WO2024139501A1

WO2024139501A1 - Evaluation method for curing agent, and thermosetting resin cement paste for well cementation in oil and gas fields and preparation method therefor

Info

Publication number: WO2024139501A1
Application number: PCT/CN2023/123316
Authority: WO
Inventors: 张作宏; 严海兵; 赵启阳; 王纯全; 黄伟; 代清; 赖大禹; 余建; 梁远斌; 周利
Original assignee: 中国石油天然气集团有限公司; 中国石油集团川庆钻探工程有限公司
Priority date: 2022-12-26
Filing date: 2023-10-08
Publication date: 2024-07-04
Also published as: CN118258719A

Abstract

An evaluation method for a curing agent. The method allows for quick evaluation of a curing agent to determine the optimal addition amount thereof by means of judgments made according to a temperature-addition amount matrix graph. A thermosetting resin cement paste, which comprises a cement paste portion and a resin portion, wherein the cement paste portion comprises oil well cement, 3-6% of a filtrate reducer, 2-4% of an expanding agent, 0.02-0.25% of a retarder, 0.1-0.2% of a defoaming agent and 40-46% of water, based on the mass of the oil well cement being 100%; and the resin portion comprises an epoxy resin, 0.5-2% of a curing agent, 3-5% of an emulsifier and 0-170% of a weighting agent, based on the mass of the epoxy resin being 100%. The resin cement paste, when being in a liquid state, can prevent the formation of a permanent channel caused by weight loss and gas channeling; and when the resin cement paste is in a solid state, the integrity of a shaft can be maintained by improving the permeability, elasticity modulus, shear bond strength, etc., of cement stone.

Description

A curing agent evaluation method and thermosetting resin cement slurry for oil and gas field cementing and preparation method thereof

Technical Field

The invention relates to a curing agent evaluation method, thermosetting resin cement slurry for oil and gas field cementing and a preparation method thereof, and belongs to the technical field of cement slurry for cementing.

Background technique

Cementing is an indispensable and important part in the process of drilling and completion. When drilling reaches a certain level, casing will be lowered and cement slurry will be pumped to fill the gap between the well wall and the casing. Cementing of oil and gas wells is the process of injecting cement slurry into the annulus. The purpose is to achieve interlayer separation, support and protect the casing, prevent the oil, gas and water layers in the well from interpenetrating, stabilize the casing, and form a safe passage for oil production, gas production or water injection. The downhole situation after cementing is shown in Figure 14. Before construction, the space inside the casing and the annulus is all drilling fluid (liquid); during construction, cement slurry is injected into the casing through a cement pump truck, and the cement slurry displaces the drilling fluid, and then the drilling fluid with the same volume as the casing is used to displace the cement slurry, and finally the annulus is full of cement slurry, while the casing is full of drilling fluid. The entire fluid movement direction is similar to the U-tube effect. After that, it is the shut-in and waiting stage to allow the cement slurry to solidify and form a cement ring. At this time, the drilling fluid in the casing is still liquid, which is convenient for subsequent operations.

Silicate oil well cement is the main component of cementing materials. The cement stone formed has the defects of hardness, brittleness and volume shrinkage. In the solidification process of cement stone, the formation fluid cannot be stabilized due to "weightlessness", resulting in the formation of channels during the entry of fluid. In the later operation of cement ring, the changes in temperature and pressure lead to the formation of micro-annulus and internal micro-cracks, and the loss of separation, which causes the formation fluid to enter the cement ring, interlayer channeling, and even channeling to the wellhead, causing wellhead safety. With the extension of oil and gas well development time, problems such as annulus pressure caused by annulus sealing failure will become more and more serious.

The reasons for cement ring sealing failure and annulus pressure are generally as follows:

1. Silicate oil well cement itself has the defects of volume shrinkage and brittleness after solidification.

2. The changes in temperature and pressure caused by the later operations lead to mismatched deformation of cement ring and casing, forming micro-annulus at the interface between the two. For example, the temperature changes caused by fluid circulation in the wellbore, steam injection during thermal recovery, and liquid nitrogen injection during liquid nitrogen displacement; perforation, fracturing, gas injection in gas storage wells, increasing the density of drilling fluid when drilling high-pressure gas layers, reducing the density of drilling fluid when drilling lost formations, and using low-density well-killing fluid during oil testing will all lead to changes in downhole pressure.

3. The cement slurry cannot stabilize the formation during the weight loss process of waiting to set, and the formation fluid will enter the cement slurry and form channels during the migration process.

4. Changes in formation stress and the impact force generated by perforating will cause cracks in the hard and brittle cement sheath.

It is often the combined effect of the above factors that creates a fluid migration channel, which is more likely to occur when the fluid is gas.

Annulus pressure refers to the phenomenon that the pressure of the casing annulus at the wellhead returns to the pressure level before pressure relief after pressure relief.

Many scholars have analyzed the mechanism of annular pressure and pointed out that the anti-channeling performance of cement slurry, cement stone permeability, elastic modulus, interface bonding, and the failure of the second interface sealing under temperature and pressure changes, which cannot maintain the integrity of the wellbore, are the reasons for the annular pressure. 1 ([1] Song Jianjian, Xu Mingbiao, Wu Yumeng, Wang Xiaoliang, Schumann; Causes of annular pressure in gas wells and research progress [J]; Bulletin of Science and Technology, 2018, 34(09):8-1; [2] Zhu Renfa; Preliminary study on causes and prevention measures of annular pressure in natural gas wells [D]).

At present, there are three main ways to prevent annular pressure by improving the performance of cement slurry:

By adding an expansion agent with calcium oxide or magnesium oxide as the main material, the cement hydration process produces larger crystals, which can slow down the volume shrinkage of cement after solidification and reduce the size of the micro-annular gap formed on the first cementing surface (Zhang Qingjiao, Deng Min; Review of the Study on the Expansion Mechanism of Cement Paste Added with MgO Expansion Agent [J]; Science and Technology Review, 2009, 27(13):111-115). However, this solution can only alleviate the volume shrinkage, but cannot reduce the elastic modulus of cement paste. It still shows hardness and brittleness. The deformation during the stress process is very small and it is easy to break.

By adding elastic materials such as latex or rubber powder to cement slurry and filling it into cement stone after solidification, the elastic modulus can be reduced, so that when subjected to external force, a certain degree of deformation can occur, which is essentially a physical effect. Since there is no chemical reaction, it mainly depends on the effect of cement hydrate and the casing surface, so the shear bonding ability cannot be improved on the first bonding surface, and the compressive strength of cement stone is reduced. Rubber powder also has side effects such as non-hydrophilicity, poor wettability of cement slurry, and difficulty in slurrying.

CN 109504356 A discloses a high-strength, low-elasticity water-soluble resin cement slurry system, which is composed of the following components by weight: 100 parts of water-soluble epoxy resin, 30-70 parts of curing agent, 15 parts of diluent, 0-15 parts of accelerator, 0-2 parts of nano-silicon dioxide, 0-400 parts of weighting agent, 0-100 parts of oil well G-grade cement, 0-50 parts of water, and 1 part of defoamer. The water-soluble epoxy resin is a bisphenol A type water-based epoxy resin. The curing agent is diethylenetriamine, triethyltetramine, diaminodiphenylmethane, phthalic anhydride, methyltetrahydrophthalic acid or a mixture thereof. The diluent is acryl glycidyl ether, butyl glycidyl ether or alicyclic monoepoxy glycidyl ether. The accelerator is 2,4,6-tris(dimethylaminomethyl)-side-phenol. The resin cement slurry system has good compatibility with water, good fluidity, adjustable density, and excellent mechanical properties of high strength and low elasticity after curing. It can be used for cementing, special well section plugging, well abandonment, offshore unconventional well repair and other operations.

