Salt water intrusion resistant drilling fluid and its preparation method and application

Abstract

The present invention provides a saltwater intrusion-resistant drilling fluid, its preparation method, and its application, belonging to the technical field of drilling fluids in oil and gas drilling projects. The system exhibits high-temperature, high-pressure, and high-density resistance, making it suitable for drilling deep wells in high-pressure saltwater formations. The drilling fluid is applicable to formations with a maximum temperature of up to 180°C and can resist 20% high-pressure saltwater intrusion from the formation. The present invention also provides a process for the on-site application of the saltwater intrusion-resistant water-based drilling fluid in drilling operations in complex formations such as deep wells. The saltwater intrusion-resistant water-based drilling fluid of the present invention exhibits strong thermal stability under high-temperature conditions, easily controllable rheological properties, simple performance maintenance, and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling fluid in oil and natural gas drilling projects, and particularly relates to a saltwater intrusion resistant drilling fluid and a preparation method and application thereof. Background Art

[0002] Deep and ultra-deep oil and gas resources are key areas for future exploration and development in my country. However, deep and ultra-deep well drilling involves long openhole sections and complex formations. Furthermore, deep oil and gas resources are mostly capped by salt-gypsum layers, with oil and gas reservoirs developed in the strata beneath them. Drilling operations in the Tarim Basin consistently encounter salt-gypsum layers to varying degrees, with high-pressure brine formations prevalent between these layers. For example, in the Tarim Basin's piedmont tectonic belt, the high-density drilling fluid used can easily squeeze through salt and salt-gypsum layers, causing lost circulation and brine overflow, leading to a series of complex situations such as leakage, collapse, and stuck pipe.

[0003] High-pressure brine layers are mostly developed in thin layers of siltstone or dolomite within thick layers of gypsum salt rock. During the diagenesis process, pore water is not released (low diagenesis degree, good porosity and permeability). Under the action of high temperature and overlying formation pressure, abnormally high pressure occurs, forming high-pressure brine layers. In drilling wells where high-pressure brine layers are developed, the high-temperature and high-density drilling fluid used is often contaminated by the high-pressure brine in the formation. During the drilling process, a large amount of brine and other salt substances often invade or dissolve into the drilling fluid, thereby destroying the stability of the drilling fluid and causing a sharp deterioration in the drilling fluid performance. These are often accompanied by complex situations such as lost circulation, overflow, and stuck pipe. Conventional drilling technology makes it difficult to drill normally and safely, seriously affecting the drilling cycle. Therefore, high-temperature and high-density water-based drilling fluid technology that is resistant to high-pressure brine invasion is still a major technical challenge facing drilling fluids in deep high-pressure brine layers.

[0004] Chinese patent document CN202011125329.2 discloses a high-mineralization water-based drilling fluid and its preparation method. The high-mineralization water-based drilling fluid includes the following raw material components by weight: 4-6 parts of organic bentonite; 2-4 parts of modified asphalt; 0.8-1.5 parts of salt-resistant copolymer; 0.5-1.5 parts of hydrolyzed polyacrylonitrile potassium salt; 2-3 parts of sulfonated lignite resin; 1-4 parts of a lost circulation while drilling agent; 0.2-0.5 parts of a coating agent; 0.5-1 parts of a defoaming agent; 0.3-0.5 parts of sodium carbonate; 0.8-1 parts of sodium hydroxide; and 95-105 parts of brine. The fluid is prepared using on-site brine. However, using brine to prepare drilling fluid at the drilling site significantly affects the performance of the drilling fluid. The prepared drilling fluid has poor colloidal stability, is prone to precipitation and stratification, and cannot effectively suspend and carry rock dust. In addition, formation leakage will also lead to a decrease in drilling fluid density. Too low drilling fluid column pressure can easily lead to well wall instability.

[0005] Chinese patent document CN201410852999.2 discloses a high-density water-based drilling fluid for drilling shale. The components and contents of the raw materials used to prepare the drilling fluid are as follows: 900-1000 parts tap water, 30-60 parts bentonite, 2-4 parts Na2CO3, 1-3 parts CP-1, a polymer anti-salt viscosity inhibitor for drilling fluid, 3-5 parts carboxymethyl starch GMS-1, a high-temperature resistant special resin SPNH-III, 10-30 parts high-temperature resistant viscosity reducer JNT-115-25 parts high-temperature resistant viscosity reducer NL-III, 10-30 parts lubricating nanoemulsion NL-III, 10-20 parts non-fluorescent white asphalt anti-slump agent WBF-II, and water-dispersible cationic emulsified asphalt powder SFT-I. Prepare a 40% alkali solution with NaOH by mass, adjust the system pH to 9, and use the drilling fluid to increase the density of the oil and gas layer protection weighting agent YB-I to 1.8-2.0g / cm 3 The drilling fluid system has the performance of imitating oil-based drilling fluid, but the starch-modified product GMS-1 is used in the drilling fluid, which results in insufficient temperature resistance of the drilling fluid system, with the temperature resistance being lower than 150°C.

[0006] The study "Research and Application of High-Mineralized Brine Drilling Fluid Systems" (Hou Jie et al., Western Mining Engineering) provides a high-mineralized brine drilling fluid system. Based on the selection of inhibitors and plugging agents, the system was optimized for salt-resistant fluid loss reducers and coating agents, and compatibility studies were conducted. The resulting system consists of 1% soil slurry, 1%-1.5% polyol, 5%-7% KCl, 8%-10% NaCl, 1%-1.5% polyamine inhibitor, 2%-2.5% plugging agent, 0.5%-0.8% coating agent, 2%-4% ultrafine calcium carbonate, and 0.05%-0.1% flow modifier. The system exhibits reasonable rheological properties, controllable viscosity and shear, and fluid loss comparable to freshwater drilling fluid. It also exhibits good inhibitory and lubricity properties. However, this system has a temperature tolerance of only 120°C and a clay contamination resistance of 10%.

