JPS644977B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to cement compositions for the petroleum industry. This cement composition, whose components are combined in a unique way, is characterized by the so-called "gas channeling phenomenon" (gas-channeling phenomenon) by an entirely novel mechanism.
channelling phenomenon) as soon as it occurs. [Conventional technology and problems to be solved] The concept of gas passage (forming a pressurized gas passage in a cemented annular part) is widely known to experts involved in cementing oil wells. ing. Gas channeling occurs when an oil well traverses a pressurized gas pocket in the annular space between the traversed rock and the well casing.
It is already known that this is after the cement slurry has been injected. The gas passage phenomenon occurs after the cement slurry has solidified to some extent and before it has solidified. Once the cement slurry has solidified to some extent, the hydrostatic pressure of the cement column is no longer completely applied to the zone of the gas pocket, but the degree of solidification is still not sufficient so that the gas forms a passage through the cement slurry. be. The pressurized gas flows through the cement column or between the cement and the traversed rock as setting progresses. For this reason, a large number of channels are formed in the cement. These passages may even reach the surface of the earth. This phenomenon is facilitated by the shrinkage of cement. In addition, if the rock is porous, fluid loss from the cement slurry may also help. As described above, the gas passage phenomenon is a very serious problem that is related not only to cement embrittlement but also to safety on the ground. The number of repeated attempts to solve this problem is a testament to its seriousness and the longstanding interest of the oil industry. Also, whether these attempts result in complete failure;
The magnitude of the difficulty involved is that it was at best a partial failure. And this problem has never been completely overcome, even at relatively low gas pressures, even though all oil companies would like to overcome it. It should also be noted that the inherent conditions inherent in this technique of cementing wells further complicate the solution to the problem. In particular, when using additives, the slurry
pumpable over several hours
One can list the conditions that must be in the state. There is also a general requirement that the properties of the additive and its effectiveness must not be altered by the severe temperature and pressure conditions at the bottom of the oil well. On the other hand, it is necessary to maintain good pressure strength and good rheological properties to prevent free water formation and fluid loss. Thus, when considering the large number and complexity of parameters involved in cementing, and the contradictory nature of some of them, the oil industry It is not surprising, however, that up to the present time no satisfactory solution to the problem of gas channeling has been found. In the prior art, attempts have been made to increase the viscosity of interstitial water by adding water-soluble polymers, in particular by adding polyethyleneimine or its derivatives. Attempts have also been made to mix in-situ slush-polymerizable monomers (e.g., acrylamide) into the cement slurry before it begins to thicken (thicken), i.e. before gas channeling can occur. , it was not possible to control the polymerization. Thixotropic or expansive cements have sometimes been used, but these have not been fully effective. British Patent No. 1460508 attempts to mix a blowing agent into a cement slurry. However, since this blowing agent is adsorbed on the cement particles, it has not in practice been possible to use it to form stable foams under the action of gas. U.S. Pat. No. 4,304,248 discloses that a gas generating agent that generates gas on-site is mixed with a cement slurry.
A method is described that compensates for the drop in hydrostatic pressure. One of the recommended gas blowing agents is aluminum powder, but this has two drawbacks. One is that the aluminum carrier used is a glycol, and the other is that the gas evolved is hydrogen. Its dangers are widely known. In addition, the generation of gas could not be controlled. That is, if the amount generated was too small, it was not possible to prevent the gas from forming a channel, and if the amount generated was too large, the permeability of the cement slurry became extremely high. [Means for Solving the Problems] As a means for solving the above-mentioned problems, in the present invention, the basic components are hydraulic cement, compatible styrene (70-30% by weight)-butadiene (30-30% by weight). 70
A composition of a cement slurry composition was employed: a latex consisting of a copolymer (% by weight), a latex stabilizer, and water. [Operations and Effects] When considering the matters described in the section of the prior art and its problems, it is clear that the present invention maintains the properties absolutely necessary for cement (pumpability, etc.), and also achieves the same properties. It can be said that it is amazing that some of these problems have been solved by improving some of them and preventing the formation of gas passages even at considerable depths below the earth's surface. In this case, "quite deep" refers to areas where the oil well's temperature is particularly high, above 185°, and can even reach about 485° or above. The composition according to the invention consists of four basic components: (a) Cement (b) Latex (c) Latex stabilizer (d) Water Each component (a), (b), and (c) will be explained below. (a) Cement Cement is a hydraulic cement. This may be of any class among those currently used for cementing oil wells. Hydraulic cement is a cement that is composed of calcium, aluminum, silicone enzymes and/or sulfur compounds and hardens by reacting with water. Things that meet this definition include the following: First, there are the usual cements called Portland cements, such as those with normal hardening speed, Portland cement with fast hardening speed, Portland cement with very fast hardening speed, cement with sulfur resistance, and other cements. Modified Portland cement. Also, cement that is usually called alumina cement, calcium aluminate cement with a high alumina content. Cement containing a small amount of setting accelerator, setting inhibitor, and AE agent, second component (fly ash,
cement containing pozzolan), etc. (b) Latex The latex shall be selected from styrene/butadiene latex. More specifically, it is selected from styrene (70-30% by weight)/butadiene (30-70% by weight) latices that do not contain groups that are incompatible with cement. In determining the above ratio of styrene and butadiene, we take into account the fact that too much butadiene will cause premature coagulation of the latex, and conversely, too much styrene will not form a strong film. is taken into consideration. Until about 10 years ago, latex was used extensively in the oil industry, although its use is much reduced today. In this way, the petroleum industry is working to improve the mechanical strength (compressive strength, tensile strength, etc.) of cement.
