DE2829168A1 - METHODS FOR DRILLING TREATMENT AND APPROPRIATE MEANS - Google Patents

Description

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1A-51 082 Applicant: Shell Int.

Patent application

Applicant: SHELL INTERNATIONAL RESEARCH MAATSCHAPPIJ B.V. Carel van Bylandtlaan 30, The Hague, Netherlands

Title: Borehole Treatment Process and Appropriate Means

8192

809883/0934

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1A-51 082

Applicant: Shell Int.

Description

The invention relates to a method for treating a borehole, to dissolve silicate material, which may be a bit removed, but still with the liquid in It comes into contact with sands or clays that adversely affect permeability, or in or around the borehole itself. According to the method according to the invention, the silicate material is made using a self-acidifying solution of a fluoride and a relatively slow-reacting and acid-producing substance dissolved in this with the silicate material is brought into contact before the solution becomes strongly acidic.

The solution can dissolve the silicate material in one

can
converting still relatively high pH and / or dispersible clay or silicates with a grain size of the clay to non-dispersible solids. (U.S. Patent 3,828,854).

According to the method according to the invention, an aqueous solution of a fluoride is added to the area containing the silicate material and a relatively slow-reacting, acid-donating substance injected, which in addition at least ^ o a chlorocarboxylate contains in solution, the chlorine of which is relatively easy to hydrolyze. The agent used according to the invention is therefore an aqueous solution of a salt of hydrofluoric acid and of at least one chlorocarboxylate with easily hydrolyzable Chlorine. The term "dissolved chlorocarboxylate" is understood here to mean an aqueous solution of at least one mono- or poly-

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chlorinated carboxylic acid and / or its salt.

In many cases such treatments are for oil wells desirable in which the composition of the injection solution is adjustable so that essentially all of it dissolved chlorocarboxylate, which comes into contact with the oil deposit, only contains certain salts of chlorocarboxylic acids « This ensures that there is practically no chlorinated organic Product is dissolved in the oil. As is well known, lead - such Substances often poison the catalysts in the course of processing the crude oils and during refining.

or self-foaming

It has now been found that a self-regenerating / sludge acid, in which the acid-releasing reaction component is the dissolved Is chlorocarboxylate, in a second reaction stage in counter v / kind of excess clay or other silicates reacts. In the second stage of the reaction can be more clay than the stoichiometric Limit for the amount of fluoride ions present (as with usual

_v for sound or

chen sludge acid systems) corresponds to / dispersible solids of the same size are converted into non-dispersing solids “Non-dispersible products only take a relative a small proportion of the pore volume in the formations and therefore improve the permeability and / or the extent of solidification of the treated formations.

In addition, a self-acidifying sludge acid system, in which the acidifying substance is a chlorocarboxylate, the rate of hydrolysis with the formation of HCl and a hydroxycarboxylic acid noticeably higher when the pH value rises. In certain cases this is advantageous when the reservoir temperature is too low for a desired rate of hydrolysis in the acid solution, so that an essentially neutral or alkaline solution can inject relatively slowly into the reservoir at such a rate that the relatively high The hydrolysis rate is high due to the high pH value

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is held by the alkaline reacting components of the accompanying rock. Such injections can be interrupted again and again, to ensure that sufficient hydrolysis takes place. However, it reduces hydrolysis within any one Part of the solution gradually adjusts the pH to such an extent that the rate of hydrolysis is reduced to ensure that appropriate proportion in a further part the deposit is pressed, which causes the neutralization of the acids with an increase in pH.

The method according to the invention and the means suitable for it are of particular importance in the treatment of formations in and around boreholes, the permeability of which is impaired by dispersed or adhering particles of clay or silicates will. The high pH value and the relatively slow reaction of the agent according to the invention lead to less damage the acid-sensitive cement protection of deposits solidified with synthetic resins or the like. And beyond that, too to improve the effectiveness in terms of permeability.