[0007] A low-soil, high-density, calcium-resistant drilling fluid system (Wang Shuyong et al., Drilling Fluids and Completion Fluids) provides a low-soil, high-density, calcium-resistant drilling fluid system. By using a new viscosity-enhancing and fluid-loss reducer, DSP-1, the dosage of bentonite is reduced, improving the drilling fluid's calcium tolerance while maintaining low fluid loss. The drilling fluid contains near-saturated sodium chloride concentrations, which inhibit the dissolution of salt-gypsum layers. This system withstands temperatures up to 150°C, with an API fluid loss of less than 3.0 mL and a high-temperature and high-pressure fluid loss of less than 15.0 mL, demonstrating strong inhibitory properties.

[0008] Oil-based drilling fluids are widely used for drilling due to their strong resistance to high-pressure brine contamination. However, due to the high preparation costs and significant impact on the surrounding ecological environment, the development of a saltwater-resistant drilling fluid with similar performance to oil-based drilling fluids is urgently needed. Summary of the Invention

[0009] In view of the current technical difficulties faced by high-temperature and high-density water-based drilling fluids in deep and ultra-deep well drilling projects in high-pressure saline layers, such as poor high-temperature stability, rapid deterioration of rheological properties, susceptibility to well collapse, and susceptibility to drilling fluid loss after high-pressure saline intrusion, the present invention provides a salt water intrusion resistant drilling fluid and a preparation method thereof, so as to solve the technical bottleneck problem of high-temperature and high-density water-based drilling fluids resisting high-pressure salt water intrusion during the drilling of deep and ultra-deep wells in high-pressure saline layers.

[0010] Terminology: The saltwater intrusion resistant drilling fluid mentioned in this invention refers to a drilling fluid with a temperature resistance of 150-200°C and a density of 1.45-2.0 g / cm 3 The drilling fluid provided by the present invention has a temperature resistance of up to 180°C and a density value range of 1.60-1.80 g / cm3.

[0011] In order to achieve the above object, the technical solution of the present invention is as follows:

[0012] A high-pressure saltwater intrusion-resistant water-based drilling fluid with a temperature resistance of up to 180°C. The drilling fluid comprises the following components in parts by weight:

[0013] Mixing water: 100 parts

[0014] Soda ash: 0.1-0.2 parts

[0015] Drilling soil: 3-4 parts

[0016] Sodium hydroxide: 0-0.3 parts

[0017] Sodium sulfite: 0-0.3 parts

[0018] Potassium chloride: 5-10 parts

[0019] High temperature and salt resistant sulfonate copolymer: 0.3-1.2 parts

[0020] High temperature and high pressure resistant salt water intrusion resistant polymer fluid loss reducer: 0.5-2 parts

[0021] Concentrated sulfomethylphenolic resin (Type III): 3-7 parts

[0022] Special resin: 2-8 parts

[0023] Asphalt plugging and anti-collapse agent: 2-6 parts

[0024] Flexible plugging and anti-collapse agent: 1-3 parts

[0025] High softening point emulsified asphalt resistant to high temperature, high pressure and salt water intrusion: 2-5 parts

[0026] No. 5 white oil: 0-4 parts

[0027] Emulsifier: 0-1 part

[0028] API standard barite: 0-100 parts, add weight to the required density.

[0029] in:

[0030] The slurry mixing water is tap water or natural fresh water; preferably, the slurry mixing water is tap water.

[0031] The drilling soil is secondary bentonite obtained by sodium modification of calcium-based bentonite.

[0032] The high temperature and salt resistant sulfonate copolymer is a copolymer of 2-acrylamide-2-methylpropanesulfonic acid; preferably, the commercial product code of the high temperature and salt resistant sulfonate copolymer is DSP-1.

[0033] The high temperature and high pressure salt water intrusion resistant polymer fluid loss reducer is a multi-component copolymer formed by free radical polymerization of 2-acrylamide-2-methylpropanesulfonic acid, 2-(dimethylamino)ethyl methacrylate, acryloylmorpholine and acrylamide in aqueous solution;

[0034] The method for preparing the multi-component copolymer comprises the following steps:

[0035] Weigh 19.41g of 2-acrylamide-2-methylpropanesulfonic acid and place it in a 50mL beaker, first dissolve it in 20mL of water, then adjust the pH of the solution to 7-8 with sodium hydroxide, then add 8.875g of acrylamide, 5.7715g of 2-(dimethylamino)ethyl methacrylate and 5.80g of acryloylmorpholine, 0.083g of azobisisobutylimidazoline hydrochloride in the container, add 255mL of deionized water to dissolve completely, pour into a three-necked flask, a magnetic stirrer stirs at a speed of 150r / min, and maintaining the temperature below 20 ℃, after making it mix, then pass through 20min N2 deoxygenation, then be warming up to 50 ℃, react after 4 hours, take out the product in the three-necked flask, use absolute ethanol, acetone to wash repeatedly 3 times, and be placed in 80 ℃ air drying oven and dry for 16h, pulverize and obtain.

[0036] The concentrated sulfonyl phenolic resin (Type III) is a concentrated product obtained by sulfonating a product obtained by a condensation reaction of phenol and formaldehyde; preferably, the commercial product code of the concentrated sulfonyl phenolic resin (Type III) is SMP-3.

[0037] The asphalt-based plugging and anti-collapse agent is sulfonated asphalt powder; preferably, the commercial product code of the asphalt-based plugging and anti-collapse agent is sulfonated asphalt powder and is FT-3.

[0038] The flexible plugging and anti-collapse agent is a water-dispersible asphalt-based high-temperature resistant deformable plugging material; preferably, the commercial product code of the flexible plugging and anti-collapse agent is Flexible Sealing and Anti-collapse Agent Type 1.

[0039] The special resin is a multi-polymerized fluid loss additive modified from humic acid and the like; preferably, the commercial product code of the special resin is KFT-2.

[0040] The high-softening-point emulsified asphalt resistant to high temperature, high pressure and salt water intrusion is a high-softening-point emulsified asphalt plugging and anti-collapse agent prepared from nanoemulsion, with a softening point of 130-50°C.

