CN117189002A - Low-pressure easy-to-leak stratum drilling parameter optimization method - Google Patents
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Abstract
The invention relates to a low-pressure easy-leakage stratum drilling parameter optimization method, which comprises the steps of firstly predicting stratum leakage pressure and collapse pressure; then designing drilling fluid parameters, wherein the density of the drilling fluid is designed based on the equivalent density of the smaller one of the drilling fluids; the circulation displacement, the hydraulic shear force of the drilling fluid and the plastic viscosity are designed so that the circulation friction resistance during drilling does not exceed the difference value between the leakage pressure and the collapse pressure; calculating critical annular return speed when a rock debris bed is not formed, and if the currently designed circulating return speed is smaller than the critical annular return speed, re-optimizing the circulating displacement, drilling fluid tangential force and plastic viscosity until the optimized circulating displacement meets the condition that the circulating return speed is smaller than the critical annular return speed; finishing the design of the performance parameters of the drilling fluid of the whole well section; and finally, optimizing the drilling or casing running speed according to the performance parameters of the drilling fluid, and controlling the exciting pressure within the range of the difference value between the leakage pressure and the collapse pressure to finish the optimization of the drilling parameters. The drilling construction efficiency is improved, and the cost is reduced.
Description
Technical Field
The invention relates to a method for optimizing drilling parameters of a low-pressure easy-to-leak stratum, and belongs to the technical field of drilling optimization design.
Background
In the drilling engineering, a stratum with low leakage pressure, which is developed when encountering cracks, has better permeability, poor bedding and cementing and the like, is often drilled, and drilling fluid leakage occurs because the wellbore pressure is larger than the stratum leakage pressure. The lost circulation not only consumes drilling time and loses a large amount of drilling fluid, but also can cause complex accidents such as blowout, well collapse, drill sticking and the like due to improper treatment, and is one of the most common drilling engineering accidents. Numerous scholars at home and abroad develop researches around well leakage mechanism, leakage blocking technology and the like, and form a series of well leakage blocking materials and systems with great effects, and the pertinence of well leakage control and the leakage blocking efficiency are obviously improved. Based on the concepts of 'mainly preventing' and 'earlier bearing', the well drilling engineering parameters are optimized, the well bore pressure is accurately controlled to be smaller than the leakage pressure, and the method is a key measure for improving the well drilling construction efficiency and reducing the cost.
Wellbore pressure influences many factors, drilling fluid density directly influences hydrostatic column pressure, mechanical drilling speed, circulation displacement, drilling fluid performance and the like influence annular circulation friction, while tripping (casing) speed and drilling fluid performance influence fluctuation pressure (the fluctuation pressure can be regarded as the sum of exciting pressure and swabbing pressure, and the fluctuation pressure is brought by the exciting pressure under the condition of tripping or tripping the casing). Therefore, in order to accurately control the pressure of the well bore, a well bore pressure prediction method is required to be established, the influence rule of each factor on the pressure of the well bore is respectively analyzed on the basis, the requirements of well bore cleaning and drilling speed are integrated, and drilling engineering parameters are optimized.
Disclosure of Invention
The invention aims to provide a method for optimizing drilling parameters of a low-pressure easy-leakage stratum, which is used for realizing accurate prediction and optimization of drilling engineering parameters under the stratum with low leakage pressure.
In order to achieve the above object, the present invention provides a method comprising:
the technical scheme of the low-pressure easy-leakage stratum drilling parameter optimization method provided by the invention comprises the following steps of:
1) Predicting formation leak-off pressure and collapse pressure;
2) Designing drilling fluid parameters, wherein the density of the drilling fluid is designed based on the equivalent density of the collapse pressure;
the circulation displacement, the hydraulic shear force of the drilling fluid and the plastic viscosity are designed so that the circulation friction resistance during drilling does not exceed the difference value between the leakage pressure and the collapse pressure;
3) Calculating critical annular return speed when a rock debris bed is not formed, if the currently designed circulating return speed is smaller than the critical annular return speed, returning to the step 2) to optimize the circulating displacement, the hydraulic cutting force and the plastic viscosity of the drilling fluid again until the optimized circulating displacement meets the condition that the circulating return speed is smaller than the critical annular return speed;
4) Repeating the steps 2) and 3), designing drilling fluid performance parameters of different horizons, different well depths and different well inclinations, and completing the design of the drilling fluid performance parameters of the whole well section;
5) And optimizing the drilling parameter by optimizing the drilling or casing running speed according to the drilling fluid performance parameter and controlling the exciting pressure within the range of the difference value between the leakage pressure and the collapse pressure.