However, this method only considers the influencing factors of the compressive strength and elastic modulus of the cement sheath after cementing on the annular pressure, and does not consider the influencing factors of the permeability, shear bond strength, and the anti-channeling performance of the cement slurry in liquid state such as "weight loss" in the waiting stage on the annular pressure. In addition, water-soluble resin is used, and the modification and purification process is complicated.

Summary of the invention

In order to solve the above technical problems, the object of the present invention is to provide a method for evaluating a curing agent, by which a curing agent suitable for resin cement slurry for oil and gas well cementing is determined through testing.

The present invention also aims to provide a thermosetting resin cement slurry for oil and gas field cementing and a preparation method thereof.

To achieve the above object, the present invention first provides a method for evaluating a curing agent, which comprises the following steps:

Different types and different addition amounts of curing agents are mixed with epoxy resins to prepare epoxy resin mixtures to be tested;

The state of the epoxy resin mixture to be tested is observed with the construction time of the oil and gas well to be operated plus the additional safety time (generally 2 hours) as the limit; a construction safety matrix corresponding to various curing agents is established with the amount of curing agent added as the horizontal coordinate and the temperature as the vertical coordinate, and the corresponding state of the epoxy resin mixture to be tested obtained by observation is filled in;

The waiting time (generally 24 hours) is used as a limit, and then the observation is carried out again. Then, the corresponding state of the epoxy resin mixture to be tested obtained by observation is filled in the quality assurance matrix diagram with the amount of curing agent added as the horizontal axis and the temperature as the vertical axis;

Overlap the construction safety matrix and the quality assurance matrix, define the units that are liquid in the construction safety matrix and solid in the quality assurance matrix as ideal units; define the units that are liquid in the construction safety matrix and gel (high viscosity state) in the quality assurance matrix as critical units - focusing on safety; define the units that are gel (high viscosity state) in the construction safety matrix and solid in the quality assurance matrix as critical units - focusing on quality; define the units that are both liquid as non-ideal units - liquid; define the units that are both solid as non-ideal units - solid;

The temperature range formed by the maximum temperature and minimum temperature corresponding to all ideal units is the optimal temperature for this type of curing agent suitable for cementing operations, and the addition amount range formed by the corresponding maximum addition amount and minimum addition amount is the optimal addition amount for this type of curing agent suitable for cementing operations;

The temperature range formed by the maximum temperature and minimum temperature corresponding to all critical units is the critical temperature of this type of curing agent suitable for cementing operations, and the addition amount range formed by the corresponding maximum addition amount and minimum addition amount is the critical addition amount of this type of curing agent suitable for cementing operations. This method can quickly evaluate the curing agent and give a semi-quantitative conclusion.

In the above evaluation method, preferably, the definition of the ideal unit and the critical unit is performed in the following manner:

(1) A batch of resin mixtures to be tested containing different curing agent concentrations are respectively placed in glass reagent bottles, placed in the same water bath, heated to the test temperature, and the timing T is started at the same time; every time t (preferably, t = 0.5 hour or 1 hour), take out and observe, and record the status;

(2) Select different temperature points and repeat step (1);

(3) The status data corresponding to T = construction time + additional safety time is used to form a construction safety matrix diagram; the status data corresponding to T = waiting time (generally 24 hours) is used to form a quality assurance matrix diagram;

(4) The state can be divided into liquid, gel (high viscosity state), and solid; the solid state can be further divided into: initial solidification, medium strength solid, and high strength solid if necessary;

(5) Status determination:

Liquid: Visual inspection, gently shake the glass reagent bottle, it can flow quickly;

Gluing: Visual inspection, gently shake the glass reagent bottle, it can flow slowly and there is a phenomenon of wall adhesion;

Solid: visual inspection, shaking the glass reagent bottle, no flow;

Initial stage of solidification: feel, inserting the glass rod into the sample is difficult, or pinching the sample with hands, it may deform;

Medium-strength solids: Hearing, tapping a glass reagent bottle on a table makes a dull sound;

High-strength solid: Hearing, tapping the glass reagent bottle lightly on the table makes a crisp sound.

Although some resins or curing agents can be cured, their strength may not be high and their strength development speed may not be fast enough. The strength of fat cement slurry is not high enough. Wellbore integrity emphasizes low elastic modulus while also emphasizing high strength, which is a contradiction from a certain perspective. Therefore, most of the existing technical research avoids this and only emphasizes low elastic modulus. Liquid, gel, and solid are mainly focused on field applications; the technical solution of the present invention subdivides the solid state, especially T = waiting time (generally 24 hours) to better predict the performance of the solidified body formed by the tested resin mixture, so as to optimize the types of resin and curing agent.

In the above evaluation method, the epoxy resin mixture to be tested can be prepared in the following manner: different types and different amounts of curing agents are fully mixed with the resin, stirred evenly (for example, stirred at 200RPM for 10 minutes with a stirrer), placed in a glass reagent bottle, placed in a water bath at different temperatures, and timed.

In the above evaluation method, the strength of the solidified body can be tested by hand feel: if it can be deformed by hand, it has low strength; if it makes a dull sound when tapping on the table, it has medium strength; if it makes a crisp sound when tapping on the table, it has high strength. If the compressive strength needs to be accurately tested later, it can be done according to the common practice in the field.

Taking a mixture of 70% N-methylimidazole and 30% 2-ethyl-4-methylimidazole as an example, the evaluation results are shown in Figure 1. It can be seen that the optimal temperature is 70°C, the temperature range is 60-80°C, the optimal dosage is 1.0%, and the dosage range is 0.5-1.7%. The amount of curing agent is calculated relative to the resin. For example, for 100g of resin, the amount of curing agent is 1.5%, that is, 1.5g of curing agent.

The present invention also provides a thermosetting resin cement slurry for oil and gas field cementing, wherein the cement slurry comprises a cement slurry part and a resin part;

The cement slurry part includes oil well cement, 3-6% of fluid loss reducer, 2-4% of expansion agent, 0.02-0.25% of retarder, 0.1-0.2% of defoamer, and 40-46% of water, with the mass of oil well cement being 100%;

The resin part comprises epoxy resin, 0.5-2% of curing agent, 3-5% of emulsifier, and 0-170% (preferably 130-140%) of weighting agent, with the mass of epoxy resin being 100%.

Among them, when the cement slurry part is 0 and the addition amount of the emulsifier and weighting agent of the resin part is 0%, the curing agent and the epoxy resin can be mixed evenly and used alone, and the density is 1.13g/ ^cm3 ; when the addition amount of the weighting agent is 170%, it needs to be used in resin cement slurry, and the density of the prepared resin cement slurry is 2.00-2.04g/ ^cm3 ; when the addition amount of the weighting agent is 130-140%, it needs to be used in resin cement slurry, and the density of the prepared resin cement slurry is 1.88-1.92g/ ^cm3 , preferably 1.90g/ ^cm3 , which is suitable for most situations.

