Thickened oil saturation measurement experiment device and method based on multi-physics field coupling

Abstract

The invention provides a thick oil saturation degree measurement experiment device and method based on multi-physics field coupling, and belongs to the field of oil and gas field development. The thick oil saturation degree measurement experiment device comprises an oil reservoir simulation system, an oil reservoir development system and a remaining oil content measurement and control system; the three-dimensional sand-packed model wrapping shell is filled with porous medium filler, the interior of the three-dimensional sand-packed model wrapping shell is connected with a formation pressure system through a pipeline, and the exterior of the three-dimensional sand-packed model wrapping shell is connected with a model communication system; the oil reservoir development system comprises an injection supply system, a measurement and control system and a well pattern system. The remaining oil content measurement and control system comprises a pressure guiding detection system, an electric conduction detection system, a heat conduction detection system and a multi-physical field coupling saturation degree measurement system. According to the heavy oil saturation measurement experiment device and method based on multi-physics field coupling, oil saturation quantitative evaluation of the development effect in the heavy oil reservoir development simulation experiment process is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas field development, and in particular to a heavy oil saturation measurement experimental device and method based on multi-physical field coupling. BACKGROUND

[0002] Heavy oil physical simulation development experiment is a key research method for heavy oil reservoir development. For conventional heavy oil thermal recovery development methods such as huff and puff, displacement, gravity assisted gravity drainage, etc., the simulation experiment devices mainly cover one-dimensional sand filling pipe models, two-dimensional sand filling plate models and three-dimensional sand filling body models, etc. These models simulate the reservoir porous medium characteristics by filling quartz sand or natural cores.

[0003] At present, the above-mentioned sand filling model is often used in the following methods when testing the oil saturation inside: direct sampling method, model external auxiliary detection method and probe indirect testing method. The direct sampling method is mainly used in one-dimensional sand filling models, and the saturation is identified by weighing the sampling points along the pipe column, but each sampling will seriously interfere with the oil and water distribution in the porous medium, resulting in large fluid loss. The model external auxiliary detection method is suitable for two-dimensional sand filling models and small size core models, such as using light transmission ability combined with Beer-Lambert law to determine the oil saturation of two-dimensional model, but when the model is thickened and the light transmission is poor, it cannot be applied; using CT, nuclear magnetic resonance and other means to monitor the saturation evolution of one-dimensional small size core model, but there are problems such as small monitoring range and poor model size adaptability.

[0004] The probe indirect testing method is often used in three-dimensional sand filling models and large-scale reservoir simulation devices. The "invention patent CN01123944.1 oil saturation measurement method and measurement probe" uses a conductive probe to test the oil saturation of low viscosity oil, and the injected foreign agent can easily strip the thin oil from around the probe to trigger a change in electrical conductivity to test the oil saturation. Due to the high content of asphaltene and gum in heavy oil, a heavy oil adhesion layer is formed on the surface of the probe, which hinders the test of the electrical conductivity of the probe. In order to overcome the influence of heavy oil adhesion, a temperature-sensitive probe is used to test the remaining oil saturation, but the large-scale monitoring of temperature has low measurement accuracy for the simulation device in the laboratory, and cannot accurately depict the oil saturation in the dominant water drive channel during development.

[0005] In summary, although there are many oil saturation test methods, the accurate quantitative identification method for heavy oil saturation is not perfect. The previous saturation identification method mainly refers to the electrical conductivity coefficient of low viscosity and low adsorption crude oil or a wide range of oil-water distribution evaluation, which cannot adapt to the accurate identification of heavy oil saturation. Due to the limitation of dynamic acquisition data, there is a persistent saturation change missing problem in the development process, and a full-process saturation change correlation method needs to be constructed after the end of different development stages. At the same time, the accurate description of saturation in different regions and time periods and the division of the mining potential partition classification are difficult, and the mining potential region after saturation identification needs to be highlighted. SUMMARY

[0006] The purpose of the present application is to provide a heavy oil saturation measurement experimental device and method based on multi-physical field coupling, which solves the problems of the existing oil saturation test method in the accurate quantitative identification of heavy oil, the missing of saturation change data in development, and the difficulty of saturation description in different regions and time periods and the division of mining potential partition classification.

[0007] To achieve the above purpose, the present application provides a heavy oil saturation measurement experimental device based on multi-physical field coupling, which comprises an oil reservoir simulation system, an oil reservoir development system and a remaining oil content measurement and control system

[0008] The oil reservoir simulation system comprises a three-dimensional sand filling model package shell, the inside of which is filled with a porous medium filler, the inside of the three-dimensional sand filling model package shell is connected with a formation pressure system through a pipeline, and the outside of the three-dimensional sand filling model package shell is connected with a model communication system.

[0009] The oil reservoir development system comprises an injection supply system, a metering and control system and a well pattern system, the output end of the injection supply system is connected with the metering and control system through a pipeline, and the injection supply system is connected with the well pattern system through a second six-way valve.

[0010] The remaining oil content measurement and control system comprises a pressure guide detection system, an electrical conductivity detection system, a thermal conductivity detection system and a multi-physical field coupling saturation determination.

[0011] Preferably, the supply system comprises a double-cylinder plunger displacement pump, a liquid supply intermediate container, a displacement gas cylinder, a gas flow control meter, a mixed displacement system generator and a steam generator, the output end of the double-cylinder plunger displacement pump is connected with the liquid supply intermediate container through a liquid distribution three-way valve, the output end of the liquid supply intermediate container is connected with the inlet of a first six-way valve, the output end of the displacement gas cylinder is connected with the gas flow control meter, the output end of the gas flow control meter is connected with another inlet of the first six-way valve, the input end of the mixed displacement system generator is connected with the outlet of the first six-way valve, the output end of the mixed displacement system generator is connected with the inlet of a second six-way valve, the output end of the steam generator is connected with another inlet of the second six-way valve, and another outlet of the first six-way valve is connected with the input end of the second six-way valve.

