Full-diameter long core oil washing method

Abstract

The invention relates to a full-diameter long rock core oil washing method which comprises the following steps: placing a rock core in a constant-temperature box to enable soluble substances in the rock core to be in a flowing state, then placing the full-diameter long rock core in a full-diameter rock core holder again, establishing an oil washing process, and removing impurities and crude oil contained in the rock core by adopting an oil washing agent reciprocating displacement mode. And multiple rounds of oil washing are carried out through the oil washing agent, one round of oil displacement is set as six cycles, and the oil washing agent in the intermediate container is sampled after each round of oil washing is finished until the oil washing qualification standard is reached. The oil washing method is simple and convenient, the oil washing efficiency can be greatly improved, oil washing is convenient, good sealing performance is achieved, the used oil washing agent is low in price and easy to obtain, and the oil washing cost is reduced.

Description

Technical Field

[0001] The invention belongs to a safe and efficient oil washing method for natural full-diameter cores or artificial cores in the field of core analysis in the petroleum industry, and specifically relates to an oil washing method for full-diameter long cores. Background Art

[0002] In the oilfield exploration and development plan, indoor core experiments can analyze the production laws of oilfields in specific development blocks, which has important guiding significance for the formulation of its development plan. Before the oilfield development block, it is necessary to obtain full-diameter core samples through drilling coring technology, and conduct core-related experiments indoors to test and obtain experimental data such as the permeability and porosity of the core in the development formation of the block, so as to analyze the physical and chemical properties of the core. Therefore, in some experiments of oilfield exploration and development, core oil washing is an important part of the preliminary treatment, the purpose is to clean and remove the crude oil and impurities contained in the core, and ensure the smooth progress of subsequent experiments. From the current point of view, there are two main methods of oil washing: the first is to unidirectionally displace polymers, surfactants, toluene, etc. into the core holder; however, the unidirectional oil washing method is not efficient, the oil washing agent is expensive and difficult to obtain, and toluene itself has toxic and volatile properties, and must be operated in a sealed manner, otherwise it is easy to endanger the health of the experimenters. The second method is to use centrifugal method to remove impurities in the core with a certain kinetic energy. This method has certain power advantages, but it is greatly affected by the core permeability and the cleaning degree is relatively low. No matter which method is used, it is impossible to carry out the full diameter core length of 80cm and diameter of 10cm. Summary of the invention

[0003] The purpose of the present invention is to provide a full-diameter long core oil washing method, which is used to solve the problem that the existing technology cannot perform oil washing on a full-diameter long core with a length of 80 cm and a diameter of 10 cm, and the oil washing efficiency is slow and the oil washing effect is poor.

[0004] The technical solution adopted by the present invention to solve the technical problem is: the full-diameter long core oil washing method comprises the following steps: (1) Use drilling coring technology to obtain full-diameter long cores. The cores are columnar natural cores with a length of 80-85 cm and a diameter of 10 cm. Measure the core diameter, length, and dry weight to obtain core basic data; (2) Place the full-diameter long core in a constant temperature box and set the heating temperature to 104°C for 12 hours to make the soluble matter in the core flowable; (3) placing the full-diameter long core in a full-diameter core holder, and connecting it to a permeability tester to perform gas permeability testing under the conditions of a confining pressure of 2 MPa, room temperature, and no heat shrinkage; (4) Put the full-diameter long core and the plunger into the heat shrink tube, heat and wrap them tightly with the heat shrink tube, and weigh the dry weight of the core and the plunger after heat shrinkage as 1; (5) placing the full-diameter long core in a core holder, connecting it to a high-efficiency vacuum pump through a high-pressure pipeline under a confining pressure of 2 MPa and room temperature, and saturating the core with oil by self-priming for 12 hours; (6) After full saturation, take out the full-diameter long core and weigh the wet weight together with the plunger to calculate the initial porosity; (7) placing the full-diameter long core back into the full-diameter core holder, establishing an oil washing process, using an oil washing agent reciprocating displacement method to remove impurities and crude oil contained in the core, performing multiple rounds of oil washing with the oil washing agent, setting one round of oil driving to 6 cycles, and sampling the oil washing agent in the piston container after each round; (8) Compare the colors of the oil washing agent sampled in the piston container in each round until the oil washing is determined to be complete; after the oil washing process is completed, remove the heat shrink tube wrapped around the core surface and the plungers at both ends of the full-diameter core holder to weigh the wet weight 2, and finally place the core that has completed the oil washing process outdoors for 12 hours; (9) The core was then placed in a thermostatic box and the heating temperature was set to 102°C-104°C for 24 hours. The dry weight 2 was weighed and combined with the wet weight 2 to calculate the porosity after oil washing. Finally, the dried core was placed in a core holder at a confining pressure of 2 MPa without heating, and gas permeability was measured.

