FR2488325A1 - PROCESS FOR THE PRODUCTION OF A HOMOGENEOUS AND VISCOUS WELL MAINTENANCE FLUID WITHIN A BOREHOLE AND WELL MAINTENANCE FLUID COMPOSITIONS - Google Patents

Abstract

PROCESS FOR PRODUCING A THICK AQUEOUS MEDIUM WITHIN A SURVEY COMPRISING THE ADDITION TO THE AQUEOUS MEDIUM OF A FIRST HYDROPHILIC POLYMER WHICH INCREASES THE VISCOSITY OF THE ENVIRONMENT AT AMBIENT TEMPERATURE AND OF A SECOND HYDROPHILIC POLYMER WHICH DOES NOT INCREASE APPROXIMATELY THE VISCOSITY AT AMBIENT TEMPERATURE, BUT WHICH INCREASES THE VISCOSITY AT HIGH TEMPERATURE, THE MIXTURE OF THE AQUEOUS MEDIUM AND POLYMERS TO INCREASE THE VISCOSITY, THE PUMP OF THE LARGELY RENDERED SO MUCH DESIRED IN THE SURVEY AND AGING OF THE PARTIALLY VISCOUS MEDIUM TO ALLOW BOTH POLYMERS TO HYDRATE TOTALLY.

Description

The present invention relates to methods for increasing viscosity and

  reduce fluid losses in aqueous brines, and aqueous maintenance fluids

wells thus prepared.

  Thickened aqueous media, in particular those containing soluble salts, are commonly used as well maintenance fluids, such as drilling fluids, reconditioning fluids, conditioning fluids, "packer" fluids (packing materials). sealing), well treatment fluids, underground formation treatment fluids, spacing fluids, well abandonment fluids

  and other aqueous fluids whose viscosity is desired to be increased

  cosity. We know how to use hydrophilic polymeric substances.

  such as hydroxyethyl cellulose (HEC) and xanthan gums as thickening agents for the media

  aqueous used in these well maintenance fluids.

  However, these polymers are not easily hydrated,

  solvated or dispersed in certain aqueous systems by the ab-

  high temperatures and / or mixing below

  significant salting for long periods of time.

  For example, the polymers of hydroxyethyl cellulose are poorly hydrated, solvated or dispersed at room temperature in aqueous solutions containing one or more water-soluble salts of multivalent cations, such as dense brines having a density greater than about 1.392 kg / dm3

  which are used in well maintenance fluids.

  Other polymers, such as xanthan gum, require

  high temperatures even in lower density solutions. In many cases, such as

  in reconditioning operations, the equipment available

  available to prepare well maintenance fluids do not

  does not lend itself to high temperature mixing.

  In well maintenance operations where a well-solid maintenance fluid is desired, as in certain conditioning operations, the fluid cannot circulate in the borehole to increase the temperature of the fluid. This is how we usually send the fluid "by keys" in the survey to the required place

  to execute the packaging operation. The temperature

  ture / probing is sufficient to allow the polymer to hydrate when the fluid contains one or more hydrophilic polymers. However, it has been observed that in many cases the polymer forms a sphere or a mass of

  hydrated polymer containing a high polymer content.

  This hydrated polymer sphere then prevents the polymer from increasing the viscosity of all of the brine and / or decreasing the loss of fluid from all of the brine, but in addition it closes the perforations in the well and forms plugs. in the well when the fluid is flowing

outside the well.

  The object of the invention is therefore to provide a new process for the production, within a borehole, of a MvrDilea homogeneous aqueous medium containing one or more pblymers I which do not hydrate in an aqueous medium at temperature

ambient.

  The object of the invention is also to provide an improved, aqueous well-maintenance fluid containing

  a polymer, which produces a homogeneous dispersion of poly-

  mother hydrated when subjected to static aging

tick in a poll.

  Finally, the object of the invention is to provide a pro-

  discontinued use of hydrophilic polymers in fluids

well maintenance.

  These and other goals will appear better at

  reading the description below.

