A production cycle calculation method for in-situ conversion of oil shale by using high salinity brine composite electric heating

Abstract

The present application belongs to the technical field of oil shale enhanced recovery, and discloses a production cycle calculation method for in-situ conversion of oil shale by using high salinity brine combined with electric heating, in which two horizontal wells opposite to each other are selected as positive and negative electrodes of electric heating; fracturing is performed on the two horizontal wells, and the fracturing fluid is retained in the fracture network; the two horizontal wells are subjected to energization operation to heat the shale reservoir; during the heating process, the time of temperature rise of the electrically heated formation, the time of organic matter thermal cracking conversion in the oil shale reservoir, the time of upward migration of the oil and gas generated by organic matter thermal cracking conversion under the action of buoyancy, and the production time of the upper horizontal well are calculated; and the production cycle of in-situ conversion of oil shale by using high salinity brine combined with electric heating is calculated according to the foregoing results. The present application calculates the time required for each stage, and finally obtains the total time of one cycle of in-situ conversion production of oil shale when using the heating electric heating method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil shale enhanced recovery, and particularly relates to a production cycle calculation method for in-situ conversion of oil shale by using high salinity brine composite electric heating. BACKGROUND

[0002] The in-situ conversion technology is a trend of oil shale resource development, and the in-situ conversion of oil shale underground is a physical and chemical process of converting heavy oil, asphalt and various organic matters in shale with a buried depth of 300-3000 m into light oil and natural gas by using electric heating lightening technology, which has obvious advantages in clean exploitation, total scale and output quality. Based on the mechanism of organic matter generation and expulsion, research shows that in the low-maturity (Ro value less than 1.0%) organic-rich shale, the proportion of liquid hydrocarbon in the total oil generation is about 25%, and the unconverted organic matter is 40%-100%. The organic-rich shale suitable for in-situ conversion underground should meet the following conditions: the TOC value of the shale accumulation section is greater than 6%, and the higher the better; the Ro value is 0.5%-1.0%; the thickness is greater than 15 m; the buried depth is less than 3000 m, and the area is greater than 50 km 2 ; the top and bottom plate of the shale section is well sealed; and the formation water content is less than 5%.

[0003] In the traditional oil shale heating conversion experiment or simulation, there are a large number of research cases about the oil shale hydrocarbon conversion time under high temperature conditions, but the calculation of the entire production cycle from oil shale heating to oil and gas generation and being extracted is still lacking. SUMMARY

[0004] To solve the problems in the prior art, the main purpose of the present application is to provide a production cycle calculation method for in-situ conversion of oil shale by using high salinity brine composite electric heating, so as to calculate the heating time and production cycle in the process of in-situ exploitation of oil shale.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A production cycle calculation method for in-situ conversion of oil shale by using high salinity brine composite electric heating, comprising the following processes:

[0007] Select two opposite horizontal wells as positive and negative electrodes for electric heating; the upper horizontal well is used as an oil and gas production well, and fracturing operations are performed on both horizontal wells, the fracturing fluid is high salinity brine, and after the fracturing operation is completed, the fracturing fluid is retained in the fracturing fracture network;

[0008] Install an oil and gas wellhead device on the wellhead of the upper horizontal well, and install a wellhead device on the lower horizontal well;

[0009] The two horizontal wells are powered to generate heat by the fracturing fluid staying in the formation as conductive medium, and the shale reservoir is heated, and the formation temperature rises;

[0010] During the heating process, the time of the formation temperature rising stage of the electrically heated formation is calculated , wherein the formation temperature rising stage is a stage in which the organic matter in the oil shale reservoir has not yet cracked by heat; the time of the organic matter thermal cracking conversion stage in the oil shale reservoir is calculated ; the time of the upward migration stage of the oil and gas generated by the organic matter thermal cracking conversion under the action of buoyancy is calculated ; the production time of the upper horizontal well is calculated ;

[0011] The production cycle of the high-salinity brine composite electric heating in-situ conversion of oil shale is calculated .

[0012] Preferably, the temperature demarcation point between the formation temperature rising stage and the organic matter thermal cracking conversion stage in the oil shale reservoir is 350℃.

[0013] Preferably, the time of the formation temperature rising stage of the electrically heated formation is calculated according to the range of the formation temperature rise and the electrical energy injected into the formation .

