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Publication numberUS3724564 A
Publication typeGrant
Publication dateApr 3, 1973
Filing dateNov 12, 1971
Priority dateNov 12, 1971
Publication numberUS 3724564 A, US 3724564A, US-A-3724564, US3724564 A, US3724564A
InventorsJ Messenger
Original AssigneeMobil Oil Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Technique for controlling lost circulation
US 3724564 A
Abstract
This specification discloses a method of controlling lost circulation in drilling operations. In carrying out the method of the invention, an aqueous mixture of a dispersing agent, an inert particulate material, and a water dispersible oleophilic colloid is introduced into the well. This aqueous mixture is circulated down the well and into the vicinity of a formation into which lost circulation is occurring. The aqueous mixture is then mixed with an oleaginous liquid and a gel is formed which tends to plug the formation into which lost circulation is occurring. The oleophilic colloid may be a normally water swellable clay such as bentonite which has been treated to render it oleophilic. The oleaginous liquid may comprise an oil-base drilling fluid utilized in drilling of the well. The inert material may be a weighting material such as barite.
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United States Patent 1 Messenger 11] 3,724,564 [451 Apr. 3, 1973 [21] Appl. No.1v 198,357

[52] U.S. C1 .1 ..175/72, 166/294 [51] Int. Cl. ....E2lb 21/04, E21b 33/13, E21b 43/00 [58] Field of Search ....175/72, 70, 65; 166/292, 293,

[56] References Cited UNlTED STATES PATENTS 2,531,812 11/1950 Hauser 252/85 2,637,692 5/1953 Nahin ..252/8.5 2,675,353 11/1954 Dawson ..252/8.5 2,776,713 l/19S7 'Morgan et al. ..l66/293 2,800,964 7/1957 Garrick .'..166/293X 2,990,016 .6/1961 Goins,.1r. et al. .......-166/293 3,070,179 12/1962 Moore ..l75/72 3,411,581 11/1968 Alpha ..175/72X 3,448,800 6/1969 Parker et a1. ..175/72X 8/1969 Kelly,'Jr. ..l75/72X 9/1969 Kelly,Jr. ..l75/72 Primary Examiner-Stephen J. Novosad Attorney-William J. Scherback [57] ABSTRACT This specification discloses a method of controlling lost circulation in drilling operations. In carrying out the method of the invention, an aqueous mixture of a dispersing agent, an inert particulate material, and a water dispersible oleophilic colloid is introduced into the well. This aqueous mixture is circulated down the well and into the vicinity of a formation into which lost circulationis occurring. The aqueous mixture is then mixed with an oleaginous liquid and a gel is formed which tends to plug the formation into which lost circulation is occurring. The oleophilic colloid may be a normally water swellable clay such as bentonite which has been treated to render it oleophilic. The oleaginous liquid may comprise an oil-base drilling fluid utilized in drilling of the well. The inert material may be a weighting material such as barite.

9 Claims, 1 Drawing Figure lo 3o OIL PHASIE, VOL.%

l so} 1 so I l l.67t| 321 VOLUME RATIO OF OLEAGINOUS LIQUID AQUEOUS MIXTURE Pmmwma ma 3.724.564

JOSEPH U. MESSENGER INVENTOR Ev /W A954? ATTORNEY BACKGROUND OF THE INVENTION This invention relates to the drilling of wells into the earths crust and more particularly to a new and improved method of lost circulation control in such drilling operations.

In the drilling of wells into the earth to penetrate subterranean oil-containing formations, there is commonly employed a drill string having a drill bit connected to the lower end thereof. The drill string is rotated, thereby rotating the drill bit which penetrates the earth by cutting and breaking the formation whichit contacts. Drilling fluid is conventionally circulated down the drill string and through ports provided in the drill bit and back to the surface through the annulus formed between the drill string and the wall of the well. The circulating drilling fluid performs numerous functions including removing the cuttings from the well, cooling the bit, and applying hydrostatic pressure upon the penetrated formations to control fluids contained under pressure therein. Drilling muds which may be either oil base or water base are commonly utilized as drilling fluids. These drilling muds are normally treated to provide desired rheological properties which make them particularly desirable for use in drilling wells. For example, drilling muds may be treated to increase the density thereof by adding thereto such materials as barium sulfate (barite) and lead sulfide (galena).