Studies have shown that wellbore pressure in drilling engineering consists of hydrostatic column pressure, circulating friction and fluctuating pressure. The invention takes stratum leakage pressure, borehole cleaning and the like as main constraints, respectively establishes a circulating friction resistance and fluctuation pressure prediction model on the basis of clear borehole pressure composition, and establishes a low-pressure easy-leakage stratum drilling parameter system optimization design method aiming at working conditions such as normal drilling, running and casing running.
Further, in step 1), the leakage pressure is predicted by establishing a transverse distribution profile of a main leakage horizon of the target area through interpolation by statistically analyzing drilling data; alternatively, predictions are made by fitting a model of the relationship of leak rate, leak pressure differential, and fracture porosity with the aid of logging data.
Further, in step 1), the collapse pressure is predicted based on logging data using a mole-coulomb criterion to establish a collapse pressure profile.
Further, in the step 2), the circulating friction during drilling is composed of circulating pressure loss of the drilling fluid in the whole annulus inner laminar flow section and pressure loss generated by rock debris solid phase particles in the whole annulus inner laminar flow section.
Further, the circulating pressure consumption p of the drilling fluid al1 Calculated by the following formula:
wherein: l is the annular section length for calculating the pressure consumption; q is the cyclic displacement; d (D) 0 Is the diameter of the borehole; d (D) i Is the outer diameter of the drill rod. Mu (mu) p 、τ 0 The plastic viscosity and the dynamic shear force of the drilling fluid are respectively.
Further, the pressure loss p generated by the rock debris solid phase particles al2 Calculated by the following formula:
p al2 ＝(ρ s -ρ)gL·C a
wherein: ρ s ρ is the density of the cuttings and drilling fluid, respectively; g is gravity acceleration; l is annular section for calculating pressure consumptionA length; c (C) a Is the annulus cuttings concentration.
Further, the annular cuttings concentration Ca is calculated by the following formula:
wherein R is the rate of penetration; k' is a speed correction coefficient; v (V) f The annulus return speed of the drilling fluid is set; d (D) b Is the diameter of the drill bit; d (D) 0 Is the diameter of the borehole; d (D) i Is the outer diameter of the drill rod; d, d s Is the diameter of the rock debris.
Further, in step 3), the critical annular return velocity Vc is calculated by:
wherein D is s Is the equivalent diameter of the rock debris particles; k is the consistency coefficient; θ is the well tilt angle; ρ s Is the rock debris density; ρ m Is the density of drilling fluid; mu (mu) e Is the effective viscosity of the drilling fluid.
Further, the effective viscosity μe of the drilling fluid is calculated as follows:
wherein K is a consistency coefficient; n is a fluidity index; d (D) o 、D i The diameter of the well bore and the outer diameter of the drill rod are respectively; v (V) a Is the return speed of the annular drilling fluid.
Further, in the step 3), if the optimized circulating speed is not smaller than the critical annular speed, the mechanical drilling speed is controlled by increasing the rotating speed of the drill rod, and the rock debris bed is damaged and cleared.
Drawings
FIG. 1 is a flow chart of a method for optimizing drilling parameters of a low pressure leaky stratum according to the invention;
FIG. 2 is the cyclic friction of the example JPH-4XY well at different cyclic displacements;
FIG. 3 is a graph showing the pressure increase of the Liujia ditch group of the JPH-4XY well at different rates of penetration in the example;
FIG. 4 is an illustration of activation pressure of a JPH-4XY well at different drilling fluid properties and rates of penetration in an example;
FIG. 5 is an illustration of activation pressures for a JPH-4XY well at different drilling fluid properties and casing running rates in an example.
