A method and device for evaluating the throughput test of an imbibition agent

Abstract

The present invention discloses an imbibition agent huff-and-puff experimental device and an evaluation method thereof, wherein the device comprises a thermostatic box, wherein a core holder and an imbibition agent piston container are arranged in the thermostatic box; the core holder can accommodate a plurality of core samples placed in sequence; the two ports of the core holder are respectively connected to the imbibition agent piston container; the imbibition agent piston container is connected to an ISCO displacement pump arranged outside the thermostatic box; the core holder is connected to an annular pressure monitoring pump arranged outside the thermostatic box. The present invention can truly simulate the process of injecting imbibition agent huff-and-puff of an oil well under reservoir conditions, and study and evaluate the spontaneous imbibition and oil production phenomenon of imbibition agent during the huff-and-puff process, providing a theoretical indoor theoretical basis for field application.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production and relates to an imbibition agent throughput test evaluation method and device. Background Art

[0002] In the process of developing complex small fault block reservoirs, oil wells in remote blocks have been mined for a long time, and there are no corresponding water injection wells to supplement the formation energy, resulting in a gradual decline in liquid volume and production. In view of this situation, the use of chemical huff and puff of oil wells can effectively supplement the formation energy, and achieve the dual effects of expanding the sweep and efficient oil washing, so as to achieve the purpose of improving oil and gas recovery. During the huff and puff process, the permeation effect of the capillary force of the oil layer is applied to allow the imbibition agent to enter the micropores along the wall of the seepage channel, so that the crude oil in the pores is displaced. This oil recovery technology is called imbibition oil recovery, which mainly relies on capillary force to achieve "liquid suction and oil discharge". There are two main types of commonly used imbibition agents: conventional aqueous solution imbibition agents and surfactant solution imbibition agents.

[0003] In his paper "Research on Reservoir Pore Structure and Seepage Characteristics of Xing 76 Area" (Northeast Petroleum University, 2018), Sun Shoumeng used the weighing method to determine the recovery rate of imbibition water flooding, used nuclear magnetic resonance technology to study the degree of imbibition recovery during oil displacement, and used the degree of imbibition recovery to evaluate the imbibition effect. The weighing method uses the difference in oil and water density to calculate the recovery degree, which has a large error; the recovery degree is affected by factors such as the mobility and emulsification carrying capacity of the imbibition agent, and does not represent its true imbibition capacity.

[0004] CN201920109002.2 discloses a visualized pressure core imbibition experimental device based on nuclear magnetic resonance, which uses a nuclear magnetic resonance instrument and a data acquisition platform to test the nuclear magnetic resonance T2 spectrum of the core water injection and huff-and-puff process, obtain the microscopic oil-water distribution state of the core, and then obtain the microscopic imbibition law of the core during different water injection and huff-and-puff processes. The device allows the imbibition agent to directly contact the oil sand or oil-bearing core in a continuous phase at the injection end, and cannot accurately simulate the imbibition phenomenon in the reservoir.

[0005] CN202011229052.8 discloses a shale dynamic imbibition device and a method for determining the dynamic imbibition impact results. The method uses a weighing method to monitor the experimental samples. By controlling the dynamic experimental conditions, the influence of different influencing factors on the shale imbibition recovery degree can be quantitatively evaluated. In the device and method, the imbibition agent is directly contacted with the oil-bearing core in a continuous phase at the injection end, which cannot accurately simulate the imbibition phenomenon in the reservoir; the weighing method is used to calculate the recovery degree, and the error is large; the recovery degree is affected by factors such as the fluidity and emulsification carrying capacity of the imbibition agent, and does not represent its true imbibition capacity.

[0006] CN202022121805.5 discloses an imbibition oil displacement effect evaluation device, which can simulate the process of fracturing fluid entering rock under temperature and pressure conditions close to formation conditions, as well as the imbibition process of the residual fracturing fluid in the formation as an imbibition oil displacement agent after fracturing, and measure the imbibition oil displacement effect of different imbibition oil displacement agents added to the fracturing fluid. The experimental device uses a one-way injection and production method to simulate the imbibition in the displacement process, and cannot reflect the function of the imbibition agent replacing crude oil through spontaneous imbibition during oil well huff and puff.