[0041] The preparation method of the high softening point emulsified asphalt plugging and anti-collapse agent comprises the following steps:

[0042] Take 100 mL of liquid paraffin (No. 5 white oil), weigh the same weight of the surfactants Span 80 and Tween 80 (Span 80:Tween 80 mass ratio of 1:1), and then measure 30 mL of n-butanol. These experimental materials are mixed with 100 mL of tap water (stirred at 3000 rpm for 20 minutes), followed by the addition of 5 g of the cationic gemini surfactant GTN. Stirring is then continued at low speed to form a paraffin nanoemulsion. Next, the paraffin nanoemulsion is heated to 60-70°C, and a colloid mill is started. Once the mill surface temperature rises, the heated paraffin nanoemulsion is poured into the mill. A homemade comb-type polycarboxylate dispersant (30% by weight of the water) is then added, and shear emulsification is performed for 20 minutes. Finally, 200g of high-softening-point emulsified asphalt raw material (purchased from Shandong Qingzhou Tianyi Asphalt Co., Ltd., with a softening point of 130°C-150°C) was weighed and poured into a colloid mill. Under the shear action of the colloid mill, it was shear-emulsified with the paraffin nanoemulsion. After shearing and emulsification for 0.5-1 hour, the fluid in the colloid mill was poured out to obtain a high-temperature-resistant, high-softening-point emulsified asphalt plugging and anti-collapse agent based on the paraffin nanoemulsion. The obtained product has an effective content of the high-softening-point asphalt component of approximately 60%.

[0043] Wherein, the preparation method of the homemade comb-shaped polycarboxylate dispersant is:

[0044] 8.24 g of sodium p-styrene sulfonate, 56 g of allyl alcohol polyoxyethylene ether APEG600 and 3.22 g of methacryloyloxyethyl trimethylammonium chloride were weighed separately, prepared into a deionized water solution, poured into a 250 mL three-necked flask, stirred at high speed for 20 minutes, and then 2.698 g of ammonium persulfate was added to the three-necked flask. Deionized water was added to control the total monomer concentration to 30-35%. Stir and heat to 45 ° C. After deoxygenation with N2 for 30 minutes, the temperature was raised to 80 ° C. and the reaction was carried out for 4 hours to obtain a brown thin colloid. After separation and purification, and after removing water in a vacuum at 90 ° C, a comb-type polycarboxylate strong dispersant was obtained.

[0045] The No. 5 white oil is a refined white mineral oil obtained through conventional purchasing methods.

[0046] The emulsifier is Span80.

[0047] The API standard barite is mainly composed of barium sulfate, with a density of ≥4.2g / cm 3 .

[0048] As some preferred embodiments, the saltwater intrusion resistant water-based drilling fluid has a temperature resistance of up to 180° C. The drilling fluid comprises the following components in parts by weight:

[0049] Mixing water: 100 parts

[0050] Soda ash: 0.2 parts

[0051] Drilling soil: 4 parts

[0052] Sodium hydroxide: 0.3 parts

[0053] Sodium sulfite: 0.3 parts

[0054] Potassium chloride: 6-8 parts

[0055] High temperature and salt resistant sulfonate copolymer: 0.5-0.7 parts

[0056] High temperature and high pressure resistant salt water intrusion resistant polymer fluid loss reducer: 0.5-0.8 parts

[0057] Concentrated sulfomethylphenolic resin (Type III): 4-5 parts

[0058] Special resin: 3-4 parts

[0059] Asphalt plugging and anti-collapse agent: 3-4 parts

[0060] Flexible plugging and anti-collapse agent: 1-2 parts

[0061] High softening point emulsified asphalt resistant to high temperature, high pressure and salt water intrusion: 2-3 parts

[0062] No. 5 white oil: 2-3 parts

[0063] Emulsifier: 0.3-0.5 parts

[0064] API standard barite: 0-100 parts, add weight to the required density.

[0065] The density of the saltwater-resistant drilling fluid prepared in this application can be controlled in the range of 1.60-1.80 g / cm 3 The pH value of the drilling fluid is 8-12, the API medium pressure filtration loss at room temperature is ≤2mL, the high temperature and high pressure filtration loss at 180℃ and a pressure difference of 3.5MPa is ≤12mL, the initial apparent viscosity of the drilling fluid is 45-55mPa·s, and it can resist 20% high-pressure brine intrusion. Under the conditions of on-site maintenance, it can resist up to 30% high-pressure brine intrusion.

[0066] The salt water intrusion resistant water-based drilling fluid of the present invention has a temperature resistance of up to 180° C. and is suitable for use in deep well and ultra-deep well high-pressure salt water layer drilling projects.

[0067] In the salt water intrusion resistant water-based drilling fluid of the present invention, the various constituent raw materials are all commercially available, and any qualified common industrial products are all acceptable.

[0068] The method for preparing the saltwater intrusion resistant drilling fluid comprises the following steps:

[0069] (1) Under high-speed stirring (10,000-12,000 r / min), drilling soil, sodium carbonate and soda ash are added to the slurry water in proportion, stirred for 0.5-1 hour, and then allowed to stand at room temperature for 24 hours to obtain a prehydrated bentonite-based slurry;

[0070] (2) Under high-speed stirring (8000 r / min), sodium hydroxide, sodium sulfite, potassium chloride, high-temperature and salt-resistant sulfonate copolymer, high-temperature and high-pressure salt water intrusion resistant polymer filtration reducer, concentrated sulfomethyl phenolic resin (Type III), special resin, asphalt plugging and anti-collapse agent, flexible plugging and anti-collapse agent, high-temperature and high-pressure salt water intrusion resistant high softening point emulsified asphalt, No. 5 white oil and emulsifier are added to the device containing bentonite-based slurry in proportion every 15-20 minutes. After continuing high-speed stirring for 20 minutes, the drilling fluid is weighted to the corresponding density value using API barite. After continuing stirring for 20 minutes, the salt water intrusion resistant water-based drilling fluid is obtained.

