阅读说明：本技术 高密度水泥浆用高温稳定剂及其制备方法 (High-temperature stabilizer for high-density cement slurry and preparation method thereof ) 是由 刘文明 吴朝明 齐奔 林志辉 付家文 赵殊勋 李小林 凌勇 陈绪 王翔宇 李中国 于 2020-07-15 设计创作，主要内容包括：本发明公开了一种高密度水泥浆用高温稳定剂及其制备方法,其中高温稳定剂包括以重量份计的76～84份的膨润土、10～14重量份的改性定优胶、6～10重量份的交联共聚物；改性定优胶采用苯乙烯磺酸钠和2-丙烯酰胺-2-甲基丙磺酸对定优胶进行接枝共聚得到；交联共聚物由2-丙烯酰胺基-2-甲基丙磺酸、丙烯酰胺、二甲基二烯丙基氯化铵、N-乙烯基己内酰胺和二乙烯基苯共聚而成的交联共聚物,其分子量为7×10<Sup>5</Sup>～9×10<Sup>5</Sup>；该高温稳定剂具有低温高粘、高温增粘的特点,显著改善水泥浆高温稳定,解决现有水泥浆高温稳定性差的问题,且对水泥浆综合性能无不良影响,满足现场施工需求；另外,该稳定剂在制备方面制备方法简单,条件以控制,成本低,具有市场推广应用前景。(The invention discloses a high-temperature stabilizer for high-density cement slurry and a preparation method thereof, wherein the high-temperature stabilizer comprises 76-84 parts by weight of bentonite, 10-14 parts by weight of modified diutan and 6-10 parts by weight of cross-linked copolymer; modified pyridineThe excellent glue is obtained by graft copolymerization of sodium styrene sulfonate and 2-acrylamide-2-methylpropanesulfonic acid; the crosslinked copolymer is prepared by copolymerizing 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, dimethyl diallyl ammonium chloride, N-vinyl caprolactam and divinylbenzene, and has a molecular weight of 7 × 10 5 ～9×10 5 (ii) a The high-temperature stabilizer has the characteristics of high viscosity at low temperature and high-temperature tackifying, obviously improves the high-temperature stability of cement paste, solves the problem of poor high-temperature stability of the existing cement paste, has no adverse effect on the comprehensive performance of the cement paste, and meets the requirements of site construction; in addition, the stabilizer has the advantages of simple preparation method, controllable conditions, low cost and market popularization and application prospect in the aspect of preparation.)

1. The high-temperature stabilizer for the high-density cement slurry is characterized by comprising 76-84 parts by weight of bentonite, 10-14 parts by weight of modified diutan and 6-10 parts by weight of cross-linked copolymer; the modified diutan is obtained by graft copolymerization of sodium styrene sulfonate and 2-acrylamide-2-methylpropanesulfonic acid; the crosslinked copolymer is prepared by copolymerizing 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, dimethyl diallyl ammonium chloride, N-vinyl caprolactam and divinylbenzene, and has a molecular weight of 7 multiplied by 10⁵～9×10⁵。

2. The high-temperature stabilizer for high-density cement slurry as claimed in claim 1, wherein the modified diutan is prepared by the following steps:

s1, slowly adding 10-15 parts by weight of diutan into 60-80 parts by weight of water, and continuously stirring the solution in the adding process at a stirring speed of 300-500 r/min;

s2, when the to-be-optimized gum is fully hydrated and is in a colloid state, adding 5-10 parts by weight of sodium p-styrenesulfonate and 5-10 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, continuously stirring until the sodium p-styrenesulfonate and the 2-acrylamide-2-methylpropanesulfonic acid are completely dissolved, and dropwise adding a NaOH solution until the pH of the solution is 5-5.5 to obtain a reaction mixed solution;

and S3, heating the reaction mixed solution to 60 ℃, adding 0.2-0.5 part by weight of an initiator I into the reaction mixed solution to perform free radical polymerization, continuously reacting for 4 hours, and performing spray drying to prepare uniform powdery solid for later use.

3. The high-temperature stabilizer for high-density cement slurry according to claim 2, wherein the initiator I is ammonium persulfate.

