US2402433A - Treatment of oil wells - Google Patents

Description

2 sheets-shet 1 J. E. MUNNA TREATMENT OF OIL WELLS Filed-May 19. 1941 INVENToR `lune 18, 1946.

4, f .///vl INVENTOR 2 Sheets-Sheet 2 J. E. MUNN TREATMENT OF OIL WELLS vFiled May 19, 1941 June 18,1946?.

P'atented June 18,

UNITED STATES PATENT oI-FlcI 'y John E. Munn, Bellevue, Pa., assigner to Chemical Service Company, Pittsburgh, Pa., a partnei-ship comprising Theodore Schleid, Anita H. Munn, and John E. Munn Application May 19, 1941, Serial No. 394,101

1 This invention pertains to the production of petroleum from wells, and relates particularly to the reduction or'elimination of water from petroleum producing wells. e

In many cases new wells which are driven into oil-bearing sands or stratum produce a relatively large volume of water from the beginning of the operation of the well. In other cases wells which have been in production for a period of time gradually begin to produce water and as the operation of the well continues the water ows in an increasing amount until it mayI in some cases, entirely supplant the production of oil. The present invention is applicableto the drilling of new wells where it-is anticipated that water may be encountered and it' isalso applicable to the correction of existing wells which are now producing a considerable volume of water.

y In the oil ilelds where water is-encountered the' oil-producing sand or stratum is often immediately above a stratum containing water. The well is drilled into the sand far enough to produce oil but it is not drilled through the oil-bearing sand into the water.

In the ca s'e of the drilling of a new well, the operation of the drilling tool up and down in the bottom of the well or the head pressure of water.

or drilling mud in the well drives water which may be in the well downwardly through the forreduction in pressure due to the withdrawing of the oil from the producing sand creates an aspir ating effect and gradually causes the Water level immediately under the well to rise and at the same time capillaries are gradually opened up from the zoneimmediately under the bottom of the well downwardly toward the water. These capillaries'increase in size and eventually the entire zone in the oil-producing stream immediately below the bottom of the well becomes full y of capillaries through which the water can flow directly from the` water-bearing formation to the bottom of the well, and eventually a point may be 4 Claims. (Cl. 166-21) 2 reached where nothing but water is pumped by the well. e

According to the present invention it is contemplated that a iluid be introduced into the well which will -displace'the water in the capillaries. ,or channels and which is heavier than the water so as to force the water downwardly out of the capillaries or channels away from the bottom of the well. After its introduction, the heavier fluid is trapped in the formation at the bottom of the well, preferably by a specially constructed packer, where it remains as a barrier to the further flow of water into the well.

My invention may be more fully understood by reference to the accompanying drawings in which- Figure 1 is a schematic view representing the lower portion of a well -at the time that it rst begins to produce water in appreciable quantities;

Figure 2 is a similar View showing the growth of the channels through which water enters the well;

h Figure 3 is a similar view showing the intro- `duction of a correction packer into the well and illustrating the discharge of the first solutibn into the formation at the bottom of the well; l

s Figure 4 is a View similar to Figure 3 after the introduction of the second solution, two diierent solutions being used in succession in the correction of existing wells;

Figure 5 is a transverse vertical section through a correction packer used for the introduction of iiuids into the well and for the subsequent operation of the well;

Figure 5a is a horizontal section in substantially the plane of line 5ft-5a of Figure 5;

Figure 6 is a schematic view generally similar l to Figure 1 showing the stage at which drilling is temporarily halted to take steps to prevent the opening of capillaries through the producing y Figure 8 is a vertical section through oneform V `of production packer which is used in new wells.

Referring first to Figure 1, 2 designates the well which extends down into the oil-bearing sand or stratum 3.

producing sand and 5 designates the tubing through which oil is withdrawn or pumped rfrom the bottom of the well. Under the oil-bearing sand 3 is a water-bearing formation or stratum 6.

4 is the well-casing which usually terminates at some point above the oil- 3 Whenthe well is vproducing oil ows laterally through the oil-bearing sand into the bottom of the well and is withdrawn or pumped out of the well tubing 5. 'I'he oil flowing in from the sides and up the tubing creates a suction or aspirating effect at the bottom of the well, creat- "ing a zone of relatively lower pressure in the vicinity of the bottom of the well which causes the normal water level in the stratum 6 to rise. At the same time channels or capillaries through which the oil previously entered the bottom of the well tend to open up from the bottom 'of the well in a zone of downwardly increasing area. eventually communicating with the underlying water. In lFigure 1 the general character of these channels or capillaries at the time when the well first begins to produce water in appreciable quantities is diagrammatically illustrated. As shown in Figure 2, because the ow of water has become established an increasing number of passages from the bottom of the well tothe water level are created and eventually there is a zone generally in the form of a cone from the bottom of the Well down to the water-bearing stratum through which water is drawn into the well, in many cases to the complete exclusion of the oil.