[0012] Preferably, the metering and control system comprises a first measuring cylinder, a first electronic balance, a second measuring cylinder and a second electronic balance, the first measuring cylinder is connected with the outlet of the second six-way valve, the lower end of the first measuring cylinder is provided with the first electronic balance, and the output end of the oil reservoir simulation system is connected with the second measuring cylinder through a back pressure valve, and the lower end of the second measuring cylinder is provided with the second electronic balance.

[0013] Preferably, the well pattern system comprises a wellbore structure and a sand prevention spring structure, the wellbore structure comprises a wellbore mechanism and a well site fixing mechanism, and the well site fixing mechanism realizes the material exchange between the external fluid and the oil reservoir simulation system.

[0014] Preferably, the pressure detection system comprises a pressure detection array and an electronic pressure gauge, the electric field detection system comprises a high-precision direct current power supply, an electric field controller and a potential detection array, and the heat detection system comprises a bottom plate heating device, a temperature detection array and a heat flux measurement device.

[0015] The method for measuring heavy oil saturation based on multi-physical field coupling comprises the following steps

[0016] S1, constructing an oil reservoir physical model, selecting a suitable sand prevention spring structure according to the diameter of the porous medium filler and the impact force of the external fluid;

[0017] S2, synchronously collecting multiple parameters, collecting the pressure conductivity coefficient, the electric conductivity coefficient and the heat conductivity coefficient in the pressure detection system, the electric field detection system and the heat detection system respectively;

[0018] S3, coupling multiple physical fields to calculate the heavy oil saturation, based on the physical property changes derived from the three physical fields of the pressure conductivity coefficient, the electric conductivity coefficient and the heat conductivity coefficient, and using the pressure-conductivity-heat identification of the saturation for correction and supplement;

[0019] S4, verifying the heavy oil saturation, calculating the experimental oil production and the mass deviation value of the oil production calculated by the saturation, if the calculated mass deviation value is within the allowable error range, it is considered that the calculated value conforms to the law of conservation of mass and has higher accuracy.

[0020] Preferably, the spring screen expression of the sand prevention spring structure is:

[0021]

[0022] Wherein, l0 is the pitch of the spring, d s is the diameter of the spring wire, θ is the included angle between the main streamline direction and the axial direction of the spring, k is the radial stiffness coefficient of the spring, n is the number of coils of the spring, and D is the diameter of the sand.

[0023] Preferably, the pressure guide coefficient expression is:

[0024]

[0025] Wherein, k1 and k2 are the pressure guide coefficient undetermined coefficients, φ is the porosity in the porous medium, K is the permeability, S o is the oil saturation, c t is the comprehensive compression coefficient of the core;

[0026] The electrical conductivity coefficient expression is:

[0027]

[0028] Wherein, k3, k4 and k5 are the saturation fluid porous medium electrical conductivity property undetermined coefficients related to the porous medium, R w is the resistivity of the formation water;

[0029] The thermal conductivity coefficient expression is:

[0030]

[0031] Wherein, c p is the specific heat capacity, Q is the internal heat source, ρ is the density, T is the temperature, t is the time, and λ is the thermal conductivity.

[0032] Preferably, the saturation calculated oil production expression is:

[0033]

[0034] Wherein, wherein, ρ o is the density of the crude oil, S oi is the oil saturation, V i,j,k is the apparent volume of the porous medium in the model.

[0035] Therefore, the application adopts the above-mentioned heavy oil saturation measurement experimental device and method based on multi-physical field coupling, and the technical effects are as follows:

[0036] 1. Strong structural stability, can be repeatedly disassembled and used: the sand filling model shell is made of polyether ether ketone material which is resistant to temperature and pressure and insulation, can maintain the integrity and stability of the model in high temperature and high pressure environment, considering the demand of repeated disassembly and use, so that the experimental device can be used for many times, reducing the experimental cost.

[0037] 2. Comprehensive heavy oil saturation measurement experimental device: a comprehensive measurement system containing flow field, electric field and temperature field and other multiple physical fields is constructed, which can obtain parameters of multiple physical fields at the same time, and through the coupling analysis of multiple physical fields, the efficient and accurate measurement of heavy oil saturation is realized.

[0038] 3. Suitable for heavy oil reservoir of thermal development mode: it can accurately measure the heavy oil saturation, and also can measure the effective action distance of injected hot fluid in the thermal recovery process, which provides important data support for the optimization of thermal development mode. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is the logic flow chart of the application based on multi-physical field coupling heavy oil saturation measurement experimental device and method;

[0040] Figure 2 It is the device connection diagram of the reservoir simulation system and the reservoir development system;

[0041] Figure 3 It is the three views of the three-dimensional sand filling package shell in the reservoir simulation system;

[0042] Figure 4 It is the logic diagram of saturation inversion calculation of each physical field;

[0043] Figure 5 It is the oil saturation distribution field diagram generated by pressure field inversion;

[0044] Figure 6 It is the oil saturation distribution field diagram generated by electric field inversion;

[0045] Figure 7 It is the oil saturation distribution field diagram generated by temperature field inversion;

[0046] Figure 8 It is the oil saturation distribution field diagram generated by multi-physical field collaborative inversion.

[0047] REFERENCE NUMERALS

[0048] 10, double cylinder piston displacement pump; 11, three-way valve; 12, liquid supply intermediate container; 13, displacement gas cylinder; 14, gas flow control meter; 15, first six-way valve; 16, mixed displacement system generator; 17, steam generator; 18, second six-way valve; 19, first measuring cylinder; 20, first electronic balance; 21, pressure detection array; 22, potential detection array; 23, temperature detection array; 24, three-dimensional sand filling model; 25, back pressure valve; 26, single cylinder piston confining pressure pump; 27, second measuring cylinder; 28, second electronic balance; 29, data processing computer. DETAILED DESCRIPTION

[0049] The technical solutions of the present application are further described below by means of the accompanying drawings and examples.

