GB2154631A - Non-foaming water-loss reducer - Google Patents

Abstract

A non-foaming water-loss controller composition is made by adding an anti-foamer to solid particles of a polyvinyl alcohol reaction product. The anti-foamer is present in an amount from about 0.5 to 20% by weight of the polyvinyl alcohol reaction product. The product can be used in making drilling fluids which will not foam. By using this composition, the well drilling operator does not have to measure and add any anti-foamer at the well site.

Description

SPECIFICATION Non-foaming water-loss reducer 1. Field of the invention This invention relates to a method of producing a polyvinyl alcohol reaction product water-loss controller containing an anti-foamerfor oil field drilling use and to the resulting product.

2. Description of the previously published art It has been known to use a polyvinyl alcohol reaction product water-loss controller in oil field drilling muds. Such reaction products are described by Block in U.S. Patent No. 4,349,443; by Green and Block in U.S. Patent Nos. 4,353,804, 4,389,319 and 4,411,800; by Michaels in U.S. Patent No 4,385,155; and by Block and Michaels in U.S. Patent No.4,424,302.

3. Objects ofthe invention It is an object of this invention to produce a polyvinyl alcohol reaction product water-loss controller which has an antifoamer added to the water-loss controller reaction product as the reaction product is being manufactured or prior to its use in formulating a drilling fluid.

It is a further object of this invention to produce a polyvinyl alcohol reaction product water-loss controller which does not foam during use as drilling fluid.

It is a further object of this invention to be able to drill a bore hole in a subterranean formation with a drilling fluid containing a polyvinyl alcohol reaction productwater-loss controller where it is not necessary to have to separately add an anti-foamer in controlled amounts.

Summary ofthe invention The performance of a polyvinyl alcohol (PVA) reaction product as a water-loss controller in an oil field drilling fluid can be improved by the incorporation of a controlled amount of an anti-foamer into the water-loss control agent. The anti-foamer can be added at any stage in the production of the reaction product synthesis or even after it has been formed, dried and stored. However, the preferred point of addition is just after the reaction product has been formed and dried, but before it is packaged or stored so that the anti-foamer is sorbed onto the particles of the reaction product.

The preferred reactants for the polyvinyl alcohol are aldehydes such as formaldehyde or glutaraldehyde and epihalohydrins such as epichlorohydrin. It is believed that any conventional anti-foamer can be used with preferred anti-foamers being Tergitol 15-S-3 made by Union Carbide and n-octanol. The anti-foamer should be added in an amount that is effective to reduce the foaming of the PVA reaction product with weight ranges bf from about 0.5 to 20 wt.% being contemplated and with an upper limit of about 10 wt.% being preferred for the antifoamer Tergitol 15-S-3. Larger amounts could be used, but they would merely increase the cost without contributing to any significant inreased benefit.

Description of the preferred embodiments A very effective water-loss controller can be made by reacting polyvinyl alcohol with an aldehyde or a compound which will produce an aldehyde in situ. Such water-loss controllers are described in U.S. Patent Nos. 4,349,443; 4,353,804; 4,385,155; 4,389,319; 4,411,800; 4,424,302; and 4,428,845. The reaction product can be made continuously as described in Blouin U.S. Patent Application No. 553,510 filed November 21, 1983, now Patent No. 4472552. The entire contents of these patents and patent application are incorporated herein by reference.

These water-loss controllers can be used as drilling fluids for drilling wells or bore holes. Under some circumstances such as when there is a lot of air being mixed with the drilling fluid, unwanted foam can develop. This foam is especially a problem when the foam enters the mud pumps. It is also a problem when removing the cuttings by shaking them over a screen; the foam forms a film over the screen which reduces the amount of mud which passses through the screen leading to losses of whole mud over the screen. It is preferred to avoid the foaming in the first place, rather than attack the foam after it is formed.

