A method and system for calculating the core temperature during the upward lifting process of drilling coring

Abstract

The present application relates to a method and system for calculating the core temperature during the lifting process of drilling coring. The method includes the following steps: dividing the core barrel into multiple layers of barrel wall structures, and obtaining the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the core lifting process; establishing a radial heat transfer model between the barrel wall structures from the inside to the outside based on each barrel wall structure and the corresponding basic parameters; setting the model boundary conditions based on the model and initializing the model parameters according to the relevant parameters of the wellbore and the formation; determining the temperature distribution of the core along the entire wellbore based on the motion parameters according to the radial heat transfer model, and obtaining the variation law of the core temperature with the lifting time. By calculating the dynamic change of the core temperature during the coring process, the present application overcomes the influence of core movement, annulus fluid and formation contact, and obtains the dynamic change law of the core temperature during the entire well section and the lifting process, thereby providing a basis for the optimization design of coring and improving work efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of heat and mass transfer in wellbores, and particularly to a method and system for calculating the core temperature during the lifting process of drilling coring. Background Technique

[0002] With the continuous expansion of the exploration and development areas of geothermal resources and oil and gas resources, the effective acquisition of formation information has become one of the key core issues faced in the efficient development of geothermal and oil and gas resources. Drilling coring is an effective way to obtain formation information by sending a coring barrel to the bottom of the well to obtain a formation core sample, and then transporting the coring barrel and the obtained core from the bottom of the well to the wellhead to obtain a formation core sample, which can obtain key parameters such as the true porosity, permeability, and oil and gas saturation of the target formation.

[0003] However, with the continuous increase in the wellbore depth, the influence of formation pressure and temperature on the core becomes more and more significant. Under different temperature and pressure conditions, the porosity, permeability, and oil and gas saturation of the core will change significantly, thus affecting the accuracy of obtaining formation information by obtaining core samples. Therefore, pressure and temperature maintenance coring has become a widely used coring method in deep wellbores. Among them, pressure maintenance can be achieved by using a pressure compensation device to keep the core in the formation pressure state all the time, and there are various ways to achieve temperature maintenance, including active heating compensation and passive heat insulation, etc. In order to select the optimal temperature maintenance method and optimize the coring process parameters, it is necessary to analyze and simulate the temperature change of the core during the drilling coring process.

[0004] However, the core is always in dynamic motion during the lifting process, the time scale is much smaller than the oil and gas production process, and heat exchange occurs with the wellbore fluid and the formation, resulting in the difficulty of calculating the core temperature during the lifting process by semi-steady state and other wellbore temperature calculation methods. At present, the method of numerical simulation has the problems of large workload of solving and inability to calculate the temperature change during the entire lifting process, with low work efficiency and low accuracy. Summary of the Invention

[0005] The present application provides a method and system for calculating the core temperature during the lifting process of drilling coring. By calculating the dynamic change of the core temperature during the coring process, the influence of core movement, annulus fluid and formation contact is overcome, the temperature distribution of the core along the entire wellbore is obtained, the dynamic change law of the core temperature during the entire well section and the lifting process is determined, the coring accuracy is improved, so as to provide a basis for the optimized design of coring and improve the work efficiency.

[0006] In a first aspect, the present application provides a method for calculating the core temperature during the lifting process of drilling coring, including the following steps: Divide the core barrel into multiple layers of barrel wall structures, and obtain the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the core lifting process. Among them, the barrel wall structure includes a core, an inner core steel barrel, a heat insulation layer, water between the inner and outer core steel barrels, and an outer core steel barrel; Based on each of the barrel wall structures and the corresponding basic parameters, establish a radial heat transfer model between the barrel wall structures from the inside to the outside; Based on the radial heat transfer model, set the model boundary conditions and initialize the model parameters according to the relevant parameters of the wellbore and the formation; Based on the motion parameters, determine the temperature distribution of the core along the entire wellbore according to the radial heat transfer model, and obtain the variation law of the core temperature with the lifting time;

[0007] Optionally, divide the core barrel into multiple layers of barrel wall structures, and obtain the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the core lifting process. The parameters include: The basic parameters include the density ρ, specific heat capacity C, height L, radius r, and thermal conductivity λ of each barrel wall structure; The relevant parameters of the wellbore and the formation include the geothermal gradient g e , well depth h, bottom hole temperature, and surface temperature T 0 ; The motion parameters during the core lifting process include the lifting speed v and the lifting time t z .

[0008] Optionally, establishing a radial heat transfer model between the barrel wall structures from the inside to the outside based on each of the barrel wall structures and the corresponding basic parameters includes: Calculating the process parameters of the radial heat transfer model between the barrel wall structures based on the basic parameters; Among them, the process parameters include the volume V of each barrel wall structure of the core barrel and the heat transfer coefficient U of each part of the inner core steel barrel, the heat insulation layer, the water between the inner and outer core steel barrels, and the outer core steel barrel; Based on the basic parameters and the obtained process parameters, respectively construct the radial heat transfer equations of each barrel wall structure to obtain the radial heat transfer model.