[0005] The heat shrink sleeve in step (5) of the above scheme is a polytetrafluoroethylene heat shrink sleeve.

[0006] The oil washing agent in step (7) of the above scheme is No. 120 gasoline.

[0007] The oil washing process in step (7) of the above scheme is carried out in a reciprocating circulation displacement mechanism, which includes a full-diameter core holder, a first piston container, a second piston container, a first four-way valve, a second four-way valve, a displacement power source and a confining pressure power source. A heating and temperature control system is arranged on the full-diameter core holder, and the heating and temperature control system is equipped with a nano-heating coil and a temperature sensor for measuring the full-diameter core holder. The full-diameter core holder is arranged on a fixed frame; the confining pressure power source is composed of a high-pressure pump connected to the full-diameter core holder through a high-pressure pipeline to provide radial pressure to the core; The two ends of the full-diameter core clamp are respectively connected with the first piston container and the second piston container through high-pressure pipelines. The first piston container is filled with oil washing agent. The lower end of the first piston container is connected with the first four-way valve, and the lower end of the piston of the second piston container is connected with the second four-way valve. The displacement power source is composed of the first four-way valve and the second four-way valve connected to the high-pressure gas cylinder by high-pressure pipelines. The first piston container, the first four-way valve, the full-diameter core clamp, the second piston container, the second four-way valve, and the displacement power source constitute a reciprocating circulation loop, and the valves arranged on each high-pressure pipeline in the loop are equipped with pressure sensors.

[0008] In the above scheme, the full-diameter core holder is heated to 50-60° C. by a heating temperature control system.

[0009] In the above scheme, a pressure sensor is installed at the outlet end of the full-diameter core holder, and the pressure sensor is installed on the high-pressure pipeline connected to the outlet end of the core.

[0010] In the above solution, one valve port of the first four-way valve is connected to the first beaker; and one valve port of the second four-way valve is connected to the second beaker.

[0011] The full-diameter long core oil washing method of the present invention has the following beneficial effects: 1. The oil washing agent of the present invention adopts No. 120 gasoline, which is low in price and easy to obtain. It is not easy to cause melting catalysis to the rubber sleeve in the full-diameter core holder, and prolongs the service life of the experimental sealing rubber sleeve. In addition, this oil washing agent is not easy to react with the crude oil in the core, thereby reducing the change of the original properties of the core, providing an accurate basis for subsequent indoor experiments.

[0012] 2. The present invention uses a heat shrink tube to heat shrink the core to avoid contact between the oil washing agent and the sealing rubber sleeve, and reduces the contact between the experimenter and the oil washed core, which is beneficial to the health of the experimenter. The heat shrink sleeve wrapped on the surface of the core increases the contact area between the core and the sealing rubber sleeve, ensuring airtightness during the entire experiment, thereby maximizing the oil washing effect.

[0013] 3. The full-diameter core holder used in the oil washing process of the present invention overcomes the problem of small size of the core for oil washing. At the same time, the core holder can wash oil at multiple angles, such as vertically, which can greatly speed up the oil washing efficiency.

[0014] 4. The core oil washing method of the present invention is simple, easy to operate, and has good sealing performance. The reciprocating cycle oil washing method can effectively remove the crude oil and soluble matter in the core, shorten the oil washing time to the greatest extent, and achieve a good oil washing effect.

[0015] 5. The present invention washes the core oil based on the reciprocating cycle displacement method, and overcomes the problem of the small size of the existing core oil washing. The experimental process is simple and convenient to operate, and can effectively improve the oil washing efficiency. The oil washing agent is cheap and easy to obtain. By wrapping the full-diameter long core with a heat shrink tube, the contact between the experimenter and the oil washing agent can be greatly reduced to avoid affecting health. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the oil washing process structure of the full-diameter long core oil washing method; Figure 2 It is a schematic diagram of the vacuum saturation process structure of the full-diameter long core oil washing method.

