US2894584A

US2894584A - Well completion

Info

Publication number: US2894584A
Application number: US630266A
Authority: US
Inventors: Bertie F Birdwell; Gerald G Priest; Bryan E Morgan
Original assignee: Jersey Production Research Co
Current assignee: Jersey Production Research Co
Priority date: 1956-12-24
Filing date: 1956-12-24
Publication date: 1959-07-14
Anticipated expiration: 1976-07-14

Description

B. F. BIRDwELl. TAL 2,894,584

July 14, 1959 WELL COMPLETION 2 sheets-*sheet 1 Fiied Dec. 24, 1956 NNI..

Illfll l||||| om @S 92.5.1@

"' |||||||I II Il lilil iIII IIIIIII IiIiIiliI IIIIIIIIIIIIIIII IIIIIIIIIIIII IIIIIIII III iin IIIIIIIIIIIIIIIIIII Il IIIIII ||||I|||||||| IIIIIII GERALD G. PRIEST. BRYAN E. MORGAN.

I I l .r III III IIIII IIIII INVENToRs.

lATT RNE TII III III il I II 1. I III I III .I :I'II I II'IIiIm IIIIIIIIII IIIIIIIlIIIIIIIIIwww I 'IIIIIIIIIIII'I I 2 u. Il I1 Il B'E'RTIEr- F. BIRDWELL July 14, 1959 B. F. BlRDwELL ErAL WELL COMPLETION 2 sheets-sheet 2 Filed Dec. 24. 1956 o "I TMll 2 Il.

kvk..

I I ,il I

L. S ..L RTN-t mSAW Nmso ERRR VPOM. N .M IG .E DEE LNI AAM RY ERE GBB V. B

Mgqg

.VAT

United States Patent O f WELL CGMPLETION Bertie F. Birdwell, Austin, and Gerald G. Priest and lBryan E. Morgan, Houston, Tex., assgnors, by mesne assignments, to Jersey Production 'Research Company, Tulsa, Okla., a corporation of Delaware Application December 24, 1956, Serial No. 630,266 4 Claims. (Cl. -166--42)y The present invention is directed to a method for completing oil and gas wells. More particularly, the invention is directed to a method for completing oil and gas Wells in which a drilling uid or mud is used to control the well. In its more particular aspects, the invention is directed to a method for completing an oil or gas well in which a column of drilling uid is maintained in a casing to control the well.

Current practice when completing wells, such as oil and gas wells, through perforated casings is to have drilling fluids, such as mud, salt Water, water, or oil, in the well casing and to perforate the casing with bullet, shaped charge, chemical or punch-type perforators. When the pressure of a formation traversed by the well exceeds the hydrostatic pressure of a column of oil or water at the Vcompletion depth, it is customary to use weighted salt water or normal drilling mud having a density great enough to exceed formation pressure in order to control the well while perforating the casing and performing other routine completion operations. In the case of a well filled with drilling mud when the casing is perforated, the drilling mud flows into the perforations because of the pressure differential existing between the interior of the casing and the formation. The perforations are thereby partially or completely plugged with mud and this plugging is aggravated by the heat and instantaneous pressure evolved by the propellant powder in the case of bullet perforators and the high explosive in the case of the jet or shaped charge perforators. Where chemical or punchtype perforators are employed, it is'not uncommon for the drilling mud to lose water rapidly to the formation resulting in the drilling mud becoming dehydrated and forming plugs. Data are available which indicate that such plugs whether formed by dehydration of the drilling mud by heat, and/ or pressure or by loss of Water to the formation are diflicult to remove by subsequent flow from the formation into the well bore and that the productivity of a perforated interval in a producing formation is significantly reduced. Field completion attempts of wells indicate that such plugging of the perforations may cause formations to be tested as being non-productive and thereby condemned when actually the formation may contain economically producible oil or gas. Thus it is clear that the problem of plugging of perforations is serious and is a source of expense in well completions and of erroneous conclusions in exploratory work which may cause major hydrocarbon reserves to remain undiscovered.

Another problem which exists in perforating wells is that it is necessary to provide control of the well during perforations. This is accordingly accomplished by maintaining a hydrostatic column which exerts a pressure greater than the formation pressure exposed when the casing is perforated. However, to provide a column having a sufficient hydrostatic pressure, it is necessary to add 2,894,584 Patented July 14, 1959 HCC weighting agents such as barites, sand, and other solid heaI/y materials to the fluid column maintained in the We As it has become necessary to drill deeper and deeper wells in search for petroleum-producing formations, the temperatures encountered in these deeper wells have increased to an extent that difficulties have been encountered. For example, the fluids which heretofore have been used in wells become unstable and tend to lose their properties at the high temperatures of the order of 200 to 250 F., which may be encountered. For example, emulsions which may be used as completion fluids may become unstable and resolve intov their component parts. It is, therefore, desirable to provide a heat-stable emulsion which will maintain and preserve its characteristics at high temperatures encountered in deep Wells.

