A method, apparatus, and storage medium for determining lost circulation zone fracture width

Abstract

The application provides a lost formation fracture width determination method, device and storage medium. The method comprises the following steps: S10, establishing a fracture width inversion calculation model based on drilling fluid solid phase particle size and concentration; S20, determining the volume concentration of the drilling fluid solid phase particle; S30, determining the characteristic particle size value of the drilling fluid solid phase particle; S40, calculating the maximum lost fracture width; and S50, determining the formation lost fracture width range. The application provides a fracture width inversion calculation model based on drilling fluid solid phase particle size and concentration, overcomes the neglect of the drilling fluid solid phase particle in the traditional method, can timely and accurately determine the formation lost fracture width, and provides a reliable basis for the particle size selection of the plugging material and the plugging slurry formula design.

Description

Technical Field

[0001] This invention relates to the field of drilling and completion engineering technology, and in particular to a method, device, and storage medium for determining the width of lost formation fractures. Background Technology

[0002] Fractures are the primary channels and spaces for drilling fluid loss during oil and gas and geothermal drilling. Sealing fractures with leakage prevention and plugging materials is currently the most common technical means to control drilling fluid loss. Selecting appropriate leakage prevention and plugging technologies based on the leakage conditions, choosing leakage prevention and plugging materials that match the fracture width, designing plugging slurry formulations that match the fracture width, and determining reasonable leakage prevention and plugging process parameters are crucial prerequisites for successful leakage prevention and plugging. Determining the width of leakage fractures has always been a challenge in leakage prevention and plugging technology. Currently, commonly used methods include four main categories: core observation methods, hydrodynamic methods, rock mechanics methods, and well logging methods.

[0003] Core observation methods determine fracture width by directly observing, microscopically observing, or scanning electron microscopy examining downhole cores. These methods measure the fracture width on the surface or cross-section of the core after stress release, which is significantly larger than the fracture width under underground stress loading. Cores used for observation are generally from adjacent wells, and their fracture widths may differ considerably from those in lost-loop wells; therefore, the measurement results should only be used as a reference. Furthermore, this method is limited by factors such as whether or not coring is performed in the lost-loop zone, the difficulty of coring, and the cost of coring.

[0004] The hydrodynamic method indirectly determines fracture width by measuring in-situ leakage velocity or core permeability and using hydrodynamic equations. The hydrodynamic method calculates the hydraulic width of an equivalent single flat fracture with the same leakage velocity or permeability, neglecting the effects of multiple fractures, fracture tortuosity, fracture surface micro-protrusions, and solid particles within the drilling fluid. This method is highly accurate for medium to large fractures with widths much larger than the height of fracture surface micro-protrusions and the diameter of drilling fluid solid particles, but it has larger errors for small, leak-causing fractures or fractures with widths comparable to the diameter of drilling fluid solid particles. Furthermore, when there is a long interval between leakage and plugging, the bottomhole environment has changed, and the fracture width calculated using leakage data may differ significantly from the fracture width before plugging.

[0005] Rock mechanics methods determine fracture widths under specific wellbore pressures by establishing mathematical or numerical models of the dynamic behavior of formation fractures. The calculations reflect the dynamic fracture width under varying wellbore pressures, indicating the changes in width of induced and propagating fractures under positive pressure differentials. Currently, this method primarily considers two-dimensional fractures, neglecting the effects of fracture tortuosity, surface micro-protrusions, and solid particles within the drilling fluid. The calculation results are significantly influenced by formation stress and rock mechanics properties, but these data are often difficult to obtain.

[0006] Well logging methods determine fracture width using empirical formulas based on well logging data. Well logging determines the fracture width under subsurface stress, providing the most direct and accurate measurement result. However, well logging results are affected by the resolution of the logging instrument, the accuracy of the interpretation model, and well control safety. The measurement process is generally complex, time-consuming, and costly, making widespread implementation difficult.

[0007] Chinese patent CN112127882A discloses a method for calculating the dynamic fracture width of drilling fluid leakage in fractured formations, including the following steps: selecting a model based on seismic data and fracture development characteristics and calculating the static hydraulic width of formation fractures; substituting the static hydraulic width of formation fractures into the fracture hydraulic width deformation formula to obtain the dynamic hydraulic width of wellbore fractures; converting the dynamic hydraulic width of wellbore fractures into the average mechanical width of wellbore fractures according to the mechanical width conversion formula; and solving the distribution range of fracture mechanical width based on the standard deviation of natural fracture mechanical width distribution. This patent uses a hydrodynamic method to determine fracture width, which has a relatively large error.

[0008] Chinese patent CN111472752A discloses a method for estimating fracture width while drilling using well logging data. This method first establishes a fracture width estimation model based on the amount of leakage. The model assumes the angle between the fracture surface and the horizontal plane of the wellbore is γ, with γ ranging from 0 to 90°. Different scenarios are represented by the angle γ between the wellbore axis and the fracture surface: when γ = 0°, the wellbore axis intersects the fracture surface perpendicularly; when 0 < γ < 90°, the wellbore axis intersects the fracture surface at an angle; and when γ = 90°, the wellbore axis is parallel to the fracture surface. Based on the estimation mathematical model formula, a chart curve comparison algorithm is used to calculate the fracture width. This patent belongs to the method of determining fracture width using well logging, which suffers from problems such as complex measurement procedures, long measurement cycles, and high costs. Summary of the Invention

[0009] The purpose of this invention is to address at least one of the aforementioned shortcomings of the prior art. One objective of this invention is to provide a method for quickly and accurately measuring the width range of leakage cracks.