[0014] Preferably:

[0015] The range of the formation temperature rise ΔT is calculated according to the following formula:

[0016]

[0017] The electrical energy injected into the formation E j is calculated according to the following formula:

[0018]

[0019] The time of the formation temperature rising stage of the electrically heated formation T 1 is calculated according to the following formula:

[0020]

[0021] In the formula, T 1 is the time of the electrically heated formation, in min; ΔT is the amount of the formation temperature rise, in ℃; E j is the electrical energy injected into the formation, in kJ; r is the well diameter of the horizontal well, in m; d is the distance between the two horizontal wells, in m; UThe voltage between the two horizontal wells is expressed in V. L This refers to the length of the horizontal section of a horizontal well, in meters (m). I This represents the current after the formation is energized, expressed in amperes (A). The time for electrical energy injection is expressed in minutes. K The value represents the degree of mineralization, expressed in g / L; a, b, α, and β are constants obtained experimentally.

[0022] Preferably, the time of the organic matter thermal decomposition and transformation stage in oil shale reservoirs Calculated using the following formula:

[0023]

[0024] In the formula, A is the frequency factor, which is the number of molecular collisions per unit time and unit volume; E is the activation energy; R is the gas constant; T is the absolute temperature; c ０ c and c represent the initial concentration of organic matter and the reaction time, respectively. The concentration of reactants at that time;

[0025] reaction time The following relationship must be satisfied:

[0026]

[0027] Where d is a constant, and the calculation method is as follows:

[0028]

[0029] Preferably, the time of the upward migration phase of the oil and gas generated by the thermal cracking of organic matter under the action of buoyancy. The calculation formula is as follows:

[0030]

[0031] In the formula, d This is the distance between two horizontal wells, in meters. The viscosity of the converted oil and gas is expressed in mPa·s. The porosity of the formation is a decimal. The permeability of the formation, in μm 2 ; This represents the pressure gradient drop of the formation, expressed in MPa / m. The density of the converted oil and gas is expressed in kg / m³. 3 ; This is the acceleration due to gravity, expressed in m / s².

[0032] Preferably, the upper horizontal well opening production time The calculation formula is as follows:

[0033]

[0034] wherein, is the amount of oil and gas converted in the formation, is the production index of the horizontal well, P is the reservoir pressure; is the bottom hole flowing pressure of the horizontal well.

[0035] Preferably, the two horizontal wells are staggered and the fracture length is greater than 1 / 2 well spacing.

[0036] Preferably, the high salinity brine has a salinity of 3000-10000 mg / L.

[0037] Preferably, the voltage is controlled at 300-900 V when the two horizontal wells are energized.

[0038] The present application has the following advantages:

[0039] The present application addresses the problems of slow heat transfer and long heating cycle of the existing ICP electric heating. After the high salinity brine is used for fracturing in the oil shale formation, the fracturing fluid is not returned after the fracturing is completed. The heat generated by the brine under the thermal effect of the electric current directly heats the formation, and the heating range is larger and the heating cycle is shorter. Meanwhile, the present application divides the in-situ conversion cycle of oil shale into four stages, which are: the stage of energizing and heating the formation to raise the temperature, in which the organic matter in the oil shale reservoir has not yet cracked; the stage of thermal cracking and conversion of the organic matter in the oil shale reservoir under high temperature (i.e. the stage of thermal cracking and conversion of the organic matter in the oil shale reservoir); the stage of upward migration of the converted oil and gas under the action of buoyancy; and the stage of exploiting the converted oil and gas in the upper horizontal well. The present application calculates the time required for each stage, and finally obtains the total time of the in-situ conversion cycle of oil shale when using this heating method. BRIEF DESCRIPTION OF DRAWINGS

[0040] Fig. 1 is a schematic diagram of the fracture network in the embodiment of the present application;

[0041] Fig. 2 is a schematic diagram of oil and gas migration during the electric heating process in the embodiment of the present application;

[0042] Fig. 3 is a schematic diagram of the electrode arrangement in the embodiment of the present application.

