CN103484087B - Viscoelastic cementing packing material - Google Patents

Abstract

The present invention relates to a kind of viscoelasticity well cementation packer material.This viscoelasticity well cementation packer material, its component and proportioning are as follows: high molecular polymer host 20-82.5%, cross-linking agent 3-9%, fluidised form regulator 5-9%, suspending agent 0.5-1%, heavy weight additive 0-49.5%, water 0-22%.This viscoelasticity well cementation packer material, it is possible to form viscoelastic well cementation packer material in down-hole, strengthens the anti-ability of altering of well cementation annular space, the well cementation pack quality of raising Oil/gas Well.

Description

Viscoelastic cementing packing material

technical field

The invention relates to a cementing packing material used in the field of petroleum drilling, in particular to a viscoelastic cementing packing material which is liquid during cementing construction and solidifies itself after injection.

Background technique

Annular channeling after cementing is one of the technical problems faced by current drilling engineering. It will lead to the inability to achieve effective isolation between the formation and the casing, causing interlayer channeling or oil, gas and water leakage from the wellhead, and may lead to the scrapping of the entire well in severe cases. The quality of the isolation performance of the cementing material directly affects the quality of the downhole annulus isolation ability. However, as a common cementing material at present, oil well cement is a hydraulically hardened gelling substance. The cured cement stone has inherent defects such as high porosity and large volume shrinkage, and it is easy to break in its body or with casing and formation. Micron-scale gaps and cracks are generated at the cemented interface, forming tiny channeling passages, resulting in failure of the annulus seal. At the same time, during the drilling process, external forces such as the collision of running in and the impact of perforation, the high formation pressure in complex blocks and the highly active underground fluid may also easily cause irreversible damage to cement stones with high brittleness and small deformation. damage, and then induce annular channeling after cementing, affecting normal oil and gas production and recovery.

Contents of the invention

The present invention overcomes the problems existing in the background technology and provides a viscoelastic cementing isolation material, which can enhance the anti-channeling isolation ability of the cementing annulus and improve the oil and gas well performance. Cementing and isolation quality.

The present invention can solve the problem through the following technical solutions: a viscoelastic cementing and sealing material, its components and proportions are as follows by mass percentage: high molecular polymer main agent 20-82.5%, crosslinking agent 3- 9%, flow regulator 5-9%, suspending agent 0.5-1%, weighting agent 0-49.5%, water 0-22%.

The raw material components and mass ratio of the crosslinking agent are: 0.5-1 part of chromium propionate, 0.5 part of basic aluminum acetate, 1 part of chromium acetate, and 100 parts of water; And the mass ratio is: 100 parts of sodium silicate, 100 parts of sodium chloride, 50 parts of isopropanol; the raw material components and mass ratio of the suspending agent are: 100 parts of bentonite, 50 parts of PAC-HV high polyanionic cellulose The weighting agent is G grade high sulfur-resistant oil well cement; the preparation process of the high molecular polymer main agent: (1) 2 parts of sodium carboxymethyl cellulose are placed in 100 parts of deionized water by mass ratio , stirred at room temperature for 120-150min until fully dissolved; (2) Weighed 4 parts of acrylamide, 8 parts of acrylic acid, 10 parts of acryloyloxyethyltrimethylammonium chloride and 0.5 parts of methyl methacrylate and poured them into 100 parts In deionized water, stir at room temperature for 20-30min; (3) move the above two groups of solutions into the reaction kettle and stir evenly; (4) under the condition of circulating and cooling tap water, adjust the pH value with 30% sodium hydroxide solution To 7; (5) feed nitrogen and start heating, heat up to the reaction temperature of 60 ° C, and continue to stir for 20 minutes after the temperature is constant; (6) add 0.05 parts of initiator ammonium persulfate, keep warm for 6-12 hours; (7) cool to room temperature, set aside.

The viscoelastic cementing and sealing material has a density of 1.05-1.70×10 ³ kg/m ³ and a service temperature of 20-80°C.

