JPH0135156B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates to boring finishing fluid compositions. By the way, the following is mainly desired for underground layer drilling mud for oil wells. (1) Remove the cutting debris generated as the drill bit scrapes the strata from the wellbore, and cool the drill bit. (2) Provides lubrication to the drill stem. The drilling fluid with these functions flows downward through the drill pipe and is injected from the Dorbit nozzle. Then, after passing through the annulus section, it returns to the earth's surface. Most drilling fluids, commonly referred to as muds, contain dispersed hydrated and swollen clay particles. Clay-based fluids have the ability to cool drill bits and transport debris, as well as prevent gas eruptions in high-pressure formations. This is because the colloidal properties of the drilling fluid containing dispersed clay, such as gel strength and specific gravity, greatly improve the various functions of the clay-based drilling fluid. To increase the specific gravity, weighting agents such as barite are added. As Dorbit digs into the production layer during drilling operations, insoluble materials such as clay and barite in the mud create a filter cake on the surface of the formation. Until it reaches the production layer, this filter cake is very important in terms of preventing well collapse, but once it reaches the production layer, the surface of the production layer is blocked with filter cake, resulting in a permanent loss of production. This is a major problem as it causes a decrease in the permeability of the layer. The clay and barite particles that make up these filter cakes can sometimes be removed by a process called acid treatment, but even this costly acid process often does not repair wellbore damage. This is because clay and barite solids have low solubility in acids. Therefore, to prevent damage to permeability, it is necessary to use clean drilling fluids with sufficient specific gravity to suppress formation pressure. This is called the finishing fluid. Similarly,
Since the permeable production layer is in contact with the workover fluid, it is preferred to use a fluid that does not cause formation damage due to its high specific gravity. Commonly used are high-density salt solutions, such as saturated aqueous CaCl ₂ solutions, which do not cause formation damage. The highest specific gravity of _CaCl2 aqueous solution is 1.38g/ ^cm3 (=11.5
(pounds per gallon), which is not satisfactory for all well treatment operations. In a mixed solution of CaBr ₂ and CaCl ₂ , 1.81 g/cm ³ (=
15.1 pounds per gallon). Also
CaCl ₂ aqueous solution and other high specific gravity solutions (e.g.
Mixtures of NaNO ₃ , Ca(NO ₃ ) ₂ , ZnCl ₂ ) have also been proposed to obtain high density fluids. Addition of water-insoluble substances such as _CaCO3 further increases the density of the brine solution and minimizes completion fluid invasion into permeable formations and fractures during gunperforation. It is added for the purpose of CaCO ₃ is often used because it is readily soluble in acids and available in a variety of particle sizes. It is necessary to add polymers to such finishing fluids as thickeners, water loss reducers, and transport enhancers. This polymer also acts as a dispersant for CaCO ₃ . Conventionally, known polymers that provide the above functions include (1) HEC (hydroxyethyl cellulose), (2) CMC (carboxymethyl cellulose), (3) polyacrylonitrile, (4) xanthan gum, (5) guar gum, and in particular, (1) )HEC was mainly used. However, (1) HEC generates bubbles due to stirring and dissolution; (2)
CMC and (3) polyacrylonitrile are not soluble in acids, (4) xanthan gum is only 50% soluble in acids, and (4) xanthan gum and (5) guar gum are degraded by oxygen. ing.