The aqueous liquid according to the invention for / self-acidifying Sludge acids can be used in any way relatively soft water, brackish water, Contain fresh water or pure water. Since multivalent cations can lead to a precipitation of the fluoride and higher Concentrations of dissolved salts lead to a reduction in the solubility of the silicates in the hydrofluoric acid solution, soft water, at least like pure or fresh water, is preferred. If necessary, you can also use chelating agents in it or scavengers, such as / polyacetate (ethylenediamine-tetraacetic acid, Citric acid or the like.) Use to improve the tolerance of such liquids for polyvalent cations.

According to the invention, at least in some cases essentially any water soluble fluoride can be used, but asionium fluorides are preferred. As is well known for Al | bniuiabifluorid a corresponding amount of ammonia is added to im

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to have substantially equal proportions of ammonium and fluoride ions. One can also ammonia or ammonium hydroxide in excess or deficiency apply, to increase the initial pH or to lower and thus the extent _(in which the carboxylic acid chloride is converted to the ammonium salt, to increase or decrease.

Any chlorocarboxylic acid which is relatively easily soluble in water can be used according to the invention. their water-soluble salts ₍ and which are hydrolyzable with respect to at least one, preferably all chlorine atoms at moderate temperatures, such as about 40 to 150 ⁰ C (310 to 420 K), and at moderate speeds, which half-lives (for

unhydrolyzed chlorocarboxylic acid or its salts) in size.

Order of about 0.5 to 10 h / such acids expediently contain one or more chlorine atoms and "can be aliphatic, alicyclic or aromatic carboxylic acids, such as monochloro and dichloroacetic acid, 2-chloropropionic acid, the chlorobenzoic acids, 2,3-dichlorobenzoic acid, p-chlorohexahydrobenzoic acid or the like. Particularly suitable are chlorocarboxylic acids whose half-lives for hydrolysis are sufficient for many deposit temperatures and include monochloroacetic acid, 2-chloropropionic acid and Di chiοre s acetic acid.

The concentrations of fluorides and chlorocarboxylates in the self-acidifying system according to the invention can be over wide ranges vary. It is generally desirable that the hydrolysis of the chlorocarboxylic acid ions provide sufficient HCl to power the system to make at least 0.1 η hydrochloric acid, and that the system Contains sufficient fluoride to make it at least 0.1 η hydrofluoric acid.

If there are equimolar proportions of ammonia and acid then present when a chlorocarboxylic acid is mixed with water, ammonium fluoride and ammonia, the pH value is essentially new.

_ 5 8 0 9 8 8 3/0 9 3 A

1A-51 082

be neutral due to the ionization constant of the special chlorocarboxylic acid (such as 6.5 for monochloroacetic acid). While the solution flows to greater depths and is within the There is piping, the rate of hydrolysis increases with increasing temperature. The hydrolysis takes place with the chlorocarboxylic acid and their anions and leads to a mixture of hydrogen chloride and hydroxycarboxylic acids. Acid formation lowers the pH of the solution and converts the fluoride into hydrofluoric acid.

The composition and concentration of the chlorocarboxylic acid in the injection solution can be adjusted to the temperature of the deposit and the rate of injection for a predetermined amount of hydrolysis within the casing. As soon as the injection solution begins to flow in the clayey deposit, ground the acids are consumed quickly and the pH rises as the rate of dissolution of the clay is much greater than that Rate of hydrolysis. Consequently, the speed of the

The sound resolution is limited by the speed at which acids

formed by hydrolysis of the sludge acid.

If, in this situation, ammonia or ammonium hydroxide is used in an amount greater than the stoichiometric amount of the chlorocarboxylic acid, so the pH of the solution rises as a function of this excess. The rate of hydrolysis for a given temperature is larger due to the higher pH while the solution is in the piping. Though this at a faster rate If the acid leads to hydrolytic release, more acid is needed to lower the higher pH before hydrogen fluoride is released. Within a clayey formation, the speed of sound resolution will adjust to one Rate as a function of the rate of hydrolysis at an essentially neutral pH, since the hydrolytic Released acids are then used up essentially as quickly as they are released.

