A cationic foaming agent system for foam drilling

Abstract

The present invention discloses a high temperature and high salt resistant cationic foaming agent system for foam drilling, which solves the problems of insufficient heat and salt resistance and inhibition performance in the current foam drilling fluid system, and can well meet the requirements of complex formation drilling construction. The foaming agent is composed of the following mass percentages: 20% to 60% of the main foaming agent, 10% to 25% of the auxiliary foaming agent, and the balance of water. The main foaming agent is a quaternary ammonium salt type cationic surfactant containing an alkyl polyglycoside structure, and the auxiliary foaming agent is a zwitterionic surfactant containing a betaine structure. The foaming agent system prepared by the present invention has a temperature resistance of 120°C and a salt resistance of 100,000 mg / L (Ca 2+ 5000mg / L), with excellent foaming effect and good effect in inhibiting shale hydration.

Description

Technical Field

[0001] The invention relates to a foaming system for foam drilling, in particular to formations with frequent upper and lower sand and mudstone interlayers, high hardness, strong abrasiveness and poor drillability, and low-pressure formations with poor well wall stability, and belongs to the field of treating agents for oilfield drilling fluids. Background Art

[0002] Foam drilling is a drilling method that uses a honeycomb foam fluid formed by mixing air or nitrogen and other gases with a foaming agent base liquid as the drilling fluid. The foam fluid has a lower density than conventional mud drilling fluid and a smaller bottom hole clamping effect. It can not only effectively control the circulation loss of drilling fluid and increase the mechanical drilling speed, but also reduce reservoir damage and protect low-pressure oil and gas reservoirs.

[0003] Foam drilling has many advantages, but when drilling in water-sensitive shale formations, the hydration of the shale during the foam drilling process causes the wellbore to become unstable, and the viscosity of the foam circulating base fluid will increase rapidly, thus affecting the recycling of the foam base fluid. During on-site construction, a large amount of clean water is generally added to the base fluid for dilution, and foaming agents are added to maintain the performance of the foam system. This is bound to increase the amount of on-site wastewater and drilling costs, which seriously restricts the promotion and application of foam drilling.

[0004] In order to solve a series of problems caused by shale hydration during foam drilling, most studies have added inhibitors to the foam system to improve the foam system's hydration inhibition performance. This will inevitably increase drilling costs, complicate the system, narrow the performance control window, and bring potential risks to field use. Summary of the invention

[0005] In view of the shortcomings of the current technology, the present invention aims to meet the requirements of inhibiting shale hydration and foam performance during foam drilling. The cationic groups in the molecular structure of glycoside cationic surfactants and betaine zwitterionic surfactants interact with the negative charge on the surface of shale to shorten the distance between clay sheets and squeeze out the interlayer adsorbed water, thereby inhibiting clay hydration. A cationic foam drilling fluid system with both inhibition and foam properties has been developed, which can well meet the requirements of drilling construction in complex formations.

[0006] A cationic foaming agent system for foam drilling, characterized in that the foaming agent system comprises the following components: 20% to 60% of a main foaming agent, 10% to 25% of an auxiliary foaming agent, and the balance of water;

[0007] The main foaming agent is a quaternary ammonium salt cationic surfactant containing an alkyl polyglycoside structure;

[0008] The auxiliary foaming agent is a zwitterionic surfactant containing a betaine structure;

[0009] The structure of the alkyl polysaccharide quaternary ammonium salt cationic surfactant is:

[0010]

[0011] Wherein R1 is a straight chain alkyl group or a branched chain alkyl group having 12 to 18 carbon atoms. 2 A straight chain alkyl group or a branched chain alkyl group having 8 to 16 carbon atoms is selected, and R3 and R4 are straight chain alkyl groups having 1 to 3 carbon atoms, and n=1 to 3.

[0012] The structure of the zwitterionic surfactant auxiliary foaming agent containing betaine structure is:

[0013]

[0014] Where R 5 A straight chain alkyl group or a branched chain alkyl group having 12 to 18 carbon atoms is selected.

[0015] The preferred component of the alkyl polysaccharide quaternary ammonium salt cationic surfactant is 20% to 50%, and the preferred component of the betaine zwitterionic surfactant is 10% to 15%.