At the oil field well site the operator attempts to prevent foam formation by adding some amount of an anti-foamer material. It is difficult to know how much is to be added. Since this anti-foaming material is expensive, adding too much can increase drilling costs. Even if the proper amount is known, there are often problems encountered when, by human error, the proper amount is not added. Furthermore, in the case where a foam has already formed, there may be a problem with the time it takes for the newly added antifoamer to adequately mix with the foaming drilling fluid.

These-problems are overcome by using the water-loss composition according to the present invention where an anti-foamer has been addded directlyto the polyvinyl alcohol reaction product in a controlled, proper amount.

In one embodiment the reaction product is made by using an aldehyde which reacts with the PVA in an aqueous acidic medium having a pH of less than about 5.5. One of the preferred aldehydes is formaldehyde and the preferred form is the commercially availableformalin which is an aqueous solution of 37% formaldehyde which has been stabilized with from 6-15% methanol. Suppliers of this material include J. T.

Baker Chemical Co., Hercules, and Ashland Chemical Co. Other commercial grades of formaldehyde and its polymers could be used. Such commercial grades include 44,45 and 50% low-methanol formaldehyde, solutions of formaldehyde in methyl, propyl, n-butyl, and isobutyl, paraformaldehyde and trioxane. When using solid paraformaldehyde, care must be taken that it all dissolves. If it has not dissolved, then the solid material may remain unreacted when the reaction product is formed and this paraformaldehyde can produce unwanted hazardous vapour when it and the reaction product are subsequently heated in the dryer.

Another preferred aldehyde is glutaraldehyde. Other aldehyde containing or generating reactants are organic chemical compounds which contain at least one aldehyde group therein as are well known and include, for example, acetaldehyde, proprionaldehyde, glycoaldehyde, glyoxylic acid and the like or polyaldehydes i.e., organic compounds having more than one aldehyde group in the compound, such as glyoxal and the like. Other suitable aldehyde reactants include aldehyde generating agents i.e. known organic compounds capable of forming an aldehyde group in situ, such as melamine-formaldehyde monomeric products and derivatives such as tri and hexa(methylol) melamine and the tri and hexa (C1-C3 alkoxymethyl) melamine. Such materials can be formed by known conventional methods.The alkyl blocked derivatives are commercially available, are stable to self polymerization and are, therefore, preferred. Of all of the aldehyde reactants, the preferred reactants are paraformaldehyde, formaldehyde and glutaraldehyde.

The amount of the aldehyde added to the reaction mixture must be controlled. If too much aldehyde is added the product is over cross-linked yielding a material that does not have the desired low controlled fluid loss value of less than 10 cc.

When the aldehyde reacts with the polyvinyl alcohol, two OH groups react with one aldehyde group.

Based on this stoichiometry the amount of aldehyde added is at least about 0.01% and preferably from about 1 to 80 and most preferably from about 2 to 50 percent of stoichiometry of an aldehyde reactant based on the hydroxyl content of the polyvinyl alcohol. On a weight basis, the preferred weight ratio of formaldehyde to polyvinyl alcohol is about 0.0095:1 and for glutaraldehyde to polyvinyl alcohol it is about 0.0016:1. Excess aldehyde can be used. The particular amount of aldehyde agent will depend on its solubility in the aqueous reaction media, and its reactivityas is known and determinable by conventional means.

In another embodiment the reaction product is made by using an epihalohydrin which reacts with the PVA in an aqueous basic medium having a pH of at least about 9.5. The halo group on the epihalohydrin can be Cl or Br and the epihalohydrin can be substituted with a C1 -C3 alkyl group such as methyl, ethyl or propyl. The most preferred epihalohydrin is epichlorohydrin due to its availablilty and the superior product formed.