The high temperatures may be encountered in Wells ranging from 10,000 to 25,000' in depth with a usual operation being performed at from about 14,000' to about 18,000'. High well temperatures may be encountered at lesser depths, for example, from 6,000' to about 14,000', depending on the area where the operations are being conducted.

In accordance with the present invention, the plugging of perforations in well casing in which a column of drilling uid or mud is maintained to control the well is eliminated by providing in the well casing adjacent the producing formation a body of a thermally stable emulsion, which effectively removes, displaces, or excludes the drilling fluid from that zone and allows perforations to be made in the casing without damaging the formation by contamination.

The present invention may, therefore, be briefly described as involving the placement of an emulsion of an oily and aqueous medium containing a soluble weighting agent dissolved in one of the components of the emulsion, the emulsion being characterized by having a low fluid loss into the formation, having the property of displacing or excluding drilling uid from the region of the casing to be perforated or from the subsurface earth interval to be treated. The particular emulsion is a heat-stable emulsion in which an emulsifying agent selected from the alkali metal salts of purified lignin sulfonic acids containing from about 3% to about 33% by Weight of sulfonate groups and from the ammonium and alkali metal salts of lignin sulfonic acids containing from about 38% to about 57% lignin sulfonic acid groups is employed.

Another problem exists in well recompletion and servicing operations in that, heretofore, existing perforations in the wall of a well bore or a well casing penetrating into hydnocarbon-productive formations frequently were contaminated or damaged by conventional well fluids or Well completion uids while an operation such as treating, sealing or cementing, perforating, fracturing, and the like was carried on or performed elsewhere in the well such as in a vertically spaced part zo-ne. Heretofore,

there had been no satisfactory way of preventing damage to the existing perforated formation.

In accordance with the present invention, it has been found that such damage may be eliminated by placing a body of an emulsion having a low fluid loss in contact with the perforations or perforated formation while conducting or performing operations elsewhere in the well. Hence, the present invention also contemplates the feature of protecting or blanketing selected intervals or zones in the well While reconrpletion, servicing, sealing, or treating operations are conducted in the well either in a zone or intervalk vertically removed from the emulsionprotected zone or in the emulsion-protected zone.

The emulsion employed in the practice of the present invention is used in the sense of the emulsions described in Sutheimns Introduction to Emuls1ons, Chemical Publishing Company, Inc., Brooklyn, NewYork, 1947,

- page l, where an emulsion is described as followsz.

Emulsions are intimate mixtures .of two immiscible liquids, one of them being dispersed in the other 1n the form. of iine droplets. I

The emulsion of the present invention contains, dissolved in one of the components of the emulsion, a welghting agent Whichis soluble in one of the components.

The weighting agent may be soluble either in the aqueous phase or the oily phase ofthe emulsion. For example,

Weighting agent.

puried uniform pine wood lignin is obtained as a byvproduct of pulping wood chips with a caustic solution to separate and recover the pure lignin, which is then sulthe by-products of wood pulping by the sulteprocess the water phase may contain a water-soluble, inorganic f The oily phase may suitably be a hydrocarbon, such n as crude petroleum and fractions thereof, such as gasoline, kerosene, gas oil, dieseloil, andthe like. Other carbons, such as carbon tetrachloride, and the like, ma form all or part of the oily phase.

The emulsion may either be heavier or lighter than the drilling fluid and suitably may have a density in pounds per gallon in the range fromabout 7 to about 18 pounds per gallon. The emulsion where lighter than the drilling fluid may have a suitable viscosity sumcient to displace the drilling mud and to prevent displacement thereof by the drilling mud. For example, the viscosity of the emulsion replacing the drilling mud may range from about l() to about4000 centipoises at 60 F.

The emulsion of the present invention is suitably formed by employing an emulisfying agent of the type known as the Polyfons and the Orzans. The Polyfons are a series of surface-active-chemicals formed from. purified lignin.

- These surface-active agents may be the alkali metal salts such as sodium, potassium, and lithium of lignin sulfonic acid. The commerciallyk available Polyfons are sodium lignosulfonates and may be ldentied as follows:

Grades Percent Sodium Sullonate Groups 2.9 5. s 1c. s 19. 7 26.9 324 s hydrocarbonaceous materials `or derivatives of hydro-k my using an ammonia base. The Orzans contain from. about 20% to about 40% by weight `of ash land contain varying amounts of sugars. In this process Wood chips consisting of about 90% western `hemlock and 10% white r are placed into a digester containing ammonium bisulfite and excess sulfur dioxide. The mixturek is cooked for about 8 hours at a temperature of about 290-300 F., while a pressure of about 70 to 80 pounds per square inch is maintained within the digester. After the cooking period, the mixture is filtered tokseparate the wood pulp from` i the bisulfte liquor.

