Device and method for evaluating oil saturation of rock based on step-by-step centrifugal volumetric method

Abstract

The invention relates to a device and method for evaluating the oil saturation of rock based on a step-by-step centrifugal volumetric method, and the device comprises a centrifugal unit which comprises a rotating support and a centrifugal tray sleeving the rotating support; the measuring unit comprises a plurality of closed detachable centrifugal tubes, the plurality of centrifugal tubes are uniformly arranged in the circumferential direction of the centrifugal tray, a pressurizing chamber, a sample chamber and a collecting chamber are sequentially arranged in each centrifugal tube from top to bottom, and the pressurizing chamber and the sample chamber are separated through a sealing partition plate and are controlled to be opened and closed through a valve; and the sample chamber and the collection chamber are separated by a filter screen. Compared with an organic solvent, the supercritical CO2 adopted by the method has obvious advantages in the quantification of the crude oil of the source rock. The oil content measuring agent has both gas diffusivity and liquid solubility, is small in molecular size, can penetrate through tiny pores of source rocks, is higher in dissolving capacity for heavy components in crude oil, and can fully extract the crude oil in various pores and reduce residues, so that the oil content of the rocks is more accurately quantified.

Description

TECHNICAL FIELD

[0001] The application relates to a device and method for evaluating oil saturation of rock based on a step-by-step centrifugal volume method, and belongs to the technical field of oil and gas field exploration. BACKGROUND

[0002] Conventional oil saturation evaluation methods mainly include core analysis, logging analysis and laboratory phase permeability method. The core analysis obtains core samples, separates oil and water by distillation and extraction, and calculates oil saturation combined with porosity, but the method is prone to data distortion due to fluid loss during core taking and transportation, and cannot reflect the state under the original formation condition. The logging analysis indirectly calculates by using resistivity, acoustic wave and other logging curves, is greatly affected by formation heterogeneity and logging instrument precision, and has a wide error range. The phase permeability method deduces oil saturation by measuring oil-water relative permeability curves, but has many assumptions (such as uniform fluid distribution), which deviates from the complex pore structure of the actual rock sample. SUMMARY

[0003] In view of the above technical problems, the application provides a device and method for evaluating oil saturation of rock based on a step-by-step centrifugal volume method. The method can effectively overcome the following defects by using high-speed centrifugal volume method: on the one hand, the total pore volume is accurately measured by combining multi-stage centrifugal force with CO2 adsorption and DFT model, full-scale pores from micro-pores to macro-pores are covered, and the one-sidedness of the conventional method for estimating pore volume is avoided; on the other hand, oil and water in the rock sample are directly separated by using centrifugal force and the volume is measured, without relying on indirect deduction or assumption, and the error is reduced. At the same time, the heating jacket simulates the formation temperature, and the high-pressure environment maintains the original state of the fluid, so that the calculation of oil saturation is closer to the real formation condition.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical scheme: A device for evaluating oil saturation of rock based on a step-by-step centrifugal volume method, comprising: A centrifugal unit, comprising a rotating support and a centrifugal tray sleeved on the rotating support; A measuring unit, comprising a plurality of closed and detachable centrifugal tubes, the centrifugal tubes are uniformly arranged along the circumferential direction of the centrifugal tray, the centrifugal tubes are sequentially provided with a pressurizing chamber, a sample chamber and a collection chamber from top to bottom, the pressurizing chamber and the sample chamber are separated by a sealing partition plate and are controlled to open and close by a valve, and the sample chamber and the collection chamber are separated by a filter screen.

[0005] Preferably, the upper end of the centrifugal tube is provided with a gas injection port, and / or; The collection chamber is provided with a valve two.

[0006] The device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method, preferably, the booster chamber is provided with a pressure gauge one.

[0007] The device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method, preferably, the sample chamber is provided with a pressure gauge two.

[0008] The device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method, preferably, the outside of the centrifugal tube is sleeved with a heating jacket.