In the above-mentioned cement slurry, oil well cement is the basic cementitious material. Preferably, the oil well cement is Class G oil well cement, such as the high sulfur resistance (HRS) oil well Class G oil well cement produced by Jiahua Group, or other similar products available on the market that comply with GB 10238.

In the above cement slurry, the fluid loss agent is used to reduce the water loss of the cement slurry. Preferably, the fluid loss agent is the SD130 fluid loss agent produced by Sichuan Chuanqing Downhole Technology Co., Ltd. or the BXF-200L (AF) fluid loss agent produced by Tianjin PetroChina Boxing Engineering Technology Co., Ltd. The SD130 fluid loss agent is copolymerized with AMPS monomer and other monomers.

In the above cement slurry, the expansion agent is used to prevent or reduce the volume shrinkage of cement during solidification. Preferably, the expansion agent is the SDP-1 expansion agent produced by Sichuan Chuanqing Downhole Technology Co., Ltd. or the expansion agent produced by Sichuan Huaze Petroleum Technology Co., Ltd. CM025 expansion agent. The main components of the SDP-1 expansion agent are calcium oxide, magnesium oxide, aluminum oxide, etc., which are compounded from these components.

In the above cement slurry, the retarder is used to adjust the thickening time (pumping time) of the cement slurry. Preferably, the retarder is the SD21 retarder produced by Sichuan Chuanqing Downhole Technology Co., Ltd. The main component of the SD21 retarder is sodium salt of ethylidene organic phosphonic acid.

In the above cement slurry, the defoamer is used to eliminate bubbles generated during the preparation of the cement slurry. Preferably, the defoamer is the SD52 defoamer produced by Sichuan Chuanqing Underground Technology Co., Ltd. The main components of the SD52 defoamer are silicone oil, tributyl phosphate, etc., which are compounded from these components.

In the cement paste, epoxy resin is a low-molecular-weight material used to improve the performance of cement. Preferably, the epoxy resin is bisphenol A epoxy resin. When adding epoxy resin, a small amount of commonly used diluent can be appropriately added. The density of epoxy resin is about 1.13 g/cm ³ .

In the above cement slurry, preferably, the epoxy equivalent of the epoxy resin is 182-196 g/mol, preferably 185.693 g/mol.

In the cement paste, preferably, the kinematic viscosity of the epoxy resin at room temperature 16° C. is 350-380 mm ² /s, preferably 365 mm ² /s, and the kinematic viscosity at high temperature 70° C. is 10-30 mm ² /s, preferably 15.8 mm ² /s.

In the above cement slurry, preferably, the molecular weight of the epoxy resin meets the following requirements:

Epoxy resins with a number average molecular weight (Mn) of 7000-10000 (preferably 8019) account for 17.7%; epoxy resins with a number average molecular weight of 2500-4500 (preferably 3522) account for 81.0%, epoxy resins with a number average molecular weight of 100-300 (preferably 132) account for 1.3%, and the overall number average molecular weight is 2000-4000 (preferably 2815).

In the above cement paste, the curing agent is used to promote the polymerization reaction of the epoxy resin to form a three-dimensional cross-linked body. Preferably, the curing agent includes one or a combination of two or more of imidazole, N-methylimidazole, 2-ethyl-4-methylimidazole, N-allylimidazole and its derivatives and homologues (liquid). Among them, the melting point of 2-ethyl-4-methylimidazole is 47-54°C, and it is solid at room temperature. Adding a special solvent with curing function (such as one or a combination of two or more of cyclohexanedimethylamine, modified diaminodiphenyl sulfone, 4-amino-3-methylcyclohexane, polyetheramine) can dissolve it at room temperature and keep it in liquid state without crystal precipitation.

The mixture obtained by mixing the epoxy resin and the curing agent in the present invention can be used alone without adding cement slurry for casing repair and abandoned well management.

In the above-mentioned cement slurry, the role of the emulsifier is to use the water of the cement slurry as a continuous phase to emulsify the epoxy resin and the curing agent to form a dispersed phase, thereby improving the compatibility of the epoxy resin and cement and dispersing the epoxy resin in the cement slurry. Preferably, the emulsifier includes one or a combination of two or more of fatty alkyd methyl ethoxylate and its sulfonate (FMES), isomeric C10-15 fatty alcohol ethers, nonylphenol polyoxyethylene ether, and dicyclopentadiethylene fatty alcohol polyoxyethylene sulfonate.

In the cement slurry, the weighting agent is used to weight the resin part. Preferably, an indirect equivalent weighting method is used, that is, the amount of weighting agent required to weight the resin to the same density as the cement slurry part is first calculated, and the weighting agent is not directly added to the resin. Instead, it is mixed in cement so that the density of the resin part and the cement paste part are the same, so that the density of the resin cement paste obtained by mixing in any volume ratio remains unchanged. Preferably, the weighting agent is an inert weighting material, preferably barite (density is about 4.21 g/cm ³ ) and/or iron ore powder.

In the above cement slurry, preferably, the volume ratio of the cement slurry part to the resin part is 100:10-100:30, more preferably 100:15.

In the above cement slurry, preferably, the cement paste formed by the cement slurry has a 3d compressive strength greater than 40 MPa, an elastic modulus of 3.0-4.5 GPa, and a permeability of preferably 0.0026 mD.

Epoxy resin is a low-molecular polymer with epoxy groups at both ends. Under certain conditions, the epoxy groups undergo ring-opening polymerization to form a three-dimensional cross-linked network solidified body, which is a polymer polymerization reaction. The solidified body of epoxy resin has excellent functional mechanical properties such as high strength, low elasticity (modulus), and no volume shrinkage. The hardening nature of silicate cement is a dissolution precipitation process. Its hydrates overlap each other by various forces to form a solidified body, which is naturally brittle and has defects such as volume shrinkage. The present invention incorporates epoxy resin into oil well cement slurry, combines epoxy resin and silicate cement, and forms a new generation of functional cementing material-resin cement slurry, which is a cement slurry that can improve the hardness and brittleness of silicate oil well cement. As a cementing material, the resin cement slurry can prevent annular pressure in two stages: (1) in liquid (plastic) state, it prevents the formation of permanent channels due to "weightlessness" gas channeling; (2) in solid state, it maintains the integrity of the wellbore by improving the permeability, elastic modulus, shear bonding strength and other capabilities of the cement stone (ring).

The present invention also provides a method for preparing the above-mentioned thermosetting resin cement slurry for oil and gas field cementing, wherein the resin cement slurry is composed of two parts: a cement slurry part and a resin part, which are calculated by volume ratio; the resin part includes a mixture of resin and curing agent, an emulsifier, and a weighting agent, wherein the mixture of resin and curing agent is prepared separately, the emulsifier is added during the slurrying process, and the weighting agent exists in the form of being mixed in cement dry ash, and the concentrations (mixing ratio) of the curing agent, emulsifier, and weighting agent are all relative to the mass concentration of pure resin, and the calculation of the mass or volume of the three items is all included in the resin part; in the cement slurry part, the amount of cement admixture added is all relative to the mass concentration of pure cement, and the clean water is the mass ratio (W/C) relative to pure cement, as shown in Table 1.