In correcting a' well where such a condition exists, ya. specially constructed packer is first entered into the bottom of the well and set. One form of packer suitable for this purpose is illustrated in Figure 5. The particular packer is the subject-matter of a copending application filed by me, Serial No. 394,102. led May 19, 1941, (Patent Number 2,367,733, dated January 23, 1945 in which the packer is more fully described and claimed, and it will be described hereinafter only insofar as is necessaryfor an understand` ing of the present invention. The packer as shown in Figure has a main lower body portion 8 having a nipple-like element 8 secured to the lower end thereof. Secured to the nipple elel ment 8 is a compressible oil resistant resilient packing -body I0. The body I0 is preferably formed of a specially prepared rubber or plastic, which has the resilient and elastic properties of rubber but which is not affected by oil or chemical compounds used in the treatment of the well. Rubber coated with a synthetic rubber such, for example, as that known under the trade-mark 'I'hioko may be employed for this purpose. The packing I0 has a central passage II therein and there is a coil spring I2 in this central .passage to prevent the hole Il from closing when pressure is put on the packing and it is expanded at the bottom of the well.

The upper part of the body 8 has a neck portion 8a of reduced diameter and screwed on to the above the lower terminal portion of the tube,

the .perforations preferably being in the form of narrow slots. This perforated portion of the tubing provides al screen through which oil may flow after the well is againA put into operation. At the top of the tubing I8 is a conical body I4 about which are a series of radially movable slips I5 of a type commonly found in oil well packers.

faces to catch against the interior of the casing and hold the packer against upward movement. At the top of the body I4 is a collar- I8 and a compression spring I'I interposed between the collar I6 and a ring I8 serves to exert longitudinal .pressure against the ring I8 for forcing the slips I5 down over the conical surface of the body I4 for expanding the slips into contact with the casing.

Passing down through the body I4 and through the tubing I3 is a well tube I9. This tube is shown in Figure 5 as being screwed into the upper end of the neck 8a of the body 8.

Contained within the. body 8 is a plug 20 having an upper chamber 2I therein and having a central passage 22 therethrough with an upwardly closing ball check valve 23 in this passage.

The chamber 2| at the top of the .plug 20 has an internal thread which is a left-hand thread and screwed into the chamber is a disk 24 having a compressible plug 25 at the center thereof. As shown in Figure 5a, this disk has a series of openings 26 therein around the center and it is provided with two diagonally opposite upstanding pins 21. In the lower end of the tubing I! is a crosspin 28 which extends between the two pins 21 forming, in effect. a spline or wrench for turning the disk 24. The arrangement is such that when the well tubing I9 is rotated in a counterclockwise direction so as to screw it up wardly out of the neck 8a. of the body 8, the disk 24 will be turned, but because of the thread on the interior of the chamber 2l being a lefthand thread the disk will screw down as the tubing screws up to force thesealing D lug 2l plug this hole.

In the treating of the well the packer which has been described is'attached to the lower end of the Well tubing and itis lowered into the bottom of the well. Pressure on the well tubing causes the body I0 of packing material to be expanded against the sides of the well. When the compressed packing tends to re-expand by slightly lifting the well tube, it tends to lift the body l and the tubing I3 and the body I4. The conical surface of the body immediately expands the slips or grips I5 against the interior of the casing. thus setting the packer. so that the packing I8 re`- mains permanently under compression. At this time the disk 24 is in the position shown in Figure 5 and fluid may be introduced into the well tubing. This uid will flow down the well tube through the holes 28 in the disc 24, through the hole 22. forcing the valve 28 downwardly. The liquid may continue down through the packing I0 and be discharged into the bottom of the well.

