Transient extended reach well cleaning state prediction method based on well temperature and drill string rotation

Abstract

The invention relates to the technical field of oil and gas wells, and provides a transient extended reach well cleaning state prediction method based on well temperature and drill string rotation, and the method comprises the steps: building an extended reach well model according to design parameters of an extended reach well, and setting the type and flow velocity of fluid in a horizontal annulus in the extended reach well model; determining a control equation set of the extended reach well model; the method comprises the following steps: performing simulation by using an extended reach well model, solving a mass conservation equation and a momentum conservation equation in a control equation of the extended reach well model based on an SETS method, performing simulation calculation on the momentum conservation equation and the mass conservation equation corresponding to each moment, and performing correction; the liquid-solid two-phase flow velocity in the cuttings bed layer, the liquid-phase flow velocity in the suspension layer, the solid-phase flow velocity in the suspension layer, the cuttings concentration in the suspension layer, the height of the cuttings bed layer and the pressure in the axial position of the shaft at all moments are obtained, and the cleaning state of the transient extended reach well is predicted. The method can accurately predict the cleaning state of the transient extended reach well.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas wells, and in particular to a method for predicting the cleaning state of a transient extended-reach well based on well temperature and drill string rotation. Background Art

[0002] The development of oil and gas resources using long horizontal section extended-reach wells has become an important technical means to ensure energy security. More than 60% of downhole accidents during the drilling of extended-reach horizontal wells are caused by insufficient wellbore cleaning. Therefore, the prediction and diagnosis of the wellbore cleaning status in land and offshore well sections is extremely important to ensure the optimal and fast construction of extended-reach horizontal wells.

[0003] The borehole cleanliness status of extended-reach wells is mainly described by the annular cuttings bed height and annular cuttings concentration, which is affected by many factors, including drilling fluid displacement, drilling fluid density, drilling fluid rheology, borehole size, drill string size, drill string eccentricity, well inclination, cuttings size, mechanical drilling speed and drill string speed. These factors show a complex nonlinear relationship with the borehole cleanliness status and have no monotonic characteristics. Oil-based and synthetic-based drilling fluids are commonly used in marine extended-reach wells. Their density and rheology are greatly affected by downhole temperature, and the density and rheology of drilling fluids are important factors affecting the rock-carrying capacity of drilling fluids. At the same time, some experimental data and field practices show that drill string rotation has a significant positive effect on the migration of cuttings in horizontal wells.

[0004] At present, the evaluation methods of the clean status of inclined wellbore are mainly divided into three categories: cuttings particle mechanics model, annular flow stratification model and statistical regression model based on experimental data. However, all three methods have certain defects. Among them, the velocity determined by the cuttings particle mechanics model is the local velocity in the eccentric annulus, and the velocity is generally used as the average flow velocity in engineering, which leads to the critical displacement predicted by the cuttings particle mechanics model being significantly lower than the actual displacement; the annular flow stratification model does not consider the influence of drill string rotation, resulting in the calculated critical displacement being higher than the actual engineering demand, and the error of the borehole clean status diagnosis result is large; the experimental data based on the statistical regression model comes from a small-sized wellbore with a well diameter of 203 mm, which is difficult to be applied to the key well section with a well diameter of 311 mm in the marine large displacement well, and the scope of application is limited.

[0005] In summary, the evaluation methods for the cleanliness of inclined wellbore currently used do not fully consider the influence of downhole temperature on the rheology of drilling fluid and the effect of drill string rotation on cuttings migration, resulting in a large deviation between the predicted results of the cleanliness of the wellbore and the actual situation. Summary of the invention

[0006] The purpose of the present invention is to solve at least one technical problem in the background technology and to provide a method for predicting the cleaning state of a transient extended-displacement well based on well temperature and drill string rotation.

[0007] To achieve the above object, the present invention provides a method for predicting the cleaning state of a transient extended reach well based on well temperature and drill string rotation, comprising:

[0008] S1. construct an extended reach well model according to the design parameters of the extended reach well, and set the fluid type and flow rate in the horizontal annulus of the extended reach well model;

[0009] S2. Establishing a mass conservation equation and a momentum conservation equation, forming a nonlinear first-order partial differential control equation group through the mass conservation equation and the momentum conservation equation, establishing an auxiliary equation, substituting the auxiliary equation into the nonlinear first-order partial differential control equation group to form a nonlinear first-order partial differential control equation group for determining unknown variables;

[0010] S3. Using the extended displacement well model for simulation, the mass conservation equation and momentum conservation equation in the nonlinear first-order partial differential control equation group of the extended displacement well model are solved based on the SETS method. The downhole temperature, pressure and drill string speed are combined to simulate and calculate the momentum conservation equation and mass conservation equation corresponding to each moment and make corrections to obtain the liquid-solid two-phase flow velocity v1 in the cuttings bed and the liquid phase flow velocity v in the suspension layer at each moment. l2 , solid phase velocity v in the suspended layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore to predict the cleaning state of the transient extended reach well.

[0011] According to one aspect of the present invention, the method of constructing an extended reach well model according to the design parameters of the extended reach well and setting the fluid type and flow rate in the horizontal annulus in the extended reach well model includes:

[0012] According to the design parameters of the extended reach well, the well inclination angle φ and the wellbore diameter D of the extended reach well are obtained. h 、Drill string outer diameter D p and drill string eccentricity s;

[0013] An extended reach well model is constructed according to the design parameters of the extended reach well, wherein the extended reach well model includes a wellbore model and a drill string model, the drill string model is connected to a drill bit, and the entire extended reach well model is divided into a vertical section, a deflection section, and an inclined section. The drill string model is arranged in the wellbore model according to the eccentricity, and the space between the drill string model and the wellbore model forms a horizontal annulus;

[0014] The fluid in the horizontal annulus is provided with a liquid-solid two-phase flow, and the liquid-solid two-phase flow is formed by a mixture of drilling fluid and rock cuttings particles; the upper space of the horizontal annulus is suspended with rock cuttings particles to form a suspended layer, and the lower space of the horizontal annulus is evenly piled with settled rock cuttings particles to form a rock cuttings bed;

[0015] The flow velocities of the liquid phase and the solid phase in the suspension layer are different. The flow velocity of the liquid phase in the suspension layer is set to v l2 , solid phase flow rate is v s2 The cross-sectional area of ​​the suspension layer is A2, and the wetted perimeter of the suspension layer in contact with the inner wall of the wellbore model is L 2，out , the wetted perimeter of the suspended layer and the drill string model L 2，in , the concentration of rock debris in the suspension layer is C s2 ;

[0016] The flow velocities of the liquid phase and the solid phase in the cuttings bed are the same. The liquid phase flow velocity and the solid phase flow velocity in the cuttings bed are equal to the liquid-solid two-phase flow velocity v1 in the cuttings bed. The height of the cuttings bed is h, the cross-sectional area is A1, and the wetted perimeter of the cuttings bed in contact with the inner wall of the wellbore model is L. 1，out The contact wet perimeter between the cuttings bed and the drill string model is L 1，in , the cuttings concentration in the cuttings bed is C s1 .

[0017] According to one aspect of the present invention, the mass conservation equation includes the suspended layer liquid phase mass conservation equation, the suspended layer solid phase mass conservation equation and the cuttings bed mass conservation equation, and the momentum conservation equation includes the suspended layer liquid phase momentum conservation equation, the suspended layer solid phase momentum conservation equation and the cuttings bed momentum conservation equation;

[0018] The auxiliary equations include mechanical equations, drilling fluid PVT equations, drilling fluid rheological temperature-pressure relationship equations, and wellbore purification and lifting degree equations for drill string rotation;

[0019] The mechanical equation is used to determine the shear stress τ2 between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model, the shear stress τ between the suspension layer and the cuttings bed interface l2 , the drag force F between the solid and liquid phases in the suspension layer sf , the shear stress τ1 between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model, the dry friction resistance F1 between the solid phase in the cuttings bed per unit length and the inner wall of the wellbore model and the outer wall of the drill string model, and the sedimentation velocity v of the cuttings particles dep , rock debris particle resuspension velocity v ent ;

[0020] After substituting the auxiliary equation into the nonlinear first-order partial differential control equation group, it is determined that the unknown variables in the nonlinear first-order partial differential control equation group include: the liquid-solid two-phase flow velocity v1 in the cuttings bed, the liquid phase flow velocity v in the suspension layer l2 , solid phase velocity v in the suspended layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore.

[0021] According to one aspect of the present invention, the mass conservation equation of the suspension layer liquid phase is:

[0022]

[0023] In the formula, t is time; s is the well depth direction; C l2 is the liquid volume fraction of the suspension layer; A2 is the cross-sectional area of ​​the suspension layer; ρ1 is the drilling fluid density; v l2 is the liquid phase flow rate in the suspension layer; Γ ent，1 is the solid mass entering the cuttings bed from the suspension layer per unit time and unit length; Γ dep，l is the mass of liquid entering the cuttings bed from the suspension layer per unit time;

[0024] The solid mass conservation equation of the suspended layer is:

[0025]

[0026] In the formula, C s2 is the concentration of rock debris in the suspended layer; ρ s is the rock cuttings density; v s2 is the solid phase flow rate in the suspension layer; Γ ent，s is the solid mass entering the suspension layer from the cuttings bed per unit time and unit length; Γ dep，s is the mass of solid phase entering the cuttings bed from the suspension layer per unit time and unit length;

[0027] The mass conservation equation of the cuttings bed is:

[0028]

[0029] Where A1 is the cross-sectional area of ​​the cuttings bed, D h is the borehole diameter, θ h is the angle between the top surface of the outer wall of the cuttings bed and the center of the wellbore model, D p is the outer diameter of the drill string, θ p is the angle between the top surface of the inner wall of the cuttings bed and the center of the drill string model; ρ1 is the density of the mixture in the cuttings bed, ρ1 = C s2 ρ s +(1-C s2 )ρ1, where C s2 +C 12 =1; v1 is the liquid-solid two-phase flow velocity in the cuttings bed;

[0030] In the formula, Γ dep，l and Γdep，s They are:

[0031]

[0032] In the formula, C s1 is the cuttings concentration in the cuttings bed, C l1 is the liquid volume fraction of the cuttings bed, C s1 +C l1 =1;L 12 is the contact length, L 12 =D h sinθ h -D p sinθ p ;v dep is the deposition rate of rock debris particles;

[0033] In the formula, Γ ent，l and Γ dep，s They are:

[0034] Γ ent，l =C l1 ρ1L 12 v ent ;

[0035] Γ ent，s =C s1 ρ s L 12 v ent ;

[0036] In the formula, v ent is the resuspension velocity of rock cuttings particles;

[0037] The momentum conservation equation of the suspended layer liquid phase is:

[0038] Where g is the gravitational acceleration; φ is the well inclination angle; L2 is the contact length between the suspension layer and the inner wall of the wellbore model and the drill string model, L2 = L 2，in +L 2，out =Π(D h +D p )-L1; L1 is the contact length between the cuttings bed and the inner wall of the wellbore model and the drill string model, L1=L 1，in +L 1，out =D h θ h +D p θ p ; τ2 is the shear stress between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model; F sf is the drag force between the solid and liquid phases in the suspension layer;

[0039] The solid phase momentum conservation equation of the suspended layer is:

[0040] In the formula, τ12 is the shear stress between the interface of the suspended layer and the cuttings bed;

[0041] The momentum conservation equation for the cuttings bed is:

[0042] Where τ1 is the shear stress between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model, and F is the dry friction resistance between the solid phase in the cuttings bed per unit length and the inner wall of the wellbore model and the outer wall of the drill string model.