In conducting the continuous process, as described by Blouin in U.S. Application Serial No. 533,510filed November21, 1983, the enture content of which is incorporated herein by reference, solid particles of polyvinyl alcohol (PVA) are added to the inlet of the rotating continuous reactor. A preferred form of PVA is Gelvatol 9000 made by Monsanto Industrial Chemicals Co. and Vinol 540-S made by Air Products, Inc. The molecular weight for the Gelvatol family PVA and the Vinol family PVA can vary from about 2,000 to 125,000 with the Gelvatol 9000 and Vinol 540-S having a weight average molecular weight of about 125,000. There are many manufacturers of PVA. The preferred PVA weight average molecular weight is at least 20,000 with a more preferred range being from about 90,000 to 200,000.In the preferred forms the PVA is at least about 75 percent hydrolyzed and more peferablyfrom about 80 to 95 percent hydrolyzed.

A wide range of anti-foaming materials can be employed. As described by M. J. Rosen in Surfactants and Interfacial Phenomena (Wiley-lnterscience Publication 1978) antifoaming agents appear to operate by replacing the foam producing surface film by an entirely different type of film. To do this, they must displace any foam stabilizer, such as surfactants, present in the film. They must, therefore, have a surface tension low enough in the pure state so that they can spread spontaneously over the existing film. They must also maintain a high concentration in the surface while being used at very low concentrations. As a result, they must be quite insoluble in the foaming solution, but still not so soluble in-itthatthey do not become a component of the surface film.

Two types are used: foam breakers and foam inhibitors. Foam breakers are materials that destroy existing foam. They may act (1) by reducing the surface tension in local areas to exceptionally low values, thereby causing these local areas to be thinned rapidly to the breaking point by the pull of the surrounding higher tension regions and (2) by promoting drainage of the liquid from the foam film and thereby shortening its life.

Foam inhibitors are materials that prevent foam from being formed. They act by eliminating surface elasticity. They produce a surface that has a substantially constant surface tension when subjected to expansion or contraction. Some inhibitors do this by swamping the surface with nonfoaming, rapidly diffusing, non-cohesive, only moderately surface-active molecules, so that any transient rise in surface tension caused by film expansion is rapidly anulled. Some wetting agents appear to act in this manner.

Others act by replacing the elastic surface film with brittle, close-packed surface film.

In some cases, the foam-breaking and foam-inhibiting properties appear to be additive, and mixtures of a foam breaker and a foam inhibitor show remarkably good foam-breaking and foam-inhibiting properties.

The anti-foaming material used in the present invention can be either a foam breaker or a foam inhibitor.

The preferred type of material is a foam breaker. Examples of preferred foam-inhibitors include the Tergitol 15-S series of nonionic surfactants which are ethoxylates of a mixture of secondary alcohols having chain lengths of 11 to 15 carbon atoms made by Union Carbide. A particularly preferred member is Tergitol 15-S-3 which is a 3 mole ethoxylate of a mixture of secondary alcohols having chain lengths of 11 to 15 carbon atoms. Other inhibitors are n-octanol, Foamaster DF 122 NS (Diamond Shamrock Chemical Co.), Colloid 481-B (Colloids Inc), silicone type anti-foamers made by Dow Corning and the Pluronic family of polyethylene oxide polypropylene oxide block polymers made by BASF-Wyandotte.

When formulating a drilling fluid using the water-loss controller according to the present invention, a viscosifier can be added such as a hydroxy containing aluminum agent which is substantially waterinsoluble. This alumina agent has the formula Alo(OH) and is in suspension or dispersion on aqueous systems. It is characterized by either having an x-ray diffraction spectrum containing a major characterizing diffraction peak at 6.3+0.2 Angstrom units or by having an x-ray diffraction spectrum which is amorphous, that is, having substantially no x-ray diffraction pattern within the range of from 1.5 to 17 Angstroms. The spectrum is determined by standard techniques using the K-a doublet of copper as the radiation source. This preferred AIO(OH) viscosifier is further described by Block in U.S Patent No. 4,240,915 and in other U.S.

patents such as 4,244,835; 4,349,443,4,366,070; 4,389,319; and 4,431,550.