Detailed Description
The present invention will be further described in detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent.
1. A method of wellbore pressure prediction.
(1) And (5) a circulating friction calculation model.
During the drilling process, the pressure of the bottom hole dynamic liquid column is changed if the circulation displacement or the drilling fluid density is changed. The circulation displacement changes change the annular internal circulation friction of the 'well bore-drill rod', and influences the cleaning degree of rock fragments in the well, thereby influencing the density of drilling fluid in the well; the density of drilling fluid in the well is greatly influenced by the mechanical drilling speed besides the influence of the circulating displacement. Thus, the annulus circulation friction comprises two parts:
1) Pressure loss p of drilling fluid circulation al1 ：
Wherein: l is the annular section length for calculating the pressure consumption, and the unit is m; q is cyclic displacement, unit is m 3 /s；D 0 Is the diameter of the borehole, in m; d (D) i The drill rod outer diameter is given in m. Mu (mu) p 、τ 0 The units of the plastic viscosity and the dynamic shear force of the drilling fluid are Pa.s and Pa respectively.
2) Pressure loss p generated by rock debris solid phase particles al2 ：
The sliding speed of the rock debris adopts a Moore formula, and the annular rock debris concentration calculation formula is as follows:
p al2 ＝(ρ s -ρ)gL·C a (3)
wherein R is the mechanical drilling speed, and the unit is m/h; k' is a speed correction coefficient; v (V) f The unit is m/s for the annulus return speed of the drilling fluid; ρ s ρ is the density of the cuttings and drilling fluid, respectively, in g/cm 3 ；D b The diameter of the drill bit is cm; d (D) 0 The diameter of the well bore is given in cm; d (D) i The unit is cm and the outside diameter of the drill rod is the outside diameter of the drill rod; d, d s The diameter of rock scraps is in cm; g is gravity acceleration, 980g/cm 3 。
3) According to the difference of the inner diameter and the outer diameter of the annulus, the circulation friction of the drilling fluid in the whole annulus inner laminar flow section annulus is as follows:
wherein M is i The total annular section number divided according to different inner diameters and outer diameters; i is a sequence of segments divided from bottom hole to top hole; d (D) 0i Refers to the diameter of the well bore corresponding to the ith annular space, and the unit is cm; d (D) ii The outside diameter of the drill rod corresponding to the ith annular space is cm; l (L) i Refers to the length of the ith annular space section, and the unit is m.
(2) And a fluctuating pressure calculation model.
During operations such as tripping, casing running, well dredging and the like, the well drilling fluid can flow due to the pipe column displacement, so that additional pressure is generated. Because the tripping speed is not uniform, the value of the additional pressure can change in the running process of the pipe column, and the stratum is easy to leak due to the overlarge exciting pressure.
1) Wave pressure model during tripping:
the one-way valve is arranged at the lower part of the drill rod or the casing, no matter whether the pump works or not, the drilling fluid in the well bore can not flow into the pipe when the pump starts to drill or runs the casing, namely, the drilling fluid belongs to a plugging pipe. As the drill string descends, the well drilling fluid movement is subject to the displacement force of the bottom surface of the drill string and the adhesion force of the drill string surface to the drilling fluid. By utilizing the narrow groove flow principle of Burkhardt and combining with the actual condition of drilling under the well, a drilling fluid flow rate equation when a pump is closed by a plugging pipe is provided:
in the formula, v p For average running speed of casing or single drill rod, D i For the outside diameter of the drill rod or casing, D 0 Is the inside diameter of the borehole.
2) Calculation of wave pressure during well dredging:
during well dredging, the mud pump works, and drilling fluid circulates in the well. The speed of the drilling fluid returning to the annulus is jointly formed by the flow rate caused by the displacement flow of the bottom area of the drill string, the flow rate caused by the adhesion of the drill string and the flow rate caused by the pump circulation:
in the formula, v p For average running speed of casing or single drill rod, D i For the outside diameter of the drill rod or casing, D ii Is the inner diameter of the drill rod or the casing, D 0 Is the inside diameter of the borehole.