Viscoelastic cementing and sealing materials, through surface graft modification, introduce reactive functional groups into the main chain of polymers, so that they can be used as active metal ions in the cross-linking agent during the cross-linking and curing reaction. The nodes are cross-linked into a regular three-dimensional space network structure, and the texture is flexible and the pressure deformation is large. The rich hydroxyl, carboxyl and amino groups in the molecular chain make the polymer have excellent water retention and excellent sealing performance; at the same time, these groups can also react with cations on the cement stone and formation surface, making the material have good adhesion . Inorganic salts and small molecule alcohols are used as flow regulators to control the curling degree of molecular chains and reduce the reaction rate of active groups. The use of organic cross-linking agents with mild reactions solves the defects of low fluidity of polymer materials, short gelation time and great influence of temperature.

By introducing a small amount of hydrophobic groups into the main chain of the macromolecule, its dispersibility and stability in water are improved; adding silicate to the flow regulator controls the hydration process of oil well cement and reduces the polymer The degree of adsorption of molecules to cement particles, thus solving the defect of poor compatibility with oil well cement when the polymer is added in a large amount.

The viscoelastic cementing packing material is used in combination with oil well cement slurry to form a sandwich structure similar to a "sandwich" in the cementing annulus, which is equivalent to adding an efficient and flexible sealing ring to the hard and brittle cement stone. In downhole working conditions, as the cross-linking reaction progresses, the molecular structure and viscosity of the viscoelastic cementing and sealing material increase, and it is in a viscous liquid state at first. Under the action of formation pressure, the material will be squeezed into the pores and microcracks of the cement stone body and the cement stone-casing, cement stone-formation bonding interface to fill the above-mentioned defects. At this time, the arrangement of the viscous liquid polymer molecules in the narrow gap tends to be relatively tight, and the molecular movement must not only overcome the frictional resistance on the contact surface, but also destroy the van der Waals force and hydrogen bonds between the polymer molecules. Equivalent force, the energy required to change the molecular conformation increases, and the anti-channeling sealing ability increases. The solid phase particles added to the viscoelastic cementing isolation material will also fill the surface or interior of the fracture to form a bridge to ensure sealing. After further cross-linking and forming, the molecular structure of the viscoelastic cementing packing material is arranged neatly and densely, and is in an elastic solid state. Under the action of formation pressure, the material will be compacted to the top cement stone and produce compression deformation, and use its dense molecular structure to fill the sealing gaps everywhere, blocking the leakage of formation fluid and ensuring sealing; the solid phase inside the material The particles will not only improve the flexibility of the polymer main agent, but also form a "labyrinth" sealing effect, thereby improving the overall sealing ability of the material.

In addition, the viscoelastic cementing isolation material can also rely on the viscoelastic deformation of the polymer to convert part of the energy generated by the external force such as the impact of tripping into the heat energy and dissipate it, and the other part is stored in the form of potential energy. Structural damping with good shock absorption effect. Therefore, it can be used as a flexible buffer area to reduce the transmission of stress from the lower part to the upper part of the viscoelastic cementing isolation material, avoiding damage to the upper cement stone and ensuring its integrity and sealing ability.

The present invention uses surface graft modified liquid and curable high molecular polymer as the main agent, and by introducing hydrophobic groups, researching and selecting organic crosslinking agents and high-efficiency flow regulators, the curing time is prolonged and the connection with oil wells is improved. The compatibility of cement and drilling fluid; by optimizing the ratio of suspending agent and weighting agent, the material density is adjusted. The final viscoelastic cementing isolation material has important practical significance and application value for improving the interlayer isolation ability of the cementing annulus, improving the cementing quality of oil and gas wells, and ensuring the security of the national energy strategy.

detailed description:

The present invention will be further described below in conjunction with specific embodiment:

Referring to the national standard GB/T19139-2003 "Oil Well Cement Test Method", the conventional performance of the viscoelastic cementing isolation material at different densities and different experimental temperatures was evaluated. The main experimental instruments are: 30-60 type tile edge stirrer, 7025 type high temperature and high pressure thickening instrument, American CANDLER company; 35SA rotational viscometer, American Fann company. At the same time, the following methods were used to study the channeling resistance and settlement stability of the material.