[0007] The above prior art mainly has the following three problems:

[0008] (1) Most experimental devices are composed of imbibition bottles or imbibition chambers. They simulate the imbibition during displacement by unidirectional injection and production. However, they cannot reflect the function of the imbibition agent to replace crude oil through spontaneous imbibition during well huff and puff.

[0009] (2) In actual oil layers, after being injected, the imbibition agent usually enters the micropores along the wall of the seepage channel in the form of a discontinuous phase, thereby imbibing and replacing crude oil. In existing experiments simulating the imbibition process, the imbibition agent is made to directly contact the oil sand or oil-bearing core in the form of a continuous phase at the injection end, which cannot accurately simulate the imbibition phenomenon in the reservoir.

[0010] (3) The conventional evaluation method of the imbibition capacity of the imbibition agent is generally to calculate the imbibition recovery degree by the volume method or the mass method, and to evaluate the imbibition effect by the imbibition recovery degree. However, the recovery degree is affected by factors such as the fluidity and emulsification carrying capacity of the imbibition agent, and does not represent its true imbibition capacity.

[0011] At present, there is no experimental method to simulate spontaneous imbibition during the huff and puff process of oil wells and no method to evaluate the effect of imbibition agents. Therefore, establishing a set of research and evaluation methods for the huff and puff oil recovery effect of imbibition agents is crucial for the identification of imbibition capacity and has practical significance in field applications. Summary of the invention

[0012] The purpose of the present invention is to provide an imbibition agent throughput experimental device and an evaluation method, which can truly simulate the process of imbibition agent throughput in oil wells under reservoir conditions, and study and evaluate the spontaneous imbibition and oil production phenomenon of the imbibition agent during the throughput process, providing a theoretical indoor theoretical basis for field applications.

[0013] To achieve the above object, the present invention provides the following technical solutions:

[0014] A permeate throughput experimental device comprises a thermostatic box, wherein a core holder and a permeate piston container are arranged in the thermostatic box; the core holder can accommodate a plurality of core samples placed in sequence; two ports of the core holder are respectively connected to the permeate piston container; the permeate piston container is connected to an ISCO displacement pump arranged outside the thermostatic box; and the core holder is connected to an annular pressure monitoring pump arranged outside the thermostatic box.

[0015] As a preferred embodiment, three core samples are sequentially placed in the core holder, wherein the middle core sample is saturated with crude oil, and the core samples on the left and right sides are saturated with imbibition agent.

[0016] As a preferred embodiment, the length of the inner cavity of the core holder is 30 cm, and the length of each core sample is 10 cm.

[0017] As a preferred embodiment, valves are also provided at the two ports of the core holder.

[0018] As another object of the present invention, the present invention also provides a method for evaluating the spontaneous imbibition effect of an imbibition agent using the above-mentioned imbibition agent throughput experimental device, comprising the following steps:

[0019] (1) Select three cylindrical core samples from the same block as the test samples, which are required to have the same physical properties and size specifications;

[0020] (2) vacuuming the second core sample and saturating the sample with crude oil, and vacuuming the first core sample and the third core sample and saturating the sample with imbibition agent;

[0021] (3) placing the first core sample, the second core sample and the third core sample in a core holder in sequence, placing them in a constant temperature box, and setting the detection pressure of the ring pressure monitoring pump;

[0022] (4) Start the ISCO displacement pump and inject the imbibition agent into the two ports of the core holder through the imbibition agent piston container. When the injection pressure reaches the spontaneous imbibition starting pressure, close the valves at both ends of the holder to simulate the well soaking process after the injection.

[0023] (5) After the soaking, the first and third core samples are taken out for slicing, and the oil marks on the sliced ​​sections at different distances from the second core sample are observed, so as to evaluate the imbibition capacity of the imbibition agent.

[0024] As a preferred implementation, in step (3), the ambient pressure of the core holder is required to be always 2 MPa higher than the pressure in the core cavity.

