High-density organic brine drilling and completion fluid and preparation method thereof

Abstract

The invention relates to the technical field of organic salt water drilling and completion fluids, in particular to a high-density organic salt water drilling and completion fluid and a preparation method thereof.The high-density organic salt water drilling and completion fluid is prepared from water, sodium hydroxide, sodium-based montmorillonite, a shale inhibitor, a filtrate reducer, a plugging anti-collapse agent, a lubricant, a high-temperature stabilizer, an organic salt weighting agent, composite barite and a rheological property regulator; the treating agents are mixed in proportion. The mechanical properties of the high-density organic brine drilling and completion fluid are as follows: the temperature resistance is 220 DEG C, the density is 2.0 g / cm < 3 >, the high-temperature and high-pressure filter loss at 150 DEG C is 10mL, the thickness of a mud cake is 5mm, the settling density difference in 24 hours is less than or equal to 0.02 g / cm < 3 >, no coalescence deposition hardened layer exists at the bottom of a tank after standing and aging at the constant temperature of 55 DEG C for 15 days, and the high-density organic brine drilling and completion fluid is excellent in temperature resistance, filter loss performance, salt resistance and calcium resistance; and the anti-sloughing performance and the sedimentation stability are good.

Description

Technical Field

[0001] The invention relates to the technical field of organic brine drilling and completion fluid, in particular to a high-density organic brine drilling and completion fluid and a preparation method thereof. Background Art

[0002] At present, most high temperature treatment agents can maintain the stability of drilling fluid performance at 200°C, but only a few treatment agents have temperature resistance of 200°C to 240°C. The main products are sulfonate polymers, acrylic acid and hydroxypropyl acrylate copolymers, sodium acrylate and ethylene sulfonate copolymers (CDP or TSD), sulfonated styrene and maleic anhydride copolymers SSMA, high temperature and salt resistance fluid loss reducers TSVA, 2-acrylamido-2-methylpropylene sulfonic acid AMPS and acrylamide copolymer COP-1, etc.

[0003] At present, formate brine systems are being recognized and valued by the petroleum industry as drilling fluids and completion fluids. In-depth research has been conducted on sodium formate, potassium formate, calcium formate, and cesium formate brine drilling fluids, especially in the low solid phase and medium-low density formate systems. Sodium formate drilling fluids, potassium formate biopolymer systems, potassium formate-sodium formate mixed brine systems, and potassium formate-potassium acetate polymer systems have been developed and applied on site.

[0004] However, the organic salt-based drilling fluid in the prior art has a low density (≤1.5 g / cm 3 ) and the cost is relatively high. The use of barite in combination makes it difficult to control the rheological properties of the system. High-solid content systems are prone to thickening, solidification, and aggregation instability at high temperatures, which restricts the application of organic brine drilling and completion fluids in drilling in complex formations. Summary of the invention

[0005] The present invention provides a high-density organic salt water drilling and completion fluid and a preparation method thereof, which overcomes the above-mentioned deficiencies of the prior art and can effectively solve the problem of poor rheology of the existing organic salt water-based drilling fluid.

[0006] One of the technical solutions of the present invention is achieved through the following measures: a high-density organic brine drilling and completion fluid, the raw materials include water, the weight of the water is 100%, and the raw materials also include 0.25% sodium hydroxide, 3.0% sodium montmorillonite, 0.1% shale inhibitor, 3.5% filtration reducer, 2.5% plugging and anti-collapse agent, 2.0% lubricant, 0.5% high-temperature stabilizer, 120% organic salt weighting agent, 165% composite barite and 0.8% rheology regulator by weight percentage.

[0007] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: The above-mentioned shale inhibitor is one or more of shale inhibitor JT888, shale inhibitor FA367 and shale inhibitor IND30.

[0008] The above-mentioned fluid loss reducer is one or more of fluid loss reducer BZ-Redu240, fluid loss reducer DSP-1, fluid loss reducer Redu1, fluid loss reducer SMP-2, fluid loss reducer SPNH and fluid loss reducer HRFL.

[0009] The above-mentioned plugging and anti-collapse agent is one or more of non-fluorescent white asphalt NFA-25, natural asphalt powder KH-n (II) and modified asphalt SFT.

[0010] The above lubricant is one or more of lubricant JXFQ-2, lubricant GR-1, lubricant Ultalfree and lubricant PGCS-1.