[0043] According to one aspect of the present invention, in the mechanical equation, the shear stress τ2 between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model is:

[0044]

[0045] in,

[0046]

[0047]

[0048] Where f2 is the friction coefficient of the suspension layer; Re2 is the Reynolds number of the suspension layer; D2 is the hydraulic diameter of the suspension layer, M is the fluidity index, k is the liquid phase consistency coefficient;

[0049] The shear stress τ between the suspension layer and the cuttings bed interface 12 for:

[0050]

[0051] in,

[0052]

[0053] In the formula, f 12 is the interfacial friction coefficient between the suspension layer and the cuttings bed; Re 12 is the Reynolds number between the suspension layer and the cuttings bed interface; d c is the diameter of the cuttings;

[0054] The drag force F between the solid and liquid phases in the suspension layer sf for:

[0055]

[0056] in,

[0057]

[0058] In the formula, C Dis the drag coefficient; Re p is the particle Reynolds number;

[0059] The shear stress τ1 between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model is:

[0060]

[0061] in,

[0062]

[0063] Where f1 is the friction coefficient of the cuttings bed; Re1 is the Reynolds number of the cuttings bed; D1 is the hydraulic diameter of the cuttings bed, μ1 is the consistency coefficient of the cuttings bed mixture, which is determined by correcting the liquid phase consistency coefficient k according to the cuttings concentration of the cuttings bed;

[0064] The dry friction resistance F between the solid phase in the unit length of the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model is:

[0065]

[0066] Where η is the dry friction coefficient;

[0067] The rock cuttings particle settling velocity v dep for:

[0068] v dep =(1-C s2 ) m v p ;

[0069] in,

[0070]

[0071] Where m is the sedimentation velocity constant; Re dep is the particle Reynolds number when the cuttings particles are settling; v p is the settling velocity of a single rock cutting particle;

[0072] The resuspension velocity of the cuttings particles from the cuttings bed to the suspension layer is assumed to be a linear relationship between the friction velocities of the two layers, and the resuspension velocity v of the cuttings particles is determined. ent for:

[0073]

[0074] in,

[0075]

[0076] In the formula, m entis the resuspension coefficient of rock debris particles; v 12 is the friction speed; is the critical friction velocity; α is the repose angle of the cuttings bed, in degrees; C′ D is the drag force coefficient based on friction speed, and its value is 0.4.

[0077] According to one aspect of the present invention, the drilling fluid PVT equation is:

[0078] ρ l =ρ 10 e Γ(p，T) ;

[0079] in,

[0080] Γ(p, T) = γ P (p-p0)+γ PP (p-p0) 2 +γ T (T-T0)+γ TT (T-T0) 2 +γ PT (p-p0)(T-T0);

[0081] In the formula, ρ l0 is the density of drilling fluid under ground temperature and pressure conditions; p is pressure; p0 is ground pressure; T is temperature; T0 is ground temperature; γ P , γ PP , γ T , γ TT , γ PT All are fitting coefficients;

[0082] The temperature-pressure relationship equation of the drilling fluid rheology is:

[0083] f(p,T)=f(p0,T0)exp[A(T-T0)+B(p-p0)+C(T-T0)(p-p0)+D(T-T0) 2 ];

[0084] Where f(p, T) is the rheological property of the drilling fluid at temperature T and pressure p, including the apparent viscosity (μ a ) p，T , plastic viscosity (μ p ) p，T and dynamic shear force (τ0) p，T ; f(p0, T0) is the rheological property of the drilling fluid at temperature T0 and pressure p0, including the apparent viscosity of the drilling fluid at temperature T0 and pressure p0 Plastic viscosity and dynamic shear force A, B, C, and D are the rheological characteristic constants of drilling fluid;

[0085] The wellbore cleaning lifting degree equation of the drill string rotation is:

[0086]

[0087] Where, N is the speed; I q，N It indicates the relative reduction of the mass of the cuttings accumulated in the annulus when the displacement is q and the rotation speed is N, compared with the case where the drill string does not rotate; m q，0 is the mass of cuttings deposited in the annulus under the condition of displacement q and no drill string rotation; m q，N is the mass of cuttings deposited in the annulus when the displacement is q and the drill string speed is N;

[0088] The solid mass Γ entering the suspension layer from the cuttings bed per unit time and unit length based on the drill string rotation speed and displacement ent，s Correction formula is:

[0089]

[0090] In the formula, It is the corrected solid mass entering the suspended layer from the cuttings bed per unit time and unit length.

[0091] According to one aspect of the present invention, the S3 step comprises:

[0092] The extended reach well model is used for simulation. The extended reach well model is placed in a staggered grid that is evenly divided. The pressure item is arranged at the grid interface. The grid node numbers are evenly distributed along the axial direction of the horizontal well section of the extended reach well model from the bottom of the well to the wellhead. The grid node where the drill bit is located is taken as the initial node, and the initial node number is 0.

[0093] The mass conservation equation and momentum conservation equation of the extended displacement well model are discretized implicitly in the first-order upwind format.

[0094] The mass conservation equation of the suspended layer liquid phase after the implicit discretization of the first-order upwind scheme is:

[0095]

[0096] Where i is the grid node number; n is the time step number; Δt is the time interval; Δs is the interval length along the axial direction of the wellbore model;

[0097] The solid mass conservation equation of the suspended layer after the implicit discretization of the first-order upwind scheme is:

[0098]

[0099]

[0100] The mass conservation equation of the cuttings bed after the implicit discretization of the first-order upwind scheme is:

[0101]

[0102] The momentum conservation equation of the suspended layer liquid phase after the implicit discretization of the first-order upwind scheme is:

[0103]

[0104] The momentum conservation equation of the suspended layer solid phase after the implicit discretization of the first-order upwind scheme is:

[0105]

[0106] The momentum conservation equation of the cuttings bed after the implicit discretization of the first-order upwind scheme is:

[0107]

[0108] Set the initial conditions, boundary conditions and total simulation time of the extended reach well model; the initial conditions are set as:

[0109]

[0110] In the formula, Q l is the drilling fluid displacement; A a is the total cross-sectional area of ​​the annulus, p h is the static column pressure of drilling fluid at the grid node; Δp f is the friction pressure drop from the grid center along the annulus back to the ground;

[0111] It is known that the annulus node number corresponding to the drill bit is 0. All the cuttings generated by the drill bit breaking the rock at the annulus node No. 0 enter the annulus of the extended reach well model. At this time, the boundary condition is set as:

[0112]

[0113] In the formula, Q c D is the volume of rock cuttings produced per unit time when the drill bit is drilling; b is the drill diameter; v d is the mechanical drilling speed of the drill bit;

[0114] Based on the mass conservation equation and momentum conservation equation after implicit discretization of the first-order upwind format of the large-displacement well model, combined with the initial conditions and boundary conditions, the momentum conservation equation and mass conservation equation corresponding to each time step are predicted, the predicted step momentum conservation equation and the predicted step mass conservation equation are determined, and the corrected step momentum conservation equation and the corrected step mass conservation equation are obtained by correction;

[0115] Based on the SETS method, a large displacement well model is used for simulation, and the clean state of the transient large displacement well is predicted according to the prediction equation of momentum conservation, the prediction equation of mass conservation, the modified equation of momentum conservation and the modified equation of mass conservation.