[0009] The second aspect of the present application provides a method for operating a device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method, comprising the following steps: During measurement, the sample is first added to the sample chamber, the booster chamber is filled with boosted CO2 through the gas injection port, the reading P0 of the pressure gauge one is recorded, the centrifugal tray is started to reach the specified speed after the gas injection port is closed, the valve one is opened, the pressure gauge one and the pressure gauge two have the same reading P1 when the valve one is closed, a period of time is allowed to elapse, the reading of the pressure gauge two slowly decreases from P1 to P1', and the reading remains unchanged for a certain period of time, then the relative pressure P1' / P1 is recorded, and the CO2 adsorption amount V1 entering the sample is calculated through the gas state equation; The centrifugal speed is increased step by step, CO2 is filled to reach the centrifugal force corresponding to the speed, and the relative pressure P n ' / P n and the CO2 adsorption amount V n are obtained by repeating the measurement, the total pore volume v 孔 of the sample is obtained by using a DFT model, the valve two is opened to obtain the oil volume v 油 and the water volume v 水 , and the oil saturation S 油 and the water saturation S 水 of the sample are calculated.

[0010] The method for operating the device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method, preferably, The calculation formula of the CO2 adsorption amount V1 is as follows: V1=P1V0 / P1' In the formula, V0 is the volume of the sample chamber.

[0011] The method for operating the device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method, preferably, the calculation formula of the oil saturation S 油 of the sample is as follows: S 油 =v 油 / v 孔 .

[0012] The operation method of the device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method, preferably, the water saturation S of the sample 水 The calculation formula is as follows: S 水 =v 水 / v 孔 .

[0013] The present application has the following advantages due to the above technical scheme: 1、The method of the present application has obvious advantages in source rock oil quantification compared with organic solvents. It has gas diffusion and liquid solubility, small molecular size, can penetrate the small pores of source rock, and has stronger solubility for heavy components in crude oil, can fully extract crude oil in various pores, reduce residue, and thus more accurately quantify the oil content of source rock.

[0014] 2、The centrifugal method has simpler requirements for sample specifications and pretreatment, without the need for complex processing, and the rock sample can be directly loaded into the sample chamber. The weight method needs to grind the rock sample into powder, which is easy to cause oil evaporation or loss during the grinding process, affecting the accuracy of quantification. The centrifugal method relies on the synergistic effect of centrifugal force and CO2 to maximize the preservation of the original state of the crude oil and reduce the error in the pretreatment link.

[0015] 3、The present application avoids the limitations of traditional centrifugal methods: conventional centrifugal technology is mostly operated by single centrifugal force when measuring oil saturation, which can only separate free fluid and is difficult to access capillary bound fluid and clay bound fluid, resulting in the omission of key parts in oil saturation calculation. The multi-speed centrifuge of the present application can simulate different formation stress environments, fully displace various fluids, accurately reveal the true oil state of the rock sample, and solve the problem of one-sidedness in conventional centrifugal method measurement. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method provided by the present application is shown in the internal schematic diagram; Figure 2 The device operation flowchart provided by the present application is shown in the internal schematic diagram; The reference signs in the drawings are as follows: 1- pressure gauge one; 2- centrifugal tube; 3- pressure gauge two; 4- filter screen; 5- collection chamber; 6- gas injection port; 7- centrifugal tray; 8- valve one; 9- heating jacket; 10- sample chamber; 11- valve two; 12- pressure boosting chamber. DETAILED DESCRIPTION

[0017] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application are clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0018] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the common meaning understood by those skilled in the art to which the present application pertains. The terms "first", "second", "third", "fourth" and similar words used in the present application do not indicate any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar words mean that the components or objects before the words cover the components or objects listed after the words and their equivalents, but do not exclude other components or objects. The terms "connect" or "connected" and similar words are not limited to physical or mechanical connection, but can include electrical connection, whether direct or indirect.