[0011] The above-mentioned high temperature stabilizer is sodium sulfite.

[0012] The above-mentioned organic salt weighting agent is one or more of organic salt weighting agent weigh2 and organic salt weighting agent weigh3.

[0013] The composite barite is a mixture of conventional barite powder and micron barite powder in a mass ratio of 2:1.

[0014] The above-mentioned rheology regulator is one or more of the rheology regulator VISCO1, rheology regulator xy-27, rheology regulator Desco, rheology regulator Drill-thin and rheology regulator SF260.

[0015] The above-mentioned high-density organic brine drilling and completion fluid is obtained by the following method: S1, adding a required amount of sodium hydroxide and sodium-montmorillonite to a required amount of water and mixing at high speed, and obtaining a prehydrated bentonite-based slurry after curing; S2, add the required amount of shale inhibitor, fluid loss reducer, plugging and anti-collapse agent, lubricant and high-temperature stabilizer to the prehydrated bentonite-based slurry in sequence and mix well, then add the required amount of organic salt weighting agent and rheology regulator in sequence and mix well at high speed to obtain high-density organic brine drilling and completion fluid.

[0016] The second technical solution of the present invention is achieved by the following measures: A method for preparing a high-density organic brine drilling and completion fluid is carried out according to the following method: S1, adding a required amount of sodium hydroxide and sodium-montmorillonite to a required amount of water and mixing at high speed, and obtaining a prehydrated bentonite-based slurry after curing; S2, add the required amount of shale inhibitor, fluid loss reducer, plugging and anti-collapse agent, lubricant and high-temperature stabilizer to the prehydrated bentonite-based slurry in sequence and mix well, then add the required amount of organic salt weighting agent and rheology regulator in sequence and mix well at high speed to obtain high-density organic brine drilling and completion fluid.

[0017] The mechanical properties of the high-density organic brine drilling and completion fluid of the present invention are: temperature resistance of 220°C, density of 2.0g / cm 3 , 150℃ high temperature and high pressure filtration loss is 10mL, mud cake thickness is 5mm, 24-hour sedimentation density difference is ≤0.02g / cm 3 After 15 days of static aging at a constant temperature of 55°C, there is no agglomerated deposition hardened layer on the bottom of the tank. In short, it has excellent temperature resistance, filtration loss resistance, salt resistance and calcium resistance. At the same time, it also has good anti-collapse properties and good settlement stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a comparison chart of shale rolling recovery rates of experimental slurries containing different types of shale inhibitors according to the present invention.

[0019] Figure 2 The figure is a comparison chart of the fluid loss reduction of the experimental pulp containing different types of fluid loss reducers after aging according to the present invention.

[0020] Figure 3 The figure is a comparison chart of the dynamic shear force of the experimental slurry containing different types of rheology regulators after aging according to the present invention.

[0021] Figure 4 This is a comparison chart of shale recovery rates of the high-density organic brine drilling and completion fluid of the present invention.

[0022] Figure 5 This is a comparison chart of shale expansion rates of the high-density organic brine drilling and completion fluid of the present invention. DETAILED DESCRIPTION

[0023] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals known and used in the prior art; unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0024] The present invention will be further described below in conjunction with embodiments: Example 1: The high-density organic brine drilling and completion fluid, the raw materials include water, with the weight of water being 100%, and the raw materials also include, by weight percentage, 0.25% sodium hydroxide, 3.0% sodium-based montmorillonite, 0.1% shale inhibitor, 3.5% filtration reducer, 2.5% plugging and anti-collapse agent, 2.0% lubricant, 0.5% high-temperature stabilizer, 120% organic salt weighting agent, 165% composite barite and 0.8% rheology regulator.

[0025] Example 2: As an optimization of the above example, the shale inhibitor is one or more of the shale inhibitor JT888, the shale inhibitor FA367 and the shale inhibitor IND30.

[0026] Example 3: As an optimization of the above examples, the fluid loss reducer is one or more of the fluid loss reducer BZ-Redu240, fluid loss reducer DSP-1, fluid loss reducer Redu1, fluid loss reducer SMP-2, fluid loss reducer SPNH and fluid loss reducer HRFL.