The fluctuating pressure prediction model is:
2. a method for evaluating well cleaning.
And calculating a critical flow rate by using a critical flow rate prediction model, converting the critical flow rate into a corresponding critical displacement, and comparing the designed displacement with the critical displacement. If the design displacement is larger than the critical displacement, the rock debris bed cannot be formed in the well, and the design meets the cleaning requirement of the well; if the design displacement is smaller than the critical displacement, a rock debris bed is generated in the shaft, and the thickness of the rock debris bed is calculated by using a rock debris migration theoretical model. If the thickness of the rock debris bed can not meet the well cleaning requirement, the drilling parameters are optimized and adjusted. The thickness and the minimum rock carrying displacement of the rock debris bed:
T CB ＝0.015D o (μ e +6.15μ e 0.5 )(1+0.587ε)(V c -V a ) (8)
wherein: t (T) CB The thickness of the rock debris bed (if negative, no rock debris bed is considered to be formed) is expressed in mm; d (D) o 、D i The diameter of the well bore and the outer diameter of the drill rod are respectively in mm; d (D) s The equivalent diameter of rock debris particles is in mm; v (V) a The unit is m/s for the return speed of the annular drilling fluid; v (V) c The critical annular return speed of the rock debris bed is not formed, and the unit is m/s; n is a fluidity index; k is the consistency coefficient, the unit is Pa.s n The method comprises the steps of carrying out a first treatment on the surface of the θ is the well inclination angle in rad; epsilon is the eccentricity of the drill string, the dimensionless quantity; ρ s The unit is the rock debris density, and the unit is kg/L; ρ m The density of the drilling fluid is kg/L; mu (mu) e The effective viscosity of the drilling fluid is expressed in mPas.
Setting a limit value T of the thickness of the rock debris bed according to the actual requirements of drilling construction CBL (T CBL Limited to within 10% of the diameter of the wellbore). Primary selecting one V a T is calculated by using formulas (9) to (11) CB . If T CB Equal to or slightly greater than T CBL V is then a The minimum return speed meeting the requirement of carrying the rock is obtained. If T is calculated CB Less than T CBL Then a larger V needs to be retried a Until the requirements are met. Critical carried rock displacement Q c ：
In which Q c Is critical rock carrying displacement, and the unit is L/s.
3. A method for designing drilling parameters of a low-pressure easy-to-leak stratum.
The borehole diameter, the outer diameter of the drill pipe, and the well inclination angle are objectively difficult to change under fixed borehole structure, borehole trajectory, and drilling tool assembly conditions. The requirements of drilling leakage prevention, borehole cleaning and the like are met, and engineering parameters such as mechanical drilling speed, circulating displacement, rheological property of drilling fluid, running (casing running) speed and the like can be optimized. Based on the analysis and the model establishment, an optimal design method for the drilling parameters of the low-pressure easy-to-leak stratum is constructed, and specific steps are shown in figure 1.
(1) Collecting basic data;
collecting well body structures, well hole tracks, stratum layering, geological structures, adjacent well drilling data and the like, and laying a foundation for the optimization of drilling parameters.
(2) Predicting formation leak-off pressure and collapse pressure;
predicting the leakage pressure, namely establishing a transverse distribution profile of a main leakage horizon of the target area by carrying out statistical analysis on drilling data and interpolation; or by means of logging data, fitting a relation model of the leak-off speed, the leak-off pressure difference and the crack porosity. Collapse pressure prediction, based primarily on logging data, utilizes the "mole-coulomb" criterion to establish a collapse pressure profile. Based on the wellbore structure and the wellbore trajectory, a safe density window, i.e. "window" of the difference between the leak pressure and the collapse pressure of the open hole section, is determined.
(3) Designing the density of drilling fluid;
if the pressure window is "positive", i.e., the leak pressure is greater than the collapse pressure, the drilling fluid density design is based on the collapse pressure equivalent density (ρ=collapse pressure equivalent density+0.01-0.02 g/cm) 3 ). If the pressure window is zero or the pressure window is negative, namely the leakage pressure is smaller than the collapse pressure, the design of the drilling fluid density still takes the equivalent density of the collapse pressure as the standard, but the leakage blocking material while drilling is required to be optimized for 'early blocking', so that the stratum leakage pressure is gradually improved.