4. The high-temperature stabilizer for high-density cement slurry according to claim 1, wherein the preparation method of the crosslinked copolymer comprises the following steps:

s1, dissolving 40-50 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 15-20 parts by weight of acrylamide, 5-10 parts by weight of dimethyldiallylammonium chloride, 25-35 parts by weight of N-vinylcaprolactam and 1-2 parts by weight of divinylbenzene in water to obtain a reaction mixed solution with the monomer mass fraction of 15-20%;

s2, adding sodium hydroxide or sodium carbonate into the reaction mixed solution, and adjusting the pH value of the solution to 7-9;

s3, adding 2-5 parts by weight of emulsifier into the reaction mixed liquid prepared in the step S2, heating to 40-60 ℃ after uniformly stirring, adding 0.5-1.0 part by weight of initiator II to initiate reaction, and continuously reacting for 4-6 hours to obtain a reaction product liquid;

s4, spray drying the reaction liquid to prepare uniform powdery solid for later use.

5. The high temperature stabilizer for high density cement slurry according to claim 4, wherein the emulsifier is sodium dodecyl sulfate, sodium dodecyl sulfonate or sodium dodecyl benzene sulfonate.

6. The high-temperature stabilizer for high-density cement slurry according to claim 4, wherein the initiator II is a mixture of ammonium persulfate and sodium bisulfite with a molar ratio of 1: 1.

7. The high-temperature stabilizer for high-density cement slurry according to claim 1, wherein the bentonite is an OCMA type sodium bentonite.

8. The high-temperature stabilizer for high-density cement slurry as claimed in claim 1, wherein the preparation method comprises: and adding the bentonite into a double-helix conical mixing and stirring machine, sequentially adding the modified diutan and the cross-linked copolymer under the stirring condition, and continuously mixing and stirring for 1-2 h to obtain the high-temperature stabilizer for the high-density cement paste.

Technical Field

The invention relates to the technical field of downhole operation of oil and gas fields, in particular to a high-temperature stabilizer for high-density cement slurry and a preparation method thereof.

Background

Deep oil and gas resources in China have become the main field of exploration and development. The cement slurry for high-temperature deep well cementing usually adopts soluble polymers as additives such as fluid loss additive, retarder and the like, and solves various problems of large high-temperature water loss, difficult adjustment of thickening time and the like. However, as the exploration and development progress to a deeper level, some defects of the water-soluble polymer are gradually exposed in the application process, which is mainly reflected in that the viscosity of the polymer is obviously reduced along with the increase of the temperature, the stability of a polymer system is weakened, the settlement of cement particles is aggravated, and the stability of a cement paste system is poor. High-density cement slurry contains a large amount of weighting materials, so that sedimentation and even severe layering are more likely to occur.

For high-density cement slurry, a particle grading mode is usually adopted to improve the stability of the cement slurry at present. The particle size distribution of the weighting material is reasonably designed, and superfine particles such as micro-silicon powder, micro-manganese powder and the like are introduced, so that the high-temperature stability of the high-density cement paste can be solved to a certain extent. However, after the density exceeds 2.40g/cm3 and the temperature exceeds 130 ℃, the stability of the high-density cement paste is difficult to maintain.

In order to further improve the stability of the high-density cement slurry, researchers have conducted studies from several aspects:

CN104263333A discloses a high-density cement slurry stabilizer, which is composed of 20-30% of non-metallic oxide, 65-75% of metallic oxide and 3-5% of asphalt micropowder. The high-temperature stability of the high-density cement slurry is improved mainly by a particle grading mode. However, the suspending agent is inorganic particles, and the problems of slurry thinning, poor stability and the like caused by the aggravation of self thermal motion of cement and aggravating materials in high-density cement slurry and the high-temperature thinning of polymer additives cannot be solved.

CN105176505A discloses a cement slurry stabilizer for well cementation and a preparation method thereof, wherein the cement slurry stabilizer comprises 54-89 parts by weight of quartz sand, 2-20 parts by weight of welan gum, 0-8 parts by weight of xanthan gum, 3-10 parts by weight of polyvinyl alcohol and 3-8 parts by weight of graft high polymer. The stabilizer can improve the stability of cement paste, including high-density cement paste, and has no adverse effect on other properties of the cement paste. However, the preparation process of the grafted high molecular polymer related in the stabilizer is complex, and the grafted high molecular polymer can be prepared only by multi-step reaction, which is not beneficial to industrial production.