[0009] Optionally, calculating the process parameters of the radial heat transfer model between the barrel wall structures based on the basic parameters includes: Obtaining the volume of each barrel wall structure according to the height and radius parameters of the basic parameters of each barrel wall structure. Among them, the core is a cylinder, and the volume is described by the formula:

[0010] V 1 =πr 1 2 L,

[0011] In the formula, V 1 is the core volume, with the unit of m3, r 1is the core radius, with the unit of m, and L is the core height, with the unit of m; the inner core steel cylinder, the insulation layer, the water between the inner and outer core steel cylinders, and the outer core steel cylinder are all cylindrical walls, and their volumes are described by the following formula:

[0012]

[0013] In the formula, i is the number of each part structure of the core barrel from the inside to the outside, i = 2, 3, 4, 5, Vi is the volume of the corresponding part, with the unit of m 3 , r i is the outer diameter of the corresponding part, with the unit of m, r i-1 is the inner diameter of the corresponding part, with the unit of m 3 ; According to the thermal conductivity λ of the inner core steel cylinder, the insulation layer, the water between the inner and outer core steel cylinders, and the outer core steel cylinder i+1 the heat transfer coefficients U of the corresponding cylindrical wall structures are calculated respectively i , and are described by the formula:

[0014]

[0015] In the formula, U i is the heat transfer coefficient at the corresponding r i radius and r i+1 radius, with the unit of W / (m 2 ·℃); λ i+1 is the thermal conductivity of the corresponding part, with the unit of W / (m·℃).

[0016] Optionally, based on the basic parameters and the obtained process parameters, the radial heat transfer equations of the respective cylindrical wall structures are constructed respectively to obtain a radial heat transfer model, including: segmenting the time for transporting the core barrel from the bottom of the well to the wellhead, and assuming that when the time step is short enough, steady-state heat transfer occurs radially between the respective parts of the core barrel; based on the calculation that the amount of heat transfer between adjacent two cylindrical wall structures is the same as the change in the internal energy of the corresponding cylindrical wall structure, a radial heat transfer model is constructed according to the basic parameters and the obtained process parameters.

[0017] Optionally, based on the calculation that the amount of heat transfer between adjacent barrel wall structures is the same as the change in the internal energy of the corresponding barrel wall structure, a radial heat transfer model is constructed according to the basic parameters and the obtained process parameters, including: within a segmented time step, calculating the heat transferred radially from the core to the inner core steel barrel and the change in the internal energy of the core itself according to the basic parameters of the core and the process parameters, and constructing the radial heat transfer equation of the core based on the fact that the transferred heat is the same as the change in its own internal energy; within a segmented time step, calculating the heat radially transferred between the water between the inner core steel barrel, the insulation layer, and the outer core steel barrel and the change in the internal energy of the inner core steel barrel, the insulation layer, and the outer core steel barrel itself according to the basic parameters of the water between the inner core steel barrel, the insulation layer, and the outer core steel barrel and the process parameters, and constructing the radial heat transfer equations of the inner core steel barrel, the insulation layer, and the outer core steel barrel respectively based on the fact that the transferred heat is the same as the change in their own internal energies; within a segmented time step, calculating the heat radially transferred from the outer core steel barrel to the annulus water and the change in the internal energy of the outer core steel barrel itself according to the basic parameters of the outer core steel barrel and the process parameters, and constructing the radial heat transfer equation of the outer core steel barrel based on the fact that the transferred heat is the same as the change in its own internal energy, where the annulus water refers to the water filled between the core barrel and the wellbore wall; based on the constructed radial heat transfer equations of each barrel wall structure, the radial heat transfer model of each barrel wall structure is obtained to determine the radial variation law of the core temperature.

[0018] Optionally, before constructing the radial heat transfer model, it also includes preset conditions, specifically including: based on the fact that the core length is much smaller than the wellbore depth, the center point of the core is taken as the temperature calculation point; based on the fact that the core is in a moving state in the wellbore and the speed is slow, frictional heat generation and longitudinal heat transfer are ignored; it is preset that the core barrel is always centered and the temperatures of the wellbore wall and the annulus water are the same as the formation temperature.

[0019] Optionally, based on the model, the model boundary conditions are set and the model parameters are initialized according to the relevant parameters, including: based on the process of lifting the core barrel from the bottom of the well to the wellhead being regarded as a uniform motion, the relationship between the lifting speed and the lifting time is obtained and described by the formula:

[0020]

[0021] In the formula, v is the lifting speed, with the unit of m / s, t z is the total movement time, with the unit of s, h is the well depth, with the unit of m; the initial temperature of each part of the core barrel is set to be equal to the core-taking formation temperature, and is described by the formula:

[0022] T i 0 = T 0+g e h,

[0023] wherein, T i 0 is the initial temperature of the corresponding part of the core barrel, in °C, T 0 is the ground temperature, in °C, g e is the geothermal gradient, in °C / m; it is set that the annulus water temperature in contact with the m-th time period is equal to the formation temperature, which is described by the formula:

[0024]

[0025] wherein, T i 0 is the initial temperature of the corresponding part of the core barrel, in °C, T 0 is the ground temperature, in °C, g e is the geothermal gradient, in °C / m; calculate the maximum value of the time segments, and the number of time segments is described by the formula:

[0026]

[0027] wherein, M is the maximum value of the time segments, t z is the total movement time, and △t is the time step.