[0116] According to one aspect of the present invention, based on the pressure p at the last moment n Determine the prediction speed for the n+1th time step The mass conservation equation and momentum conservation equation after the implicit discretization of the first-order upwind format of the extended reach well model are transformed into first-order linear equations, and the calculation formulas for the velocity term and shear term are determined as follows:

[0117]

[0118] in,

[0119]

[0120] v n v n+1 =v n (2v n+1 -v n );

[0121]

[0122] In the formula, β is the calculation coefficient;

[0123] The predicted step momentum conservation equations include a suspended layer solid phase momentum conservation prediction equation, a suspended layer liquid phase momentum conservation prediction equation, and a cuttings bed momentum conservation prediction equation;

[0124] The prediction equation for the conservation of solid phase momentum in the suspended layer is:

[0125]

[0126] In the formula, is the predicted value of solid phase velocity in the suspended layer; is the predicted value of the liquid phase velocity in the suspension layer; is the predicted value of the liquid-solid two-phase flow velocity in the cuttings bed;

[0127] The prediction equation for the conservation of momentum of the suspended layer liquid phase is:

[0128]

[0129] The momentum conservation prediction equation for the cuttings bed is:

[0130]

[0131] The modified step momentum conservation equation includes a modified suspended layer solid phase momentum conservation prediction equation, a modified suspended layer liquid phase momentum conservation prediction equation and a modified cuttings bed momentum conservation prediction equation;

[0132] The modified suspended layer solid phase momentum conservation prediction equation is:

[0133]

[0134] The modified prediction equation for conservation of momentum of the suspended layer liquid phase is:

[0135]

[0136]

[0137] The modified cuttings bed momentum conservation equation is:

[0138]

[0139] The prediction step mass conservation equation calculates the velocity v based on the current time step n+1 , determine the solid volume fraction at each grid node at the n+1th time step and area Including the prediction equations for the conservation of mass of the suspended layer solid phase, the prediction equations for the conservation of mass of the suspended layer liquid phase, and the prediction equations for the conservation of mass of the cuttings bed;

[0140] The suspended layer solid phase mass conservation prediction equation is:

[0141]

[0142] In the formula, is the predicted value of the cuttings concentration in the suspended layer; is the predicted value of the cross-sectional area of ​​the suspension layer; the prediction equation for the conservation of mass of the liquid phase of the suspension layer is:

[0143]

[0144] In the formula, is the predicted value of the liquid volume fraction of the suspension layer;

[0145] The cuttings bed mass conservation prediction equation is:

[0146]

[0147]

[0148] In the formula, is the predicted value of the cross-sectional area of ​​the cuttings bed;

[0149] The mass conservation equation of the correction step is based on the solid volume fraction at each grid node calculated in the current prediction step. area and speed v n+1 , determine the solid volume fraction C at each grid node in the n+1th time step n+1 and area A n+1 , including the revised prediction equation for the conservation of mass of the solid phase of the suspended layer, the revised prediction equation for the conservation of mass of the liquid phase of the suspended layer and the revised prediction equation for the conservation of mass of the cuttings bed;

[0150] The modified suspended layer solid phase mass conservation prediction equation is:

[0151]

[0152] The modified suspension layer liquid phase mass conservation prediction equation is:

[0153]

[0154] The modified cuttings bed mass conservation prediction equation is:

[0155]

[0156] According to one aspect of the present invention, the simulation is performed using the large displacement well model based on the SETS method, and the clean state of the transient large displacement well is predicted according to the prediction step momentum conservation prediction equation, the prediction step mass conservation prediction equation, the modified step momentum conservation prediction equation and the modified step mass conservation prediction equation, including:

[0157] S11. Using the extended reach well model to perform simulation, the drilling fluid density in each grid is determined according to the drilling fluid PVT equation for the pressure and temperature of each grid node in the previous time step, and the rheology of the drilling fluid in each grid is determined according to the temperature-pressure relationship equation of the rheology of the drilling fluid;

[0158] S12. Based on the calculation data of the previous time step of each grid node, determine the sedimentation velocity of the rock cuttings particles and the resuspension velocity of the rock cuttings particles, combined with the liquid mass Γ entering the rock cuttings bed from the suspension layer per unit time dep，l , the solid mass per unit time and unit length from the suspension layer into the cuttings bed layer Γ dep，s , the mass of liquid entering the suspension layer from the cuttings bed per unit time and unit length Γ ent，l and the mass of solid phase entering the suspension layer from the cuttings bed per unit time and unit length Γ ent，s , obtain liquid deposition data, solid deposition data and solid resuspension data, and make rotation speed correction based on the wellbore purification lifting degree equation of drill string rotation;

[0159] S13. Based on the pressure of each grid node in the previous time step, calculate the momentum conservation equation of the prediction step and determine the velocity at the grid node at the current time Substitute it into the modified step momentum conservation equation and get The speed v n+1 ;

[0160] S14. Set the speed v n+1 Substituting into the prediction step mass conservation equation, the calculation is determined and pressure Substitute it into the modified step momentum conservation equation to determine the current velocity v n+1 Substitute it into the modified step mass conservation equation to determine C n+1 , A n+1 and pressure

[0161] S15. Update the pressure p at each grid node, the liquid-solid two-phase flow velocity v1 in the cuttings bed, and the liquid phase flow velocity v in the suspension layer. 12 , solid phase velocity v in the suspended layer s2 and cuttings concentration;

[0162] S16. Repeat steps S11 to S15 to calculate the physical quantities to be predicted at each grid node at the next moment, the physical quantities to be predicted include the pressure p at the grid node, the liquid-solid two-phase flow velocity v1 in the cuttings bed, the liquid phase flow velocity v l2 , solid phase velocity v in the suspended layer s2 and rock cuttings particle concentration until the preset total simulation time is reached;

[0163] S17. According to the calculated physical quantities to be predicted at each grid node at each time, the suspension, deposition and resuspension of cuttings particles in the transient extended displacement well are obtained, the prediction result of the clean state of the transient extended displacement well is obtained, and a prediction diagram of the clean state of the transient extended displacement well is generated;

[0164] S18. Output the transient large-reach well cleaning status prediction diagram.

[0165] To achieve the above object, the present invention also provides a transient extended reach well cleaning state prediction system based on well temperature and drill string rotation, comprising:

[0166] The extended reach well model building module builds the extended reach well model according to the design parameters of the extended reach well, and sets the fluid type and flow rate in the horizontal annulus of the extended reach well model;

[0167] A control equation determination module establishes a mass conservation equation and a momentum conservation equation, forms a nonlinear first-order partial differential control equation group through the mass conservation equation and the momentum conservation equation, establishes an auxiliary equation, substitutes the auxiliary equation into the nonlinear first-order partial differential control equation group to form a nonlinear first-order partial differential control equation group for determining unknown variables;

[0168] The cleaning state prediction module uses the extended displacement well model for simulation. Based on the SETS method, the mass conservation equation and momentum conservation equation in the nonlinear first-order partial differential control equation group of the extended displacement well model are solved. The downhole temperature, pressure and drill string speed are comprehensively considered to simulate and calculate the momentum conservation equation and mass conservation equation corresponding to each moment and make corrections to obtain the liquid-solid two-phase flow velocity v1 in the cuttings bed and the liquid phase flow velocity v in the suspension layer at each moment. l2 , solid phase velocity v in the suspension layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore to predict the cleaning state of the transient extended reach well.

[0169] According to the scheme of the present invention, the present invention determines the suspended layer liquid phase mass conservation equation, the suspended layer solid phase mass conservation equation and the cuttings bed mass conservation equation and the suspended layer liquid phase momentum conservation equation, the suspended layer solid phase momentum conservation equation and the cuttings bed momentum conservation equation of the large displacement well model, and uses the mass conservation equations and the momentum conservation equations to jointly form a first-order partial differential control equation group, combines the mechanical equation, the drilling fluid PVT equation, the drilling fluid rheological temperature-pressure relationship equation and the wellbore purification lifting degree equation of drill string rotation, fully considers the influence of downhole pressure, downhole temperature and drill string rotation, and realizes accurate prediction of the transient large displacement well cleaning state by accurately obtaining the transient evolution law of cuttings migration during the large displacement well section drilling process, laying a foundation for guiding the safe drilling operation of the horizontal section of the large displacement well.

[0170] The present invention solves the nonlinear first-order partial differential control equations based on the SETS method, eliminates the deficiency of the traditional SIMPLE method solution process being restricted by the Courant-Friedrichs-Lewy convergence condition, increases the time step of the calculation, and the prediction step and the correction step in the simulation calculation process only need to solve the explicit equation, eliminates the iterative calculation within the time step, improves the calculation efficiency, and effectively guarantees the stability of the simulation calculation process. At the same time, the method of the present invention also fully considers the influence of downhole temperature on the rheology of the drilling fluid, the influence of the drill string rotation, and the liquid phase flow rate and solid phase flow rate in the liquid-solid two-phase flow in different areas of the annulus, ensures the authenticity of the large displacement well model simulation process, improves the accuracy of the prediction of the downhole wellbore cleaning state, and is of great significance for the study of the cleaning state of high-angle wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0171] Figure 1 A flowchart schematically showing a method for predicting the cleaning state of a transient extended reach well based on well temperature and drill string rotation according to an embodiment of the present invention;

[0172] Figure 2 A cross-sectional view schematically showing a horizontal section of an extended reach well model according to an embodiment of the present invention;

[0173] Figure 3 An axial diagram schematically showing a horizontal section of an extended reach well model according to an embodiment of the present invention;

[0174] Figure 4 A diagram schematically showing staggered grid division according to one embodiment of the present invention;

[0175] Figure 5 This is a transient large-displacement well cleaning status prediction diagram of Example 1. DETAILED DESCRIPTION

[0176] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only to enable those skilled in the art to better understand and thus implement the present invention, rather than implying any limitation on the scope of the present invention.

[0177] As used herein, the term “including” and variations thereof are to be interpreted as open-ended terms meaning “including, but not limited to.” The term “based on” is to be interpreted as “based, at least in part, on.” The terms “one embodiment” and “an embodiment” are to be interpreted as “at least one embodiment.”

[0178] Figure 1 The flowchart schematically shows a method for predicting the cleaning state of a transient extended reach well based on well temperature and drill string rotation according to an embodiment of the present invention. Figure 1 As shown, in this embodiment, the transient extended reach well cleaning state prediction method based on well temperature and drill string rotation includes:

[0179] S1. construct an extended reach well model according to the design parameters of the extended reach well, and set the fluid type and flow rate in the horizontal annulus of the extended reach well model;

[0180] S2. Establishing a mass conservation equation and a momentum conservation equation, forming a nonlinear first-order partial differential control equation group through the mass conservation equation and the momentum conservation equation, establishing an auxiliary equation, substituting the auxiliary equation into the nonlinear first-order partial differential control equation group to form a nonlinear first-order partial differential control equation group for determining unknown variables;

[0181] S3. Using the extended displacement well model for simulation, the mass conservation equation and momentum conservation equation in the nonlinear first-order partial differential control equation group of the extended displacement well model are solved based on the SETS method. The downhole temperature, pressure and drill string speed are combined to simulate and calculate the momentum conservation equation and mass conservation equation corresponding to each moment and make corrections to obtain the liquid-solid two-phase flow velocity v1 in the cuttings bed and the liquid phase flow velocity v in the suspension layer at each moment. l2 , solid phase velocity v in the suspended layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore to predict the cleaning state of the transient extended reach well.