[0050] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those with ordinary skills in the art to which the present application belongs.

[0051] Example 1

[0052] As shown in the accompanying drawings, Figure 1 The present application provides a multi-physical field coupling heavy oil saturation measurement experimental device and method. The device is based on a reservoir simulation system and its attached reservoir development system, and takes a remaining oil content measurement and control system as the core, and a heavy oil saturation identification process as an expanded comprehensive reservoir simulation development evaluation method.

[0053] As shown in the accompanying drawings, Figures 2-3 The device includes a reservoir simulation system, a reservoir development system, and a remaining oil content measurement and control system. The reservoir simulation system includes a three-dimensional sand filling model package shell, a porous medium filler, a formation pressure system, and a model communication system.

[0054] The three-dimensional sand filling package shell is made of polyether ether ketone material, which can maintain good mechanical properties and dimensional stability at high temperatures, and can adapt to different temperature conditions in the physical simulation of reservoir development. The tensile strength of the material can reach more than 90 MPa, and the bending strength can reach 150 MPa. In a high-pressure environment, the model can maintain its integrity and stability, and is not prone to deformation or damage.

[0055] The porous medium filler is composed of a quartz particle skeleton and a clay mineral interstitial material. The clay mineral needs to adhere to the surface of the quartz sand, and mainly relies on an ultrasonic oscillator suspended in a NaOH alkaline solution to promote the mixing of the clay mineral and the quartz particle porous medium filler.

[0056] The formation pressure system is composed of a back pressure valve 25 and a single cylinder piston confining pressure pump 26. The single cylinder piston confining pressure pump 26 supplies distilled water to the back pressure valve 25 to maintain a certain level of formation starting pressure, thereby preventing the internal fluid of the reservoir simulation system from easily leaking out of the output end.

[0057] The model communication system is composed of a through-going wellbore in the shell and a fixed valve outside the shell. The through-going wellbore can provide a communication channel between the reservoir system and the outside world for the injection-production well and the saturation measurement and control system, and prevent the quality loss in the reservoir.

[0058] The supply system includes a double-cylinder plunger displacement pump 10, a liquid supply intermediate container 12, a displacement gas cylinder 13, a gas flow control meter 14, a mixed displacement system generator 16 and a steam generator 17. The output end of the double-cylinder plunger displacement pump 10 is connected to the liquid supply intermediate container 12 through a liquid distribution three-way valve 11, the output end of the liquid supply intermediate container 12 is connected to the inlet of a first six-way valve 15, and the injection energy of each injection component is supplied. The output end of the displacement gas cylinder 13 is connected to the gas flow control meter 14, the output end of the gas flow control meter 14 is connected to another inlet of the first six-way valve 15, and the gas is injected into the reservoir simulation system at a constant speed and pressure. The input end of the mixed displacement system generator 16 is connected to the outlet of the first six-way valve 15, and the output end of the mixed displacement system generator 16 is connected to the inlet of a second six-way valve 18, and the two-phase mixed fluid such as emulsion / foam is generated in the porous medium and then injected into the reservoir simulation system. The output end of the steam generator 17 is connected to another inlet of the second six-way valve 18, and the high-temperature steam is directly injected into the reservoir simulation system. Another outlet of the first six-way valve 15 is connected to the input end of the second six-way valve 18, and each component fluid is directly injected into the reservoir simulation system.

[0059] The measurement and control system includes a first measuring cylinder 19, a first electronic balance 20, a second measuring cylinder 27 and a second electronic balance 28. The first measuring cylinder 19 is connected to the outlet of the second six-way valve 18, and the first electronic balance 20 with a base heating function is arranged at the lower end of the first measuring cylinder 19 to simulate the fluid production change of the thickened oil reservoir during the huff and puff development or the fluid input end of the other adjacent fluid. The output end of the reservoir simulation system is connected to the second measuring cylinder 27 through a back pressure valve 25, and the second electronic balance 28 is arranged at the lower end of the second measuring cylinder 27 to simulate the fluid production change of the thickened oil reservoir during the development or the displacement of the fluid input end far away from the fluid.

[0060] The well pattern system includes different types of wellbore structures and sand prevention spring structures, and the distribution of injection-production wells is designed and arranged according to various well pattern structures, such as five-point method, seven-point method or nine-point method well pattern. The wellbore structure is mainly divided into a wellbore mechanism and a well position fixing mechanism, wherein the well position fixing mechanism is a threaded fastening structure which is closely fitted with the through-going wellbore in the shell, and the purpose of the branch line is to realize the exchange of external fluid and substances in the reservoir simulation system. The selection of the sand prevention spring structure needs to consider the influence of the particle size of the porous medium filler and the impact force generated by the injected fluid, and the spring screen expression of the sand prevention spring structure is:

[0061]

[0062] wherein l0 is the pitch of the spring, d s is the diameter of the spring wire, theta is the angle between the main streamline direction and the axial direction of the spring, k is the radial stiffness coefficient of the spring, n is the number of coils of the spring, and D is the diameter of the sand.

[0063] When the spring is pressed by an external force F, according to Hooke's law F=kx, the diameter of the spring wire can be expressed as d s , the spring spacing is compressed by an amount x, the number of coils of the spring is n, and the actual spacing l between the coils after the spring is compressed can be expressed as:

[0064]

[0065] To achieve the purpose of effective sand prevention, it is required that l<D, wherein D is the diameter of the sand. By selecting the radial stiffness coefficient k and the initial spacing l0 of the spring, it can be ensured to a certain extent that the sand prevention requirement can still be met even in the case of side impact of rock particles.