[0025] As a preferred implementation, when the injection pressure in step (4) reaches 0.5 MPa, the valves at both ends of the clamp are closed.

[0026] As a preferred implementation, the time for simulating the well blocking in step (4) is 48-72 hours.

[0027] As a preferred embodiment, in the step (5), the first core sample and the third core sample are cut into 3 mm thin slices, and the slices are numbered in order from near to far from the second core sample. The end faces of the slices are observed using a fluorescence microscope, and the number x of the farthest slice where the oil stain can be continuously observed is used as a standard for evaluating the imbibition capacity of the imbibition agent. The larger the number value, the longer the imbibition front edge, and the stronger the imbibition capacity and replacement efficiency of the imbibition agent.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention places three sections of cores saturated with crude oil and imbibition agents respectively in a core holder, and then bidirectionally pressurizes and then shuts the well, so as to simulate the process of spontaneous imbibition and oil production of discontinuous phase imbibition agents during the huff and puff of an oil well. The present invention provides an evaluation method for the spontaneous imbibition effect of an imbibition agent, which can horizontally and quantitatively compare the effects of spontaneous imbibition and replacement of crude oil by different imbibition agents under the same reservoir conditions, and provide a theoretical indoor theoretical basis for field application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a connection schematic diagram of the imbibition agent throughput experimental device of the present invention;

[0031] Figure 2 The slicing result of the first core sample in Example 1, wherein from left to right are schematic diagrams of the slicing results of No. 1, 6, 7, and 8;

[0032] In the figure, 1-constant temperature box; 2-ISCO displacement pump; 3-imbibition agent piston container; 4-core holder; 5-annular pressure monitoring pump; 6-six-way; 7-first core sample; 8-second core sample; 9-third core sample. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] Three cylindrical core samples (marked as #1, #2, and #3) were selected from the same block, all with a size of φ2.5×10 cm and a permeability of 50×10 -3 μm2 The porosity is 17%. The cores #1 and #3 were vacuumed and saturated with petroleum sulfonate solution; the core #2 was vacuumed and saturated with crude oil. The cores #1, #2, and #3 were placed in a 30 cm long core holder in the order of #1, #2, and #3, and placed in a constant temperature box. Figure 1 Connect the equipment. Set up annular pressure monitoring to keep the annular pressure always higher than the pressure in the core cavity by 2MPa. Inject petroleum sulfonate at both ends simultaneously. When the injection pressure reaches 0.5MPa, close the valves at both ends of the clamp and soak the well for 72h. After soaking, take out the cores and cut the #1 and #3 cores into thin slices of about 3mm respectively. Excluding cutting loss, each core can be cut into about 30 slices. Number the slices from near to far from the #2 core. Use a fluorescent microscope to observe the end face of the slice, and use the farthest slice number where the oil stain can be continuously observed as the standard for evaluating the imbibition ability of the imbibition agent. Figure 2 The slicing results of core #1 are shown (the slicing results of core #3 are the same as those of core #1 and are not repeated here). From left to right, they are slices 1, 6, 7, and 8. Slice 7 is the farthest slice where oil traces can be observed, and the 72-hour imbibition capacity of petroleum sulfonate can be evaluated as level 7.

[0036] Example 2

[0037] See the osmotic agent throughput experimental device for Figure 1 Three cylindrical cores #1, #2, and #3 were selected from the same block, all with dimensions of φ3.8×10 cm and permeabilities of 70×10 -3 μm 2 The porosity is 19%. The cores #1 and #3 are vacuumed and saturated with water; the core #2 is vacuumed and saturated with crude oil. The cores #1, #2, and #3 are placed in a 30 cm long core holder in the order of #1, #2, and #3, and placed in a constant temperature box. Figure 1 Connect the equipment. Set up annular pressure monitoring to keep the annular pressure always higher than the pressure in the core cavity by 2MPa. Inject clean water at both ends simultaneously. When the injection pressure reaches 0.5MPa, close the valves at both ends of the clamp and stew the well for 72h. After stewing, take out the cores and cut the #1 and #3 cores into thin slices of about 3mm respectively. Excluding cutting loss, each core can be cut into about 30 slices. Number the slices from near to far from the #2 core. Use a fluorescent microscope to observe the end face of the slice, and use the farthest slice number where oil stains can be continuously observed as the standard for evaluating the imbibition capacity of the imbibition agent. The slice results of both #1 and #3 cores are slice No. 1, and the imbibition capacity of clean water for 72 hours can be evaluated as level 1.