[0182] Further, according to an embodiment of the present invention, an extended reach well model is constructed according to the design parameters of the extended reach well, and the fluid type and flow rate in the horizontal annulus in the extended reach well model are set, including:

[0183] According to the design parameters of the extended reach well, the well inclination angle φ and the wellbore diameter D of the extended reach well are obtained. h 、Drill string outer diameter D p and drill string eccentricity s;

[0184] The extended reach well model is constructed according to the design parameters of the extended reach well, such as Figure 2 and Figure 3 As shown, the extended reach well model includes a wellbore model 1 and a drill string model 2. The drill string model is connected to a drill bit. The entire extended reach well model is divided into a vertical section, a deflection section, and an inclined section. The drill string model is arranged in the wellbore model according to the eccentricity. The space between the drill string model and the wellbore model forms a horizontal annulus 3.

[0185] The fluid in the horizontal annulus is provided with a liquid-solid two-phase flow, which is a mixture of drilling fluid and rock cuttings particles; the upper space of the horizontal annulus is suspended with rock cuttings particles to form a suspended layer, and the lower space of the horizontal annulus is evenly piled with settled rock cuttings particles to form a rock cuttings bed;

[0186] The flow velocities of the liquid phase and the solid phase in the suspension layer are different. The flow velocity of the liquid phase in the suspension layer is set to v l2 , solid phase flow rate is v s2 The cross-sectional area of ​​the suspension layer is A2, and the wetted perimeter of the suspension layer in contact with the inner wall of the wellbore model is L 2,out , the wetted perimeter of the suspended layer and the drill string model L 2，in , the concentration of rock debris in the suspension layer is C s2 ;

[0187] The flow velocities of the liquid and solid phases in the cuttings bed are the same. The liquid and solid flow rates in the cuttings bed are equal to the liquid-solid two-phase flow velocity v1 in the cuttings bed. The height of the cuttings bed is h, the cross-sectional area is A1, and the wetted perimeter of the cuttings bed in contact with the inner wall of the wellbore model is L.1,out The contact wetted perimeter between the cuttings bed and the drill string model is L 1，in , the cuttings concentration in the cuttings bed is C s1 .

[0188] In this embodiment, the liquid-solid two-phase flow composed of drilling fluid and cuttings particles in the extended reach well model is transient flow, and the cuttings concentration C in the cuttings bed is s1 The average flow velocity of the liquid-solid two-phase flow in the suspension layer is greater than the movement velocity of the cuttings bed. The well pressure is only related to the axial depth of the large displacement well model. The pressure increases along the well depth, and the drilling fluid density in the horizontal annulus is affected by the downhole pressure and downhole temperature and changes along the well depth.

[0189] Further, according to an embodiment of the present invention, in the above step S2, the mass conservation equation includes the suspended layer liquid phase mass conservation equation, the suspended layer solid phase mass conservation equation and the cuttings bed mass conservation equation, and the momentum conservation equation includes the suspended layer liquid phase momentum conservation equation, the suspended layer solid phase momentum conservation equation and the cuttings bed momentum conservation equation;

[0190] The auxiliary equations include mechanical equations, drilling fluid PVT equations, drilling fluid rheological temperature-pressure relationship equations, and wellbore purification and lifting degree equations for drill string rotation;

[0191] The mechanical equations are used to determine the shear stress τ2 between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model, and the shear stress τ between the suspension layer and the cuttings bed interface. 12 , the drag force F between the solid and liquid phases in the suspension layer sf , the shear stress τ1 between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model, the dry friction resistance F1 between the solid phase in the cuttings bed per unit length and the inner wall of the wellbore model and the outer wall of the drill string model, and the sedimentation velocity v of the cuttings particles dep , rock debris particle resuspension velocity v ent ;

[0192] After substituting the auxiliary equation into the nonlinear first-order partial differential control equation group, it is determined that the unknown variables in the nonlinear first-order partial differential control equation group include: the liquid-solid two-phase flow velocity v1 in the cuttings bed, the liquid phase flow velocity v in the suspension layer l2 , solid phase velocity v in the suspension layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore.

[0193] Furthermore, in this embodiment, the mass conservation equation of the suspension layer liquid phase is:

[0194]

[0195] In the formula, t is time; s is the well depth direction; C l2 is the liquid volume fraction of the suspension layer; A2 is the cross-sectional area of ​​the suspension layer; ρ l is the drilling fluid density, in kg / m 3 ; γ 12 is the liquid phase flow rate in the suspension layer; Γ ent，l is the solid mass entering the cuttings bed from the suspension layer per unit time and unit length, in kg / s / m; Γ dep，l is the mass of liquid entering the cuttings bed from the suspension layer per unit time, in kg / s / m;

[0196] The mass conservation equation of the suspended layer solid phase is:

[0197]

[0198] In the formula, C s2 is the concentration of rock debris in the suspended layer; ρ s is the rock cuttings density, in kg / m 3 ;v s2 is the solid phase flow rate in the suspension layer; Γ ent，s is the mass of solid phase entering the suspension layer from the cuttings bed per unit time and unit length, in kg / s / m; Γ dep，s is the mass of solid phase entering the cuttings bed from the suspension layer per unit time and unit length, in kg / s / m;

[0199] The mass conservation equation of the cuttings bed is:

[0200]

[0201] Where A1 is the cross-sectional area of ​​the cuttings bed, D h is the borehole diameter, θ h is the angle between the top surface of the outer wall of the cuttings bed and the center of the wellbore model, D p is the outer diameter of the drill string, θ p is the angle between the top surface of the inner wall of the cuttings bed and the center of the drill string model; ρ1 is the density of the mixture in the cuttings bed, in kg / m 3 ,ρ1=C s2 ρ s +(1-C s2 )ρ1, where C s2 +C 12 =1; v1 is the liquid-solid two-phase flow velocity in the cuttings bed;

[0202] In the formula, Γ dep，l and Γ dep，s They are:

[0203]

[0204] In the formula, C s1 is the cuttings concentration in the cuttings bed, C l1 is the liquid volume fraction of the cuttings bed, C s1 +C l1 =1;L 12 is the contact length, L 12 =D h sinθ h -D p sinθ p ;v dep is the sedimentation velocity of rock debris particles, in m / s;

[0205] In the formula, Γ ent， l and Γ dep，s They are:

[0206] Γ ent，1 =C l1 ρ1L 12 v ent ;

[0207] Γ ent，s =C s1 ρ s L 12 v ent ;

[0208] In the formula, v ent is the resuspension velocity of rock cuttings particles, in m / s;

[0209] The momentum conservation equation of the suspended layer liquid phase is:

[0210] Where g is the gravitational acceleration; φ is the well inclination angle; L2 is the contact length between the suspension layer and the inner wall of the wellbore model and the drill string model, L2 = L 2，in +L 2，out =Π(D h +D p )-L1; L1 is the contact length between the cuttings bed and the inner wall of the wellbore model and the drill string model, L1=L 1，in +L 1，out =D h θ h +D p θ p ; τ2 is the shear stress between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model; F sf is the drag force between the solid and liquid phases in the suspension layer;

[0211] The momentum conservation equation of the suspended layer solid phase is:

[0212] In the formula, τ 12 is the shear stress between the interface of the suspended layer and the cuttings bed;

[0213] The momentum conservation equation for the cuttings bed is:

[0214]

[0215] Where τ1 is the shear stress between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model, and F is the dry friction resistance between the solid phase in the cuttings bed per unit length and the inner wall of the wellbore model and the outer wall of the drill string model.

[0216] Further, in this embodiment, in the mechanical equation, the shear stress τ2 between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model is:

[0217]

[0218] in,

[0219]

[0220] Where f2 is the friction coefficient of the suspension layer; Re2 is the Reynolds number of the suspension layer; D2 is the hydraulic diameter of the suspension layer, M is the fluidity index, k is the liquid phase consistency coefficient;

[0221] Shear stress τ between the suspended layer and the cuttings bed interface 12 for:

[0222]

[0223] in,

[0224]

[0225] In the formula, f 12 is the interfacial friction coefficient between the suspension layer and the cuttings bed; Re 12 is the Reynolds number between the suspension layer and the cuttings bed interface; d c is the diameter of the cuttings;

[0226] The drag force F between the solid and liquid phases in the suspension layer sf for:

[0227]

[0228] in,

[0229]

[0230] In the formula, C D is the drag coefficient; Re p is the particle Reynolds number;

[0231] The shear stress τ1 between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model is:

[0232]

[0233] in,

[0234]

[0235] Where f1 is the friction coefficient of the cuttings bed; Re1 is the Reynolds number of the cuttings bed; D1 is the hydraulic diameter of the cuttings bed, μ1 is the consistency coefficient of the cuttings bed mixture, which is determined by correcting the liquid phase consistency coefficient k according to the cuttings concentration of the cuttings bed;

[0236] The dry friction resistance F between the solid phase in the unit length of the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model is:

[0237]

[0238] Where η is the dry friction coefficient;

[0239] Rock cuttings particle settling velocity v dep for:

[0240] v dep =(1-C s2 ) m v p ;

[0241] in,

[0242]

[0243]

[0244] Where m is the sedimentation velocity constant; Re dep is the particle Reynolds number when the cuttings particles are settling; v p is the settling velocity of a single rock cutting particle;

[0245] The resuspension velocity of the cuttings particles from the cuttings bed to the suspension layer is assumed to be a linear relationship between the friction velocities of the two layers, and the resuspension velocity v of the cuttings particles is determined. ent for:

[0246]

[0247] in,

[0248]

[0249] In the formula, m ent is the resuspension coefficient of rock debris particles; v 12 is the friction speed; is the critical friction velocity; α is the repose angle of the cuttings bed, which is 35°; C′ D is the drag force coefficient based on friction speed, and its value is 0.4.

[0250] Further, in this embodiment, the drilling fluid PVT equation is:

[0251] ρ l =ρ l0 e Γ(p，T) ;

[0252] in,

[0253] Γ(p, T) = γ P (p-p0)+γ PP (p-p0) 2 +γ T (T-T0)+γ TT (T-T0) 2 +γ PT (p-p0)(T-T0);

[0254] In the formula, ρ 10 is the density of drilling fluid under ground temperature and pressure conditions; p is pressure, in Pa; p0 is ground pressure, in Pa; T is temperature, in °C; T0 is ground temperature, in °C; γ P , γ PP 、V T , γT T , γ PT All are fitting coefficients;

[0255] In this embodiment, the fitting coefficient V P , γ PP 、V T , γT T , γ PT All of them are obtained by fitting the experimental data, and the drilling fluid PVT characteristic relationship model coefficients are shown in Table 1.