[0066] The remaining oil content measurement and control system comprises a pressure guiding detection system, an electrical conductivity detection system, a heat conduction detection system and a multi-physical field coupling saturation determination.

[0067] The pressure guiding detection system comprises a pressure detection array 21 and an electronic pressure gauge, which can record pressure data in real time. The injection supply system is adjusted to supply fluid for developing heavy oil. The pressure fluctuation is obtained through the pressure detection array. The pressure guiding coefficient is calculated according to the diffusion equation of pressure propagation:

[0068]

[0069] The discretization of the above diffusion equation is as follows:

[0070]

[0071] The pressure guiding coefficient of each phase fluid in the porous medium is determined by using a pre-prepared small-size three-dimensional sand filling model 24 of the saturated water phase fluid to determine the pressure guiding coefficient when the saturated water phase fluid is saturated. The backward small-size three-dimensional sand filling model 24 is used to inject oil and water two-phase fluids in equal proportions until the liquid is stably discharged to determine the pressure guiding coefficient under different saturations. The correlation function of the pressure guiding coefficient and the oil saturation is constructed as follows: o Under the comprehensive influence of the porosity phi and the permeability K in the porous medium, the correction of the pressure guiding coefficient in the porous medium can be expressed as:

[0072]

[0073] Wherein, k1, k2 are the pressure coefficient of the pending coefficient, need to match the small size of three-dimensional sand filling model experiment data fitting; φ is the porosity of the porous medium, K is the permeability, S0 is the oil saturation, ct is the core comprehensive compression coefficient.

[0074] The conductive detection system includes a high-precision direct current power supply, an electric field controller and a potential detection array 22, and can determine an oil saturation field map based on an electric field through a conductive coefficient interpolation algorithm. The high-precision direct current power supply can provide a stable adjustable voltage, and the output voltage range is 0-100 V, and the precision is 0.1 V. The electric field controller can accurately control the voltage size and direction output by the direct current power supply according to the measurement requirements, and form a uniform or specific distribution electric field inside the sand filling model. The electrodes of the potential detection array 22 are cylindrical bodies made of corrosion-resistant and conductive platinum-iridium alloy material, and the electrodes are installed on each side and bottom of the three-dimensional sand filling wrapping shell through the through-hole wellbore in the shell, forming a three-dimensional electrode array, and the electrodes are connected with the external circuit through wires for measuring voltage signals.

[0075] The conductive coefficient interpolation algorithm determines the oil saturation field map based on the electric field. The electrode array system applies current to different electrode pairs and measures the voltage between the corresponding electrode pairs. According to the inverse relationship between resistivity and conductive coefficient, the conductive coefficient can be expressed as:

[0076]

[0077] Wherein, I is the current, S is the contact area between the electrode and the porous medium, U is the voltage, and l is the electrode spacing.

[0078] The number of conductive coefficients obtained is subject to the number of electrode arrays, and only discrete data points can be obtained. Eight adjacent electrode measurement points in the micro-grid unit of the sand filling model are calculated, and the coordinates and conductive values of the eight points are calculated through a trilinear interpolation formula to obtain the conductive coefficient σ(x, y, z) of the grid unit. According to the color and transparency mapping of the conductive coefficient value, a conductive coefficient distribution map is formed in the three-dimensional sand filling model.

[0079] The oil saturation field map based on the electric field is based on the difference in conductive characteristics of oil, gas and water, and establishes a corresponding relationship between the conductive coefficient and the fluid type: under certain experimental conditions, the area with a conductive coefficient greater than σ1 can be judged as water, the area with a conductive coefficient less than σ2(σ2<σ1) can be judged as oil, and the area with a conductive coefficient close to zero can be judged as gas. Finally, according to the above corresponding relationship between the conductive coefficient and the fluid type, the generated conductive coefficient distribution map is divided into oil saturation values.

[0080] The numerical division of oil saturation in porous media is based on Archie formula. Under the comprehensive influence of porosity φ and permeability K in porous media, the modified conductivity coefficient in porous media can be expressed as:

[0081]

[0082] wherein k3, k4 and k5 are the undetermined coefficients of saturated fluid porous media conductivity properties related to porous media, R w is the resistivity of formation water.

[0083] The heat conduction detection system includes a bottom heating device, a temperature detection array 23 and a heat flow density measuring device.

[0084] The temperature detection array 23 adopts a distributed temperature-sensitive optical fiber temperature sensor, which realizes temperature measurement by using the back Raman scattering effect of light in the optical fiber, and the temperature measurement accuracy can reach ±0.2℃, and the spatial resolution can reach 0.5m. The optical fiber is laid in a grid shape inside the main body of the three-dimensional sand filling model, on the four side surfaces, the bottom surface and different height planes inside.

[0085] The bottom heating device is composed of a heating bottom plate, a temperature controller and a heat insulation layer. The heating bottom plate adopts a high-temperature-resistant stainless steel plate with a thickness of 10mm, and the resistance heating wire is uniformly embedded inside, which can provide stable heat output. The heating bottom plate is installed on the bottom surface of the main body of the three-dimensional sand filling model 24 and closely adheres to the model to ensure that the heat can be effectively transmitted to the inside of the model. The temperature controller monitors the temperature in real time through the temperature sensor installed on the heating bottom plate and automatically adjusts the heating power according to the set value. The heat insulation layer adopts ceramic fiber material with good heat insulation performance and high temperature resistance, with a thickness of 20mm, which is laid below and around the heating bottom plate to prevent heat loss and improve heating efficiency.

[0086] The heat flow density measuring device is a heat flow density meter based on thin film sensor technology installed outside the four side surfaces and the bottom surface of the three-dimensional sand filling model 24, which is connected with the data processing computer 29 through data line.