[0028] Optionally, the process of lifting the core barrel from the bottom of the well to the wellhead is regarded as a uniform motion. According to the radial heat transfer model, the temperature distribution of the core along the entire wellbore is determined, and the variation law of the core temperature with the lifting time is obtained, including: based on the radial heat transfer model, the temperature fields of each part of the core barrel at different time periods are obtained in the order from inside to outside and from bottom to top to obtain the temperature distribution of the core along the entire wellbore; according to the relationship between the movement parameters of the core barrel and the well depth, the variation law of the core with the lifting time is obtained.

[0029] In a second aspect, the present application provides a core temperature calculation system during the upward lifting process of drilling coring. The system includes: an acquisition module, which is used to divide the core barrel into multiple layers of barrel wall structures, and acquire the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the upward lifting process of the core. Among them, the barrel wall structure includes the core, the inner core steel barrel, the insulation layer, the water between the inner and outer core steel barrels, and the outer core steel barrel; a model construction module, which is used to establish a radial heat transfer model between the barrel wall structures from the inside to the outside based on the respective barrel wall structures and the corresponding basic parameters; an initialization module, which is used to set the model boundary conditions based on the radial heat transfer model and initialize the model parameters according to the relevant parameters of the wellbore and the formation; a processing module, which regards the upward lifting process of the core barrel from the bottom of the well to the wellhead as a uniform motion, and determines the temperature distribution of the core along the entire wellbore according to the radial heat transfer model, and obtains the variation law of the core temperature with the upward lifting time.

[0030] In a third aspect, the present application further provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. The characteristic is that when the processor executes the computer program, the steps of the above-mentioned method are implemented.

[0031] In a fourth aspect, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned method are implemented.

[0032] The present application has at least the following advantages:

[0033] The core barrel is divided into multiple layers of barrel wall structures, and the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the upward lifting process of the core are acquired. Based on the acquired multi-layer barrel wall structures and combined with the parameters of each barrel wall, a radial heat transfer model between each barrel wall is constructed according to the fact that the heat transfer between adjacent two barrel wall structures is the same as the change in the internal energy of the corresponding barrel wall structure. According to the constructed radial heat transfer model, the dynamic change of the core temperature during the coring process is calculated, overcoming the influence of core movement, annulus fluid and formation contact, obtaining the temperature distribution of the core along the entire wellbore, determining the dynamic change law of the core temperature during the entire well section and the upward lifting process, improving the coring accuracy, thereby providing a basis for the optimized design of coring and improving the work efficiency. Description of the Drawings

[0034] Figure 1 It is an application environment diagram showing the core temperature calculation method during the upward lifting process of drilling coring in an embodiment;

[0035] Figure 2 It is a schematic flow chart showing the steps of the core temperature calculation method during the upward lifting process of drilling coring in an embodiment;

[0036] Figure 3 Schematic diagram showing the core barrel structure in one embodiment;

[0037] Figure 4 Schematic diagram showing the steps of constructing a radial heat transfer model in one embodiment;

[0038] Figure 5 Block diagram showing the structure of the core temperature calculation system during the lifting process of drilling coring in one embodiment;

[0039] Figure 6 Schematic structural diagram of a computer device in one embodiment. Detailed implementation manners

[0040] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present application, many technical details are provided to help the reader better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented. The labels of the following embodiments are for convenience of description and should not constitute any limitation to the specific implementation manners of the present application. The various embodiments can be combined with each other and cross-referenced on the premise of not being contradictory.

[0043] Figure 2 Flowchart showing a method for calculating the core temperature during the lifting process of drilling coring provided by an embodiment of the present application. This method can be executed by a user space file server in a system as shown in Figure 1 shown. As shown in Figure 2 、 Figure 3 shown, this method may include the following steps:

[0044] S201. Divide the core barrel into multiple layers of barrel wall structures, and obtain the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the upward movement of the core. Among them, the barrel wall structure includes the core, the inner core steel barrel, the insulation layer, the water between the inner and outer core steel barrels, and the outer core steel barrel;

[0045] S202. Based on each barrel wall structure and the corresponding basic parameters, establish a radial heat transfer model between the barrel wall structures from the inside to the outside;

[0046] S203. Based on the radial heat transfer model, set the model boundary conditions and initialize the model parameters according to the relevant parameters of the wellbore and the formation;

[0047] S204. Based on the motion parameters, determine the temperature distribution of the core along the entire wellbore according to the radial heat transfer model, and obtain the variation law of the core temperature with the upward movement time.

[0048] Divide the core barrel into multiple layers of barrel wall structures, and obtain the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the upward movement of the core. According to the obtained multi-layer structure of the core barrel and combined with the obtained parameters, construct a radial heat transfer model between each barrel wall. Initialize the model and calculate the temperature distribution of the core along the entire wellbore according to the constructed radial heat transfer model. According to the relationship between the motion speed, well depth, and time, obtain the variation law of the core temperature with the upward movement time, improve the coring accuracy, thereby providing a basis for the optimized design of coring and improving the work efficiency.