[0038] Example 3

[0039] See the osmotic agent throughput experimental device for Figure 1As shown. Three cylindrical cores #1, #2, and #3 were selected from the same block, all with dimensions of φ2.5×15cm, permeability of 200×10-3μm2, and porosity of 22%. Cores #1 and #3 were vacuumed and saturated with betaine solution; core #2 was vacuumed and saturated with crude oil. The cores were placed in a 30cm long core holder in the order of #1, #2, and #3, and placed in a constant temperature box. Figure 1 Connect the equipment. Set up annular pressure monitoring to keep the annular pressure always higher than the pressure in the core cavity by 2MPa. Inject betaine solution at both ends simultaneously. When the injection pressure reaches 0.5MPa, close the valves at both ends of the clamp and stew for 72 hours. After stewing, take out the cores and cut the #1 and #3 cores into thin slices of about 3mm respectively. Excluding cutting loss, each core can be cut into about 50 slices. Number the slices from near to far from the #2 core. Use a fluorescence microscope to observe the end face of the slice, and use the farthest slice number where the oil stain can be continuously observed as the standard for evaluating the imbibition capacity of the imbibition agent. The slice results of both #1 and #3 cores are slice No. 5, and the 72-hour imbibition capacity of betaine can be evaluated as level 5.

[0040] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating the spontaneous imbibition effect of an imbibition agent using an imbibition agent throughput experimental device, characterized in that: The imbibition agent throughput experimental device comprises a thermostatic box, in which a core holder and an imbibition agent piston container are arranged; the core holder can accommodate a plurality of core samples placed in sequence; two ports of the core holder are respectively connected to the imbibition agent piston container; the imbibition agent piston container is connected to an ISCO displacement pump arranged outside the thermostatic box; the core holder is connected to an annular pressure monitoring pump arranged outside the thermostatic box, and valves are also arranged at the two ports of the core holder; The steps include: (1) Select three cylindrical core samples from the same block as the test samples, which are required to have the same physical properties and size specifications; (2) the second core sample is saturated with crude oil after being vacuumed, and the first core sample and the third core sample are saturated with imbibition agent after being vacuumed; (3) placing the first core sample, the second core sample and the third core sample in a core holder in sequence, placing them in a constant temperature box, and setting the detection pressure of the ring pressure monitoring pump; (4) Start the ISCO displacement pump and inject the imbibition agent into the two ports of the core holder through the imbibition agent piston container. When the injection pressure reaches the spontaneous imbibition starting pressure, close the valves at both ends of the holder to simulate the well soaking process after the huff-and-puff injection. (5) After soaking, the first and third core samples are taken out for slicing. The oil marks on the sliced ​​sections at different distances from the second core sample are observed to evaluate the imbibition capacity of the imbibition agent.

2. The method according to claim 1, characterized in that The length of the inner cavity of the core holder is 30 cm, and the length of each core sample is 10 cm.

3. The method according to claim 1, characterized in that In step (3), the ambient pressure of the core holder is required to be always higher than the pressure in the core cavity by 2 MPa.

4. The method according to claim 1, characterized in that When the injection pressure in step (4) reaches 0.5 MPa, the valves at both ends of the clamp are closed.

5. The method according to claim 1, characterized in that The time for simulating the well blocking in step (4) is 48-72 hours.

6. The method according to claim 1, characterized in that: In the step (5), the first core sample and the third core sample are cut into 3 mm thin slices, and the slices are numbered in order from near to far from the second core sample. The end faces of the slices are observed using a fluorescence microscope, and the number x of the farthest slice where the oil stain can be continuously observed is used as a standard for evaluating the imbibition ability of the imbibition agent. The larger the number value, the longer the imbibition front edge, and the stronger the imbibition ability and replacement efficiency of the imbibition agent.

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