Traditionally, latexes have been used in cement; examples of the use of styrene/butadiene latexes for this purpose are described in US Pat. Nos. 3,228,907 and 4,151,150. No. 3,228,907 does not recommend the use of stabilizers and flocculation of the latex is observed. Therefore, the composition recommended by this invention has no effect on the specific phenomenon of gas passage. Additionally, the compositions taught in this patent have proven difficult to infuse by pump. On the other hand, US Pat. No. 4,151,150 proposes adding an interfacial agent (sodium lauryl sulfur salt), but this does not prevent the latex from coagulating. Therefore, the compositions described in this patent also do not have the effect of inhibiting gas passage. Furthermore, the use temperature of the composition is limited to ambient temperature. Belgian patent No. 886819 describes a cement containing latex and wax and having water penetration resistance. However, these characteristics occur because of the addition of wax, not because of the addition of latex. US Pat. No. 3,050,520 recommends the use of latex (polyvinyl acetate) to reduce fluid loss. However, this patent does not explicitly mention the problem of gas passage, and the temperature limit for use of the composition according to this patent is about 122°C. From what has been stated above, (1) latex has been used in the petroleum industry for a long time;
Furthermore, even though the issue of gas channelization was already a focus of concern for those involved in the oil industry, it was inevitable that latex was recommended to prevent this gas channelization (2 ) Some of the compositions that have been recommended in the past have solved the problem of gas passages due to the above-mentioned difficulties in injection, condensation of the latex, and the fact that they can only be used at low temperatures. Things that could not have been done become clear. (c) Latex stabilizer The composition according to the invention must necessarily contain a latex stabilizer. Latex stabilizers have a secondary function as dispersion aids for cement particles. The stabilizers used according to the invention significantly improve the film-forming properties of the latex. This is because the stabilizer allows this film-forming property to be developed only when gas is generated in the slurry (in response only to gas generation). This cement has excellent properties not previously available, that is, a cement that immediately prevents the gas passage phenomenon as soon as it occurs, and has improved other properties (rheological properties, etc.). This is achieved by the composition of the invention because it has the "selective" reaction properties described above. The remarkable nature of this selective latex film-forming reaction is illustrated by the fact that only a few of the stabilizers tested were able to similarly improve latex properties. This is something that can be substantiated. This highly useful stability according to the present invention is achieved by anionic polyelectrolytes, such as
These include melamine formaldehyde resins modified with sulfonic acid or sulfite, formaldehyde/sulfonated naphthalene resins, or condensates of dinuclear sulfonated ferrules and formaldehyde. Preferably, an alkali metal salt of a condensate of mononaphthalene sulfonic acid and formaldehyde is selected, and more preferably a sodium salt is selected. In the prior art, a condensate of formaldehyde and naphthalene sulfonic acid was recommended as a reducing agent to reduce fluid loss. but,
When used alone (U.S. Pat. No. 3,465,825)
It has only mediocre effectiveness, and when used in combination with polyoxyethylene (US Pat. No. 3,998,773) its action is limited to temperatures up to 149°C. Thus, although this type of compound has been recommended in the past, it is by no means due to the very different function it performs in the compositions of the invention ("selective" stabilizer of latex). , it has not been recommended. Additionally, the following was discovered: That is, if an inhibitor is needed to control the setting time of the cement in high temperature applications, certain anionic cement inhibitors (e.g.