Orzan A `is obtainedby concentrating the liquor by evaporation to about solids, and then spray-drying the concentrated liquor. Orzan A, therefore, is an unaltered by-product of the pulping process containing ammonium lignin sulfonate and wood sugars.

- Orzan Sis a sodium salt of lignin sulfonic acid and is obtained by adjusting the concentrated ammonium bisulfite liquor to pH 7.0-7.5 with sodium hydroxide. At a pH of 7.0-7.5 the excess ammonia is driven off and the concentrated liquor isspray-dried to obtain a free flowing powder.

The Orzans AHO, AHI, AH2, and AH3 are made by partiallypolynierizing thelignin sulfonate units present kin Orzan A, increasing the average molecularweight from about 10,000 to about 40,000. The member havingthe highest molecular weight is Orzan AH3. 40

A complete description of methods used in the isolation of lignins and the various lignin sulfonates` by the kraft, soda and sulite processes will be found in the work by Ott, Spurlin, and Graflin, entitled Cellulose and Cellulose Derivatives, lnterscience Publishers, Inc., New York, second edition, part 2, pages 524 to 545.

The by-products from this process are ammonium lignin sulfonates and sugars, `occurring in a `fixed proportion. The Orzans available in the industry and emloyed in the present invention have a composition as shown in the following table:

TABLE I A comparison of the chemical composition of the various Orzans Constituent Analysis-Percent Total Solids Trade Dess Type of Compound ignation Lignin Reducing Available Sulfated Sulfonic Sugar Ammonia Sulfate Ash Ash Acids Orzan-A. Ammonium Lignin Sulfonatc 16. 7 2. 8 1.6 2.0 21. l Orzan-S Sodium Lignin Sulfonatc 40 10. 6 0.2 1.69 23.0 18. 5 Orzan-AI-l0 Polymcrized Ammonium Lignin 55. 2 12. 9 2. 58 1. 52 6. 5 21. 3

Sulonatc (Orzan A). Oman-AHL do 55. 5 10. 7 2. 58 l 55 S. 3 21. 4 OrZan-AI-I2 .d0 55. 8 9. 5 2. G5 l 57 8.3 22. 2 Orzan-AH3 .do 56. 7 9. 0 2. i5 l 60 7. 7 22. 4 Orzan-SS Sodium Lignin Sulfonatc 38. 4 0.0 0.00 41.3

The extent of sulfonation of the Polyfons is controlled to form the intermediate components having the degree To forml the Polyfons, ated with them. By processing the ammonium lignin of sulfcnation indicated before.

Thus, it can be seen that the Orzans vary in their degree of sulfonation` and lthe amount of sugars associ- In a word, the Polyfons are the alkali sulfonates with sodium" hydroxide, it is possible to forni the alkali metal salt which is substantially free of sugar. There are many water-soluble, linorganic Weighting agents which find use in the practice of the present in- TABLE Il Water soluble inorganic compounds suitable as weighting agents Specific Name Formula Gravity A1Bra 01 A1013 44 A113 98 NHrBr 33 NHA 51 NHrNOa 72 (NHmHPOl 62 SbCla 14 SbFa 38 B8,(C2H3Oz)z 47 78 Cadmium iod1de Cadmium nitrate tetrahydr Cadmium sulfate heptahydrate. Calcium bromate nionohydrate. Calcium bromide.

Cupric bromate Oupric bromide Ferrous brom' e. Ferrous chlorid Lithium iodide Magnesium bromid Magnesium iodide. Manganese bromide Manganese chloride tetrahydrat iodide Zinc sulfate CdBlq 2 Cd(C10a)i 3 CdCln 05 C6112 67 CCKNOQMAHQO 45 CdS 04.715120 48 CBL(BIO3)2 2H2O 33 CaBrz 35 Cach C212 96 CMNOSM 35 C11(Br03)2.6H3O 58 CuBra 2- 8 CuClz 3- 05 C11(NO3)2.6H20 2. 07 neon 2- 81 Fe(N0a)a.6H2O 1. 68 Fez(SO4)a.9H2O 2. 1 FeBri 4. 64 FeCla 2. 70 Pb(C3H3O2)z.3HgO 2. 55 Pb(C10s)i.HzO 4. 04 PMN 03). 4. 53 LiBr 3. 46 LiI 4. 06 MgBrz 8. 72 MgIn 4. MnBrg 4. 39 MnCliAHzO 2- 01 Mula 5- 01 NiBri 4- 64 Ni(NOs)i.6H2O 2 05 KCzHaOn 1- 8 15,00, 2. 2e KF 2. 48 KI 3. 13 KNOz 1 92 K3PO4 2. 56 NEHSOA 2. 74 NaBr 3. 20 NaClOx 2. 49 NaCl 2. 16 NaOH k2. 13 N aI 3. 67 NaNO; 2. 26 aNOz 2. 17 NaHaP 04.2H20 1. 91 ZnBra 2, 56 ZnClg 2. 91 ZIlIn 4. 66 ZI\(NO3)2.6H2O 2. 05 ZI1S04 3. 74