[0027] Example 4: As an optimization of the above example, the plugging and anti-collapse agent is one or more of non-fluorescent white asphalt NFA-25, natural asphalt powder KH-n (II) and modified asphalt SFT.

[0028] Example 5: As an optimization of the above example, the lubricant is one or more of lubricant JXFQ-2, lubricant GR-1, lubricant Ultalfree and lubricant PGCS-1.

[0029] Example 6: As an optimization of the above example, the high temperature stabilizer is sodium sulfite.

[0030] Example 7: As an optimization of the above example, the organic salt weighting agent is one or more of organic salt weighting agent weigh2 and organic salt weighting agent weigh3.

[0031] Example 8: As an optimization of the above example, the composite barite is a mixture of conventional barite powder and micron barite powder in a mass ratio of 2:1.

[0032] In the present invention, the particle size of conventional barite powder is 40 microns to 50 microns, and the particle size of micron barite powder is 5 microns to 15 microns.

[0033] Example 9: As an optimization of the above example, the rheology regulator is one or more of the rheology regulator VISCO1, rheology regulator xy-27, rheology regulator Desco, rheology regulator Drill-thin and rheology regulator SF260.

[0034] Example 10: As an optimization of the above example, a high-density organic brine drilling and completion fluid is obtained by the following method: S1, adding a required amount of sodium hydroxide and sodium-montmorillonite to a required amount of water and mixing at high speed, and obtaining a prehydrated bentonite-based slurry after curing; S2, add the required amount of shale inhibitor, fluid loss reducer, plugging and anti-collapse agent, lubricant and high-temperature stabilizer to the prehydrated bentonite-based slurry in sequence and mix well, then add the required amount of organic salt weighting agent and rheology regulator in sequence and mix well at high speed to obtain high-density organic brine drilling and completion fluid.

[0035] Compared with the prior art, the present invention has the following beneficial effects: First, the raw material sulfonate copolymer (filtration reducer DSP-1) and carboxyl hydroxy copolymer (filtration reducer Redu240) have strong hydration groups, which can be well dissolved in organic salt solution, and can interact with bentonite to improve the hydration film on the clay surface, which is conducive to the formation of dense mud cakes and enhance the system's filtration reduction performance at high temperatures; the raw material non-fluorescent white asphalt NFA-25 has strong temperature resistance and can soften and deform at high temperatures, thereby squeezing into pores of different sizes, which is conducive to the formation of a dense plugging layer; the raw material high-temperature stabilizer sodium sulfite can consume active oxygen, prevent the oxidative degradation of the treatment agent, and further improve the system's temperature resistance. The synergistic effect of different preferred treatment agents improves the high temperature resistance of organic salt drilling fluid.

[0036] Secondly, the present invention combines an organic salt weighting agent and a composite barite, which effectively solves the defects of the weighting density limitation and high cost of the organic salt weighting agent, and increases the solid capacity limit of the system by compounding conventional barite powder and micron barite powder. It is further combined with a rheology regulator to improve the rheology and colloidal dispersion stability of the high-density organic salt drilling and completion fluid.

[0037] Thirdly, the mechanical properties of the high-density organic brine drilling and completion fluid of the present invention are: temperature resistance 220°C, density 2.0g / cm 3 , 150℃ high temperature and high pressure filtration loss is 10mL, mud cake thickness is 5mm, 24-hour sedimentation density difference is ≤0.02g / cm 3 After 15 days of static aging at a constant temperature of 55°C, there is no agglomerated deposition hardened layer on the bottom of the tank. In short, it has excellent temperature resistance, filtration loss resistance, salt resistance and calcium resistance. At the same time, it also has good anti-collapse properties and good settlement stability.