Lignosulfonates, partially desulfonated lignosulfonates, or polyhydroxydicarboxylic acids) can partially replace the preferred stabilizers mentioned above. These cement inhibitors have been found to behave similarly to melamine/formaldehyde resins modified with sulfonic acids or sulfites. However, its efficiency is
considerably lower than the latter. Furthermore, the amount of such inhibitor that can be added to the cement is determined primarily by the setting time of the cement and not by the stability of the latex. The ratio of anionic inhibitor to stabilizer therefore depends on the efficiency in each case of the inhibitor in inhibiting cement setting and stabilizing the latex. The compositions of the present invention open up new directions for the control of gas channeling phenomena, which include:
First of all, it allows effective use of the action of the gas itself on the additives in the cement slurry. Furthermore, with the composition according to the invention, the limits of well depth in which gas passage can be controlled have been considerably expanded. This means that the composition according to the invention has at least
This is because it is effective at temperatures up to 212㎓ and considerably higher than that. Conventional cement compositions containing latex are
It could not be used at temperatures above 122°C. Furthermore, it has never been suggested that effective work could be done with this general type of composition at temperatures of 185°C or higher, much less that gas channeling could occur. It was not completely clear to me that there was no such thing. This temperature difference of 65° or more represents a significant advance in well depth to those skilled in the art. Because in this field, only 2~
It is no exaggeration to say that even a difference of three degrees is of great significance. Furthermore, according to the present invention, it has been found that the cement slurry composition described above can be used even at even higher temperatures. i.e. about 230
It has been found that it can be used in the temperature range from 0 to the decomposition temperature of latex. The decomposition temperature of latex is styrene (50% by weight)/butadiene (50% by weight).
(% by weight) for latex, it is approximately 550〓. When using in such a high temperature area, the above (A) ~
In addition to the four main components (cement, latex, latex stabilizer, and water) shown in (D), it is preferable to mix a specific silica component. The size of the silica is, for example, 20 to 200 mesh, and the particle size distribution is preferably similar to that of the cement powder used. If the size of the silica is selected as described above, the silica has no effect on the quality of the latex and therefore has no effect on the prevention of gas passage. Thus, according to an advantageous variant embodiment of the invention, the invention provides five basic components as a cement slurry composition for cementing oil wells.
Relating to a combination of (a) cement, (b) latex, (c) latex stabilizer, (d) water, and (e) silica powder, passage of pressurized gas until the temperature is approximately 550°C. , which enables control. The temperature of 550㎓ is the temperature at which the decomposition (in air at atmospheric pressure) of the main latexes used begins. According to this variant embodiment of the invention, the following components are mixed: - 20-50% by weight of silica powder relative to cement;
Preferably 30-35% by weight of silica powder (hereinafter referred to as
BWCO (by weight
of cement), - 20-30% BWOC of latex, - 3-15% by weight of latex stabilizer, based on the latex. The above latex percentages, also referred to below, are based on the total amount of latex and not on the active polymer component. The compositions according to the invention may also contain conventional cement additives, in particular antifoaming agents (e.g. based on triptyl phosphate or polypropylene glycol) and setting inhibitors (hereinafter referred to as inhibitors). good. Other antifoaming agents include dibutyl phthalate and polysiloxane. Inhibitors include lignosulfonates, partially desulfonated lignosulfonates, polyhydroxymonocarboxylic acids or polyhydroxydicarboxylic acids (these are high temperature inhibitors, among these are tartaric acid, tartrate , D-gluconic acid, D
