Foaming and stabilizing agent for mechanical aerated foam cement slurry and evaluation method

Abstract

The present application belongs to the field of oil field chemistry, and particularly relates to a foaming and stabilizing agent for mechanical aerated foam cement slurry and an evaluation method. The foaming and stabilizing agent is composed of a foaming agent, a stabilizing agent and water; the stabilizing agent is lauric acid monoisopropanol amide. The present application evaluates the stabilizing effect of the foaming and stabilizing agent by comparing the density change of the foam cement slurry before and after heating. The foaming and stabilizing agent has simple components, the foaming agent and the stabilizing agent interact with each other, the surface viscosity of the liquid film is increased while the bubbles are formed, the good stabilizing effect is achieved from the perspective of the foam liquid film, the stabilizing effect is almost not affected by the temperature in the range of less than or equal to 140 DEG C, and the influence on the viscosity performance of the cement slurry is small; and the evaluation method can more truly, more comprehensively, more scientifically and more reliably evaluate the stabilizing effect of the foaming and stabilizing agent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of oilfield chemistry, and particularly relates to a foaming stabilizer suitable for mechanical aerated foam cement slurry and an evaluation method. BACKGROUND

[0002] In the process of oil and gas exploration and development, low pressure and leaky formations are often encountered. When cementing is performed in low pressure and leaky formations, the problems of cement slurry loss and insufficient return are often encountered. To prevent cementing loss, foam cement slurry is often used for cementing.

[0003] Foam cement slurry has elastic-plasticity, compressibility and expandability, which can more fully isolate oil and gas layers; under hydraulic fracturing conditions, it reduces the risk of crack generation and expansion in the cement sheath compared with conventional cement isolation; foam cement slurry can withstand higher casing internal pressure and higher hydrostatic pressure than conventional cement slurry; the mechanical properties of foam cement slurry allow it to withstand greater wellbore pressure than conventional cement; the viscosity of foam cement slurry helps to prevent crack propagation in the cement sheath, ensuring continuous oil layer isolation; foam cement slurry has good heat preservation properties, which can effectively prevent salt crystallization during production, ensuring normal production; and the construction process is one-time return to the wellhead, without the need for staged cementing. In summary, foam cementing has significant advantages and is a research hotspot in recent years, and more and more cementing units are developing foam cement slurry.

[0004] It is generally believed that the core of foam cement slurry is a foaming agent and a foam stabilizer, so scholars have researched a large number of foaming agents and foam stabilizers. However, the foam stabilization effect of foam cement slurry is still a problem affecting its application, mainly in the following aspects:

[0005] (1) Xanthan gum is a commonly used foam stabilizer for foam cement slurry, but it has the disadvantage of significantly thickening the cement slurry, so its addition amount is limited, making it difficult to achieve ideal foam stabilization effect. The existing technology usually complexly combines nanoparticles and hydrophobic association modified hydroxyethyl cellulose on the basis of xanthan gum, but the components have a certain influence on the rheological properties of the cement slurry base.

[0006] (2) The commonly used foam stabilizer for foam cement slurry has good foam stabilization effect at room temperature and normal pressure after being added to the cement base slurry, but as the temperature rises, the viscosity of the foam cement slurry decreases, the gas is more likely to separate, and the foam stabilization effect decreases sharply, limiting the application of foam cement slurry in high temperature environments.

[0007] (3) The existing technology usually adds a foaming stabilizer to the cement base slurry under initial conditions to configure foam cement slurry of a certain density, heats and cures, and compares the upper and lower density differences of the obtained cement stone under the same curing conditions to evaluate the foam stabilization effect, ignoring the comparison of the density of the foam cement slurry under the initial conditions, which has a large error and low reliability. SUMMARY

[0008] In view of the problems in the prior art, the application provides a foaming stabilizer suitable for mechanical aerated foam cement slurry and an evaluation method.

[0009] The foaming stabilizer suitable for the mechanical aerated foam cement slurry comprises a foaming agent, a stabilizer and water, and the stabilizer is lauryl acid monoisopropanol amide.

[0010] The amount of the foaming agent is 10-20% of the mass of water, and the amount of the lauryl acid monoisopropanol amide is 0.1-0.5% of the mass of the foaming agent.

[0011] The foaming agent is one or more of sodium laurate, sodium myristate and sodium palmitate.

[0012] The prior art usually adopts xanthan gum, microsilica and silica sol to increase the viscosity of the cement slurry so that the cement slurry has the foaming stabilizing effect, but the effect of the viscosity increase is reduced with the increase of temperature (Brown motion). The application stabilizes the foam from the perspective of the foam liquid film. The application can cause the shrinkage of the monomolecular layer film area (shrinkage film) by compounding one or more of sodium laurate, sodium myristate and sodium palmitate with the lauryl acid monoisopropanol amide, increase the surface viscosity of the liquid film while forming the bubbles, and achieve the foaming stabilizing effect.