[0016] Alkyl polyglycoside quaternary ammonium salt cationic surfactant: R1 is a straight chain alkyl group with 12 to 16 carbon atoms, R 2 A linear alkyl group or a branched alkyl group having 12 to 16 carbon atoms is selected. 3 , R 4 Select -CH 3 .

[0017] Betaine zwitterionic surfactants: R 5 A straight chain alkyl group or a branched chain alkyl group having 12 to 16 carbon atoms is selected.

[0018] The preparation steps of the foaming agent system provided by the present invention are: firstly, adding the main foaming agent into half of the water, slowly stirring until completely dissolved, then adding the auxiliary foaming agent into the other half of the water, slowly stirring until completely dissolved, and finally mixing the above two solutions and slowly stirring evenly.

[0019] The invention is a treating agent in the field of oilfield drilling, which is suitable for formations with frequent sand and mudstone interlayers in the upper formation, high hardness, strong abrasiveness, poor drillability, and low-pressure formations with poor well wall stability.

[0020] The foaming agent system prepared by the present invention has a temperature resistance of 120°C and a salt resistance of 100000mg / L (Ca 2+5000mg / L), good foaming effect, and strong shale hydration inhibition effect. Compared with the prior art, it provides a foaming agent system for foam drilling with excellent comprehensive performance, which can maintain good foaming performance and hydration inhibition performance under complex formation conditions. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the embodiments.

[0022] Embodiment 1:

[0023] Take 20g of alkyl polysaccharide quaternary ammonium salt cationic surfactant (R 1 =C 12 H 25 , R 2 =C 16 H 33 , R 3 =R 4 =CH 3 ), add 35g water and stir slowly; take 10g betaine zwitterionic surfactant (R 5 =C 12 H 25 ), add 35g of water and stir slowly; mix the above two solutions to form a foaming agent, which is foaming agent 1.

[0024] Embodiment 2:

[0025] Take 20g of alkyl polysaccharide quaternary ammonium salt cationic surfactant (R 1 =C 16 H 25 , R 2 =C 14 H 33 , R 3 =R 4 =CH 3 ), add 27.5g water and stir slowly; take 25g betaine zwitterionic surfactant (R 5 =C 12 H 25 ), add 27.5g of water and stir slowly; the above two solutions are mixed to form a foaming agent, which is foaming agent 2.

[0026] Embodiment 3:

[0027] Take 40g of alkyl polysaccharide quaternary ammonium salt cationic surfactant (R 1 =C 12 H 25 , R 2 =C 14 H 33 , R 3 =R 4 =CH3 ), add 25g water and stir slowly; take 10g betaine zwitterionic surfactant (R 5 =C 16 H 25 ), add 25g of water and stir slowly; mix the above two solutions to form a foaming agent, which is foaming agent 3.

[0028] Embodiment 4:

[0029] Take 40g of alkyl polysaccharide quaternary ammonium salt cationic surfactant (R 1 =C 12 H 25 , R 2 =C 14 H 33 , R 3 =R 4 =CH 3 ), add 20g water and stir slowly; take 20g betaine zwitterionic surfactant (R 5 =C 12 H 25 ), add 20g of water and stir slowly; the above two solutions are mixed to form a foaming agent, which is foaming agent 4.

[0030] Embodiment 5:

[0031] Take 50g of alkyl polysaccharide quaternary ammonium salt cationic surfactant (R 1 =C 16 H 25 , R 2 =C 16 H 33 , R 3 =R 4 =CH 3 ), add 20g water and stir slowly; take 10g betaine zwitterionic surfactant (R 5 =C 16 H 25 ), add 20g of water and stir slowly; the above two solutions are mixed to form a foaming agent, which is foaming agent 5.

[0032] Embodiment 6:

[0033] Take 50g of alkyl polysaccharide quaternary ammonium salt cationic surfactant (R 1 =C 16 H 25 , R 2 =C 14 H 33 , R 3 =R 4 =CH 3), add 15g water and stir slowly; take 20g betaine zwitterionic surfactant (R 5 =C 12 H 25 ), add 15g of water and stir slowly; the above two solutions are mixed to form a foaming agent, which is foaming agent 6.

[0034] Embodiment 7:

[0035] Take 60g of alkyl polysaccharide quaternary ammonium salt cationic surfactant (R 1 =C 12 H 25 , R 2 =C 12 H 33 , R 3 =R 4 =CH 3 ), add 15g water and stir slowly; take 10g betaine zwitterionic surfactant (R 5 =C 12 H 25 ), add 15g of water and stir slowly; the above two solutions are mixed to form a foaming agent, which is foaming agent 7.