One difficulty which is often encountered in drilling operations is lost circulation which involves the loss of unacceptably large amounts of drilling fluid into a formation penetrated by the well. Such a formation is commonly termed a lost circulation zone. Lost circulation may occur when the well encounters a formation .of unusually high permeability or one which has naturally occurring fractures or fissures. Also a formation may be fractured by the hydrostatic pressure of the drilling fluid, particularly when a changeover is made to a relatively heavy mud in order to control high formation pressures. Numerous techniques have been developed in order to control lost circulation. One common expedient is to increase the viscosity of the drilling fluid in order to increase its resistance to flow into the formation. Another technique involves the addition of bulk material, such as cottonseed hulls, sawdust, or ground walnut shells, to the drilling fluid. Also, it has been proposed to place a soft plug such as a gel formed by a liquid-clay dispersion into the lost circulation zone. For example, as disclosed in. U.S. Pat. No.

2,800,964 to Garrick, a gel may be formed within the well by mixing an aqueous liquid and an oil dispersion of a hydrophilic clay and the gel forced into the lost circulation zone. In another procedure, a hydraulic cement slurry may be placed in the lost circulation zone and allowed to set.

In U.S. Pat. No. 3,467,208, to John Kelly, .lr., there was disclosed a method of controlling lost circulation in drilling operations. In accordance with Kelly, an aqueous suspension of an oleophilic colloid which is both water and oil dispersible is introduced into a drill string which extends into a well. The aqueous suspension is circulated through the drill string and into the wellbore where it is contacted with an oleaginous liquid to form a gel which tends to plug the formation into which lost circulation occurs.

SUMMARY OF THE INVENTION The present invention is an improvement to the aforementioned U.S. Pat. No. 3,467,208 and to a copending patent application, Ser. No. 198,247, entitled METHOD OF CONTROLLING LOST CIRCU- LATION, by John Kelly, .Ir., filed of even date with the present application. In accordance with the present invention, there is provided a method of alleviating fluid loss into a subterranean formation penetrated by a well. There is introduced into the well an aqueous mixture of a dispersing agent, an inert particulate material, and a water dispersible oleophilic colloid which acts as an oleaginous gelling agent. This aqueous mixture is circulated down the well and into the vicinity of the formation where it is mixed with an oleaginous liquid, thereby dispersing the oleophilic colloid in the oleaginous liquid and forming a gel. This gel tends to plug the formation and mitigate the loss of fluid thereinto.

I BRIEF DESCRIPTION OF THE DRAWING The drawing is a graph showing the effect of the inclusion of inert particulate material into an aqueous mixture of dispersing agent and oleophilic colloid when mixed with an oleaginous liquid.

DESCRIPTION OF THE PREFERRED EMBODIMENTS relatively little or no gelling action in an aqueous liquid.

Particularly suitable for use in the present invention are the normally water swellable clays which have undergone treatment to render them oleophilic. Exemplary of suitable oleophilic clays are the bentonites or other clays which have been treated with an oil-wetting surfactant such as a long-chain quaternary or nonquatemary amine. For a more detailed description of such clays and the method of preparation, reference is made to CHEMICAL ENGINEERING, March 1952, pp. 226230; U.S. Pat. No. 2,531,812 to I-Iauser; and U.S. Pat. No. 2,675,353 to Dawson, Suitable oleophilic clays also may be prepared by dehydrating a hydrophilic clay such as bentonite, and then treating the dehydrated clay with a glycol or glycol ether. For a more detailed description of this procedure, reference is made to U.S. Pat. No. 2,637,692 to Nahin. Suitable oleophilic colloids are available under the trade names of Geltone and Petrotone.

The dispersing agent employed :in carrying out the present invention may be any suitable material which functions to promote and maintain separation of the individual, extremely fine particles of solids which are usually of colloidalsize. As will be recognized by those skilled in the art, various such dispersing agents are conventionally employed in drilling muds in order to maintain adequate dispersion of clays added to impart desired rheological properties to such muds. Also, as will be recognized by those skilled in the art, certain dispersing agents are more effective in alkaline environments and therefore it may be desirable to adjust the pH of the liquid medium into which the dispersing agent is added to an alkaline pH. The pH may be adjusted, for example, by adding caustic soda to the liquid medium. Examples of dispersing agents which may be used are lignites, chrome lignosulfonates, other lignosulfonates such as iron, nickel, and cobalt lignosulfonates, tannins, and complex phosphates such as polyphosphates and pyrophosphates. Dispersing agents which have been found to give particularly good results when used in accordance with this invention and which are therefore preferred are chrome lignosulfonates and ferrochrome lignosulfonates.

The inert particulate materials employed in carrying out the present invention may be any suitable inert particulate materials conventionally employed in drilling muds. By inert particulate materials is meant materials which are resistant to physical and chemical action.