[0256]

[0257] Table 1

[0258] The temperature-pressure relationship equation of drilling fluid rheology is:

[0259] f(p,T)=f(p0,T0)ex p[A(T-T0)+B(p-p0)+C(T-T0)(p-p0)+D(T-T0) 2 ];

[0260] Where f(p, T) is the rheological property of the drilling fluid at temperature T and pressure p, including the apparent viscosity (μ a ) p，T , plastic viscosity (μ p ) p，T and dynamic shear force (τ0) p，T , where the apparent viscosity (μ a ) p，T The unit is mPa·s, plastic viscosity (μ p ) p，T The unit is mPa·s, dynamic shear force (τ0) p，T The unit is Pa; f(p0, T0) is the rheological property of the drilling fluid at temperature T0 and pressure p0, including the apparent viscosity of the drilling fluid at temperature T0 and pressure p0. Plastic viscosity and dynamic shear force Among them, the apparent viscosity The unit is mPa·s, plastic viscosity The unit is mPa·s, dynamic shear force The unit is Pa; A, B, C, and D are the rheological characteristic constants of the drilling fluid.

[0261] In this embodiment, the drilling fluid rheological characteristic constants A, B, C, and D are shown in Table 2 below.

[0262]

[0263]

[0264] Table 2

[0265] The equation for the wellbore cleaning efficiency of drill string rotation is:

[0266]

[0267] Where, N is the speed, in rpm; lq, N It indicates the relative reduction of the mass of the cuttings accumulated in the annulus when the displacement is q and the rotation speed is N, compared with the case where the drill string does not rotate; m q，0 is the mass of cuttings deposited in the annulus under the condition of displacement q and non-rotation of drill string, in kg; mq, N is the mass of cuttings deposited in the annulus when the displacement is q and the drill string speed is N, in kg;

[0268] The solid mass Γ entering the suspension layer from the cuttings bed per unit time and unit length based on the drill string rotation speed and displacement ent，s Correction formula is:

[0269]

[0270] In the formula, is the corrected solid mass entering the suspension layer from the cuttings bed per unit time and per unit length. Furthermore, according to one embodiment of the present invention, a large displacement well model is used for simulation. In order to improve the calculation speed and stability of the nonlinear first-order partial differential control equation group, the mass conservation equation and momentum conservation equation of the large displacement well model are solved based on the SETS (Stability Enhancing Two Step method). The downhole temperature, pressure and drill string speed are comprehensively considered to simulate and calculate the momentum conservation equation and mass conservation equation corresponding to each moment and make corrections to obtain the liquid-solid two-phase flow velocity v1 in the cuttings bed and the liquid phase flow velocity v in the suspension layer at each moment. l2 , solid phase velocity v in the suspension layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore to predict the cleaning state of the transient extended reach well.

[0271] Specifically, in this embodiment, the above step S3 includes:

[0272] The extended reach well model is used for simulation. The extended reach well model is placed in a uniformly divided staggered grid. The pressure term is arranged at the grid interface. The grid node numbers are uniformly distributed along the axial direction of the horizontal well section of the extended reach well model from the bottom of the well to the wellhead. The grid node where the drill bit is located is taken as the initial node, and the initial node number is 0, such as Figure 4 As shown;

[0273] The mass conservation equation and momentum conservation equation of the extended displacement well model are discretized implicitly in the first-order upwind format.

[0274] The mass conservation equation of the suspended layer liquid phase after the implicit discretization of the first-order upwind scheme is:

[0275]

[0276] Where i is the grid node number; n is the time step number; Δt is the time interval; Δs is the interval length along the axial direction of the wellbore model;

[0277] The solid mass conservation equation of the suspended layer after the implicit discretization of the first-order upwind scheme is:

[0278]

[0279] The mass conservation equation of the cuttings bed after the implicit discretization of the first-order upwind scheme is:

[0280]

[0281] The momentum conservation equation of the suspended layer liquid phase after the implicit discretization of the first-order upwind scheme is:

[0282]

[0283]

[0284] The momentum conservation equation of the suspended layer solid phase after the implicit discretization of the first-order upwind scheme is:

[0285]

[0286] The momentum conservation equation of the cuttings bed after the implicit discretization of the first-order upwind scheme is:

[0287]

[0288] Set the initial conditions, boundary conditions and total simulation time of the extended reach well model, and determine the interval between each time step during the simulation process;

[0289] The initial conditions are set as:

[0290]

[0291] In the formula, Q l is the drilling fluid displacement, in m 3 / s; A a is the total cross-sectional area of ​​the annulus, ph is the static column pressure of the drilling fluid at the grid node, in Pa; Δp f is the friction pressure drop from the center of the grid along the annulus to the ground, in Pa;

[0292] It is known that the annulus node number corresponding to the drill bit is 0. All the cuttings generated by the drill bit breaking the rock at the annulus node No. 0 enter the annulus of the extended reach well model. At this time, the boundary condition is set as:

[0293]

[0294] In the formula, Q c The volume of rock cuttings produced per unit time when the drill bit is drilling, in m 3 ;D b is the drill bit diameter, in m; v d is the mechanical drilling speed of the drill bit, in m / s;

[0295] Based on the mass conservation equation and momentum conservation equation after implicit discretization of the first-order upwind format of the large-displacement well model, combined with the initial conditions and boundary conditions, the momentum conservation equation and mass conservation equation corresponding to each time step are predicted, the predicted step momentum conservation equation and the predicted step mass conservation equation are determined, and the corrected step momentum conservation equation and the corrected step mass conservation equation are obtained by correction;

[0296] Based on the SETS method, a large displacement well model is used for simulation, and the clean state of the transient large displacement well is predicted according to the prediction equation of momentum conservation, the prediction equation of mass conservation, the modified equation of momentum conservation and the modified equation of mass conservation.

[0297] Furthermore, in this embodiment, the prediction step momentum conservation equation is based on the pressure p at the previous moment n Determine the prediction speed for the n+1th time step The mass conservation equation and momentum conservation equation after the implicit discretization of the first-order upwind format of the extended reach well model are transformed into first-order linear equations, and the calculation formulas for the velocity term and shear term are determined as follows:

[0298]

[0299] in,

[0300]

[0301] v n v n+1 =v n (2v n+1 -v n );

[0302]

[0303]

[0304] In the formula, β is the calculation coefficient;

[0305] The momentum conservation equations of the prediction step include the momentum conservation prediction equations of the solid phase of the suspended layer, the momentum conservation prediction equations of the liquid phase of the suspended layer, and the momentum conservation prediction equations of the cuttings bed;

[0306] The prediction equation for the conservation of solid phase momentum in the suspended layer is:

[0307]

[0308] In the formula, is the predicted value of solid phase velocity in the suspended layer; is the predicted value of the liquid phase velocity in the suspension layer; is the predicted value of the liquid-solid two-phase flow velocity in the cuttings bed;

[0309] The prediction equation for the conservation of momentum of the suspended layer liquid phase is:

[0310]

[0311] The momentum conservation prediction equation for cuttings bed is:

[0312]

[0313] The momentum conservation equation of the correction step is substituted into the prediction step to obtain After that, get The speed v n+1 , the modified step momentum conservation equation includes the modified suspended layer solid phase momentum conservation prediction equation, the modified suspended layer liquid phase momentum conservation prediction equation and the modified cuttings bed momentum conservation prediction equation;

[0314] The corrected prediction equation for the conservation of solid phase momentum in the suspended layer is:

[0315]

[0316] The corrected prediction equation for the conservation of momentum of the suspended layer liquid phase is:

[0317]

[0318] The revised momentum conservation equation of cuttings bed is:

[0319]

[0320] The prediction step mass conservation equation calculates the velocity v based on the current time step n+1 , determine the solid volume fraction at each grid node at the n+1th time step and area Including the prediction equations for the conservation of mass of the suspended layer solid phase, the prediction equations for the conservation of mass of the suspended layer liquid phase, and the prediction equations for the conservation of mass of the cuttings bed;

[0321] The prediction equation for the conservation of solid mass in the suspended layer is:

[0322]

[0323] In the formula, is the predicted value of the cuttings concentration in the suspended layer; is the predicted value of the cross-sectional area of ​​the suspension layer; the prediction equation for the conservation of mass of the liquid phase in the suspension layer is:

[0324]

[0325] In the formula, is the predicted value of the liquid volume fraction of the suspension layer;

[0326] The prediction equation for the mass conservation of the cuttings bed is:

[0327]

[0328] In the formula, is the predicted value of the cross-sectional area of ​​the cuttings bed;

[0329] The mass conservation equations of the modified step are based on the solid volume fraction at each grid node calculated in the current prediction step. area and speed v n+1 , determine the solid volume fraction C at each grid node in the n+1th time step n+1 and area A n+1 , including the revised prediction equation for the conservation of mass of the solid phase of the suspended layer, the revised prediction equation for the conservation of mass of the liquid phase of the suspended layer and the revised prediction equation for the conservation of mass of the cuttings bed;

[0330] The corrected prediction equation for the conservation of suspended layer solid mass is:

[0331]

[0332] The corrected prediction equation for the mass conservation of the suspended layer liquid phase is:

[0333]

[0334] The revised prediction equation for the mass conservation of cuttings bed is:

[0335]

[0336] Further, in this embodiment, the SETS method is used to perform simulation using the large-reach well model, and the clean state of the transient large-reach well is predicted according to the prediction step momentum conservation prediction equation, the prediction step mass conservation prediction equation, the modified step momentum conservation prediction equation, and the modified step mass conservation prediction equation, including:

[0337] S11. Using the extended reach well model to perform simulation, the drilling fluid density in each grid is determined according to the drilling fluid PVT equation for the pressure and temperature of each grid node in the previous time step, and the rheology of the drilling fluid in each grid is determined according to the temperature-pressure relationship equation of the rheology of the drilling fluid;