[0038] Embodiment 11: The high-density organic brine drilling and completion fluid comprises 250 mL of water as raw materials, and based on the weight of water, the raw materials also include 0.25% sodium hydroxide, 3.0% sodium montmorillonite, 0.1% shale inhibitor (shale inhibitor IND30), 3.5% fluid loss reducer (2.0% fluid loss reducer DSP-1+1.5% fluid loss reducer BZ-Redu240), 2.5% plugging and anti-collapse agent (non-fluorescent white asphalt NFA-25), 2.0% lubricant (lubricant PGCS-1), 0.5% high-temperature stabilizer (sodium sulfite), 120% organic salt weighting agent (organic salt weighting agent weigh3), and 165% composite barite (conventional barite powder and micron barite powder with a mass ratio of 2:1, weighted to a density of 2.0 g / cm 3 ) and 0.8% rheology modifier (rheology modifier SF260), obtained as follows: S1, adding a required amount of sodium hydroxide and sodium-montmorillonite to a required amount of water and mixing at high speed, and obtaining a prehydrated bentonite-based slurry after curing; S2, add the required amount of shale inhibitor, fluid loss reducer, plugging and anti-collapse agent, lubricant and high-temperature stabilizer to the prehydrated bentonite-based slurry in sequence and mix well, then add the required amount of organic salt weighting agent and rheology regulator in sequence and mix well at high speed to obtain high-density organic brine drilling and completion fluid.

[0039] Comparative Example 1: The difference from Example 11 of the present invention is that the raw material includes 250 mL of water, and the raw material also includes 0.2% sodium hydroxide, 2.0% sodium montmorillonite, 1.2% filtrate reducer (0.2% filtrate reducer DSP-1 + 1.0% filtrate reducer BZ-Redu240), 6.0% sulfonated phenolic resin SMP-2, 2.0% lignite resin SPNH, 3.0% plugging and anti-collapse agent (non-fluorescent white asphalt NFA-25), 2.0% lubricant (lubricant PGCS-1), 0.5% high temperature stabilizer (sodium sulfite), 60% organic salt weighting agent (organic salt weighting agent weigh2), 165% composite barite (conventional barite powder and micron barite powder with a mass ratio of 4:1, weighted to a density of 2.0 g / cm 3 ) and 1.0% rheology regulator SF260, and the rest of the steps are the same.

[0040] Comparative Example 2: The difference from Example 11 of the present invention is that the raw material includes 250 mL of water, and based on the weight of water, the raw material also includes 0.2% sodium hydroxide, 2.0% rheology regulator VISCO1, 1.5% fluid loss reducer (fluid loss reducer BZ-Redu240), 6.0% sulfonated phenolic resin SMP-2, 2.0% lignite resin SPNH, 2.5% plugging and anti-collapse agent (non-fluorescent white asphalt NFA-25), 3.0% lubricant (lubricant PGCS-1), 0.5% high temperature stabilizer (sodium sulfite), 60% organic salt weighting agent (organic salt weighting agent weigh3), 165% composite barite (conventional barite powder and micron barite powder with a mass ratio of 4:1, weighted to a density of 2.0 g / cm 3 ) and 1.0% rheology regulator SF260, and the rest of the steps are the same.

[0041] Comparative Example 3: The difference from Example 11 of the present invention is that the raw material includes 250 mL of water, and based on the weight of water, the raw material also includes 0.2% sodium hydroxide, 1.5% sodium montmorillonite, 1.0% filtrate reducer (filtrate reducer BZ-Redu240), 6.0% sulfonated phenolic resin SMP-2, 2.0% lignite resin SPNH, 3.0% plugging and anti-collapse agent (non-fluorescent white asphalt NFA-25), 2.0% lubricant (lubricant PGCS-1), 0.5% high temperature stabilizer (sodium sulfite), 70% organic salt weighting agent (30% organic salt weighting agent weigh2 + 40% organic salt weighting agent weigh3), 165% composite barite (conventional barite powder and micron barite powder with a mass ratio of 4:1, weighted to a density of 2.0 g / cm 3 ) and 1.0% rheology regulator SF260, and the rest of the steps are the same.

[0042] Example 12: Optimization test of various raw materials Experiment 1: Optimization of shale inhibitors Test method: Select mud shale cuttings from deep and complex formations in a well in Qinghai Oilfield, crush and take 2mm to 5mm rock samples, and conduct shale rolling dispersion experiments to investigate the shale rolling recovery rate of various polymer treatment agents in organic salt weigh2 aqueous solution. The experimental slurry formula is: 350mL clean water + 20% organic salt weigh2 + 0.8% treatment agent. The experimental slurry is as follows: Experimental slurry 1-1: 300 mL of water Experimental slurry 1-2: Base slurry: 350mL water + 20% organic salt weigh2 Experimental pulp 1-3: base pulp + 0.8% JT888 Experimental pulp 1-4: base pulp + 0.8% FA367 Experimental pulp 1-5: base pulp + 0.8% IND30 Test results: Figure 1 It can be seen that Figure 1 As shown in the figure, the rolling recovery rate of the mudstone cuttings in the deep complex formation in clean water is 50.2%, which is the lowest recovery rate; the rolling recovery rate in the organic salt water slurry is 57.3%; and the rolling recovery rate in the organic salt water solution of 0.8% FA367 is the highest, which is 79.3%, followed by the aqueous solution of 0.8% JT888, which has a recovery rate of 79%. Therefore, the shale inhibitors FA367 and JT888 are more preferred.