In the practice of the present invention I preferably first introduce into the bottom of the well through this specially constructed packer a liquid whose function'is to enter the capillaries extending downwardly from the bottom of the wall and decrease the surface tension of the water in the area immediately below the bottom of the well. In Figure 3 the shaded area designated generally at 30 indicates the diffusion of this first liquid through the zone at the bottom of the well. Numerous substances may be used for this purpose. Ordinary alcohol, for example, will mix with the water and decrease its surface tension. Various industrial soaps may be used, ,or a wetting agent, such as that sold under the trade name of "Aerosol may be'employed. By the introduction of a wetting agent into the bottom the members I5 having serrations on their outer 75 of a well to reduce surface tension of the water,

the water wm tend to drain more freely from the capillaries. As the wetting agent is introduced it will tend to now downwardly and spread out lat-- erally, eventually permeating the conical zone extended from the bottomy of the well down to the normal water-level. The amount of wetting agent to be introduced has to be determined from known factors in the particular field in which the well is located. the amount depending very largely, however, upon the depth of the oil-bearing sand and the calculated distance from the bottom of the well to the normal water level. The fluid is introduced under pressure greater than the normal pressure inv the well.

After the first fluid has been introduced, a second fluid is introduced in the same manner. This second fluid is a liquid which is heavier than water. 'Ihe fluid is preferably one which is a solvent for oil and which, while normally not readily miscible with water will, by reason of the wetwater, mix to some extent therewith. 'I'he fluid which is preferably used is carbon tetrachloride, which substance is a solvent for petroleum vbut which is normally substantially insoluble in water. When the carbon tetrachloride is injected into ting agent which has been introduced into the the bottom of the well, it follows down the capillaries toward the water-bearing stratum.` Because of its being heavier than the water, it forces much of thel water down these capillaries out of the oil-bearing sand. Some of the water with the wetting agent in it will be forced upwardly into the sand around the bottom of the well. 'I'he action of the second fluid is diagrammatically illustrated in Figure 4 where the area 3| designates that zone through which the second fluid has '6 well. All of the liquid that can enter the well must flow into the well laterally in the zone above the packing I0. It enters the tubing Il through the slots therein and is then drawn or forced up into the well tubing. v

In the first short period of the operation of the well the water in the zone 30 will be withdrawn from the well. and after this water has been withdrawn the oil will flow laterally through the sand. One reason for the original entry of the water into the well is that the oil in flowing into the well and then up to the well tubing creates an aspirating effect or low pressure area imy mediately below the bottom of the well tending to raise the water level, and eventually draw the waterup through the oil-bearing sand into the- The provisionof a packingbottom of the well. I0 positively destroys this aspirating action. With this invention there is created a condition where. in the conical area immediately under the after produce water in any substantial quantitles for an indenite period of time.

This treatment of. the well is relatively inexpensive in that the chemicals used for the treatment are. relatively cheap and aside from the chemicals, the only additional equipment required isl the packer.

An important function of the packer'is Vits con- Y struction which pennits the forcing of the liquid of carbon tetrachloride to be used has to be de- 1 termined from the known facts about the well, including the depth of the oil-bearing sand and the distance between the bottom ofthe well and the normal water level. Y

After the second fluid has been introduced,the -well is then ready to be put back into operation. The first step in putting the well back into operation is to turn the well tubing I9 in a counterthe neck portion 8a of the body 8 at the bottom of the packer. 'Ihe turning of the tube in this direction screws the disk 24 downwardly, forcing the plug 25 against the top of the hole 22. 'I'he A check valve 23 forms one positive seal against any each forming a checkagainst the other -to assure against the back flow lof fluid through the packer.

When the well tubing I9 has been unscrewed from the neck 8a of the body 8 it is elevated a short distance above the body 8. After the tubdownwardly throughthe bottom of the well into the sand below the bottom and which positively seals the bottom of the well against any flowing fluid upwardly through the packer.

In the drilling of new wells in formations where water is anticipated, the drilling is proceeded with asusual until the drilling tool approaches relatively close to the oil-bearing sand. When the drilling has approached within a predetermined distanceof say, fty feet of the oil-bearing sand, the drilling operation is stopped and as much of the water as possible is bailed out of the bottom of the well. After the well has been bailed as dry as possible, a considerable quantity of liquid which is heavier than Water, preferably carbon tetrachloride, is poured into the zwell, after which the drilling is continued. -Thus instead of water being forced downwardly through the formations under the impact of thedrilling tool. carbonl tetrachloride is forced downwardly through these formations; When the oil-bearing sand is eventually reached and penetrated by the drilling tool. the capillaries are filled with carbon tetrachloride which is heavier than water and whlchtends to prevent the rise of water upwardly through the capillaries. Carbon tetrachloride also dissolves paramn deposits in the oildrilling operation is stopped and the carbon tetraing has been thus disconnected and raised, the

pumping of the well may be started. The packer at the bottom of the well prevents lany flow of liqbearing statum, thus enabling oil to flow more freely into the well.