[0013] The evaluation method of the foaming stabilizer comprises the foaming stabilizer, and the specific evaluation steps are as follows.

[0014] (1) configure a cement slurry base slurry, and test the density thereof;

[0015] (2) after the foaming stabilizer is added to the cement slurry base slurry and stirred, the density of the foam cement slurry is recorded as ρ1. 3 1

[0016] (3) after the foam cement slurry is heated, the density of the foam cement slurry after heating is tested and recorded as ρ2.

[0017] (4) ρ2≤0.99ρ1, the foaming stabilizing effect is good; and ρ2>0.99ρ1, the foaming stabilizing effect is not good.

[0018] Specifically, the cement slurry base slurry is first configured, and then the foaming stabilizer, the cement slurry base slurry and nitrogen are mixed in a mixer to generate the foam cement slurry.

[0019] ​​The foaming stabilizer in the application is 4-6% of the mass of cement.

[0020] The stirring speed in step (1) is 2000-4000 rpm.

[0021] The heating temperature of the foamed cement slurry in step (2) is 75℃, and the heating time is 30 min. According to a large amount of field experience, if the foamed cement slurry is heated at 75℃ for 30 min, and ρ2≤0.99ρ1 is met, the working environment of subsequent high temperature cementing within 140℃ can be met. Field construction has been carried out in more than 80 wells, and the foaming stabilizing effect is good, and the cementing quality is stable.

[0022] In the prior art, a foamed cement slurry with a certain density is usually prepared by adding a foaming stabilizer to a cement-based slurry under initial conditions, and the density difference of the obtained cement stone under the same curing condition is compared to evaluate the foaming stabilizing effect. The disadvantages of this evaluation method are: even if gas overflow occurs during the temperature rising and curing process, if the dispersion of the gas that has not overflowed in the cement slurry is still relatively uniform, the density difference of the obtained cement stone under the same curing condition after temperature rising and curing is not large, and an inaccurate conclusion that the foaming stabilizing effect is good is easily drawn. The prior art only considers whether the distribution of the gas that has not overflowed in the cement slurry is uniform, ignores the overflowed gas, and ignores the comparison with the density of the foamed cement slurry before temperature rising and curing, so the error is large and the reliability is low. In the present application, after the foaming stabilizer is added to the cement slurry, the stirring is carried out until the density is reduced by 0.4g / cm 3 , which can ensure that the maximum amount of gas is introduced into the cement slurry. When ρ2≤0.99ρ1, only not more than 10% of the gas overflows, and the foaming stabilizing effect is good; when the gas overflow is more than 10%, ρ2>0.99ρ1, and the foaming stabilizing effect is not good.

[0023] The present application also provides a foaming stabilizer, which comprises the following components by weight: cement 100 parts, polycarboxylic acid thickening type fluid loss additive 1.5 parts, polycarboxylic acid type retarder 1 part, lattice expander 2 parts, early strength agent 1.5 parts, microsilica 5 parts, water 44 parts, and foaming stabilizer 4-6 parts.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] (1) The present application has simple components, the foaming agent and the stabilizing agent interact with each other to increase the surface viscosity of the liquid film while forming bubbles, and good foaming stabilizing effect is achieved from the perspective of the foamed liquid film, which is almost not affected by temperature and has little effect on the viscosity performance of the cement slurry;

[0026] (2) The foaming agent and the matching stabilizing agent selected in the present application are natural substances extracted or modified on the basis of natural substances, and the obtained foaming stabilizer is degradable and has environmental protection advantages;

[0027] (3) The application can more truly, more comprehensively, more scientifically and more reliably evaluate the foam stabilizing effect of the foam stabilizer by comparing the density of the cement slurry before and after the temperature rise of the foam stabilizer. DETAILED DESCRIPTION

[0028] The cement slurry base slurry preparation method is carried out according to "GB / T 19139-2012 Oil Well Cement Test Method". Since the cement slurry loss and thickening time are adjusted by the fluid loss reducer and the retarder, the loss and thickening performance will not be compared and analyzed, and the foam cement slurry stability (the foam stabilizing effect of the foam stabilizer) will be mainly compared and analyzed.

[0029] The cement slurry base slurry uses G-grade oil well cement, the fluid loss reducer is a polycarboxylic acid thickening type fluid loss reducer, and G33S of Weihui City Chemical Co., Ltd. is recommended, and the addition amount is 1.5% of the cement quality; the retarder is a polycarboxylic acid type retarder, and GH-9 of Weihui City Chemical Co., Ltd. is recommended, and the addition amount is 1.0% of the cement quality; the lattice expansion agent is active magnesium oxide, and the addition amount is 2.0% of the cement quality; the early strength agent is sodium sulfate, and the addition amount is 1.5% of the cement quality; and the micro-silicon addition amount is 5% of the cement quality. The water quality is 44% of the cement.

