A method for reducing friction and torque of water-based drilling fluid in extended reach well or long horizontal well

Abstract

The application provides a water-based drilling fluid friction reduction and torque reduction method, and belongs to the technical field of drilling fluids for oil and gas field exploration and development. The application first uses thick slurry well washing to fully remove the rock debris bed and to reduce the negative influence of the rock debris bed on the friction torque of the drill string as much as possible; then, the well slurry containing a first liquid lubricant is pumped in, so that the liquid lubricant forms a solid lubricating film on the well wall or the well wall mud cake and the surface of the drill string; then, the well slurry containing a solid lubricant is pumped in, and the solid lubricant plays a role of a ball bearing on the basis of a high-toughness lubricating film of a sufficient amount of lubricant in a local part, so as to further reduce the friction torque; finally, the second liquid lubricant is supplemented in the whole well slurry to consolidate the lubricating effect and improve the long-term effect. The application fully utilizes the film lubrication mechanism of the liquid lubricant and the sheet effect and ball effect of the solid lubricant, improves the "instant effect" of the lubricant, achieves the purpose of reducing friction and torque, and helps the horizontal displacement or the limit extension of the horizontal section of the large displacement well or the long horizontal well.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid technology for oil and gas field exploration and development, and in particular to a method for reducing friction and torque in water-based drilling fluids. Background Technology

[0002] With the accelerated pace of oil and gas field exploration and development, the oil and gas extraction efficiency of ordinary vertical wells and directional wells can no longer meet the demands for increased reserves and production. Operating wells are gradually shifting towards extended reach wells or long horizontal wells, bringing with them new challenges. Excessive drill string friction torque is the most critical factor affecting the horizontal displacement or horizontal section limits of extended reach wells or long horizontal wells. Therefore, the industry commonly uses high-lubricity drilling fluids to improve drill string friction torque. Oil-based drilling fluids are favored by the market due to their naturally high lubricity, but their high cost and environmental impact have constrained their development. Water-based drilling fluids, on the other hand, can achieve lubrication performance comparable to oil-based drilling fluids by adding high-efficiency lubricants, thereby reducing the friction coefficient between the drill string and the wellbore or mud cake and improving friction torque. Numerous cases of preparation and research on lubricants for water-based drilling fluids exist in the industry, but they are mostly focused on laboratory synthesis and performance evaluation, and simple, crude field applications. The methods of using lubricants and field construction techniques have not been elaborated, and there have been no precedents for research on these aspects. Summary of the Invention

[0003] The purpose of this invention is to provide a method for reducing friction and torque in water-based drilling fluids, which can make full use of the action mechanism of commonly used liquid or solid lubricants in oil and gas field drilling to improve the effect of lubricants and avoid the problems of material loss and poor effect caused by blindly adding slurry to the whole well.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for reducing friction and torque in water-based drilling fluids, comprising the following steps:

[0006] Pumping thick slurry into the bottom of the well to flush the well;

[0007] After the well washing is completed, pump well slurry containing the first liquid lubricant into the bottom of the well;

[0008] After pumping is completed, well slurry containing solid lubricant is pumped to the bottom of the well. After pumping is completed, the drill string continues to drill, and a second liquid lubricant is added to the entire well slurry during the drilling process.

[0009] Preferably, the thick slurry comprises well slurry and a viscosifier; the funnel viscosity of the thick slurry is 90–110 s; and the pumping rate of the thick slurry is 10–30 m³ / s. 3 .

[0010] Preferably, the dosage of the second liquid lubricant is 5–20 kg / m³. 3.

[0011] Preferably, the pumping rate of the well slurry containing the first liquid lubricant is 10–40 m³. 3 The dosage of the first liquid lubricant is 50-100 kg / m³. 3 .

[0012] Preferably, the pumping rate of the well slurry containing solid lubricant is 10–40 m³. 3 The amount of the solid lubricant used is 50-100 kg / m³. 3 .

[0013] Preferably, the first liquid lubricant and the second liquid lubricant are a mixture of polyalkylene glycol, boron-based nanoemulsion and castor oil.

