the liquid agent which is to be kept separated from the oil column. The oil-miscible liquid thus introduced, descends into the oil forming a solution therewith, the speciiic gravity of which is thereby raised to a value exceeding that of the liquid agent to be kept separated from the oil column. The liquid agent is subsequently introduced, and, being lighter than the solution on the oil column, iloats thereon as long as the speciiic gravity of the solution remain-s above that of the liquid agent. Although vthe specific gravity of the solution declines in time as the relatively heavy liquid diffuses into and is diluted by the lighter liquid, nevertheless, suicient time is had to permit the relatively heavy liquid agent to be lowered through a tubing string behind a lighter liquid column therein without intermixing of the two liquids.

The following examples are illustrative of th application of the principle of the invention in preventing the intermixing of a relatively heavy liquid agent supported in a tube as a liquid column on a column of a lighter liquid with which the heavier liquid is immiscible.

Example 1 A column yoi? crude oil 51 inches long is established in a glass tube standing vertically, having a bore of 0.5 inch. A quantity of carbon tetrachloride (Which is immiscible with the liquid to be supported), suflicient to increase the height of the oil column 23 inches, is introduced into the .the length of the oil column about 30 feet.

carbon tetrachloride-crude oil mixture. `immiscible liquid agent so introduced, yremains tubing. After the carbon tetrachloride has settled down into the oil column forming a relatively heavy solution in the upper part of the column, a quantity cf an oil-immiscible liquid agent to be supported thereon having a specific gravity of 1.13 sumcient to form a column 10 inches long in the tube is introduced. The oilimmiscible liquid remains supported upon the carbon tetrachloride treated oil column for approximately 20 minutes before the specific gravity of the solution in the upper part of the oil column declines below that of the oil-immiscible liquid, allowing the oil-immiscible liquid to drop through the oil column.

Example 2 An oil (crude oil) column is established in a string of 2 inch well tubing standing vertically. Enough carbon tetrachloride (about 5 gallons) is introduced into the top of the tubing to increase Several gallons of a relatively heavy oil-immiscible .liquid agenty consisting of a resin forming liquid composed of a partially condensed mixture of an `aldehyde and la phenol and capable of spontaneously hardening into a solid resin is introduced into'the tubing and allowed to descend uponfthe The oiloating upon'the'carbon tetrachloride-oil solu- .tion for approximately one hour before the specolumn.

. 'Example 3 In'a'setup similar to that of Example 2, but using 2.5 inch tubing in p'lace of the 2 inch tubing, approximately '7.5 gallons of carbon tetrachloride is. introduced into the tubing string ahead of the oil-immiscible resin-forming liquid which remains .supported for approximately one hour.

`While the foreging examples are illustrative of the manner in which the relatively heavy miscible liquid, interposed between the supporting liquid column and the relatively heavy immiscible liquid to-be vsupported may be used, it is to be understoodthat the `method is not to be limited thereby, inasmuch as the method is effective with .other liquids having similar characteristics as to .specic gravity, miscibility, and immiscibility,

Yand which occupies the uppermost position, and

the heaviest liquid (miscible) which occupies the position between the bottom of the column of the uppermost liquid and the top of the column of :the lowermcst liquid, may be moved downn wardly and without alternation of their relative positionsin the tubing string, as when the liquid agentismoved into 'the well hole through the tubing string behind the relatively light liquid column.

The invention may be further illustrated and explained by reference vto the accompanying drawing in which:

vFig. 1 is a schematic elevational viewof an oil well provided with the usual casing and tubing, showing the well and tubing string partially iilled with oil.

Fig. 2 is a similar view to Fig. 1, showing the addition to the top of the oil column in the tubing string of a quantity of a relatively heavy oilmiscible liquid.

Fig. 3 is a similar View to Fig. 2, showing the addition to the tubing string of the relatively heavy oil-immiscible liquid agentto be supported in the tubing string and kept separated from the oil column therein.

Fig. 4 is a similar view to Fig. 3, and shows a subsequent stage in the use of the principle of the invention.

In the several figures, like numerals designate 1 like parts.

Asshown inlFig. 1 the well bore I, extends from the surface of the earth 2, through the earth stratum .3, to be treated. The well above the stratum 3, is provided with casing 4, cemented in place with cement 5. Suspended in the well through the casing head 6, is a string of tubing 1,'the lower end 8, terminating opposite the stratum 3.

In carrying out the method in connection with the well illustrated, for example, an oil column 8 is normally standing in the'tubing string I at the commencement of the method (Fig. 1). A chargeiof a relatively heavy oil-miscible liquid is introduced into the' tubing 7, in an amount sufficient to increasethe'length of the liquid column 8, preferably between about 25 and 200 times the diameter of the bore of the tubing string. With very small bores of tubing e. g. 0.5 inch, an increase in liquid column length of about 25 times the diameterof the'column4 is suicicntto provide aboutSO iminutes :of Asupporting time before intermixing may be expected. With bores of .2-to 2.5 inchesyan increase in liquid column length of about to 200 diameters is desirable. After introducing the miscible heavy liquid into the tubing string, the liquid settles down into the oil column 8, forming a heavy solution' 9, with the upper part of column 8 (Fig. 2). The upper portion I0 of the solution is essentially undiluted heavy liquid while the lower portion II of the solution is essentially all oil. Thereafter, the relatively heavy oil 'immiscible liquid agent to be introduced into the well and kept separated from the oil column 8, is introduced into the tubing forming the liquid column I2 (Fig. 3). Being lighter than the liquid of the top I0 of the column 9, the liquid agent forming column I2, oats and remains floating as long as the relatively heavy butoil-miscibleliquid in column 9, does not become too highly diluted with the oil of the oil column 8 .below it. As aforesaid, such support may be had for a comparatively long period of time. In the vExamples 2 and 3, at least an hour elapses before the supporting power of the liquid column G, is lost by dilution.