[0338] S12. Determine the rock cuttings particle settling velocity v based on the calculation data of each grid node in the previous time step dep and the rock debris resuspension velocity v ent , combined with the mass of liquid entering the cuttings bed from the suspension layer per unit time Γ dep，1 , the solid mass per unit time and unit length from the suspension layer into the cuttings bed layer Γ dep，s, the mass of liquid entering the suspension layer from the cuttings bed per unit time and unit length Γ ent，l and the mass of solid phase entering the suspension layer from the cuttings bed per unit time and unit length Γ ent，s , obtain liquid deposition data, solid deposition data and solid resuspension data, and make rotation speed correction based on the wellbore purification lifting degree equation of drill string rotation;

[0339] S13. Based on the pressure of each grid node in the previous time step, calculate the momentum conservation equation of the prediction step (including the momentum conservation prediction equation of the solid phase of the suspended layer, the momentum conservation prediction equation of the liquid phase of the suspended layer and the momentum conservation prediction equation of the cuttings bed layer), and determine the velocity at the grid node at the current moment Substitute it into the modified step momentum conservation equation (including the modified suspended layer solid phase momentum conservation prediction equation, the modified suspended layer liquid phase momentum conservation prediction equation and the modified cuttings bed momentum conservation equation), and get The speed v n+1 ;

[0340] S14. Set the speed v n+1 Substituting into the mass conservation equation of the prediction step (including the solid mass conservation prediction equation of the suspended layer, the liquid mass conservation prediction equation of the suspended layer and the mass conservation prediction equation of the cuttings bed), the calculation is determined and pressure Substitute it into the modified step momentum conservation equation (including the modified suspended layer solid phase momentum conservation prediction equation, the modified suspended layer liquid phase momentum conservation prediction equation and the modified cuttings bed momentum conservation equation) to determine the current velocity v n+1 Substitute it into the modified step mass conservation equation (including the modified suspended layer solid phase mass conservation prediction equation, the modified suspended layer liquid phase mass conservation prediction equation and the modified cuttings bed mass conservation prediction equation) to determine C n+1 , A n+1 and pressure

[0341] S15. Update the pressure p at each grid node, the liquid-solid two-phase flow velocity v1 in the cuttings bed, and the liquid phase flow velocity v in the suspension layer. l2 , solid phase velocity v in the suspended layer s2 and cuttings concentration;

[0342] S16. Repeat steps S11 to S15 to calculate the physical quantities to be predicted at each grid node at the next moment, the physical quantities to be predicted include the pressure p at the grid node, the liquid-solid two-phase flow velocity v1 in the cuttings bed, the liquid phase flow velocity v l2 , solid phase velocity v in the suspended layer s2 and rock cuttings particle concentration until the preset total simulation time is reached;

[0343] S17. According to the calculated physical quantities to be predicted at each grid node at each time, the suspension, deposition and resuspension of cuttings particles in the transient extended displacement well are obtained, the prediction result of the clean state of the transient extended displacement well is obtained, and a prediction diagram of the clean state of the transient extended displacement well is generated;

[0344] S18. Output the transient large-reach well cleaning status prediction diagram.

[0345] According to the above scheme of the present invention, the present invention determines the suspended layer liquid phase mass conservation equation, the suspended layer solid phase mass conservation equation and the cuttings bed mass conservation equation and the suspended layer liquid phase momentum conservation equation, the suspended layer solid phase momentum conservation equation and the cuttings bed momentum conservation equation of the large displacement well model, and uses the mass conservation equations and the momentum conservation equations to jointly form a first-order partial differential control equation group, combines the mechanical equation, the drilling fluid PVT equation, the drilling fluid rheological temperature-pressure relationship equation and the wellbore purification lifting degree equation of drill string rotation, fully considers the influence of downhole pressure, downhole temperature and drill string rotation, and realizes accurate prediction of the transient large displacement well cleaning state by accurately obtaining the transient evolution law of cuttings migration during the large displacement well section drilling process, laying a foundation for guiding the safe drilling operation of the horizontal section of the large displacement well.

[0346] The present invention solves the nonlinear first-order partial differential control equations based on the SETS method, eliminates the deficiency of the traditional SIMPLE method solution process being restricted by the Courant-Friedrichs-Lewy convergence condition, increases the time step of the calculation, and the prediction step and the correction step in the simulation calculation process only need to solve the explicit equation, eliminates the iterative calculation within the time step, improves the calculation efficiency, and effectively guarantees the stability of the simulation calculation process. At the same time, the method of the present invention also fully considers the influence of downhole temperature on the rheology of the drilling fluid, the influence of the drill string rotation, and the liquid phase flow rate and solid phase flow rate in the liquid-solid two-phase flow in different areas of the annulus, ensures the authenticity of the large displacement well model simulation process, improves the accuracy of the prediction of the downhole wellbore cleaning state, and is of great significance for the study of the cleaning state of high-angle wells.

[0347] Furthermore, to achieve the above-mentioned purpose, the present invention also provides a transient extended reach well cleaning state prediction system based on well temperature and drill string rotation, comprising:

[0348] The extended reach well model building module builds the extended reach well model according to the design parameters of the extended reach well, and sets the fluid type and flow rate in the horizontal annulus of the extended reach well model;

[0349] A control equation determination module establishes a mass conservation equation and a momentum conservation equation, forms a nonlinear first-order partial differential control equation group through the mass conservation equation and the momentum conservation equation, establishes an auxiliary equation, substitutes the auxiliary equation into the nonlinear first-order partial differential control equation group to form a nonlinear first-order partial differential control equation group for determining unknown variables;

[0350] The cleaning state prediction module uses the extended displacement well model for simulation. Based on the SETS method, the mass conservation equation and momentum conservation equation in the nonlinear first-order partial differential control equation group of the extended displacement well model are solved. The downhole temperature, pressure and drill string speed are comprehensively considered to simulate and calculate the momentum conservation equation and mass conservation equation corresponding to each moment and make corrections to obtain the liquid-solid two-phase flow velocity v1 in the cuttings bed and the liquid phase flow velocity v in the suspension layer at each moment. l2 , solid phase velocity v in the suspension layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore to predict the cleaning state of the transient extended reach well.

[0351] The transient extended reach well cleaning state prediction system based on well temperature and drill string rotation according to the present invention can realize the above-mentioned transient extended reach well cleaning state prediction method based on well temperature and drill string rotation. The specific process steps are as described above and will not be repeated here.

[0352] Based on the above solution of the present invention, the solution of the present invention is verified in the form of a specific embodiment in combination with the accompanying drawings.

[0353] Example 1

[0354] In this embodiment, the above-mentioned transient extended reach well cleaning state prediction method based on well temperature and drill string rotation is applied to the extended reach well X.

[0355] In this embodiment, the total depth of the extended reach well X is 1345 meters, the ratio between the horizontal displacement and the vertical depth is 1.46, and during the drilling process of the 1099m-1345m well section, the average mechanical drilling speed is 13.7m / h, the drill string speed is 40rpm, the displacement is 1976L / min, and the drilling fluid density is 1170kg / m 3 The drilling fluid fluidity index is 0.58, the drilling fluid viscosity coefficient is 0.52Pa.sn, and the cuttings density is 2400kg / m 3 , the rock chip size is 3.2mm.

[0356] The transient extended-reach well cleaning state prediction method based on well temperature and drill string rotation proposed in this invention is applied. During the simulation calculation, the grid distance of the staggered grid is set to 27m, divided into 122 grids in total, and the time step is set to 60s. The local geometric size changes of the tool joint, stabilizer or joint are ignored, and the drill string eccentricity ε is considered in each well section.

[0357] Set the drill string eccentricity ε for different well sections:

[0358]

[0359] In the formula, ε max is the maximum drill string eccentricity, D j is the outer diameter of the drill pipe joint, in meters.

[0360] The transient extended reach well cleaning state prediction method based on well temperature and drill string rotation proposed in the present invention is used for simulation, and the cuttings bed height evolution law during the drilling of the 1099m-1345m well section of the extended reach well model is simulated, and the cuttings bed height transient simulation results are obtained, that is, the transient extended reach well cleaning state prediction diagram, as shown in FIG. Figure 5 As shown, it was compared with the on-site operation conditions during the actual drilling operation of this section of the well. After comparison, it was found that the rock cuttings were seriously accumulated during the drilling operation of this section of the well, and the phenomenon of back-marking and pump blocking occurred many times on site, thereby verifying the consistency between the simulation results of the method of the present invention and the on-site operation.

[0361] Those skilled in the art will appreciate that the modules and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0362] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices and equipment can refer to the corresponding processes in the aforementioned method implementation methods, and will not be repeated here.

[0363] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0364] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the embodiments of the present invention.

[0365] In addition, each functional module in the embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0366] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the energy-saving signal sending / receiving method of each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, ROM, RAM, magnetic disks, or optical disks.

[0367] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

[0368] It should be understood that the size of the serial numbers of each step in the content of the invention and the implementation methods of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation methods of the present invention.

Claims

1. A transient extended reach well cleaning state prediction method based on well temperature and drill string rotation, characterized in that: include: S1. construct an extended reach well model according to the design parameters of the extended reach well, and set the fluid type and flow rate in the horizontal annulus of the extended reach well model; S2. Establishing a mass conservation equation and a momentum conservation equation, forming a nonlinear first-order partial differential control equation group through the mass conservation equation and the momentum conservation equation, establishing an auxiliary equation, substituting the auxiliary equation into the nonlinear first-order partial differential control equation group to form a nonlinear first-order partial differential control equation group for determining unknown variables; S3. Using the extended displacement well model for simulation, the mass conservation equations and momentum conservation equations in the nonlinear first-order partial differential control equations of the extended displacement well model are solved based on the SETS method. The downhole temperature, pressure and drill string speed are combined to simulate and calculate the momentum conservation equations and mass conservation equations corresponding to each moment and make corrections to obtain the liquid-solid two-phase flow velocity v1 in the cuttings bed and the liquid phase flow velocity v in the suspension layer at each moment. l2 , solid phase velocity v in the suspension layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore to predict the cleaning state of the transient extended reach well.