[0049] The following will specifically expand and elaborate on each step:

[0050] Please refer to Figure 2 、 Figure 3 As shown in, step S201. Divide the core barrel into multiple layers of barrel wall structures, and obtain the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the upward movement of the core;

[0051] In this embodiment, it should be noted that the barrel wall structure includes the core, the inner core steel barrel, the insulation layer, the water between the inner and outer core steel barrels, and the outer core steel barrel. The entire core barrel enters the well, and the core barrel is on the center line of the entire well and moves vertically up and down along the well. There is also annulus water filled between the outer side of the outer core steel barrel of the core barrel and the well wall. According to the divided multi-layer structure of the core barrel, obtain the basic parameters of each barrel wall structure, the relevant parameters of the wellbore and the formation, and the motion parameters during the upward movement of the core. The basic parameters include the density ρ, specific heat capacity C, height L, radius r, and thermal conductivity λ of each barrel wall structure; the relevant parameters of the wellbore and the formation include the geothermal gradient g e 、well depth h, bottom hole temperature, and surface temperature T 0, where the geothermal gradient is a parameter representing the degree of inhomogeneous temperature distribution within the Earth. It is usually expressed as the number of Celsius degrees increase in temperature per 100-meter vertical depth. The motion parameters during the core lifting process include the lifting speed v and the lifting time t z , based on the various parameters obtained, provides a data basis for subsequent calculation and processing.

[0052] Please continue to refer to Figures 2 - 4 As shown, in step S202, a radial heat transfer model between the barrel wall structures from the inside to the outside is established based on each barrel wall structure and the corresponding basic parameters, specifically including:

[0053] Step S2021: Calculate the process parameters of the radial heat transfer model between the barrel wall structures based on the basic parameters;

[0054] In this embodiment, it should be noted that specifically, the process parameters include the volume V of each barrel wall structure of the core barrel, as well as the heat transfer coefficients U of each part of the inner core steel barrel, the insulation layer, the water between the inner and outer core steel barrels, and the outer core steel barrel; the volume of each barrel wall structure is obtained based on the height and radius parameters of the basic parameters of each barrel wall structure. Among them, the core is a cylinder, and the volume is described by formula (1):

[0055] V 1 = πr 1 2 L (1),

[0056] In the formula, V 1 is the core volume, with the unit of m 3 ; r 1 is the core radius, with the unit of m, and L is the core height, with the unit of m; the inner core steel barrel, the insulation layer, the water between the inner and outer core steel barrels, and the outer core steel barrel are all cylindrical walls, and their volumes are described by formula (2):

[0057]

[0058] In the formula, i is the number of each part structure of the core barrel from the inside to the outside, i = 2, 3, 4, 5, V i is the volume of the corresponding part, with the unit of m 3 , r i is the outer diameter of the corresponding part, with the unit of m, r i-1 is the inner diameter of the corresponding part, with the unit of m 3 ;

[0059] In addition, in an example, according to the thermal conductivities λ corresponding to the inner core steel barrel, the insulation layer, the water between the inner and outer core steel barrels, and the outer core steel barrel i+1 the heat transfer coefficients U of the inner core steel barrel, the insulation layer, and the water between the inner and outer core steel barrels are calculated respectively i, which is described by formula (3):

[0060]

[0061] In the formula, i is the number of each part of the core barrel from the inside to the outside, i = 2, 3, 4, 5, U i is the heat transfer coefficient corresponding to the radius of r i and the radius of r i+1 at the radius, with the unit of W / (m 2 ·℃); λ i+1 is the thermal conductivity of the corresponding part, with the unit of W / (m·℃). For example, U 2 is the thermal conductivity of the inner core steel barrel, corresponding to the heat transfer coefficient at the radius of the inner core steel barrel and the radius of the insulation layer.

[0062] Step S2022: Based on the basic parameters and the obtained process parameters, respectively construct the radial heat transfer equation of the core, the energy equation of the water between the inner core steel barrel, the insulation layer, and the outer core steel barrel, and the radial heat transfer equation of the outer core steel barrel, to obtain the radial heat transfer model.

[0063] In this embodiment, it should be noted that the time for the core barrel to migrate from the bottom of the well to the wellhead is segmented. When the time step is short enough, it can be considered that steady-state heat transfer occurs between each part of the core barrel; therefore, the radial heat transfer equation of the core is constructed according to the fact that the heat transferred from the core radially to the inner core steel barrel is the same as the change in the internal energy of the core itself.

[0064] In an example, the radial heat transfer equation of the core is constructed according to the density of the basic parameters of the core, the specific heat capacity parameter of the core, and the volume and heat transfer coefficient parameter of the process parameters, and is described by formula (4):

[0065]

[0066] In the formula, m is the number of the time segment, m = 0, 1, 2, 3.........; T 1 m+1 is the temperature of the core in the (m + 1)-th time period, with the unit of ℃, T 1 m is the temperature of the core in the m-th time period, with the unit of ℃, ρ 1 is the density of the core, with the unit of kg / m 3 ; C 1 is the specific heat capacity of the core, with the unit of J / (kg·℃), is the temperature of the inner core steel barrel in the m-th time period, with the unit of ℃, and △t is the time step, with the unit of s.