Table 1 Composition and state of resin cement slurry

According to a specific embodiment of the present invention, the above preparation method may include the following steps:

First, the type and amount of curing agent can be determined according to the above-mentioned curing agent evaluation method, and the curing agent is mixed with the epoxy resin to obtain a mixture of the curing agent and the epoxy resin; when the type of curing agent is determined, this process can also be omitted;

The liquid phase components in the raw materials of the cement slurry part and the emulsifier are stirred and mixed; the rotation speed is increased, the solid materials and the weighting agent in the raw materials of the cement slurry part are added, and the rotation speed is increased again to obtain slurry;

The curing agent and epoxy resin mixture are added into the slurry and stirred to obtain the thermosetting resin cement slurry for oil and gas field cementing.

In the above preparation method, preferably, the liquid phase component in the raw materials of the cement slurry part and the emulsifier are stirred and mixed at a speed of 1500-2000 rpm for 15-30 seconds.

In the above preparation method, preferably, increasing the rotation speed is increasing the rotation speed to 4000 rpm.

In the above preparation method, preferably, the solid materials and weighting agents in the raw materials of the cement slurry part are added within 15 seconds.

In the above preparation method, preferably, increasing the rotation speed for stirring again is to increase the rotation speed to 12000 rpm and maintain it for 35 seconds.

In the above preparation method, preferably, after adding the curing agent and epoxy resin mixture to the slurry, stirring is performed at a speed of 200-400 rpm for 1 minute, thereby eliminating bubbles generated after high-speed stirring, facilitating more accurate density measurement in the next step.

According to a specific embodiment of the present invention, the preparation method of the present invention can also be carried out according to the following steps:

The liquid phase components in the raw materials of the cement slurry part, i.e., the liquid phase cement admixture and clean water, are stirred and mixed using a corrugated stirrer at a speed of 1500-2000 rpm for 15-30 seconds; then, the speed is increased to 4000 rpm, and cement, solid phase cement admixture, and weighting agent are added within 15 seconds; and the speed is increased to 12000 rpm and maintained for 35 seconds;

Subsequently, the rotation speed is reduced to 4000 rpm, an emulsifier is added and maintained for 10-20 seconds; a pre-prepared mixture of a curing agent and epoxy resin is added and maintained for 10-20 seconds, and then stirred at a rotation speed of 200-400 rpm for 1 minute to obtain the thermosetting resin cement slurry for oil and gas field cementing.

The resin cement slurry provided by the present invention is easy to prepare, has an adjustable density range, and a fluidity of 24 cm, which is similar to that of ordinary cement slurry; the high-temperature sedimentation stability and API water loss are better than those of ordinary cement slurry; the thickening time is adjustable; the 3d compressive strength is greater than 40MPa, the elastic modulus is 3.0-4.5GPa, and the permeability is 0.002-0.0026mD, which is better than the cement stone formed by ordinary cement slurry; the shear bonding strength is increased by 67%; the cement ring sealing simulation test shows that it can withstand a pressure difference of 70MPa, and the annulus has no gas channeling flow and pressure. It plays a role in preventing annulus pressure from being carried out in two stages: (1) in liquid state (plastic state), it prevents the formation of permanent channels due to "weightlessness" gas channeling; (2) in solid state, it maintains the integrity of the wellbore by improving the permeability, elastic modulus, shear bonding strength and other aspects of the cement stone (ring).

1. The incompatibility problem between epoxy resin and cement was solved through emulsification technology.

This is the most fundamental of all measures. By using the water content of the cement slurry as the continuous phase through the emulsifier, rather than adding additional water, the water-insoluble resin is formed into an oil-in-water emulsion, which is then dispersed in the cement slurry, solving the problem of the resin directly contacting the cement slurry and thickening during the slurry making process. From the slurry making situation, the fluidity of 24cm is similar to that of the blank cement slurry (micro-expansion cement slurry, prior art solution 1), and the slurry making is easy; from the API water loss point of view, 32ml is lower than the blank cement slurry. The thickening time curve reflects the absence of abnormal phenomena such as steps and bulging, indicating that the emulsification method is feasible. Prior art solution 3 is to put Resin modification to make it water-soluble solves the incompatibility problem. However, the modification process is complicated, involving purification, dissolution and effective concentration when used, and adding it to cement slurry will increase the amount of water.

2. Rapid evaluation method of curing agent (determine applicable temperature and dosage), using temperature-dosage matrix diagram for judgment.

This method is unique to the present invention and can quickly evaluate potential curing agents, find out the applicable temperature range and dosage range, and thus determine the optimal dosage. In the embodiment of the present invention, the optimal dosage is determined to be 1.0%. After 3 days, the infrared spectrum shows that the characteristic peak of the epoxy group disappears, so the superiority is reflected in the relevant properties of cement paste, avoiding the gelation or curing time earlier than the solidification time of the cement slurry, which may cause accidents during construction; it also avoids the solidification time later than the cement slurry for too long, which does not reflect the improvement effect of the resin. The existing technical solutions 1, 2, and 3 do not reflect this.

3. Chemical compatibility of epoxy resin, curing agent, cement and cement additives under temperature and pressure conditions.

Compared with the blank slurry, the technical solution of the present invention does not reduce the performance index, but is better; even if the curing agent is excessive, it has no obvious effect on the thickening time, etc. In short, the chemical compatibility is guaranteed.

4. Performance of resin cement slurry in preventing annular pressure in liquid (plastic) state

Due to the "weightlessness" of cement slurry, SPN = 1.79, and the transition time of 48-240pa static gel strength is 10 minutes, indicating that the resin cement slurry has a better anti-gas channeling function, thereby reducing the formation of permanent channels due to the "weightlessness" fluid entering the cement slurry. From this point of view, annular pressure is also prevented at this stage. Prior art solutions 1 and 2 do not have this function, and prior art solution 3 does not disclose data based on the prevention of annular pressure at this stage.

5. Performance of preventing annular space pressure during solidification of resin cement ring

After the cement stone is formed, that is, in the solid state, the mechanical properties of the cement stone formed by the embodiment of the present invention, the elastic modulus is reduced to 4GPa, which is significantly lower than the 8-9GPa of the blank cement slurry; the permeability (N2 as the medium) is 0.0026mD, which is much lower than that of ordinary cement slurry; the shear bonding strength is 67% higher than that of ordinary cement slurry; the wellbore integrity evaluation has passed the pressure difference of 70MPa inside and outside the casing, no micro cracks, micro annular gaps are generated, and the annular air channeling pressure and flow rate are 0; and the microscopic analysis by SEM can show that in the solid state, the resin cement stone (ring) has excellent mechanical properties, and the annular zone prevention is achieved at this stage. The existing technical solutions 1 and 2 can only achieve partial effects, and the existing technical solution 3 does not disclose the data based on the prevention of annular zone pressure at this stage.

6. About the method of aggravation

Technical solution 3 is to "balance" the low-density resin by configuring a higher-density cement slurry. In the art, inert weighting agents are usually used, or the ratio of water to cement (water-cement ratio W/C) is reduced, or both methods are used at the same time. In particular, reducing the water-cement ratio will increase the difficulty of equipment for preparing cement slurries with higher densities, and will also affect the performance of the cement slurry part, thereby interfering with the study of the influence of resin addition. Through these two methods, a variety of combination schemes can be formed, all of which can achieve the designed density of resin cement slurry, but the performance will be different, which will prevent different technicians in the field from communicating effectively. The technical solution of the present invention is an indirect equivalent weighting method, that is, first calculate the amount of weighting agent required to weight the resin to the same density as the cement slurry part. The weighting agent is not directly added to the resin, but mixed in the cement so that the resin part and the water are mixed. The density of the mud parts is the same, so that the density of the resin cement slurry obtained by mixing in any volume ratio remains unchanged. This design method can avoid the disadvantages of the conventional weighting method mentioned above.