2. The method for predicting the cleaning status of a transient extended reach well based on well temperature and drill string rotation according to claim 1, characterized in that: The method of constructing an extended reach well model according to the design parameters of the extended reach well and setting the fluid type and flow rate in the horizontal annulus of the extended reach well model includes: According to the design parameters of the extended reach well, the well inclination angle φ and the wellbore diameter D of the extended reach well are obtained. h 、Drill string outer diameter D p and drill string eccentricity s; An extended reach well model is constructed according to the design parameters of the extended reach well, wherein the extended reach well model includes a wellbore model and a drill string model, the drill string model is connected to a drill bit, and the entire extended reach well model is divided into a vertical section, a deflection section, and an inclined section. The drill string model is arranged in the wellbore model according to the eccentricity, and the space between the drill string model and the wellbore model forms a horizontal annulus; The fluid in the horizontal annulus is provided with a liquid-solid two-phase flow, and the liquid-solid two-phase flow is formed by a mixture of drilling fluid and rock cuttings particles; the upper space of the horizontal annulus is suspended with rock cuttings particles to form a suspended layer, and the lower space of the horizontal annulus is evenly piled with settled rock cuttings particles to form a rock cuttings bed; The flow speeds of the liquid phase and the solid phase in the suspension layer are different. The flow speed of the liquid phase in the suspension layer is set to v l2 , solid phase flow rate is v s2 The cross-sectional area of ​​the suspension layer is A2, and the wetted perimeter of the suspension layer in contact with the inner wall of the wellbore model is L 2,out , the wetted perimeter of the suspended layer and the drill string model L 2,in , the concentration of rock debris in the suspension layer is C s2 ; The flow velocities of the liquid phase and the solid phase in the cuttings bed are the same. The liquid phase flow velocity and the solid phase flow velocity in the cuttings bed are equal to the liquid-solid two-phase flow velocity v1 in the cuttings bed. The height of the cuttings bed is h, the cross-sectional area is A1, and the wetted perimeter of the cuttings bed in contact with the inner wall of the wellbore model is L. 1,out The contact wet perimeter between the cuttings bed and the drill string model is L 1,in , the cuttings concentration in the cuttings bed is C s1 .

3. The method for predicting the cleaning status of a transient extended reach well based on well temperature and drill string rotation according to claim 2 is characterized in that: The mass conservation equation includes the suspended layer liquid phase mass conservation equation, the suspended layer solid phase mass conservation equation and the cuttings bed mass conservation equation, and the momentum conservation equation includes the suspended layer liquid phase momentum conservation equation, the suspended layer solid phase momentum conservation equation and the cuttings bed momentum conservation equation; The auxiliary equations include mechanical equations, drilling fluid PVT equations, drilling fluid rheological temperature-pressure relationship equations, and wellbore purification and lifting degree equations for drill string rotation; The mechanical equation is used to determine the shear stress τ2 between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model, the shear stress τ between the suspension layer and the cuttings bed interface l2 , the drag force F between the solid and liquid phases in the suspension layer sf , the shear stress τ between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model l , the dry friction resistance F between the solid phase in the cuttings bed per unit length and the inner wall of the wellbore model and the outer wall of the drill string model l , rock cuttings particle settling velocity v dep , rock debris particle resuspension velocity v ent ; After substituting the auxiliary equation into the nonlinear first-order partial differential control equation group, it is determined that the unknown variables in the nonlinear first-order partial differential control equation group include: the liquid-solid two-phase flow velocity v1 in the cuttings bed, the liquid phase flow velocity v in the suspension layer l2 , solid phase velocity v in the suspension layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore.

4. The method for predicting the cleaning status of a transient extended reach well based on well temperature and drill string rotation according to claim 3 is characterized in that: The mass conservation equation of the suspended layer liquid phase is: In the formula, t is time; s is the well depth direction; C l2 is the liquid volume fraction of the suspension layer; A2 is the cross-sectional area of ​​the suspension layer; ρ l is the drilling fluid density; v l2 is the liquid phase flow rate in the suspension layer; Γ ent,l is the solid mass entering the cuttings bed from the suspension layer per unit time and unit length; Γ dep,l is the mass of liquid entering the cuttings bed from the suspension layer per unit time; The solid mass conservation equation of the suspended layer is: In the formula, C s2 is the concentration of rock debris in the suspended layer; ρ s is the rock cuttings density; v s2 is the solid phase flow rate in the suspension layer; Γ ent,s is the solid mass entering the suspension layer from the cuttings bed per unit time and unit length; Γ dep,s is the mass of solid phase entering the cuttings bed from the suspension layer per unit time and unit length; The mass conservation equation of the cuttings bed is: Where A1 is the cross-sectional area of ​​the cuttings bed, D h is the borehole diameter, θ h is the angle between the top surface of the outer wall of the cuttings bed and the center of the wellbore model, D p is the outer diameter of the drill string, θ p is the angle between the top surface of the inner wall of the cuttings bed and the center of the drill string model; ρ1 is the density of the mixture in the cuttings bed, ρ1 = C s2 ρ s +(1-C s2 )ρ l , where C s2 +C l2 =1; v1 is the liquid-solid two-phase flow velocity in the cuttings bed; In the formula, Γ dep,l and Γ dep,s They are: In the formula, C s1 is the cuttings concentration in the cuttings bed, C l1 is the liquid volume fraction of the cuttings bed, C s1 +C l1 =1;L l2 is the contact length, L l2 =D h sinθ h -D p sinθ p ;v dep is the deposition rate of rock debris particles; In the formula, Γ ent,1 and Γd ep , s They are: C ent,l =C l1 r l L l2 v ent ; C ent,s =C s1 r s L l2 v ent ; In the formula, v ent is the resuspension velocity of rock cuttings particles; The momentum conservation equation of the suspended layer liquid phase is: Where g is the gravitational acceleration; φ is the well inclination angle; L2 is the contact length between the suspension layer and the inner wall of the wellbore model and the drill string model, L2 = L 2,in +L 2,out =Π(D h +D p )-L1; L1 is the contact length between the cuttings bed and the inner wall of the wellbore model and the drill string model, L1=L 1,in +L 1,out =D h θ h +D p θ p ; τ2 is the shear stress between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model; F sf is the drag force between the solid and liquid phases in the suspension layer; The solid phase momentum conservation equation of the suspended layer is: In the formula, τ l2 is the shear stress between the interface of the suspended layer and the cuttings bed; The momentum conservation equation for the cuttings bed is: Where τ1 is the shear stress between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model, and F1 is the dry friction resistance between the solid phase in the cuttings bed per unit length and the inner wall of the wellbore model and the outer wall of the drill string model.

5. The method for predicting the cleaning status of a transient extended reach well based on well temperature and drill string rotation according to claim 4 is characterized in that: In the mechanical equation, the shear stress τ2 between the suspension layer and the inner wall of the wellbore model and the outer wall of the drill string model is: in, Where f2 is the friction coefficient of the suspension layer; Re2 is the Reynolds number of the suspension layer; D2 is the hydraulic diameter of the suspension layer, M is the fluidity index, k is the liquid phase consistency coefficient; The shear stress τ between the suspension layer and the cuttings bed interface l2 for: in, In the formula, f l2 is the interfacial friction coefficient between the suspension layer and the cuttings bed; Re l2 is the Reynolds number between the suspension layer and the cuttings bed interface; d c is the diameter of the cuttings; The drag force F between the solid and liquid phases in the suspension layer sf for: in, In the formula, C D is the drag coefficient; Re p is the particle Reynolds number; The shear stress τ1 between the liquid phase in the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model is: in, Where f1 is the friction coefficient of the cuttings bed; Re1 is the Reynolds number of the cuttings bed; D1 is the hydraulic diameter of the cuttings bed, μ1 is the consistency coefficient of the cuttings bed mixture, which is determined by correcting the liquid phase consistency coefficient k according to the cuttings concentration of the cuttings bed; The dry friction resistance F1 between the solid phase in the unit length of the cuttings bed and the inner wall of the wellbore model and the outer wall of the drill string model is: Where η is the dry friction coefficient; The rock cuttings particle settling velocity v dep for: in dep =(1-C s2 ) m in p ; in, Where m is the sedimentation velocity constant; Re dep is the particle Reynolds number when the cuttings particles are settling; v p is the settling velocity of a single rock cutting particle; The resuspension velocity of the cuttings particles from the cuttings bed to the suspension layer is assumed to be a linear relationship between the friction velocities of the two layers, and the resuspension velocity v of the cuttings particles is determined. ent for: in, In the formula, m ent is the resuspension coefficient of rock debris particles; v l2 is the friction speed; is the critical friction velocity; α is the repose angle of the cuttings bed; C' D is the drag force coefficient based on friction speed, and its value is 0.

4.

6. The method for predicting the cleaning status of a transient extended reach well based on well temperature and drill string rotation according to claim 5, characterized in that: The drilling fluid PVT equation is: r l =ρ l0 e Γ (p, T); in, Γ(p,T)=γ P (p-p0)+γ PP (p-p0) 2 +g T (T-T0)+γ TT (T-T0) 2 +g PT (p-p0)(T-T0); In the formula, ρ l0 is the density of drilling fluid under ground temperature and pressure conditions; p is pressure; p0 is ground pressure; T is temperature; T0 is ground temperature; y P , γ PP , γ T , γ TT , γ PT All are fitting coefficients; The temperature-pressure relationship equation of the drilling fluid rheology is: f(p,T)=f(p0,T0)exp[A(T-T0)+B(p-p0)+C(T-T0)(p-p0)+D(T-T0) 2 ]; Where f(p,T) is the rheological property of the drilling fluid at temperature T and pressure p, including the apparent viscosity (μ a ) p,T , plastic viscosity (μ p ) p,T and dynamic shear force (τ0) p,T ; f(p0,T0) is the rheological property of the drilling fluid at temperature T0 and pressure p0, including the apparent viscosity of the drilling fluid at temperature T0 and pressure p0 Plastic viscosity and dynamic shear force A, B, C, and D are the rheological characteristic constants of drilling fluid; The wellbore cleaning lifting degree equation of the drill string rotation is: Where, N is the speed; I q,N It indicates the relative reduction of the mass of the cuttings accumulated in the annulus when the displacement is q and the rotation speed is N, compared with the case where the drill string does not rotate; m q,0 is the mass of cuttings deposited in the annulus under the condition of displacement q and no drill string rotation; m q,N is the mass of cuttings deposited in the annulus when the displacement is q and the drill string speed is N; The solid mass Γ entering the suspension layer from the cuttings bed per unit time and unit length based on the drill string rotation speed and displacement ent,s Correction formula is: In the formula, It is the corrected solid mass entering the suspended layer from the cuttings bed per unit time and unit length.