[0014] Preferably, the first or second liquid lubricant, based on a total mass of 100, has a mass ratio of polyalkylene glycol, boron-based nanoemulsion, and castor oil of (30-50): (10-30): (20-50) in both liquid lubricants.

[0015] Preferably, the solid lubricant is a mixture of nano-boron nitride, graphene, and plastic microspheres.

[0016] Preferably, the solid lubricant, based on a total mass of 100, has a mass ratio of nano-boron nitride, multilayer graphene, and plastic microspheres of (30-60):(5-15):(35-65).

[0017] Preferably, the boron nitride nanoparticles have a particle size of 100–500 nm, the graphene has 5–10 layers with a layer thickness of 1–5 nm, and the plastic microspheres have a particle size of 10–200 μm.

[0018] This invention provides a method for reducing friction and torque in water-based drilling fluids, comprising the following steps: pumping a thick slurry into the bottom of the well for washing; after washing, pumping a slurry containing a first liquid lubricant into the bottom of the well; after pumping is complete, continuing to pump a slurry containing a solid lubricant into the bottom of the well; after pumping is complete, the drill string continues drilling, and during drilling, a second liquid lubricant is added to the entire slurry. This invention first uses a thick slurry to wash the well, thoroughly removing the cuttings bed and minimizing its negative impact on drill string friction and torque; then, it pumps in a slurry containing the first liquid lubricant so that the liquid lubricant forms a robust lubricating film on the wellbore or wellbore mud cake and drill string surface; subsequently, it pumps in a slurry containing a solid lubricant, which, based on the locally sufficient high-toughness lubricating film, acts as a ball bearing, further reducing friction and torque; finally, a second liquid lubricant is added to the entire slurry to consolidate the lubrication effect and improve its long-term effectiveness. This invention fully utilizes the thin-film lubrication mechanism of liquid lubricants and the sheet effect and ball effect of solid lubricants to improve the immediate effect of lubricants and achieve the purpose of reducing friction and torque.

[0019] The friction reduction and torque reduction method of the present invention can maintain the long-term lubrication performance of drilling fluid, ensure low friction and low torque, and help wells with large reach or long horizontal wells to achieve horizontal displacement or limit extension of horizontal section.

[0020] Furthermore, the multi-level matching of solid lubricant particle size in this invention can effectively reduce internal friction in the lubricant and avoid internal consumption.

[0021] The friction reduction and torque reduction method of the present invention is particularly suitable for large-displacement wells (referring to wells with a water-to-vertical ratio greater than 2) and long horizontal wells (referring to wells with a horizontal displacement distance greater than 2000m). Detailed Implementation

[0022] This invention provides a method for reducing friction and torque in water-based drilling fluids, comprising the following steps:

[0023] Pumping thick slurry into the bottom of the well to flush the well;

[0024] After the well washing is completed, pump well slurry containing the first liquid lubricant into the bottom of the well;

[0025] After pumping is completed, well slurry containing solid lubricant is pumped to the bottom of the well. After pumping is completed, the drill string continues to drill, and a second liquid lubricant is added to the entire well slurry during the drilling process.

[0026] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0027] This invention preferably involves pumping a thick slurry into the bottom of the well to wash the well when the drill string friction torque continuously increases and affects normal drilling. In this invention, the thick slurry preferably includes well mud and a viscosifier; the funnel viscosity of the thick slurry is preferably 90–110 s, more preferably 95–105 s. This invention does not have special requirements on the type of viscosifier; any viscosifier well known in the art is acceptable. This invention does not impose special limitations on the amount of viscosifier used, as long as the funnel viscosity of the thick slurry is 90–110 s. In this invention, the method for preparing the thick slurry preferably includes: introducing well mud into a spare mud tank, and then adding a viscosifier using a shear pump for shearing and stirring to obtain the thick slurry. In this invention, the shearing and stirring time is preferably 30–60 minutes.