[0067] Within segmented time steps, calculate the heat radially transferred between the adjacent inner core steel cylinder, insulation layer, and outer core steel cylinder and the change in internal energy of the inner core steel cylinder, insulation layer, and outer core steel cylinder themselves based on the basic parameters and process parameters of the water between the inner core steel cylinder, insulation layer, and outer core steel cylinder. Construct the radial heat transfer equations for the inner core steel cylinder, insulation layer, and outer core steel cylinder respectively according to the fact that the transferred heat is the same as the change in their own internal energy.

[0068] Specifically, construct the energy equation of the water between the inner core steel cylinder, insulation layer, and outer core steel cylinder based on the density of the basic parameters of the inner core steel cylinder, insulation layer, and water between the inner and outer core steel cylinders, the core specific heat capacity parameter, and the volume and heat transfer coefficient parameter of the process parameters, and describe it by formula (5):

[0069]

[0070] In the formula, T i m+1 is the temperature of the corresponding part in the (m + 1)-th time period, in °C, T i m is the temperature of the corresponding part in the m-th time period, in °C; ρ1 is the density of the corresponding part, in kg / m 3 , C 1 is the specific heat capacity of the corresponding part, in J / (kg·°C), is the temperature of the corresponding part in the m-th time period, in °C.

[0071] Within segmented time steps, calculate the heat radially transferred from the outer core steel cylinder to the annulus water and the change in internal energy of the outer core steel cylinder itself based on the basic parameters and process parameters of the outer core steel cylinder. Construct the radial heat transfer equation of the outer core steel cylinder according to the fact that the transferred heat is the same as the change in its own internal energy.

[0072] Specifically, construct the radial heat transfer equation of the outer core steel cylinder based on the density of the basic parameters of the outer core steel cylinder, the specific heat capacity parameter of the outer core steel cylinder, and the volume and heat transfer coefficient parameter of the process parameters, and describe it by formula (6):

[0073]

[0074] In the formula, is the temperature of the outer core steel cylinder in the (m + 1)-th time period, in °C, is the temperature of the outer core steel cylinder in the m-th time period, in °C, ρ 5 is the density of the outer core steel cylinder, in kg / m 3 , C 5 is the specific heat capacity of the outer core steel cylinder, in J / (kg·°C), is the annulus water temperature contacted by the outer core steel cylinder in the m-th time period, with the unit of °C;

[0075] According to the radial heat transfer equations of each structure of the core barrel constructed above, a radial heat transfer model is obtained, so as to determine the variation law of the core temperature along the radial direction.

[0076] Refer to Figure 3 、 Figure 4 As shown in, in step S202, before constructing the radial heat transfer model, preset conditions are also set, specifically including: based on the fact that the core length is much smaller than the wellbore depth, the center point of the core is taken as the temperature calculation point; based on the fact that the core is in a moving state in the wellbore and the speed is slow, frictional heat generation and longitudinal heat transfer are ignored; it is preset that the core barrel is always centered, and the temperatures of the water filled in the wellbore wall and the annulus are the same as the formation temperature.

[0077] In this embodiment, it should be noted that before constructing the radial heat transfer model, preset conditions are set in advance, the temperature difference of different parts of the core is ignored, the center point of the core is taken as the calculation point, the calculation base point is found, and the obtained calculation point is regarded as the temperature of the entire core. At the same time, during the core sampling process, when the core barrel moves along the wellbore, frictional heat generation will occur. This part of the heat has little influence and can be ignored. When each part of the entire core barrel moves in the vertical direction, it is regarded as a point moving, and the change of its own longitudinal heat is ignored to ensure the rationality of the radial heat transfer model constructed in the subsequent calculation. Finally, it is preset that the core barrel is always centered to ensure uniform radial heat transfer, and it is preset that the wellbore wall and annulus water temperatures are the same as the formation temperature, so as to initialize the constructed model later. The above preset conditions are all within the scope of consideration for constructing the entire radial heat transfer model to increase the accuracy of the constructed model.

[0078] Refer to Figures 2 - 4 As shown in, in step S203, based on the radial heat transfer model, model boundary conditions are set and model parameters are initialized according to relevant parameters;

[0079] First, based on the fact that the process of lifting the core barrel from the bottom of the well to the wellhead is regarded as a uniform motion, the relationship between the lifting speed and the lifting time is obtained and described by formula (7):

[0080]

[0081] In the formula, v is the lifting speed, with the unit of m / s, t z is the total motion time, with the unit of s, and h is the well depth, with the unit of m;

[0082] Set the initial temperature of each part of the core barrel to be equal to the core sampling formation temperature, and it is described by formula (8):

[0083] T i 0= T 0 + g e h(8),

[0084] wherein, T i 0 is the initial temperature of the corresponding part of the core barrel, in °C, T 0 is the ground temperature, in °C, g e is the geothermal gradient, in °C / m;

[0085] Set the annulus water temperature in contact with the m-th time period equal to the formation temperature, which is described by formula (9):

[0086]

[0087] wherein, T i 0 is the initial temperature of the corresponding part of the core barrel, in °C, T 0 is the ground temperature, in °C, g e is the geothermal gradient, in °C / m;

[0088] Calculate the maximum value of the time segment, and the number of time segments is described by formula (10):

[0089]

[0090] wherein, M is the maximum value of the time segment, t z is the total movement time, and Δt is the time step.

