An inhibitory water-based foam drilling fluid system

Abstract

This invention discloses an inhibitory water-based foam drilling fluid system to solve the wellbore instability problem currently existing in foam drilling. The system comprises 0.5%-1.0% fluorocarbon foaming agent, 0.2%-1.0% inhibitor, 0.04%-0.2% foam stabilizer, 0.2%-0.4% thickener, 1.0%-5.0% bentonite, and water as the balance. The fluorocarbon surfactant is a fluorocarbon surfactant containing a quaternary ammonium salt cationic structure, the inhibitor is a small-molecule amine salt structure inhibitor, and the large-molecule foam stabilizer is one or more combinations of starch, cellulose, and polyacrylamide. The foaming agent provided by this invention, when applied in foam drilling, possesses both strong foaming and inhibitory properties.

Description

Technical Field

[0001] This invention relates to chemical additives for drilling, specifically to an inhibitory water-based foam drilling fluid system, applicable to drilling, completion, workover, and oil and gas well enhancement measures for large-diameter, ultra-long open-hole wells and horizontal wells, and belongs to the field of oilfield drilling fluid treatment agents. Background Technology

[0002] When gas drilling encounters formation water, appropriate treatment methods are often employed depending on the water volume. However, in field applications, water shut-off or suction operations often fail to achieve satisfactory results. Therefore, gas drilling is typically converted to foam drilling. Compared to conventional drilling fluid drilling, foam drilling, being a gas drilling fluid, offers unique advantages in protecting oil and gas reservoirs and preventing formation loss. It effectively complements gas drilling in addressing formation water issues and significantly improving mechanical drilling speed. Compared to pure gas drilling, foam fluids have higher viscosity and shear strength, stronger suspension and rock-carrying capabilities, and can effectively solve the technical challenges of successful drilling when encountering formation water during gas drilling. It is one of the more ideal drilling technologies for exploring and developing oil and gas reservoirs with large losses, such as fractured reservoirs, pressure-depleted formations, and low-pressure, low-permeability formations. However, current ordinary water-based foam drilling fluid systems generate a large amount of wastewater during drilling. On the one hand, the drilling fluid promotes shale hydration, which rapidly increases the viscosity of the foam-based fluid, requiring the replenishment of clean water and drilling materials. On the other hand, the treatment cost is also very high. This is mainly due to the weak ability of drilling fluid systems to inhibit shale hydration. Developing an inhibitory water-based foam drilling fluid system to suppress shale hydration and improve the utilization rate of foam-based fluids is of great significance. Summary of the Invention

[0003] To overcome the shortcomings of current technology, one of the objectives of this invention is to provide a foaming agent system with strong inhibition properties and simple composition to address the wellbore instability problem in foam drilling.

[0004] The present invention discloses an inhibitory water-based foam drilling fluid system comprising a fluorocarbon foaming agent, an inhibitor, a foam stabilizer, a thickener, bentonite, and water, wherein the weight percentages of each component are as follows: fluorocarbon foaming agent 0.5%-1.0%, inhibitor 0.2%-1.0%, foam stabilizer 0.04%-0.2%, thickener 0.2%-0.4%, bentonite 1.0%-5.0%, and water as the balance.

[0005] The fluorocarbon blowing agent is a fluorocarbon surfactant containing quaternary ammonium salt cations;

[0006] The inhibitor is an inhibitor containing a small molecule amine structure;

[0007] The foam stabilizer is a macromolecular foam stabilizer selected from one or more of starch, cellulose, and polyacrylamide.

[0008] The aforementioned thickener is a thickener treated with quaternary ammonium salt surfactants.

[0009] The molecular structure of the fluorocarbon surfactant containing quaternary ammonium salt cation is as follows:

[0010] , where m = 6~10, n = 1~3.

[0011] The small molecule amine inhibitor is selected from one or a combination of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0012] The aforementioned tackifier is a hydrophobically modified tackifier formed by treating montmorillonite with a quaternary ammonium salt surfactant.