There are many oil-soluble organic Weighting agents which are soluble in the oily phase of the emulsion ernployed in the practice of the present invention. The oilsoluble organic yweighting agents suitably have a specific gravity in the range Ifrom about 1.2 to about 4. vThese organic weighting agents are illustrated in the following table:

TABLE III Organic weighting agents Name Formula Specific Gravity m-Aminobenzoic acid. NHgCHrCO 0H 1. 511 CH3(CH2)3CH2B1' 1. 218 (CHmOH (CHmBr. 1. 22 (CHQZC (Br) 02H5- 1. 216 C 1. 26 1. 51 1. 515 1. 507 1. 471 1. 52A 1. 25 1. 438 1. 54 CiH101N 1. 66 CH5CHIBI'2 1 51 Benzene hexa chloride.

Benzoic acid 89 66 Benzanilide- 1. 31 Benzainide.. 1. 34 Benzylbromde 1. 44 Beuzylodide.- 1. 73 Bromal BraCCHO 2. 665 p-Bromoacetanilide.. BrC5H4NHCOCHa- 1.77 Bromoacetophenone CaH5COCH2Br 1.65 p-Bromoaniline. 1. Bromobenzene- 1. 495 Bromoiodobeuzene 2. 257 Bromoiodoethane (1,1) 2. 45 1,2Bromoiodoetliane 2. 52 Bromoiodomethane 2. 96 Bromonaphthalene 1. 605 Bromosuccinic acid 2 07 Bromatoluene 1. 422 Broniotoluene gm) 1.41 Bromotoluene p) 1.39 Brnmnfnrm C 2. 89 Butyliodide 1. 617 Chlorobromobenzene 1. 63 Chlorodibroiiioethane 2. 3 Chlorodiiodomethane CICH 3.17 Chlorodiiodobenzene-- 1. Chloroiodoethane 2.1 Chiorotetrabromoethane. 3. 4 Chlorotribromoethane..- 2. 6 Chlorotribromomethane.-. 2. 7 Pentabroinoethane 3. 4 Tetrabroinoethaiie (sym) 2. 96 Iodoform-. 4. 0 Ethylene Dibromide 2. 17 Carbon Tetrachloride CO1 1.595 Dichlorobromomethane. 2. 01 Dichlorodibromoethane ClzCHCHBrL.-- 2.39 Dichlorotribromoethane.-- Br2CClCHBrCL. 2.62 Dilnorobroinoethane F2CHCH2Br 1.82 Difluorodibromoethane BrzCHCHFg 2.31 Peruoro-n-heptane CvFw 1.73 Prflnorotrimethylpen- CgFrg 1.80

ane. Peruoro(O-dimethy1 CBFN 1. 86

cyclohexane) Tritluoroethanol Peruo- (n-CrFmO 1.71

rodibutylether. Periiuorodiamylether (i1-05111020 1.78 Perilriliorodimethyhexyla- CaFnN(CF3)2 1. 82

m e. Pert'luorodipropylethyla- (ri-CaF-MNCRFL 1. 79

mine. Perfluorotripropylamine... (n-CaFgN 1. 82 Peruorotetraethylethy- (CzFmNC FgCFgN(C;F5) 1. 86

lene diamine. Pertluorotributylamina... (n-C4F9)3N 1. 86 Periluorotrihexylamine.. nF1s)sN.. 1.93 Trichloroethylene ClCHCCl2 1.47 Periuorodihexylether (ii-05111920 1.81

The emulsion employed 1n the present invention will suitably consist essentially of from about 5% to about 95% by Volume of Water with a preferred range from about 20% to about 80% by volume of water, from a'bout 5% to about 95% of oil with a preferred range from about 20% to 8O volume percent of oil, and an emfulsifying agent of the type illustrated in an amount in the range from about 0.5 to about grams per 100 ml. of the external phase of the emulsion. j

The weight percent of the inorganic weighting agent or salt dissolved in the aqueous or water phase will range from 1% up to about saturation, Iwhile the weight percent of organic compound or weighting agent dissolved in the oil phase will range from .1% up to about saturation.