[0043] Test 2: Optimization of fluid loss additive Test method: Add BZ-Redu240, DSP-1, Redu1, SMP-2, SPNH and HRFL to the base slurry respectively to optimize the slurry, test the filtration of each experimental slurry before and after aging at 200℃ / 16h, and use the API filtration loss of the experimental slurry after aging as the main evaluation index for selection. The formula of the experimental slurry is: 300mL clean water + 2% Xiazijie soil + 20% organic salt weigh2 + 2% (or 4%) filtration reducer. The experimental slurry is as follows: Experimental slurry 2-1: Base slurry: 300mL water + 2% Xiazijie soil + 20% organic salt weigh2 Experimental slurry 2-2: base slurry + 2% fluid loss reducer BZ-Redu240 Experimental slurry 2-3: base slurry + 2% fluid loss reducer DSP-1 Experimental slurry 2-4: base slurry + 2% fluid loss reducer Redu1 Experimental slurry 2-5: base slurry + 4% fluid loss reducer SMP-2 Experimental slurry 2-6: base slurry + 4% fluid loss reducer SPNH Experimental slurry 2-7: base slurry + 4% HRFL Test results: Figure 2 It can be seen that Figure 2 As shown in the figure, the filtration loss of the experimental slurry with BZ-Redu240 and DSP-1 added after high temperature aging is basically the same, and the filtration loss after high temperature aging is 13mL and 6mL respectively; among the resin and lignite resin filtration reducers, the filtration loss of the experimental slurry with SPNH added after high temperature aging is the smallest, which is 10mL. Therefore, the filtration loss reducer is more preferably BZ-Redu240, DSP-1 and SPNH.

[0044] Test 3: Optimization of plugging and anti-collapse agent Test method: The medium pressure (0.69MPa) sand bed filtration test was used to optimize the non-fluorescent white asphalt NFA-25, natural asphalt powder KH-n (Ⅱ) and modified asphalt SFT, and the drilling fluid invasion depth of each experimental slurry in the sand bed containing 40 mesh to 60 mesh sand (the thickness of the sand bed is 18.5cm) was tested. The depth of drilling fluid invasion into the sand bed after high temperature aging at 200℃ was used as the investigation index to select the plugging and anti-collapse agent with better plugging and anti-collapse agent performance. The experimental slurry formula is: 300mL clean water + 2% Xiazijie soil + 50% organic salt weigh2 + 2% filtration reducer BZ-Redu240 + 4% plugging and anti-collapse agent. The experimental slurry is as follows: Experimental slurry 3-1: Base slurry: 300mL clean water + 2% Xiazijie soil + 50% organic salt weigh2 + 2% filtrate reducer BZ-Redu240 Experimental slurry 3-2: base slurry + 4% non-fluorescent white asphalt NFA-25 Experimental slurry 3-3: base slurry + 4% natural asphalt powder KH-n (Ⅱ) Experimental slurry 3-4: base slurry + 4% modified asphalt SFT Test results: As shown in Table 1, AV is the apparent viscosity, PV is the plastic viscosity, YP is the dynamic shear force, Gel initial cut / final cut and FLAPI are the API water loss. It can be seen from Table 1 that the API filtration loss of the experimental slurry with the addition of modified asphalt SFT before and after aging is smaller. In the 40-mesh to 60-mesh medium-pressure sand bed filtration loss experiment, the immersion depth of the experimental slurry with the addition of non-fluorescent white asphalt NFA-25 is smaller, which is 7 cm. The test shows that among the plugging and anti-collapse agents, the non-fluorescent white asphalt NFA-25 and modified asphalt SFT have the best plugging and anti-collapse performance. Therefore, the plugging and anti-collapse agents are more preferably non-fluorescent white asphalt NFA-25 and modified asphalt SFT.