[0087] The oil saturation field map based on temperature field is based on the differences in thermal conductivity and specific heat capacity of oil, gas and water. The heat transfer properties of different regions are directly related to the multiphase saturation of the region. Based on the mixing theory, the relationship between the thermal conductivity λ mix and the specific heat capacity c mix of the mixed fluid and the oil saturation S o can be obtained by weighted average method:

[0088] λ mix =S o λ o +S w λ w +Ss λ s ;

[0089] c mix =S o c o +S w c w +S s c s ;

[0090] wherein, λ o , λ w , λ s are thermal conductivity coefficients of oil phase, water phase and solid phase in turn.

[0091] According to Fourier heat conduction law, the heat conduction equation in the three-dimensional sand filling model is established:

[0092]

[0093] wherein, c p is specific heat capacity, Q is internal heat source, ρ is density, T is temperature, t is time, and λ is thermal conductivity coefficient.

[0094] After the bottom heating device is turned on, the entire model is heated from the bottom, and the real-time temperature data of each area after heating is obtained by relying on the temperature-sensitive fiber temperature sensor array. The thermal conductivity coefficient at each point is calculated according to the above Fourier heat conduction equation, and the thermal conductivity coefficient λ(x, y, z) of the grid unit in the three-dimensional sand filling model 24 is calculated by using the eight adjacent temperature measurement data of the micro-grid unit through the trilinear interpolation formula. According to the color and transparency mapping of the heat transfer coefficient value, the thermal conductivity coefficient distribution map is formed in the three-dimensional sand filling model.

[0095] The thermal conductivity coefficient of each phase fluid in the porous medium is determined by using the pre-prepared small-size three-dimensional sand filling model 24 of the saturated water phase fluid to measure the heat transfer coefficient when the oil saturation is 0. The small-size three-dimensional sand filling model 24 is injected with oil and water in equal proportions until the stable liquid is discharged to measure the thermal conductivity coefficient at different saturations, and the correlation function λ=f(S o ) of the thermal conductivity coefficient-oil saturation is constructed.

[0096] The heavy oil saturation recognition process is based on the physical property changes derived from the three physical fields of thermal conductivity coefficient, electrical conductivity coefficient and thermal conductivity coefficient. The saturation recognition of thermal conductivity-electrical conductivity-thermal conductivity is corrected and supplemented.

[0097] In the distribution field of the pressure conductivity coefficient, in the area where the pressure conductivity coefficient is obviously higher, it means that the flow resistance of the fluid is obviously lower and cannot weaken the injection pressure, so it can be determined that this area is a strong sweep development area, the water phase saturation is higher, the space occupied by the water phase fluid is more, and the difference in conductivity performance is more obvious after the electric field is applied. Therefore, the saturation identified based on the synergy of the pressure field and the electric field can be carried out in the low oil saturation area (i.e., the "swept area").

[0098] The synergy of the pressure field and the electric field in the oil saturation identification, when the difference between the single-point saturation values obtained by the pressure conductivity coefficient and the conductivity coefficient inversion is less than 5% in the efficient sweep area, it can be considered that the two field values match well, and the oil saturation value at the point can be calculated by using the average value. When the oil saturation measured by the pressure conductivity coefficient is lower than the value measured by the conductivity coefficient and the difference between the two is more than 5%, the electrode probe at the point is surrounded by heavy oil and cannot accurately measure the oil saturation around it. At this time, the oil saturation measured by the pressure conductivity coefficient is more accurate.

[0099] The pressure conductivity coefficient dominates the calculation of the oil saturation, and the conductivity coefficient assists the calculation, and the weight coefficients of the two need to be determined. The first weight ω1 of the pressure conductivity coefficient can be preset to 0.7-0.8, and the weight ω2 of the conductivity coefficient can be preset to 0.2-0.3. A small-size three-dimensional sand filling model 24 is used for verification, and the weight coefficients are continuously adjusted to minimize the error.

[0100] When the oil saturation measured by the pressure conductivity coefficient is higher than the value measured by the conductivity coefficient and the difference between the two is more than 5%, the electrode probe at the point has more continuous initial saturated water channels during the saturation of oil, and its surface is not adhered to heavy oil, and its conductivity is easy to be much higher than the pressure conductivity performance. The oil saturation in the micro-pore channel is accurately described, but the action distance is slightly enlarged, and the oil saturation value fluctuates greatly. The saturation corresponding to the intersection point of the pressure conductivity coefficient expression and the conductivity coefficient expression is the oil saturation value at each point.

[0101] In the area where the oil saturation measured by the conductivity coefficient is obviously low, the electrode probe is surrounded by heavy oil with strong adhesion, and the resistance is large, which cannot truly reflect the change of the flow field around it. Therefore, in the area where the electric conductivity is insufficient, the oil saturation measured by the electric field needs to be ignored, and the synergy of the pressure field and the temperature field can be used to identify the oil saturation in the high oil saturation area (i.e., the "unswept area") with weak development effect.

[0102] The oil saturation of the pressure field and the temperature field is identified. When the single-point saturation value difference obtained by the inversion of the pressure conductivity coefficient and the thermal conductivity coefficient is less than 5% in the efficient swept area, it can be considered that the two field values match well, and the oil saturation value at the point can be calculated by using the average value. When the oil saturation measured by the pressure conductivity coefficient is lower than the value measured by the thermal conductivity coefficient, and the difference between the two is more than 5%, the pressure-sensitive probe at the point detects a low-width water drive dominant channel. Since the channel is too narrow, the oil saturation value around it fluctuates greatly, and the measurement accuracy of the temperature is difficult to effectively cover. At this time, the oil saturation calculated by the pressure conductivity coefficient is more accurate.