[0010] To achieve the above objectives, the present invention provides a method for determining the width of fractures in lost formations.

[0011] The method includes the following steps: S10, establishing a fracture width inversion calculation model based on the particle size and concentration of drilling fluid solid particles; S20, determining the volume concentration of drilling fluid solid particles; S30, determining the characteristic particle size value of drilling fluid solid particles; S40, calculating the maximum leakage fracture width; S50, determining the range of leakage fracture width.

[0012] According to an exemplary embodiment of the present invention, the establishment of a fracture width inversion calculation model based on the particle size and concentration of drilling fluid solid particles may include the following steps: S11, deriving the velocity N of solid particles flowing into the fracture during well leakage or plugging. in S12. Derive the maximum allowable solid particle outflow velocity N from the crack. out , max S13. According to the crack plugging conditions: N in ≥N out,max S14. Derive the critical blockage judgment expression for fractures; S15. Derive the average particle concentration at the fracture outlet based on classical experimental data; S16. Derive the average particle velocity at the fracture outlet based on the Free Falling Arch theory; S17. Substitute the average particle concentration and average particle velocity at the fracture outlet to obtain the fracture width inversion calculation model based on the particle size and concentration of solid phase particles in the drilling fluid.

[0013] According to an exemplary embodiment of the present invention, the velocity N of the solid particles flowing into the crack in It can be calculated based on equation (1), which is:

[0014]

[0015] In equation (1), N in The velocity of solid particles flowing into the crack is given in units per second (W). i V is the width of the crack entrance, in meters. f C represents the drilling fluid velocity in m / s. enter d represents the volume concentration of solid particles flowing into the crack, dimensionless; p denoted as the diameter of the solid particle, in meters (m).

[0016] According to an exemplary embodiment of the present invention, the maximum permissible solid particle outflow velocity N out , max It can be calculated based on equation (2), which is:

[0017]

[0018] In equation (2), N out，max The maximum permissible solid particle outflow velocity is (particles / s). The average particle concentration at the crack outlet is dimensionless. d represents the average particle velocity at the crack exit, in m / s; o d represents the width of the crack exit (m); p denoted as the diameter of the solid particle, in meters (m).

[0019] According to an exemplary embodiment of the present invention, the critical blockage determination expression (3) for the crack can be:

[0020]

[0021] In equation (3), The average particle concentration at the crack outlet is dimensionless. W represents the average particle velocity at the crack exit, in m / s. o The maximum leakage crack width is in meters (m); d p Where W is the diameter of the solid particles, in meters; i V is the width of the crack entrance, in meters. f C represents the drilling fluid velocity in m / s. enter The volume concentration of solid particles flowing into the crack is dimensionless.

[0022] According to an exemplary embodiment of the present invention, the average particle concentration at the crack outlet can be calculated based on equation (4), which is:

[0023]

[0024] In equation (4), The average particle concentration at the crack exit is dimensionless; e is the natural constant; W o The maximum leakage crack width is in meters (m); d p denoted as the diameter of the solid particle, in meters (m).

[0025] According to an exemplary embodiment of the present invention, the expression (5) for the average particle velocity at the crack exit can be:

[0026]

[0027] In equation (5), βV represents the average particle velocity at the crack exit, in m / s; f It is the local fluid velocity, m / s; C D d is the drag coefficient; L is the distance the particle travels in the direction of fluid flow, in meters; d p denoted as the diameter of the solid particle, in meters (m).

[0028] According to an exemplary embodiment of the present invention, the calculation of the drag coefficient may include the following steps: measuring the density and apparent viscosity of the drilling fluid; and calculating the Reynolds number Re and the drag coefficient C using the measured drilling fluid density and apparent viscosity. D The Reynolds number Re is calculated using formula (6):

[0029]

[0030] Drag coefficient C D The calculation formula (7) is:

[0031]

[0032] In equation (6), ρ f Fluid density, kg / m³ 3 V f Drilling fluid velocity, m / s; d p Where is the diameter of the solid particles, in meters (m); μ is the diameter of the solid particles. f ρ is the fluid dynamic viscosity, Pa·s.

[0033] According to an exemplary embodiment of the present invention, the crack width inversion calculation model may include equations (8) and (9), wherein equation (8) is:

[0034]

[0035] In equation (8), λ is the intermediate coefficient. C D W is the drag coefficient. o The maximum leakage crack width is in meters (m); d p Where is the diameter of the solid particles, in meters (m).

[0036] Equation (9) is:

[0037]

[0038] In equation (9), e is the natural constant; W o The maximum leakage crack width is in meters (m); d p Where C is the diameter of the solid particles, in meters; enter The solid particle volume concentration flowing into the crack is dimensionless; λ is an intermediate coefficient.

[0039] According to an exemplary embodiment of the present invention, determining the volume concentration of drilling fluid solid particles may include determining the volume concentration of drill cuttings or determining the volume concentration of plugging material.

[0040] According to an exemplary embodiment of the present invention, the volume concentration of the drill cuttings can be determined by formula (10), which is:

[0041]

[0042] In equation (10), C enter Q represents the dimensionless volume concentration of solid particles flowing into the crack. L For leakage velocity, m 3 / h;V c The volume of drill cuttings removed by the vibrating screen per unit time during normal drilling, in meters. 3 / h;V' c The volume of drill cuttings removed by the vibrating screen per unit time after partial loss of return to the well is expressed in m. 3 / h.