[0043] In the figure, 1 is a production well, 2 is a perforation location, 3 is a negative electrode for electric heating, 4 is a positive electrode for electric heating, and 5 is a fracture network. DETAILED DESCRIPTION

[0044] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments and drawings. Herein, the illustrative embodiments of the present application and their descriptions are used to explain the present application but not as a limitation of the present application.

[0045] The present application proposes a production cycle calculation method for in-situ conversion of oil shale by using high salinity brine composite electric heating, and in order to solve the problems of slow heat transfer and long heating cycle of the existing ICP heating method for in-situ conversion of oil shale, the present application proposes a new electric heating method based on the traditional electric heating, and cooperates with the fracturing process to shorten the heating cycle. The heating method mainly uses high salinity brine compatible with the formation as fracturing fluid in the fracturing process, and uses the non-flowback brine fracturing fluid as the conductive medium for subsequent heating; the heat energy enters the oil shale reservoir, and the solid kerogen in the oil shale or low-maturity shale oil reservoir is converted into light oil and natural gas under the action of high temperature; the converted oil and gas enter the upper production well under the action of buoyancy; the converted light oil and natural gas are produced by opening the upper production well. In order to calculate the time required for one production cycle of in-situ electric heating conversion, the calculation formula for the time required for four stages of in-situ conversion is derived.

[0046] Specifically, referring to Figs. 1-3 The production cycle calculation method for in-situ conversion of oil shale by using high salinity brine composite electric heating of the present application comprises the following steps:

[0047] Step S1: two double horizontal wells are selected, and the two horizontal wells are positive and negative electrodes of electric heating; specifically, the upper horizontal well can be used as the electric heating negative electrode 3, and the lower horizontal well can be used as the electric heating positive electrode 4; at the same time, the upper horizontal well is used as the oil and gas production well (i.e. production well), and fracturing operation is performed on the two horizontal wells to form a fracture network; the fracturing fluid is high salinity brine, and the fracturing fluid is not flowback after the fracturing operation is completed, and the brine (i.e. high salinity brine) remaining in the fracturing fracture network and the formation minerals together form an electric heater;

[0048] Step S2: an oil and gas wellhead device is installed on the wellhead of the upper oil and gas production well (i.e. the upper horizontal well), and a wellhead device is installed on the lower horizontal well;

[0049] Step S3: power operation is performed on the upper and lower heating horizontal wells, the brine remaining in the formation is used as a conductive medium to generate heat, the shale reservoir is directly heated, the temperature of the formation begins to gradually rise, the organic matter in the shale is converted into oil and gas, and production is performed in the upper horizontal well;

[0050] The time T1 of the formation heating and temperature rising stage is calculated, and the power-on time of the formation and the formation temperature change curve are fitted, and there is the following approximate relationship:

[0051]

[0052] wherein a, b can be measured by experiment;

[0053] According to the range of the formation temperature rise ΔT and the electric energy injected into the formation E j and finally the corresponding formation heating time is calculated by the following formula T 1:

[0054]

[0055]

[0056] wherein, T 1 is the time of electric heating of the formation, in min; ΔT the amount of the formation temperature rise, in ℃; E j is the electric energy injected into the formation, in kJ; r is the hole diameter of the horizontal well, in m; d is the distance between the two horizontal wells, in m; U is the voltage between the two horizontal wells, in V; L is the horizontal section length of the horizontal well, in m; I is the current after the formation is electrified, in A; is the electric energy injection time, in min; K is the salinity, in g / L; and a and β can be measured by experiment.

[0057] Step S4: When the formation temperature rises to above 350℃, the organic matter between the two horizontal wells starts to transform and crack to generate oil and gas under the action of heat; it is found by experiment that when the formation temperature is above 350℃, the hydrocarbon generation rate in the formation is relatively fast; the time T2 required for the transformation of the organic matter in the formation to generate a large amount of oil and gas is calculated (if the transformation rate of the organic matter is above 60%, the transformation and cracking time of the organic matter in the formation can be calculated according to the relationship between the temperature at the time of transformation and the time required for transformation); under the condition of high temperature cracking of the organic matter such as cheese root in the formation, for a certain fixed reaction degree, or for different reactions of the same reaction degree, the relationship between the transformation time (i.e. the reaction time) and the formation temperature is as follows:

[0058]

[0059] wherein, d is a constant, and the calculation method is as follows:

[0060]

[0061] wherein, is the reaction time; A is the frequency factor, i.e. the number of molecular collisions per unit time and per unit volume; E is the activation energy; R is the gas constant, 8.3144 J / (mol·K); T is the absolute temperature; c ０ and c represent the original concentration of the reactants and t the concentration of the reactants at time t, respectively.