In particular, the generation of foam not only causes corrosion due to oxygen, but also reduces the apparent specific gravity of the liquid, and the foam is so large that it cannot be eliminated even by adding an antifoaming agent, so the cost of adding an antifoaming agent cannot be ignored. . Depending on the type of inorganic cations in the finishing fluid, insoluble substances may be formed with the inorganic cations and precipitated. In order to minimize the corrosion rate of finishing fluids, acid treatments and PH changes such as adding PH modifiers can cause very large viscosity reductions. There are various problems like this. The object of the present invention is to provide a boring finishing fluid containing at least one of monovalent salts or polyvalent salts with excellent thickening properties, water loss reduction ability, transportability, and resolution, stable over a wide range of pH, and with almost no toxicity. An object of the present invention is to provide a finishing fluid composition that does not cause masonry damage. The amount of polymer added is generally 0.3 to 1.5% by weight based on the finished fluid volume. In view of the above-mentioned current situation, the present inventors have arrived at the present invention as a result of intensive research to obtain a water-soluble polymer that is stable against boring finishing fluids containing at least one type of monovalent salt or polyvalent salt. It is. That is, the degree of substitution is
Range of 0.50 to 2.50 and 1% (by weight)
The present invention provides a finishing fluid composition for boring, which contains as an essential component a sulfoethylcellulose alkali metal salt (hereinafter referred to as SEC) having an aqueous solution viscosity of 5 to 5000 (cp). Next, the structural formula of the repeating unit of SEC (when the degree of substitution is 1.0) is shown. _{( Wherein ,} It must be sufficient for sex. In order to have sufficient water solubility, the degree of substitution of SEC needs to be 0.5 or more. When the degree of substitution is less than 0.5, solubility is poor and the effects of the present invention cannot be fully exhibited. Degree of substitution
The reason why the substitution degree is 2.5 or less is that if the degree of substitution is higher than that,
It is difficult to manufacture industrially and is not economical. The viscosity of SEC is not particularly limited, but as long as the viscosity of the 1% aqueous solution is 5 to 5000 (cp), the object of the present invention can be fully achieved. Since thickening properties are usually required, it is particularly preferable that the viscosity of the 1% aqueous solution is 100 (cp) or more. Inorganic salts contained in finishing fluids include:
NaCl, KCl, CaCl ₂ and CaBr ₂ are common, but
Other salts may be preferable depending on economical availability and required density. However, it is necessary to pay attention to the specific gravity and crystallization temperature. Other salts such as LiCl, NH ₄ Cl,
NH ₄ NO ₃ , (NH ₄ ) ₂ SO ₄ , Na ₂ CO ₃ , NaCr ₂ O ₇・
_2H2O , _NaBO2 , _NaNO3 , _NaBO3 , _{Na2SO4 ,}
Na ₂ SO ₃ .7H ₂ O, Na ₂ S ₂ O ₃・5H ₂ O, Na ₂ HPO ₄・
12H ₂ O, K ₄ Fe (CN) ₆・3H ₂ O, CaSO ₄ , Ca
(C ₂ H ₃ O ₂ ), Ca (CHO ₂ ) ₂ , Ca (NO ₃ ) ₂ , Ca
( _CH2OH (CHOH) _4COO ) ₂ , _MgCl2 , _MgSO4 ,
Mg( _{C2H3O2 ) ,} Mg( _CHO2 ) ₂ , Mg( _NO3 ) ₂ , Mg
( _CH2OH (CHOH) _4COO ) ₂ , _BaCl2 , Ba(OH) ₂ ,
BaSO ₄ , ZnCl ₂ , ZnNO ₃ , Zn(OH) ₂ , ZnSO ₄ ,
_AlCl3・_6H2O , Al(OH) ₃ , _Al2 ( _SO4 ) ₃ , Al
( _CH3CO2 ) ₃ , _FeCl3・_6H2O , _Fe (OH) ₃ , _Fe2
(SO ₄ ) ₃ , Fe(NO ₃ ) ₃ , Cr(NO ₃ ) ₃ , Cr(CH ₃ CO ₂ ) ₃ ,
_CrBr3 , _CrCl3 , Cr(OH)( _NO3 ) ₂ , Cr(OH) ₂
( _NO3 ), _SnCl4 , _AgNO3 , _FeCl2, etc., but are not particularly limited to these. These salts are not limited by their solubility; they may be present as solids in the finishing fluid if measures are taken to minimize formation damage. . The most important features of SEC are its ability to thicken, reduce water loss, It must be stable without impairing its clay dispersion ability. Another characteristic is that HEC (hydroxyethyl cellulose), which has been commonly used in the past, has extremely high foaming properties. In this respect, SEC used in the present invention has no foaming properties at all, so it can be said that it has excellent properties in the high specific gravity applications of the present invention. Furthermore, SEC is harmless to the human body, easy to handle, and therefore free from environmental pollution concerns. It is also easier to transport than HEC. The effects achieved by the present invention are summarized as follows. (1) Even in highly concentrated (10,000 ppm to saturated) finishing fluids containing at least one monovalent salt or polyvalent salt, it exhibits excellent thickening properties without forming any insoluble matter. (2) The system described in (1) shows an extremely excellent ability to reduce water loss. (3) Acts as an excellent dispersant in the system described in (1). (4) The system described in (1) has no foaming at all and is very advantageous in terms of operation (liquid production). No need for antifoaming agents or corrosion inhibitors. (5) The system described in (1) has a wide PH range (PH = 1 to