[0045] Test 4: Lubricant Optimization Test method: The rheological properties, filtration and lubricity of each experimental slurry were tested before and after aging at 200℃ / 16h, and the extreme pressure lubrication coefficient of the experimental slurry after aging was used as the main evaluation index for selection. The formula of the experimental slurry is: 300mL clean water + 2% Xiazijie soil + 20% organic salt weigh2 + 2% lubricant.

[0046] Experimental slurry 4-1: Base slurry: 300mL water + 2% Xiazijie soil + 20% organic salt weigh2 Experimental slurry 4-2: base slurry + 2% lubricant JXFQ-2 Experimental slurry 4-3: base slurry + 2% lubricant GR-1 Experimental slurry 4-4: base slurry + 2% lubricant Ultalfree Experimental slurry 4-5: base slurry + 2% lubricant PGCS-1 Test results: As shown in Table 2, it can be seen from Table 2 that the lubrication coefficient of adding 2% lubricant PGCS-1 to the base slurry is the lowest, and the lubrication coefficients before and after high temperature aging are 0.091 and 0.121 respectively, and the viscosity and shear force of the experimental slurry before and after high temperature aging remain basically unchanged, and the filtration loss is also low, indicating that lubricant PGCS-1 has good lubricity and thermal stability under high temperature environment; Utralfree has the second best lubricity, and the lubrication coefficients before and after high temperature aging are 0.130 and 0.145 respectively. Therefore, the lubricant is more preferably lubricant PGCS-1.

[0047] Test 5: Optimization of rheology modifier Rheology modifiers xy-27, Desco, Drill-thin and SF260 were added to the base slurry to select the rheology modifiers. The rheology, filtration and lubricity of each experimental slurry were tested before and after aging at 200℃ / 16h, and the shear value of the experimental slurry after aging was used as the main evaluation index for selection. The formula of the experimental slurry is: 250mL water + 0.25% NaOH + 3.0% Xiazijie soil + 0.1% IND30 + 2.0% DSP-1 + 1.5% BZ-Redu240 + 2.5% NFA-25 + 2.0% PGCS-1 + 0.5Na2SO3 + 120% weigh3 + 165% composite barite (conventional barite powder and micron barite powder with a mass ratio of 2:1, weighted to a density of 2.0g / cm 3 )+0.8% rheology regulator.

[0048] Experimental slurry 5-1: Base slurry: 250mL water + 0.25% NaOH + 3.0% Xiazijie soil + 0.1% IND30 + 2.0% DSP-1 + 1.5% BZ-Redu240 + 2.5% NFA-25 + 2.0% PGCS-1 + 0.5Na2SO3 + 120% weigh3 + 165% composite barite (conventional barite powder and micron barite powder with a mass ratio of 2:1, weighted to a density of 2.0g / cm 3 ) Experimental slurry 5-2: base slurry + 0.8% rheology modifier xy-27 Experimental slurry 5-3: base slurry + 0.8% rheology modifier Desco Experimental slurry 5-4: base slurry + 0.8% rheology modifier Drill-thin Experimental slurry 5-5: base slurry + 0.8% rheology regulator SF260 Test results: Figure 3 It can be seen that Figure 3As shown in the figure, after aging at 200℃ / 16h, the experimental slurry with the addition of rheology regulator SF260 can still maintain a relatively high shear force value of 10Pa, which meets the rheological property requirements of organic salt drilling fluid. Therefore, the rheology regulator SF260 is preferably used.

[0049] Example 13: Investigating the rheological properties, filtration loss and sedimentation stability of the high-density organic brine drilling and completion fluid of the present invention. Specifically, the rheological properties and filtration loss of the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention before and after aging at 220°C / 16h, as well as the sedimentation stability after aging for 24 hours were investigated, and comparative examples 1 to 3 were used as controls.

[0050] The test results are shown in Table 3. It can be seen from Table 3 that in Comparative Examples 1 to 3 of the present invention, since the raw materials sulfonated phenolic resin SMP-2 and lignite resin SPNH cannot withstand the high temperature of 220°C, the polymer is degraded, resulting in a low viscosity of the entire drilling fluid system, a high filtration loss, and an unstable system. The high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention has a density difference of 0.01, good filtration loss, and the best sedimentation stability.