[0043] According to an exemplary embodiment of the present invention, the volume concentration of the sealing material can be determined by formula (11), which is:

[0044]

[0045] In equation (11), C enter wt% represents the volume concentration of solid particles flowing into the crack, dimensionless; m represents the number of components in the plugging material; wt% i Let be the mass concentration of the i-th material, t / m³ 3 ;ρ i Let be the density of the i-th material, in g / cm³. 3 .

[0046] According to an exemplary embodiment of the present invention, determining the characteristic particle size value of the drilling fluid solid particles may include: measuring the particle size distribution of drill cuttings returned to the surface during normal drilling or the particle size distribution of the plugging formula in the most recent plugging operation using a sieve analysis method; calculating and plotting a cumulative particle size distribution curve, and reading the particle size corresponding to the solid particles with a cumulative volume fraction of 90% in the curve as the characteristic particle size value d of the drilling fluid solid particles. 90 .

[0047] According to an exemplary embodiment of the present invention, calculating the maximum leakage fracture width may include: substituting the determined volume concentration of drilling fluid solid particles and the characteristic particle size value of drilling fluid solid particles into the fracture width inversion calculation model, and performing iterative calculation through numerical calculation methods to obtain the maximum leakage fracture width W. o .

[0048] According to an exemplary embodiment of the present invention, determining the width range of the lost formation fracture may include: determining the width range of the lost formation fracture as W∈[d] by combining the measured characteristic particle size values ​​of the solid particles and the calculated maximum lost fracture width. 90 W o ].

[0049] On the other hand, the present invention provides a computer device. The computer device includes: a processor; and a memory storing a computer program, which, when executed by the processor, implements the method for determining the width of fractures in leaky formations as described above.

[0050] In another aspect, the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the method for determining the width of lost formation fractures as described above.

[0051] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0052] (1) This invention takes into account the important role of larger solid particles in drilling fluid in sealing fractures of a specific width, and provides a fracture width inversion calculation model based on the particle size and concentration of solid particles in drilling fluid. It overcomes the neglect of solid particles in drilling fluid by traditional methods, and can determine the width of formation leakage fractures in a timely and accurate manner, providing a reliable basis for the selection of particle size of plugging materials and the design of plugging slurry formulation.

[0053] (2) This invention takes into account the critical conditions for solid particles to seal cracks, directly reflecting the width of the main leakage-causing cracks in the formation, and the calculation results are more reliable.

[0054] (3) A fracture width greater than the particle size of the solid phase in the external working fluid is one of the necessary conditions for well leakage. For rigid particles of a given concentration and size, there exists a fracture plugging range, the lower limit of which is the absolute plugging width with a plugging probability of 100%, and the upper limit of which is the critical plugging width with a plugging probability of 0. Compared with the fracture width of adjacent well stress release by core observation, the equivalent hydraulic fracture width by hydrodynamics, and the theoretically calculated fracture width by rock mechanics, the fracture width calculated in this invention is the local true width within the leakage fracture, and is more representative.

[0055] (4) This invention uses drilling cuttings data or early plugging construction data to determine the width of the fracture in the lost formation. Compared with core observation and logging methods, it is faster to implement, easier to operate, and cheaper. Attached Figure Description

[0056] The above and other objects and features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0057] Figure 1 A flowchart illustrating the calculation of the fracture width in a lost formation according to an exemplary embodiment of the present invention is shown.

[0058] Figure 2 The particle size distribution diagram of the plugging formulation of Example 1 of the present invention is shown;

[0059] Figure 3 A schematic diagram of a computer device according to an exemplary embodiment of the present invention is shown.

[0060] Explanation of reference numerals in the attached figures:

[0061] 100 - Computer equipment; 101 - Memory; 102 - Processor. Detailed Implementation

[0062] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention.

[0063] Exemplary Example 1

[0064] This exemplary embodiment provides a method for determining the width of lost formation fractures based on drilling fluid solid particle information. The method includes the following steps:

[0065] S10. Establish a fracture width inversion calculation model based on the particle size and concentration of solid particles in drilling fluid.

[0066] Fractures, acting as flow channels, have a maximum permissible capacity for solid particles in the drilling fluid flowing within them. When the number of solid particles entering a fracture exceeds the local permissible capacity, the particles will block the fracture at that location and be unable to continue moving forward. Therefore, by measuring the particle size and concentration of solid particles in the drilling fluid leaking into the formation fractures, the width of the fracture can be calculated inversely based on the leakage rate.

[0067] In this embodiment, establishing a fracture width inversion calculation model based on the particle size and concentration of drilling fluid solid particles may include the following steps:

[0068] S11, Determine the velocity N of solid particles flowing into the fracture during well leakage or plugging. in .

[0069] In this embodiment, it is assumed that the width of the local crack inlet is W. i The export width is W o Drilling fluid flows at a velocity V f The solid particles flow into the crack, assuming they are spherical particles of the same size. The velocity N of the solid particles flowing into the crack is then... in Calculated based on equation (1),

[0070] Equation (1) is:

[0071]

[0072] In equation (1), N in The velocity of the solid particles flowing into the crack is given in units per second.

