Strong plugging type oil-based drilling fluid system suitable for fractured formation and preparation method of strong plugging type oil-based drilling fluid system

Abstract

The invention relates to a strong plugging type oil-based drilling fluid system suitable for a fractured formation and a preparation method thereof, the oil-based drilling fluid system comprises the following components by mass: 70-80 parts of base oil, 3-5 parts of an integrated emulsifier, 1-3 parts of an alkalinity regulator, 2-4 parts of a liquid filtrate reducer, and 1.5-3 parts of an oil-based efficient tackifying and shear strength improving agent, 1.5-3.0 parts of a multi-stage crack plugging agent and 0-80 parts of a weighting material. The strong-plugging oil-based drilling fluid is wide in application range, the density can be adjusted between 0.9 g / cm < 3 > and 2.2 g / cm < 3 >, and the strong-plugging oil-based drilling fluid has relatively good rheological property, suspension stability and filter loss control capability in a range of 60-170 DEG C and can be applied to shale gas drilling construction of a fractured formation.

Description

Technical Field

[0001] The invention relates to drilling fluid, and more particularly to a strong plugging oil-based drilling fluid system suitable for fractured formations and a preparation method thereof. Background Art

[0002] Oil-based drilling fluids are increasingly widely used due to their good lubricity, strong anti-pollution ability, excellent wellbore stability and shale inhibition, wide temperature adaptability range, and can effectively protect water-sensitive formations and improve mechanical drilling speed. Compared with water-based drilling fluids, the rheological properties of oil-based drilling fluids are more difficult to control. Currently, organic soil is mainly used as a viscosity-enhancing and shear-enhancing agent to improve its rheological properties and enhance its suspension and carrying capacity for weighted materials and drill cuttings. As the horizontal section of shale gas wells gradually extends, the construction of fractured formations requires drilling fluids to have good rheological properties and rock and sand carrying capabilities to ensure the overall mechanical drilling speed. Excessive addition of organic soil in existing oil-based drilling fluids will cause the overall viscosity of the drilling fluid to be too high, the initial and final cuts to be too high, and the overall flow pattern of the drilling fluid to be weakened. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a strong plugging oil-based drilling fluid system suitable for fractured formations with high shear force, low viscosity, good rheological properties and strong plugging properties, and a preparation method thereof, which can improve drilling efficiency and effectively save costs.

[0004] The technical solution adopted by the present invention to solve the technical problem is: constructing a strong plugging type oil-based drilling fluid system suitable for fractured formations, comprising the following components, calculated by mass: 70-80 parts of base oil, 3-5 parts of integrated emulsifier, 1-3 parts of alkalinity regulator, 2-4 parts of liquid filtrate reducer, 1.5-3 parts of oil-based high-efficiency viscosity-enhancing and shear-enhancing agent, 1.5-3.0 parts of multi-stage fracture plugging agent, and 0-80 parts of weighting material.

[0005] According to the above scheme, the integrated emulsifier comprises the following components, calculated by mass fraction: 30% of sorbitan monooleate, 30% of oleic acid diethanolamide, and 40% of methyl erucate.

[0006] According to the above scheme, the liquid fluid loss reducer is SSC-FL liquid fluid loss reducer. The liquid fluid loss reducer is a modified compound obtained by chemically modifying plant asphalt with anhydride through a diene synthesis method and dissolved in an organic solvent.

[0007] According to the above scheme, the oil-based high-efficiency viscosity-enhancing and shear-enhancing agent is SSC-MOD oil-based high-efficiency viscosity-enhancing and shear-enhancing agent. The oil-based high-efficiency viscosity-enhancing and shear-enhancing agent is a high-efficiency viscosity-enhancing and shear-enhancing agent for oil-based drilling fluid developed by suspension polymerization using materials such as styrene, alkoxylated fatty acids, methyl methacrylate and 16-hexadecene.

[0008] According to the above scheme, the multi-stage crack plugging agent includes plant fiber plugging particles and nanometer plugging particles. For cracks within 0.5 mm, the mass ratio of the two is plant fiber plugging particles: nanometer plugging particles = 1:2.