-gluconate, hebutonic acid and heptate). Other conventional additives for cement include: ● Accelerators: calcium salts ● Lightening agents: pozzolan, fly ash, diatomaceous earth, silicates, expanded perlite, jilsonite, charcoal, activated carbon, microscopic spheres of glass or ceramic, etc. ● Bulking agents: iron oxides, titanium, barite, etc. According to the present invention, the composition ratios of various components are as follows (expressed in weight % unless otherwise specified) ●% latex/cement: 5-30, however, the concentration of latex is: Directly related to operating temperature. If the temperature is 80-120〓, 5-10%, if the temperature is 120-180〓, 10-15%, if the temperature is 180-200〓, 15-20%, if the temperature is 200-230〓 When the temperature is about 230 degrees, it is preferably 20-25%, and when the temperature is about 230 degrees, it is preferably 20-30%. ●% stabilizer/latex: about 1-20, preferably 3-15. ●% Inhibitor/Cement: Depending on temperature (optional)
0.05−4. ●% Defoamer/cement: 0.045-0.067gal/sk (optional). • The preferred moisture content is approximately 30-60% BWOC, less the amount of liquid additives, and preferably 38-46% for Bortland cement. When Rhodophas SBO12 latex was used, good results with good durability were obtained as shown below. [Embodiments] Hereinafter, embodiments of the present invention will be described in conjunction with the accompanying drawings. Figure 1: Scanning electron microscope [magnification 5000] shows
Observed cement composition. ● Semoil Class G Cement ● Rhodopas SBO12: 14% BWOC ● Moisture without stabilizers, minus amount of latex: 44% BWOC and then lyophilized). Figures 2 and 3: Scanning electron microscope [2500x magnification in Figure 2, 10000x magnification in Figure 3]
Observed cement composition. ● Deitzkerhoff Gulf Class G Cement ● Rhodopas SBO12: 14% BWOC ● Stabilizer: 8% by weight of latex (as defined on the following page) ● Moisture less the amount of liquid additives: 44%
BWOC (This cement sample was stored at 135°C for 10 days after hydration made pumping impossible and then lyophilized) Figure 4: Composition thickening time
well simulation test (this is listed in the table that follows). The conditions for the simulation test are as follows. ●Surface temperature 80〓 ●Surface pressure 1500Psi ●Bottom hole pressure 10200Psi ●Bottom hole circulation temperature 185〓 ●Time to reach final temperature 44 minutes ●Heating rate 2.38〓/min ●Time to reach final pressure 44 minutes (API Schedule No.7g5 ) (Pressurized Consistency Meter Tests) Tests 2, 5 and 8 were conducted under atmospheric pressure. FIG. 5: Diagram of the gas passage test tank used in Example 3. Each reference symbol in this figure refers to the following: E: Recorder I: DP tank (see Example 3) A: HP tank (see Example 3) □P: Water trap The meanings of other reference symbols are already known to the person skilled in the art. . V: Valve T: Pressure transducer P: Pressure regulator M: Manometer F: Flowmeter H: Hose Figure 6: Cement composition observed by scanning electron microscope [DP24 slurry; magnification 5000]. ●Semoil Class G Cement ●Defoamer: 0.05gal/sk ●DOW465 Latex: 18% BWOC ●Stabilizer: 6% by weight of latex (defined below) ●Moisture: 44 less the amount of liquid additive %BWOC Figure 7: Cement composition observed with a scanning electron microscope (10,000x magnification). ● Deitzkerhof North Class G Cement ● Defoamer: 0.05g/sk ● Rhodopas SBO12: 19% BWOC ● Stabilizer: 8% by weight of latex (defined on the following page) ● Inhibitor: 0.1% BWOC ● Moisture: 44% BWOC after subtracting the amount of liquid additives [The samples shown in Figures 6 and 7 were tested for gas channeling with cement hardened 185〓 in a tank without gas flow. It was then freeze-dried. ] Figures 8 and 9: Cement compositions observed under a scanning electron microscope [Figure 8 at a magnification of 2500 and Figure 9 at a magnification of 5000]. ● Deitzkerhof North Class G Cement ● Defoamer: 0.05g/sk ● Litex6301: 19% BWOC ● Stabilizer: 15% by weight of latex (as defined below) ● Inhibitor: 0.1% BWOC ● Moisture : 44% BOC after subtracting the amount of liquid additive [The samples shown in Figures 8 and 9 are 185〓 where cement hardening has occurred, after conducting a gas passage test,
It is freeze-dried and comes out of a tank that is flushed with gas. ] Figure 10: Cement composition observed with a scanning electron microscope [magnification: 2500]. ●Semoil Class G Cement ●DOW465 latex: 19% BWOC ●Stabilizer: 6% by weight of latex ●Moisture: 44% BWOC minus the amount of liquid additive ●Defoamer: 0.05 gal/sk [185 when cement hardens A sample from a DP tank with gas flowed through the gas passage test and freeze-drying.] Preferred compositions are: ●API class G cement, ●Latex: Rhodophas SBO12 (5 to 30% by weight of cement) (%), ●Stabilizer: Sodium salt of the condensate of formaldehyde and β-naphthalene sulfonic acid (3-15% by weight of latex), ●Clear water: 44% after subtracting the amount of latex and stabilizer.