Disclosure of Invention

The invention aims to provide a high-temperature stabilizer for high-density cement slurry, which can obviously improve the stability of the high-density cement slurry under the high-temperature condition.

The invention also aims to provide a preparation method of the high-temperature stabilizer for the high-density cement slurry.

Therefore, the technical scheme of the invention is as follows:

a high-temperature stabilizer for high-density cement slurry comprises, by weight, 70-90 parts of bentonite, 2-20 parts of modified diutan and 2-10 parts of cross-linked copolymer; the modified diutan is obtained by graft copolymerization of sodium styrene sulfonate and 2-acrylamide-2-methylpropanesulfonic acid; the crosslinked copolymer is prepared by copolymerizing 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, dimethyl diallyl ammonium chloride, N-vinyl caprolactam and divinylbenzene, and has a molecular weight of 7 multiplied by 10⁵～9×10⁵。

Preferably, the high-temperature stabilizer for the high-density cement slurry comprises, by weight, 70-90 parts of bentonite, 2-20 parts of modified diutan and 2-10 parts of a cross-linked copolymer.

Preferably, the specific preparation steps of the modified diutan are as follows:

s1, slowly adding 10-14 parts by weight of diutan into 60-80 parts by weight of water, and continuously stirring the solution in the adding process at a stirring speed of 300-500 r/min;

s2, when the to-be-optimized gum is fully hydrated and is in a colloid state, adding 5-10 parts by weight of sodium p-styrenesulfonate and 5-10 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, continuously stirring until the sodium p-styrenesulfonate and the 2-acrylamide-2-methylpropanesulfonic acid are completely dissolved, and dropwise adding a NaOH solution until the pH of the solution is 5-5.5 to obtain a reaction mixed solution;

s3, heating the reaction mixed solution to 60 ℃, adding 0.2-0.5 part by weight of ammonium persulfate into the reaction mixed solution to carry out free radical polymerization reaction, and continuing to react for 4 hours, and then spray-drying the product to prepare uniform powder solid.

The modified diutan has the characteristic of high solution viscosity at a lower temperature, and chain rigid groups are introduced into the molecular structure of the diutan through modification: the sulfonate group effectively improves the stability of the solution under the high-temperature condition, so that the viscosity of the solution is less influenced by the temperature.

Preferably, the initiator I is ammonium persulfate.

Preferably, the preparation method of the crosslinked copolymer comprises the following steps:

s1, dissolving 40-50 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 15-20 parts by weight of acrylamide, 5-10 parts by weight of dimethyldiallylammonium chloride, 25-35 parts by weight of N-vinylcaprolactam and 1-2 parts by weight of divinylbenzene in water to prepare a reaction mixed solution with the monomer mass fraction of 15-20%; wherein, the divinylbenzene is a cross-linking agent;

s2, adding sodium hydroxide or sodium carbonate into the reaction mixed solution, and adjusting the pH value of the solution to 7-9;

s3, adding 2-5 parts by weight of emulsifier into the reaction mixed liquid prepared in the step S2, heating to 40-60 ℃ after uniformly stirring, adding 0.5-1.0 part by weight of initiator II to initiate reaction, and continuously reacting for 4-6 hours to obtain a reaction product liquid;

s4, spray drying the reaction liquid to prepare uniform powdery solid for later use.