  In one embodiment of the invention, a method is carried out for producing, within a survey,

  a homogeneous, viscous aqueous solution, this process consists

  both to add to the solution (1) a hydrophilic polymer which increases the viscosity of the solution at room temperature and (2) a hydrophilic polymer which does not significantly increase the viscosity of the solution at room temperature, but becomes hydrated in this one solution

  high temperature to increase the viscosity of the solution

  tion, then mix the solution containing the polymers to increase the viscosity of the solution, pump the solution to the desired location in the borehole and allow the solution to age to allow the two polymers to hydrate completely in the solution by following the

high sounding temperature.

  In another embodiment of the invention

  tion, a well maintenance fluid is provided which is characterized by a much higher viscosity when aged at a high temperature than before aging, and which comprises an aqueous solution, a hydrophilic polymer which does not increase the viscosity of the solution appreciably at room temperature, but which hydrates in the solution and makes it more viscous at high temperature, and a hydrophilic polymer which hydrates in the solution and makes it more viscous at temperature

  ambient, in sufficient quantity to maintain in addition

  the other polymer which does not hydrate at room temperature

ambient ture.

  The well maintenance fluid according to the invention requires an aqueous solution, a first hydrophilic polymer (hereinafter referred to as FHP) which does not appreciably hydrate in the solution and therefore does not make it viscous at room temperature. , but which becomes hydrated in the solution

  and makes it viscous at high temperature, and a second poly-

  hydrophilic mother (designated below / iS9P) which hydrates in the solution and makes it viscous at room temperature. This is how SHP gives the solution an initial viscosity which allows it to keep the FHP in suspension, such

  so that the FHP does not hydrate as an agglomerate-

  particle rat which separates from the solution by aging

  static at high temperature.

  The aqueous solution used can be any solution which has the desired characteristics of a well maintenance fluid, such as density, minimal effect on formation, etc., and for which a

  FHP and SHP can be found.

  In one embodiment of the invention,

  the aqueous solution contains a salt chosen from chlo-

  calcium rure, calcium bromide, zinc bromide and mixtures thereof, and has a density of between about and 1.279 / 2.285 kg / dm3. Representative solutions, but

  non-limiting, are indicated in table I. The solutions

  tions with a density between 1.279 and 1.797 kg / dm3

  approximately contain a salt chosen from calcium chloride

  cium, calcium bromide and mixtures thereof. Solutions with a density between about 1.797 and 2.285 kg / dm3 contain zinc bromide and a salt chosen from calcium chloride, calcium bromide and their mixtures. Solutions with a density between about 1.690 and 1.797 kg / dm3 can be formulated from

  so as to contain zinc bromide and calcium chloride

  cium, calcium bromide or mixtures thereof. In all

  these solutions, the FHP can be of polymer XC, defined above

after.

TABLE I

  Density%%% s kg / ctm3 CaC12 CaBr2 ZnBr2 H20

1.279 29.2 0 0 70.8

1.380 37.6 0 0 62.4

1,690 0 53 4 47

1,785 16.3 43.2 0 40.5

1,844 4.4 32.9 24.0 38.7

1.904 0 38.7 24.6 36.7

2,082 0 29.1 41.3 29.6

2.285 0 20 57 23

  Polymer XC is the heteropolysaccharide pro-

  duit by the bacteria Xanthomonas campestris from a

  nutrition solution containing an appropriate carbohydrate

  prayed. It is a well-known xanthan gum polymer, which can be used in various cases to make aqueous media more viscous. (See for example the patent

  US No. 3,988,246). XC polymer does not hydrate in sauces

  dense ripe and does not increase the viscosity of these brines,

  as shown in Table I, that very slight-

  or not at all at room temperature. At a temperature-

  ture greater than 54.50C, the XC polymer hydrates in these

  solutions. If the solution is stirred at high temperatures

  The XC polymer hydrates, producing a viscous, homogeneous solution. But with static aging, the

  polymer XC hydrates as a particle mass

  producing them a "ball" or "sphere" and a solution of

low viscosity.

  In solutions with a density greater than about 1.725 kg / dm3, the FHP can be hydroxyethyl

  cellulose (HEC). This is how in solutions containing

  nant a salt chosen from calcium chloride, calcium bromide and mixtures thereof, having a density of between approximately 1.725 and 1.797 kg / dm3, the CET does not hydrate at room temperature, but hydrates easily at temperatures above 54.4WC. Hydroxyethyl cellulose is also an FHP suitable in solutions containing zinc bromide and a salt chosen from calcium chloride, calcium bromide and mixtures thereof, having a

  density between approximately 1.701 and 2.285 kg / dm3.

