Crude oil multi-component differential seepage measurement method and device

Abstract

The invention discloses a crude oil multi-component differential seepage measurement method and device, and the method comprises the following steps: S1, injecting to-be-measured crude oil into a solution cylinder (1), pressurizing to be higher than saturation pressure, and keeping constant pressure in the solution cylinder (1); s2, crude oil enters a rock core seepage displacement device (2) through a high-pressure-bearing pipe (3), the pressure of the right end of the rock core seepage displacement device (2) is equal to the pressure in the solution cylinder (1), the outlet pressure difference is controlled, the oil flow is controlled, and the oil phase flow is kept relatively stable; s3, recording the total flow and the flow of each component, collecting crude oil samples at the outflow port of the solution cylinder (1) and the core seepage displacement device (2) at different time, and measuring the component composition in the outflow oil phase sample; and S4, respectively calculating the seepage velocity and flow of the crude oil and each component thereof. The device and the method can be used for measuring the seepage velocity and the flow of crude oil and components thereof under a high-pressure condition, and correctly reflecting the flow rule of each component in the oil reservoir seepage process.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas development, and in particular to a method and a device for measuring multi-component differential seepage of crude oil. Background Art

[0002] In the process of studying multiphase seepage, it was found that there are problems with the current mathematical model of multiphase and multicomponent seepage: the existing component mathematical model cannot fully capture the differential characteristics of molecular flow: (1) When the injected gas has not yet broken through, the predicted production gas-oil ratio remains basically unchanged, whether it is commercial or non-commercial theoretical calculations, which deviates significantly from the actual production situation.

[0003] (2) In the production practice of oil and gas fields, significant changes in the properties of the oil phase are observed over time, such as condensate gas turning into black oil. However, the existing mathematical models cannot accurately describe the dynamic changes of the components during the flow process.

[0004] (3) When CO is injected into the oil phase for extraction under supercritical conditions, it is found that the remaining oil phase is a solid residue. However, existing numerical simulators and component mathematical models are unable to simulate this experimental result.

[0005] The above phenomenon shows that the current multiphase and multicomponent seepage measurement technology is not perfect. After research and analysis, the fundamental reason is that these multiphase and multicomponent models, when describing the seepage of multicomponents, imply that all components in each phase fluid (oil phase, gas phase, water phase) flow at the same seepage velocity, without considering that different molecules in the same phase fluid have different seepage velocities. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a method and device for measuring multi-component differential seepage of crude oil.

[0007] The present invention is implemented by adopting the following technical scheme: a method for measuring the differential seepage of multi-component crude oil, comprising the following steps: S1: Inject the crude oil to be tested into the solution cylinder and pressurize it to a pressure higher than the saturation pressure, that is: and keep the solution cylinder at a constant pressure; S2: Crude oil enters the core seepage displacement device through the high-pressure pipe. The pressure at the right end of the core seepage displacement device is equal to the pressure in the solution cylinder, that is: ; and control the outlet pressure difference , control the oil flow , keep the oil phase flow rate relatively stable; S3: Record the total flow rate and the flow rate of each component, collect crude oil samples from the outflow port of the solution cylinder and the core seepage displacement device at different times, and measure the component composition of the outflow oil phase samples; S4: Calculate the seepage velocity and flow rate of crude oil and its components respectively.

[0008] Furthermore, the calculation method of the seepage velocity of the crude oil and its components is: ; in, is the average true flow velocity; is the deviation flow rate; is the porosity; For components Content in oil phase; is the oil phase saturation; is the absolute permeability of the porous medium; is the relative permeability of the oil phase; is the viscosity of the oil phase; is the density of the oil phase; is the gravity coefficient; For any component The true flow rate is controlled by the pure viscosity factor; The components defined right The friction coefficient generated satisfies .

[0009] Furthermore, The calculation method is: ; in, For components The relative permeability factor of For components Partial viscosity in the oil phase; For components Reduced pressure component in the oil phase; is the gradient operator.

[0010] Furthermore, The calculation method is: ; in, is the pre-factor; Question: Components in the oil phase Mole fraction; Indicates the pure components of a liquid at the same temperature and pressure Viscosity value.