13) has little viscosity drop, which means it has excellent PH resistance. (6) In the system described in (1), SEC is less likely to be degraded by enzymes, unlike xanthan gum and guar gum. Next, examples of the present invention will be shown, but the present invention is not limited thereto. (However, % and parts indicate weight basis.) Example 1 NaCl, KCl, CaCl ₂ , AlCl ₃ , Al ₂ (SO ₄ ) ₂ of 3
Aqueous solutions of 10% by weight and 10% by weight were prepared, added and dissolved in each solution so that the polymer concentration (anhydride basis) was 1%, and the viscosity was measured using a B-type viscometer. The results are shown in Figure 1. The degree of substitution (DS) of the sodium salt of sulfoethylcellulose (Na-SEC) in the present invention is 0.90,
The viscosity of a 1% aqueous solution is 149 (cp). Control sodium salt of cellulose sulfate (Na−
CS) has a DS of 0.87 and a 1% aqueous solution viscosity of 142 (cp). Further, as a control, the sodium salt of highly substituted carboxymethyl cellulose (Na-CMC), which has been conventionally used as a salt-resistant salt, has a DS of 1.07 and a 1% aqueous solution viscosity of 121 (cp). Na-CS was used as a control because it was expected to be equivalent in performance to SEC since it is structurally similar to SEC of the present invention. As is clear from Figure 1, Na−CMC is Na ⁺
In the presence of monovalent cations such as Ca ^{2+ and} Al 3+, it dissolves almost completely, and the viscosity does not decrease significantly as the salt concentration increases from 2wt% to 10wt%, but in the presence of Ca2 ⁺ and ^Al3+ , It combines with these cations and becomes an insoluble substance. Therefore, the viscosity decrease is significant. In addition, Na-CS exhibits a severe viscosity decrease (due to the formation of insoluble matter) in any aqueous solution system. On the other hand, the Na-SEC of the present invention does not form any insoluble matter even in the presence of divalent or trivalent cations and exhibits good solubility. This shows that the SEC of the present invention has excellent salt resistance and is also excellent as a thickener. Example 2 Example 1 shows salt tolerance up to a salt concentration of 10%, but in this example, various inorganic salts were used to create several aqueous solutions with concentrations ranging from 5% to saturation. , this and 1% polymer (Na-SEC,
The compatibility with an aqueous solution of HEC (sodium salt of carboxymethyl hydroxyethyl cellulose (Na-CMHEC)) was observed. The experimental method was to place 10 cm ³ of each of the above salt concentration aqueous solutions in a test tube, and add 1 cm ³ of 1% polymer aqueous solution into the test tubes.
was added, and the presence or absence of undissolved matter formation after stirring was examined.
The results are shown in Table-1. The DS of Na-SEC in the present invention is 2.45, and the viscosity of a 1% aqueous solution is 12 cp. Control HEC (molar degree of substitution of ethylene oxide
A 1% aqueous solution of 2.0) is 10 cp. Substitution degree of carboxymethyl group of Na-CMHEC (molar substitution degree of ethylene oxide 2.0) = 0.30,
A 1% aqueous solution is 15 cp. As is clear from Table 1, HEC is the polymer most often added to finishing fluids, but depending on the type and concentration of inorganic salts, it can create insoluble matter, limiting its use. The same applies to Na-CMHEC. On the other hand, the Na-SEC of the present invention does not form an insoluble substance with at least any of the inorganic salts (monovalent cations to trivalent cations) listed in the table. Furthermore, the fact that it has good solubility even in inorganic salts shows the superiority of the salt resistance performance of the present invention.

[Table] 〓Note〓 Polymer solubility ◎〓Extremely good solubility.
△〓Some insoluble matter is formed.
×= Insoluble matter is formed.