Evaluation method of anti-channeling isolation ability: The evaluation of anti-channeling isolation ability of cementing isolation materials is mainly based on the gas channeling resistance breakthrough pressure difference and permeability value of the sample. In the national standard GB/T19139-2003, the sample to be tested is placed in the core rubber holder for testing, ignoring the channeling channel caused by the micro-annular gap on the annulus interface. Therefore, in order to more truly reflect the actual working conditions of the downhole dual interface, the present invention uses a solid steel column (33.5mm in diameter, 190.0mm in length) and a dehydration cylinder (53.6mm in inner diameter, 216.0mm in length, and 0.5mm in wall thickness) for use together. The annular space composed of 95/8" casing and 51/2" casing was simulated to study the anti-channeling and isolation ability of cementing materials under the influence of double interface. The main steps are: sequentially inject 30mm high oil well cement, 40mm high material to be tested (the mixed viscoelastic cementing packing material or the oil well cement used as a comparison sample), and 30mm high oil well cement into the above-mentioned annular space, Form a sandwich structure with a total length of 100mm, seal it and move it into a water bath curing box; after curing at the test temperature for a certain period of time, use nitrogen as the channeling medium to pressurize from the bottom of the water loss cylinder to simulate the pressure difference formed from the bottom to the top of the oil and gas well, according to 0.1MPa Continuously pressurize at a rate of /20s (according to the outer diameter of the casing is 139.7mm, the diameter of the drill bit is 215.9mm, the expansion rate of the well diameter is 5%, and the displacement displacement is 1.8m ³ /min), and the pressure is stabilized for 300s for each increase of 0.5MPa, until Until continuous bubbles emerge, the gas channeling pressure difference at this time is the anti channeling breakthrough pressure difference. On this basis, connect the gas outlet on the top of the dehydration cylinder with a "ball" flowmeter, record the gas flow, and calculate the comprehensive permeability K' of the sealing material including the double interface state according to Darcy's law.

${\mathrm{<span\; class="notranslate">\; K</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; \&times;</span>\frac{\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}}$

In the formula:

K′——integrated permeability of the packing material in the double-interface state, μm ² ;

Q——gas flow rate, ml/s;

μ—viscosity of gas, Pa·s;

L - the total length of the sandwich structure, mm;

A - cross-sectional area of the sample, mm ² ;

P _i ——inlet pressure, MPa;

P ₀ ——outlet pressure, MPa;

△P——Pressure difference (P _i -P ₀ ), MPa.

In addition to the cross-linking agent, other substances in the viscoelastic cementing packing material constitute the base fluid of the material. The test method for the stability of the base fluid: weigh the required water according to the ratio of different densities, and use a high-speed stirrer Fully hydrate the suspending agent; move the solution to the slurry cup of the Varin agitator, add the high molecular polymer main agent, flow regulator and other materials in turn at 3500±500r/min, and stir fully; the prepared material Pour it into a 250ml measuring cylinder, seal it and put it into a curing box with a preset temperature, let it stand for 24 hours, test the density of the top and bottom slurry respectively, and calculate the density difference.

The treatment agents used in the following examples are all commercially available, among which, PAC-HV high polyanionic cellulose for drilling fluid was purchased from Beijing Zhongke Risheng Technology Co., Ltd.

Prepare the components:

Weigh 0.5 parts of acid chromium, 0.5 parts of basic aluminum acetate, 1 part of chromium acetate, and 100 parts of water to prepare crosslinking agent; weigh 100 parts of sodium silicate, 100 parts of sodium chloride, and 50 parts of isopropanol Mix and prepare a flow regulator; weigh 100 parts of bentonite and 50 parts of PAC-HV high polyanionic cellulose and mix and prepare a suspending agent.