[0103] The pressure conductivity coefficient dominates the calculation of the oil saturation, while the thermal conductivity coefficient assists in the calculation. The weight coefficients of the two need to be determined. The second weight ω3 of the pressure conductivity coefficient can be preset to 0.5-0.7, and the weight ω4 of the thermal conductivity coefficient can be preset to 0.3-0.5. A small-size three-dimensional sand filling model 24 is used for verification. By continuously adjusting the weight coefficients, the error is minimized.

[0104] When the oil saturation measured by the pressure conductivity coefficient is higher than the value measured by the thermal conductivity coefficient, and the difference between the two is more than 5%, the heavy oil around the pressure-sensitive probe is replaced by the injected fluid, and the pressure fluctuation is small and cannot accurately reflect the change of the oil saturation. Therefore, the saturation corresponding to the intersection point of the pressure conductivity coefficient and the thermal conductivity coefficient is the oil saturation value at each point.

[0105] The pressure field (or "flow field"), electric field and temperature field used in the swept area and the unswept area are finally drawn into the oil saturation field map to express the zonation condition of the remaining oil. The volume of each microgrid unit is multiplied by its saturation, and then the change of the oil saturation in each microgrid is summarized into the change of the oil phase mass in the porous medium by using the mass conservation method, which is expressed as:

[0106]

[0107] wherein ρ o is the density of the crude oil, S oi is the oil saturation, and V i,j,k is the apparent volume of the porous medium in the model.

[0108] The logic of the saturation inversion calculation of each physical field is shown in Figure 4 The experimental oil production m oe recorded during the development process is compared with the oil production m oc calculated by using the saturation. If the calculation mass deviation value is within the allowable error range (less than 5%), it is considered that the calculation value meets the mass conservation law and has high accuracy. If the calculation mass deviation exceeds the allowable error range value, the four weight coefficients of the pressure conductivity coefficient, the electrical conductivity coefficient and the thermal conductivity coefficient are adjusted to verify the experimental measured oil production m oe.

[0109] The 3D reservoir simulation device and its development system are the equipment basis for the identification of residual oil saturation. Figure 2 As shown, the various devices are connected in sequence. A completed wellbore with a screen, a pressure detection array 21, a potential detection array 22, and a temperature detection array 23 are successively installed within the three-dimensional sandfill model 24. Floor heating devices are evenly distributed across the bottom of the model. To accommodate heavy oil thermal recovery applications, two parallel vertical wells are located in the center of the top of the three-dimensional sandfill model 24.

[0110] Each wall of the three-dimensional sand filling model 24 is paved with clay and ceramic sheets for sealing and heat insulation. Thereafter, the mass of the pre-configured quartz particle skeleton-clay mineral filling mixture is measured as m s , poured into a container filled with heavy oil and mixed thoroughly to form oil sand. The solid particles serve as the rock skeleton, and their mass can be weighed as the total mass of the oil sand m t , filling the oil sands into a three-dimensional model with insulation and monitoring functions.

[0111] A single-cylinder plunger confining pressure pump 26 is used to increase the pressure of the back pressure valve 25 to 3.5 MPa. Then, the injection supply system is used to continue saturating the 3D model with heavy oil until the fluid produces oil stably. During this process, the permeability is measured to be 1572 mD. The mass of heavy oil in the oil sand is divided by its density to obtain its oil-bearing volume V. o The porosity φ is calculated by dividing the oil-containing volume by the total volume of the reservoir's internal voids. The volume of the oil phase fluid is 39,763 mL, resulting in a porosity of approximately 0.32 and a saturated oil mass of 36,582 g. After saturation, the sample was placed in a thermostat for at least 144 hours to allow for pressure equilibrium within the reservoir.

[0112] When 0.5 PV of 260°C steam is injected into the reservoir from the injection wellhead, the steam chamber fully develops, and its internal oil saturation changes significantly. During the development process, the pressure readings inside the reservoir are detected by a pressure-sensitive probe array. The pressure conductivity is calculated using the diffusion equation for pressure propagation. The pressure is then discretized to obtain a distribution map of the pressure conductivity. The relationship between the pressure conductivity and oil saturation is constructed using data from 24 experiments on a small-scale three-dimensional sandfill model:

[0113]

[0114] Where K, μ, and c t Expressed as permeability, viscosity and comprehensive compressibility respectively. Using the above formula, the original pressure conductivity distribution field map can be transformed into an oil saturation field map based on pressure conductivity, such as Figure 5 shown.

[0115] The high-precision DC power supply and electric field controller are connected to the analog reservoir, and the size and direction of the voltage output are controlled. During the development process, the electrical conductivity coefficient is obtained by measuring the voltage between the corresponding electrode pairs, and then the discrete data points of the electrical conductivity coefficient are interpolated to obtain the electrical conductivity coefficient distribution field map. Since the electrical conductivity coefficients of water, oil and gas inside the model decrease in turn, the relationship between the electrical conductivity coefficient and the oil saturation is constructed according to the Archie formula:

[0116]

[0117] wherein, R w is the resistivity of the formation water. By using the above formula, the original electrical conductivity coefficient distribution field map can be converted into an oil saturation field map based on the electrical conductivity, as shown in Figure 6 .

[0118] After the steam flooding displacement stage is completed, the heating bottom plate and the temperature controller are used to heat from the bottom of the three-dimensional sand filling model 24, and the temperature change is monitored by using the temperature-sensitive optical fiber temperature sensor array. After the development is completed, the bottom plate heating device is turned on to heat the entire model from the bottom, the real-time temperature data of each region after heating is obtained by relying on the temperature-sensitive optical fiber temperature sensor array, and the thermal conductivity coefficient at each point is calculated according to the Fourier heat conduction equation:

[0119]

[0120] wherein, λ, c are the thermal conductivity coefficient and the specific heat capacity respectively.