7. Use the mixture of resin and curing agent separately

Since the technical solution of the present invention examines the conditions of the resin and the curing agent separately, it can be used independently without cement slurry, and a rapid evaluation method can be used to provide construction guidance. The prior art solution 3 does not disclose a similar situation.

8. Simple process and equipment during implementation

The present invention does not change the current construction process and does not require additional construction equipment. It only requires a container with a common stirring motor to stir the resin and the curing agent.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a temperature-dosage matrix diagram of the curing agent.

FIG. 2a and FIG. 2b are infrared spectra of epoxy resin and a cured product of epoxy resin and curing agent, respectively.

FIG3a and FIG3b are respectively the appearance of the cured body of the resin under the action of the curing agent and the elastic modulus test curve.

FIG. 4 a and FIG. 4 b are SEM microstructures of the cured body under the action of epoxy resin and curing agent alone, wherein FIG. 4 a is magnified 1k times, and FIG. 4 b is magnified 2k times.

FIG. 5 shows the slurry preparation and mixing process of the resin cement slurry.

Figure 6 shows the high temperature sedimentation of resin cement slurry.

FIG7 is a thickening curve of resin cement slurry, where (a) is formulation 2# and (b) is formulation 3#.

Figure 8 is a static gel strength development curve.

Figure 9 is the elastic modulus curve of resin cement slurry (Vcement slurry: Vresin = 100:15), where (a) is the 2# test mold when the confining pressure is 0; (b) is the 3# test mold when the confining pressure is 0; (c) is the 5# test mold when the confining pressure is 10 MPa; (d) is the 6# test mold when the confining pressure is 10 MPa.

Figure 10 shows the annular air flow rate of resin cement slurry under different pressure differences.

Figure 11 shows the SEM microstructure of blank cement paste and resin cement paste, where (a-1) is Vs:Vr=100:0 (500x); (b-1) is Vs:Vr=100:15 (500x); (c-1) is Vs:Vr=100:20 (500x); (a-2) is Vs:Vr=100:0 (1000x); (b-2) is Vs:Vr=100:10 (1000x); (c-1) is Vs:Vr=100:20 (1000x). Vs:Vr refers to the volume ratio of the cement paste part to the resin part.

Figure 12 shows the pore structure calculated based on the SEM microstructure of cement paste (solidified body), where (a) is Vs:Vr=100:0 (500x); (b) is Vs:Vr=100:15 (500x); and (c) is Vs:Vr=100:20 (500x).

Figure 13 shows the microstructure of microcracks in different cement pastes after repeated loading and unloading three times, where (a-1) is Vs:Vr=100:0 (500x); (b-1) is Vs:Vr=100:15 (500x); (c-1) is Vs:Vr=100:20 (500x).

Figure 14 shows the downhole situation after cementing.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

Example

This embodiment provides a thermosetting resin cement slurry for oil and gas field cementing and a preparation method thereof, which is used for oil and gas wells at 70° C. and the construction time is about 3 hours.

The preparation method comprises the following steps:

(I) Determine the curing agent

According to the evaluation method of the curing agent provided by the present invention, the safe construction time = 5h (construction time 3h + safety additional time 2h) and the waiting time = 24h are limited, and the judgment criteria are set as follows:

Status judgment

Solid: visual inspection, shaking the glass reagent bottle, no flow;

The units that are in liquid state in the construction safety matrix diagram (when safe construction time = 5h) and in solid state in the quality assurance matrix diagram (when waiting time for setting = 24h) are judged as "ideal"; in the "ideal" area, the curing agent addition value corresponding to the addition value with high solidified body strength should be selected as much as possible.

Further investigation of the curing results in the "rational" unit. Observation of the solidified body with a waiting time of 24h shows that the high-strength solid is the best, followed by the medium-strength solid, and the initial solidification is poor. The specific temperature-dosage matrix of the curing agent is shown in Figure 1.

From this, it can be determined that the amount of curing agent added should be 1.0-1.5% and the temperature range should be 65-75℃.

The test was conducted at 70°C and with a curing agent addition of 1.0% (mainly considering that the strength of the solidified body will be relatively weak, which is the lower limit of the effective range).

Using infrared spectrometer, test and characterize the epoxy functional group in the resin to analyze the curing degree of the resin. During the experiment, the resin (liquid), the cured body under the action of epoxy resin and curing agent alone were taken and tested using infrared spectrometer. As can be seen from Figure 2a, the resin (liquid) has a characteristic absorption peak of epoxy group with a wave number of 915cm ^-1 , and a characteristic absorption peak of benzene ring with a wave number of 1607cm ^-1 and 1506cm ^-1 . The cured body produced after the action of the cycloresin and curing agent (as shown in Figure 2b), the characteristic peak of the epoxy group disappears, and the characteristic peak of the benzene ring still exists, proving that the epoxy group of the resin has been ring-opening polymerized within 3 days and the reaction is complete.

After the resin + curing agent 1.0% was fully mixed, the elastic modulus and compressive strength were tested at 70℃×0.1MPa×72H. Degree test and infrared spectrum analysis. According to the infrared spectrum, as shown in Figure 2b, the characteristic absorption peak of the epoxy group with a wave number of 915cm ^-1 disappears, proving that the epoxy group of the resin has been ring-opened and polymerized within 3 days and the reaction is complete. The compressive strength is 48MPa and the elastic modulus is 3.37GPa, as shown in Figure 3b. It is difficult to remove the solidified body from the curing kettle. It is firmly bonded to the base of the kettle and cannot be removed by hand. Although the contact surface is coated with sealing grease, it falls off the base of the kettle after being hit with a hammer. Preliminary analysis shows that it has strong bonding ability. As can be seen from Figure 3a, it is found that part of the bottom is still bonded to the base, and there is a half-circle ring on the lower edge (the instrument is designed with a circle of grooves), which cannot be broken by hand; while normal cement slurry can be broken by hand with a slight force.

The characteristics and formation process of the cured resin were analyzed: the cured epoxy resin and the curing agent were taken separately. The microstructure of the cured epoxy resin was observed by scanning electron microscopy (SEM) at 1000 times and 2000 times, as shown in Figure 4a and Figure 4b. After curing, the epoxy resin showed dense regular stripes with flexibility and no voids, which proved that the low molecular weight liquid epoxy resin was ring-opened and polymerized under the action of the curing agent to form a three-dimensional network structure, which was a chain polymer cross-linked body with a high degree of polymerization.