(4) The circulating displacement, the hydraulic shearing force and the plastic viscosity of the drilling fluid in drilling are designed;
analysis of cyclic displacement Q and drilling fluid shear force τ by means of reference 4 0 Plastic viscosity mu p The influence rule of the rock debris bed on the circulating pressure consumption; and (3) optimizing related parameters, and controlling the circulation friction resistance in drilling within a window range of the leakage pressure and the collapse pressure.
(5) Checking borehole cleaning and designing the rotation speed of a drill rod;
calculating critical annular return velocity V when no cuttings bed is formed by means of the public representations 8-10 c The method comprises the steps of carrying out a first treatment on the surface of the If the circulation return speed V is the current circulation displacement Q a Less than V c Then go back to step (4) to re-optimize Q, mu p And τ 0 Up to the designed circulation return speed V c ≥V a . If the cyclic displacement Q optimized by the step (4) still cannot meet the requirement V c ≥V a (i.e. the current cyclic displacement Q is at least greater than the critical carried-rock displacement Q c ) And controlling the mechanical drilling speed by increasing the rotating speed of the drill rod, and damaging and removing the rock debris bed.
(6) Designing drilling parameters of a whole well section;
repeating the steps (3) - (5), and sequentially designing drilling fluid parameters of different horizons, different well depths and different well inclinations; the drilling fluid parameters include drilling fluid density, drilling fluid circulation displacement, drilling fluid shear force, and drilling fluid plastic viscosity.
(7) Designing the running (casing running) speed;
with the aid of the disclosure 7, the drilling fluid performance parameters designed in step (6) are used to optimize the running (casing running) speed and control the fluctuating pressure (i.e., the activation pressure in this embodiment) within the "window" of the leak-off pressure and the collapse pressure.
The application effect analysis was performed by the following example.
The eastern gas field in the north of the Erdos basin adopts a horizontal well development mode, the well body structure is usually three-level, namely, one opening 311.2mm multiplied by 244.5mm, two openings 222.3mm multiplied by 177.8mm and three openings 152.4mm multiplied by 114.3mm. The second well section comprises a straight well section and an inclined well section, the leakage pressure of the formation of the Liu Jia ditch group when drilling is low, and the wall of the mudstone well of Dan Qianfeng groups and the stone box groups of the open hole section is easy to collapse. And the drilling parameters of the two-hole drilling and middle-finishing stage are optimized, so that the aim of safe drilling is fulfilled.
The JPH-4XY well is described as an example.
According to the adjacent well real drilling data and logging data, the lost pressure of the Liujia ditch group of the JPH-4XY well is predicted to be 1.15-1.20g/cm 3 Well depth 2699m of Liu Jia ditch group; while the collapse pressure at 3307m near the large well inclination A target point of the down stone box group is 1.18g/cm 3 . Meets the requirements of safe drilling, optimizes the drilling fluid density at the inclined and layered positions, and has the Liu Jia ditch group and the density of the well section of 1.05-1.08 g/cm 3 The density from the bottom of the Liu Jia ditch group to the well section of the deflecting point is 1.08-1.10 g/cm 3 Well section density of 0-30 degree well deviation is 1.10-1.12 g/cm 3 Well section density of 30-45 degrees is 1.12-1.14 g/cm 3 Well section density of 45-60 degrees is 1.14-1.16 g/cm 3 Well section density of 60-90 degrees is 1.16-1.18 g/cm 3 . In order to ensure the stability of the well wall of the lower stratum when the drilling fluid density is increased, flaky elastic graphite, bamboo fiber and rigid superfine calcium carbonate are compounded, so that the leakage pressure of the Liu family ditch group is gradually increased.