  Hydroxyethyl cellulose is a well-known viscosity enhancer for aqueous media (see, for example, US Patent No. 3,852,201). HEC polymers

  are solid, particulate substances which are solu-

  in water or dispersible in water and which, in solu-

  tion or in dispersion in an aqueous medium, increase the viscosity of the system. HEC polymers are generally

  non-ionic substances, soluble in water, to make

  high, which is produced by treating the cellulose with sodium hydroxide and then reacting the product

  obtained with ethylene oxide. Each unit of anhydroglu-

  cose in the cellulose molecule contains 3 reactive hydroxy groups. The degree of substitution (D.S.) indicates

  the average number of hydroxy positions on the anhydro- unit

  glucose that reacted with ethylene oxide. The D.S.

  maximum is 3. Molecular substitution (M.S.) is

  defined as the average number of ethylene oxide molecules

  lene that reacted with each unit of anhydroglucose. Once a hydroxyethyl group is attached to a unit, it

  can then react with another molecule of ethyl oxide

  lene. Good solubility in water is obtained for a D.S. value of between approximately 0.75 and 1.75 and a

  M.S. value between about 1.75 and 3.0.

  In solutions having a density of less than about 1.725 kg / dm3, containing a salt chosen from

  calcium chloride, calcium bromide and their mixtures

  ges, the SHP can be hydroxyethyl cellulose. HEC easily hydrates in these solutions and makes them more

  viscous at room temperature.

  Solutions having a density of between about 1.725 and 1.797 kg / dm3, containing a salt chosen from calcium chloride, calcium bromide and

  their mixtures, and solutions having a density

  taken between approximately 1.725 and 2.285 kg / dm3, containing zinc bromide and a salt chosen from calcium chloride, calcium bromide and their mixtures, are very

  difficult to make more viscous at room temperature.

  But in US patent applications No. 119,805 of February 8, 1980 and No. 146,286 of May 5, 1980, it has been shown that the HEC can be activated to cause hydration easily

  in these brines and make them more viscous at

  ambient rature. This is how for these solutions, the HEC

  is an effective SHP provided it is activated.

  Examples of SHP compositions useful in the present invention, as indicated in US patent application No. 119,805 of February 8, 1980, include: hydroxyethyl cellulose, a solvating agent consisting of a polar organic liquid, miscible with water, which,

  when uniformly mixed with HEC in a ratio

  weight port HEC / solvating agent of 1: 2, produces a mixture containing no free liquid solvating agent after standing for one week at room temperature in a sealed container, and a diluent consisting of an organic liquid which does is not a solvating agent. As preferred solvating agents, mention may be made of ethylene glycol, glycerol, propane glycols, butane glycols and their mixtures. Preferred diluents are isopropanol and ethylene glycol lower alkyl ethers, such as ethylene glycol n-propyl ether, ethylene glycol ether.

  ethylene glycol n-butyl, isobutyl ether

thylene glycol, and the like.

  This SHP composition preferably contains about 15 to 25% HEC, about 15 to 50% of solvating agent

  and about 25 to 70% thinner. Other examples of

  SHP positions which are useful in the present invention, as indicated in US Patent Application No. 146,286 of May 5, 1980, include: HEC, an aqueous liquid, and a water-soluble organic liquid, which,

  when uniformly mixed with HEC in a ratio

  1: 2 HEC / organic fluid weight, produces a non-mixing / container / free liquid after resting

  week at room temperature in a sealed container.

  As examples of organic liquid, mention may be made of the iso-

  propanol and ethylene glycol lower alkyl ether

  cervix such as 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol and the like. The aqueous liquid may be water or an acid solution, but it is preferably a basic solution having a dissolved hydroxide content of less than about 3N. This SHP composition preferably contains about 15 to 25% HEC, about 15 to 30% of aqueous liquid and about 45 to 70% of organic liquid

soluble in water.

  The concentration of SHP in the fluids of

  The wells according to the invention must only be sufficient to produce a viscosity which keeps the FHP in suspension and in dispersion when the well maintenance fluid is aged in the static state at a high temperature in the borehole. Preferably, the concentration is sufficient to provide the fluid with an apparent viscosity

  API of at least 0.1 Pa.s (i.e. 100 centipoise). The concentration

  maximum tion should only be limited by viscosity

  maximum fluid that can be pumped down the sound-

  dage, with the existing equipment on the well site.