[0036] Test Example 1:

[0037] Weigh 1g of the above foaming agent and add it to a solution with a mineralization of 100000 mg / L (Ca 2+ The foam performance was measured by high-speed stirring method in simulated water with a concentration of 5000 mg / L.

[0038] Test Example 2:

[0039] Weigh 3g of the above foaming agent, add it to 300g of clean water, then add 20g of rock chips, and after hot rolling at 120°C for 16h, filter the rock chips, dry and weigh them, and measure their hydration inhibition performance.

[0040] Comparative Example 1:

[0041] The specific preparation process is: take a conventional anionic foaming agent system for foam drilling on the market, refer to the methods of Test Example 1 and Test Example 2, measure its foam performance and hydration inhibition performance and compare them with the present invention.

[0042] The specific test data are as follows:

[0043] Table 1 Foam properties

[0044] sample Foam volume / mL Dialysis half-life / min Foam half-life / min Foaming system 1 595 7.4 108 Foaming system 2 605 9.8 112 Foaming system 3 600 7.6 97 Foaming system 4 580 8.1 134 Foaming system 5 640 8.7 105 Foaming system 6 595 7.9 89 Foaming system 7 590 7.0 97 Comparative Example 1 505 5.6 76

[0045] Table 2 Shale hydration inhibition performance

[0046] sample Cuttings rolling recovery rate / % Shimizu 23.6 Foaming system 1 59.4 Foaming system 2 61.4 Foaming system 3 58.3 Foaming system 4 54.8 Foaming system 5 49.9 Foaming system 6 56.1 Foaming system 7 52.7 Comparative Example 1 25.7

[0047] It can be seen from the test data of the above embodiments that the cationic foaming system of the present invention still has excellent foaming performance under high temperature and high salt conditions. At the same time, the rolling recovery rate of rock cuttings in clear water is increased by more than 100%, and the performance in all aspects is better than conventional foaming agents on the market.

Claims

1. A cationic foaming agent system for foam drilling, characterized in that: The foaming agent system includes the following mass components: Main foaming agent 20%~60% Auxiliary foaming agent 10%~25% Water balance; The main foaming agent is a quaternary ammonium salt cationic surfactant containing an alkyl polyglycoside structure; The auxiliary foaming agent is a zwitterionic surfactant containing a betaine structure; The structure of the alkyl polysaccharide quaternary ammonium salt cationic surfactant is: , wherein R1 is a straight chain alkyl group or branched chain alkyl group having 12 to 18 carbon atoms, R2 is a straight chain alkyl group or branched chain alkyl group having 8 to 16 carbon atoms, R3 and R4 are straight chain alkyl groups having 1 to 3 carbon atoms, and n=1 to 3.

2. A cationic foaming agent system for foam drilling as claimed in claim 1, characterized in that: The structure of the zwitterionic surfactant auxiliary foaming agent containing betaine structure is: , wherein R5 is a straight chain alkyl or branched chain alkyl having 12 to 18 carbon atoms.

3. A cationic foaming agent system for foam drilling as claimed in claim 1, characterized in that: The component of the main foaming agent is 20% to 50%, and the component of the auxiliary foaming agent is 10% to 15%.

4. A cationic foaming agent system for foam drilling as claimed in claim 1, characterized in that: Alkyl polysaccharide quaternary ammonium salt cationic surfactant: R1 is a straight-chain alkyl group having 12 to 16 carbon atoms, R2 is a straight-chain alkyl group or a branched-chain alkyl group having 12 to 16 carbon atoms, and R3 and R4 are -CH3.

5. A cationic foaming agent system for foam drilling as claimed in claim 2, characterized in that: Betaine zwitterionic surfactants: R5 is selected from straight-chain alkyl groups or branched-chain alkyl groups having 12 to 16 carbon atoms.

6. A cationic foaming agent system for foam drilling as claimed in claim 1, characterized in that: The preparation steps are: first add the main foaming agent to half of the water, slowly stir until completely dissolved, then add the auxiliary foaming agent to the other half of the water, slowly stir until completely dissolved, and finally mix the above two solutions and slowly stir evenly.

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