[0017] Numbers in the figure: 1-high-pressure gas cylinder; 2-full-diameter core holder; 3-high-pressure pump; 4-first piston container; 5-second piston container; 6-heating temperature control system; 7-pressure sensor; 8-first four-way valve; 9-second four-way valve; 81-first displacement valve; 91-second displacement valve; 82-first signal valve, 92-second signal valve; 10-first beaker, 11-second beaker; 12-high-efficiency vacuum pump. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the embodiments described in the accompanying drawings, but the present invention is not limited to the scope of the embodiments, which is only indicated by the scope of the claims.

[0019] The novel method for washing oil from a full-diameter long core of the present invention is described below in conjunction with specific embodiments.

[0020] Combination Figure 1-2 As shown, the novel method for washing oil from a full-diameter long core of the present invention comprises the following steps: (1) A natural full-diameter cylindrical core of the size required for the experiment is obtained by drilling and coring. The natural long core obtained can be 10 cm in diameter and 65 to 85 cm in length according to the clamping size of the full-diameter core holder 2 for indoor experiments; (2) placing the full-diameter long core obtained in step (1) in a constant temperature box, setting the heating temperature to 104° C. and the heating time to 12 hours, so that the crude oil and solubles in the core are in a flowable state; (3) placing the full-diameter long core obtained in step (1) in a full-diameter core holder 2, and performing gas permeability measurement under the conditions of a confining pressure of 2 MPa, room temperature, and no thermal shrinkage; (4) Place the plungers at both ends of the full-diameter long core in step (1), heat and wrap them tightly with a heat shrink sleeve, and weigh the dry weight of the plunger after heat shrinkage as 1; (5) placing the full-diameter long core in step (1) in a full-diameter core holder 2, and connecting it to a high-efficiency vacuum pump 12 through a high-pressure pipeline under the conditions of a confining pressure of 2 MPa and room temperature, so that the core is in a negative pressure vacuum state, and then saturating the core with oil by self-priming, and the saturation time is 12 hours; (6) After the core is fully saturated, take out the core in the full-diameter core holder 2 in step (5), weigh the wet weight 1 together with the plunger, and calculate the initial porosity; (7)Reference Figure 1 As shown, the full-diameter long core in step (6) is installed in the full-diameter core holder. The size of the full-diameter core holder 2 is 40 cm in diameter and 120 cm in length. Its structure includes a heat shrink rubber sleeve wrapped around the core in the holder, a holder body, plungers at both ends of the inlet and outlet, and the core holder is mounted on a fixed frame that can rotate radially. The high-pressure pump 3 is used to inject water into the inner space of the full-diameter core holder to form a confining pressure. Then, pressurization can be used to make the core tightly wrapped by the heat shrink rubber sleeve. At the same time, the heat shrink sleeve wrapped on the surface of the core can prevent the oil washing agent from contacting the sealing rubber sleeve, so that the oil washing agent can only flow through the core in the full-diameter core holder from the inlet end; a pressure sensor 7 is installed at the outlet end of the full-diameter core holder, and the pressure sensor 7 is installed on the high-pressure pipeline connected to the outlet end of the core. Start the heating and temperature control system 6, set the temperature at 50°C and keep it constant, and at the same time, fill the first piston container 4 set at the left end of the full-diameter core holder 2 with the oil washing agent. Open the first displacement valve 81 and the second signal valve 92, and close the first signal valve 82 and the second displacement valve 91. Open the high-pressure gas cylinder 1 for displacement, and the oil washing agent flows through the core in the full-diameter core clamp and flows into the second piston container 5. At this time, bubbles are generated in the second beaker 11. After the bubbles disappear completely, close the first displacement valve 81 and the second signal valve 92, and open the first signal valve 82 and the second displacement valve 91. The oil washing agent flows from the second piston container 5 through the core and then flows back to the first piston container 4. At this time, bubbles are generated in the first beaker 10. When the bubbles disappear completely, one cycle is completed. Repeat this operation to perform a reciprocating displacement method to remove impurities and crude oil contained in the core. Set one round of oil drive to 6 cycles, and sample the oil washing agent after each round; (8) According to the color comparison of the oil washing agent sampled in each round of the first piston container 4 in step (7) until the oil washing is determined to be completed; after the oil washing process is completed, the heat shrink sleeve wrapped around the core surface and the plungers at both ends of the full-diameter core holder are removed to weigh the wet weight 2, and finally the core that has completed the oil washing process is placed outdoors and left to stand for 12 hours; (9) The core is then placed in a constant temperature box at 104°C for 24 hours; the dry weight 2 is weighed and combined with the wet weight 2 to calculate the porosity after oil washing; finally, the dried core is placed in a core holder 2 at a confining pressure of 2 MPa without heating, and gas permeability is measured.