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If, in the above case, a stoichiometric excess of carbonic acid is used, the solution can have at least two different phases of behavior with regard to the dissolution of clay. Pass the R _e action partner essentially of carboxylic acid chloride and ammonium fluoride, the system behaves initially like a conventional mud acid from a mixture of a weak chlorine carboxylic acid and hydrofluoric acid. If the system also contains at least a significant amount of ammonia, preferably sufficient to neutralize most of the chlorocarboxylic acid, the system initially behaves like a buffered sludge acid (US Pat. No. 3,889,753). If, for example, the system consists essentially of significant proportions of hydrochloric acid, chlorocarboxylic acid and ammonium carboxylate in a mixture with ammonium fluoride, the system initially behaves like a normal HCl-HF sludge acid and then becomes a buffered and finally a self-acidifying one in which the acid-forming component is the Is chlorocarboxylic acid and / or its salt. ·

According to the invention, the solution contains less ammonia or another alkali than to essentially neutralize of all the acid initially present is required, it is desirable that the proportion of ammonium fluoride be substantial is greater than stoichiometric for the acid-base reaction of the non-neutralized and non-hydrolyzed amount of acid is needed. This ensures that after the free acid has been used up, the deposit is subject to prolonged treatment with the self-acidifying Sludge acid, the acid-yielding reaction component of which is a salt of chlorocarboxylic acid, is subject.

The method according to the invention is also suitable for treatment of boreholes (U.S. Patent 3,868,998) in which a mud of fine-particle materials that can form sand or split packs in boreholes or cracks in underground formations * is applied to a viscous, slow-acting acidic solution with little loss of liquid along and into the walls of such cracks

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to urge / temporarily a fast-acting acid from a To displace zone, which acts as a "thief zone", in the treatment to improve the permeability profile in an interval of inh like permeable formations or the like. Water-soluble cellulose ethers, which are relatively acid-sensitive, can be used as thickeners, such as hydroxyalkyl, carboxyalkyl or lower alkyl cellulose ethers (hydroxy

to serve. ethyl, carboxymethyl cellulose, methyl cellulose) These substances are themselves completely soluble and form completely soluble hydrolysis products when they are in acidic aqueous liquids be hydrolyzed.

The invention is explained further with reference to the figures. Fig. 1 shows a diagram in which the amount of clay (g / l), which dissolved or has been implemented against the time is plotted. Fig. 2 shows a diagram relating to the change in the rate of hydrolysis (Half-life) as a function of temperature.

The diagram in FIG. 1 shows the results for the suspension of excess sodium bentonite in an inventive Sludge acid. The solution investigated was 1.5 η for monochloroacetic acid and 1.5 η for ammonium hydroxide and ammonium fluoride 1 n. The proportion of initially suspended.

Clay was 25.77 g / l and the suspension was the times indicated

ο specific

held at 93 C. The test amounts included the proportion of total suspended solids and the percentage of clay remaining in those solids (determined by X-ray diffraction analysis). A _u s these flows and the initial concentrations of the amount (g / l) of unreacted clay, clay and unreacted solids was calculated.

The measuring points of the diagram according to FIG. 1 and the calculation bases are summarized in Table I. Curve A and B of the Fig. 1 relate to the amount of converted clay and the

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Amount of dissolved solids. The straight line C corresponds to the stoichiometry.

809883/0934

I. H Tone in
suspend
th fabrics
% (A) total sus
pending
Solids
ä / 1 (B) TABEL I. not-
react
the tone
ff / 1 (D) react
the tone
g / l (E) B + D
(containing Al,
Si, F etc.)
g / l _i.
O 0 _; 00 100 25.77 25.77 0.00 0.11 0.33
0.67 92
92 24.51
22.28 net
solved
Solids
g / i (c) 22.55
20.50 3.22
5.27 1.96
1.78 1.00 90 22.69 0.00 20.42 5.35 2.27 80988 1; 33
1.67 90
88 21.15
21 _; 74 1.26
3.49 19.04
19.13 6.73
6.64 2.11
2.61 2.0 89 20.31 3.08 18.08 7.69 2.23 σ
co
Approx
Jt- 3.0 87 21.62 4.62
4.03 18.81 6.96 2.81 4.0 80 18 _; 7Ο 5.46 14.96 10.81 3.74 5.0 79 17.11 4.15 13.52 12.25 3.59 6.0 78 16.87 7.07 13.16 12.61 3.71 7.0 72 19.18 8.66 13 _; 8l 11.96 5 _; 37 8.90 6; 59

TABLE I.