The above-described AIO(OH) composition is capable of imparting to a clay-free, (the term "clay-free" when used herein refers to the absence of drilling fluid viscosifying clays as an essential agent of the fluid and not to other materials entrained therein) aqueous system, such as a water-based drilling fluid (the term "fluid" or "system" when used herein refers to water-based systems containing the subject composition), non-Newtonian, pseudoplasticity. That is to say, that the viscosity of the resultant fluid varies inversely with respect to the shear rate exerted on the fluid.The relationship of the shear stress with respect to shear rate can be defined by the rheological power law model relationship of T= K( y) in which T represents the shear stress exerted on the aqueous system of the drilling fluid in units such as pounds per 100 ft2 or dynesicm2;yis the shear rate in units of reciprocal time such as sec-1; and n is a numerical value greater then zero. When ni, the system is Newtonian; if n is less than 1, the system is pseudoplastic, and if n is greater than 1, the system is dilatant.It has been unexpectedly found that fluids containing the presently described composition exhibit shear stress (T) properties at varying shear rates (w) in the range from about 10 to 400 sec-',that is, in the range normally encountered in the annular region of the bore hole such that n of the power law relationship has a value of less than about 0.4. Such systems, therefore, exhibit non-Newtonian, pseudoplastic properties to an exceptionally high and desirable degree.

The drilling fluid can have various types of viscosifiers. One type is the low solids AIO(OH) viscosifier described above. Other conventional viscosifiers can be alternatively used such as bentonite, attapulgite or sepiolite clay.

By using the product made by the process of the present invention in combination with an aqueous drilling fluid in an amount of from about 0.1 to 15 percent by weight based on the weight of the water present in the drilling fluid and maintaining the system at a pH of from 8 to 12, there results a method of inhibiting fluid loss from an aqueous drilling fluid in subterranean formations without the formation of any substantial amount of foam. Again, the aldehydes used for the reaction product are preferably formaldehyde or glutaraldehyde.

The drilling fluid containing the reaction product made according to the present invention can be used in the process of drilling a bore hole into a subterranean formation using conventional bore hole drilling equipment. In this embodiment the drilling fluid containing the reaction product made according to the present invention is circulated in the bore hole while drilling. Again, the aldehydes used are preferably formaldehyde or glutaraldehyde.

TEST PROCEDURES Drilling fluid preparation A drilling fluid sample was prepared by making a dispersion of a viscosifier and the water-loss controller in tap water. The viscosifier was a tartrate-gluconate stabilized AIO(OH) which was prepared according the the procedure in the Block U.S. Patent No.4,431,440. This stabilized AIO(OH) was then filtered and dried on a Blaw-Knoxdouble drum dryer. The production of the PVA reaction product is described in each example.

The final concentrations were 2.4% AIO(OH) and 1.6% PVA reaction product.

Rheologicalproperties The resulting drilling fluid was tested for its rheological properties using a standard procedure with a Haake Rotovisco rotation viscometer (Model RV-3) at varying shear rates and at 25"C. The values of n and K (given as pounds-sec/100 ft2 and Pa.sec in all examples) in the power law model relationship were determined.

Fluid loss test The fluid loss property of this drilling fluid was determined by the American Petroleum Institute procedure API No. RP-13B. At ambient temperature a sample is placed in a vessel having a screen on the bottom over which a specially treated filter paper is placed. Pressure (100 psig or 690 kPA) is applied and the amount of liquid that flows out in 30 minutes is measured and identified as the control total fluid loss, TFL. It is desirable to have the TFL value less than 15 cc. and more preferably at a value of 10 cc. or less.

An additional test for fluid loss is the roller oven test where the reaction product is heated on a rolling device in an oven at 250"F (1 21'C) for 16 hours. This is intended to simulate the conditions in a well where shear forces exist in addition to elevated temperatures. The TFL is determined in the cooled sample and again it is desirableto have a TFLvalue less than 15 cc. and preferably at a value of 10 cc. or less.