  The FHP concentration in the well maintenance fluid depends on the desired viscosity after the fluid has been statically aged at elevated temperature. The more FHP the fluid contains, the higher the viscosity after aging. Preferably, the FHP concentration is between approximately 1.426 and 28.53 kg / m3, preferably

between 2.85 and 14.26 kg / m3.

  Another feature of the present invention

  is that very homogeneous solutions very

  can be obtained in a site survey-

  desired temperature and prevailing in a survey o

  solutions of the prior art would be too obvious

  women to prepare and pump from the surface.

  The method of the present can be implemented

  invention by preparing the maintenance fluid for wells

  made up of aqueous liquid, FHP and SHP, mixing the fluid to allow SHP to hydrate and increase the viscosity of the fluid enough to keep the FHP in suspension, pumping the fluid to the desired location in a survey and letting the fluid age

  at the temperature prevailing in the survey.

  The term "homogeneous" used here refers to the overall volume of well-maintenance fluid, since the FHP hydrates in the fluid in the limited area in which it is suspended and thus the viscous fluid of well maintenance, after aging in the borehole, could be considered a suspension

  viscous ion of the hydrated polymer and, on a micro-scale

  copic, not appear homogeneous.

  A simple test to determine whether a hydrophilic polymer functions as an FHP or an SHP in a particular aqueous medium is carried out as follows: 1. the aqueous medium and the hydrophilic polymer are mixed together at room temperature for one hour; and

  2. the aqueous medium containing the poly-

  mother overnight at a temperature

  taken between around 54.4 and 121'C, preferably

  at the temperature assumed to prevail in

the poll.

  If the polymer easily makes the aqueous medium more viscous at room temperature, then it can be

  used as SHP. If the polymer does not increase the viscosity

  sited appreciably at room temperature and increases the viscosity at high temperature, it can then be used as FHP. If the polymer does not increase viscosity at high temperature, it cannot be used in well maintenance fluids and in the process

of the invention.

  Other hydrophilic polymers which can be used according to

  the invention can be chosen from cellulose derivatives

  water-dispersible starch derivatives,

  other polysaccharide gums, polymers and copo-

  acrylic, synthetic and similar lymers. As an example-

  ples of cellulose derivatives, there may be mentioned carboxyalkyl cellulose ethers, such as carboxymethyl cellulose and carboxyethyl cellulose; hydroxyalkyl cellulose ethers such as hydroxypropyl cellulose; and mixed cellulose ethers such as carboxyalkyl hydroxyalkyl cellulose, such as carboxymethyl hydroxyethyl cellulose;

  alkyl hydroxyalkyl celluloses, such as methyl hydroxy-

  thyl cellulose or methyl hydroxypropyl cellulose; alkyl carboxyalkyl celluloses, such as ethyl carboxymethyl cellulose (see US Pat. No. 4,110,230). As examples

  starch derivatives include carboxyal ethers

  kyl starch such as carboxymethyl starch and carboxy-

  thyl starch; hydroxyalkyl starch ethers such as hydroxyethyl starch and hydroxypropyl starch; and the

  mixed ethers such as carboxyalkyl hydroxyalkyl ami

  donations, including carboxymethyl hydroxyethyl starch; alkyl hydroxyalkyl starches, such as methyl hydroxyethyl

  starch; alkyl carboxyalkyl starches, such as ethylcar-

  boxymethyl starch, as examples of polysaccha gums

  wrinkles, there may be mentioned: other biopolymers such as other

  very Xanthomonas gums (xanthans); galac gums

  tomannans, such as guar gum, locust bean gum,

  tara gum; glucomannan gums; and their deri-

  ves, in particular hydroxyalkylated derivatives (see

  U.S. Patents 4,021,355 and 4,105,461).

  In particular, guar gum can be used as SHP in solutions having a density at most equal to approximately 1.690 kg / dm 3, containing calcium chloride,

  calcium bromide or mixtures of these two substances.