I am BWOC. The concentration of latex depends on the temperature: 85〓 5-10% 122〓 10-15% 185〓 15-20% 212〓 20-25% 230〓 20-30% According to the invention, fresh water and seawater Brine from 0% to 37% NaCl (saturated) can be used to mix. Example 1 Stabilizing latex in cement slurry. The stability of latex in cement slurry,
Evaluation was made under the following two conditions (a) and (b). (a) Fluid cement: Measure the rheological properties of cement slurry after stirring at a constant temperature for a certain period of time. (b) Set and hardened cement: A cement sample is freeze-dried and then visually observed using a scanning electron microscope. Let's start with (a). Rheological properties The cement slurry is mixed at room temperature in accordance with API (American Petroleum Institute) specification RP10B section 5 using a high shear rate mixer (wearing mixer type) and then mixed according to API specification RP10B section 5. Stirring was carried out in accordance with RP10B section 9 for 20 minutes at the specified temperature in an apparatus known as a Chandler type atmospheric consistency meter. The rheological parameters were then measured with a FANN35V-G viscometer at the same temperature according to API standard RP10B, Follow-up H. If the latex is completely unstable, the cement slurry will remain stable when removed from the consistency meter.
It is also unpourable even before the end of stirring. This means that the consistency of the slurry as measured by the calibration spring or potentiometer is very good.
This is indicated by 100 units or more. Since not all rheological parameters of cement slurry can be measured with FANN35V-G, the unpourability of the slurry
is the criterion for determining instability. If the cement slurry is pourable,
Rheological parameters are measured and criteria regarding latex stability are based on the values of rheological parameters such as plastic viscosity and yield stress. The table below shows the effect of stabilizers on the stability of latexes in cement slurries containing various polystyrene-butadiene latexes with or without stabilizers at various temperatures. Based on the flow characteristics of cement slurry, it is shown whether the The latex used was as follows. (weight%)

[Table] The antifoaming agent used was a polyglycol with an average molecular weight of 4000. The stabilizer used is the sodium salt of a condensate of formaldehyde and β-naphthalene sulfonic acid. Sedimentation tests were conducted on the same cement slurry at the same time. According to it, the non-flowability of the slurry is directly related to the flocculation of the latexes as well as the strong interaction between the flocs of these latexes and the cement grains, and It was found that it produced a high gel structure. Next, let us discuss (b). Observation using a scanning electron microscope A slurry of cement modified with latex with or without stabilizers was
After stirring until completely concentrated, lyophilize and
Next, it was observed using a scanning electron microscope. Some of these slurries were stored at the above temperatures for 10 days and then lyophilized and tested. When latex is used without adding stabilizers,
When latex is heated and agitated, it solidifies very quickly. This coagulation is manifested by flocculation of latex particles on and between cement grains (first
(Figure), strong bridging is formed between the cement grains and the latex flocs. In this way, a gel structure is formed so that the cement slurry can no longer be poured. On the other hand, if the latex is stabilized with a stabilizer as described above, the latex will
Even after 10 days, it still maintains the state of individual polymer particles. This is particularly clearly shown in FIGS. 2 and 3. In these figures,
No latex flocs or latex films are visible, but only small polymer particles of 0.2-0.4μ can be seen uniformly distributed on and between the normally hydrated cement grains. . Example 2 Properties of cement slurry The properties referred to here include fluid loss adjustment,
Free water control and pumping time. All of these properties are measured using specific equipment and regulations specified by the American Petroleum Institute (API Standard RB10, 1st edition January 1982). Fluid loss test, free water test and thickening time test (injection time)
A cement slurry composition containing a polystyrene-butadiene latex stabilized with the sodium salt of a condensate of formaldehyde and β-naphthalene sulfonic acid was tested. A comparative test was attempted using the same cement slurry without the addition of stabilizers, but it was not possible to perform a test based on anything other than pouring time.