[0073] W i The width of the crack entrance is in meters (m).

[0074] V f The drilling fluid velocity is given in m / s.

[0075] C enter The volume concentration of solid particles flowing into the crack is dimensionless.

[0076] d p denoted as the diameter of the solid particle, in meters (m).

[0077] S12. Derive the maximum allowable solid particle outflow velocity N from the crack. out，max .

[0078] In this embodiment, the maximum particle discharge velocity N of the opening can be obtained by integrating the fluid velocity and volume concentration flowing through a certain opening over the opening area. out，max (Number of particles per unit of time):

[0079]

[0080] In the formula d o V is the diameter of the opening, r is the distance from a point to the center of the opening, and V is the diameter of the opening. exit (r) represents the open-circuit fluid velocity profile, C exit (r) represents the open particle volume concentration profile.

[0081] The above formula can be simplified to:

[0082]

[0083] The particle discharge volume concentration in the piston flow model is integrated over the simplified equation. In piston flow, C exit V is constant throughout the entire opening. exit Only at the edge of the opening (C exit =0) is when there is a significant deviation from the center line. Therefore, the particle discharge velocity can be well approximated as:

[0084]

[0085] Therefore, in this embodiment, the maximum permissible solid particle outflow velocity N out，max It can be calculated based on equation (2).

[0086] Equation (2) is:

[0087]

[0088] In equation (2), N out，max The maximum permissible solid particle outflow velocity is (particles / s).

[0089] The average particle concentration at the crack outlet is dimensionless.

[0090] The average particle velocity at the crack exit is in m / s;

[0091] d o The width of the crack exit is in meters (m).

[0092] d p denoted as the diameter of the solid particle, in meters (m).

[0093] S13. According to the crack plugging conditions: N in ≥N out,maxDerive the expression for determining critical blockage of cracks.

[0094] In this embodiment, when the particle velocity flowing into the local crack exceeds the maximum particle discharge velocity, the particles begin to clog the crack. Therefore, by comparing equation (1) and equation (2): N in ≥N out,max Using the local crack exit width W o Replace d o The expression for determining the critical blockage of the crack (3) can be obtained as follows:

[0095]

[0096] In equation (3), The average particle concentration at the crack outlet is dimensionless.

[0097] The average particle velocity at the crack exit is in m / s;

[0098] W o The maximum leakage crack width, in meters;

[0099] d p Where is the diameter of the solid particles, in meters (m).

[0100] W i The width of the crack entrance is in meters (m).

[0101] V f The drilling fluid velocity is given in m / s.

[0102] C enter The volume concentration of solid particles flowing into the crack is dimensionless.

[0103] In the formula W o =d o The maximum leakage crack width.

[0104] S14. Derive the average particle concentration at the crack outlet based on classic experimental data.

[0105] Based on empirical formulas for particle discharge concentrations with different combinations of particle size and opening size, when the opening is reduced to near the particle size, the particle volume concentration at the opening centerline tends to be 0.48, close to the assumed particle size from a point equal to d. o / d p The height of the particles obtained by passing through the openings one after another is 0.52. As the openings gradually increase in size, the particle volume concentration at the center line of the openings tends to be 0.83, which is very close to the critical particle volume concentration of 0.84 for the transition of isotropically compressed particle packing from a blocked state to a flow dynamic state.

[0106] For piston flow, C exitThe average particle concentration remains constant throughout the opening. Therefore, in this embodiment, it is assumed that the average particle concentration at the crack exit is equal to the particle concentration at the centerline. The average particle concentration at the crack exit is then calculated based on equation (4).

[0107] Equation (4) is:

[0108]

[0109] In equation (4), The average particle concentration at the crack outlet is dimensionless.

[0110] e is a natural constant;

[0111] W o The maximum leakage crack width, in meters;

[0112] d p denoted as the diameter of the solid particle, in meters (m).

[0113] S15. Derive the average particle velocity at the crack exit based on the Free Falling Arch theory.

[0114] In this embodiment, assuming that the Free Falling Arch (FFA) theory still holds in fluid-driven flows, and that particles are freely dragged by the flowing fluid rather than falling freely under gravity, then a particle dragged by a fluid satisfies the following condition in its direction of motion x:

[0115]

[0116] In the formula, a p It is the acceleration of the particle, V p Where x is the velocity of the particle, and x is the direction of fluid flow. D It is the drag coefficient, V f It is the drilling fluid velocity, βV f It refers to the local fluid velocity, which is relevant to localized cracks. W o It is the maximum leakage crack width, W i It is the width of the crack entrance, d p It is the diameter of the solid particles.

[0117] In this embodiment, boundary conditions (V) are used. p =0, x=0; Solving the equation (x=L), we obtain the expression for the average particle velocity at the crack exit (5):

[0118]

[0119] In equation (5), The average particle velocity at the crack exit is in m / s;

[0120] βV f It is the local fluid velocity, in m / s;

[0121] C D This is the drag coefficient;

[0122] L is the distance the particle travels in the direction of fluid flow, in meters (m).

[0123] d p denoted as the diameter of the solid particle, in meters (m).

[0124] In this embodiment, the calculation of the drag coefficient may include the following steps:

[0125] Measure the density and apparent viscosity of the drilling fluid; use the measured density and apparent viscosity to calculate the Reynolds number Re and the drag coefficient C. D The Reynolds number Re is calculated using formula (6):

[0126]

[0127] Drag coefficient C D The calculation formula (7) is:

[0128]

[0129] In equation (6), ρ f Fluid density, kg / m³ 3 ;

[0130] V f The drilling fluid velocity is given in m / s.