[0009] According to the above scheme, the multi-stage crack plugging agent includes plant fiber plugging particles and nanometer plugging particles. For cracks within 0.5mm-1.5mm, the mass ratio of the two is plant fiber plugging particles: nanometer plugging particles = 1:1.

[0010] According to the above scheme, the multi-stage crack plugging agent includes plant fiber plugging particles and nano plugging particles. For cracks within 1.5mm-3.0mm, the mass ratio of the two is plant fiber plugging particles: nano plugging particles = 2:1.

[0011] The present invention also provides a method for preparing a strong plugging type oil-based drilling fluid system suitable for fractured formations, comprising the following steps:

[0012] At room temperature, in the slurry preparation cup, add the oil phase, integrated emulsifier, alkalinity regulator, saturated calcium chloride brine, liquid filtrate reducer, oil-based high-efficiency viscosity enhancer and shear enhancer, and weighting material in this order to form a strong plugging oil-based drilling fluid system. After adding each liquid phase material, it is necessary to stir at a variable speed for 15-20 minutes before adding another material, and the stirring speed shall not be less than 6000rpm; after adding each solid phase material, it is necessary to stir at a variable speed for 25-30 minutes before adding another material, and the stirring speed shall not be less than 8000rpm. After weighting with the weighting material, stir at a variable speed for 60-90 minutes, and the stirring speed shall not be less than 12000rpm.

[0013] The strong plugging oil-based drilling fluid system suitable for fractured formations and the preparation method thereof of the present invention have the following beneficial effects:

[0014] 1) The system formula of the product of the present invention is based on the conventional oil-based drilling fluid formula, by optimizing the solid-liquid ratio, selecting a liquid-phase fluid loss reducer with the same effect to replace the granular fluid loss reducer, and introducing SSC-MOD oil-based drilling fluid shearing agent into the system formula to replace the solid organic soil, thereby improving the shear force of the system and reducing the solid content by 4-8%;

[0015] 2) Strong plugging oil-based drilling fluid has a wide range of applications and a density of 0.9g / cm 3 ~2.2g / cm 3 It is adjustable between 60℃ and 170℃ and has good rheological properties, suspension stability and filtration loss control ability.

[0016] 3) The product of the present invention has good rheological properties, suspension properties, and filter vector control ability, with a dynamic plastic ratio range of 0.3-0.4, and a high temperature and high pressure filter vector FL (110°C) <3mL;

[0017] 4) The product cost of the present invention has good crack sealing ability and can effectively form a dense sealing layer for 1.0-3.0 mm cracks;

[0018] 5) The product cost of the present invention has a strong advantage, which is 15%-20% lower than that of conventional oil-based drilling fluid systems;

[0019] The strong plugging oil-based drilling fluid system of the present invention has good temperature resistance, rheological properties, plugging properties, good compatibility with conventional soil-containing oil-based drilling fluids, and can meet the technical requirements of long horizontal well drilling. DETAILED DESCRIPTION

[0020] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail.

[0021] Embodiment 1:

[0022] The purpose of the present invention is to provide a strong plugging type oil-based drilling fluid system suitable for fractured formations, using an integrated emulsifier, a liquid fluid loss reducer, an oil-based high-efficiency viscosity-enhancing and shear-enhancing agent, and a multi-stage fracture plugging agent to construct a high shear force, low viscosity, good rheological property, and strong plugging type oil-based drilling fluid system. The integrated emulsifier, liquid fluid loss reducer, oil-based high-efficiency viscosity-enhancing and shear-enhancing agent, and multi-stage fracture plugging agent in this embodiment are all existing products.

[0023] At room temperature, 80 parts of oil phase (diesel / white oil), 3 parts of SSC-M integrated emulsifier, 3 parts of alkalinity regulator, 20 parts of saturated calcium chloride brine, 3 parts of SSC-FL liquid fluid loss reducer, 1 part of SSC-MOD oil-based high-efficiency viscosity enhancer and shear enhancer, 1 part of multi-stage crack plugging agent, and 56 parts of weighting material were added in sequence to form a 1.4 g / cm 3 For the strong plugging oil-based drilling fluid, after adding each liquid material, it is necessary to stir at a variable speed for 15-20 minutes before adding another material, and the stirring speed is less than 6000rpm; after adding each solid material, it is necessary to stir at a variable speed for 25-30 minutes before adding another material, and the stirring speed is less than 8000rpm. After weighting with weighting materials, stir at a variable speed for 60-90 minutes (stirring speed 12000rpm).