[0028] In this invention, the pumping rate of the slurry is preferably 10-30 m³. 3 Those skilled in the art can flexibly adjust the above range according to actual conditions. The present invention preferably uses staged pumping of the thick slurry, which is beneficial to improving well washing efficiency. After the thick slurry is pumped to the bottom of the well, the sand carried by the thick plug gradually increases the amount of sand returned to the vibrating screen. As the thick plug is discharged, the amount of sand returned to the vibrating screen decreases until the screen surface is clean. The present invention utilizes the thick slurry to thoroughly remove the cuttings bed, minimizing the negative impact of the cuttings bed on the drill string friction torque.

[0029] After the well is cleaned, the present invention pumps well slurry containing a first liquid lubricant into the bottom of the well.

[0030] In this invention, well slurry is preferably added to a tank that has been prepared with thickened slurry, and then a first liquid lubricant is added via a shear pump, followed by shearing and stirring to obtain well slurry containing the first liquid lubricant. In this invention, the shearing and stirring time is preferably 30–60 minutes. This invention does not have special requirements regarding the type of the first liquid lubricant; any liquid lubricant well-known in the art is acceptable. In this invention, the first liquid lubricant is preferably a mixture of polyalkylene glycol, boron-based nanoemulsion, and castor oil; based on a total mass of 100, the mass ratio of the polyalkylene glycol, boron-based nanoemulsion, and castor oil is preferably (30–50):(10–30):(20–50), more preferably 30:20:50, 40:15:45, or 50:30:20.

[0031] In this invention, the pumping rate of the well slurry containing the first liquid lubricant is preferably 10-40 m³. 3 More preferably 15–35m 3 More preferably 20-30m 3 The preferred dosage of the first liquid lubricant is 50–100 kg / m³. 3 More preferably 60–90 kg / m 3 A further preferred value is 70–80 kg / m³. 3 .

[0032] After the well slurry containing the first liquid lubricant is pumped in, a solid lubricating film is formed on the well wall or well wall mud cake and drill string surface, which is beneficial to reduce friction and torque.

[0033] After the well slurry containing the first liquid lubricant has been pumped out, the present invention preferably stops the pump and waits, and then continues to pump well slurry containing solid lubricant to the bottom of the well.

[0034] During the pump shutdown and waiting period, the present invention continues to introduce new well slurry into the tank, and then adds solid lubricant using a shear pump, performing shearing and stirring to obtain well slurry containing solid lubricant. In the present invention, the shearing and stirring time is preferably 30-60 minutes. The present invention does not impose a special limitation on the pump shutdown and waiting time; subsequent steps can be carried out after the mud containing solid lubricant is prepared. The present invention does not have special requirements on the type of solid lubricant; any solid lubricant well known in the art is acceptable. In the present invention, the solid lubricant is preferably a mixture of nano-boron nitride, graphene, and plastic microspheres; the mass ratio of nano-boron nitride, multilayer graphene, and plastic microspheres in the solid lubricant, based on a total mass of 100, is preferably (30-60):(5-15):(35-65), more preferably 30:10:60, 35:15:50, or 60:5:35.

[0035] In this invention, the particle size of the nano-boron nitride is preferably 100–500 nm, more preferably 200–400 nm; the number of graphene layers is preferably 5–10, specifically 5, 8, or 10 layers in the embodiments of this invention; the layer thickness of the graphene is preferably 1–5 nm, more preferably 2–4 nm; and the particle size of the plastic microspheres is preferably 10–200 μm, more preferably 50–150 μm. The multi-level matching of particle sizes in the solid lubricant of this invention can effectively reduce internal friction in the lubricant and avoid internal consumption.

[0036] In this invention, the pumping rate of the well slurry containing solid lubricant is preferably 10-40 m³. 3 More preferably 15–35m 3 More preferably 20-30m 3 The preferred dosage of the solid lubricant is 50–100 kg / m³. 3 More preferably 60–90 kg / m 3 A further preferred value is 70–80 kg / m³. 3 The present invention, after pumping in well slurry containing solid lubricant, acts as a ball bearing on the basis of the lubricating film, further reducing frictional torque.

[0037] After the well slurry containing solid lubricant is pumped out, the movable drill string of the present invention continues to drill, and during the drilling process, the entire well slurry is replenished with a second liquid lubricant.