[0091] In this embodiment, it should be noted that the process of lifting the core barrel from the bottom of the well to the wellhead is regarded as a uniform motion, the average speed of the core barrel lifting is obtained, and according to the determined time step, the maximum value of the time segment is obtained to determine the boundary conditions of the radial heat transfer model. At the same time, set the initial temperature of each part of the core barrel equal to the core formation temperature, set the annulus water temperature in contact with the m-th time period equal to the formation temperature, and initialize the parameters of the radial heat transfer model for subsequent calculation and processing.

[0092] Refer to Figure 2 、 Figure 3 shown, step S204, based on the motion parameters, determine the temperature distribution of the core along the entire wellbore according to the radial heat transfer model, and obtain the variation law of the core temperature with the lifting time.

[0093] In this embodiment, it should be noted that according to the obtained radial heat transfer model and combined with the set boundary conditions, the equations are solved in the order from the inside to the outside and from the bottom to the top. In the initial state, let m = 0, and then let i = 1. First, the temperature change of the core is solved, and then let i = i + 1 to sequentially solve the temperature changes of other parts. After solving the temperature fields of all parts, calculate the temperature fields of all parts at the next time period, that is, m = m + 1, and then let i = 1 again. Repeat the above steps until the core barrel is lifted from the bottom of the well to the wellhead, that is, m = M, and the calculation ends. Through the above steps, the temperature distribution of the core along the entire wellbore can be obtained. Then, according to the relationship between the movement speed of the core barrel, the well depth, and the time, the specific change law of the core with the lifting time can be obtained.

[0094] The implementation principle of this embodiment: The above steps mainly divide the core barrel into a multi-layer wall structure, and obtain the basic parameters of each wall structure, the relevant parameters of the wellbore and the formation, and the movement parameters during the lifting of the core. According to the obtained multi-layer wall structure, combined with the basic parameters of each wall and the obtained process parameters, a radial heat transfer model between adjacent two wall structures is constructed based on the fact that the heat transfer between adjacent two wall structures is the same as the change in the internal energy of the corresponding wall structure. Initialize the model and calculate the dynamic change of the core temperature during the coring process according to the constructed radial heat transfer model, overcome the influence of core movement, annulus fluid and formation contact, obtain the temperature distribution of the core along the entire wellbore, and according to the relationship between the movement speed, well depth and time, obtain the change law of the core temperature with the lifting time, improve the coring accuracy, so as to provide a basis for the optimized design of coring and improve the work efficiency.

[0095] Refer to Figure 5 As shown, the present application also provides a core temperature calculation system during the lifting process of drilling coring. The system may include: an acquisition module 301, a model construction module 302, an initialization module 303, and a processing module 304. The main functions of each component module are as follows:

[0096] The acquisition module 301 is used to divide the core barrel into a multi-layer wall structure, and obtain the basic parameters of each wall structure, the relevant parameters of the wellbore and the formation, and the movement parameters during the lifting of the core. Among them, the wall structure includes the core, the inner core steel cylinder, the insulation layer, the water between the inner and outer core steel cylinders, and the outer core steel cylinder;

[0097] The model construction module 302 is used to establish a radial heat transfer model between the wall structures from the inside to the outside based on each wall structure and the corresponding basic parameters;

[0098] The initialization module 303 is used to set the model boundary conditions based on the radial heat transfer model and initialize the model parameters according to the relevant parameters of the wellbore and the formation;

[0099] The processing module 304 is configured to regard the process of lifting the core barrel from the bottom of the well to the wellhead as a uniform motion, determine the temperature distribution of the core along the entire wellbore according to the radial heat transfer model, and obtain the variation law of the core temperature with the lifting time.

[0100] As Figure 6 shown, it is a block diagram of a computer device according to an embodiment of the present application. The computer device is intended to represent various forms of digital computers or mobile devices. Among them, the digital computer may include a desktop computer, a portable computer, a workbench, a personal digital assistant, a server, a mainframe computer, and other suitable computers. The mobile device may include a tablet computer, a smart phone, a wearable device, etc.

[0101] As Figure 6 shown, the device 600 includes a computing unit 601, a ROM 602, a RAM 603, a bus 604, and an input / output (I / O) interface 605. The computing unit 601, the ROM 602, and the RAM 603 are connected to each other through the bus 604. The input / output (I / O) interface 605 is also connected to the bus 604.

[0102] The computing unit 601 can execute various processes in the method embodiments of the present application according to the computer instructions stored in the read-only memory (ROM) 602 or the computer instructions loaded from the storage unit 608 into the random access memory (RAM) 603. The computing unit 601 can be various general and / or special processing components with processing and computing capabilities. The computing unit 601 may include, but is not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. In some embodiments, the method provided by the embodiments of the present application can be implemented as a computer software program, which is tangibly contained in a computer-readable storage medium, such as the storage unit 608.