[0024] The performance evaluation of the strong plugging oil-based drilling fluid system prepared in this example is shown in Table 1.

[0025] Table 1 Performance evaluation of strong plugging oil-based drilling fluid system

[0026]

[0027] The strong plugging oil-based drilling fluid system of the present invention has applicability to multiple oil-water ratios, and the applicable range is from oil / water = 70 / 30 to 85 / 15. The performance evaluation of different oil-water ratio intervals is shown in Table 2.

[0028] Table 2 Performance evaluation of oil-based drilling fluid system with multiple oil-water ratios

[0029]

[0030] The strong plugging oil-based drilling fluid system of the present invention has a strong plugging ability. The plugging performance of cracks in different size intervals is evaluated as shown in Table 3.

[0031] Table 3 Evaluation of plugging performance of strong plugging oil-based drilling fluid system

[0032] Temperature ℃ Seam width mm Pressure MPa Time min Loss 120 0.28 0.34 5 0 120 0.68 0.74 5 0 120 1.03 3.5 5 0 120 1.37 5.16 5 0 120 1.68 7.11 5 0 120 1.91 10.15 5 0 120 2.32 12.06 5 0 120 2.73 15.04 5 6.01 120 3.02 18.56 5 40.58

[0033] Embodiment 2:

[0034] The purpose of the present invention is to provide a strong plugging type oil-based drilling fluid system suitable for fractured formations, which adopts an integrated emulsifier, a liquid filtrate reducer, an oil-based high-efficiency viscosity-enhancing and shear-enhancing agent, and a multi-stage fracture plugging agent to construct a high shear force, low viscosity, good rheology, and strong plugging type oil-based drilling fluid system.

[0035] At room temperature, 80 parts of oil phase (diesel / white oil), 6 parts of SSC-M integrated emulsifier, 3 parts of alkalinity regulator, 20 parts of saturated calcium chloride brine, 3 parts of SSC-FL liquid fluid loss reducer, 1 part of SSC-MOD oil-based high-efficiency viscosity enhancer, 1 part of multi-stage crack plugging agent, 48 parts, 56 parts, 67 parts, and 80 parts of weighting material are added in sequence to form a density of 1.2 g / cm 3 , 1.4g / cm 3 , 1.6g / cm 3 , 2.0g / cm 3 For strong plugging oil-based drilling fluid, after adding each liquid material, it is necessary to stir at a variable speed for 15-20 minutes before adding another material, and the stirring speed should be less than 6000rpm; after adding each solid material, it is necessary to stir at a variable speed for 25-30 minutes before adding another material, and the stirring speed should be less than 8000rpm. After weighting with weighting materials, stir at a variable speed for 60-90 minutes (stirring speed 12000rpm).

[0036] The strong plugging oil-based drilling fluid system of the present invention has a multi-density range applicability, and the applicable range is from 0.9g / cm 3 -2.2g / cm 3Considering the technical requirements of long horizontal well drilling fluid, 1.2g / cm 3 , 1.4g / cm 3 , 1.6g / cm 3 , 2.0g / cm 3 The performance of the strong plugging oil-based drilling fluid was evaluated as shown in Table 4.

[0037] Table 4 Performance evaluation of soil-free drilling fluid system

[0038]

[0039] The strong plugging oil-based drilling fluid system of the present invention has strong adaptability and good adaptability with conventional soil-phase oil-based drilling fluid, can be mixed in multiple proportions, and the performance after mixing is basically stable. The performance of the strong plugging oil-based drilling fluid: conventional soil-phase drilling fluid system = 3:7\5:5\7:3 after mixing is evaluated as shown in Table 5.