Preparation of high molecular polymer main agent: (1) according to the mass ratio, put 2 parts of carboxymethylcellulose sodium in 100 parts of deionized water, stir at room temperature for 120-150min until fully dissolved; (2) weigh 4 parts of AM , 8 parts of AA, 10 parts of DAc and 0.5 part of MMA were poured into 100 parts of deionized water, and stirred at room temperature for 20-30min; (3) the above two groups of solutions were moved into the reactor and stirred evenly; (4) circulated in tap water Under cooling conditions, use 30% sodium hydroxide (NaOH) solution to adjust the pH (pH value) to 7; (5) feed nitrogen (N ₂ ) and start heating, and raise the temperature to a reaction temperature of 60°C. After the temperature is constant Continue to stir for 20 minutes; (6) Add 0.05 part of initiator APS, keep warm for 6-12 hours; (7) Cool to room temperature, and discharge for later use.

Example 1

Weighed 82.5g of polymer main agent, 9g of crosslinking agent, and 8.5g of flow condition regulator, respectively, and configured them into a sealing material with a density of 1.05×10 ³ kg/m ³ . The experimental results are shown in Tables 1, 2, and 3. .

Example 2

Weigh 57g of polymer main agent, 7.7g of flow regulator, 0.8g of suspending agent, 6g of cross-linking agent, 9g of water, and 19.5g of oil well cement to configure, and the mass ratio (liquid-solid ratio) of drug solution to oil well cement is 4.13 , with a density of 1.20×10 ³ kg/m ³ , and the experimental results are shown in Tables 1 and 2.

Example 3

Weigh respectively 20g of polymer main agent, 5g of flow conditioner, 0.5g of suspending agent, 3g of crosslinking agent, 22g of water, and 49.5g of oil well cement for configuration, and the mass ratio (liquid-solid ratio) of medicinal liquid to oil well cement is 1.02, The density is 1.70×10 ³ kg/m ³ , and the experimental results are shown in Tables 1 and 2.

Comparative example 1

Grade G oil well cement slurry: Dalian G grade high sulfur-resistant oil well cement 69.4g, tap water 30.5g, the mass ratio of water to oil well cement (liquid-solid ratio) is 0.44, the density is 1.90×10 ³ kg/m ³ , the experimental results See Tables 1 and 2.

Comparative example 2

Drilling fluid system: emulsion polymer drilling fluid, including 4g of bentonite, 0.2g of soda ash, 0.3g of viscosifier, 1g of fluid loss reducer, and a density of 1.05×10 ³ kg/m ³ . The experimental results are shown in Table 3.

Table 1 embodiment and comparative example basic performance evaluation

Compared with Dalian G grade oil well cement slurry, the material of the present invention has good fluidity (24-27cm), long thickening time, and can meet the needs of cementing construction; the free liquid is 0, and the density difference between the upper part and the lower part is small, and there is It is beneficial to improve the isolation ability of the cementing annulus.

Table 2 Evaluation of anti-channeling and sealing capacity of materials

*The safety test pressure of the water loss cylinder is 7MPa

# When the channeling pressure is 7MPa, no air bubbles escape or gas channeling occurs after the pressure is stabilized for 0.5h

The evaluation of anti-channeling isolation ability found that the anti-channeling breakthrough pressure difference and comprehensive permeability of Dalian G grade oil well cement were improved with the increase of curing temperature, but the maximum anti-channeling breakthrough pressure difference within 24 hours did not exceed 0.50 MPa, and the comprehensive permeability was high. . After introducing the 40mm high material of the present invention to form a sandwich structure, the anti-channeling breakthrough pressure difference at 80°C curing temperature for 24 hours increases significantly with the increase of the content of viscoelastic polymer main agent in the material of the present invention, the highest value can be greater than 7MPa, and the comprehensive permeability Compared with oil well cement, it is 1-2 orders of magnitude lower. At the same time, it can be seen from Example 1 that the anti-channeling and sealing ability of the material of the present invention will also increase with the increase of curing temperature.