[0062] According to the temperature of the formation, the conversion time T2 required for the organic matter in the formation to reach a certain degree of conversion can be obtained, and the calculation method is as follows:

[0063]

[0064] Step S5: The oil and gas generated by conversion and cracking migrate to the upper production well under the action of buoyancy through the fracture network; the time required for the oil and gas generated in the formation to migrate to the upper horizontal well is calculated , and the time required for oil and gas seepage considering the action of gravity is calculated:

[0065]

[0066] wherein, d is the distance between the two horizontal wells, in meters; is the viscosity of the oil and gas generated by conversion, in mPa·s; is the porosity of the formation, in decimal; is the permeability of the formation, in μm 2 ; is the pressure gradient drop of the formation, in MP / m; is the density of the oil and gas generated by conversion, in kg / m 3 ; is the acceleration of gravity, in m / s²;

[0067] Step S6: The production mode of the upper horizontal well is to open the upper production well, and the oil and gas generated by heating and conversion in the oil shale reaches the upper horizontal well through the fracture network generated by fracturing under the action of buoyancy, and then is produced. Specifically as follows: open the oil and gas wellhead device of the upper horizontal well, and sequentially perform heat recovery treatment, purification and dust removal treatment, and desulfurization treatment on the mixed fluid discharged from the oil and gas wellhead device, and store the separated oil and gas; calculate the open well production time , and according to the productivity formula of the horizontal well and the amount of oil and gas generated by conversion in the formation G, the calculation formula of , is as follows:

[0068]

[0069] In the formula, J h is a production index of the horizontal well, P is a reservoir pressure; P wf is a bottom hole flowing pressure of the horizontal well;

[0070] Step S7: calculating a total time T of a cycle of the in-situ conversion production of oil shale, i.e., a total of the time of the above four stages:

[0071]

[0072] Further, in step S1: at least two horizontal wells are involved, the upper horizontal well is selected as a production well and a negative electrode of electric heating, the lower well is a positive electrode of electric heating, and a fracturing technique is used to connect the two horizontal wells; further, when the fracturing operation is performed, the fracturing fluid is high salinity brine with a salinity of 3000 mg / L to 10000 mg / L, and after the fracturing operation is completed, the fracturing fluid does not perform a flowback operation. The electrically conductive ions contained in the high salinity brine used in the fracturing operation should also be compatible with the original formation water, without scaling and plugging the formation, and without hindering the subsequent development work. The electric heating well is the upper and lower two horizontal wells, and the fracturing operation is performed on the two horizontal wells at the same time, and the fracturing fractures are distributed in a staggered manner, and the fracture length is greater than 1 / 2 of the well spacing. Compared with the traditional heating method, the formation is heated by the electric current in the brine, and because the range of the distribution of the fracturing fracture network is larger, the heating range is also larger.

[0073] Further, in step S4, alternating current is passed through the upper and lower horizontal wells, and the voltage should be set to 300-900V according to the need for heating speed, and the voltage can be adjusted according to the required heating speed of the oil shale, and the current passes through the heater composed of the external brine in the formation to generate heat; wherein the higher the voltage, the faster the reservoir temperature rises, and the reservoir temperature can reach the target heating temperature faster, and correspondingly, the temperature of the heated shale reservoir can be controlled by controlling the voltage.

[0074] Further, in step S6, when measuring the components of the mixed gas at the gas well mouth, it is necessary to measure the components of the mixed gas for a preset number of times at an interval of a preset time length, the measurement results within the preset number of times are recorded by the control device, and the measurement results are analyzed, when the yield begins to decrease, the voltage can be increased to increase the conversion efficiency to improve the yield.

[0075] The technical scheme of the application can calculate the production cycle of the in-situ conversion process of oil shale. Specifically, the application can calculate the time required in the four stages of the in-situ conversion process of oil shale to calculate the entire production cycle of the in-situ conversion of oil shale.