[0021] The present invention places a first piston container 4 and a second piston container 5 at both ends of a full-diameter core holder 2. The first piston container 4 is filled with an oil washing agent, and a channel for the oil washing agent is established in the core to form a reciprocating oil washing mode, thereby greatly improving the working efficiency. Example

[0022] In order to conduct indoor experiments on porosity and permeability of full-diameter long cores before and after oil washing in a certain oil field development block, the cores must be subjected to oil washing treatment. The full-diameter long cores are sandstones with a core diameter of 10 cm, a length of 82 cm, and a dry weight of 12348 g. The oil is washed according to the above-mentioned oil washing method of the present invention.

[0023] Place No. 120 gasoline in the left piston container, place the dried full-diameter core in the full-diameter core holder, and measure the permeability under the conditions of no heat shrinkage, constant temperature, and confining pressure of 2MPa; after heat shrinkage, weigh the dry weight 1 with the plunger, and then vacuum the full-diameter core to saturate it with oil; after full saturation, take out the core, weigh the wet weight 1 with the plunger, and calculate the initial porosity; by re-placing the full-diameter core in the core holder, the confining pressure is 2MPa, the temperature is 50℃, and the oil washing agent is 4L, the reciprocating oil washing channel is completed, and then multiple rounds of washing are performed. The oil flow chart is as follows: one round of oil flooding is set to 6 cycles, and the washed oil is sampled after each round. It is estimated that 6 to 8 rounds of oil washing will be carried out. According to the color of the oil washing agent sampling, comprehensive comparison and photography are taken to determine the end of oil washing. The cores after oil washing are taken out, and the heat shrink sleeve and plunger are removed to weigh the wet weight 2. The washed cores are placed outdoors for 12 hours. The cores are then placed in a constant temperature box at 104°C for 24 hours. The dry weight 2 is weighed, and the porosity after oil washing is calculated by combining the wet weight 2. The dried cores are placed in a core holder at a confining pressure of 2MPa, and the permeability is measured by gas measurement without heating.

[0024] The full-diameter core was subjected to 6 rounds of oil washing, and the permeability before and after oil washing was 495.01mD and 623.81mD, and the porosity was 14.95% and 18.84%. This indicates that the present invention effectively removes crude oil and soluble substances in the core. A comprehensive comparison of the sampling pictures shows that the color of the first round of oil washing samples is brown, and the color depth gradually decreases with the increase of oil washing rounds. The overall color is yellow, and the color change from 2 to 3 rounds is not significant. The color of the last round changes from brown to light yellow, which proves that the oil washing effect is better. At the same time, the whole process only takes 3 days, which greatly improves the oil washing efficiency.

[0025] The present invention adopts the drilling coring technology to obtain a long-diameter rock sample; after placing the core in a constant temperature box to make the soluble matter in the core flow, the full-diameter long core is placed back in a full-diameter core holder, an oil washing process is established, and an oil washing agent reciprocating displacement method is adopted to remove impurities and crude oil contained in the core. Multiple rounds of oil washing are performed by the oil washing agent, and one round of oil driving is set as 6 cycles. After each round, the oil washing agent in the intermediate container is sampled until the qualified standard of oil washing is reached; the core is then placed in a constant temperature box. The oil washing method of the present invention is simple and convenient, and can greatly improve the oil washing efficiency. The oil washing device has a simple structure, is convenient for oil washing, has good sealing performance, and the oil washing agent used is cheap and easy to obtain. The full-diameter core holder used in the oil washing process solves the problem that only smaller cores can be washed in the prior art. At the same time, the core holder can wash oil at multiple angles, which can greatly speed up the oil washing efficiency.