This is because fluid loss and free water tests cannot be performed on unpourable slurries, as they are usually performed after stirring the slurry for 20 minutes at a suitable temperature. The compatibility with inhibitors and the possibility of adjusting the injection time were also investigated using lignosulfonate type inhibitors. Data to compare this result with a conventional cement slurry with no added latex at 185% - a good quality, fluid loss adjustment of 150% in 30 minutes.
It is expressed by a filtration rate of less than m. -Highly good quality, fluid loss adjustment in 30 minutes
It is expressed by a filtration rate of 100ml or less. - The preferred content of free water is up to 1.4% by volume of the slurry. - The thickening time curve (injectability curve) should be relatively flat until cement thickening [there should be no premature plateaus due to gelation], and It is necessary to check that the thickening of the cement is due to hydration of the cement and not due to the development of a gel structure due to coagulation of the latex. To do this, when the cement slurry reaches a non-pourable state (corresponding to a consistency of 100 units),
Keep it under the same temperature and pressure for an additional 30 minutes.
If the thickening is due to hydration of the cement, then after 30 minutes the cement should have more or less the consistency of friable soil or rock, and no longer have the consistency of a paste. The table below shows test results regarding fluid loss, free water, and concentration time. The test is
It was held at 185〓. Concentration time curve (injectability curve)
is shown in FIG. The antifoaming agent used was a polyglycol with an average molecular weight of 4000. The inhibitor used is a lignosulfonate derivative. Main conclusions: - The control of fluid loss and free water is always good (<100 ml per 30 minutes). - If no stabilizer is added, the latex is heated and
When stirred, it solidifies in the cement slurry and forms a gel structure. This gel formation can be seen by plateaus indicating gelation on the injection mold curve. This gel plateau is at a consistency of about 60 units, indicating that the slurry is not flowable and is nearly pourable. In this case, the cement is still a gel even after reaching the maximum recordable consistency (100 units consistency). With latex and stabilizer no gelation occurs and in this case the maximum consistency recorded
Hydration of cement is shown. Polystyrene-butadiene latexes stabilized with the above-mentioned stabilizers do not retard the setting of the cement and the thickening time can be perfectly controlled by conventional inhibitors used in normal concentrations (e.g. within 4 to 5 hours). Example 3 Gas passage prevention properties of latex modified cement slurry. The gas channeling inhibition properties were tested using an experimental device specifically designed for this purpose, called a gas channeling test tank. This device, shown schematically in FIG. 5, consists essentially of two separate cylinders filled with cement. In the first cylinder (referred to as the HP bath), the decrease in the pore pressure of the cement is measured over time when a constant head pressure is applied to the cement by a piston. On the other hand, in the second cylinder (called the DP tank), when the pore pressure of the cement drops sufficiently in the first cylinder, the flow property of the gas in the second cylinder is
Measure under constant differential pressure. If all other parameters are constant from test to test, the gas passage prevention properties of the cement slurry can be readily determined by the maximum gas flow rate recorded. The test conditions are as follows. ●Temperature: 185〓 ●Head pressure in both tanks: 40 bar ●Back pressure in DP tank: 35 bar ●When the cell pressure of the cement reaches 30 bar, i.e. when it drops from 40 bar to 30 bar, let the gas flow . The antifoam agent consists of a polyglycol with an average molecular weight of 4000. The thixotropic liquid additive consists of an aqueous liquid composition of iron sulfate and aluminum sulfate. This is described in UK Patent No. 2030976. The table below shows conventional slurry (x), slurry according to the invention, slurry without stabilizer (x)
×), slurry containing nonionic surfactant ()
This shows the results of tests conducted on Main Conclusions - Conventional cement slurries (eg without added latex) have high gas passage rates (between 300 and 1100 scm ³ /min) and no gas passage inhibition properties. ●Cement slurry with 19% BWOC latex and appropriate amount of stabilizer has very low flow rate (3-25scm ³ /min) and has excellent gas passage prevention properties. ● For cement slurries containing latex but without added stabilizers, the flow rate is moderate (100scm ³ /
minute). Therefore, when the latex is not stabilized, the mechanism of film formation due to gas flow does not occur, and an improvement over conventional cement slurries is that the latex precipitates (linear lumps) are absorbed into the cement pores. It appears that the only effect is to partially unevenly block the cement (which naturally reduces the permeability of the cement somewhat). Example 4 Mechanism for preventing gas passage using latex. The mechanism of preventing gas passage using latex will be illustrated using a scanning electron microscope.