The chemical structural formula of the high-density cement slurry high-temperature stabilizer is as follows:

in the graft copolymerization, 2-acrylamide-2-methylpropanesulfonic acid contains water-soluble and strong anionic sulfonic groups, so that the copolymer has good salt resistance and thermal stability; acrylamide is a strong adsorption monomer, and can improve the molecular weight and viscosity of the copolymer; dimethyl diallyl ammonium chloride is a cationic monomer, a five-membered ring is formed on a main chain of a macromolecule after polymerization, the chain rigidity of the polymer is improved, an association structure is formed between anions and cations under the condition of low temperature, the polymer is curled, the association structure is destroyed at high temperature, a stable net structure can be formed between the polymers, and the polymers are fully adsorbed with cement particles to play a role in suspension; meanwhile, by introducing a temperature-sensitive monomer: n-isopropyl acrylamide or N-vinyl caprolactam ensures that the copolymer is easily dissolved in water at a low temperature lower than the critical phase transition temperature (LCST), intermolecular hydrogen bonds are gradually dissociated, and the viscosity of a polymer solution is low; as the temperature rises above the LCST, the temperature-sensitive groups begin to self-assemble to form an interchain hydrophobic structure, so that the viscosity of the polymer solution can be increased, and as the temperature rises, the self-assembly behavior is intensified, and the viscosity of the polymer gradually increases; after reaching a certain degree, the viscosity of the polymer solution is gradually reduced along with the increase of the temperature, because more temperature-sensitive groups participate in forming a hydrophobic region in a larger range above the temperature, the hydrophobic region of the polymer solution is too large, phase separation is caused, a network structure is weakened, the viscosity of the polymer solution is reduced, and the consistency of the cement slurry added with the stabilizer cannot be too high under the condition of higher temperature can be ensured; the addition of the crosslinking agent moderately crosslinks the polymer to form a network structure, and maintains stability under high temperature conditions.

Preferably, the emulsifier is sodium dodecyl sulfate, sodium dodecyl sulfonate or sodium dodecyl benzene sulfonate.

Preferably, the initiator II is a mixture of ammonium persulfate and sodium bisulfite with a molar ratio of 1: 1.

Preferably, the bentonite is OCMA type sodium bentonite.

In the high-temperature stabilizer for the high-density cement paste, the high viscosity and the high suspension capacity of the modified diutan and the thermal tackifying performance and the high-temperature suspension capacity of the crosslinked copolymer have synergistic effect, so that the stability of the high-density cement paste under the high-temperature condition can be obviously improved, and the problem of poor high-temperature stability of the existing cement paste is effectively solved; and the OCMA type sodium bentonite has certain capacity of suspending and weighting materials, so that the risk of uneven mixing caused by excessively small addition of the cross-linked copolymer and the diutan can be effectively reduced, and the operability of field application is improved.

The preparation method of the high-temperature stabilizer for the high-density cement slurry is simple, and comprises the following specific steps: and adding the bentonite into a double-helix conical mixing and stirring machine, sequentially adding the modified diutan and the cross-linked copolymer under the stirring condition, and continuously mixing and stirring for 1-2 h to obtain the high-temperature stabilizer for the high-density cement paste.

Compared with the prior art, the high-temperature stabilizer for the high-density cement paste is prepared by mixing OCMA type sodium bentonite, modified diutan and a cross-linked copolymer in proportion, wherein the high viscosity and the high suspension capacity of the modified diutan and the thermal tackifying performance and the high-temperature suspension capacity of the cross-linked copolymer have synergistic effect, so that the stabilizer has the characteristics of high viscosity at low temperature and high viscosity at high temperature, remarkably improves the high-temperature stability of the cement paste, solves the problem of poor high-temperature stability of the existing cement paste, has no adverse effect on the comprehensive performance of the cement paste, and meets the requirements of site construction; in addition, the stabilizer has the advantages of simple preparation method, controllable conditions, low cost and market popularization and application prospect in the aspect of preparation.

Drawings

FIG. 1 is a graph of 2.50g/cm prepared without adding example 2 of the present invention³A performance result schematic diagram of a shutdown experiment of the high-density cement slurry of the high-temperature stabilizer for the high-density cement slurry;

FIG. 2 shows a graph of 2.50g/cm prepared by adding the catalyst of example 2 of the present invention³Schematic diagram of performance results of shutdown experiments of high-density cement slurry prepared by using high-temperature stabilizer for high-density and high-density cement slurry.

Detailed Description

The invention will be further described with reference to the following figures and specific examples, which are not intended to limit the invention in any way. In the following examples and comparative examples, sodium bentonite of the OCMA type and the raw materials for preparing the modified diutan and the crosslinked copolymer were purchased from commercially available products;