[0071] According to the hot topics in this field, the salt water intrusion resistant water-based drilling fluid described in this invention is generally prepared and used at the drilling site.

[0072] The saltwater intrusion resistant water-based drilling fluid of the present invention is generally used in deep well and ultra-deep well high-pressure saltwater formation drilling projects. The operating temperature is ≤200°C. The drilling site application process is as follows:

[0073] On-site application process method 1:

[0074] Before drilling into the target formation, stop drilling, empty or recover the old slurry in the mud tank, inject slurry water into the mud tank, add drilling soil and soda ash into the slurry water, and continue stirring for 2-3 days to form a pre-hydrated bentonite-based slurry. Under stirring conditions, sodium hydroxide, sodium sulfite, potassium chloride, high-temperature and salt-resistant sulfonate copolymer, high-temperature and high-pressure salt water invasion resistant polymer fluid loss reducer, concentrated sulfomethyl phenolic resin (Type III), special resin, asphalt plugging and anti-collapse agent, flexible plugging and anti-collapse agent, high-temperature and high-pressure salt water invasion resistant high softening point emulsified asphalt, No. 5 white oil, emulsifier and API standard barite are added in sequence. Continue stirring to form a stable colloidal suspension system. Then, under the transportation of the mud pump, the drilling fluid is gradually circulated from "mud tank-into the well-downhole-out of the well-mud tank". The old slurry in the wellbore is emptied or recovered, and the high-pressure salt water layer drilling operation begins.

[0075] On-site application process method 2:

[0076] Before drilling into the high-pressure salt water layer, continue drilling according to the drilling engineering design and strengthen the operation of solid control equipment to remove as much useless solid phase as possible from the drilling fluid. During the normal circulation of the drilling fluid, add dewatering water, drilling soil, soda ash, high-temperature and salt-resistant sulfonate copolymer, high-temperature and high-pressure salt water intrusion-resistant polymer fluid loss reducer, concentrated sulfomethyl phenolic resin (Type III), and API standard barite in sequence. Circulate until all treatment agents are fully dissolved; then add sodium hydroxide, sodium sulfite, potassium chloride, special resin, asphalt plugging and anti-slumping agent, flexible plugging and anti-slumping agent, high-temperature and high-pressure salt water intrusion-resistant high-softening point emulsified asphalt, No. 5 white oil, and emulsifier in sequence. Each treatment agent needs to be circulated for 1-2 cycles to allow the drilling fluid and treatment agent to fully react. After the conversion from the old drilling fluid to the new drilling fluid is completed during the drilling process and the performance is stable, the drilling fluid is tested and adjusted to meet the design requirements before drilling operations into the high-pressure salt water layer begin.

[0077] Compared with the prior art, the present invention has the following advantages:

[0078] (1) The saltwater intrusion-resistant drilling fluid component provided by the present invention contains a high-temperature and high-pressure saltwater intrusion-resistant polymer fluid loss reducer. Adding the polymer fluid loss reducer to the drilling fluid can significantly improve the fluid loss of the drilling fluid after pressure-resistant saltwater intrusion. The high-temperature and high-pressure saltwater intrusion-resistant polymer fluid loss reducer has better resistance to high-pressure saltwater intrusion than similar products at home and abroad.

[0079] (2) The saltwater intrusion-resistant drilling fluid component provided by the present invention contains a high-temperature and high-pressure saltwater intrusion-resistant high-softening-point emulsified asphalt. Adding the high-temperature and high-pressure saltwater intrusion-resistant high-softening-point emulsified asphalt to the drilling fluid can significantly improve the sealing and anti-collapse performance of the drilling fluid after high-pressure saltwater intrusion. The high-temperature and high-pressure saltwater intrusion-resistant high-softening-point emulsified asphalt has better resistance to high-pressure saltwater intrusion than similar domestic products.

[0080] (3) The present invention provides a saltwater-resistant water-based drilling fluid, the density of which can be controlled in the range of 1.60-1.80 g / cm 3 The pH value of the drilling fluid is 8-12, the API medium pressure filtration loss at room temperature is ≤2mL, and the high temperature and high pressure filtration loss at 180℃ and a pressure difference of 3.5MPa is ≤12mL. The initial apparent viscosity of the drilling fluid is 45-55mPa·s, which can directly resist 20% high-pressure brine intrusion. Under the conditions of on-site maintenance, it can resist up to 30% high-pressure brine intrusion.

[0081] (4) Currently, the performance control of water-based drilling fluids on site often becomes uncontrollable after high-pressure saltwater intrusion. Therefore, when a certain amount of high-pressure saltwater intrusion occurs, the on-site practice is usually to discard the drilling fluid contaminated by the high-pressure saltwater intrusion and re-formulate new drilling fluid that meets the on-site construction requirements. Compared with conventional high-temperature, high-density water-based drilling fluids, the saltwater intrusion-resistant water-based drilling fluid provided by the present invention simplifies the daily performance maintenance issues of the drilling fluid during application, reduces the dependence on key treatment agents for ultra-high-temperature drilling fluids produced by foreign countries, and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 Comparison of API filtration loss of various emulsified asphalts before and after high-temperature aging in experimental slurry. DETAILED DESCRIPTION

[0083] The following describes the implementation methods of the present application through specific examples. Those skilled in the art should realize that these specific examples are only to illustrate the specific implementation plans selected to achieve the purpose of the present application, and are not limitations on the technical solutions of the present application.

[0084] Unless otherwise specified, the test methods used in the following examples were performed in accordance with GB16783.1-2014, "Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry - Part 1: Water-Based Drilling Fluids." All raw materials and reagents used in the examples were commercially available unless otherwise specified. The slurry was prepared using tap water; soda ash, drilling soil, sodium hydroxide, sodium sulfite, high-temperature and salt-resistant sulfonate copolymer, concentrated sulfomethylphenolic resin (Type III), specialty resin, asphalt plugging and anti-slumping agent, flexible plugging and anti-slumping agent, No. 5 white oil, emulsifier, and API-standard barite were all obtained from the drilling site. The high-temperature and salt-resistant polymer fluid loss reducer DSP-2 and the foreign high-temperature and salt-resistant polymer fluid loss reducer HE300 were purchased commercially. The high-temperature and high-pressure saltwater intrusion-resistant polymer fluid loss reducer and the high-softening-point emulsified asphalt for high-temperature and high-pressure saltwater intrusion resistance were homemade.