Example 3 1% polymer (Na-SEC, Na-CMC, Na-
Using H ₂ SO ₄ or NaOH as CS), we observed the decrease in viscosity when the pH was varied. A B-type viscometer was used to measure the viscosity, 25.0±0.5
Measured at °C. The results are shown in Figure 2. The DS of the polymer Na-SEC according to the present invention is
The viscosity of the 0.55,1% aqueous solution is 1130 cp. The DS of the control Na-CS is 0.53, and the viscosity of 1% aqueous solution is
1115cp, and the control Na-CMC DS is 0.55, 1
% aqueous solution viscosity is 1080 cp. As is clear from Figure 2, in Na−CMC, PH
= 6.0 to 11.0, and in the range of PH = 4.5 to 10.0 for Na-CS, the viscosity is stable, in other words, no decrease in viscosity occurs, but outside this range there is a significant decrease. on the other hand,
In the pH range of 1 to 13, Na-SEC of the present invention has
It can be confirmed that there is almost no decrease in viscosity and that it has a wide range of PH resistance. However, SEC with a low degree of substitution, which is outside the scope of the present invention, for example, about 0.35, does not cause a decrease in viscosity due to PH change, but the solution contains many insoluble substances (free fibers), which cause formation It is not recommended for use in finishing fluids as it may cause damage. Example 4 10, 20, 40, 60 containing 3% CaCO ₃ (solid matter)
%, _polymer (Na−
SEC, HEC, Na-CMHEC, Na-CMC) were added and dissolved to a concentration of 2 ppb (pounds per barrel) = 0.57%, and a filtration test was conducted. The results are shown in Figure 2. The filtration test followed the API (American Petroleum Institute) method. The DS of Na-SEC according to the present invention is 1.05, and the viscosity of a 1% aqueous solution is 3900 cp. The control HEC has a molar substitution degree of ethylene oxide of 2.0, a 1% aqueous solution viscosity of 4500 cp, and a Na-
The molar substitution degree of ethylene oxide in CMHEC is 2.0,
The degree of substitution of carboxymethyl group is 0.60, the viscosity of 1% aqueous solution is 4000 cp, the DS of Na-CMC is 1.00, and the viscosity of 1% aqueous solution is 4200 cp. As is clear from Figure 3, it was confirmed that the Na-SEC according to the present invention has superior water loss reduction ability in a wide range of salt concentrations compared to the controls HEC, Na-CMHEC, and Na-CMC. can. The smaller the water loss (WL), the better. Example 5 4, 15, 30, 60% and saturated Peladow (CaCl ₂
To 350 ml each of industrial grade, Dow Chemical Co.) aqueous solution and ZnBr ₂ aqueous solution, add Na-
Three types of polymers, SEC, HEC, and Na-CMHEC, were added individually to a concentration of 4 ppb = 1.14%, and mixed with a multimixer (manufactured by Balloid, USA).
After stirring at 10,000 rpm for 30 minutes and standing overnight, the volume increase due to residual foam was measured. Table 2 shows the results.
It was shown to. The DS of Na-SEC of the present invention is 0.50, the viscosity of 1% aqueous solution is 3000 cp, and the degree of molar substitution of ethylene oxide of Na-CMHEC of the present invention is 1.7, the degree of substitution of carboxymethyl group is 0.50, and the viscosity of 1% aqueous solution is 3150 cp.
The degree of molar substitution of ethylene oxide in HEC is 2.0, and the viscosity of a 1% aqueous solution is 2900 cp. When the value shown in Table 2 is 1 (=volume after stirring/volume before stirring), it indicates that no bubbles are generated at all, or that bubbles disappear quickly even if bubbles are generated. The larger the value, the more difficult the stirring operation during polymer dissolution becomes, which is undesirable. As is clear from Table 2, Na-CMHEC and HEC have relatively good solubility even in the presence of Peladow or ZnBr ₂ , but they generate a large amount of bubbles during dissolution and stirring, which do not disappear easily. As a result, a large amount of atmospheric oxygen enters the completion fluid, resulting in oxygen-induced corrosion of machinery and equipment, and reduces the density of the completion fluid, thereby increasing the risk of wellbore collapse. There are other difficulties involved. On the other hand, the Na-SEC of the present invention is based on Peladow and ZnBr ₂
There is little foaming over a wide concentration range of
It has advantages such as no need for antifoaming agents.

[Table] 〓Note〓
Volume after stirring (ml)
Numbers in Table-2:

Claims (1)

[Claims] 1 Boring finishing fluid containing at least one monovalent salt or polyvalent salt has a degree of substitution (DS) of 0.5 to
2.5 and a 1% (by weight) aqueous solution viscosity of 5 to 5000 (cp).