[0011] Furthermore, the calculation method of the flow rate of the crude oil and its components is: ; in, For components The seepage velocity; For components Content in oil phase; is the oil phase saturation; is the porosity; is the pre-factor.

[0012] A crude oil multi-component differential seepage measurement device is used for the above-mentioned crude oil multi-component differential seepage measurement method, the device comprises a solution cylinder and a core seepage displacement device, the solution cylinder is connected to the core seepage displacement device through a high-pressure pipe, and a connection port is provided on the solution cylinder for communicating with a piston; the core seepage displacement device is horizontally arranged, and a core clamping cavity is provided inside for placing a core or multi-section core sample to be measured, and a fluid inlet and a fluid outlet are also provided on the core seepage displacement device, and the seepage velocity and flow rate of the crude oil and its components in the core are measured by monitoring the crude oil inflow and outflow data.

[0013] Furthermore, the piston is coaxially arranged with the solution cylinder and slidingly cooperates with the cylinder body of the solution cylinder through a high temperature resistant seal. A solid push rod is arranged on the upper part of the piston, and the solid push rod is connected to the constant pressure pump.

[0014] Furthermore, a first sampling port or a discharge port is provided at the lower portion of the solution cylinder so as to sample or discharge the fluid at different stages; an outlet is also provided at the lower portion of the solution cylinder, and the outlet is connected to the fluid inlet of the core seepage displacement device through a high-pressure pipe.

[0015] Furthermore, a first pressure gauge is provided at the fluid inlet of the core seepage displacement device, and a second pressure gauge and a flow meter are provided at the fluid outlet of the core seepage displacement device.

[0016] The beneficial effects of the present invention are: The present invention can correctly reflect the flow law of components in the oil reservoir seepage process; can correctly reflect the change of gas-oil ratio of oil wells; can correctly reflect the change law of oil reservoir components over time, the change law of oil phase physical properties, and the emergence of modified oil reservoirs, such as the change from volatile oil to black oil.

[0017] The present invention considers the effective period difference of component seepage, so as to correctly sample and correctly reflect the component composition of the reservoir. Especially for the reservoir developed over a long distance and for a long time with a large flow rate, considering the differential seepage of components has important engineering practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 It is a flow chart of the present invention; In the figure, 1-solution cylinder, 2-core seepage displacement device, 3-high pressure pipe, 4-piston, 5-first sampling port, 6-fluid outlet, 7-first pressure gauge, 8-second pressure gauge, 9-flow meter. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0022] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0023] See also Figure 1 The invention discloses a crude oil multi-component differential seepage measuring device, comprising a solution cylinder 1 and a core seepage displacement device 2. The solution cylinder 1 is connected to the core seepage displacement device 2 through a high-pressure pipe 3. A connection port is provided on the solution cylinder 1 for communicating with a piston 4. The core seepage displacement device 2 is horizontally arranged, and a core clamping cavity is provided inside for placing a core or a multi-section core sample to be measured. A fluid inlet and a fluid outlet 6 are also provided on the core seepage displacement device 2. The seepage velocity and flow rate of the crude oil and its components in the core are measured by monitoring the crude oil inflow and outflow data.

[0024] In this embodiment, the solution cylinder 1 is a high-pressure container that can hold crude oil. The cylinder body is made of alloy steel or other pressure-resistant materials, and a connection port is provided on the top or side wall of the cylinder body of the solution cylinder 1 for communicating with the piston 4. A first sampling port 5 or a discharge port may be provided at the bottom or side of the cylinder body to sample or discharge the fluid at different stages. During the experimental operation, a constant pressure higher than the saturation pressure of the crude oil is maintained in the solution cylinder 1 to prevent gas escape or phase change.

[0025] In this embodiment, the piston 4 is coaxially arranged with the solution cylinder 1, and slidingly cooperates with the cylinder body through a high-pressure resistant seal (such as an O-ring or a metal seal). In addition, a solid push rod is provided on the upper part of the piston 4, and the solid push rod is connected to a constant pressure pump (not shown in the figure). The force applied by the push rod is adjusted by the constant pressure pump to achieve constant control of the pressure in the solution cylinder 1.