[0085] Basic Example 1 Preparation Method of High-Temperature-Resistant and High-Pressure Salt Water-Invasion-Resistant Polymer Fluid Loss Reducer

[0086] The steps include:

[0087] The high temperature and high pressure salt water intrusion resistant polymer fluid loss reducer is a multi-component copolymer formed by free radical polymerization of 2-acrylamide-2-methylpropanesulfonic acid, 2-(dimethylamino)ethyl methacrylate, acryloylmorpholine and acrylamide in aqueous solution;

[0088] The method for preparing the multi-component copolymer comprises the following steps:

[0089] Weigh 19.41g of 2-acrylamide-2-methylpropanesulfonic acid and place it in a 50mL beaker, first dissolve it in 20mL of water, then adjust the pH of the solution to 7-8 with sodium hydroxide, then add 8.875g of acrylamide, 5.7715g of 2-(dimethylamino)ethyl methacrylate and 5.80g of acryloylmorpholine, 0.083g of azobisisobutylimidazoline hydrochloride in the container, add 255mL of deionized water to dissolve completely, pour into a three-necked flask, a magnetic stirrer stirs at a speed of 150r / min, and maintaining the temperature below 20 ℃, after making it mix, then pass through 20min N2 deoxygenation, then be warming up to 50 ℃, react after 4 hours, take out the product in the three-necked flask, use absolute ethanol, acetone to wash repeatedly 3 times, and be placed in 80 ℃ air drying oven and dry for 16h, pulverize and obtain.

[0090] Test Example 1-1 Evaluation of Fluid Loss Control Performance of High-Temperature and High-Pressure Salt Water Intrusion Resistant Polymer Fluid Loss Control Agent in Composite Salt Water-Based Slurry

[0091] Preparation of composite salt water-based slurry: Pour 400 mL of tap water into a slurry cup, then gradually add 20 g of sodium chloride, 40 g of calcium chloride, and 1 g of sodium bicarbonate at 8000 r / min, stir at high speed for 20 minutes, then add 40 g of evaluation soil, and stir at high speed for 30 minutes to obtain the composite salt water-based slurry.

[0092] Preparation of test slurry: Add 400 mL of composite salt water-based slurry into three high-stirring cups respectively, stir at 8000 r / min for 20 minutes, then add 4 g of high-temperature and high-pressure salt water intrusion resistant polymer fluid loss reducer, high-temperature and salt-resistant polymer fluid loss reducer DSP-2 and foreign high-temperature and salt-resistant polymer fluid loss reducer HE300 into each experimental slurry respectively, and stir at high speed for 30 minutes to fully dissolve them in the composite salt water-based slurry.

[0093] Table 1 Effects of different products on the properties of composite salt-based slurry

[0094]

[0095] Test Example 1-2 Evaluation of the performance of high-temperature and high-pressure saltwater intrusion resistant polymer fluid loss reducer

[0096] Preparation of freshwater base slurry: Add 16g of secondary bentonite for drilling fluid and 0.8g of sodium carbonate to 400mL of tap water respectively, stir at a high speed of 8000 rpm for 30 minutes, scrape the material on the wall of the slurry cup into the slurry, continue high-speed stirring for 2 hours, take out and let it stand for 24 hours to obtain freshwater base slurry.

[0097] Preparation of high-pressure brine: Take a 1L volumetric flask and add 79.4784g of sodium chloride, 30.5059g of potassium chloride, 11.1g of calcium chloride, 1.2627g of magnesium chloride and 1.2704g of ferric chloride into the volumetric flask at 20°C, then add water to make the volume up to 1L to obtain high-pressure brine.

[0098] Preparation of test slurry: Take 3 portions of 400mL freshwater-based slurry and place them in 3 high-stirring cups respectively. After high-speed stirring for 20 minutes, add 80mL of high-pressure brine to the experimental slurry in each high-stirring cup. After high-speed stirring for 30 minutes, add 4g of high-temperature and high-pressure salt water-invasion-resistant polymer fluid loss reducer, high-temperature and salt-resistant polymer fluid loss reducer DSP-2 and foreign high-temperature and salt-resistant polymer fluid loss reducer HE300 to each experimental slurry respectively, and then stir at high speed for 30 minutes to make it fully dissolved in the freshwater-based slurry invaded by high-pressure salt water.

[0099] Table 2 Effects of different products on the performance of freshwater base slurry subjected to high-pressure salt water intrusion

[0100]

[0101]

[0102] According to the test results in Table 1 and Table 2 above, it can be seen that the high-temperature and salt water intrusion-resistant polymer fluid loss reducer provided in the present invention has good resistance to composite salt water intrusion and high-pressure formation salt water intrusion, and its performance is better than similar products at home and abroad.

[0103] Basic Example 2 Preparation Method of High Softening Point Emulsified Asphalt Plugging and Collapse Prevention Agent

[0104] The steps include:

[0105] Take 100 mL of liquid paraffin (No. 5 white oil), weigh the same weight of the surfactants Span 80 and Tween 80 (Span 80:Tween 80 mass ratio of 1:1), and then measure 30 mL of n-butanol. The above measured experimental materials are mixed with 100 mL of tap water (stirred at 3000 rpm for 20 minutes), and then 5 g of the cationic gemini surfactant GTN is added and stirred at low speed to form a paraffin nanoemulsion. Next, the paraffin nanoemulsion is heated to 60-70°C, and a colloid mill is started. After the colloid mill surface temperature rises, the heated paraffin nanoemulsion is poured into the colloid mill. A homemade comb-shaped polycarboxylate dispersant (30% by weight of the water) is then added and shear emulsified for 20 minutes. Finally, 200 g of high-softening-point emulsified asphalt raw material is weighed and poured into the colloid mill. Under the shear action of the colloid mill, the raw material and the paraffin nanoemulsion are shear-emulsified. After shear emulsification for 0.5-1h, pour out the fluid in the colloid mill to obtain a high-temperature resistant and high-softening point emulsified asphalt plugging and anti-collapse agent based on paraffin nanoemulsion. The effective content of the high-softening point asphalt component in the obtained product is about 60%.