[0131] d p Where is the diameter of the solid particles, in meters (m).

[0132] μ f ρ is the fluid dynamic viscosity, Pa·s.

[0133] The drag coefficient of solid particles in drilling fluid is a function of the particle Reynolds number, which in turn is a function of the drilling fluid velocity, density, viscosity, and particle diameter. After lost circulation or plugging operations, data such as drilling fluid density, apparent viscosity, leakage rate, drill cuttings, or plugging material are collected on-site. 90 The particle Reynolds number Re is calculated using equation (6), and the drag coefficient C can be obtained by substituting it into equation (7). D .

[0134] S16. Substitute the average particle concentration and average particle velocity at the fracture outlet to obtain the fracture width inversion calculation model based on the particle size and concentration of solid phase particles in the drilling fluid.

[0135] In this embodiment, substituting the formula (4) for calculating the average particle concentration at the crack outlet into the expression (3) for determining the critical blockage of the crack, we can obtain the following:

[0136]

[0137] Substitution The above formula can be rewritten as:

[0138]

[0139] In this embodiment, let L=W o Then, equation (5) and the above equation can be used to obtain the crack width inversion calculation models equations (8) and (9), where,

[0140] Equation (8) is:

[0141]

[0142] In equation (8), λ is the intermediate coefficient.

[0143] C D This is the drag coefficient;

[0144] W o The maximum leakage crack width, in meters;

[0145] d p denoted as the diameter of the solid particle, in meters (m).

[0146] Equation (9) is:

[0147]

[0148] In equation (9), e is the natural constant;

[0149] W o The maximum leakage crack width, in meters;

[0150] d p Where is the diameter of the solid particles, in meters (m).

[0151] C enter The volume concentration of solid particles flowing into the crack is dimensionless.

[0152] λ is the intermediate coefficient.

[0153] S20. Determine the volume concentration of solid particles in the drilling fluid.

[0154] In this embodiment, the solid particles in the drilling fluid can be drill cuttings with larger particle sizes, which play a decisive role in the process of sealing fractures.

[0155] In this embodiment, C enter When the volume concentration of drill cuttings is determined, it can be calculated by the volume of drilling fluid returned per unit time, the volume of drill cuttings removed by the vibrating screen, and the leakage rate.

[0156] During normal drilling, the drill bit breaks the rock and produces drill cuttings. Some of these cuttings form a filter cake, while the remainder is circulated back to the surface by the drilling fluid. The volume of drilling fluid returned per unit time is V0, and the volume of drill cuttings removed by the vibrating screen is V. c For the same formation, with drilling parameters and drilling fluid properties remaining essentially unchanged, the rate of drill cuttings generation is stable, and therefore the concentration and size of the drill cuttings returned to the surface are also relatively stable.

[0157] After well leakage, some drill cuttings are lost into the formation with the drilling fluid, while the remaining drill cuttings are returned to the surface with the drilling fluid. If the drilling fluid is completely lost after well leakage, it is considered that the drill cuttings were lost at a leakage rate Q. L All drilling fluid leaks into formation fractures; if some drilling fluid is lost after well leakage, the volume of drill cuttings removed by the vibrating screen per unit time is V'. c The leakage rate is Q. L The volume concentration of drilling fluid solid particles that leak into formation fractures can be determined by equation (10).

[0158] Equation (10) is:

[0159]

[0160] In equation (10), C enter The volume concentration of solid particles flowing into the crack is dimensionless.

[0161] Q L For leakage velocity, m 3 / h;

[0162] V c The volume of drill cuttings removed by the vibrating screen per unit time during normal drilling, in meters. 3 / h;

[0163] V' c The volume of drill cuttings removed by the vibrating screen per unit time after partial loss of return to the well is expressed in m. 3 / h.

[0164] S30. Determine the characteristic particle size value of the solid phase particles in the drilling fluid.

[0165] For a homogeneous particulate system, d p It is the diameter of a single particle. For a particle system with a certain particle size distribution, d p It is a particle size range. Studies have found that clogging in polydisperse particle systems is mainly caused by large particles (d... p ≥d 90The decision is based on the fact that the bridging structures causing blockages are primarily composed of these large particles. The blockage probability of particle systems with a wide particle size distribution correlates poorly with the volume average diameter but strongly with d0 / d 90 The correlation is very good. For particle systems with different particle size distributions, d 90 If the particle systems are the same, the probability of blockage at the same opening is the same, and their critical and absolute blockage d0 / d 90 The same applies to both polydisperse and homogeneous particle systems. 90 If they are the same, then the critical and absolute blocking d0 / d 90 They are basically the same. Therefore, d 90 It can be used as a characteristic particle size for calculating crack width in particle systems with particle size distribution.

[0166] In this embodiment, during normal drilling, drill cuttings returned to the surface are collected periodically, and their particle size distribution is determined using a sieving method. A cumulative particle size distribution curve is plotted using the measured particle size distribution data. The particle size value corresponding to the drill cuttings with a cumulative volume fraction of 90% is taken as the characteristic particle size value d of the drilling fluid solid phase particles. 90 .

[0167] S40. Calculate the maximum leakage crack width.