(II) Resin cement slurry formula and preparation process:

The total volume is 600 mL, Vs (volume of cement slurry): Vr: (volume of resin) = 100:15, that is, Vs = 521.7 mL, Vr = 78.3 mL,

Composition of each substance

Cement slurry part: Jiahua G (673.0g) + 2% expansion agent SDP-1 (13.46g) + 4% fluid loss reducer SD130 (26.92g) + 0.02% medium temperature retarder SD21 (0.40g) + 0.2% defoamer SD52 (1.35g) + clean water (280.87g);

Resin part: epoxy resin (60.25g) + 1.35 barite (85.56g) + 1% curing agent (0.60g) + 5% emulsifier (3.01g), wherein the curing agent is a mixture of code-named G70, 70% N-methylimidazole and 30% 2-ethyl-4-methylimidazole, and the emulsifier is fatty alcohol methyl ethoxylate and its sulfonate, isomeric C10-15 fatty alcohol ether, or nonylphenol polyoxyethylene ether.

Among them, the epoxy resin is bisphenol A epoxy resin; the epoxy equivalent of the epoxy resin is 185.693g/mol, the viscosity at room temperature is ^365mm2 /s, and the viscosity at high temperature is ^15.8mm2 /s; the epoxy resin with a number average molecular weight of 8019 accounts for 17.7%; the epoxy resin with a number average molecular weight of 3522 accounts for 81.0%, the epoxy resin with a number average molecular weight of 132 accounts for 1.3%, and the overall number average molecular weight is 2815.

Preparation process of resin cement slurry:

Place the corrugated mixer slurry cup containing liquid cement admixture, clean water and emulsifier on the corrugated mixer, and pre-mix at 1500-2000rpm for 15-30 seconds; then adjust the speed to 4000rpm, pour cement, barite and other solid materials into the slurry cup within 15s, and then set the speed to 12000rpm and mix for 35s; place the slurry cup on an electronic balance, add the resin and curing agent mixture, place it on the mixer, control the speed at 200-400rpm, and mix for 1min to obtain resin cement slurry.

(III) Test data and analysis in liquid state

The cement slurry part in the resin cement slurry formula in (II) is used as the blank cement slurry, that is, the 1# formula in Table 2. The method is also the technical solution in the prior art solution 1, which is used as a comparative example.

Formula 2# is the formula of the resin cement slurry in (II);

Formula 3# is based on the formula of resin cement slurry in (II), with the addition amount of medium-temperature retarder SD21 increased to 0.04%.

Table 2 Test data of different working fluids in liquid state

The slurry preparation and mixing process and high temperature sedimentation of the resin cement slurry are shown in Figures 5 and 6 respectively.

From the fluidity data in Table 2, it can be analyzed that the resin cement slurry and the blank cement slurry (current micro-expansion cement slurry system) have the same fluidity at room temperature under the same density. The wettability and flow state during the slurry making process indicate that the mixing difficulty is equivalent; the high temperature stability (water separation) and high temperature fluidity in Table 2 show that the water separation result of the resin cement slurry at high temperature is 0.5% less than that of the blank cement slurry, and the high temperature fluidity is reduced to 20.5cm compared with the fluidity at room temperature, indicating that the resin cement slurry helps to stabilize the slurry at high temperature and slow down the instability caused by "thermal dilution". The API water loss in Table 2 is 32mL for the resin cement slurry, which is less than the 48mL water loss of the blank cement slurry, indicating that the water loss can be further reduced; the thickening time in Table 2, the thickening time test of the resin cement slurry is 211min/30Bc, 220min/100Bc, which is about 30min longer than the overall thickening time of the blank cement slurry. The thickening curve is smooth, without abnormal phenomena such as steps or bulges. When the dosage of retarder SD21 is increased to 0.04%, the thickening time is 298min/30Bc and 306min/100Bc, indicating that it has adjustability (as shown in (a) and (b) in Figure 7), and is consistent with the empirical value of the dosage sensitivity of SD21 under this condition. The thickening performance of resin cement slurry is mainly affected by the cement slurry part.

Anti-gas channeling performance

The anti-gas channeling performance is investigated using the cement slurry performance factor (SPN), and the specific expression is:

Where: SPN - cement slurry performance coefficient, dimensionless;

FL _API —— API water loss of cement slurry, mL;

_t100Bc ——the time when the cement slurry consistency reaches 100Bc, min;

_t30Bc ——The time when the cement slurry consistency reaches 30Bc, min.

General evaluation criteria for SPN values: When the SPN value is 1-3, the anti-gas channeling effect is good; when the SPN value is 3-6, the anti-gas channeling effect is medium; when the SPN value is greater than 6, the anti-gas channeling effect is poor. The smaller the value, the better the anti-gas channeling effect.

The calculated resin cement slurry SPN=1.79 indicates that it has a good anti-channeling effect.

Using the transition time of 48-240Pa static gel strength to examine the anti-gas channeling function (Zhu Haijin, Qu Jiansheng, Liu Aiping, Zou Jianlong, Xu Jiaxing; A new method for evaluating the anti-gas channeling performance of cement slurry [J]. Natural Gas Industry, 2010, 30(08): 55-58+116-117)

It can be seen from the static gelation development curve in Figure 8 that the static gelation time of the resin cement slurry is 10 minutes, and it has a strong anti-channeling function.

(IV) Solid-state test data and analysis

The performance tests of different working fluids in the solid state are shown in Table 3.

Table 3 Test data of different working liquid solid state

1. Compressive strength

In terms of compressive strength, the compressive strength of resin cement paste is 40MPa, while that of blank cement paste is 32MPa, an increase of 25%.

2. Elastic modulus

Using a high-temperature and high-pressure curing kettle, pour the cement slurry into the mold, cure it under a certain temperature and pressure, take it out after solidification, cool it to room temperature, and process it into a Φ25.00mm×50.00mm cylinder. The two ends are cut and polished flat and perpendicular to the axis of the cylinder. The non-parallelism of the two end surfaces is less than 0.015 mm. The RTR-1000 triaxial rock mechanics servo test system manufactured by GCTS of the United States is used to carry out triaxial mechanical testing of cement stone.

The resin cement paste (Vs: Vr = 100: 15) was poured into the mold and cured at 70℃×21MPa for 3 days. Six parallel samples were prepared for elastic modulus test. The test was conducted under two conditions: confining pressure of 0 and 10MPa. From Table 4, it can be seen that the elastic modulus is around 4.2GPa. The confining pressure has little effect on the elastic modulus, but has a significant effect on the deformation. When the confining pressure is 0, the deformation is generally 0.6-0.8%, while when the confining pressure is 10MPa, the deformation can reach more than 3.5%, as shown in Figure 9.

Table 4 Test results of elastic modulus and Poisson's ratio of resin cement slurry

The elastic modulus of resin cement paste is 8-9GPa lower than that of ordinary cement paste, which meets the requirement of "Technical Specifications for Tough Cement for Well Cementing" of less than 6GPa.

3. Penetration

Using a high-temperature and high-pressure curing kettle, pour the cement slurry into the mold, cure it under a certain temperature and pressure, take it out after solidification, cool it to room temperature, and process it into a Φ25.00mm×50.00mm cylindrical test mold. Put the test mold into the instrument, apply a certain confining pressure and temperature, use nitrogen as the medium, collect the gas pressure and gas flow at both ends of the test mold, and calculate the permeability according to the corresponding formula.

The resin cement slurry (Vs: Vr = 100: 15) was poured into the mold and cured at 70℃×21MPa for 3 days, and 4 parallel samples were prepared for permeability testing. The confining pressure during the test was 3MPa and the temperature was 70℃. As can be seen from Table 5, the average permeability was 0.0026mD, which is less than the 0.05mD required by the Technical Specifications for Tough Cement for Well Cementing.