[0013] The preferred composition of the quaternary ammonium salt cationic fluorocarbon surfactant is m = 6-8 and n = 1-2.

[0014] The present invention also provides a method for preparing an inhibitory water-based foam drilling fluid system. The preparation steps are as follows: first, add a fluorocarbon foaming agent to half of the water and stir slowly until completely dissolved; then add an inhibitor to the other half of the water and stir slowly until completely dissolved; finally, mix the two solutions and add a foam stabilizer, a thickener and bentonite in sequence while stirring, and stir slowly until uniform.

[0015] The inhibitory water-based foam drilling fluid system provided by this invention is applicable to the field of oilfield drilling. It is suitable for formations with frequent interbedded sandstone and mudstone in the upper strata, high hardness, strong abrasiveness, and poor drillability, as well as low-pressure formations with poor wellbore stability.

[0016] The advantages of this invention are that it uses fluorocarbon surfactants with specific molecular structures to enhance the foam performance of the system, small molecule amine salts have a strong effect on inhibiting shale hydration, and thickeners and foam stabilizers can enhance the suspension and rock-carrying capacity of the system, thereby achieving the effects of inhibiting collapse, suspending and carrying rock, and rapid drilling.

[0017] Compared with the prior art, the present invention has the following superior effects:

[0018] (1) This foaming agent system can simultaneously possess both strong foaming performance and strong inhibition performance;

[0019] (2) The temperature resistance of this foaming agent can reach 150℃ and the foam half-life can reach more than 50 minutes. Detailed Implementation

[0020] The present invention will be further illustrated below through embodiments, which are intended only to provide a better understanding of the invention and not to limit the scope of protection of the invention. Example 1

[0021] At room temperature, 0.5g of fluorocarbon surfactant (m=8, n=1) was slowly added to a beaker containing 98.06g of water while stirring. After it was completely dissolved, 0.2g of inhibitor diethylenetriamine, 0.04g of polyacrylamide foam stabilizer, 0.2g of thickener, and 1.0g of bentonite were added slowly in sequence. The mixture was stirred for 0.5h to obtain product 1#. Example 2

[0022] At room temperature, 1.0g of fluorocarbon surfactant (m=8, n=2) was slowly added to a beaker containing 92.9g of water while stirring. After it was completely dissolved, 0.5g of tetraethylenepentamine inhibitor, 0.2g of polyacrylamide foam stabilizer, 0.4g of thickener, and 5.0g of bentonite were added in sequence and stirred for 0.5h to obtain product 2#. Example 3

[0023] At room temperature, 1.0g of fluorocarbon surfactant (m=6, n=1) was slowly added to a beaker containing 95.6g of water while stirring. After it was completely dissolved, 1.0g of the inhibitor triethylenetetramine, 0.1g of polyacrylamide foam stabilizer, 0.3g of thickener, and 2.0g of bentonite were added slowly in sequence and stirred for 0.5h to obtain product 3#. Example 4

[0024] At room temperature, 1.0g of fluorocarbon surfactant (m=8, n=2) was slowly added to a beaker containing 93.6g of water while stirring. After it was completely dissolved, 1.0g of inhibitor diethylenetriamine, 0.1g of polyacrylamide foam stabilizer, 0.3g of thickener, and 4.0g of bentonite were added slowly in sequence and stirred for 0.5h to obtain product 4#. Example 5

[0025] At room temperature, 0.5g of fluorocarbon surfactant (m=8, n=2) was slowly added to a beaker containing 93.1g of water while stirring. After it was completely dissolved, 0.8g of the inhibitor triethylenetetramine, 0.2g of polyacrylamide foam stabilizer, 0.4g of thickener, and 5.0g of bentonite were added in sequence and stirred for 0.5h to obtain product 5#. Example 6