[0103] The RAM 603 can also store various programs and data required for the operation of the device 600. Part or all of the computer programs can be loaded and / or installed onto the device 600 via the ROM 602 and / or the communication unit 609.

[0104] The input unit 606, the output unit 607, the storage unit 608, and the communication unit 609 in the device 600 can be connected to the I / O interface 605. Among them, the input unit 606 can be such as a keyboard, a mouse, a touch screen, a microphone, etc.; the output unit 607 can be such as a display, a speaker, an indicator light, etc. The device 600 can exchange information, data, etc. with other devices through the communication unit 609.

[0105] It should be noted that the device may also include other components necessary for normal operation. It may also only include the components necessary for implementing the solution of this application, and does not necessarily include all the components shown in the figure.

[0106] The various embodiments of the systems and technologies described herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system on a chip (SOC) systems, complex programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof.

[0107] The computer instructions for implementing the methods of this application can be written in any combination of one or more programming languages. These computer instructions can be provided to the computing unit 601, such that when the computer instructions are executed by a computing unit 601 such as a processor, the various steps involved in the method embodiments of this application are executed.

[0108] The computer-readable storage medium provided by this application can be a tangible medium that can contain or store computer instructions for executing the various steps involved in the method embodiments of this application. The computer-readable storage medium can include, but is not limited to, storage media in the forms of electronic, magnetic, optical, electromagnetic, etc.

[0109] The above specific embodiments do not constitute a limitation on the protection scope of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims

1. A method for calculating core temperature during the process of coring in drilling, characterized in that: The following steps are involved: The coring barrel is divided into a multi-layer barrel wall structure, and the basic parameters of each barrel wall structure, the wellbore and formation related parameters, and the movement parameters during the core lifting process are obtained, wherein the barrel wall structure includes the core, the inner core steel barrel, the insulation layer, the water between the inner and outer core steel barrels, and the outer core steel barrel; based on the barrel wall structures and the corresponding basic parameters, a radial heat transfer model between the barrel wall structures from the inner to the outer is established; Setting model boundary conditions based on the radial heat transfer model and initializing model parameters according to the wellbore and formation related parameters; Based on the motion parameters, the temperature distribution of the core along the entire wellbore is determined according to the radial heat transfer model, and the variation law of the core temperature with the lifting time is obtained; The step of setting the model boundary conditions based on the radial heat transfer model and initializing the model parameters according to the relevant parameters includes: Based on the fact that the process of lifting the coring barrel from the bottom of the well to the wellhead is regarded as uniform motion, the relationship between the lifting speed and the lifting time is obtained and described by the formula: Where, v is the lifting speed in m / s, t z is the total movement time in seconds, h is the well depth in meters; The initial temperature of each part of the coring barrel is set equal to the coring formation temperature, which is described by the formula: T i 0 =T0+g e h, Where, T i 0 is the initial temperature of the corresponding part of the core barrel, in °C, T0 is the ground temperature, in °C, g e is the geothermal gradient, in °C / m; The annular water temperature in contact with the mth time period is set to be equal to the formation temperature, which can be described by the formula: Where, T i 0 is the initial temperature of the corresponding part of the core barrel, in °C, T0 is the ground temperature, in °C, g e is the geothermal gradient, in °C / m; Calculate the maximum value of a time segment, the number of time segments is described by the formula: Where M is the maximum value of the time segment, t z is the total movement time, and △t is the time step.

2. The method for calculating core temperature during the core extraction process according to claim 1, characterized in that: The coring barrel is divided into a multi-layer barrel wall structure, and the basic parameters of each barrel wall structure, the wellbore and formation related parameters and the movement parameters during the core lifting process are obtained, including: The basic parameters include the density ρ, specific heat capacity C, height L, radius r, and thermal conductivity λ of each cylinder wall structure; The wellbore and formation related parameters include geothermal gradient g e , well depth h, well bottom temperature and ground temperature T0; The movement parameters of the core during lifting include lifting speed v and lifting time t z .

3. The method for calculating the core temperature during the core extraction process according to claim 2, characterized in that: The radial heat transfer model between the inner and outer cylinder wall structures is established based on the cylinder wall structures and the corresponding basic parameters, including: Calculate the process parameters of the radial heat transfer model between the cylinder wall structures based on the basic parameters; Among them, the process parameters include the volume V of each barrel wall structure of the coring barrel, the inner core steel barrel, the insulation layer, the water between the inner and outer core steel barrels, and the heat transfer coefficient U of each part of the outer core steel barrel; based on the basic parameters and the obtained process parameters, the radial heat transfer equations of each barrel wall structure are respectively constructed to obtain a radial heat transfer model.