[0106] Wherein, the preparation method of the homemade comb-shaped polycarboxylate dispersant is:

[0107] 8.24 g of sodium p-styrene sulfonate, 56 g of allyl alcohol polyoxyethylene ether APEG600 and 3.22 g of methacryloyloxyethyl trimethylammonium chloride were weighed separately, prepared into a deionized water solution, poured into a 250 mL three-necked flask, stirred at high speed for 20 minutes, and then 2.698 g of ammonium persulfate was added to the three-necked flask. Deionized water was added to control the total monomer concentration to 30-35%. Stir and heat to 45 ° C. After deoxygenation with N2 for 30 minutes, the temperature was raised to 80 ° C. and the reaction was carried out for 4 hours to obtain a brown thin colloid. After separation and purification, and after removing water in a vacuum at 90 ° C, a comb-type polycarboxylate strong dispersant was obtained.

[0108] Test Example 2: Test on the Effect of High-Temperature- and High-Pressure-Resistant Saltwater Intrusion-Resistant High-Softening-Point Emulsified Asphalt on the Sealing and Collapse-Preventing Performance of Field Drilling Fluids

[0109] (1) Evaluation of sealing and anti-collapse performance

[0110] Preparation and testing of test slurry: 4 portions of on-site drilling fluid from the SHB5-17H well, 400 mL each, were taken. After stirring each test slurry at high speed for 20 minutes, 20 g of on-site emulsified asphalt No. 1 (emulsified asphalt type I, taken from the site), on-site emulsified asphalt No. 2 (emulsified asphalt type II, taken from the site), on-site emulsified asphalt No. 3 (emulsified asphalt FH, taken from the Seventh Chemical Co., Ltd., Xinxiang City, Henan Province), and high-temperature, high-pressure, and saltwater-intrusion-resistant high-softening-point emulsified asphalt were added to each test slurry. After high-speed stirring, each test slurry was aged at 150°C for 16 hours, and the PPA sand disk plugging performance of each test slurry was tested using a permeability plugging instrument (PPA sand disk model 210538, permeability 10 μm2).

[0111] Table 3 Effects of high-temperature and high-pressure saltwater intrusion resistant high softening point emulsified asphalt and on-site emulsified asphalt samples on the plugging and anti-collapse performance of on-site drilling fluids

[0112]

[0113] (2) Evaluation of resistance to high-pressure salt water intrusion

[0114] Preparation of test slurry: Take 5 parts of fresh water base slurry and place them in a high stirring cup. After stirring at a high speed of 8000r / min for 20 minutes, add the emulsified asphalt sample 1, emulsified asphalt sample 2, emulsified asphalt sample 3, emulsified asphalt sample 4 used on site and the high temperature and salt water invasion resistant high softening point emulsified asphalt provided by the present invention to each test slurry, continue to stir each test slurry at high speed for 20 minutes, and finally add 15% high pressure salt water to each test slurry, and continue to stir at high speed for 30 minutes. Test the API filtration loss of each test slurry before and after high temperature aging at 180°C. The experimental results are as follows: Figure 1 shown.

[0115] According to Table 3 above and Figure 1It can be seen from the experimental test results that the high-temperature and high-pressure salt water intrusion resistant and high-softening point emulsified asphalt plugging and anti-collapse agent provided by the present invention can significantly reduce the leakage of on-site drilling fluid. The PPA leakage of the on-site drilling fluid is 18mL. After the high-temperature and high-pressure salt water intrusion resistant and high-softening point emulsified asphalt plugging and anti-collapse agent provided by the present invention is added to the on-site drilling fluid, the PPA leakage is reduced to 9.6mL and 6.8mL, respectively, which is about 46.7% and 62.2% lower than the PPA leakage of the on-site drilling fluid. At the same time, after the high-temperature and high-pressure salt water intrusion resistant and high-softening point emulsified asphalt plugging and anti-collapse agent provided by the present invention is added to the on-site drilling fluid, the instantaneous filtration loss and static filtration loss rate of the on-site drilling fluid can be significantly reduced. In addition, after the high-temperature and high-pressure salt water intrusion resistant and high-softening point emulsified asphalt plugging and anti-collapse agent provided by the present invention is added to the freshwater base slurry invaded by high-pressure salt water, it has good filtration loss reduction characteristics, and its performance is better than the emulsified asphalt plugging and anti-collapse agent currently used in China.

[0116] Example 1 Saltwater intrusion resistant water-based drilling fluid and preparation method thereof

[0117] The saltwater-resistant water-based drilling fluid has the following formula:

[0118] 400 mL tap water; 8 g drilling soil; 0.4 g sodium carbonate; 1.2 g sodium hydroxide; 1.2 g anhydrous sodium sulfite; 28 g potassium chloride; 2 g high temperature and salt resistance sulfonate copolymer (DSP-1); 2.8 g high temperature and high pressure salt water intrusion resistance polymer fluid loss reducer; 12 g special resin (KFT-2); 20 g sulfomethylated phenolic resin (Type III) (SMP-3); 20 g asphalt plugging and anti-slumping agent (FT-3); 8 g flexible plugging and anti-slumping agent (Flexible plugging and anti-slumping agent Type 1); 12 g high temperature and high pressure salt water intrusion resistance high softening point emulsified asphalt (prepared in Basic Example 2); 12 g No. 5 white oil; 1.2 g Span 80; API standard barite weighted to 1.60 g / cm 3 .