[0030] Example 1

[0031] The foaming agent is sodium laurate, and the addition amount is 10% of the water quality. The lauric acid monoisopropanol amide addition amount is 0.1% of the sodium laurate quality. The foam stabilizer addition amount is 4% of the cement quality. The foam cement slurry sample C1 is configured.

[0032] Example 2

[0033] The foaming agent is sodium myristate, and the addition amount is 20% of the water quality. The lauric acid monoisopropanol amide addition amount is 0.5% of the sodium myristate quality. The foam stabilizer addition amount is 6% of the cement quality. The foam cement slurry sample C2 is configured.

[0034] Example 3

[0035] The foaming agent is sodium palmitate, and the addition amount is 15% of the water quality. The lauric acid monoisopropanol amide addition amount is 0.3% of the sodium palmitate quality. The foam stabilizer addition amount is 5% of the cement quality. The foam cement slurry sample C3 is configured.

[0036] Example 4

[0037] The foaming agent is sodium laurate and sodium myristate, and the mass ratio is 1:1, and the addition amount is 10% of the water quality. The lauric acid monoisopropanol amide addition amount is 0.4% of the total quality of sodium laurate and sodium myristate. The foam stabilizer addition amount is 6% of the cement quality. The foam cement slurry sample C4 is configured.

[0038] Example 5

[0039] The foaming agent is sodium laurate and sodium palmitate with a mass ratio of 1:1, and the amount is 15% of the mass of water. The lauric acid monoisopropanolamide is added in an amount of 0.3% of the total mass of sodium laurate and sodium palmitate. The foaming and stabilizing agent is added in an amount of 5% of the mass of cement. The foam cement slurry sample C5 is prepared.

[0040] Example 6

[0041] The foaming agent is sodium laurate, sodium myristate and sodium palmitate with a mass ratio of 1:1:1, and the amount is 15% of the mass of water. The lauric acid monoisopropanolamide is added in an amount of 0.45% of the total mass of sodium laurate, sodium myristate and sodium palmitate. The foaming and stabilizing agent is added in an amount of 6% of the mass of cement. The foam cement slurry sample C6 is prepared.

[0042] Example 7

[0043] The foaming and stabilizing agent evaluation method includes the following specific steps:

[0044] (1) Prepare a cement slurry base slurry of 500 ml, and test its density;

[0045] (2) After adding the foaming and stabilizing agent to the cement slurry base slurry, stir until the density decreases by 0.4 g / cm 3 , and record the initial density ρ1 of the foam cement slurry sample C1-C6 at room temperature;

[0046] (3) Heat the foam cement slurry sample C1-C6 to 75℃, heat for 30 min, test and record the density ρ2 of the foam cement slurry after heating; and evaluate the stabilizing effect. The results are as follows:

[0047]

[0048] As can be seen from the above table, the density of the foam cement slurry after adding the foaming and stabilizing agent according to the present application is significantly less than the density of the base slurry; after the temperature is increased, the density of the foam cement slurry obtained by adding the foaming and stabilizing agent is ≤0.99ρ1, and the stabilizing effect is good. In the case where no dispersing agent is added, the six-speed rotational viscometer 3 rotation reading is ≥8, and the six-speed rotational viscometer 300 rotation reading is ≤300, indicating that the foaming and stabilizing agent has no effect on the rheological properties of the cement slurry base slurry, and meets the requirements of well cementing construction.

Claims

1. A foaming and stabilizing agent suitable for use in a mechanically aerated foamed cement slurry for cementing, characterized in that, The foaming stabilizer is composed of a foaming agent, a stabilizer and water; the stabilizer is lauric acid monoisopropanolamide; the foaming agent accounts for 10-20% of the mass of water, and the lauric acid monoisopropanolamide accounts for 0.1-0.5% of the mass of the foaming agent; The foaming agent is one or more of sodium laurate, sodium myristate and sodium palmitate; The foaming stabilizer meets the following standards: (1) Add foaming stabilizer to cement slurry base slurry and stir until density is reduced by 0.4 g / cm 3 ; record the density of the foamed cement slurry ; (2) After the foamed cement slurry is heated at 75°C for 30 min, the density of the foamed cement slurry after heating is tested and recorded , ≤0.99 .

2. A foam stabilizer suitable for use in a mechanical aerated foam cement slurry for cementing well, according to claim 1, characterized in that, The addition amount of the foaming stabilizer is 4-6% of the mass of cement in the cement paste base paste.

3. A foaming and stabilizing agent for use in a mechanical aerated foam cement slurry for cementing, according to claim 1, characterized in that, The stirring speed in step (1) is 2000-4000 rpm.

4. A foamed cement slurry, characterized in that, The foaming stabilizer of claim 1 is used, and the raw material composition is: cement 100 parts, polycarboxylic acid tackifying type fluid loss additive 1.5 parts, polycarboxylic acid type retarder 1 part, lattice expander 2 parts, early strength agent 1.5 parts, microsilica 5 parts, water 44 parts, and foaming stabilizer 4-6 parts.

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