-Afourth liquid i3, (Fig. .4) of lower specific gravity than the liquid I2, may be introduced into the tubing string. for the purpose of applying pressure upon the liquids below it, so as to force the various liquids into the well hole, as when it is desired to convey the liquid agent I2 through the tubing string into the Well hole I3, opposite stratum 3.

.As already indicated, the choice of separating liquid, referred tov generally heretofore as the relatively heavy miscible liquid, depends upon the specific gravity of the lliquid agent to be supported and the miscibility of the separating liquid with the liquid of the liquid column in the tubing string ahead ofiit. A wide choice of liquids is available for this use and their suitability for the purpose may be ascertained readily by measuring the specific gravity of the liquid agent to be supported and choosing as a separating liquid any liquid having a higher speciiic gravity than the liquid agent and which on dissolving in the column of liquid in the well, forms a solution that is immiscible with the agent to be supported. The following organic liquids are heavier than and miscible with oil and are illustrative of those which may be used on an oil column in the instances in which the specific gravity of the liquid treating agent to be supported is less than the organic liquid chosen: ortho and meta dichlorobenzene, ortho, meta and para dibromobenzene, ethylene dichloride, trichloroethane, acetylene tetrachloride, pentachloroethane, trichloroethylene, ,tetrachloroethylena trchloropropane, tetra chloropropane.

Among the advantages of the invention are, that the method prevents the intermixing of a relatively heavy liquid agent introduced into a Well through the usual tubing string ahead of a lighter one with which the former is immiscible irrespective of irregularities in the bore of the tubing string; and the use of tubing plugs is obviated along with their attendant diiculties.

We claim:

1. In the treatment of a deep Well, provided with the usual tubing string and having a column of liquid in the said tubing string, With a liquid agent which is immiscible with and of higher specific gravity than the liquid of the said column of liquid and capable of penetrating an earth formation, the method of preventing the liquid agent from descending through and mixing with the liquid of the said column of liquid on being deposited in the said tubing string which consists in depositing upon the said column of liquid, another liquid which is miscible with the liquid of the said column oi liquid and of higher specific gravity than the liquid agent in amount sufficient to increase the specic gravity of at least the upper portion of the said column of liquid to a value above that of the said liquid agent, and thereafter introducing into the tubing string, the said liquid agent.

2. In the treatment of an oil well, provided with the usual tubing string and having a column of oil standing in the said tubing string, with a liquid agent which is immiscible with and of higher specic gravity than the oil of the said column of oil and capable of penetrating an earth formation, the method of preventing the liquid agent from descending through and mixing with the oil column on being deposited in the tubing string which consists in depositing upon the said column of oil, a separating liquid which is miscible with and of higher speciilc gravity than the oil of the said oil column in amount suil'icient to increase the specific gravity of at least the upper portion of the said column of oil to a value above that of the said liquid agent, and thereafter introducing into the tubing string, the said liquid agent.

PAUL H. CARDWELL. ALBERT W. COULTER, JR. HARRY H. JONES.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,563,520 Owen Dec. l, 1925 1,889,889 Ennis Dec. 6, 1932 2,001,350 Mills May 14, 1935 2,122,452 Clason July 5, 1933 2,316,596 Kennedy Apr. 13, 1943

Claims

1. IN THE TREATMENT OF A DEEP WELL, PROVIDED WITH THE USUAL TUBING STRING AND HAVING A COLUMN OF LIQUID IN THE SAID TUBING STRING, WITH A LIQUID AGENT WHICH IS IMMISCIBLE WITH AND OF HIGHER SPECIFIC GRAVITY THAN THE LIQUID OF THE SAID COLUMN OF LIQUID AND CAPABLE OF PENETRATING AN EARTH FORMATION, THE METHOD OF PREVENTING THE LIQUID AGENT FROM DESCENDING THROUGH AND MIXING WITH THE LIQUID OF THE SAID COLUMN OF LIQUID ON BEING DEPOSITED IN THE SAID TUBING STRING WHICH CONSISTS IN DEPOSITING UPON THE SAID COLUNM OF LIQUID, ANOTHER LIQUID WHICH IS MISCIBLE WITH THE LIQUID OF THE SAID COLUMN OF LIQUID AND OF HIGHER SPECIFIC GRAVITY THAN THE LIQUID AGENT IN AMOUNT SUFFICIENT TO INCREASE THE SPECIFIC GRAVITY OF AT LEAST THE UPPER PORTION OF THE SAID COLUMN OF LIQUID TO A VALUE ABOUT THAT OF THE SAID LIQUID AGENT, AND THEREAFTER INTRODUCING INTO THE TUBING STRING, THE SAID LIQUID AGENT.