It is contemplated that weighting agents may be present in both the oily and aqueous phases of the emulsions. However, conditions may exist where the weighting agent is present in only one phase of the emulsion.

The presentl invention will be further illustrated by reference to the drawing, in which:

Figs. l to 6, inclusive, represent a stepwise operation in accordance with the invention; and

Figs. 7 to 11, inclusive, represent another mode of practicing lthe invention.

Referring to the drawing in which identical numerals will be employed to designate identical parts, and particularly to Figs. 1 to 6, numeral 11 designates a well drilled from the earths surface, not shown, to penetrate a plurality of

subsurface earth intervals

12, 13 and 14. The well is lined `with a well casing 15, which may ybe cemented in place with cement 16. The well casing 15 and the cement 16 may be perforated in the earth interval 14 to form perforations 17 to allow communication between the formation or zone 14 and the interior of the casing 15 to produce, for example, oil, gas and other desirable earth minerals. A tubing 18 may be placed in the casing 15 with its lower end 19 immediately above the plurality of subsurface earth intervals, sands, zones, strata, horizons, or

formations

12, 13 and 14. It may be assumed for purposes of this description that the

intervals

12 and 14 may be productive of hydrocarbons, while the interval 13 may be non-productive. In the showing of Fig. 1 the well has been drilled and contains drilling fluid or other fluid which may be used for control, such as salt water indicated by the numeral 20.

In Fig. 2, it is desirable to perform an operation in the well, but yet itis also desirable to protect the perforations 17 against damage. For example, if mud were allowed to come into contact with the perforations 17, damage to the formation or interval 14 might occur which could effectively prevent production of hydrocarbons from the zone 14. It may be assumed for purposes of this description that it is desirable to perform a cementing operation to prevent communication from back of the casing with the perforations 17 from the interval either 12 or 13. To this end a tubing extension member, such as 21, may be lowered on a suitable wire line, not shown, and located adjacent the lower end 19 of the-tubing 18. The tubing extension 21 may suitably be landed, anchored, or supported in the lower end 19 in asuitable landing nipple or other supporting means, such as 22. By anchoring and sealing the extension member 21 in the lower end 19 of the tubing 18, the effective. length of the tubing 18 is increased. A body of emulsion, such as 23, then may be placed adjacent the perforations 17 displacing the fluid 20 up the annulus A between the tubing 18 land the casing 15. It will be seen by placing an emulsion of the type indicated before adjacent the perforations 17, the perforations 17 are effectively blanketed and protected. T here after, the tubing extension 21 is removed from the tubing 18 by attaching a wire line, not shown, to -the fishing head 24 and retrieving same from the tubing. A-s shown in Fig. 3, a gun perforator 25, which may be of the Shaped charge or bullet type, is lowered on the wire line `26 to perforate the interval 12. The perforator 25 may be one of the chemical or mechanical types, but preferably is a bullet gun or a shape charge gun. The

perforator is then operated or fired to form perforations 27 in the casing 15, cement 16, and to penetrate the interval 12. Thereafter, the perforator 25 is retrieved from the tubing 18 by wire line 26and a body of cement 28 is then placed adjacent the perforations 27A and squeezed outwardly to fill the perforations 27 and any channels between the wall of the wellbore 11 and the casing 15 to prevent communication with the perforations` 17. After the cement has been squeezed by imposing pressure on thebody 28, the excess cement may be removed by employing a tubing extension member, such as 21, and to remove the excess cement which may be of a modified type having a low fluid loss and which remains fluid for a suicient length of -time to allow circulation of the cement out. A :suitable modified cement is described in the patent to Salathiel, U.S. Patent No. 2,582,459. After the fluid cement has been removed, the perforations 27 are effectively sealed, as indicated, and it becomes desirable to remove the body of emulsion 23. This is also accomplished by placing a tubular extension member, such as 21a, in the landing nipple 22 and circulating the emulsion out as indicated by the arrows shown in Fig. 5 using a suitable circulating fluid. Thereafter on removal of the emulsion, pro duction may again be had from the interval 14, which has been protected during the operations from damage by contact with fluids in the well. This flow is shown las indicated by the arrows. The emulsion may be flowed outwardly without the use of a tubing extension by suitlably swabbing the well.

Referring now to Figs. 7 to ll, 11 designates a well drilled from the earths surface, not shown, to penetrate a plurality of

subsurface earth intervals

12, 13 and 14. The well is lined with a Iwell casing 15, which is cemented in place with cement 16. The 'well casing 15 and the cement 16 has been perforated previously in the earth interval 14 to form perforations 17 to allow communication between the formation or zone 14 and the interior of the casing 15 lto produce, for example, oil, gas and other desirable earth minerals. A tubing 18 is in the casing 15 with its lower end 19 immediately 'above the perforations 17. This condition is illustrated i in Fig. 7.