8.0 12 24

48

Tone in total sus- net- no- reactionp-

suspended-dissolved reacted clay

th substances solids solids ^{ter clay}

% (A) g / l (B) g / l (C) g / l (D) g / l (S)

80 68 60

43 28

19.91 16.28 21.35 17.04 17.64

5.86 9.49

4.42

8.73 8.13

9.84
14 _; 7O
12.96
18 _; 44
20.83

B ■ + D

(containing Al,

Si, F etc.) g / l

3.98 5.21 8.54

■ 9.71 12.70

2829! 68

Table II shows similar results in one trial

temperature of 107 ° C.

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809883/0934

TABLE II

ο
co
c *>

Tone in total sus-

suspended substances solids

g / 1

net dissolved solids

unresponsive

third tone g / l (D)

react
the tone

0.00 1.00 0 _; 33 87 0.67 84 I ₇ OO - 1.33 78 1.67 - 3.0 71 4.0 69 5.0 69 6 _; 0 65 7.0 68

26 _; 02 21.94 19.54 24 _; 08 18.75 22.83 20 _; 63 17.04

17.01 16 _; 96 16.28 16 _; 27

0.00 4 _f 08 6 _f 48

1; 94

7 _; 27 3.19 5.39 8.98

9.01

9.74 9.75

02/26

21 _; 70

11

12.10

11.74 ll _; 70 10 _; 58 ll _; 06

0 _; 00

9.61

I4 _; 6l

13.92
14 _; 28
14.32
15 _; 44
14.96

B + D (containing Al,

Si, F etc.)

g / l

0 _; 00 0.24 3 ₇ 13

7 _; 34

4 _? 94 5.27

5 _; 26th

5 ₇ 7O 5.21

Nb

QQ

■ rt.i5j-ilj.Lui .Li.

OO OO Ca>

8.0 12 2k.

unreacted tone

Tone in total SUS nettosuspendier- pendierte dissolved reagis-r ^h th fabrics solids' solids ter tone

% (A) g / l (B) g / l (C) g / l (D) g / l (E)

63

h -

15.73 17. ^r '- ^:

0

b. 9

9.94 4.15 .1.46 1 / η 0 i. (J. U ο

21.86 24.56

B + D (containing Al,

Si, F etc.) g / l

1A-51 082

From Fig. 1 and Tables I and II it can be seen that the behavior of the solution according to the invention up to about 15 hours in terms of the dissolution of clay is similar to that of a self-acidifying system according to US Pat. No. 3,828,854. At about 15 hours

to is the amount of dissolved solid / about 2/3 of the converted clay.

For longer times, however, such as 48 hours, the solution according to the invention leads to a reaction which does not occur when the Hydrolysis products are primarily a weak acid such as formic acid and an alcohol such as methanol. The inventive System, which by hydrolysis both a strong acid (hydrochloric acid) and a weak acid (hydroxycarboxylic acid) forms, reacts long after a maximum in terms of solids dissolution. This is the second Reaction stage, in which further clay, is converted almost completely into solids, the silica, aluminum and contain fluorine. In a scanning electron microscope one sees that the solid end products are well-defined small crystals which are deposited on the grain of sand packs. Vfie indicated in Fig. 1 appears to have increased after 48 hours Clay resolved as the 15 g / l used as the stoichiometric limit (curve 10, Fig. 1) for analogous self-acidifying sludge acids

assume that are 2 m in methyl formate and 1 min in ammonium.

fluoride (US Pat. No. 3,828,854 Fig. 2) Although the second reaction stage in the process of the invention does not lead to an increase in the dissolution of solids, replacing the dispersible clay with a nondispersible solid improves the permeability and / or stability of the formation. As can be seen from Table II, results of the second reaction stage at 107 ^° C. similar to those obtained at 80 ^° C. are also obtained.