[0026] In this embodiment, the core seepage displacement device 2 is horizontally arranged, and a core clamping cavity is provided inside for placing the core to be tested or multiple core samples. The shell material of the core seepage displacement device 2 also needs to have the characteristics of high temperature and high pressure resistance; a fluid inlet and a fluid outlet 6 are provided at both ends, wherein the inlet is connected to the solution cylinder 1 through a high-pressure pipe 3, and the high-pressure pipe 3 is usually a pressure-resistant metal pipe, which can safely transport crude oil under high pressure conditions; the outlet end can be connected to a detection or collection unit, and under high pressure drive, crude oil flows from the solution cylinder 1 into the core seepage displacement device 2, flows through the core pores and then flows out, and the seepage velocity and flow rate of the crude oil and its components in the core are measured by a crude oil component composition detection instrument, and the crude oil component composition detection instrument can adopt existing instruments, such as: liquid chromatography (LC) and gel permeation chromatography (GPC), mass spectrometry (MS) technology: GC-MS, LC-MS, high resolution mass spectrometry (HRMS), FT-ICR MS.

[0027] The crude oil multi-component differential seepage measurement device can be used to measure the seepage velocity, flow rate and relative deviation of crude oil and its components under high pressure conditions, and calculate the drag coefficient matrix.

[0028] See also Figure 2 The method for measuring the differential seepage of crude oil multi-components comprises the following steps: S1: Inject the crude oil to be tested into the solution cylinder and pressurize it to a pressure higher than the saturation pressure, that is: and keep the solution cylinder at a constant pressure; S2: Crude oil enters the core seepage displacement device through the high-pressure pipe. The pressure at the right end of the core seepage displacement device is equal to the pressure in the solution cylinder, that is: ; and control the outlet pressure difference , control the oil flow , keep the oil phase flow rate relatively stable; S3: Record the total flow rate and the flow rate of each component, collect crude oil samples from the outflow port of the solution cylinder and the core seepage displacement device at different times, and measure the component composition of the outflow oil phase samples; S4: Calculate the seepage velocity and flow rate of crude oil and its components respectively.

[0029] Specifically, the present invention is to convert any component in the oil The real flow rate is decomposed into the average real flow rate of all molecules ( ) and deviation flow rate ( ); The existing oil phase seepage formula is used. Indicates other group pairs The collision and friction effect is described as the difference in component flow rates and the friction coefficient ( ), compared with the traditional model, the differential seepage characteristics of multiple components in the oil phase are considered: ; (1) Where: —porosity, dimensionless; —Components The content in the oil phase (can be mole fraction or mass fraction, etc.), dimensionless; —Oil phase saturation, dimensionless; —absolute permeability of porous media, Darcy; —Oil phase relative permeability; —Oil phase viscosity, mPa.s; —Oil phase density, Kg / m 3 , —Gravity coefficient, 9.8N / Kg; —Any component The actual flow rate controlled by the pure viscosity factor, m / s; — is the component we defined right The resulting friction coefficient is dimensionless and satisfies .

[0030] Among them, any component The flow rate under the pure viscosity factor control ( ) is calculated as: ; (2) This formula has a form similar to Darcy's formula, but with the addition of (Component of the partial viscosity), (relative permeability factor); where, —Components The relative permeability factor is dimensionless and is related to the volume proportion of each component. For multi-component mixed liquids with weak molecular interactions (such as hydrocarbons), the value can be , here is the system calibration constant; —Components Partial Molar Viscosity in the oil phase, unit , note that it is different from the pure component The viscosity of the liquid ( ) are different; —Indicates the component Reduced pressure component in the oil phase.

[0031] Furthermore, the present invention also proposes a method for calculating the "partial viscosity" (Partial Molar Viscosity) according to the log-linear mixing rule of multi-component viscosity, as shown in the formula GOTOBUTTON ZEqnNum463881 \*MERGEFORMAT REF ZEqnNum463881 \* Charformat \! \* MERGEFORMAT (3). Compared with the commonly used method of taking the viscosity of the pure component as the value of the "partial viscosity", The new method takes into account the composition The influence of the molecular distribution in space. Compared with the traditional "partial viscosity" obtained by "viscosity contribution", The existing physical dimensions are different from the physical dimensions of the actual "viscosity". The results calculated by the new method maintain the consistency of the physical dimensions and reflect the influence of the components themselves due to their more dispersed spatial distribution: ; (3) Where: — represents the Eyring molecular viscosity-activation free energy formula [ 】The pre-factor in the liquid formula composed of , the unit is mPa.s. Indicates the pure components of a liquid at the same temperature and pressure Viscosity value. Indicates the components in the oil phase In addition, considering that the measurement of A value is rarely carried out, the present invention also provides an approximate calculation formula method: ; (4) Further considering the differences in the A values ​​of each component, a calculation method is also proposed: ; (5) Indicates all components The average of the values.