[0038] In this invention, the second liquid lubricant is preferably a mixture of polyalkylene glycol, boron-based nanoemulsion, and castor oil. The mass ratio of the polyalkylene glycol, boron-based nanoemulsion, and castor oil is preferably (30-50):(10-30):(20-50), more preferably (40-45):(10-20):(30-50). In specific embodiments of this invention, the ratio is 40:10:50, 50:20:30, or 45:10:45.

[0039] In this invention, the preferred dosage of the second liquid lubricant is 5–20 kg / m³. 3 More preferably 8–17 kg / m 3 A further preferred value is 10–15 kg / m³. 3 This invention provides a second liquid lubricant to the entire well slurry to enhance lubrication and improve its long-term effectiveness.

[0040] The following detailed description of the water-based drilling fluid friction reduction and torque reduction method provided by the present invention, in conjunction with embodiments and comparative examples, should not be construed as limiting the scope of protection of the present invention.

[0041] Comparative Example 1

[0042] A certain offshore oil well has an 8-1 / 2" section with an inclination angle of 85°, a vertical depth of 1500m, a horizontal displacement of 4000m, and a water-to-vertical ratio of 2.67, classifying it as a typical extended reach well. The drilling fluid used is water-based with a funnel viscosity of 55s. During drilling into the open hole section, the torque fluctuated frequently, ranging from 27 to 35 kN·m. After adding 4000 kg of on-site liquid lubricant to the entire well, the torque decreased slightly to 25 to 32 kN·m, but the fluctuation remained significant. Furthermore, the torque returned to normal after drilling another 500m, indicating poor long-term torque reduction effectiveness.

[0043] Comparative Example 2

[0044] A certain offshore oil well has a designed depth of 3786m, a vertical depth of 1502m, a horizontal displacement of 3172m, and a water-to-vertical ratio of 2.11, classifying it as a typical extended reach well. Significant torque fluctuations occurred at a depth of 3019m in the 12-1 / 4" open hole section, with the torque increasing from 22 kN·m to 29 kN·m and showing a continuing upward trend. At this point, the well inclination angle was 73.4°, the vertical depth was 1323m, and the horizontal displacement was 2438m. The drilling fluid used was water-based, with a funnel viscosity of 49s. After adding 3000 kg of on-site solid lubricant using whole-well slurry, the torque decreased from 29 kN·m to 25 kN·m, but after drilling another 200m, it gradually increased again to 28 kN·m, still showing an upward trend.

[0045] Comparative Example 3

[0046] A typical long horizontal well has an 8-1 / 2" section with a 90° inclination angle, a measured depth of 5724m, and a horizontal section length of 2235m. The drilling fluid used is water-based with a funnel viscosity of 70s. At a measured depth of 5023m, the drilling friction during both lifting and lowering was abnormally high, increasing from 15t to 35t during lifting and from 10t to 25t during lowering, severely impacting normal operations. After adding 1500kg of on-site liquid lubricant and 1000kg of on-site solid lubricant to the whole-well slurry, the lifting friction decreased from 35t to 26t, and the lowering friction decreased from 25t to 18t, somewhat alleviating the high friction problem. However, after drilling 250m further, a short lift revealed that the lifting friction increased to 37t, and the lowering friction increased to 28t, indicating that directly adding lubricant to the whole-well slurry was no longer effective in reducing friction.

[0047] Example 1

[0048] To address the issue of unsatisfactory results when directly adding liquid lubricant to the entire well slurry in Comparative Example 1, the following steps are proposed and adopted to reduce and stabilize torque:

[0049] (1) Introduce well mud into the standby mud tank, with an effective volume of 30m³. 3 210 kg of on-site thickener was added to the slurry funnel by a shear pump to increase the viscosity of the slurry to 90 s. After shearing and stirring for 60 min, the slurry was pumped to the bottom of the well. The sand was carried by the thick plug, and the sand returned by the vibrating screen gradually increased. As the thick plug was discharged, the sand returned by the vibrating screen decreased from a lot to a little until the screen surface was clean.