When drilling to Liu Jia ditch group, the drilling fluid density is 1.08g/cm 3 The plastic viscosity of the on-site drilling fluid is 40 Pa.s, the dynamic shear force is 6Pa, and the cuttings density is 2.4g/cm 3 The average diameter of the rock debris is 0.85cm. And optimizing engineering parameters during drilling of the Liu Jia ditch group based on the related parameters. And (3) carrying out site data statistics, wherein the average drilling speed when drilling to the Liu family ditch group is not more than 12m/h. The cyclic friction at different cyclic displacement at drilling was analyzed, see figure 2. The cyclic friction at different rates of penetration was analyzed and is shown in figure 3. In order to control the circulation friction not to be more than 1.85MPa, the circulation displacement of the Liu Jia ditch group during drilling is 20-25L/s, and the mechanical drilling speed is recommended to be 6-10m/h.
In the middle-finishing operation stage, the pressure equivalent density of the leakage pressure of the pressure-bearing Liu family ditch group is increased to 1.23-1.24g/cm gradually 3 . The faster the drill-down speed, the greater the activation pressure; the greater the plastic viscosity, the greater the dynamic shear force, the lower the run-down rate limit, see FIG. 4. If the plastic viscosity mu p =50mpa.s, dynamic force τ 0 =7pa, the drill down rate should be less than 0.4m/s; if the plastic viscosity mu p =60 mpa·s, dynamic shear force τ 0 =8pa, the drill speed should be smallAt 0.2m/s.
Lost circulation during casing is very common and is closely related to the sensitivity of activation pressure to casing running speed. As shown in FIG. 5, if the plastic viscosity is μ p =20mpa.s, dynamic force τ 0 =4pa, the running speed should be less than 0.15m/s; if the plastic viscosity mu p =30mpa.s, dynamic force τ 0 =4pa, the running speed should be less than 0.1m/s; if the plastic viscosity mu p =40 mpa·s, dynamic shear force τ 0 The drain family ditch group will be pressed when running down the cannula =5 Pa. The sealing slurry injected into the well before casing running is not higher than the Liujia ditch group at the sealing well section; by means of the sectional circulation, the plastic viscosity and the dynamic shear force of the upper well section are properly reduced, and the exciting pressure is reduced.
Based on the method, a drilling leakage-proof construction scheme and a recommended method of the Dongsheng gas field are formulated, 197 wells are popularized and applied in an accumulated mode, the horizontal well leakage rate is reduced from 57% to 25.7%, the average single well drilling fluid leakage amount is reduced by 80.6%, and the drilling period is shortened by 32.3%. The drilling period of the booster east-winning gas field is shortened, and a foundation is laid for efficient exploration and benefit development of compact natural gas.
Aiming at the drilling leakage prevention of a low-pressure spilled stratum, the method for optimally designing the drilling parameters is suitable for various working conditions such as drilling, running, casing running and the like, synthesizes the requirements of safe drilling such as drilling leakage prevention, well cleaning and the like, guides the optimal design of drilling engineering parameters, realizes the transition from 'late leaking stoppage' to 'engineering leakage prevention' and 'early leaking stoppage', greatly reduces the drilling complexity, and provides technical guarantee for improving the drilling construction efficiency and reducing the cost.
Claims (10)
1. The method for optimizing the drilling parameters of the low-pressure easy-to-leak stratum is characterized by comprising the following steps of:
1) Predicting formation leak-off pressure and collapse pressure;
2) Designing drilling fluid parameters, wherein the density of the drilling fluid is designed based on the collapse pressure equivalent density; the circulation displacement, the hydraulic shear force of the drilling fluid and the plastic viscosity are designed so that the circulation friction resistance during drilling does not exceed the difference value between the leakage pressure and the collapse pressure;
3) Calculating critical annular return speed when a rock debris bed is not formed, if the currently designed circulating return speed is smaller than the critical annular return speed, returning to the step 2) to optimize the circulating displacement, the hydraulic cutting force and the plastic viscosity of the drilling fluid again until the optimized circulating displacement meets the condition that the circulating return speed is smaller than the critical annular return speed;
4) Repeating the steps 2) and 3), designing drilling fluid performance parameters of different horizons, different well depths and different well inclinations, and completing the design of the drilling fluid performance parameters of the whole well section;
5) And optimizing the drilling parameter by optimizing the drilling or casing running speed according to the drilling fluid performance parameter and controlling the exciting pressure within the range of the difference value between the leakage pressure and the collapse pressure.