[0119] The preparation method comprises the following steps:

[0120] Add 400 mL of slurry preparation water into a high-stirring cup, and under high-speed stirring (8000-12000 r / min), add 8 g of drilling soil, 0.4 g of sodium carbonate and 1.2 g of sodium hydroxide in sequence. After stirring for 2 hours, seal the mixture and let it stand at room temperature for 24 hours to obtain a prehydrated bentonite-based slurry. Under high-speed stirring at 8000 r / min, 1.2g of anhydrous sodium sulfite, 28g of potassium chloride, 2g of high-temperature and salt-resistant sulfonate copolymer (DSP-1), 2.8g of a polymeric fluid loss reducer resistant to high temperature and high pressure salt water intrusion, 12g of a special resin, 20g of sulfomethylated phenolic resin (Type III), 20g of an asphalt plugging and anti-slumping agent, 8g of a flexible plugging and anti-slumping agent, 12g of a high-softening-point emulsified asphalt resistant to high temperature and high pressure salt water intrusion, 12g of No. 5 white oil, and 1.2g of Span 80 were added to a high-stirring cup containing prehydrated base slurry at 15-20 minute intervals. Stirring was continued for 20 minutes, followed by the addition of barite to the desired density. Stirring was continued for another 20 minutes to obtain a salt water intrusion-resistant water-based drilling fluid. This test slurry was used in the following drilling fluid performance tests.

[0121] Performance Testing

[0122] (1) Drilling fluid performance test

[0123] The prepared saltwater-resistant water-based drilling fluid was placed in an aging tank, heated at 180°C for 16 hours, cooled to room temperature, and then stirred at high speed in a high-pressure agitation cup for 20 minutes. The viscosity, shear strength, medium-pressure fluid loss, and high-temperature and high-pressure fluid loss of each test slurry were measured. The test results are shown in Table 4.

[0124] Table 4 Drilling fluid performance test results in the examples

[0125]

[0126] (2) On-site drilling fluid performance test

[0127] 400 mL of drilling fluid from the Shunbei 53-2H well was placed in an aging tank, heated at 180°C for 16 hours, cooled to room temperature, and then transferred to a high-speed stirring cup for 20 minutes. The viscosity, shear force, medium-pressure fluid loss, and high-temperature and high-pressure fluid loss of each test slurry were measured. The test results are shown in Table 5.

[0128] Table 5 Field drilling fluid performance test results

[0129]

[0130] (3) High-pressure salt water intrusion resistance test

[0131] Two parts of the on-site drilling fluid from Shunbei 53-2H well and two parts of the saltwater-resistant water-based drilling fluid of the present invention were taken, and the drilling fluids were placed in a high-stirring cup. 15% and 20% high-pressure brine were added respectively at a stirring rate of 8000 r / min. After high-speed stirring for 30 minutes, the viscosity, shear force, medium-pressure filtration loss, and high-temperature and high-pressure filtration loss of the experimental slurries were tested before and after hot rolling at 180°C for 16 hours. The test results are shown in Table 6

[0132] Table 6 Test results of high-temperature and high-density drilling fluid's resistance to high-pressure brine intrusion

[0133]

[0134] The experimental test results in Tables 4-6 above show that the on-site drilling fluid and the saltwater intrusion-resistant water-based drilling fluid provided by the present invention have good basic performance. However, the experimental results of the on-site drilling fluid's resistance to high-pressure saltwater intrusion show that 15% high-pressure saltwater intrusion significantly degrades the performance of the on-site drilling fluid, especially the filtration performance. Both 15% and 20% high-pressure saltwater intrusions result in the performance of the on-site drilling fluid failing to meet normal construction requirements. The saltwater intrusion-resistant water-based drilling fluid provided by the present invention can resist 20% high-pressure saltwater intrusion. Even after 20% high-pressure saltwater intrusion, the drilling fluid provided by the present invention can still well meet the technical requirements of on-site construction. When 30% high-pressure saltwater is added to the drilling fluid provided by the present invention after on-site maintenance, it still has good overall performance, and various test results show that it still meets the technical requirements of on-site construction.

[0135] Comprehensive test results show that the salt water intrusion resistant water-based drilling fluid provided by the present invention has good resistance to high-pressure salt water intrusion. The 30% high-pressure salt water intrusion capacity limit makes the salt water intrusion resistant water-based drilling fluid provided by the present invention have performance similar to that of oil-based drilling fluid.