[0040] Table 5 Multi-ratio mixing performance evaluation

[0041]

[0042] Comparative Example 1

[0043] JH-OBS oil-based drilling fluid system

[0044] The commonly used JH-OBS oil-based drilling fluid system is a high-soil phase oil-based drilling fluid system. Its system composition is composed of emulsifiers, asphalt-based fluid loss reducers, organic soil and other materials. This type of oil-based drilling fluid system has been maturely applied in many blocks. The comparison of the two systems is shown in Table 6.

[0045] Table 6 System comparison evaluation

[0046]

[0047] Comparative Example 2

[0048] HTHP-MOM oil-based drilling fluid system

[0049] The HTHP-MOM oil-based drilling fluid system is mainly used in deep shale gas development. The system is mainly composed of emulsifiers, fluid loss reducers, organic soils, shearing agents and other materials. The emulsifier addition ratio is relatively high (6-7%). The comparison of the two systems is shown in Table 7.

[0050] Table 7 System comparison evaluation

[0051]

[0052] The embodiments of the present invention are described above, but the present invention is not limited to the above-mentioned specific implementation modes. The above-mentioned specific implementation modes are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which are all within the protection of the present invention.

Claims

1. A strong plugging oil-based drilling fluid system suitable for fractured formations, characterized in that: It includes the following components, calculated by mass: 70-80 parts of base oil, 3-5 parts of integrated emulsifier, 1-3 parts of alkalinity regulator, 2-4 parts of liquid filtration reducer, 1.5-3 parts of oil-based high-efficiency viscosity-enhancing and shear-enhancing agent, 1.5-3.0 parts of multi-stage crack plugging agent, and 0-80 parts of weighting material.

2. The strong plugging type oil-based drilling fluid system suitable for fractured formations according to claim 1, characterized in that: The integrated emulsifier comprises the following components, calculated by mass fraction: 30% of sorbitan monooleate, 30% of oleic acid diethanolamide, and 40% of methyl erucate.

3. The strong plugging type oil-based drilling fluid system suitable for fractured formations according to claim 1, characterized in that: The liquid fluid loss reducer is SSC-FL liquid fluid loss reducer.

4. The strong plugging type oil-based drilling fluid system suitable for fractured formations according to claim 1, characterized in that: The oil-based high-efficiency viscosity-increasing and shear-improving agent is SSC-MOD oil-based high-efficiency viscosity-increasing and shear-improving agent.

5. The strong plugging type oil-based drilling fluid system suitable for fractured formations according to claim 1, characterized in that: The multi-stage crack plugging agent includes plant fiber plugging particles and nanometer plugging particles. For cracks within 0.5 mm, the mass ratio of the two is plant fiber plugging particles: nanometer plugging particles = 1:

2.

6. The strong plugging type oil-based drilling fluid system suitable for fractured formations according to claim 1, characterized in that: The multi-stage crack plugging agent includes plant fiber plugging particles and nanometer plugging particles. For cracks within 0.5 mm-1.5 mm, the mass ratio of the two is plant fiber plugging particles: nanometer plugging particles = 1:

1.

7. The strong plugging type oil-based drilling fluid system suitable for fractured formations according to claim 1, characterized in that: The multi-stage crack plugging agent includes plant fiber plugging particles and nanometer plugging particles. For cracks within 1.5 mm-3.0 mm, the mass ratio of the two is plant fiber plugging particles: nanometer plugging particles = 2:

1.

8. A method for preparing the strong plugging type oil-based drilling fluid system suitable for fractured formations as claimed in claim 1, comprising the following steps: At room temperature, in the slurry preparation cup, add the oil phase, integrated emulsifier, alkalinity regulator, saturated calcium chloride brine, liquid filtrate reducer, oil-based high-efficiency viscosity enhancer and shear enhancer, and weighting material in this order to form a strong plugging oil-based drilling fluid system. After adding each liquid phase material, it is necessary to stir at a variable speed for 15-20 minutes before adding another material, and the stirring speed shall not be less than 6000rpm; after adding each solid phase material, it is necessary to stir at a variable speed for 25-30 minutes before adding another material, and the stirring speed shall not be less than 8000rpm. After weighting with the weighting material, stir at a variable speed for 60-90 minutes, and the stirring speed shall not be less than 12000rpm.

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