  The following nonlimiting examples are given by way of illustration of the invention. All measures

  physical properties were carried out according to the methods

  API test reports published in "Standard Procedure for Testing

  Drilling Fluid ", API RP 133, 7th edition, April 1978.

EXAMPLE 1

  An aqueous solution having a den-

  site of 1,785 kg / dm3, containing 16.3% of cal-

  cium, 43.2% calcium bromide and 40.5% water, with the polymers indicated in Table II, for 5 minutes

  on a Multimixer mixer at room temperature (24 C).

  After obtaining the API rheological values, the fluids were worked at room temperature for minutes and the API rheology was evaluated. Then the fluids were statically aged at 740C for 18 hours, cooled to room temperature and evaluated. The data

  obtained are reported in Table II.

  The data indicate that the composition of SHP

  easily made this solution more viscous by

  producing a very viscous fluid at room temperature.

  FHP did not increase the viscosity of this solution at room temperature, and for good reason. of a large sphere of hydrated polymer formed during static hot aging, has developed a low viscosity after heating. The fluid containing both the FHP and the composition of SHP, according to

  the invention exhibited a low viscosity at temperature.

  ambient temperature and very high viscosity after aging

static smoothing.

  The FHP used in this example was Natrosol 250 HHR, a hydroxyethyl cellulose, product of Hercules Inc. The SHP used in this example was a composition containing 20% of hydroxyethyl cellulose Natrosol 250 HHR,% of glycerol, 54.6% d isopropanol and 0.4% CAB-O-SIL

  M5. The concentration indicated in table II is expressed

  compared to a 100% active HEC base.

TABLE II

API RHEOLOGY

  After 5 minutes on the Multimixer

600> 300

  After 1 hour at room temperature

3,600> 300

After 6 p.m. at 74oC

3,600> 300

11.41 0 11.41

300

300 135

300. 205

, 70 11.41

0 11.41 11.41

1.5 300

58 29 0

21,300

0 116 *

  * Obtained on the decanted liquid, separates from the large ball of HEC.

  Me Co Co Lad rv in kg / m3 SHP kg / m3 FHP kg / m3 total HEC, 70

EXAMPLE 2

  An aqueous solution having a den-

  site of 1.904 kg / dm3, containing 38.7% calcium bromide, 24.6% zinc bromide and 36.7% water, with 8.56 kg / m3 of hydroxyethyl cellulose Natrosol 250 HHR as in example 1. During static hot aging, it is formed

  a large mass of hydrated HEC on the surface of the solu-

  tion. By mixing this solution with 2.85 kg / m3 of Natrosol 250 HHR and 5.7 kg / m3 (on a 100% active HEC basis) of the SHP composition used in Example 1, we have

  obtained a well maintenance fluid which, as it ages

  static when hot, produced a homogeneous viscous fluid

uncomfortable.

EXAMPLE 3

  An aqueous solution having a den-

  sity of 1.38 kg / dM3, containing 37.6% of cal-

  cium and 62.4% water with the polymers indicated in Table III, for 15 minutes on a Multimixer mixer

  and we worked at room temperature for 45 minutes

  your. After obtaining the API Theological values, the fluids were statically aged for 16 hours at 650C, cooled to room temperature and evaluated. The data

* are reported in Table III.

  The data indicate that HEC made it easy

  this viscous solution at room temperature and has been shown to be an effective SHP. The XC polymer did not increase the viscosity of this solution at room temperature, and on static aging was hydrated under

  the shape of a polymer mass at the bottom of the container.

  Well maintenance fluid containing HEC and poly-

  mother XC had an initial viscosity due to hydrata-

  HEC and a very high viscosity after aging

  heat static due to combined hydration of 1'-

HEC and XC polymers.

TABLE III

API RHEOLOGY

  After 1 hour at room temperature

600> 300

After 4 p.m.

at 65 C

3,600> 300

24,229

8 0 30

23,300

16 1

  The invention can be implemented under other

  very specific forms without departing from its spirit or its essential characteristics. The present modes of implementation must therefore be considered from all points of view as illustrative and not limiting of the invention and it is clear that modifications can be made without departing

of the framework of it.