Samples taken from the HP tank (gas does not flow) and the DP tank (gas flows) are tested for gas passage, then freeze-dried (the cement has hardened at this time), and then these samples are Freeze-dried samples were examined under an electron microscope. Figures 6 and 7 are for samples taken from the HP bath, and it is clearly seen that the latex particles are fully stabilized within the hardened cement in the absence of gas. on the other hand,
Figure 8 shows a sample coming from a DP tank with gas flowing through it,
In FIGS. 9 and 10, it can be seen that a film was formed due to dehydration due to the passage of gas. Particularly in FIGS. 8 and 9, the formation of multiple latex film barriers or sheets can be seen. These film barriers progressively slow gas passage until they completely prevent gas passage. In any gas channeling test performed using a (styrene-butadiene) latex stabilized with a condensate of naphthalene sulfonic acid and formaldehyde, the interface between the cement and the metal wall during the test was It is also noteworthy that no gas flow was observed. This is because this would not happen if a conventional slurry was used. This property of improving the cement-to-metal bond was also demonstrated in the case of the latex stabilization method by shear-bond strength measurements. Example 5 (Comparative Example) In this example, cement compositions containing different types of latex were used. However, all compositions contain a formaldehyde-naphthalene sulfonic acid stabilizer according to the invention. The results shown in the table below show that of the various types of latices tested, only styrene-butadiene latex can be used.
This is because, with other latexes, the slurry has no fluidity, which is clearly a disadvantage that should be prohibited. Example 6 The following slurry was tested at 212〓. ●Semonil Class G Cement ●Defoamer: 0.05g/sk ●Rhodopas SBO12 latex: 23% BWOC ●Stabilizer (formaldehyde-naphthalene sulfonate): 5% by weight of latex ●Fresh water: 19% BWOC ●Maximum gas flow rate :2scm ³ /min The test results are good and the composition according to the invention can be used even at 212㎓. Furthermore, the behavior of the cement during testing predicts the possibility of use at even higher temperatures. Example 7 (comparative), Example 8, Example 9 These examples relate to the addition of silica powder to enable use at higher temperatures. The table below shows the cement slurry composition used and the test results obtained. The tank shown in Figure 5 was used for this test. The test conditions are as follows. ●Temperature: 266〓 and 320〓 ●Head pressure of two tanks: 40 bar ●Back pressure of DP tank: 20 bar ●When the pore pressure of cement reaches 18 bar,
That is, when the pressure drops from 40 bar to 18 bar,
Let the gas flow. Main Conclusions The conventional cement slurry (Comparative Example 7) without any latex has a very high gas passage rate and does not have gas passage blocking properties. On the other hand, a cement slurry containing appropriate amounts of latex and stabilizer can be used even at a temperature of 266°
In the case of 320〓, the gas flow rate was also 0, and excellent gas passage prevention properties were exhibited (Examples 8 and 9). Moreover, thermogravimetric analysis and thermostratigraphic analysis show that the preferred latex recommended by the present invention, polystyrene-butadiene containing styrene (70-30% by weight) and butadiene (30-70% by weight), has a temperature of 518 Degradation for the first time
I found out that it was starting to happen. Other components contained in the cement composition of the present invention, such as cement, stabilizers, water, etc., do not decompose under the influence of temperature until at least 572㎓.
Temperatures higher than 320°C are applicable to this embodiment, with the upper limit of application being determined by the decomposition temperature of the latex used. In this case, the upper limit is 518〓. Since the composition of the present invention can be used even at such high temperatures, it has made it possible for the first time to efficiently treat deep wells and geothermal drilling wells. Example 10 Stabilization of latex in cement slurry at elevated temperatures. The stability of latex in cement slurry,
The rheological properties of the cement slurry were measured and evaluated as shown in the table. First, the amount of anionic inhibitor was adjusted so that the cement thickening time was 6 hours, and then the amount of stabilizer was determined so that the latex was optimally stabilized.
When using the optimum amount of inhibitor, the amount of stabilizer can be reduced by 60%
It turns out that it can be reduced.