Table 5 Permeability test results of resin cement stone

4. Bonding strength

Pour cement slurry into a steel pipe of a certain diameter and height, cure it under certain conditions, take it out after solidification, and apply external force vertically to the end face of the cement stone to push the cement stone out of the steel pipe. Measure the external force value when the cement stone is just pushed out, the inner diameter and height of the steel pipe, and use formula 2 to calculate the wall shear bonding strength between the cement stone and the steel pipe.

Where:

M——the wall shear bonding strength between cement stone and steel pipe, MPa;

F——Force applied vertically to the end surface of cement stone, KN;

D——Inner diameter of steel pipe, mm;

H——height of the steel pipe, mm.

In this experiment, blank cement slurry and resin cement slurry (Vs:Vr=100:15) were poured into cylindrical metal molds with a diameter of 25.4mm and a height of 50.8mm, with 3 parallel samples each. They were cured at 70℃×21MPa for 3d. The molds containing cement samples were cooled to room temperature and then taken out. A compressive strength tester was used to apply external force to the samples, and the external force value was recorded, and the bonding strength was calculated.

From Table 6, it can be seen that the average value of the interface bonding strength of the blank cement paste is 4.05 MPa, and the average value of the interface bonding strength of the resin cement paste is 6.7 MPa, which is increased by about 67%.

Table 6 Bond strength test results of blank cement slurry and resin cement slurry

Due to factors such as surface mold material and surface roughness, it is more objective to use molds processed in the same batch to measure the relative comparison values of cement slurries of different systems.

5. Wellbore integrity

The resin cement slurry is injected into the double-layer casing in the simulation equipment. After curing for a period of time at a certain temperature and pressure, the resin cement solidifies, and then different pressures are applied to the inner casing and maintained for a period of time, and then the pressure is released to simulate and test whether new cracks are formed in the cement ring under the pressure difference, whether the first cementing surface and the second cementing surface are separated due to deformation, and whether they can be restored after pressure relief. At the same time, the axial gas channeling pressure and flow are measured to judge the pressure situation at the wellhead. This method is the most advanced evaluation method in the world. This experiment is carried out according to the Chinese patent "A dynamic test device and experimental method for the separation capacity of cementing cement ring", patent number: ZL 2016 1 1132395.6.

The experiment was conducted after the temperature and pressure were raised to 70℃×21MPa and cured for 7 days. The pressures were 25MPa, 35MPa, 40MPa, 45MPa, 60MPa, and 70MPa for 8min, with an interval of 3min each time. The loading was repeated. During the experiment, the gas channeling flow rate and gas channeling pressure were always 0. The results are shown in Figure 10: no microcracks or microannular gaps were generated, and the cement sheath had good integrity, thus preventing annular pressure.

Combined with the elastic modulus data, it is proved that resin cement slurry is an ideal working fluid required to meet the integrity of the cement sheath, and can meet the engineering needs such as the changes in cement sheath pressure caused by changes in drilling fluid density during gas storage injection and production and drilling and completion.

6. Effect of epoxy resin on the microstructure of cement paste

The solidified bodies formed by blank cement paste, resin cement paste (Vs:Vr=100:15), and resin cement paste (Vs:Vr=100:20) were observed at magnifications of 500 and 1000 times, respectively, as shown in Figure 11. The blank cement paste has a loose and porous microstructure; while the microstructure of the resin cement paste is obviously more dense, and there are solid spheres scattered in it, which can explain that the resin is dispersed in the cement paste after emulsification, and exists in two ways: one is that part of the resin is wrapped and adsorbed on the surface of cement particles and filled in the gaps between particles. Since the cement hardening reaction and the resin curing reaction are not completely synchronized, the resin can enter the loose gaps between the cement hydration products and then gradually solidify, making the cement paste more dense, and the density of the resin cement paste increases with the increase in the amount of resin added; in addition, part of the emulsified resin and curing agent agglomerate due to surface tension, and it presents a spherical structure after curing.

At the same time, image processing technology was used to process the SEM microstructure images of different cement stones (solidified bodies) during the analysis process. The threshold between pores and solid components in the SEM microstructure image is determined by combining the “inflection point method”, and then the pore structure and its distribution are extracted from the SEM microstructure image, as shown in Figure 12. The results in Figure 12 further show that when epoxy resin is added to cement paste, the porosity of cement paste can be effectively reduced.

The solidified body formed by the reaction of epoxy resin and curing agent has a lower elastic modulus than pure silicate cement paste. However, when epoxy resin solidified body and cement paste coexist, the mutual influence between the resin solidified body and the cement skeleton can form micro cracks inside the cement paste by artificial cracking, observe the microscopic morphology of the cracks, and indirectly analyze the stress distribution of the resin cement paste. In this study, blank cement paste and resin cement paste (Vs: Vr = 100: 15) were repeatedly loaded and unloaded three times at a pressure of 90% of their respective compressive strength values, and the microscopic state of micro cracks in the cement paste was observed using SEM, as shown in Figure 13.

It can be seen from Figure 13 that there are obvious through cracks in the blank cement paste, and the cracks are straight; while the cracks in the resin cement paste are obviously more curved, and the number of branch cracks increases. The resin solidified body that wraps the cement particles or fills the gaps between the particles plays a role in force transmission and deflection of crack extension. In addition, according to the results of Figure 13, the overall skeleton in the resin cement paste is still the hydrate of cement paste. Under the action of external force, the resin can effectively transmit and deflect the direction of crack extension, thereby increasing the energy required for cement paste destruction and enhancing the elastic deformation capacity of cement paste. In addition, the epoxy resin solidified body in the cement paste will also undergo slight deformation under the action of external force, "temporarily storing" external energy in the form of potential energy. Once the external force is removed, the potential energy will be released again, which is reflected in the lower elastic modulus, higher compressive strength, and larger deformation in the macroscopic sense.

(V) On-site entry into the well

Two well tests were carried out on a certain well using the resin cement slurry with formulation 2#. The logging interpretation data of CBL and BR of the well are shown in Figure 7 and Table 8 respectively.

Table 7 Well logging interpretation data of CBL

Table 8 BR logging interpretation data

By conducting relative acoustic amplitude logging (CBL) on the well, a quantitative evaluation of the first bonding surface was performed, and the high-quality rate of the resin cement slurry sealing section (1800.00-2100.00m) was 53.05%, and the qualified rate was 95.35%. The bonding ratio (BR) index was used to quantitatively evaluate the second bonding surface, and the high-quality rate of the resin cement slurry sealing section (1800.00-2100.00m) was 74.19%, and the qualified rate was 98.77%; both were significantly higher than the cementing level of the entire well, proving that resin cement slurry can improve cementing quality compared with conventional cement slurry.