2. The method for optimizing drilling parameters of a low-pressure and easy-to-leak stratum according to claim 1, wherein in the step 1), the leak pressure is predicted by establishing a transverse distribution profile of a main leak layer of a target zone through interpolation by means of statistically analyzing drilling data; alternatively, predictions are made by fitting a model of the relationship of leak rate, leak pressure differential, and fracture porosity with the aid of logging data.
3. The method of optimizing drilling parameters of a low pressure, leak-down formation of claim 1, wherein in step 1), the collapse pressure is predicted based on logging data using a molar-coulomb criterion to establish a collapse pressure profile.
4. The method for optimizing drilling parameters of a low pressure and easy-to-leak stratum according to claim 1, wherein in the step 2), the circulating friction during drilling is composed of circulating pressure loss of drilling fluid in the whole annulus inner laminar flow section and pressure loss generated by rock debris solid phase particles in the whole annulus inner laminar flow section.
5. The method for optimizing drilling parameters of a low pressure, leak-free formation of claim 4, wherein the drilling fluid circulation pressure loss p al1 Calculated by the following formula:
wherein: l is the annular section length for calculating the pressure consumption; q is the cyclic displacement; d (D) 0 Is the diameter of the borehole; d (D) i Is the outer diameter of the drill rod. Mu (mu) p 、τ 0 The plastic viscosity and the dynamic shear force of the drilling fluid are respectively.
6. The method for optimizing drilling parameters of a low pressure and leak-free formation of claim 4, wherein the pressure loss p generated by the solid phase particles of cuttings al2 Calculated by the following formula:
p al2 ＝(ρ s -ρ)gL·C a
wherein: ρ s ρ is the density of the cuttings and drilling fluid, respectively; g is gravity acceleration; l is the annular section length for calculating the pressure consumption; c (C) a Is the annulus cuttings concentration.
7. The method for optimizing drilling parameters of a low pressure, leak-off formation of claim 6, wherein the annulus cuttings concentration C a Calculated by the following formula:
wherein R is the rate of penetration; k' is a speed correction coefficient; v (V) f The annulus return speed of the drilling fluid is set; d (D) b Is the diameter of the drill bit; d (D) 0 Is the diameter of the borehole; d (D) i Is the outer diameter of the drill rod; d, d s Is the diameter of the rock debris.
8. The method for optimizing drilling parameters of a low pressure, leak-off formation of claim 1, wherein in step 3), critical annular velocity V c Calculated by the following method:
wherein D is s Is the equivalent diameter of the rock debris particles; k is the consistency coefficient; θ is the well tilt angle; ρ s Is the rock debris density; ρ m Is the density of drilling fluid; mu (mu) e Is the effective viscosity of the drilling fluid.
9. The method for optimizing drilling parameters of a low pressure, leak-off formation of claim 8, wherein the drilling fluid has an effective viscosity μ e Calculated by the following method:
wherein K is a consistency coefficient; n is a fluidity index; d (D) o 、D i The diameter of the well bore and the outer diameter of the drill rod are respectively; v (V) a Is the return speed of the annular drilling fluid.
10. The method according to claim 1, wherein in step 3), if the optimized cyclic return speed is not smaller than the critical annular return speed, the mechanical drilling speed is controlled by increasing the rotation speed of the drill rod, and the cuttings bed is damaged and cleared.
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| CN118709602A (en) * | 2024-08-27 | 2024-09-27 | 中石化西南石油工程有限公司 | Method, device, equipment and readable storage medium for determining drilling circulation pressure loss |
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| CN118709602A (en) * | 2024-08-27 | 2024-09-27 | 中石化西南石油工程有限公司 | Method, device, equipment and readable storage medium for determining drilling circulation pressure loss |
| CN118709602B (en) * | 2024-08-27 | 2025-01-28 | 中石化西南石油工程有限公司 | Method, device, equipment and readable storage medium for determining drilling circulation pressure loss |
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