A tone-dissolving reaction occurs in the method according to the invention one after which all of the free acid originally present has been used up, and the rate at which the clay or

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Silicate material can be dissolved is limited by the rate at which an HF-containing solution is hydrolysed of the chlorocarboxylate is formed. The response appears to be based on the following equation. However, it should be noted that that the invention is not dependent on any particular mechanism. If a clay dissolving solution is a aqueous solution of ammonium chloroacetate and ammonium fluoride, the hydrolysis and ionization appear to be based on the following equations to be based:

Cl-CH ₂ -COO "+ H ₂ O = HO-CH ₂ -COOH + Cl"

Chloroacetate glycolic acid

and
HO-CH ₂ -COOH = HO-CH ₂ -COO "+ H ⁺ , pk _& = 3.83

Glycolate

The probability of the occurrence of such a mechanism is shown by the X-ray analysis of the precipitates from cold spent solutions which contained considerable amounts of dissolved calcium carbonate. The X-ray diagram of such solutions corresponds to a hydrated calcium glycolate. It seems that - if the self-acidifying sludge acid is a mixture of salts the hydrofluoric acid and chlorocarboxylic acids - the hydrolysis of the chlorocarboxylate ions to an acid containing hydroxycarboxylic acid and hydrofluoric acid, with a relatively low

of the chlorine atoms _.

speed is compared to that with / from the chlorocarboxylate ions be hydrolyzed.

Fig. 2 shows in a diagram the dependence of the hydrolysis rate (Half-life in min) with the temperature for 2-chloropropionic acid (curve D), monochloroacetic acid (curve E) and dichloroacetic acid (curve F). Curve G relates to methyl formate and is used for comparison. The half-lives for

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the Chlorcarbonsäureanionen were determined at different temperatures in buffered solutions wäi3rigen at a pH value of 5 to 5, 5 no sand or clay in test tubes by titrating the Chlorariionen that are released during the hydrolysis. As is apparent from Fig. 2, is one particularly useful half-lives of about 40 to 400 min (DR in Fig. Z) for a temperature of about 77-121 ⁰ O determines which generally corresponds to the temperature of the deposits. In the case of acid treatments of boreholes, in which generally the application of a "shut-in time" corresponding to about 3 half-life

zeiten (regarding the acid-supplying reaction partner; / in a sludge acid system, such solutions result in a shut-in time range of about 2 to 20 hours.

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Claims (7)

Claims 1. Process for the acid treatment of boreholes by Injecting a silicate material-dissolving aqueous solution of a fluoride and a relatively slow-reacting acid-forming one Material, characterized in that a solution is injected which contains at least one chlorocarboxylate contains dissolved, the chlorine of which is relatively easy to hydrolyze. 2. The method according to claim 1, characterized in that a solution is injected whose Cations are essentially all ammonium. 3. The method according to claim 1 or 2, characterized in that g e k e η η ζ ei c h η e t that a solution is injected, the chlorocarboxylic acid and / or contains its salt and / or hydrogen chloride in an amount which is below the stoichiometrically required Amount for the neutralization of the fluoride. 4. The method according to claim 3, characterized g e k e η η ζ e ichnet that a solution is injected which a Chlorocarboxylate, preferably ammonium monochloroacetate, contains. 5 ". The method according to claim 1 to 4, characterized in that the injected solution in the The deposit is left longer than it is for the hydrolysis of im contributes substantially to all of the chlorine from the chlorocarboxylate Deposit temperature is required. 809883/0934 " ² ORIGINAL INSPECTED - 2 - 1A-51 082 6. The method according to claim 1 to 5, characterized in that a solution is injected, the one Contains thickener, in particular from a cellulose ether for relatively high viscosity. 7. The method according to claim 1 to 6, characterized in that a solution is injected whose chlorocarboxylate Mono-, dichloroacetic acid and / or 2-chloropropionic acid and / or their salts is » ö. Means for carrying out the method according to claim 1 to 7 in the form of an aqueous solution of a fluoride and of at least one chlorocarboxylate, the chlorine of which is relatively easy is hydrolyzable. 8192 809883/0934