Claims

A method for evaluating a curing agent comprises the following steps:

Mixing different types and different addition amounts of curing agents with epoxy resins to prepare epoxy resin mixtures to be tested;

The state of the epoxy resin mixture to be tested is observed with the construction time of the oil and gas well to be operated plus the additional safety time as the limit; a construction safety matrix corresponding to various curing agents is established with the amount of curing agent added as the horizontal coordinate and the temperature as the vertical coordinate, and the corresponding state of the epoxy resin mixture to be tested obtained by observation is filled in;

The observation is performed again with the waiting time as the limit, and then the corresponding state of the epoxy resin mixture to be tested obtained by observation is filled in the quality assurance matrix diagram with the amount of curing agent added as the horizontal coordinate and the temperature as the vertical coordinate;

Overlap the construction safety matrix and the quality assurance matrix, define the units that are liquid in the construction safety matrix and solid in the quality assurance matrix as ideal units; define the units that are liquid in the construction safety matrix and gelled in the quality assurance matrix as critical units - focusing on safety; define the units that are gelled in the construction safety matrix and solid in the quality assurance matrix as critical units - focusing on quality; define the units that are both liquid as non-ideal units - liquid; define the units that are both solid as non-ideal units - solid;

The temperature range formed by the maximum temperature and minimum temperature corresponding to all ideal units is the optimal temperature for this type of curing agent suitable for cementing operations, and the addition amount range formed by the corresponding maximum addition amount and minimum addition amount is the optimal addition amount for this type of curing agent suitable for cementing operations;

The temperature range formed by the maximum temperature and minimum temperature corresponding to all critical units is the critical temperature of this type of curing agent suitable for cementing operations, and the addition amount range formed by the corresponding maximum addition amount and minimum addition amount is the critical addition amount of this type of curing agent suitable for cementing operations.
The evaluation method according to claim 1, wherein the ideal unit and the critical unit are defined in the following manner:

(1) A batch of resin mixtures to be tested containing different curing agent concentrations are placed in glass reagent bottles, placed in the same water bath, heated to the test temperature, and the timing T is started at the same time; after a period of time t, the mixtures are taken out for observation and the status is recorded;

(2) Select different temperature points and repeat step (1);

(3) The status data corresponding to T = construction time + additional safety time is used to form a construction safety matrix diagram; the status data corresponding to T = waiting time is used to form a quality assurance matrix diagram;

(4) The state can be divided into liquid, gel, and solid; among them, the solid state can be further divided into: initial solidification, medium-strength solid, and high-strength solid when necessary;

(5) Status determination:

Liquid: Visual inspection, gently shake the glass reagent bottle, it can flow quickly;

Gluing: Visual inspection, gently shake the glass reagent bottle, it can flow slowly and there is a phenomenon of wall adhesion;

Solid: visual inspection, shaking the glass reagent bottle, no flow;

Initial stage of solidification: feel, inserting the glass rod into the sample is difficult, or pinching the sample with hands, it may deform;

Medium-strength solids: Hearing, tapping a glass reagent bottle on a table makes a dull sound;

High-strength solid: Hearing, tapping the glass reagent bottle lightly on the table makes a crisp sound.
A thermosetting resin cement slurry for oil and gas field cementing, wherein the cement slurry comprises a cement slurry part and a resin part;

The cement slurry part includes oil well cement, 3-6% of fluid loss reducer, 2-4% of expansion agent, 0.02-0.25% of retarder, 0.1-0.2% of defoamer, and 40-46% of water, with the mass of oil well cement being 100%;

The resin part comprises epoxy resin, 0.5-2% of curing agent, 3-5% of emulsifier and 0-170% of weighting agent, with the mass of epoxy resin being 100%.
The cement slurry according to claim 3, wherein the oil well cement is Grade G oil well cement.
The cement slurry according to claim 3, wherein the fluid loss reducer is a SD130 fluid loss reducer produced by Sichuan Chuanqing Downhole Technology Co., Ltd. or a BXF-200L (AF) fluid loss reducer produced by Tianjin Sinopec Boxing Engineering Technology Co., Ltd.
The cement slurry according to claim 3, wherein the expansion agent is an SDP-1 expansion agent produced by Sichuan Chuanqing Downhole Technology Co., Ltd. or a CM025 expansion agent produced by Sichuan Huaze Petroleum Technology Co., Ltd.
The cement slurry according to claim 3, wherein the retarder is SD21 type retarder produced by Sichuan Chuanqing Downhole Technology Co., Ltd.
The cement slurry according to claim 3, wherein the defoaming agent is SD52 defoaming agent produced by Sichuan Chuanqing Downhole Technology Co., Ltd.
The cement slurry according to claim 3, wherein the epoxy resin is bisphenol A epoxy resin.
The cement slurry according to claim 9, wherein the epoxy equivalent of the epoxy resin is 182-196 g/mol.
The cement slurry according to claim 9, wherein the kinematic viscosity of the epoxy resin at room temperature of 16°C is 350-380 mm 2 /s, and the kinematic viscosity at a high temperature of 70°C is 10-30 mm 2 /s.
The cement slurry according to claim 9, wherein the molecular weight of the epoxy resin meets the following requirements:

Epoxy resins with a number average molecular weight of 7000-10000 account for 17.7%; epoxy resins with a number average molecular weight of 2500-4500 account for 81.0%; epoxy resins with a number average molecular weight of 100-300 account for 1.3%, and the overall number average molecular weight is 2000-4000.
The cement slurry according to claim 3, wherein the curing agent comprises one or a combination of two or more of imidazole, N-methylimidazole, 2-ethyl-4-methylimidazole, N-allylimidazole and their derivatives and homologues.
The cement slurry according to claim 3, wherein the emulsifier comprises one or a combination of two or more of fatty alcohol methyl ethoxylate and its sulfonate, isomeric C10-15 fatty alcohol ether, nonylphenol polyoxyethylene ether, and dicyclopentadiethylene fatty alcohol polyoxyethylene sulfonate.
The cement slurry according to claim 3, wherein the weighting agent is added in an amount of 130-140%, Inert weight material.
The cement slurry according to claim 15, wherein the inert weighting material is barite and/or iron ore powder.
The cement slurry according to claim 3, wherein the volume ratio of the cement slurry part to the resin part is 100:10-100:30.
The cement slurry according to claim 3, wherein the cement paste formed by the cement slurry has a 3d compressive strength greater than 40 MPa and an elastic modulus of 3.0-4.5 GPa.
The cement slurry according to claim 18, wherein the permeability of the cement paste formed by the cement slurry is 0.0026mD.
The method for preparing the thermosetting resin cement slurry for oil and gas field cementing according to claim 3 comprises the following steps:

Determine the type and amount of curing agent according to the evaluation method of claim 1, and mix the curing agent with the epoxy resin to obtain a mixture of the curing agent and the epoxy resin;

The liquid phase components in the raw materials of the cement slurry part and the emulsifier are stirred and mixed; the rotation speed is increased, the solid materials and the weighting agent in the raw materials of the cement slurry part are added, and the rotation speed is increased again to obtain slurry;

The curing agent and epoxy resin mixture are added into the slurry and stirred to obtain the thermosetting resin cement slurry for oil and gas field cementing.
According to the preparation method of claim 20, the liquid phase component in the raw materials of the cement slurry part and the emulsifier are stirred and mixed at a speed of 1500-2000 rpm and the time is 15-30 seconds.
The preparation method according to claim 20, wherein increasing the rotation speed is increasing the rotation speed to 4000 rpm.
The preparation method according to claim 20, wherein the solid material and the weighting agent in the raw materials of the cement slurry portion are added within 15 seconds.
The preparation method according to claim 20, wherein increasing the speed for stirring again is to increase the speed to 12000 rpm and maintain it for 35 seconds.
The preparation method according to claim 20, wherein the stirring after adding the curing agent and epoxy resin mixture to the slurry is at a speed of 200-400 rpm for 1 minute.