4. The method for calculating core temperature during the core extraction process according to claim 3, characterized in that: The process parameters of the radial heat transfer model between the cylinder wall structures are calculated based on the basic parameters, including: The volume of each cylinder wall structure is obtained according to the height and radius parameters of the basic parameters of each cylinder wall structure, wherein the core is a cylinder and the volume is described by the formula: V1=πr1 2 L, Where V1 is the core volume, in m 3 , r1 is the core radius, in m, L is the core height, in m; The inner core steel cylinder, the insulation layer, the water between the inner and outer core steel cylinders, and the outer core steel cylinder are all cylindrical walls, and their volumes are described by the formula: Where i is the number of each part of the core barrel from the inside to the outside, i = 2, 3, 4, 5, V i is the volume of the corresponding part, in m 3 , r i is the outer diameter of the corresponding part, in m, r i-1 is the inner diameter of the corresponding part, in m 3 ; According to the thermal conductivity λ corresponding to the inner core steel cylinder, the insulation layer, the water between the inner and outer core steel cylinders, and the outer core steel cylinder i+1 The heat transfer coefficient U corresponding to each cylinder wall structure is calculated separately i , described by the formula: Where U i For the corresponding r i Radius and r i+1 Heat transfer coefficient at radius, unit is W / (m 2 ·℃);λ i+1 is the thermal conductivity of the corresponding part, and its unit is W / (m·℃).

5. The method for calculating core temperature during the core extraction process according to claim 3 or 4, characterized in that: The radial heat transfer equations of each cylinder wall structure are respectively constructed based on the basic parameters and the obtained process parameters to obtain a radial heat transfer model, including: The time for the core barrel to move from the bottom of the well to the wellhead is segmented, and when the time step is short enough, steady-state heat transfer is preset to occur radially between the parts of the core barrel; Based on the calculation that the amount of heat transfer between two adjacent cylinder wall structures is the same as the amount of change in the internal energy of the corresponding cylinder wall structures, a radial heat transfer model is constructed according to the basic parameters and the obtained process parameters.

6. The method for calculating core temperature during the core extraction process according to claim 5, characterized in that: The calculation based on the heat transfer amount between two adjacent cylinder wall structures being the same as the change amount of the internal energy of the corresponding cylinder wall structures, constructing a radial heat transfer model according to the basic parameters and the obtained process parameters, includes: In the segmented time step, the heat radially transferred from the core to the inner core steel cylinder and the change in the core's own internal energy are calculated according to the basic parameters of the core and the process parameters, and the radial heat transfer equation of the core is constructed based on the fact that the transferred heat is the same as the change in its own internal energy; in the segmented time step, the heat radially transferred between the adjacent inner core steel cylinder, the insulation layer, and the outer core steel cylinder and the change in the inner core steel cylinder, the insulation layer, and the water between the inner core steel cylinder, the insulation layer, and the outer core steel cylinder are calculated according to the basic parameters of the water and the process parameters. , the change in the internal energy of the outer core steel cylinder itself, and the radial heat transfer equations of the inner core steel cylinder, the insulation layer, and the outer core steel cylinder are respectively constructed based on the fact that the transferred heat is the same as the change in its own internal energy; within the segmented time step, the heat radially transferred from the outer core steel cylinder to the annular water and the change in the internal energy of the outer core steel cylinder itself are calculated based on the basic parameters of the outer core steel cylinder and the process parameters, and the radial heat transfer equation of the outer core steel cylinder is constructed based on the fact that the transferred heat is the same as the change in its own internal energy, wherein the annular water represents the water filled between the coring cylinder and the well wall; Based on the constructed radial heat transfer equations of each barrel wall structure, a radial heat transfer model of each barrel wall structure is obtained to determine the radial variation law of the core temperature.

7. The method for calculating core temperature during the core extraction process according to claim 6, characterized in that: Before constructing the radial heat transfer model, preset conditions are also included, specifically including: based on the fact that the length of the core is much smaller than the depth of the wellbore, the center point of the core is taken as the temperature calculation point; based on the fact that the core is in a moving state in the wellbore with a slow speed, frictional heat generation and longitudinal heat transfer are ignored; It is preset that the coring barrel is always centered, and the temperature of the well wall and annular water is the same as the formation temperature.

8. The method for calculating core temperature during the coring process according to claim 1, characterized in that: The method of determining the temperature distribution of the core along the entire wellbore based on the motion parameters and the radial heat transfer model to obtain the variation law of the core temperature with the lifting time includes: Based on the radial heat transfer model, the temperature fields of the various parts of the coring barrel in different time periods are obtained from inside to outside and from bottom to top to obtain the temperature distribution of the core along the entire wellbore; According to the relationship between the movement parameters of the coring barrel and the well depth, the change law of the core with the lifting time is obtained.

9. A core temperature calculation system during the core extraction process, characterized in that: include: An acquisition module is used to divide the coring barrel into a multi-layer barrel wall structure and obtain the basic parameters of each barrel wall structure, the wellbore and formation related parameters, and the movement parameters during the core lifting process; The cylinder wall structure includes a rock core, an inner rock core steel cylinder, an insulation layer, water between the inner and outer rock core steel cylinders, and an outer rock core steel cylinder; A model building module is used to establish a radial heat transfer model between the inner and outer cylinder wall structures based on the cylinder wall structures and the corresponding basic parameters; An initialization module, used to set model boundary conditions based on the radial heat transfer model and initialize model parameters according to the wellbore and formation related parameters; A processing module is used to determine the temperature distribution of the core along the entire wellbore based on the motion parameters and the radial heat transfer model, and obtain the change law of the core temperature with the lifting time.

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