Foam test The de-foaming properties of the PVA reaction product were determined by preparing a 5% dispersion of the water-loss controller in water. The dispersion (200 ml) was placed in a 500 ml graduated cylinder and air bubbled through an extra coarse spargerfor 10 seconds. The foam volume was then measured.

Having described the basic aspects of our invention, the following examples are given to illustrate specific embodiments thereof.

Example 7 This example illustrates the decrease in foaming obtained when the antifoamer is incorporated into the PVA reaction product.

Glutaraldehyde reacted PVA was made by the continuous process described by Blouin in Example 4 of U.S. Patent Application Serial No. 553,510, filed November 21, 1983, the entire contentsof which are incorporated herein by reference, the 25% glutaraldehyde solution was applied at a rate of 2.5 ml per minute to a Gelvatol 20-90 PVA which was supplied at a rate of 2.5 pounds per minute (1.1kg per minute).

The Tergitol 15-S-3 anti-foamer made buy Union Carbide was added to the final product at the rate of 8.5 ml/min. as the material emerged from the dryer. The test procedures described above were used and the results are in Table 1.

TABLE 1 Ambient Roller Oven (250 F) Foam Tergitol K TFL K TFL Vol.

Run Added n (a) (cm3) n (a) (cm3) (cm3) A No 0.29 2.7(1.3) 5.3 10.24 23.0(11.0) 5.7 300+ B Yes 0.23 3.2(1.5) 5.9 0.38 17.8( 8.5) 5.5 10 (a) lb-sec1100 ft2 (and Pa.sec) The results show that good rheological, water-loss control and anti-foaming properties were obtained with the Tergitol 1 5-S-3-containing materials.

Example2 This example illustrates the use of finer sized particles of polyvinyl alcohol.

The procedure described in Example 1 was repeated, with the exception that Gelvatol 9000 having a finer particle size than Gelvatol 20-90 and Vinol 540-S having a finer particle size than Gelvatol 20-90 were used.

Glutaraldehyde was used again and the results are summarized in Table 2.

TABLE 2 Ambient Roller Oven (2500F) Foam PVA Tergitol K TFL K TFL Viol.

Run Type Added n (a) (cm3) n (a) (cm3) (cm3) A 540-S No 0.18 13.6(6.5) 5.6 0.19 10.2(4.9) 7.9 300+(b) B 540-S Yes 0.25 15.0(7.2) 6.2 0.21 8.4(4.0) 6.4 100(c) C 9000 No 0.21 13.5(6.5) 5.8 0.19 11.0(5.3) 5.8 300+(b) D 9000 Yes 0.26 14.0(6.7) 6.8 0.19 10.0(4.8) 7.3 100(c) (a) Ib-sec/100ft2(and Pa.sec) (b) Foam did not break (c) Foam breaks quickly The results show that the anti-foamer can be combined with the water-loss controller to obtain both good foam control, and good water-loss control.

Example 3 This example illustrates using the finer sized particles of polyvinyl alcohol which are reacted with formaldehyde.

The procedure described in Example 2 was repeated with the exception that a formaldehyde solution (37% formaldehyde in water containing 10% methanol) was used instead of glutaraldehyde and the formaldehyde was added at a rate of 27 ml/min. The results are summarized in Table 3.

TABLE 3 Ambient Roller Oven (250"FJ Foam PVA Tergitol K TFL K TFL Vol.

Run Type Reactant Added n (a) (cm3) n (a) (cm3) (cm3) A 540-S Formaldehyde No 0.29 13.0(6.2) 6.1 0.18 12.8(6.1) 8.3 300+(b) B 540-S Formaldehyde Yes 0.20 14.0(6.7) 5.9 0.18 9.2(4.4) 11.4 200(d) C 9000 Formaldehyde No 0.22 15.2(7.3) 6.0 0.19 7.8(3.7) 7.4 300(b) D 9000 Formaldehyde Yes 0.18 14.5(6.9) 5.8 0.19 8.4(4.0) 7.0 10(c) (a) Ib-sec/100ft2 (and Pa.sec) (b) Foam did not break (c) Foam breaks quickly (d) Foam breaks slowly The results show that the antifoamer can be combined with the water-loss controller to obtain both good foam control, and good water-loss control.