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【table】 [Brief explanation of the drawing]

Figures 1, 2, and 3 are diagrams showing the composition of cement observed using a scanning electron microscope, Figure 4 is the result of an oil well simulation test of the composition concentration time, and Figure 5 is the result of an oil well simulation test. Diagrams of the gas channeled test tank used in Example 3, FIGS. 6-10, show the cement composition as observed under a scanning electron microscope at different magnifications.

Claims (1)

[Claims] 1. A cement slurry composition for cementing oil or geothermal wells that improves the properties of the cement and prevents the passage of pressure gas within the cemented annulus even at high temperatures:
A cement slurry composition characterized in that the basic components are a hydraulic cement, a latex consisting of a compatible styrene (70-30% by weight)-butadiene (30-70% by weight) copolymer, a latex stabilizer and water. . 2. Portland cement, where the hydraulic cement has or does not contain fly ash, pozzolan and similar substances as secondary components;
The cement slurry composition according to claim 1, which is an alumina cement or a special cement. 3. A cement slurry composition according to claim 1, characterized in that the styrene-butadiene copolymer does not contain groups that are incompatible with cement. 4. A cement slurry composition according to claim 1, wherein the styrene-butadiene copolymer is a copolymer containing about 50% by weight styrene and about 50% by weight butadiene. 5. The cement slurry composition of claim 1, wherein the styrene-butadiene copolymer is a copolymer containing about 66% by weight styrene and about 33% by weight butadiene. 6 Latex stabilizers include anionic polyelectrolytes such as melamine-formaldehyde resins modified with sulfonic acids or sulfites, formaldehyde-sulfonated naphthalene resins, condensation of formaldehyde with sulfonated phenols having two nuclei, etc. 2. The cement slurry composition according to claim 1, wherein the stabilizer is selected from the group consisting of lignosulfonates, lignosulfonates, and partially desulfonated derivatives thereof. 7. The cement slurry composition according to claim 1, wherein the latex stabilizer is an alkali metal salt (preferably a sodium salt) of a condensate of mononaphthalene sulfonic acid and formaldehyde. 8. The ratio of latex to hydraulic cement is about 5 to 30% by weight, preferably about 5 to 10% by weight for a temperature of about 80 to 120〓, and 10 to 10% for a temperature of about 120 to 180〓. 15% by weight, 15-20% by weight for a temperature of about 180-200〓, 20-25% by weight for a temperature of about 200-230〓, 20-20% for a temperature of about 230〓 up to the decomposition temperature of the latex 30% by weight of the cement slurry composition according to claim 1. 9 The ratio of latex to hydraulic cement is 20 to 30% by weight, and this latex contains 20 to 50% by weight of silica powder with a particle size distribution comparable to that of cement powder.
A cement slurry composition according to claim 1, characterized in that it comprises: 10 The ratio of latex stabilizer to latex is about 1 to 20% by weight, preferably 3 to 15% by weight.
The cement slurry composition according to claim 1, characterized in that: 11 The proportion of water, whether fresh water or seawater or saltwater, is determined by the American Petroleum Institute (American Petroleum Institute).
Petroleum Institute).
A slurry composition of the cement according to claim 1, characterized in that the proportion less the total water content contained in the latex and latex stabilizer is preferably about 30-60% by weight relative to the hydraulic cement. thing. 12 Basic component composition: Hydraulic cement: American Petroleum Institute (API)
Class G cement, latex: styrene-butadiene (50:50) copolymer, about 5-30% by weight of cement, latex stabilizer: latex with sodium salt of a condensate of β-naphthalene sulfonic acid and formaldehyde. Fresh water: about 30 to 60% by weight of the cement based on the amount of water after deducting the total water content contained in the latex and latex stabilizer. A cement slurry composition according to item 1. 13 The basic component composition is: Hydraulic cement: API class G cement, Silica powder: 30 to 35% by weight based on cement, Inhibitor: 0.6 to 1.5% by weight based on cement, lignosulfonate, Latex: Based on cement Approximately 23~28
wt% styrene-butadiene (50:50) copolymer, latex stabilizer: 3 to 6 to latex
% formaldehyde-naphthalene sulfonate, water: 56 to 60% by weight of the cement after subtracting the water content of the latex and stabilizer, the cement according to claim 1. slurry composition. 14 Components other than the basic components include antifoaming agents, inhibitors,
The cement slurry composition according to claim 1, which is one or a mixture of two or more of a lightening agent, a weighting agent, and other additives for cement.