[0076] Since the horizontal well is horizontally extended, the underground conversion method needs to make a vertical communication channel to make the oil and gas rise to the upper horizontal well under the action of buoyancy.

[0077] Embodiment

[0078] The embodiment uses a production cycle calculation method of in-situ conversion of oil shale by high salinity brine combined with electric heating, which comprises the following steps:

[0079] Step S1: referring to Figs. 1-3 , two double horizontal wells are selected, and the two horizontal wells are respectively the positive and negative electrodes of electric heating. Specifically, the upper horizontal well can be used as the negative electrode 3 of electric heating, and the lower horizontal well can be used as the positive electrode 4 of electric heating. At the same time, the upper horizontal well is also used as the oil and gas production well. Fracturing operations are performed on the two horizontal wells. The fracturing fluid is high salinity brine. After the fracturing operation is completed, the fracturing fluid is not backflowed, and the salinity brine (i.e. high salinity brine) remaining in the fracture network and the formation minerals together form an electric heater.

[0080] Step S2: install an oil and gas wellhead device on the wellhead of the upper oil and gas production well (i.e. the upper horizontal well), and install a wellhead device on the lower horizontal well;

[0081] Step S3: power on the upper and lower horizontal wells. The salinity brine remaining in the formation acts as a conductive medium to generate heat, directly heating the shale reservoir. The time T1 of the formation heating and temperature rising stage is calculated according to the input of electric energy and the change of temperature;

[0082] Step S4: when the formation temperature rises above 350℃, the organic matter between the two horizontal wells begins to convert and crack to generate oil and gas under the action of heat. The time T2 required for the conversion rate of organic matter in the formation to reach 60% is calculated;

[0083] Step S5: the oil and gas generated by conversion and cracking migrates to the upper oil and gas production well under the action of buoyancy. According to the Darcy formula considering the influence of gravity and the real seepage velocity calculation formula, the time T3 required for the oil and gas generated in the formation to migrate to the upper horizontal well is calculated;

[0084] Step S6: open the oil and gas production wellhead device of the upper horizontal well. The mixed fluid discharged from the oil and gas production wellhead device is sequentially subjected to heat recovery treatment, purification and dust removal treatment, and desulfurization treatment. The separated oil and gas is stored. According to the productivity formula of the horizontal well and the amount G of oil and gas generated by conversion in the formation, T4 can be calculated.

[0085] Step S7: calculate the total time T of one cycle of oil shale in-situ conversion production, which is the sum of the above four stage times.

[0086]

[0087] The technical scheme of the embodiment can be used to calculate the production cycle of the in-situ conversion process of oil shale. Specifically, the embodiment uses an electric heating method to convert and crack oil shale. The embodiment selects two horizontal wells as the positive and negative electrodes of electric heating, and uses fracturing to form a fracture network to connect the two horizontal wells to form a passage for oil and gas flow. A wellhead device is installed at the wellhead of the two horizontal wells to seal the continuous passage and the production gas well.

[0088] It should be noted that during fracturing, the fracturing fluid is high salinity brine, which can be obtained from non-potable water produced from other layers. After the fracturing operation is completed, cementing operation and wellhead device installation are also performed on the two horizontal wells. The cementing operation includes installing production casings in the two horizontal wells and installing casing heads on the upper ends of the production casings, which are used to fix the gas wellhead device. In actual production, if the selected horizontal well has already been installed with a production casing, it does not need to be installed again.

[0089] Specifically, in step S3, during the power-on process of the two wells, the voltage between the two wells needs to be controlled to have a reasonable heating rate in the underground, and the current after power-on is calculated by the following formula:

[0090]

[0091] In the formula: r D is the well diameter of the horizontal well, in meters; d L is the distance between the two horizontal wells, in meters; U V is the power-on voltage between the two horizontal wells, in volts; L H is the horizontal section length of the horizontal well, in meters; I I is the current after power-on, in amperes; K T is the salinity, in grams per liter.

[0092] The salinity can directly affect the conductivity of the solution σ , and the conductivity σ and the salinity K have a linear relationship, where α is 1659.5 and β is 2339.3

[0093]

[0094] In the formula: σ σ is the conductivity of the solution, in microsiemens per centimeter; K T is the salinity, in grams per liter.