[0168] In this embodiment, the determined drag coefficient C D Volume concentration C of solid particles in drilling fluid enter Characteristic particle size d of drilling fluid solid particles 90 Substituting these equations into the crack width inversion calculation model, i.e., equations (8) and (9), the maximum leakage crack width W can be obtained through iterative calculation using numerical methods. o .

[0169] S50. Determine the width range of fractures in the lost formation.

[0170] In this embodiment, the characteristic particle size of the solid particles is combined with the calculated maximum leakage fracture width, with the drilling fluid solid particle d 90 The lower limit of the leakage crack width is used as the calculation limit for the maximum leakage crack width W. o As the upper limit, the width range of the lost formation fracture is determined to be W∈[d]. 90 W o ].

[0171] Exemplary Example 2

[0172] This exemplary embodiment provides another method for determining the width of lost formation fractures based on drilling fluid solid particle information. The method is largely the same as the method described in Exemplary Embodiment 1, except that:

[0173] S20. Determine the volume concentration of solid particles in the drilling fluid.

[0174] In this embodiment, the solid particles in the drilling fluid can be the plugging material in the plugging slurry, and the plugging material also plays a decisive role in the process of sealing the fracture.

[0175] In this embodiment, C enter When determining the volume concentration of the sealing material, it can be determined through the sealing slurry formula and the density of the sealing material.

[0176] Assume the sealing grout is composed of m types of sealing materials, where the mass concentration of the i-th material is wt%. i The density is ρ i The volume concentration of the plugging material that leaks into the formation fractures can be determined by equation (11).

[0177] Equation (11) is:

[0178]

[0179] In equation (11), C enter The volume concentration of solid particles flowing into the crack is dimensionless.

[0180] m represents the number of different types of sealing materials;

[0181] wt i Let be the mass concentration of the i-th material, t / m³ 3 ;

[0182] ρ i Let be the density of the i-th material, in g / cm³. 3 .

[0183] S30. Determine the characteristic particle size value of the solid phase particles in the drilling fluid.

[0184] In this embodiment, during the plugging process, the plugging formula from the previous operation is collected, and the particle size distribution of the plugging formula is determined using a sieving method. A cumulative particle size distribution curve is plotted using the measured particle size distribution data, and the particle size value corresponding to the plugging material with a cumulative volume fraction of 90% in the curve is taken as the characteristic particle size value d of the drilling fluid solid phase particles. 90 .

[0185] Exemplary Example 3

[0186] This exemplary embodiment provides a method for determining the width of a leakage crack, the method flow is as follows: Figure 1 As shown, the specific steps include:

[0187] A1. Establish a fracture width inversion calculation model based on the particle size and concentration of solid particles in drilling fluid.

[0188] A2. Determine the volume concentration of solid particles in the drilling fluid based on the information of drill cuttings returned before and after well leakage or the data from the most recent plugging operation.

[0189] In this embodiment, the type of solid particles in the drilling fluid is determined to be either drill cuttings or bridging and plugging material.

[0190] In this embodiment, if the solid particles in the drilling fluid are drill cuttings, the volume concentration of the solid particles can be determined by the volume of drilling fluid returned per unit time, the volume of drill cuttings removed by the vibrating screen, and the leakage rate. If the drilling fluid is completely lost after well leakage, it is assumed that the drill cuttings are concentrated at a leakage rate Q. L All drilling fluid leaks into formation fractures; for partial loss of drilling fluid return after well leakage, the volume of drill cuttings removed by the vibrating screen per unit time is V'. c During normal drilling, the volume of drill cuttings removed by the vibrating screen is V. c The leakage rate is Q. L Therefore, the volume concentration of drill cuttings that leaked into the formation fractures is:

[0191]

[0192] In this embodiment, if the drilling fluid solid particles are the plugging material, the volume concentration of the drilling fluid solid particles can be determined by the plugging slurry formulation and the density of the plugging material. Assume the plugging slurry is composed of m types of plugging materials, where the mass concentration of the i-th material is wt%. i The density is ρ i The volume concentration of the plugging material that leaks into the formation fissures is:

[0193]

[0194] A3. Use sieving to measure the particle size distribution of drill cuttings or plugging formulations to determine the characteristic particle size of solid particles in drilling fluids.

[0195] In this embodiment, the particle size distribution of drill cuttings returned to the surface during normal drilling or the particle size distribution of the plugging formula from the most recent plugging operation is measured using a sieving method. The cumulative particle size distribution curve of the plugging formula is calculated and plotted. The particle size corresponding to the solid particles with a cumulative volume fraction of 90% in the graph is d. 90 value.

[0196] A4. Calculate the Reynolds number based on drilling fluid information, and calculate the drag force coefficient using the empirical formula of drag force coefficient - Reynolds number.

[0197] In this embodiment, the drilling fluid information includes the drilling fluid density and apparent viscosity.

[0198] In this embodiment, the method for determining the drag force coefficient is as follows:

[0199]

[0200] The formula for calculating the particle Reynolds number Re is:

[0201]

[0202] A5. Based on the data in A2 to A4, use the model established in A1 to calculate the crack width.

[0203] Substitute the drag coefficient C determined in A2 to A4 D Volume concentration C of solid particles in drilling fluid enter Characteristic particle size d of drilling fluid solid particles 90 The maximum leakage crack width W was obtained by iterative calculation using numerical methods. o .