[0019] In order to facilitate the description, spatial relative terms can be used in the description to describe the relationship of one element or feature to another element or feature as shown in the drawings, such as "inner", "outer", "inside", "outside", "below", "above", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the drawings.

[0020] The conventional oil saturation evaluation methods mainly include core analysis method, logging analysis method and laboratory phase permeability method, etc. The core analysis method obtains core samples, separates oil and water by distillation method, extraction method, etc., and calculates oil saturation combined with porosity, but this method is easy to cause data distortion due to fluid loss in the core taking and transporting process, and cannot reflect the state under the original formation condition. The logging analysis method indirectly calculates by using resistivity, acoustic wave and other logging curves, which is greatly affected by formation heterogeneity and logging instrument precision, and has a wide error range. The phase permeability method deduces oil saturation by determining oil-water relative permeability curve, but its assumption conditions are more (such as uniform fluid distribution), which deviates from the complex pore structure of actual rock sample.

[0021] Based on the above technical problems, the application provides a device and method for evaluating oil saturation of rock based on a step-by-step centrifugal volume method, which is a brand-new quantitative measurement method, and combines step-by-step centrifugal-CO2 adsorption pore measurement with centrifugal separation-liquid collection crude oil measurement to directly calculate oil saturation through "crude oil volume / total pore volume", thereby omitting intermediate links of a traditional weight method and reducing errors.

[0022] As shown in Figure 1 、 2 The device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method comprises the following components. A centrifugal unit, which comprises a rotating support and a centrifugal tray 7 sleeved on the rotating support; A measurement unit, which comprises a plurality of closed and detachable centrifugal tubes 2, the centrifugal tubes 2 are uniformly arranged along a circumferential direction of the centrifugal tray 7, and the centrifugal tube 2 is sequentially provided with a pressurizing chamber 12, a sample chamber 10 and a collection chamber 5 from top to bottom, the pressurizing chamber 12 and the sample chamber 10 are separated by a sealing partition plate and are opened and closed through a valve, and the sample chamber 10 and the collection chamber 5 are separated by a filter screen 4.

[0023] Further, the centrifugal tube 2 is provided with a gas injection port 6 at an upper end, and the collection chamber 5 is provided with a valve two 11.

[0024] Further, the pressurizing chamber 12 is provided with a pressure gauge one 1, and the sample chamber 10 is provided with a pressure gauge two 3.

[0025] Further, the centrifugal tube 2 is externally sleeved with a heating jacket 9.

[0026] The second aspect of the application provides an operating method of the device for evaluating oil saturation of rock based on the step-by-step centrifugal volume method, which comprises the following steps. First, the rock sample is dried and loaded into the sample chamber 10, the sample is ensured to be uniformly filled, the valve one 8 between the sample chamber 10 and the collection chamber 5 is closed, and the sealing property of each component is checked. The temperature of the heating jacket 9 is set to 50 DEG C, and the measurement is started after the temperature is stabilized. In the initial state, the pressurizing chamber 12 and the sample chamber 10 are in a closed state, and the collection chamber 5 is empty. The rotating speed of the centrifugal tray 7 is set to v1, corresponding to a centrifugal force P1, CO2 is injected into the pressurizing chamber 12 through the gas injection port 6, the reading P0 of the pressure gauge one 1 is recorded, the centrifugal tray 7 is started to reach the specified rotating speed v1 after the gas injection port 6 is closed, the adjusting valve one 8 is opened, CO2 enters the sample chamber 10 from the pressurizing chamber 12, the readings of the pressure gauge one 1 and the pressure gauge two 3 are the same, which is P1, the adjusting valve one 8 is closed, and the initial pressure of the sample chamber 10 is ensured to be P1.

[0027] After standing for a period of time, when the reading of the pressure gauge 3 slowly decreases to P1' and remains unchanged for 30 minutes, record the P1' at this time, calculate the relative pressure P1' / P1 and the CO2 adsorption amount V1=P1V0 / P1'.