[0121] And the thermal conductivity and the specific heat capacity at each node are caused by the differences in the thermal conductivity and the specific heat capacity of oil, gas and water, which can be expressed as:

[0122] λ mix =S o λ o +S w λ w +S s λ s ;

[0123] c mix =S o c o +S w c w +S s c s ;

[0124] The thermal conductivity coefficient λ(x, y, z) of the grid cell in the three-dimensional sandpack model 24 is calculated by a trilinear interpolation formula using eight adjacent temperature measurements of the grid cell, and a color and transparency mapping is set according to the heat transfer coefficient value to form a thermal conductivity coefficient distribution map in the three-dimensional sandpack model 24. The relationship function of the thermal conductivity coefficient and the oil saturation is constructed by fitting the data of the small-size three-dimensional sandpack model experiment:

[0125]

[0126] Using the above formula, the original thermal conductivity coefficient distribution field map can be converted into an oil saturation field map based on the thermal conductivity, as shown in Figure 7

[0127] The oil saturation fields inverted from the conductivity, electrical conductivity and heat transfer show obvious differences, reflecting the sensitivity differences of each physical field to the oil saturation value. Therefore, in the areas where the saturation differences of the three physical fields are large, the reasons for the saturation measurement differences need to be considered and the measured oil saturation needs to be corrected accordingly. The detailed correction process is as follows:

[0128] The area with obviously higher conductivity and conductivity coefficients is a high-conductivity development area, and the steam condensate occupies more pore space and has a lower oil saturation value. The oil saturation inverted from the conductivity and conductivity coefficients can be determined together. When the difference between the single-point saturation values inverted from the conductivity and conductivity coefficients is less than 5%, it can be considered that the two values match, and the average value of the oil saturation at the point can be calculated. When the oil saturation measured by the conductivity coefficient is lower than that measured by the conductivity coefficient and the difference between them is more than 5%, the electrode probe at the point is mostly surrounded by heavy oil and cannot accurately measure the oil saturation around it. In this case, the oil saturation inverted by the conductivity coefficient is more accurate. In the area where the oil saturation inverted by the conductivity coefficient is significantly lower than that inverted by the conductivity coefficient, the first weight ω1 of the conductivity coefficient can be pre-set to 0.7-0.8, and the weight ω2 of the conductivity coefficient can be pre-set to 0.2-0.3. The small-size three-dimensional sandpack model is used for verification. After several trial calculations, it is found that when ω1 and ω2 are 0.75 and 0.25 respectively, the average error value of the inversion result is the smallest, which can be used as the optimal weight value. In the area where the oil saturation inverted by the conductivity coefficient is significantly higher than that inverted by the conductivity coefficient, the electrode probe at the point has more continuous initial saturated water channels during the saturation of oil, and there is no heavy oil adhesion on its surface, so its electrical conductivity is much higher than its conductivity. The oil saturation in the micro-pore channel is accurately described, and the saturation corresponding to the intersection point of the conductivity coefficient-oil saturation relationship and the conductivity coefficient-oil saturation relationship is the oil saturation value at each point.

[0129] ​In the area where the conductivity coefficient is obviously lower than the saturation, the electrode probe is surrounded by the thick oil with strong adhesion, and the resistance is large, which cannot truly reflect the change of the flow field around it. Therefore, the complementary method is required to supplement the accurate determination of oil saturation in the area with insufficient conductivity. Therefore, the cooperative identification based on the pressure field and the temperature field can be used in the area with large development effect and conductivity characteristics. When the difference between the single-point saturation values obtained by the conductivity coefficient and the thermal conductivity coefficient is less than 5%, it can be considered that the two field values match well, and the oil saturation value at the point can be calculated by the average value; in the area where the oil saturation measured by the conductivity coefficient is lower than the value measured by the thermal conductivity coefficient and the difference between them is more than 5%, the low-width water drive dominant channel is detected by the pressure-sensitive probe at the point, and the oil saturation value around it fluctuates greatly due to the narrow channel, and the measurement accuracy of the temperature cannot effectively cover it. At this time, the oil saturation obtained by the conductivity coefficient is more accurate; in the area where the oil saturation obtained by the conductivity coefficient is obviously lower, the thermal conductivity coefficient plays an auxiliary calculation role, the second weight ω3 of the conductivity coefficient can be preset to 0.5-0.7, and the weight ω4 of the thermal conductivity coefficient can be preset to 0.3-0.5. A small-size three-dimensional sand filling model is used for verification, and after several trial calculations, it is found that when ω3 and ω4 are 0.65 and 0.35 respectively, the average error value of the inversion result is the smallest, which can be used as the optimal weight value; in the area where the oil saturation measured by the conductivity coefficient is higher than the value measured by the thermal conductivity coefficient and the difference between them is more than 5%, the thick oil around the pressure-sensitive probe is replaced by the injected fluid, and the pressure fluctuation is small and cannot accurately reflect the change of the oil saturation. Therefore, the saturation corresponding to the intersection point of the curve of the conductivity coefficient-oil saturation relationship and the curve of the thermal conductivity coefficient-oil saturation relationship is the oil saturation value at each point. Figure 8 .

[0130] Finally, the mass conservation method is used to calculate the oil saturation value in each grid and compare it with the final recovery degree of the experiment. The mass produced by the oil saturation in the model can be expressed as:

[0131]

[0132] The volume of the experimental oil production recorded during the development process is 7157 mL, and the mass m oe is 6585 g. Compared with the oil production m oc (6724 g) calculated by the saturation, if the calculation mass deviation is within the allowable error range (less than 5%), the comparison result shows that the oil saturation field identified by the multi-physical field has high accuracy.