For purposes of explanation, it is desirable to protect these perforations 17 opposite the formation 14 while new perforations are to be made in formation 12. Salt water 20 is pumped into tubing 18 until the 'annulus 30 is either filled with salt water or` lthe hydrostatic column becomes balanced with the formation pressure in the formation 14. This step of the operation is illustrated in Fig. 8.

A predetermined quantity of emulsion, `according to this invention, is pumped through tubing 18 until the emulsion yreaches the lower end of the tubing 19. At this point, the casing side is closed at the surface and the emulsion in tubing 18 is displaced by' pumping salt water into tubing 18 until the emulsion 23 contacts the face of formation 14 through perforations 17. Further displacement of the emulsion is made lto cover

formations

12, 13 and 14, :as illustrated in Fig. 9.

Tubing 18 is withdrawn from the -well and perforator 25 is lowered into the well opposite formation 12 and tired to make perforations 31, as illustrated in Fig. 10.

The perforator is removed from the well fand tubing 18 with packer 32 is lowered into the well. The packer 32 is set as shown in Fig. 11 to accomplish dual completion of the well. Hydrocarbon production from formation 12 through perforations 31 is directed into the annulus between the tubing 18 and the casing 15 Iwhile production of hydrocarbons from formation 14 through perforations 17 occurs through the inside of tubing 18.

In order to illustrate the invention further, la number of compositions were prepared in `accordance with `the present invention. These compositions `are set out in the following table:

TABLE IV Composition and properties of emulsions containing calcium chloride and different solids Composition of Emulsion Composition of Aqueous Phase Oil Phase EmUlSier Sample No. External Aqueous Phasepf Phase, Solids 'Fmnlsmn C9013, g./1001Il1. Percent Wt., Identity Vol., Identity External Identity g./1100 Percent Percent Phase 60 2.0 40 Diesel 0i1 40 Polyon 0 2.0 60 d 2.0 40 do 40 Polyl'on R 2.0 60 d 2.0 40 PolyfonT 2.0 60 do 2.0 PolyionE 2.0 60 d0 2.0 d0- 3.0 e do- 2.o 1-0 60 d 2.0 0-5 60 1.0 2.0 60 0.5 2.0 60 d0 2.0 2.0

Polyvinyl alcohol- 1. 0 60 Pozrnix-MO 2.0 Polyon H 2.0

Polyvnyl alcohoL.. 0.5 Ox- 8 1.0A 60 Pozmix-MO 2.0 Polyfon H 2.0 Triton XGL... 1. 0 60 do 2.0 PolyfonH 2.0 Pluronic F68 1. 0 60 Pozmix 2.0 Polyfon H 2.0 60 IndulinA 2.0 40 2.0 60 Calcium Hydroxide- 2.0 40 2-0 60 d0 1.0 40 2.0 so do- 0.5 40 2-0 so geioiay 2.o 4o o 5o do 2.o 40 do 2.0

Polyvinyl alcohoL-. 0. 5 do 1.o do 2-0 0.5 40 do 20 0.25 40 do 2.0 0,25 40 do 1.0 0.25 40 do 05 4o do 2.0 4o do 2-0 40 do 2-0 40 do L0 40 do 1-0 4o do 2.0 40 2.0

40 2.0 e 40 1.0 2.0 40 2.0 2.0 40 2.0 2.0 40 2.0 2.0 40 2.0 2.0 40 3.0 2.0 40 1.0 -do 2.0 40 0.5 60 Calcium Carbonate. 1.0 40 2.0 60 Zeogel Clay 2.0 40 2.0 60 do 2.0 40 do 60 Aquagel Clay 2.0 40 do 2-0 eo do 2.0 4o d5 2g l. 60 Xact Clay 2,0 40 do 20 so do 2.0 40 do 2-(l) 1. o0 4o d0 2.0

' TABLE IV-Continued on following page.

It may be seen from an examination of the data in the immediately preceding table that these emulsions have very low iluid losses at room temperatures and after aging at 250 F. By vway of explanation, emulsions having a fluid loss above 40 ml. in 30 minutes at room temperature after the sample has been aged for 24 hours at 250 F., or those having a fluid loss above 80 ml. in 30 minutes at a ltest temperature of 250 F., may be considered unsatisfactory as well completion fluids under some conditions, since they may not remain in place to protect the exposed face of -a subsurface interval.

It is to be particularly noted that the Polyfonand Oman-containing emulsions are particularly suitable after both atmospheric and elevated temperature aging and, therefore, are useful as completion and servicing iluids in wells of normal and elevated temperatures.