[0028] According to the above steps, the rotating speed is increased to v2, v3,..., vn in turn. n Corresponding to the centrifugal force P2, P3,..., Pn. n The relative pressure P1' / P2, P2' / P3,..., Pn-1' / Pn and the adsorption amount V2, V3,..., Vn (n=1, 2, 3,..., n) are obtained respectively. n n The relative pressure P1' / P2, P2' / P3,..., Pn-1' / Pn and the adsorption amount V2, V3,..., Vn (n=1, 2, 3,..., n) are obtained respectively. n

[0029] The relative pressure P1' / P2, P2' / P3,..., Pn-1' / Pn and the adsorption amount V2, V3,..., Vn (n=1, 2, 3,..., n) are obtained respectively. n n n The relative pressure P1' / P2, P2' / P3,..., Pn-1' / Pn and the adsorption amount V2, V3,..., Vn (n=1, 2, 3,..., n) are obtained respectively. 孔

[0030] After the measurement is completed, the valve between the sample chamber 10 and the collection chamber 5 is opened, and the liquid stored in the collection chamber 5 after being filtered by the filter screen 4 is the oil and water centrifuged from the sample, and the oil volume vO and the water volume vH are read by the volume metering device. The oil saturation S0 of the sample is calculated as vO / vT, and the water saturation SH is calculated as vH / vT. 油 水 油 油 孔 水 水 孔

[0031] The device and method of the present application can solve the following problems of the prior art: 1. The oil and gas loss problem caused by sample pretreatment is solved. The existing dry distillation method and evaporation fractionation method require sample crushing treatment, which is easy to cause oil and gas volatilization or residue during the process, directly leading to distortion of the oil saturation measurement. The present application does not need to strictly limit the sample size (no need for crushing and grinding), the rock sample can be directly loaded into the sample chamber, the original state of the oil and gas is maximally preserved, and the oil and gas loss in the pretreatment link is avoided.

[0032] 2. The quantitative deviation caused by medium selection is overcome. The traditional method uses organic solvent as the extraction medium, which has two defects: the organic solvent easily pollutes the sample, affecting the subsequent analysis; the molecular size is relatively large, the penetration of the rock sample is insufficient, the crude oil is difficult to fully extract, and the quantitative result is low. The present application uses CO2 as the medium, which has strong penetration and high solubility, and no residual pollution, solving the inherent defects of organic solvent.

[0033] ​​​​​​​​​​​​​3、Eliminate the cumulative error of intermediate links. The gravimetric method needs to indirectly obtain the crude oil volume through multiple steps such as "sample weighing-extraction after weighing-difference calculation", and each step may introduce errors (such as weighing accuracy, incomplete extraction, etc.), leading to result deviation. The present application directly collects liquid and measures volume by centrifugal separation, and directly calculates pore volume by CO2 adsorption method, omitting weighing and other intermediate links, greatly reducing transmission error and improving measurement accuracy.

[0034] The method of the present application is a new quantitative measurement method, which combines step-by-step centrifugation-CO2 adsorption pore measurement with centrifugal separation-liquid collection crude oil volume measurement, directly calculates oil saturation through "crude oil volume / total pore volume", omits intermediate links compared with traditional gravimetric method, and reduces errors. Avoid the problems of pretreatment loss, weighing error (need a large amount of sample to reduce error) in conventional methods, and realize high-precision evaluation of the whole process.

[0035] The present application utilizes the characteristics of CO2 that it has both penetrating and dissolving properties, its molecular size is small, it can penetrate into the small pores of the rock sample, and it has strong solubility for crude oil (especially heavy components), compared with organic solvents, it can more fully extract the crude oil in the pores, reduce residue, and improve the accuracy of oil content measurement.