[0133] Therefore, the application adopts the above-mentioned experimental device and method for measuring heavy oil saturation based on multi-physical field coupling, a sand filling model shell made of temperature-resistant and pressure-resistant and insulating polyether ether ketone material is used to construct a comprehensive heavy oil saturation measurement experimental device containing multiple physical fields such as flow field, electric field and temperature field, which can measure the effective action distance of injected hot fluid in the thermal recovery process while accurately measuring the heavy oil saturation, and provides an efficient system method for accurately measuring the saturation of heavy oil in the indoor experiment, and guides the detection of potential tapping in the physical simulation of thermal recovery development of heavy oil reservoir.

[0134] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: the technical solutions of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. The experimental device for measuring heavy oil saturation based on multi-physics field coupling is characterized by: The device includes an oil reservoir simulation system, an oil reservoir development system and a residual oil content measurement and control system The reservoir simulation system includes a three-dimensional sand-filled model shell, the interior of the three-dimensional sand-filled model shell is filled with porous medium fillers, the interior of the three-dimensional sand-filled model shell is connected to the formation pressure system through a pipeline, and the exterior of the three-dimensional sand-filled model shell is connected to the model communication system; The oil reservoir development system includes an injection supply system, a metering and control system, and a well network system. The output end of the injection supply system is connected to the metering and control system through a pipeline, and the injection supply system is connected to the well network system through a second six-way valve. The residual oil content measurement and control system includes a pressure detection system, a conductive detection system, a thermal conductivity detection system and a multi-physical field coupling saturation measurement system.

2. The heavy oil saturation measurement experimental device based on multi-physical field coupling according to claim 1 is characterized in that: The supply system includes a double-cylinder plunger displacement pump, a liquid supply intermediate container, a displacement gas cylinder, a gas flow controller, a mixed displacement system generator and a steam generator. The output end of the double-cylinder plunger displacement pump is connected to the liquid supply intermediate container through a liquid separation three-way valve, the output end of the liquid supply intermediate container is connected to the inlet of the first six-way valve, the output end of the displacement gas cylinder is connected to the gas flow controller, the output end of the gas flow controller is connected to the other inlet of the first six-way valve, the input end of the mixed displacement system generator is connected to the outlet of the first six-way valve, the output end of the mixed displacement system generator is connected to the inlet of the second six-way valve, the output end of the steam generator is connected to the other inlet of the second six-way valve, and the other outlet of the first six-way valve is connected to the input end of the second six-way valve.

3. The heavy oil saturation measurement experimental device based on multi-physical field coupling according to claim 1 is characterized in that: The measurement and control system includes a first measuring cylinder, a first electronic balance, a second measuring cylinder and a second electronic balance. The first measuring cylinder is connected to the outlet of the second six-way valve, and a first electronic balance is provided at the lower end of the first measuring cylinder. The output end of the reservoir simulation system is connected to the second measuring cylinder through a back pressure valve, and a second electronic balance is provided at the lower end of the second measuring cylinder.

4. The heavy oil saturation measurement experimental device based on multi-physical field coupling according to claim 1 is characterized in that: The well network system includes a wellbore structure and a sand control spring structure. The wellbore structure includes a wellbore mechanism and a well position fixing mechanism. The well position fixing mechanism realizes material exchange between external fluid and the reservoir simulation system.

5. The heavy oil saturation measurement experimental device based on multi-physical field coupling according to claim 1 is characterized in that: The pressure detection system includes a pressure detection array and an electronic pressure gauge, the conductivity detection system includes a high-precision DC power supply, an electric field controller and a potential detection array, and the heat conductivity detection system includes a bottom plate heating device, a temperature detection array and a heat flux density measuring device.

6. A method for measuring heavy oil saturation based on multi-physics field coupling, wherein the heavy oil saturation measurement experimental device based on multi-physics field coupling according to claims 1-5 is applied to the measurement, characterized in that: The following steps are included S1. Build a reservoir physical model and select the appropriate sand control spring structure based on the diameter of the porous medium filling and the external fluid impact force; S2. Multi-parameter synchronous acquisition: collecting pressure conductivity, electrical conductivity, and thermal conductivity in the pressure detection system, electrical conductivity detection system, and thermal conductivity detection system respectively; S3. Multi-physics coupling is used to calculate the saturation of heavy oil. Based on the physical property changes derived from the pressure conductivity, electrical conductivity, and thermal conductivity, the identification of saturation is corrected and supplemented using the pressure conductivity, electrical conductivity, and thermal conductivity. S4. Verify the heavy oil saturation and calculate the mass deviation between the experimental oil production and the oil production calculated using the saturation. If the calculated mass deviation is within the allowable error range, it is considered that the calculated value complies with the law of conservation of mass and has a high degree of accuracy.

7. The method for measuring heavy oil saturation based on multi-physical field coupling according to claim 6, characterized in that: The spring screening expression of the sand control spring structure is: Where l0 is the pitch of the spring, d s is the spring wire diameter, θ is the angle between the main flow line direction and the spring axis, k is the radial spring constant of the spring, n is the number of coils of the spring, and D is the gravel diameter.

8. The method for measuring heavy oil saturation based on multi-physical field coupling according to claim 6, characterized in that: The pressure conduction coefficient expression is: Among them, k1 and k2 are the undetermined coefficients of pressure transmission coefficient. is the porosity of the porous medium, K is the permeability, S o is the oil saturation, c t is the comprehensive compression coefficient of the core; The conductivity coefficient expression is: Among them, k3, k4 and k5 are the unknown coefficients of the conductive properties of saturated fluid porous media related to the porous media, R w is the resistivity of formation water; The expression of thermal conductivity is: Among them, c p is the specific heat capacity, Q is the internal heat source, ρ is the density, T is the temperature, t is the time, and λ is the thermal conductivity coefficient.

9. The method for measuring heavy oil saturation based on multi-physical field coupling according to claim 6, characterized in that: The expression for calculating oil production by saturation is: Among them, ρ o is the density of crude oil, S oi is the oil saturation, V i,j,k is the apparent volume of the porous medium in the model.

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