Claims (18)

1. A water-loss controller composition comprising solid particles of a polyvinyl alcohol reaction product formed either (a) in an aqueous acidic medium having a pH of less than about 5.5 by reaction between polyvinyl alcohol having a weight average molecular weight of at least 20,000 and at least 0.01 percent of stoichiometry of a compound containing at least one aldehyde group per molecule or capable of generating in situ at least one aldehyde group per molecule or (b) in an aqueous medium having a pH of at least about 9.5 by reaction between said polyvinyl alcohol and epihalohydrin, and an anti-foaming effective amount of an anti-foamer.

2. A composition according to claim 1, wherein the anti-foamer is present in an amount from about 0.5 to 20% by weight of the polyvinyl alcohol reaction product.

3. A composition according to claim 1 or 2, wherein the anti-foamer is an ethoxylate of a mixture of secondary alcohols having chain lengths of 11 to 15 carbon atoms or n-octanol.

4. A composition according to claim 3, wherein the anti-foamer is a said ethoxylate having about 3 moles of ethoxylate per mole of secondary alcohol.

5. A composition according to any one of claims 1 to 4, wherein the said aldehyde is formaldehyde or glutaraldehyde.

6. A composition according to any one of claims 1 to 4, wherein the said epihalohydrin is epichlorohydrin.

7. A composition according to any one of claims 1 to 6, wherein the solid particles of polyvinyl alcohol reaction product are dry and the anti-foamer is sorbed on the particles.

8. A composition according to claim 1 substantially as described in the foregoing examples.

9. A process of making a water-loss controller which comprises reacting a polyvinyl alcohol having a weight average molecular weight of at least 20,000 with at least 0.01 percent of stoichiometry of either (a) a compound containing at least one aldehyde group per molecule therein or capable of generating in situ at least one aldehyde group per molecule or (b) an epihalohydrin, and adding to the reaction product an anti-foaming effective amount of an anti-foamer.

10. A process according to claim 9, wherein the antifoamer is present in an amount from 0.5 to 20% by weight of the polyvinyl alcohol reaction product.

11. A process according to claim 9 or 10, wherein the anti-foamer is an ethoxylate of a mixture of secondary alcohols having chain lengths of 11 to 15 carbon atoms or n-octanol.

12. A process according to any of claims 9 to 11, wherein the aldehyde is formaldehyde or glutaraldehyde.

13. A process according to any of claims 9 to 12 wherein the epihalohydrin is epichlorohydrin.

14. A process according to any of claims 9 to 13 wherein the anti-foamer is added to the polyvinyl alcohol reaction product after the reaction product has been dried.

15. A water based drillng fluid suitable for circulating in a bore hole while drilling the bore hole into subterranean formations which comprises water, a viscosifier and a fluid-loss controller composition as claimed in any of claims 1 to 8, present in said fluid in an amount from about 1 to 15 percent by weight based on the weight of the water present in said fluid, said fluid being maintained at a pH of from about 8 to 12.

16. A water based drilling fluid according to claim 15, wherein the viscosifier is attapulgite, sepiolite or bentonite.

17. Aprocess of drilling a bore hole into a subterranean formation using conventional bore hole drilling equipment, in which the drilling fluid of claim 15 or 16 is circulated in the bore hole while drilling.

18. A method of inhibiting fluid loss from an aqueous drilling fluid in subterranean formations comprising adding the composition of any of claims 1 to 8 to said aqueous drilling fluid in an amount of from about 1 to 15 percent weight based on the water present in said drilling fluid and maintaining said system art a pH of from a bout 8 to 12.