Such inert particulate materials are particularly resistant to physical action such as swelling when contacted by the aqueous and oleaginous liquids employed in carrying out this invention. Examples of inert particulate materials which may be employed are barium sulfate, commonly called barite; lead sulfide, commonly called galena; calcium carbonate; and silica. Of these, barite is preferred because it is more readily available and less expensive.

The present invention is directed to a method of controlling lost circulation which is primarily applicable when an oil-base drilling mud is employed in the drilling of the wall. In accordance with this invention, there is prepared an aqueous mixture of an oleophilic colloid and a dispersing agent, as is described in 'copending application, Ser. No. 198,247, entitled METHOD OF CONTROLLING LOST CIRCULA- TION, by John Kelly, Jr. Into this aqueous mixture there is added an inert particulate material of the type conventionally employed in drilling muds. The aqueous mixture is pumped down the well where it is mixed with an oleaginous liquid to form a soft plug or gel in the vicinity of the formation into which lost circulation is occurring. This gel then serves to plug the formation and mitigate the loss of fluid thereinto.

The inclusion of inert particulate materials into the aqueous mixture enables the weight of the aqueous mixture to be tailored to the weight of the drilling mud in the well. This is particularly important when a long column of aqueous mixture is employed in a well having fluid communication with formations that contain fluids under high pressure. The inert particulate materials in the aqueous mixture occupy space which would otherwise be occupied by the oleophilic colloid. Experimental data later presented shows that the inclusion of inert particulate material enables a gel having suitable yield strength to be formed with a lesser amount of oleophilic colloid than would otherwise be required. Also, a lesser amount of oleaginous liquid is required to be mixed with the aqueous mixture to form a gel. Thus, the inclusion of inert particulate material facilitates the mixing downhole of the oleaginous liquid with the aqueous mixture in forming a gel.

This invention normally will be used most advantageously in conjunction with the drilling procedures employing an oil-base drilling fluid, which drilling fluid is pumped downward through the drill string and upward to the surface of the earth through the annulus. Accordingly, this invention is described primarily with reference to such a procedure.

When a lost circulation zone is encountered during drilling, as evidenced for example by a decrease or loss of drilling fluid returned from the well annulus, the introduction of the drilling fluid into the drill string is temporarily suspended and a slug of an aqueous mixture of a dispersing agent, oleophilic colloid, and inert particulate material is introduced into the drill string.

Thereafter, the drilling fluid is again introduced into the drill string and an aqueous slug is entrained within the column of drilling fluid and circulated down the drill string thence into the well through the outlet ports of the drill hit. As the aqueous mixture enters the well, it is mixed with the oleaginous liquid provided by the oil-base drilling fluid and reacts with this liquid to form a gel.

The aqueous mixture of oleophilic colloid, dispersing agent, and inert particulate materials is preferably blended at the surface into a pumpable slurry. Such a slurry is most readily formed by adding the dispersing agent to the water prior to or concomitantly with the addition of the oleophilic colloid and inert particulate materials thereto. Though this step is most desirable when a maximum amount of oleophilic colloid is to be blended into the aqueous mixture, it is still desirable when less than this maximum amount of oleophilic colloid is to be employed in the aqueous mixture.

The amount of dispersing agent employed in carrying out this invention is that amount which will allow a sufficient amount of oleophilic colloid and inert particulate material to be dispersed in water but less than that amount which will reduce the efficiency of the gelling action when the aqueous mixture containing the oleophilic colloid and inert particulate material is mixed with an oleaginous liquid. The specific amount of any selected dispersing agent to be employed may readily be determined by straightforward tests wherein various amounts of dispersing agent and oleophilic colloids are mixed together to form a pumpable slurry which will gel when mixed with an oleaginous liquid. The amount of oleophilic colloid which should be present in the aqueous mixture is less than that amount which will produce a slurry that is too viscous to pump and at least equal to that amount which will produce upon mixture with an oleaginous liquid a gel of sufficient strength to mitigate the loss of circulation. The amount of inert particulate material which should be present in the aqueous mixture is that amount wherein the ratios of inert particulate material to oleophilic colloid are withinthe range of weight percent inert particulate material to 30 weight percent oleophilic colloid and 25 weight percent of inert particulate material to weight percent oleophilic colloid.

A typical formulation for use in controlling lost circulation is obtained by forming a slurry comprised of the following materials in approximately the concentrations specified: water 301 grams; oleophilic colloid of the type available under the trade name of Geltone 200 grams; barite 200 grams; ferrochrome lignosulfonate 2.9 grams; and caustic soda l.6 grams. Such a composition yields a slurry having a density of about 1 1.8 pounds per gallon, and which slurry has a Farm apparent viscosity of about 70 centipoises (cps).