[0051] Example 14: The comprehensive performance of the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention was evaluated. The comprehensive performance includes rheological filtration performance, temperature resistance, anti-pollution performance, anti-collapse performance and sedimentation stability performance.

[0052] Test 1: Rheological Fluid Loss Performance Test method: The rheological filtration performance of the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention before and after hot rolling at 220°C / 16h and the high-temperature and high-pressure filtration loss at 150°C / 3.5MPa were investigated.

[0053] Test results: As shown in Table 4, FL HTHP It is the filtration loss of drilling fluid under high temperature and high pressure. It can be seen from Table 4 that the viscosity of the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention increases after aging, the φ600 test value exceeds the range, the filtration loss decreases after aging, and the high temperature and high pressure filtration loss is 10 mL, and the filtration loss performance is excellent.

[0054] Test 2: Temperature resistance Test method: The rheological filtration properties of the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention were investigated before and after hot rolling at 225°C / 16h.

[0055] Test results: As shown in Table 5, it can be seen from Table 5 that after the aging temperature of the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention reaches 225°C, the viscosity increases, the φ600 test value exceeds the range, the filtration loss decreases, and the temperature resistance can basically meet the requirements.

[0056] Test 3: Anti-pollution performance Test method: The salt resistance, calcium resistance and inferior soil resistance of the high-density organic brine drilling and completion fluid of the present invention were investigated. Specifically, NaCl, CaCl2 and inferior soil (rock powder taken from complex formations in deep wells of Qinghai Oilfield) were added to the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention, and the rheological properties (including initial cutting / final cutting) and filtration loss properties were tested before and after aging at 220°C / 16h.

[0057] Test results: As shown in Table 6, it can be seen from Table 6 that after adding 10% NaCl to the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention, the viscosity is reduced compared with the base slurry, but the filtration loss is increased, and the salt resistance basically meets the requirements; after adding 1.0% CaCl2 to the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention, the viscosity does not change much before and after, the filtration loss is reduced, and the calcium resistance is good; after adding 8% reservoir poor soil to the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention, the viscosity rises sharply, exceeds the range, and the poor soil resistance is poor.

[0058] Test 4: Anti-collapse performance Test method: The evaluation of the anti-collapse performance includes the evaluation of the inhibition of shale hydration dispersion performance and the shale hydration expansion performance.

[0059] The method for evaluating the hydration inhibition and dispersion performance of mudstone is to select rock samples from deep complex formations in Qinghai Oilfield, and to evaluate the shale inhibition of the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention and the drilling fluid of the on-site Alkali Exploration 1 well and the drilling fluid of the Jianbei 1 well through a shale rolling dispersion recovery rate experiment.

[0060] The method for evaluating the hydration swelling performance of shale is to select rock samples from deep formations in the Qinghai Oilfield and evaluate the shale inhibition of the high-density organic brine drilling and completion fluid and the on-site well slurry prepared in Example 11 through a shale swelling experiment.

[0061] Test results: The results of inhibiting shale hydration and dispersion performance are as follows Figure 4 As shown by Figure 4 It can be seen that the shale recovery rate of the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention reaches 93.02%, which is 42.82% higher than 50.2% in clean water, 1.75% higher than 91.27% in the on-site alkaline exploration 1 well system, and 14.52% higher than 78.5% in the Jianbei 1 well system. This shows that the high-density organic brine drilling and completion fluid of the present invention has good anti-collapse performance.

[0062] The results of shale hydration expansion performance are as follows Figure 5 As shown by Figure 5It can be seen that the high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention has the smallest expansion rate, and the 8h expansion rate is only 1.64%; while the expansion rate of complex formation rock powder in clean water is the largest, and the 8h expansion rate is as high as 12.67%. The experimental results show that the high-density organic brine drilling and completion fluid of the present invention can effectively reduce the hydration expansion of rock samples.

[0063] Test 5: Sedimentation stability performance Test method: The high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention is placed in a constant temperature box at 55° C., and its sedimentation stability and density difference are regularly observed.

[0064] Test results: The high-density organic brine drilling and completion fluid prepared in Example 11 of the present invention still has good sedimentation stability after being placed in a 55°C constant temperature box for 15 days. The density difference monitoring in the first week was maintained at a low level. On the 9th day, the density difference increased and the bottom began to consolidate. On the 16th day, the bottom consolidated and began to agglomerate. After 15 days of static aging, there was no sedimentation hardening layer on the bottom of the tank, which basically met the requirements of the on-site drilling fluid.