In the composition of the present invention, it is desirable vto stabilize the emulsion, and this may suitably be done by employing suitable stabilizing agents which may be of dispersible solid material and which may be identified as Pozmix, Pozmix 140, line, Xact clay. Other stabilizing `agents such as polyvinyl alcohol in admixture with the Pozmix and the lime, Zeogel clay and calcium hydroxide may also be used. These several dispersible solids are particularly desirable at the elevated temperatures encountered in deep Wells and may be used in amounts from about 0.5 gram to about 3.0 grams per 100 m1. of the aqueous phase. Y

The compositions of the present invention are quite useful as perforating fluids and well completion iluids and have the property of protecting the formation and preventing damage of the formation by eliminating contact with contaminating bodies. For example, when the composition of the present invention is used as a perforation uid, the permeability of the formation is not damaged and flow is readily obtained therefrom. Furthermore, the composition of the present invention allows formations -to be protected While conducting operations in the well displaced from the protected formation.

While the invention specifically contemplates its use and application to perforating, servicing, and completion operations in cased wells, it is understood that these applications and uses are given by way of illustration and not by way of limitation. Thus, the present invention TABLE IV-Continued Composition and properties of emulsions containing calcium' chloride and different solids-Continued Properties of Emulsion API Fluid Loss Sample No.

Density, At Room Temperature At Elevated Tempera- Iii/gal.` ture b Before Aging, After Aging,n F. mlt/O IDL/30 min. IDL/30 min. mm.

15 9. 6 11.0 13.8 16-- 9.6 11.0-.- 16. 17-- 9. 6 l2.2 18. 18- 9.6 9.8... ll. 19. 9. 6 9.2. 16. 20- 9.6 17.0. 26. 21. 9. 6 21.0- 30. 22- 9.6 14.8 23. 9.6 15.0 24- 9. 6 16.8 25- 9.6 5.4- 26. 9. 6 8.2. 27, 9. 6 10.2-- 28- e. o 17.0.- 29- 9. o 25.0-- 30- 9. 6 12.4. 31- 9. 6 12.0-. 32- 9,6 12.0-. 33- 9.6 9.0... 2in41n1r1- 34- 9. 6 23.0...- 25 in 15 min, 35- 9. 6 25 in 10 mm. 25 in 10 min.. 3G- 9.o 25111 12 man 25 in 1 min- 37- 9. 6 16.8 38. 9. 6 25 in 10 mim 25 in 2 min. 39- 9.6 25 in 6 min. 25 in 3 min. 40 9. 6 16 4l 9.6 1l.8 42 9. 6 11.2-- 43 9. 6 16.4. 44 9. 6 18.4.- 45 9. 6 15.6. 46 9. 6 14.0-.-- 47 9. 2 17.0. 48.- 9. 2 21.0- 53.- 9. 6 13.8- 25 1n 12 min 54-- 9. 6 11.2- 25 in 8 min 55-- 9. 6 9.8- 0.2 56.- 9. 6 13.0. 57.- 9.6 11.2. 58 9. 6 22.0- 59 9. 6 35.0. 60.. 9. 6 15.2- 61-- 9. 6 13.6. 16.0. 62.. 9.6 1.6-. 25 in. 2 min. 63-- 9.6 13.6. 16.4 64.. 9. 6 21.4- 65-- 9. 6 20.4. 66-- 9. 6 6.0.- 67 9. 6 19.4

n Sample aged in a closed cylinder at 250 F. for 24 hours or longer, then cooled to room temperature und tested. h Tested in a Baroid high-temperature lter press; result doubled to convert it to regular API basis.

is applicable to fracturing of subsurface earth intervals; the invention may also be used in treatment of a selected zone pierced by a well with a chemical to improve the characteristics of a selected zone, with the emulsion being used to protect or blanket another selected zone to prevent damage thereto or to prevent change of character of the protected zone.

The present invention may suitably be used in dual or multiple completions where there may be iluid communication between vertically spaced apart zones, the improved emulsion being used to protect one zone while a remedial or sealing operation is conducted in the other Zone.

It is also important in the present invention that, whenever operations are conducted in a well, the emulsion is the first uid, other than the desired mineral, such as oil and/or gas, which contacts the exposed perforations. Thus, it is specifically contemplated that the emulsion may be used to contact the perforations and protect same following which drilling uid, mud, salt Water, and the like may then be ilowed past the protected perforations which may contain the emulsion. The emulsion thus protects the clean perforation, without damaging the earth interval and without losing iluid thereto.

It is also within the purview of the invention to conduct all workover operations using the present invention 50 with the improved emulsion protecting exposed faces of earth intervals undergoing servicing or reworking. However, the emulsions of the present invention may be used with other Well fluids so long as the exposed interval is protected against damage by contact with the detrimental lluid.