Ideally, the drill bit will be located adjacent the lost circulation zone so that as the aqueous mixture and oleaginous liquid are mixed and a gel is formed it is displaced immediately into the lost circulation zone where the gelling action continues until a stiff plug is formed, thus sealing the lost circulation zone. However, in many cases, the precise depth of the lost circulation zone will be unknown. In such cases it is important to maintain circulation of the drilling fluid in order to ensure that the plug that is formed upon mixing of the oleaginous liquid with the aqueous mixture of a dispersing agent, inert particulate materials, and a water dispersible oleophilic colloid is forced into the lost circulation zone. Due to its thixotropic character, this plug will tend to stiffen after it is displaced into the formation where it is subject to lower shear stresses than while circulating within the well.

It is contemplated that in most cases, adequate contact between the aqueous mixture of the dispersing agent, oleophilic colloid, and inert particulate material and the oleaginous liquid can be obtained simply by passing the mixture through the outlet ports of the drill bit into the well. This is particularly true when employing an aqueous mixture containing an inert particulate material therein, inasmuch as less mixing with an oleaginous liquid is required for the formation of a suitable gel. However, if more intimate mixing is desired, the drill string may be withdrawn from the well and equipped with a mixing sub such as that described in US. Pat. No. 2,800,964. Thereafter, the drill string may be reinserted within the well and the aqueous mixture introduced as described above.

If desired, a suitable oleaginous liquid, such as the oil-base drilling fluid used during normal operations, may be pumped down the well annulus in conjunction with circulation of the aqueous mixture through the drill string. These steps should be correlated such that fluid is being pumped into the annulus as the aqueous mixture is displaced from the drill string into the well. This will further promote mixing of the aqueous mixture and the oleaginous liquid and will provide a continuous supply of oleaginous liquid-to the mixing zone. Desirable yield strengths are exhibited by gels formed by mixing the oleaginous liquid and aqueous mixture of a dispersing agent, inert particulate material, and oleophilic colloid within the range of one volume of oleaginous liquid to three volumes of aqueous mixture and three volumes of oleaginous liquid to one volume of aqueous mixture. Preferably about one volume of oleaginous liquid is mixed with one volume of aqueous mixture containing a dispersing agent, inert particulate material, and oleophilic colloid to form a gel having a maximum yield strength.

By introducing the aqueous mixture of dispersing agent and oleophilic colloid into the drill string as a discrete slug, the possibility of significant contact between the oleophilic colloid and the oil-base drilling fluid within the drill string is substantially reduced. Thus, the tendency of the oleophilic colloid to go into an oleaginous dispersion within the drill string is reduced with the result that there is little chance of forming a stiff gel within the drill string.

In order to further ensure against the oleophilic colloid within the aqueous mixture contacting the oil-base drilling fluid within the drill string, the aqueous mixture may be preceded with a liquid buffer system comprising an aqueous liquid such as fresh water, brine, or if desired, an aqueous-base drilling fluid having hydrophilic clays dispersed therein. The buffer system normally will comprise a relatively small amount, e.g., on the order of one-half to five barrels, depending upon the depth to the end of the drill string which typically may vary from about 1,000 to 25,000 feet. A large amount of liquid buffer system normally should be avoided in order to ensure that contact of the aqueous mixture of dispersing agent, oleophilic colloid, and inert particulate material, and the oil-base drilling fluid will take place after the aqueous mixture enters the well from the drill string. The aqueous buffer liquid should, of course, be substantially free of oleophilic colloids. A second buffer system identical with the firstinjected buffer system may be injected into the drill string immediately following the aqueous mixture of dispersing agent, oleophilic colloid, and inert particu late materials. This second buffer system reducesthe possibility of contact within the drill string between the aqueous mixture of oleophilic colloid and the subsequently introduced oil-base drilling fluid.