[0065] In summary, the mechanical properties of the high-density organic brine drilling and completion fluid of the present invention are: temperature resistance 220°C, density 2.0g / cm 3 , 150℃ high temperature and high pressure filtration loss is 10mL, mud cake thickness is 5mm, 24-hour sedimentation density difference is ≤0.02g / cm 3 After 15 days of static aging at a constant temperature of 55°C, there is no agglomerated deposition hardened layer on the bottom of the tank. In short, it has excellent temperature resistance, filtration loss resistance, salt resistance and calcium resistance. At the same time, it also has good anti-collapse properties and good settlement stability.

[0066] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A high-density organic brine drilling and completion fluid, characterized in that The raw materials include water, with the weight of water being 100%. The raw materials also include, by weight percentage, 0.25% sodium hydroxide, 3.0% sodium montmorillonite, 0.1% shale inhibitor, 3.5% filtration reducer, 2.5% plugging and anti-collapse agent, 2.0% lubricant, 0.5% high-temperature stabilizer, 120% organic salt weighting agent, 165% composite barite and 0.8% rheology regulator.

2. The high-density organic brine drilling and completion fluid according to claim 1, characterized in that The shale inhibitor is one or more of shale inhibitor JT888, shale inhibitor FA367 and shale inhibitor IND30.

3. The high-density organic brine drilling and completion fluid according to claim 1 or 2, characterized in that The fluid loss reducer is one or more of fluid loss reducer BZ-Redu240, fluid loss reducer DSP-1, fluid loss reducer Redu1, fluid loss reducer SMP-2, fluid loss reducer SPNH and fluid loss reducer HRFL.

4. The high-density organic brine drilling and completion fluid according to any one of claims 1 to 3, characterized in that The plugging and anti-collapse agent is one or more of non-fluorescent white asphalt NFA-25, natural asphalt powder KH-n and modified asphalt SFT.

5. The high-density organic brine drilling and completion fluid according to any one of claims 1 to 4, characterized in that The lubricant is one or more of lubricant JXFQ-2, lubricant GR-1, lubricant Ultalfree and lubricant PGCS-1.

6. The high-density organic brine drilling and completion fluid according to any one of claims 1 to 5, characterized in that The high temperature stabilizer is sodium sulfite; or / and, the organic salt weighting agent is one or more of organic salt weighting agent weigh2 and organic salt weighting agent weigh3.

7. The high-density organic brine drilling and completion fluid according to any one of claims 1 to 6, characterized in that The composite barite is a mixture of conventional barite powder and micron barite powder in a mass ratio of 2:

1.

8. The high-density organic brine drilling and completion fluid according to any one of claims 1 to 7, characterized in that The rheology regulator is one or more of the rheology regulator VISCO1, rheology regulator xy-27, rheology regulator Desco, rheology regulator Drill-thin and rheology regulator SF260.

9. The high-density organic brine drilling and completion fluid according to any one of claims 1 to 8, characterized in that Obtained as follows: S1, adding a required amount of sodium hydroxide and sodium-montmorillonite to a required amount of water and mixing at high speed, and obtaining a prehydrated bentonite-based slurry after curing; S2, add the required amount of shale inhibitor, fluid loss reducer, plugging and anti-collapse agent, lubricant and high-temperature stabilizer to the prehydrated bentonite-based slurry in sequence and mix well, then add the required amount of organic salt weighting agent and rheology regulator in sequence and mix well at high speed to obtain high-density organic brine drilling and completion fluid.

10. A method for preparing a high-density organic brine drilling and completion fluid according to any one of claims 1 to 8, characterized in that Proceed as follows: S1, adding a required amount of sodium hydroxide and sodium-montmorillonite to a required amount of water and mixing at high speed, and obtaining a prehydrated bentonite-based slurry after curing; S2, add the required amount of shale inhibitor, fluid loss reducer, plugging and anti-collapse agent, lubricant and high-temperature stabilizer to the prehydrated bentonite-based slurry in sequence and mix well, then add the required amount of organic salt weighting agent and rheology regulator in sequence and mix well at high speed to obtain high-density organic brine drilling and completion fluid.

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