Claims

1. A high-pressure saltwater intrusion resistant water-based drilling fluid, characterized by: The drilling fluid is temperature-resistant up to 180°C and comprises the following components by weight: Mixing water: 100 parts Soda ash: 0.1-0.2 parts Drilling soil: 3-4 parts Sodium hydroxide: 0-0.3 parts Sodium sulfite: 0-0.3 parts Potassium chloride: 5-10 parts High temperature and salt resistant sulfonate copolymer: 0.3-1.2 parts High temperature and high pressure resistant salt water intrusion resistant polymer fluid loss reducer: 0.5-2 parts Concentrated sulfomethylphenolic resin type III: 3-7 parts Special resin: 2-8 parts Asphalt plugging and anti-collapse agent: 2-6 parts Flexible plugging and anti-collapse agent: 1-3 parts High softening point emulsified asphalt resistant to high temperature, high pressure and salt water intrusion: 2-5 parts No. 5 white oil: 0-4 parts Emulsifier: 0-1 part API standard barite: 0-100 parts, add weight to the required density; The high temperature and high pressure salt water intrusion resistant polymer fluid loss reducer is a multi-component copolymer formed by free radical polymerization of 2-acrylamide-2-methylpropanesulfonic acid, 2-(dimethylamino)ethyl methacrylate, acryloylmorpholine and acrylamide in aqueous solution; The special resin is a multi-polymer fluid loss reducer modified from humic acid; The high-softening-point emulsified asphalt resistant to high temperature, high pressure and salt water intrusion is a high-softening-point emulsified asphalt plugging and anti-collapse agent prepared from nanoemulsion, with a softening point of 130-150°C. The preparation method of the high softening point emulsified asphalt plugging and anti-collapse agent comprises the following steps: Take 100 mL of liquid paraffin, weigh the same weight of surfactants Span 80 and Tween 80, with a mass ratio of Span 80 to Tween 80 of 1:1, and then measure 30 mL of n-butanol; blend the above measured experimental materials with 100 mL of tap water, stir at 3000 r / min for 20 min, then add 5 g of cationic gemini surfactant GTN, and stir at low speed to form a nanoemulsion of paraffin; Secondly, the paraffin nanoemulsion is heated to 60-70°C, and the colloid mill is started. After the surface temperature of the colloid mill rises, the heated paraffin nanoemulsion is poured into the colloid mill, and a homemade comb-type polycarboxylate dispersant of 30% by mass of water is added, and shear emulsification is carried out for 20 minutes. Finally, 200g of high-softening-point emulsified asphalt raw material is weighed and poured into the colloid mill. Under the shear action of the colloid mill, it is shear-emulsified with the paraffin nanoemulsion. After shear emulsification for 0.5-1h, the fluid in the colloid mill is poured out to obtain a high-temperature resistant and high-softening-point emulsified asphalt plugging and anti-collapse agent based on paraffin nanoemulsion. The effective content of the high-softening-point asphalt component in the obtained product is 60%. The preparation method of the homemade comb-shaped polycarboxylate dispersant is: 8.24 g of sodium p-styrene sulfonate, 56 g of allyl alcohol polyoxyethylene ether APEG600 and 3.22 g of methacryloyloxyethyl trimethylammonium chloride were weighed separately, prepared into a deionized water solution, poured into a 250 mL three-necked flask, stirred at high speed for 20 minutes, and then 2.698 g of ammonium persulfate was added to the three-necked flask. Deionized water was added to control the total monomer concentration to 30-35%. Stir and heat to 45 ° C. After deoxygenation with N2 for 30 minutes, the temperature was raised to 80 ° C. and the reaction was carried out for 4 hours to obtain a brown thin colloid. After separation and purification, and after removing water in a vacuum at 90 ° C, a comb-type polycarboxylate strong dispersant was obtained.

2. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The slurry mixing water is tap water or natural fresh water.

3. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The drilling soil is secondary bentonite obtained by sodium modification of calcium-based bentonite.

4. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The high temperature and salt resistant sulfonate copolymer is a copolymer of 2-acrylamide-2-methylpropanesulfonic acid.

5. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The method for preparing the multi-component copolymer comprises the following steps: Weigh 19.41g of 2-acrylamide-2-methylpropanesulfonic acid and place it in a 50mL beaker, first dissolve it in 20mL of water, then adjust the pH of the solution to 7-8 with sodium hydroxide, then add 8.875g of acrylamide, 5.7715g of 2-(dimethylamino)ethyl methacrylate and 5.80g of acryloylmorpholine, 0.083g of azobisisobutylimidazoline hydrochloride in the container, add 255mL of deionized water to dissolve completely, pour into a three-necked flask, a magnetic stirrer stirs at a speed of 150r / min, and maintaining the temperature below 20 ℃, after making it mix, then pass through 20min N2 deoxygenation, then be warming up to 50 ℃, react after 4 hours, take out the product in the three-necked flask, use absolute ethanol, acetone to wash repeatedly 3 times, and be placed in 80 ℃ air drying oven and dry for 16h, pulverize and obtain.

6. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The concentrated sulfomethylphenolic resin type III is a concentrated product obtained by sulfonating a product obtained by a condensation reaction of phenol and formaldehyde.

7. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The asphalt-based plugging and anti-collapse agent is sulfonated asphalt powder.

8. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The flexible plugging and anti-collapse agent is a water-dispersible asphalt-based high-temperature resistant deformable plugging material.

9. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The liquid paraffin refers to refined white mineral oil.

10. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The emulsifier is Span80.

11. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The API standard barite is mainly composed of barium sulfate, with a density of ≥4.2g / cm 3 .

12. The high-pressure saltwater intrusion resistant water-based drilling fluid according to claim 1, characterized in that: The drilling fluid has a temperature resistance of up to 180°C and comprises the following components by weight: Mixing water: 100 parts Soda ash: 0.2 parts Drilling soil: 4 parts Sodium hydroxide: 0.3 parts Sodium sulfite: 0.3 parts Potassium chloride: 6-8 parts High temperature and salt resistant sulfonate copolymer: 0.5-0.7 parts High temperature and high pressure resistant salt water intrusion resistant polymer fluid loss reducer: 0.5-0.8 parts Concentrated sulfomethylphenolic resin type III: 4-5 parts Special resin: 3-4 parts Asphalt plugging and anti-collapse agent: 3-4 parts Flexible plugging and anti-collapse agent: 1-2 parts High softening point emulsified asphalt resistant to high temperature, high pressure and salt water intrusion: 2-3 parts No. 5 white oil: 2-3 parts Emulsifier: 0.3-0.5 parts API standard barite: 0-100 parts, add weight to the required density.

13. The method for preparing the saltwater intrusion resistant drilling fluid according to any one of claims 1 to 12, characterized in that: The following steps are involved: (1) Under high-speed stirring conditions, drilling soil, sodium carbonate and soda ash are added to the slurry water in proportion, stirred for 0.5-1 hour, and then allowed to stand at room temperature for 24 hours to obtain a prehydrated bentonite-based slurry; (2) Under high-speed stirring conditions, sodium hydroxide, sodium sulfite, potassium chloride, high-temperature and salt-resistant sulfonate copolymer, high-temperature and high-pressure salt water intrusion resistant polymer filtration reducer, concentrated sulfomethylphenolic resin type III, special resin, asphalt plugging and anti-collapse agent, flexible plugging and anti-collapse agent, high-temperature and high-pressure salt water intrusion resistant high softening point emulsified asphalt, No. 5 white oil and emulsifier are added to the device containing bentonite-based slurry in proportion every 15-20 minutes. After continuing to stir at high speed for 20 minutes, the drilling fluid is weighted to the corresponding density value using API barite. After continuing to stir for 20 minutes, the salt water intrusion resistant water-based drilling fluid is obtained.

Images