Claims

1. A full-diameter long core oil washing method, characterized in that The steps include: (1) Use drilling coring technology to obtain full-diameter long cores. The cores are columnar natural cores with a length of 80-85 cm and a diameter of 10 cm. Measure the core diameter, length, and dry weight to obtain core basic data; (2) Place the full-diameter long core in a constant temperature box and set the heating temperature to 104°C for 12 hours to make the soluble matter in the core flowable; (3) placing the full-diameter long core in a full-diameter core holder, and connecting it to a permeability tester to perform gas permeability testing under the conditions of a confining pressure of 2 MPa, room temperature, and no heat shrinkage; (4) Put the full-diameter long core and the plunger into the heat shrink tube, heat and wrap them tightly with the heat shrink tube, and weigh the dry weight of the core and the plunger after heat shrinkage as 1; (5) placing the full-diameter long core in a core holder, connecting it to a high-efficiency vacuum pump through a high-pressure pipeline under a confining pressure of 2 MPa and room temperature, and saturating the core with oil by self-priming for 12 hours; (6) After full saturation, take out the full-diameter long core and weigh the wet weight together with the plunger to calculate the initial porosity; (7) placing the full-diameter long core back into the full-diameter core holder, establishing an oil washing process, using an oil washing agent reciprocating displacement method to remove impurities and crude oil contained in the core, performing multiple rounds of oil washing with the oil washing agent, setting one round of oil driving to 6 cycles, and sampling the oil washing agent in the piston container after each round; (8) Compare the colors of the oil washing agent sampled in the piston container in each round until the oil washing is determined to be complete; after the oil washing process is completed, remove the heat shrink tube wrapped around the core surface and the plungers at both ends of the full-diameter core holder to weigh the wet weight 2, and finally place the core that has completed the oil washing process outdoors for 12 hours; (9) The core was then placed in a thermostatic box and the heating temperature was set to 102°C-104°C for 24 hours. The dry weight 2 was weighed and combined with the wet weight 2 to calculate the porosity after oil washing. Finally, the dried core was placed in a core holder at a confining pressure of 2 MPa without heating, and gas permeability was measured.

2. The full-diameter long core oil washing method according to claim 1, characterized in that: The heat shrink sleeve in step (5) is a polytetrafluoroethylene heat shrink sleeve.

3. The full-diameter long core oil washing method according to claim 2, characterized in that: The oil washing agent in step (7) is No. 120 gasoline.

4. The full-diameter long core oil washing method according to claim 3, characterized in that: The oil washing process in step (7) is carried out in a reciprocating circulation displacement mechanism, which includes a full-diameter core holder, a first piston container, a second piston container, a first four-way valve, a second four-way valve, a displacement power source and a confining pressure power source. The full-diameter core holder is provided with a heating and temperature control system, which is provided with a nano-heating coil and a temperature sensor for measuring the full-diameter core holder. The full-diameter core holder is arranged on a fixed frame; the confining pressure power source is composed of a high-pressure pump connected to the full-diameter core holder through a high-pressure pipeline to provide radial pressure to the core; the full-diameter core holder is provided with a heating and temperature control system, which is provided with a nano-heating coil and a temperature sensor for measuring the full-diameter core holder. The two ends of the full-diameter core clamp are respectively connected to the first piston container and the second piston container through high-pressure pipelines. The first piston container is filled with oil washing agent. The lower end of the first piston container is connected to the first four-way valve, and the lower end of the second piston container piston is connected to the second four-way valve; the displacement power source is composed of the first four-way valve and the second four-way valve connected to the high-pressure gas cylinder by high-pressure pipelines; the first piston container, the first four-way valve, the full-diameter core clamp, the second piston container, the second four-way valve, and the displacement power source constitute a reciprocating circulation loop, and the valves arranged on each high-pressure pipeline in the loop are equipped with pressure sensors.

5. The full-diameter long core oil washing method according to claim 4, characterized in that: The full-diameter core holder is heated to 50-60° C. by a heating temperature control system.

6. The full-diameter long core oil washing method according to claim 5, characterized in that: A pressure sensor is installed at the outlet end of the full-diameter core holder, and the pressure sensor is installed on the high-pressure pipeline connected to the outlet end of the core.

7. The full-diameter long core oil washing method according to claim 6, characterized in that: One valve port of the first four-way valve is connected to the first beaker; and one valve port of the second four-way valve is connected to the second beaker.

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