[0050] (2) Continue to introduce well slurry into the tank, with an effective volume of 20m³. 3 1600 kg of liquid lubricant (in which the mass ratio of polyalkylene glycol, boron-based nanoemulsion, and castor oil is 30:20:50) was added to the well using a shear pump. After shearing and stirring for 30 minutes, the lubricant was pumped to the bottom of the well. After pumping was completed, the pump was stopped and the well was left to stand still.

[0051] (3) Continue to pour 20m into the tank. 3Well slurry was prepared by adding 1000 kg of solid lubricant (in which the mass ratio of nano-boron nitride, graphene, and plastic microspheres was 30:10:60, the nano-boron nitride had a particle size of 300 nm, the graphene had 10 layers with a layer thickness of 3 nm, and the plastic microspheres had a particle size of 50 μm) to the slurry using a shear pump. After shearing and stirring for 30 minutes, the slurry was pumped to the bottom of the well.

[0052] (4) After 10 minutes, start the pump to circulate and open the top drive to move the drill string up and down;

[0053] (5) After 15 minutes, drilling continued and the torque was shown to drop to 25 kN·m, with the fluctuation range not exceeding 2 kN·m;

[0054] (6) After drilling for another 100m, add 2500kg of liquid lubricant (in which the mass ratio of polyalkylene glycol, boron-based nanoemulsion and castor oil is 40:10:50) to the circulation tank through a shear pump to consolidate the lubrication effect of the drilling fluid and improve the long-term lubrication effect.

[0055] (9) Until the well section 8-1 / 2" was completed, the torque was maintained at 25±2kN·m, which significantly reduced and stabilized the torque.

[0056] Example 2

[0057] To address the issue of unsatisfactory results when directly adding solid lubricant to the entire well slurry in Comparative Example 2, the following steps are proposed and adopted to reduce and stabilize torque:

[0058] (1) Introduce well mud into the standby mud tank, with an effective volume of 35m³. 3 By adding 300 kg of on-site viscosifier to the slurry funnel of the diaphragm using a shear pump, the viscosity of the slurry funnel was increased to 100 s. After shearing and stirring for 60 minutes, the slurry was pumped to the bottom of the well in three stages. Through multi-stage thick plugging and rock carrying, the rock cuttings at the bottom of the well were cleaned up, eliminating the negative impact of the rock cuttings bed.

[0059] (2) Continue to introduce well slurry into the tank, with an effective volume of 30m³. 3 2100 kg of liquid lubricant (in a mass ratio of polyalkylene glycol, boron-based nanoemulsion, and castor oil of 40:15:45) was added to the well using a shear pump. After shearing and stirring for 30 minutes, the lubricant was pumped to the bottom of the well. After pumping was completed, the pump was stopped and the well was left to stand still to ensure that the lubricant formed a solid lubricating film on the well wall and drill string surface, and participated in the formation of mud cake to reduce the viscosity coefficient of the mud cake and reduce internal friction.

[0060] (3) Continue to pour 30m into the tank 3The well slurry was mixed with 2400 kg of solid lubricant (the mass ratio of nano-boron nitride, graphene, and plastic microspheres was 60:5:35, the nano-boron nitride had a particle size of 500 nm, the graphene had 8 layers with a layer thickness of 4 nm, and the plastic microspheres had a particle size of 100 μm) and then pumped to the bottom of the well.

[0061] (4) After pumping is completed, circulate and open the top drive to move the drill bit up and down. Add 3000 kg of liquid lubricant to the circulation tank through the shear pump (the mass ratio of polyalkylene glycol, boron-based nanoemulsion and castor oil is 50:20:30).

[0062] (5) Drilling continued, and the torque was shown to drop to 20 kN·m with a fluctuation range of no more than 3 kN·m;

[0063] (6) Until the well section of 12-1 / 4" was completed, the torque was maintained at 20±3kN·m, which significantly reduced and stabilized the torque.

[0064] Example 3

[0065] To address the issue of poor friction reduction effect when directly using a mixture of solid and liquid lubricants in the well slurry in Comparative Example 3, the following steps are proposed and adopted to reduce and stabilize friction:

[0066] (1) Introduce well mud into the standby mud tank, with an effective volume of 20m³. 3 By adding 100 kg of on-site viscosifier to the slurry funnel of the well using a shear pump, the viscosity of the slurry funnel was increased to 110 s. After shearing and stirring for 60 minutes, the slurry was pumped to the bottom of the well in sections.