[0095] In the embodiment, when r D is 0.089 meters, d10 m, the power-on voltage is 300 V, L 50 m, the salinity is 10000 mg / L, the conductivity σ is 14255.7 µS / cm. At this time, the current I is 1 A.

[0096] In this embodiment, when the formation is heated to 350℃, the calculation formula of T1, where a=0.33242, b=0.78916, is 1:200 according to the heating cracking model, the energy required to heat the actual formation is 1254640.988 kJ, and the required time is 69703 minutes, i.e. 49 days.

[0097] In this embodiment, the time required for organic matter conversion when the formation temperature reaches 350℃ and the organic matter conversion rate reaches 60% is calculated:

[0098] At this time, the activation energy E of the reaction is 264 kJ / mol, the frequency factor A is 2.282565×10 15 mol / (L·s), and at this time the formula can be written as:

[0099]

[0100] Then the corresponding conversion time T2 is as follows:

[0101]

[0102] In this embodiment, when the formation temperature reaches 350℃ and the organic matter conversion rate reaches 60%, the time for high-temperature cracking conversion of organic matter in the formation is calculated to be 60.95 days.

[0103] In this embodiment, when the viscosity of the converted oil and gas is 10 mPa·s, the porosity of the formation is 0.1, the permeability of the formation fracture is 272×10 -3 μm 2 , the pressure gradient drop of the formation is 10×10 -3 MP / m, the density of the converted oil and gas is 0.9×10 3 kg / m 3 , the gravitational acceleration is 9.8 m / s²;

[0104]

[0105] The corresponding migration time is 22.6 days.

[0106] In this embodiment, when the horizontal well production index J h is 50 t / d·MPa, the production pressure difference is 1 MPa; the converted oil and gas amount G is 300 t,

[0107]

[0108] The production time of the horizontal well is calculated as T 4 days.

[0109] In this embodiment, as described above, the production cycle is as follows:

[0110] (unit: d)

[0111] In this example, the time for one production cycle of the oil shale in-situ conversion using the technology is 135.55 days.

[0112] In this embodiment, in step S1: the horizontal well includes two upper and lower wells, the upper well is selected as the oil and gas production well, and the fracture network is used to connect the two wells.

[0113] In this embodiment, step S3 includes: step S31: in the initial stage of electric heating, in order to have a higher heating rate, the temperature of the underground oil shale can be quickly raised by appropriately increasing the power supply voltage; step S32: when the formation temperature rises to the conversion critical temperature, the voltage is reduced to save electric energy while maintaining the formation temperature; step S33:

[0114] In actual production, the power supply voltage can be adjusted according to the production of the oil and gas production well, so that the formation temperature is maintained within a reasonable range.

[0115] In this embodiment, in step S5, the oil and gas formed by conversion will gradually seep into the fracture network around the upper oil and gas production well due to the action of buoyancy. These oil and gas enter the wellbore of the oil and gas production well through the fracture network, and are produced using appropriate lifting methods.

[0116] In this embodiment, in step S6, when measuring the components of the mixed gas at the gas wellhead, it is necessary to measure the components of the output oil and gas for a preset number of times at a preset interval. The measurement results within the preset number of times are recorded by the control device, and the measurement results are analyzed. When the production begins to decrease, the power supply voltage can be increased to increase the conversion efficiency and improve the production.