Results of laboratory tests carried out in accordance with this invention are shown in the drawing and following table. The drawing is a graph wherein the volume percent of oleaginous liquid (oil-phase mud) to aqueous mixture of oleophilic colloid employed in forming a gel is representedby the x-axis and the yield strength in pounds per square inch of the gel so formed is plotted as the y-axis. Also shown along the x-axis is a scale which indicates the volume ratio of oleaginous liquid to aqueous mixture used in forming a gel. The oleophilic colloid used in carrying out these experiments was purchased under the trade name of Geltone and the inert particulate material was barite. Curve A shows that a mixture of about 1.67 volumes of oleaginous liquid with 1.0 volume of aqueous mixture (no barite) results in the formation of a gel having a yield strength of about 5 psi, whereas Curve B shows that a mixture of about one volume: each of oleaginous liquid and aqueous mixture (containing about 50 percent Geltone and 50 percent barite) results in the formation of a gel having a yield strength of about 5 psi. Curve C shows that mixing one volume of an aqueous mixture containing 37.5 percent Geltone and 62.5 percent barite with one volume of an oleaginous liquid results in the formation of a gel having a yield strength of only slightly less than 5 psi and still greater than that which would have resulted if the aqueous mixture had contained no barite (Curve A). Thus, this data shows that adding inert particulate material to the aqueous mixture lessens the amount of oleaginous liquid required to be mixed with the aqueous mixture to form a gel having maximum yield strength and, that it is preferred to mix approximately equal volumes of oleaginous liquid and aqueous mixture in so forming a gel. Further, this data shows that preferably the inert particulate material (in particular, barite) and water dispersible oleophilic colloid shouldbe present in the aqueous mixture in an amount within the range of weight percent inert particulate material to 30 weight percent oleophilic colloid and 25 weight percent inert particulate material to weight percent oleophilic colloid and still more preferably in an amount of about 50 weight percent inert particulate material to 50 weight percent oleophilic colloid.

TABLE Water Oleophilic Bentonite (WOB) Slurry (omposition and Properties Density Fann Apparent Composition of Weight of weight of 1. In the drilling of a well, the method of alleviating fluid loss into a subterranean formation penetrated by said well comprising:

introducing into said well an aqueous mixture of a dispersing agent, an inert particulate material, and a water dispersible oleophilic colloid which acts as an oleaginous gelling agent;

circulating said aqueous mixture down said well and into the vicinity of said formation; and

mixing said aqueous mixture with an oleaginous liquid whereby said oleophilic colloid is dispersed in said oleaginous liquid and forms a gel.

2. The method of claim 1 wherein said inert particulate material is selected from the group consisting of barite, galena, calcium carbonate, and silica.

3. The method of claim 2 wherein said dispersing agent is selected from the group consisting of lignites, lignosulfonates, tannins, and complex phosphates.

4. The method of claim 3 wherein said oleophilic colloid is a normally water swellable clay which has been treated to render it oleophilic.

5. The method of claim 1 wherein said inert particulate material is barite.

6. The method of claim 5 wherein said barite and water dispersible oleophilic colloid are present in said aqueous mixture in an amount within the range of weight percent barite to 30 weight percent oleophilic colloid and 25 weight percent barite to weight percent oleophilic colloid.

' 7. The method of claim 6 wherein said barite and water dispersible oleophilic colloid are present in about equal weights in said aqueous mixture.

8. The method of claim 1 wherein said aqueous mixture and said oleaginous liquid are mixed within the range of one volume of oleaginous liquid to three volumes of aqueous mixture and three volumes of oleaginous liquid to one volume of aqueous mixture.

9. The method of claim 8 wherein about one volume of said aqueous mixture is mixed with about one volume of said oleaginous liquid.

Patent Citations
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3987855 *Nov 25, 1974Oct 26, 1976Mobil Oil CorporationLost circulation control
US4173999 *Sep 26, 1977Nov 13, 1979Mobil Oil CorporationTechnique for controlling lost circulation employing improved soft plug
US4445576 *May 24, 1982May 1, 1984Exxon Research And Engineering Co.Water in oil emulsions for plugging
US4848487 *Jun 30, 1988Jul 18, 1989Mobil Oil CorporationMethod for minimizing mud solids invasion of core samples obtained during subsurface coring
US4964465 *Nov 6, 1989Oct 23, 1990Texaco Inc.Method employing liquidized sand for controlling lost circulation of drilling fluids
US5147852 *Sep 30, 1991Sep 15, 1992Venture Innovations, Inc.Well working fluid additive containing cellulose material having a specified particle size distribution for use in wells in a permeable formation
US5913364 *Mar 14, 1997Jun 22, 1999Halliburton Energy Services, Inc.Methods of sealing subterranean zones
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US6167967Feb 12, 1999Jan 2, 2001Halliburton Energy Services, Inc.Methods of sealing subterranean zones
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CN102031942BNov 30, 2010Aug 28, 2013中国石油集团川庆钻探工程有限公司On-site construction process of water base barite liquid plugging agent with heat sensitive characteristic
Classifications
U.S. Classification175/72, 166/294
International ClassificationE21B21/00, C09K8/92
Cooperative ClassificationC09K8/92, E21B21/003
European ClassificationC09K8/92, E21B21/00M