[0036] The multi-speed centrifugal device of the present application works together with pressure, generates step-by-step centrifugal force through not less than 10 incremental speeds, matches the corresponding pressure of CO2 injection, establishes multiple sets of relative pressure (P n ’ / P n ) and adsorption amount (V n ) data, and accurately inverts the total pore volume through the DFT model. The pressure chamber and sample chamber in the measurement unit have the same volume, and the pressure balance is monitored through the pressure sensor, ensuring the accuracy of the initial pressure of CO2 under each centrifugal force, providing a reliable benchmark for CO2 adsorption calculation.

[0037] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A device for evaluating the oil saturation of rocks based on the stepwise centrifugal volumetric method, characterized in that, include: Centrifuge unit, the centrifuge unit includes a rotating support and a centrifuge tray (7) sleeved on the rotating support. The measuring unit includes several closed and detachable centrifuge tubes (2). The centrifuge tubes (2) are evenly arranged along the circumference of the centrifuge tray (7). The centrifuge tubes (2) are arranged from top to bottom as a pressurization chamber (12), a sample chamber (10) and a collection chamber (5). The pressurization chamber (12) and the sample chamber (10) are separated by a sealing partition and are controlled to open and close by a valve. The sample chamber (10) and the collection chamber (5) are separated by a filter screen (4).

2. The apparatus for evaluating rock oil saturation based on the stepwise centrifugal volumetric method according to claim 1, characterized in that, The centrifuge tube (2) is provided with an air injection port (6) at its upper end, and / or; The collection chamber (5) is equipped with valve two (11).

3. The apparatus for evaluating rock oil saturation based on the stepwise centrifugal volumetric method according to claim 2, characterized in that, The pressurization chamber (12) is equipped with a pressure gauge (1).

4. The apparatus for evaluating rock oil saturation based on the stepwise centrifugal volumetric method according to claim 3, characterized in that, The sample chamber (10) is equipped with a pressure gauge 2 (3).

5. The apparatus for evaluating rock oil saturation based on the stepwise centrifugal volumetric method according to claim 4, characterized in that, The centrifuge tube (2) is fitted with a heating sleeve (9).

6. The operating method of the apparatus for evaluating rock oil saturation based on the stepwise centrifugal volumetric method according to claim 4 or 5, characterized in that, Includes the following steps: During measurement, the sample is first added to the sample chamber (10), and pressurized CO2 is injected into the pressurization chamber (12) through the gas injection port (6). The reading P0 of the pressure gauge (1) is recorded. After the gas injection port (6) is closed, the centrifuge tray (7) is started to reach the specified speed. Valve (8) is opened. When the readings of the pressure gauge (1) and the pressure gauge (3) are the same (P1), the valve (8) is closed. After standing for a period of time, the reading of the pressure gauge (3) slowly decreases from P1 to P1' and remains unchanged for a certain period of time. The relative pressure P1' / P1 is recorded, and the amount of CO2 adsorbed into the sample V1 is calculated by the gas state equation. By gradually increasing the centrifugal speed and charging CO2 to achieve the corresponding centrifugal force, at least 10 sets of relative pressure P were obtained through repeated measurements. n ' / P n With CO2 adsorption capacity V n The total pore volume v of the sample was obtained using a DFT model. 孔 Open valve two (11) to obtain oil volume v 油 and the volume of water v 水 The oil saturation S of the sample was calculated. 油 and water saturation S 水 .

7. The operating method of the apparatus for evaluating rock oil saturation based on the stepwise centrifugal volumetric method according to claim 6, characterized in that, The formula for calculating the CO2 adsorption capacity V1 is as follows: V1=P1V0 / P1' In the formula, V0 is the volume of the sample chamber.

8. The operating method of the apparatus for evaluating rock oil saturation based on the stepwise centrifugal volumetric method according to claim 7, characterized in that, Oil saturation S of the sample 油 The calculation formula is as follows: S 油 =v 油 / v 孔 。 9. The operating method of the apparatus for evaluating rock oil saturation based on the stepwise centrifugal volumetric method according to claim 8, characterized in that, Water saturation S of the sample 水 The calculation formula is as follows: S 水 =v 水 / v 孔 。

Images