[0032] The crude oil multi-component differential seepage measurement device can be used to measure the seepage velocity of crude oil and its components under high pressure conditions. 】,flow【 】 and its relative deviation【 】, calculate the drag coefficient matrix .

[0033] Among them, the measurement method for measuring the flow velocity of each component in crude oil includes: Inject the crude oil to be tested into the solution cylinder 1 and pressurize it to a pressure higher than the saturation pressure. Adjust the constant pressure pump to stabilize the piston 4 to maintain a constant pressure in the cylinder. ; Crude oil enters the core seepage displacement device 2 through the high-pressure pipeline 3. The pressure at the right end of the displacement device , control outlet pressure difference , control the oil flow , keep the oil phase flow rate relatively stable; The total flow rate and the flow rate of each component are recorded by flow meter or other measuring means. At the same time, crude oil samples are collected from the outflow port of the solution cylinder and the core displacement device at different times, and the component composition of the outflowing oil phase samples is measured; for each group of crude oil samples, the components of the solution cylinder and the outflowing liquid need to be measured 3-4 times, and the measurement is 3-4 times. When the volume ratio of the remaining oil body in the solution cylinder to the crude oil is 100%, 70%, 40%, and 10%, samples are taken at the solution cylinder and the core displacement outlet at the same time, and each component is measured; The corresponding seepage velocity under the condition ; As shown in Table 1: Table 1. Component differential seepage experimental measurement data .

[0035] Drag coefficient of each component in the oil phase The measurement and calculation of the matrix is ​​based on the content and velocity measurement of crude oil components in formula (1). Substituting formula (2) into formula (1), we can get: ; (6) There are n equations expressed by formula (6), but the drag coefficient to be determined is The unknown elements in the matrix are So the number of equations needs to be supplemented. The proposed solution is to expand the test sample from 1 to M, thus obtaining equation. M needs to satisfy (here represents the CEILING rounding function), and write the M test results into Table 2.

[0036] Table 2. Data table of experimental measurements of different samples .

[0038] So we get: ; (7) In the formula, , , ; (8) Solving equation (7) equations, thus obtaining , then according to Get the drag coefficient.

[0039] The present invention is further described below by an example Since it may be difficult to accurately query the viscosity and density data of n-hexane-n-octane mixtures with different mixing ratios and temperatures under a specific pressure (10MPa), the following approximate data will be provided as a reference, see Table 3, and the analysis of trends and laws will be focused on in order to understand the principle of differential seepage: Approximate physical property data (assuming that the pressure has a small effect, use data close to atmospheric pressure as a reference trend).

[0040] Table 3 n-Hexane-n-Octane parameters .

[0042] Permeability ( ): 0.3× (Darcy units converted to SI units); Porosity ( ): 0.15 (dimensionless); core length ( ):1 ; Core cross-sectional area ( ): ; Pressure difference: . The formula for Darcy's law is: ; in: is the Darcy speed ( ); is the permeability ( ); is the fluid viscosity ( ); is the pressure difference ( ); is the seepage path length ( ). The volume flow rate Q can be obtained by multiplying the Darcy velocity by the cross-sectional area: Mixture (50% n-octane): Viscosity .

[0043] Darcy speed: ; True seepage velocity: ; Volume flow ; The "partial viscosities" of n-hexane and n-octane are: ; ; Substitution The calculation formula (6) is: .

[0044] The deviation flow rate of n-hexane is obtained as: ; Flow rate of n-hexane component: ; Flow rate of n-octane component: .

[0045] It should be noted that the terms "connection" and "setting" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "connection" and "setting" may explicitly or implicitly include one or more of the features. Moreover, the terms "connection", "setting" and the like are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. And for the aforementioned embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited to the described order of actions, because according to the present application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification belong to preferred embodiments, and the actions involved are not necessarily required by the present application.