Referring to Figure 6, this ligure indicates the depth to which the well is drilled, after which the chloride introduced into thel well 'while the dotted lines projecting downwardly from the well indicate the depth to which the well is to'be subsequently drilled. In thisgure the casing is desuid in a vertical direction directlyk up into .the ignat'ed 34. After the well has been drilled toits :,soasss 7 full depth, a packer is set in the bottom of the well to close the bottom of the well against the iow of fluid upwardly through it and prevent the aspirating effect heretofore described from drawing the water from the normal water level into the sand -in'the bottom of the well. One form of packer which may be used for this purpose is shown in Figures '7 and 8, while my copending application above referred to discloses another form of packer for the same purpose. Referring to Figure 7, 35 designates the well tubing, and $8 designates generally the packer at the bottom of the tubing. This packer has a shell 31 which is perforated to permit the flow of oil laterally from the sand into the interior of the shell. The well tubing 3B extends down into the shell `and terminates above the bottom of the packer.. Carried at the bottom of the packer is a body 38 of a resilient compressible material as. for example, synthetic rubber, or natural rubber coated with fThiokol. Under the weight of the superimposed column of tubing 35 the packingv 3l is expanded radially and compressed against the bottom of the well to eilectually seal the bottom of the well against any upow of fluids. The oil which ows through the perforated shell Il is. of course, drawn out through the tube 3l. Where the well flows under its own pressure I prefer to use a valve 38 at the top of the well so as to partially restrict the flow of oil because by restricting the flow of oil a greater pressure is vmaintained 'in the zone around the bottom of` direction.

The fluid which is heavier than water penetrates, as previously indicated, the water passages.

and capillaries in the oil producing stratum below the bottom of the well. It diffuses through the capillariesin a downwardly spreading cone with-the bottom of the well at the apex of the cone and serves as a blanket over the underlying water, filling the capillaries and preventing the water 'of this cone. definitely prevents 'the heavy liquid from being drawn back into the bottom of the well. Also, since the liquid is heavier than water, any suction will be more effective to move the oil which is lighter than water, than to move the liquid which is heavier than water, which is a further factor tending to prevent the rapid removal of the heavy fluid.

While I have illustrated and described certain specific apparatus for the practice of my invention and certain specific materials for use in carrying out my invention, it will be understood that various changes and modifications may be made, both in the apparatus and materials, and within the contemplation of my invention and the sco of the following claims. 1

I claim:

l. The method of treating oil wells in which water is present which comprises forcing a liquid capable of reducing the surface tension of water into the oil-producing stratum below the bottom of the well, thereafter introducing a second liquid consisting essentially of carbon tetrachloride into the same portion of the stratum to displace the water which has been treated with the first liquid, and thereafter sealing the bottom of the from rising. Being heavier than -the water, it will y act positively to force the water back through4 the capillaries, spreading out inl a conical pattern of downwardly increasing diameter. When the' treated well is subsequently being pumped the greatest suction is at the bottom of the well. This is due not only to the action of the pump itself, but to the aspirating effect of the oil flowing laterally inwardly. The packer, being at the apex well only below a given oil producing level against the upiiow of liquid therethrough.

2. The method of correcting producing wells in which water is flowing which comprises forcing a wetting agent into the oli-producing stratum in the zone immediately below the bottom of the well, and then forcing carbon tetrachloride into the same zone, and trapping the carbon tetrachloride in said zone.

3. The method of correcting producing wells in which water is flowing which comprises forcing a wetting agent into the oil-producing stratum in the zone immediately below the bottom of the well, then forcing carbon tetrachloride into the same zone, and thereafter sealing the bottom of the well against the direct upilow of fluid therethrough whereby the carbon tetrachloride is trapped in the zone into which it is injected.

4. A method of treating oil wells in which water is present which comprises forcing a liquid capable of reducing the surface tension of water through a tubing extending to the bottom of the well into the oil producing stratum below the bot-4 tom of the well, said liquid -being confined to penetration of the portion of the stratum at the bottom of the well only, thereafter in the same manner introducing into the oil producing stratum below the bottom of the well only a liquid consisting essentially of carbon tetrachloride, and then mechanically sealing the carbon tetrachloride so introduced in the oil producing stratum below the bottom of the well.

f- JOHN E. MU'NN.

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