SHP kgm 3 Natrosol

250 HHR

  , 70, 70 FHP kg / m3 XC polymer 8.56 8.56

Claims (22)

  1. Method for producing, inside a borehole, a viscous, homogeneous aqueous solution containing one or more hydrophilic polymers which do not hydrate in the aqueous solution at room temperature, characterized in that 'it consists of:   at. add a hydro-   phile in an amount sufficient to increase the viscosity   sity of the solution at room temperature;   b. add a hydro-   phile which does not increase the viscosity of the solution appreciably at room temperature, but which hydrates in the solution at an elevated temperature by increasing the viscosity of the solution;   vs. mix the solution containing the polymers   res to allow the polymer of stage (a) to increase the viscosity of this solution; d. pump the solution containing the polymers to the desired location in a borehole; summer. allow this solution containing the polymers to age, the polymers then hydrating completely as a result of the high temperature of the borehole, producing the homogeneous viscous solution.   2. Method according to claim 1, characterized   in that the hydrophilic polymer of stage (a) is hydroxy- thyl cellulose.   3. Method according to claim 2, characterized   in that the hydrophilic polymer of stage (b) is a poly- mother XC.   4. Method according to claim 3, characterized in that the aqueous solution contains a salt chosen from calcium chloride, calcium bromide and their mixtures and has a density of between approximately 1, 279 and 1.797 kg / dm3.   5. Method according to claim 3, characterized in that the solution contains a salt chosen from calcium chloride, calcium bromide, zinc bromide and their mixtures, and has a density between about 1.279 and 2.285 kg / dm3.   6. Method according to claim 1, characterized in that the aqueous solution has a composition such that   hydroxyethyl cellulose does not hydrate in this solution tion at room temperature.   7. Method according to claim 6, characterized   in that the hydrophilic polymer of stage (a) is hydroxy-   thyl cellulose which has been activated to hydrate in the   solution at room temperature.   8. Method according to claim 7, characterized in that the hydrophilic polymer of stage (b) consists   essentially hydroxyethyl cellulose.   9. Method according to claim 8, characterized in that the aqueous solution contains a salt chosen from calcium chloride, calcium bromide and their mixtures. 10. Method according to claim 8, characterized   in that the solution contains a salt chosen from chlo-   calcium rure, calcium bromide, zinc bromide and their mixtures.   11. Method according to claim 10, characterized in that the solution has a density of between approximately 1.701 and 2.285 kg / dm3.   12. Method according to claim 9, characterized in that the solution has a density of between approximately 1,725 and 1,797 kg / dm3.   13. Well maintenance fluid, having a viscosity   much higher after aging at a temperature   higher than before aging, characterized in that it comprises: a. an aqueous solution;   b. a hydrophilic polymer in a sufficient amount   health to increase the viscosity of this solution at room temperature; and c. a hydrophilic polymer which does not increase the viscosity appreciably at room temperature, but which hydrates in this solution at a temperature   high to increase the viscosity of the solution.   14. Well maintenance fluid according to claim 13, characterized in that the hydrophilic polymer in (b) is hydroxyethyl cellulose.   15. Well maintenance fluid as claimed   cation 14, characterized in that the hydrophilic polymer in (c) is the XC polymer.   16. Well maintenance fluid as claimed   cation 15, characterized in that the aqueous solution contains   holds a salt chosen from calcium chloride, bro- calcium mure and mixtures thereof.   17. Well-maintenance fluid as claimed   cation 15, characterized in that the aqueous solution contains   holds a salt chosen from calcium chloride, bromide calcium and zinc bromide.   18. Well maintenance fluid as claimed   cation 17, characterized in that the aqueous solution has a   density between approximately 1.279 and 2.285 kg / dm3.   19. Well maintenance fluid as claimed   cation 16, characterized in that the aqueous solution has a   density between approximately 1.279 and 1.797 kg / dm3.   20. Well maintenance fluid as claimed   cation 13, characterized in that the aqueous solution contains   holds a salt chosen from calcium chloride, calcium bromide, zinc bromide and their mixtures, and in that this solution has a density of between approximately 1,725 and 2,285 kg / dm3.   21. Well maintenance fluid as claimed   cation 20, characterized in that the hydrophilic polymer in (c) is hydroxyethyl cellulose.   22. Well maintenance fluid as claimed   cation 21, characterized in that the hydrophilic polymer in (b) is hydroxyethyl cellulose which has been activated so as to hydrate in this solution at room temperature.