[0067] (2) After the screen surface is clean, continue to pour well slurry into the tank, with an effective volume of 20m³. 3 1500 kg of liquid lubricant (in which the mass ratio of polyalkylene glycol, boron-based nanoemulsion, and castor oil is 50:30:20) is added to the well using a shear pump. After shearing and stirring for 30 minutes, the lubricant is pumped to the bottom of the well in one go. After pumping is completed, the pump is stopped and the well is left to stand still.

[0068] (3) Continue to pour 30m into the tank. 3 Well slurry was prepared by adding 1500 kg of solid lubricant (in which the mass ratio of nano-boron nitride, graphene, and plastic microspheres was 35:15:50, the nano-boron nitride had a particle size of 200 nm, the graphene had 5 layers with a layer thickness of 2 nm, and the plastic microspheres had a particle size of 150 μm) to the slurry using a shear pump. After stirring for 30 minutes, the slurry was pumped to the bottom of the well.

[0069] (4) After pumping is completed, add 2000 kg of liquid lubricant to the circulation tank by shear pump (the mass ratio of polyalkylene glycol, boron-based nanoemulsion and castor oil is 45:10:45).

[0070] (5) Then the top drive was opened to move the drill string up and down. It was shown that the friction resistance dropped to 13t when it was lifted and to 8t when it was lowered, and the fluctuation range did not exceed 2t.

[0071] (6) When the well section 8-1 / 2" was completed, the friction during the lifting and lowering was always maintained at 8-15t, which significantly stabilized and reduced the friction.

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for reducing friction and torque in water-based drilling fluid, characterized in that, Includes the following steps: Pumping thick slurry into the bottom of the well to flush the well; After the well washing is completed, pump well slurry containing the first liquid lubricant into the bottom of the well; After pumping is completed, well slurry containing solid lubricant is pumped to the bottom of the well. After pumping is completed, the moving drill string continues to drill. During the drilling process, the entire well slurry is replenished with a second liquid lubricant. The pumping rate of the well slurry containing the first liquid lubricant is 10-40 m³. 3 The dosage of the first liquid lubricant is 50-100 kg / m³. 3 ; The pumping rate of the well slurry containing solid lubricant is 10–40 m³. 3 The amount of the solid lubricant used is 50-100 kg / m³. 3 .

2. The method for reducing friction and torque of water-based drilling fluid according to claim 1, characterized in that, The thick slurry comprises well slurry and a viscosifier; the funnel viscosity of the thick slurry is 90–110 s; the pumping rate of the thick slurry is 10–30 m³ / s. 3 .

3. The method for reducing friction and torque of water-based drilling fluid according to claim 1 or 2, characterized in that, The dosage of the second liquid lubricant is 5–20 kg / m³. 3 .

4. The method for reducing friction and torque of water-based drilling fluid according to claim 1, characterized in that, The first and second liquid lubricants are mixtures of polyalkylene glycol, boron-based nanoemulsion and castor oil.

5. The method for reducing friction and torque of water-based drilling fluid according to claim 1, characterized in that, The first or second liquid lubricant is based on a total mass of 100, and the mass ratio of polyalkylene glycol, boron-based nanoemulsion and castor oil in the first and second liquid lubricants is independently (30-50):(10-30):(20-50).

6. The method for reducing friction and torque of water-based drilling fluid according to claim 1, characterized in that, The solid lubricant is a mixture of nano-boron nitride, graphene, and plastic microspheres.

7. The method for reducing friction and torque of water-based drilling fluid according to claim 6, characterized in that, The solid lubricant, with a total mass of 100, has a mass ratio of nano-boron nitride, multilayer graphene, and plastic microspheres of (30-60):(5-15):(35-65).

8. The method for reducing friction and torque of water-based drilling fluid according to claim 7, characterized in that, The boron nitride nanoparticles have a particle size of 100–500 nm, the graphene has 5–10 layers with a layer thickness of 1–5 nm, and the plastic microspheres have a particle size of 10–200 μm.