[0046] For the aforementioned embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily required by the present application.

[0047] The above embodiments describe the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the changes and modifications made by those skilled in the art shall be within the scope of protection of the appended claims of the present invention without departing from the spirit and scope of the present invention.

Claims

1. A method for measuring the differential seepage of crude oil with multiple components, characterized in that: The steps include: S1: Inject the crude oil to be tested into the solution cylinder (1) and pressurize it to a pressure higher than the saturation pressure, that is: and maintaining a constant pressure in the solution cylinder (1); S2: Crude oil enters the core seepage displacement device (2) through the high-pressure pipe (3). The pressure at the right end of the core seepage displacement device (2) is equal to the pressure in the solution cylinder (1), that is: ; and control the outlet pressure difference , control the oil flow , keep the oil phase flow relatively stable; S3: Record the total flow rate and the flow rate of each component, collect crude oil samples from the outflow port of the solution cylinder (1) and the core seepage displacement device (2) at different times, and measure the component composition of the outflowing oil phase sample; S4: Calculate the seepage velocity and flow rate of crude oil and its components respectively.

2. The method for measuring the differential seepage of crude oil multi-components according to claim 1, characterized in that: The calculation method of the seepage velocity of the crude oil and its components is: ； in, is the average true flow velocity; is the deviation flow rate; is the porosity; For components Content in oil phase; is the oil phase saturation; is the absolute permeability of the porous medium; is the relative permeability of the oil phase; is the viscosity of the oil phase; is the density of the oil phase; is the gravity coefficient; For any component The true flow rate is controlled by the pure viscosity factor; The components defined right The friction coefficient generated satisfies .

3. The method for measuring the multi-component differential seepage of crude oil according to claim 2, characterized in that: The calculation method is: ； in, For components The relative permeability factor of For components Partial viscosity in the oil phase; For components Reduced pressure component in the oil phase; is the gradient operator.

4. The method for measuring the differential seepage of crude oil multi-components according to claim 3, characterized in that: The calculation method is: ； in, is the pre-factor; Question: Components in the oil phase Mole fraction; Indicates the pure components of a liquid at the same temperature and pressure Viscosity value.

5. The method for measuring the differential seepage of crude oil multi-components according to claim 1, characterized in that: The calculation method of the flow rate of the crude oil and its components is: ； in, For components The seepage velocity; For components Content in oil phase; is the oil phase saturation; is the porosity; is the pre-factor.

6. A crude oil multi-component differential seepage measurement device, used to implement the crude oil multi-component differential seepage measurement method according to any one of claims 1 to 5, characterized in that: The device comprises a solution cylinder (1) and a core seepage displacement device (2); the solution cylinder (1) is connected to the core seepage displacement device (2) via a high-pressure pipe (3); a connection port is provided on the solution cylinder (1) for communicating with a piston (4); the core seepage displacement device (2) is arranged horizontally, and a core clamping cavity is provided inside for placing a core or a multi-section core sample to be tested; a fluid inlet and a fluid outlet (6) are also provided on the core seepage displacement device (2); and the seepage velocity and flow rate of crude oil and its components in the core are measured by monitoring crude oil inflow and outflow data.

7. The crude oil multi-component differential seepage measurement device according to claim 6, characterized in that: The piston (4) is coaxially arranged with the solution cylinder (1) and is slidably matched with the cylinder body of the solution cylinder (1) via a high-temperature resistant seal. A solid push rod is provided on the upper part of the piston (4), and the solid push rod is connected to a constant pressure pump.

8. The crude oil multi-component differential seepage measurement device according to claim 6, characterized in that: The lower part of the solution cylinder (1) is provided with a first sampling port (5) or a discharge port so as to sample or discharge the fluid at different stages; the lower part of the solution cylinder (1) is also provided with an outlet, which is connected to the fluid inlet of the core seepage displacement device (2) through a high-pressure pipe (3).

9. The crude oil multi-component differential seepage measurement device according to claim 6, characterized in that: A first pressure gauge (7) is provided at the fluid inlet of the core seepage displacement device (2), and a second pressure gauge (8) and a flow meter (9) are provided at the fluid outlet of the core seepage displacement device (2).

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