The nature and objects of the present invention having been completely described and illustrated, what We Wish to claim as new and useful and to secure by Letters Patent is:

1. A method for completing and servicing a Well containing drilling fluid in which high temperatures of the order of 200 to 250 F. are encountered which cornprises placing in said well an emulsion, containing from about 5% to about 95% by volume of an aqueous medium, from about 5% to about 95% by volume of an oily medium, a Weighting agent in an amount within the range between about 1% by Weight to about saturation dissolved in at least one of said media, and an emulsifying agent selected from the alkali metal salts of puried lignin sulfonic acids, in which sugars, hemicelluloses, and other degradation products have been removed, containing from about 3% to about 33% by weight snlfonate groups and ammonium and alkali metal salts of lignin sulfonic acids containing from about 38% to about 57% lignin sulfonic acid groups in an amount in the range between 0.2 and about 20 grams per 100 ml. of the external phase of the emulsion, said emulsion having a density in the range from about 7 to about 18 pounds per gallon and different from that of the drilling fluid and a viscosity at 60 F. in the range from about 10 to about 4,000 centipoises, displacing a portion of said drilling iluid in said well from a point adjacent a selected subsurface interval penetrated by said Well, contacting an exposed face of said selected subsurface earth interval at said point with said emulsion to protect said exposed face against contamination with said drilling fluid such that the emulsion is the irst uid other than hydrocarbons which contacts said exposed face, performing an operation in said Well, said emulsion being subjected to said temperatures of the order of 200 to 250 F. in said well and being maintained in contact with said exposed face While said operation is being performed, said emulsion being characterized by having a low ltration rate and by not damaging said earth interval, said emulsion being stable at said temperature, removing said emulsion from said exposed face after completion of said operation, and then producing hydrocarbons from said exposed face.

2. A method in accordance With claim 1 in which the operation in said well comprises the placing and operation of a perforator in said emulsion to penetrate the selected earth interval.

3. A Well completion composition which comprises an emulsion containing from about 5% to about 95% by volume of an aqueous medium, from -about 5% to about by volume of an oily medium, a weighting agent in amount Within the range from about 1% by Weight to about saturation dissolved in at least one of said media, and an emulsifying agent in an amount in a range between about 0.2 and about 2O grams per 100 ml. of the external phase of the emulsion selected from the group consisting of alkali metal salts of purified lignin sulfonic acids, in which sugars, hemicelluloses, and other degradation products have been removed, containing from about 3% to about 33% by weight sulfonate groups and ammonium and alkali metal salts of lignin sulfonic acids containing from about 38% to about 57% by Weight lignin sulfonic acid groups, said emulsion being heat stable at Well temperatures of the order of 200 to 250 F.

4. A composition in accordance with claim 3 in which the agent is a high specic gravity halogenated hydrocarbon `dissolved in the oily phase of the emulsion.

References Cited in the le of this patent UNITED STATES PATENTS 2,223,397 White Dec. 3, 1940 2,742,426 Brainerd Apr. 17, 1956 2,805,722 Morgan et al. Sept. 10, 1957 OTHER REFERENCES Dispersants From Silte Liquor by Salvesen et al. Reproduced from Chemical Industries, August 1947.

Claims

1. A METHOD FOR COMPLETING AND SERVICING A WELL CONTAINING DRILLING FLUID IN WHICH HIGH TEMPERATURES OF THE ORDER OF 200* TO 250*F. ARE ENCOUNTERED WHICH COMPRISES PLACING IN SAID WELL AN EMULSION, CONTAINING FROM ABOUT 5% TO ABOUT 95% BY VOLUME OF AN AQUEOUS MEDIUM, FROM ABOUT 5% TO ABOUT 95% BY VOLUME OF AN OILY MEDIUM, A WEIGHTING AGENT IN AN AMOUNT WITHIN THE RANGE BETWEEN ABOUT 1% BY WEIGHT TO ABOUT SATURATION DISSOLVED IN AT LEAST ONE OF SAID MEDIA, AND AN EMULSIFYING AGENT SELECTED FROM THE ALKALI METAL SALTS OF PURIFIED LIGNIN SULFONIC ACIDS, IN WHICH SUGARS, HEMICELLULOSES, AND OTHER DEGRADATION PRODUCTS HAVE BEEN REMOVED, CONTAINING FROM ABOUT 3% TO ABOUT 33% BY WEIGHT SULFONATE GROUPS AND AMMONIUM AND ALKALI METAL SALTS OF LIGNIN SULFONIC ACIDS CONTAINING FROM ABOUT 38% TO ABOUT 57% LIGNIN SULFONIC