[0026] At room temperature, 0.8g of fluorocarbon surfactant (m=6, n=2) was slowly added to a beaker containing 95.06g of water while stirring. After it was completely dissolved, 0.8g of tetraethylenepentamine inhibitor, 0.04g of polyacrylamide foam stabilizer, 0.3g of thickener, and 3.0g of bentonite were added in sequence and stirred for 0.5h to obtain product 6#. Example 7

[0027] At room temperature, 1.0g of fluorocarbon surfactant (m=8, n=2) was slowly added to a beaker containing 93.6g of water while stirring. After it was completely dissolved, 1.0g of the inhibitor triethylenetetramine, 0.1g of polyacrylamide foam stabilizer, 0.3g of thickener, and 4.0g of bentonite were added slowly in sequence and stirred for 0.5h to obtain product 7#.

[0028] Example 8: Performance Evaluation of the Foaming Agent System

[0029] Foaming performance of the foaming agent system: Take 100g of the above sample and pour it into a stirring cup. Stir at 11000rpm for 1min. Start timing after stirring stops. Pour the foam into a graduated cylinder, measure the foam volume, and record the time taken for 50nL of liquid to precipitate (precipitation half-life).

[0030] Inhibition performance of the foaming agent system: The core recovery rate of shale in water and foaming agent solution was tested according to the standard "SY-T5613-2000 Test Method for Physicochemical Properties of Shale". Specific steps: Weigh 20.0g of 4-8 mesh core and add it to a high-temperature aging reactor. Then add 350 mL of the above sample solution system to the aging reactor. After hot rolling at 150℃ for 16 hours, pass the core through a 100-mesh sieve. Dry the residue at 105℃ for 4 hours, cool to room temperature in a desiccator, and weigh. The ratio of the weight of recovered rock cuttings to the initial weight of rock cuttings is the core recovery rate.

[0031] Table 1 Performance Evaluation Results of Blowing Agent

[0032] sample Foam volume / mL half-life of the precipitate / min Rolling recovery rate / % Clear water / / 11.70 Commercially available inhibitory foaming agents 495 7.8 24.60 Product #1 575 57 68.90 Product #2 540 64 72.45 Product #3 530 56 81.02 Product #4 560 59 64.92 Product #5 570 68 59.06 Product #6 555 73 72.38 Product #7 515 57 67.14 .

Claims

1. An inhibitory water-based foam drilling fluid system, characterized in that The weight percentages of the components in the system are as follows: Fluorocarbon foaming agent: 0.5% - 1.0% Inhibitor: 0.2% - 1.0% Foam stabilizer: 0.04% - 0.2% Viscosity increasing agent: 0.2% - 0.4% Bentonite: 1.0% - 5.0% Water: the balance; The fluorocarbon foaming agent is a fluorocarbon surfactant containing quaternary ammonium cation, and its molecular structural formula is: C m F 2m+1 SO2NH(CH2)3N + (C n H 2n+1 )3I - , where: m = 6 to 10, n = 1 to 3; The inhibitor is a small molecule amine inhibitor, selected from one or a combination of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; The foam stabilizer is a macromolecular foam stabilizer, selected from one or a combination of starch, cellulose, and polyacrylamide; The viscosity increasing agent is a hydrophobic modified viscosity increasing agent formed by treating montmorillonite with a quaternary ammonium surfactant.

2. The inhibitory water-based foam drilling fluid system according to claim 1, wherein m = 6 - 8, n = 1 - 2.

3. The preparation method of an inhibitory water-based foam drilling fluid system according to claim 1, characterized in that The preparation steps are as follows: First, add the fluorocarbon foaming agent to a certain amount of water, and slowly stir until completely dissolved. Then, sequentially add the inhibitor, foam stabilizer, viscosity increasing agent, and bentonite, and slowly stir evenly.

4. The application of an inhibitory water-based foam drilling fluid system as described in claim 1, characterized in that It is used in the field of oilfield drilling, and is applicable to formations in the upper part with frequent interbedding of sandstone and mudstone, high hardness, strong abrasiveness, poor drillability, as well as low-pressure formations with poor borehole wall stability.