Table 3 Example 1 Compatibility Research with Oil Well Cement and Drilling Fluid

It can be seen from Table 3 that through the graft modification of the polymer main chain and the use of flow regulators, the defects of easy agglomeration and difficulty in dispersing of traditional polymer materials and solid particles such as oil well cement and clay have been improved, and the performance has been improved. The compatibility of the invention can ensure the safe and smooth progress of cementing construction.

When in use, the density and volume of the prepared material of the present invention are determined according to the formation pressure and isolation height requirements of the cementing construction, and then the corresponding quality of each component is calculated. Usually, the isolation height of the material of the present invention should be in the range of 40-200m downhole. Therefore, the volume of material required for well cementing can be calculated according to the cross-sectional area and height of the wellbore annulus. Wherein, the sum of the volumes of the viscoelastic polymer base fluid, the fluid state regulator, the suspension stabilizer, the weighting agent and the complexing crosslinking agent is the volume of the downhole material of the present invention, that is, the volume of the viscoelastic cementing packing material.

Before the on-site cementing construction starts, pour the crosslinking agent into other substances of the material of the present invention, and mix with a small electric pump for 10-15 minutes. During construction, first inject a certain amount of oil well cement slurry into the annulus of the operating well; then, use a cement truck to mix the material of the invention and the oil well cement as a weighting agent in proportion to the cement truck and inject it continuously and evenly Downhole; finally, inject a certain amount of oil well cement slurry and follow-up clear water or drilling fluid, replace the injected material of the present invention and oil well cement to the predetermined position of the cementing annulus, and form "oil well cement - the present invention" after 200-260min Material-oil well cement "interlayer structure, add a 40-200m high sealing ring to the cementing annulus, so as to improve the anti-channeling and isolation ability of oil and gas wells and improve the cementing quality.

Claims (6)

1. A viscoelastic cementing packing material, its components and proportions are as follows by mass percentage: 20-82.5% of high molecular polymer main agent, 3-9% of cross-linking agent, 5-9% of fluid state regulator , suspending agent 0.5-1wt%, weighting agent 0-49.5%, water 0-22%; The preparation process of the high molecular polymer main agent: (1) according to the mass ratio, put 2 parts of sodium carboxymethylcellulose in 100 parts of deionized water, stir at room temperature for 120-150min until fully dissolved; (2) weigh 4 parts of acrylamide, 8 parts of acrylic acid, 10 parts of acryloyloxyethyltrimethylammonium chloride and 0.5 parts of methyl methacrylate were poured into 100 parts of deionized water, and stirred at room temperature for 20-30min; (3) the above The two groups of solutions are moved into the reaction kettle and stirred evenly; (4) under the condition of circulating cooling of tap water, the pH value is adjusted to 7 with a 30% sodium hydroxide solution; (5) feed nitrogen and start heating, and heat up to the reaction The temperature is 60°C, and after the temperature is constant, continue to stir for 20 minutes; (6) add 0.05 parts of initiator ammonium persulfate, and keep the reaction for 6-12 hours; (7) cool to room temperature, and discharge for later use. 2. A viscoelastic cementing packing material according to claim 1, characterized in that: the raw material components and mass ratios of the crosslinking agent are: 0.5-1 part of chromium propionate, basic aluminum acetate 0.5 parts, 1 part of chromium acetate, 100 parts of water. 3. A viscoelastic cementing packing material according to claim 1, characterized in that: the raw material components and mass ratios of the fluid state regulator are: 100 parts of sodium silicate, 100 parts of sodium chloride , 50 parts of isopropanol. 4. A kind of viscoelastic cementing packing material according to claim 1, characterized in that: the raw material components and mass ratio of the suspension agent are: 100 parts of bentonite, 50 parts of PAC-HV high polyanionic cellulose share. 5. A viscoelastic cementing packing material according to claim 1, characterized in that: the weighting agent is G-grade high sulfur-resistant oil well cement. 6. A viscoelastic cementing isolation material according to claim 1, characterized in that: the density of the viscoelastic cementing isolation material is 1.05-1.07×10 ³ kg/m ³ , and the use temperature is 20 -80°C.