[0117] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for calculating the production cycle of in-situ conversion of oil shale using high-salinity brine combined with electric heating, characterized in that, The process includes the following: Two horizontal wells, one above the other, are selected as the positive and negative electrodes for electric heating, respectively. The upper horizontal well is used as an oil and gas production well. Both horizontal wells are subjected to fracturing operations. High-salinity brine is selected as the fracturing fluid. After the fracturing operation is completed, the fracturing fluid is retained in the fracturing network. An oil and gas wellhead device is installed on the wellhead of the upper horizontal well, and a wellhead device is installed on the lower horizontal well. When the two horizontal wells are energized, the fracturing fluid remaining in the formation acts as a conductive medium to generate heat, which heats the shale reservoir and raises the formation temperature. During the heating process, calculate the time of the temperature rise phase in the electrically heated formation. The formation temperature rise stage represents the period before the organic matter in the oil shale reservoir has undergone thermal decomposition; the time of the thermal decomposition and transformation stage of organic matter in the oil shale reservoir is calculated. ; Calculate the time of the upward migration stage of oil and gas generated by the thermal cracking of organic matter under the action of buoyancy. ; Calculate the production time of the upper horizontal well. ; Calculate the production cycle of in-situ conversion of high-mineralization brine with combined electric heating for oil shale. ; Calculate the duration of the formation temperature rise phase based on the range of formation temperature increase and the electrical energy injected into the formation. ; Range of formation temperature increase ΔT The calculation formula is as follows: Electrical energy injected into the formation E j The calculation formula is as follows: Time of temperature rise in electrically heated formation T The formula for calculating 1 is as follows: In the formula, T 1 represents the time for electrically heating the formation, in minutes; ΔT This represents the increase in formation temperature, expressed in °C. E j The electrical energy injected into the formation is expressed in kJ. r The diameter of a horizontal well is expressed in meters (m). d This is the distance between two horizontal wells, in meters. U The voltage between the two horizontal wells is expressed in V. L This refers to the length of the horizontal section of a horizontal well, in meters (m). I This represents the current after the formation is energized, expressed in amperes (A). The time for electrical energy injection is expressed in minutes. K The value represents the degree of mineralization, expressed in g / L; a, b, α, and β are constants obtained experimentally. During the energization of the two wells, the voltage between them is controlled to ensure a reasonable heating rate underground. The current after energization is calculated using the following formula: conductivity of the solution σ and mineralization K The two equations show a linear relationship, where α is 1659.5 and β is 2339.

3. In the formula: σ The conductivity of the solution is expressed in µS / cm.

2. The method for calculating the production cycle of in-situ oil shale conversion using high-mineralization brine combined with electric heating as described in claim 1, characterized in that, The temperature boundary between the formation temperature rise stage and the organic matter thermal decomposition and transformation stage in the oil shale reservoir is 350°C.

3. The method for calculating the production cycle of in-situ oil shale conversion using high-mineralization brine combined with electric heating as described in claim 1, characterized in that, Time of organic matter thermal cracking and transformation stage in oil shale reservoirs Calculated using the following formula: In the formula, A is the frequency factor, which is the number of molecular collisions per unit time and unit volume; E is the activation energy; R is the gas constant; T is the absolute temperature; c ０ c and c represent the initial concentration of organic matter and the reaction time, respectively. The concentration of reactants at that time; reaction time The following relationship must be satisfied: Where d is a constant, and the calculation method is as follows:

4. The method for calculating the production cycle of in-situ oil shale conversion using high-mineralization brine combined with electric heating as described in claim 1, characterized in that, The time of upward migration of oil and gas generated from the thermal cracking of organic matter under the action of buoyancy The calculation formula is as follows: In the formula, d This is the distance between two horizontal wells, in meters. The viscosity of the converted oil and gas is expressed in mPa·s. The porosity of the formation is a decimal. The permeability of the formation is expressed in μm. 2 ; This represents the pressure gradient drop of the formation, expressed in MPa / m. The density of the converted oil and gas is expressed in kg / m³. 3 ; This is the acceleration due to gravity, expressed in m / s².

5. The method for calculating the production cycle of in-situ oil shale conversion using high-mineralization brine combined with electric heating as described in claim 1, characterized in that, Upper horizontal well production time The calculation formula is as follows: In the formula, This refers to the amount of oil and gas generated during the formation. For horizontal well production index, P This refers to the reservoir pressure. This refers to the bottom flow pressure of a horizontal well.

6. The method for calculating the production cycle of in-situ oil shale conversion using high-mineralization brine combined with electric heating as described in claim 1, characterized in that, The fractures in the two horizontal wells are staggered and the fracture length is greater than 1 / 2 well spacing.

7. The method for calculating the production cycle of in-situ oil shale conversion using high-mineralization brine combined with electric heating according to claim 1, characterized in that, The high-mineralization brine has a mineralization of 3000-10000 mg / L.

8. The method for calculating the production cycle of in-situ oil shale conversion using high-mineralization brine combined with electric heating according to claim 1, characterized in that, When energizing the two horizontal wells, the voltage is controlled between 300 and 900V.

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