7. The method for predicting the cleaning state of a transient extended reach well based on well temperature and drill string rotation according to claim 6 is characterized in that: The S3 step includes: The extended reach well model is used for simulation. The extended reach well model is placed in a staggered grid that is evenly divided. The pressure item is arranged at the grid interface. The grid node numbers are evenly distributed along the axial direction of the horizontal well section of the extended reach well model from the bottom of the well to the wellhead. The grid node where the drill bit is located is taken as the initial node, and the initial node number is 0. The mass conservation equation and momentum conservation equation of the extended displacement well model are discretized implicitly in the first-order upwind format. The mass conservation equation of the suspended layer liquid phase after the implicit discretization of the first-order upwind scheme is: Where i is the grid node number; n is the time step number; Δt is the time interval; Δs is the interval length along the axial direction of the wellbore model; The solid mass conservation equation of the suspended layer after the implicit discretization of the first-order upwind scheme is: The mass conservation equation of the cuttings bed after the implicit discretization of the first-order upwind scheme is: The momentum conservation equation of the suspended layer liquid phase after the implicit discretization of the first-order upwind scheme is: The momentum conservation equation of the suspended layer solid phase after the implicit discretization of the first-order upwind scheme is: The momentum conservation equation of the cuttings bed after the implicit discretization of the first-order upwind scheme is: Set the initial conditions, boundary conditions and total simulation time of the extended reach well model; the initial conditions are set as: In the formula, Q l is the drilling fluid displacement; A a is the total cross-sectional area of ​​the annulus, p h is the static column pressure of drilling fluid at the grid node; Δp f is the friction pressure drop from the center of the grid along the annulus back to the ground; It is known that the annulus node number corresponding to the drill bit is 0. All the cuttings generated by the drill bit breaking the rock at the annulus node No. 0 enter the annulus of the extended reach well model. At this time, the boundary condition is set as: In the formula, Q c D is the volume of rock cuttings produced per unit time when the drill bit is drilling; b is the drill diameter; v d is the mechanical drilling speed of the drill bit; Based on the mass conservation equation and momentum conservation equation after implicit discretization of the first-order upwind format of the large-displacement well model, combined with the initial conditions and boundary conditions, the momentum conservation equation and mass conservation equation corresponding to each time step are predicted, the predicted step momentum conservation equation and the predicted step mass conservation equation are determined, and the corrected step momentum conservation equation and the corrected step mass conservation equation are obtained by correction; Based on the SETS method, a large displacement well model is used for simulation, and the clean state of the transient large displacement well is predicted according to the prediction equation of momentum conservation, the prediction equation of mass conservation, the modified equation of momentum conservation and the modified equation of mass conservation.

8. The method for predicting the cleaning status of a transient extended reach well based on well temperature and drill string rotation according to claim 7, characterized in that: The predicted step momentum conservation equation is based on the pressure p at the previous moment. n Determine the prediction speed for the n+1th time step The mass conservation equation and momentum conservation equation after the implicit discretization of the first-order upwind format of the extended reach well model are transformed into first-order linear equations, and the calculation formulas for the velocity term and shear term are determined as follows: in, v n v n+1 =v n (2v n+1 -v n ); In the formula, β is the calculation coefficient; The predicted step momentum conservation equations include a suspended layer solid phase momentum conservation prediction equation, a suspended layer liquid phase momentum conservation prediction equation, and a cuttings bed momentum conservation prediction equation; The prediction equation for the conservation of solid phase momentum in the suspended layer is: In the formula, is the predicted value of solid phase velocity in the suspension layer; is the predicted value of the liquid phase velocity in the suspension layer; is the predicted value of the liquid-solid two-phase flow velocity in the cuttings bed; The prediction equation for the conservation of momentum of the suspended layer liquid phase is: The momentum conservation prediction equation for the cuttings bed is: The modified step momentum conservation equation includes a modified suspended layer solid phase momentum conservation prediction equation, a modified suspended layer liquid phase momentum conservation prediction equation and a modified cuttings bed momentum conservation prediction equation; The modified suspended layer solid phase momentum conservation prediction equation is: The modified prediction equation for conservation of momentum of the suspended layer liquid phase is: The modified cuttings bed momentum conservation equation is: The prediction step mass conservation equation calculates the velocity v based on the current time step n+1 , determine the solid volume fraction at each grid node at the n+1th time step and area Including the prediction equations for the conservation of mass of the suspended layer solid phase, the prediction equations for the conservation of mass of the suspended layer liquid phase, and the prediction equations for the conservation of mass of the cuttings bed; The suspended layer solid phase mass conservation prediction equation is: In the formula, is the predicted value of the cuttings concentration in the suspended layer; is the predicted value of the cross-sectional area of ​​the suspended layer; The prediction equation for the mass conservation of the suspended layer liquid phase is: In the formula, is the predicted value of the liquid volume fraction of the suspension layer; The cuttings bed mass conservation prediction equation is: In the formula, is the predicted value of the cross-sectional area of ​​the cuttings bed; The mass conservation equation of the correction step is based on the solid volume fraction at each grid node calculated in the current prediction step. area and speed v n+1 , determine the solid volume fraction C at each grid node in the n+1th time step n+1 and area A n+1 , including the revised prediction equation for the conservation of mass of the solid phase of the suspended layer, the revised prediction equation for the conservation of mass of the liquid phase of the suspended layer and the revised prediction equation for the conservation of mass of the cuttings bed; The modified suspended layer solid phase mass conservation prediction equation is: The modified suspension layer liquid phase mass conservation prediction equation is: The modified cuttings bed mass conservation prediction equation is:

9. The method for predicting the cleaning status of a transient extended reach well based on well temperature and drill string rotation according to claim 8, characterized in that: The SETS method is based on using the large displacement well model for simulation, and according to the prediction step momentum conservation prediction equation, the prediction step mass conservation prediction equation, the modified step momentum conservation prediction equation and the modified step mass conservation prediction equation, the clean state of the transient large displacement well is predicted, including: S11. Using the extended reach well model to perform simulation, the drilling fluid density in each grid is determined according to the drilling fluid PVT equation for the pressure and temperature of each grid node in the previous time step, and the rheology of the drilling fluid in each grid is determined according to the temperature-pressure relationship equation of the rheology of the drilling fluid; S12. Based on the calculation data of the previous time step of each grid node, determine the sedimentation velocity of the rock cuttings particles and the resuspension velocity of the rock cuttings particles, combined with the liquid mass Γ entering the rock cuttings bed from the suspension layer per unit time dep,l , the solid mass per unit time and unit length from the suspension layer into the cuttings bed layer Γ dep,s , the mass of liquid entering the suspension layer from the cuttings bed per unit time and unit length Γ ent,l and the mass of solid phase entering the suspension layer from the cuttings bed per unit time and unit length Γ ent,s , obtain liquid deposition data, solid deposition data and solid resuspension data, and make rotation speed correction based on the wellbore purification lifting degree equation of drill string rotation; S13. Based on the pressure of each grid node in the previous time step, calculate the momentum conservation equation of the prediction step and determine the velocity at the grid node at the current time Substitute it into the modified step momentum conservation equation and get The speed v n+1 ; S14. Set the speed v n+1 Substituting into the prediction step mass conservation equation, the calculation is determined and pressure Substitute it into the modified step momentum conservation equation to determine the current velocity v n+1 Substitute it into the modified step mass conservation equation to determine C n+1 , A n+1 and pressure S15. Update the pressure p at each grid node, the liquid-solid two-phase flow velocity v1 in the cuttings bed, and the liquid phase flow velocity v in the suspension layer. l2 , solid phase velocity v in the suspension layer s2 and cuttings concentration; S16. Repeat steps S11 to S15 to calculate the physical quantities to be predicted at each grid node at the next moment, the physical quantities to be predicted include the pressure p at the grid node, the liquid-solid two-phase flow velocity v1 in the cuttings bed, the liquid phase flow velocity v1 in the suspension layer, l2 , solid phase velocity v in the suspension layer s2 and rock cuttings particle concentration until the preset total simulation time is reached; S17. According to the calculated physical quantities to be predicted at each grid node at each time, the suspension, deposition and resuspension of cuttings particles in the transient extended displacement well are obtained, the prediction result of the clean state of the transient extended displacement well is obtained, and a prediction diagram of the clean state of the transient extended displacement well is generated; S18. Output the transient large-reach well cleaning status prediction diagram.

10. A transient extended reach well cleaning state prediction system based on well temperature and drill string rotation, characterized in that: include: The extended reach well model building module builds the extended reach well model according to the design parameters of the extended reach well, and sets the fluid type and flow rate in the horizontal annulus of the extended reach well model; A control equation determination module establishes a mass conservation equation and a momentum conservation equation, forms a nonlinear first-order partial differential control equation group through the mass conservation equation and the momentum conservation equation, establishes an auxiliary equation, substitutes the auxiliary equation into the nonlinear first-order partial differential control equation group to form a nonlinear first-order partial differential control equation group for determining unknown variables; The cleaning state prediction module uses the extended displacement well model for simulation. Based on the SETS method, the mass conservation equation and momentum conservation equation in the nonlinear first-order partial differential control equation group of the extended displacement well model are solved. The downhole temperature, pressure and drill string speed are comprehensively considered to simulate and calculate the momentum conservation equation and mass conservation equation corresponding to each moment and make corrections to obtain the liquid-solid two-phase flow velocity v1 in the cuttings bed and the liquid phase flow velocity v in the suspension layer at each moment. l2 , solid phase velocity v in the suspension layer s2 , the concentration of rock debris in the suspended layer C s2 , the height h of the cuttings bed and the pressure p at the axial position along the wellbore to predict the cleaning state of the transient extended reach well.

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