[0204] A6. Combine the characteristic particle size of the drilling fluid solid particles with the calculated fracture width to determine the range of leakage fracture width.

[0205] drilling fluid solid particles d 90 The lower limit of the leakage crack width is defined by the calculated leakage crack width W. o If the upper limit is , then the width range of the leakage crack is W∈[d]. 90 W o ].

[0206] To better understand exemplary embodiments of the present invention, further explanation is provided below with reference to specific examples.

[0207] Example 1

[0208] The method for determining the width of lost formation fractures based on drilling fluid solid particle information, as described in this invention, is used for specific calculations:

[0209] Step 1: Determine the type of solid particles in the drilling fluid as a bridging and plugging material.

[0210] Step 2: Based on the collected information on the on-site leak sealing formula and materials, the mass concentration and density of each leak sealing material are shown in Table 1 below:

[0211] Table 1

[0212]

[0213] Step 3: Calculate the volume concentration C of the sealing material using the data in the table above. enter :

[0214]

[0215] In the formula wt i ρ represents the mass concentration of the i-th type of sealing material; iLet be the density of the i-th type of sealing material.

[0216] Substitute the data to obtain the volume concentration C of the sealing material. enter It is 17.37%.

[0217] Step 4: Use the sieving method to measure the particle size distribution of the plugging formula and record the measurement data.

[0218] Step 5: Use the measurement data from Step 4 to plot the cumulative particle size distribution curve of the plugging formulation, such as... Figure 2 As shown in the figure, the particle size corresponding to a cumulative volume fraction of 90% is d. 90 Its value is 3.00 mm.

[0219] Step 6: The drilling fluid density was measured to be 1.67 g / cm³ using a drilling fluid density meter. 3 The apparent viscosity of the drilling fluid was measured to be 30 mPa·s using a six-speed rotational viscometer.

[0220] Step 7: Calculate the Reynolds number Re and drag coefficient C using the measured drilling fluid density and apparent viscosity data. D :

[0221]

[0222]

[0223] In the formula ρ f For fluid density, μ f This refers to the fluid dynamic viscosity.

[0224] Substituting the data, the Reynolds number is 16.7 and the drag coefficient is 2.86.

[0225] Step 8: Use the obtained drag coefficient C D , Leakage sealing material volume concentration C enter Leak sealing materials d 90 Calculate the maximum width W of the leakage crack o :

[0226]

[0227]

[0228] In the formula, λ is the intermediate coefficient; C D W is the drag coefficient. o d is the maximum leakage crack width; p C is the diameter of the solid particles; enter This refers to the volume concentration of the sealing material.

[0229] Substituting the data, the maximum leakage crack width W is obtained through numerical calculation. oIt is 6.4mm.

[0230] Step 9: Combine with leak-sealing formula d 90 That is, the width range of the leakage crack is determined to be 3 to 6.4 mm.

[0231] The method for determining the width of lost formation fractures based on drilling fluid solid particle information according to the present invention can be programmed into a computer program and the corresponding program code or instructions can be stored in a computer-readable storage medium. When the program code or instructions are executed by a processor, the processor performs the above-mentioned method for determining the width of lost formation fractures based on drilling fluid solid particle information. The processor and memory can be included in a computer device.

[0232] Exemplary Example 4

[0233] An exemplary embodiment of another aspect of the present invention also provides a computer-readable storage medium storing a computer program. The computer-readable storage medium stores a computer program that, when executed by a processor, causes the processor to execute the method for determining the width of lost formation fractures based on drilling fluid solid particle information according to the present invention. The computer-readable recording medium is any data storage device capable of storing data read by a computer system. Examples of computer-readable recording media include: read-only memory, random access memory, read-only optical disk, magnetic tape, floppy disk, optical data storage device, and carrier waves (such as data transmission via the Internet through wired or wireless transmission paths).

[0234] Exemplary Example 5

[0235] An exemplary embodiment of another aspect of the present invention also provides a computer device.

[0236] In this embodiment, as Figure 3 As shown, the computer device 100 includes a memory 101 and a processor 102. The memory 101 stores computer programs. The computer programs are executed by the processor 102, causing the processor 102 to execute the computer program of the method for determining the width of lost formation fractures based on drilling fluid solid particle information according to the present invention.

[0237] In summary, this invention establishes an inversion calculation model for fracture width based on the particle size and concentration of solid phase particles in drilling fluid, thereby determining the range of leakage fracture width. This method can conveniently and in real-time determine the width of leakage fractures using drilling field data, providing a more accurate basis for designing plugging formulations and determining plugging construction parameters, thus improving the success rate of plugging.

[0238] Although the invention has been described above in conjunction with exemplary embodiments, those skilled in the art will understand that various modifications and changes can be made to the exemplary embodiments of the invention without departing from the spirit and scope defined by the claims.

Claims

1. A method for determining the width of fractures in a lost formation, characterized in that, The method includes the following steps: S10. Establish a fracture width inversion calculation model based on the particle size and concentration of solid particles in drilling fluid; S20. Determine the volume concentration of solid particles in the drilling fluid; S30. Determine the characteristic particle size value of the solid phase particles in the drilling fluid. S40. Calculate the maximum leakage crack width; S50. Determine the width range of the fractures in the lost formation; The establishment of the fracture width inversion calculation model based on the particle size and concentration of solid particles in drilling fluid includes the following steps: S11, deriving the velocity of solid particles flowing into the fracture during well leakage or plugging. N in S12. Derive the maximum allowable solid particle outflow velocity from the crack. N out，max S13. According to the crack plugging conditions: S14. Derive the critical blockage judgment expression for fractures; S15. Derive the average particle concentration at the fracture outlet based on classical experimental data; S16. Derive the average particle velocity at the fracture outlet based on the Free falling arch theory; S17. Based on the average particle concentration and average particle velocity at the fracture outlet, obtain the fracture width inversion calculation model based on the particle size and concentration of drilling fluid solid phase particles. The calculation of the maximum leakage fracture width includes: substituting the determined volume concentration and characteristic particle size of the drilling fluid solid particles into the fracture width inversion calculation model, and then performing iterative calculations using numerical methods to obtain the maximum leakage fracture width. W o ; The maximum permissible solid particle effluent velocity N out，max Based on equation (2), the calculation is as follows: ; In equation (2), N out，max The maximum permissible solid particle outflow velocity is (particles / s). The average particle concentration at the crack outlet is dimensionless. The average particle velocity at the crack exit is given in m / s. d o The width of the crack exit is in meters (m). d p Where is the diameter of the solid particles, in meters (m). The critical blockage determination expression (3) for the crack is: ; In equation (3), W o The maximum leakage crack width, in meters; W i The width of the crack entrance is in meters (m). V f The drilling fluid velocity is given in m / s. C enter The volume concentration of solid particles flowing into the crack is dimensionless. The average particle concentration at the crack outlet is calculated based on equation (4), which is: ； In equation (4), e It is a natural constant; The expression for the average particle velocity at the crack exit (5) is: ； In equation (5), βV f It is the local fluid velocity, in m / s; β =W i 2 / W o 2 , C D This is the drag coefficient; L Let be the distance the particle travels in the direction of fluid flow, in meters (m). The crack width inversion calculation model includes equations (8) and (9), wherein, Equation (8) is: ； In equation (8), λ As an intermediate coefficient, ; Equation (9) is: ； In equation (9), e It is a natural constant.

2. The method for determining the width of fractures in lost formations according to claim 1, characterized in that, The velocity of the solid particles flowing into the crack N in Calculated based on equation (1), Equation (1) is: ； In equation (1), N in The velocity of the solid particles flowing into the crack is given in units per second. W i The width of the crack entrance is in meters (m). V f The drilling fluid velocity is given in m / s. C enter The volume concentration of solid particles flowing into the crack is dimensionless. d p denoted as the diameter of the solid particle, in meters (m).

3. The method for determining the width of fractures in lost formations according to claim 1, characterized in that, The calculation of the drag coefficient includes the following steps: Measure the density and apparent viscosity of drilling fluid; Calculate the Reynolds number (Re) and drag coefficient using the measured drilling fluid density and apparent viscosity. C D The Reynolds number Re is calculated using formula (6): ； drag coefficient C D The calculation formula (7) is: ； In equation (6), ρ f Fluid density, kg / m³ 3 ; V f The drilling fluid velocity is given in m / s. d p Where is the diameter of the solid particles, in meters (m). μ f ρ is the fluid dynamic viscosity, Pa·s.

4. The method for determining the width of fractures in lost formations according to claim 1, characterized in that, Determining the volume concentration of solid particles in the drilling fluid includes determining the volume concentration of drill cuttings or the volume concentration of plugging material.

5. The method for determining the width of fractures in leaky formations according to claim 4, characterized in that, The volume concentration of the drill cuttings is determined by equation (10). Equation (10) is: ； In equation (10), C enter The volume concentration of solid particles flowing into the crack is dimensionless. Q L For leakage velocity, m 3 / h; V c The volume of drill cuttings removed by the vibrating screen per unit time during normal drilling, in meters. 3 / h; The volume of drill cuttings removed by the vibrating screen per unit time after partial loss of return to the well is expressed in m. 3 / h.

6. The method for determining the width of fractures in lost formations according to claim 4, characterized in that, The volume concentration of the plugging material is determined by equation (11). Equation (11) is: ； In equation (11), C enter The volume concentration of solid particles flowing into the crack is dimensionless. m The number of different types of materials used in sealing leaks; wt i For the first i Mass concentration of the material, t / m 3 ; ρ i For the first i The density of the material, g / cm³ 3 .

7. The method for determining the width of fractures in lost formations according to claim 1, characterized in that, The determination of the characteristic particle size values ​​of drilling fluid solid particles includes: The particle size distribution of drill cuttings returned to the surface during normal drilling or the particle size distribution of the most recent plugging formulation during plugging operations is measured using the sieving method. A cumulative particle size distribution curve is calculated and plotted, and the particle size corresponding to the solid particles with a cumulative volume fraction of 90% in the curve is taken as the characteristic particle size value of the drilling fluid solid particles. d 90 .

8. The method for determining the width of fractures in lost formations according to claim 1, characterized in that, The determination of the width range of the lost formation fracture includes: The width range of the leakage formation fractures was determined by combining the measured characteristic particle size values ​​of the solid particles and the calculated maximum leakage fracture width. W ∈[ d 90 , W o ].

9. A computer device, characterized in that, The computer device includes: processor; and The memory stores a computer program that, when executed by a processor, implements the method for determining the width of a lost formation fracture as described in any one of claims 1 to 8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method for determining the width of the lost formation fracture as described in any one of claims 1 to 8.

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