Pressure conduction experiment method for effective displacement system of oil-water well

Abstract

The invention belongs to the field of pressure displacement systems, and discloses a pressure conduction experiment method for an effective displacement system of an oil-water well. Comprising the steps of core pretreatment, laboratory pretreatment, pressure conduction experiment and pressure relief experiment. By utilizing the achievement of the invention, pressure conduction experiments and pressure relief experiments of other unconventional reservoirs such as tight reservoirs and shale oil reservoirs can be carried out, and a direction is indicated for exploration and development of the unconventional reservoirs in the future.

Description

Technical Field

[0001] The invention belongs to the field of pressure displacement systems, and in particular relates to a pressure conduction experimental method for an effective displacement system of an oil and water well. Background Art

[0002] With the continuous development of unconventional reservoirs, various displacement methods such as chemical flooding, CO2 flooding, and nitrogen flooding have gradually become popular. However, water injection development is still the main development method used in many areas of the oil field. In conventional reservoirs, the relationship between oil and water wells has been successfully understood. However, in unconventional reservoirs, the displacement system between oil and water wells has not been effectively evaluated and understood. This requires the development of a new method for evaluating the displacement system between oil and water wells. Summary of the Invention

[0003] In order to overcome the shortcomings of the existing technology, the present invention provides a pressure conduction experimental method for an effective oil-water well displacement system. Through a new idea, necessary improvements are made to the water-to-oil experimental process and parameter adjustment during the experiment, forming an unconventional reservoir pressure conduction experimental technology.

[0004] The above object of the present invention is achieved through the following technical solution: a pressure conduction experimental method for an effective displacement system of an oil and water well, comprising the following steps:

[0005] 1. Core pretreatment;

[0006] 2. Laboratory pre-treatment;

[0007] 3. Pressure conduction experiment;

[0008] 4. Pressure relief test.

[0009] Furthermore, the specific operation of step 1 is: drilling a core in a horizontal direction, cutting the core into core columns, washing the core with ethanol and benzene to reach a fluorescence level of 3 or above, and drying.

[0010] In a further preferred embodiment of the present invention, the core column cut in step 1 has a diameter of 2.5 cm and a length of at least 4.5 cm.

[0011] In a further preferred embodiment of the present invention, the specific parameters of the drying operation in step 1 are: drying in a constant temperature drying oven at 90° C. for more than 8 hours.

[0012] Furthermore, the specific operations of step 2 are: measuring the gas permeability of the core, weighing the dry weight, vacuuming, saturating the simulated formation water with the same salinity as the formation water for more than 6 hours, turning off the vacuum pump, and venting to prevent the formation water from flowing back into the vacuum pump.

[0013] In a further preferred embodiment of the present invention, the specific operation of vacuuming in step 2 is: vacuuming with a vacuum degree of -0.1 MPa using a vacuum pump.

[0014] Furthermore, the specific operations of step 3 are: setting the temperature of the thermostat to the formation temperature, maintaining a constant pressure at the core inlet, maintaining a certain back pressure at the core outlet, conducting a pressure conduction experiment, recording the experimental time required for the inlet and outlet pressures to balance, and conducting comparative experiments at 1 MPa and 0.5 MPa respectively.

[0015] Furthermore, the specific operation of step 4 is: setting the temperature of the constant temperature box to the formation temperature, the pressure at the core inlet to 1 MPa, the core outlet directly to the atmosphere, conducting a pressure relief experiment, and recording the experimental time required for the outlet pressure to return to zero.

[0016] Compared with the prior art, the present invention has the following advantages: the present invention adopts a new idea to make detailed requirements on the key nodes in each experimental step, usually 0.1×10 -3 μm 2 While the production of unconventional reservoirs is extremely poor, a certain pressure transmission velocity exists, which can serve as the lower limit for water injection development in unconventional reservoirs. The connectivity of fine pores and microthroats in unconventional reservoirs and the extremely low seepage velocity are the most critical factors affecting oil well production. This invention can be used to conduct pressure transmission and pressure relief experiments in other unconventional reservoirs, such as tight reservoirs and shale oil reservoirs, and provide guidance for future exploration and development of unconventional reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1 0.1×10 -3 μm 2 Core time and pressure transmission relationship diagram;

[0019] Figure 2 This is the 1MPa pressure conduction experiment curve;

[0020] Figure 3 This is the 0.5MPa pressure conduction experiment curve;

[0021] Figure 4 This is the pressure conduction experiment curve of the 1MPa pressure relief process. DETAILED DESCRIPTION

[0022] The present invention is described in detail below by specific examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0023] Example 1

[0024] (1) Experimental study on the lower limit of permeability development

[0025] Using mercury injection data from an external partner, the lower limit of permeability that can be effectively developed in unconventional reservoirs is 0.1×10 -3 μm 2 The present invention carried out a pressure conduction experiment simulating formation conditions, and the experimental results are shown in Figure 1 During the experiment, the pressure at the front end of the core was set at 1 MPa, and the back end was open to the atmosphere.

[0026] Figure 1 It can be seen that under the formation conditions, the time required for the core to conduct 0.01MPa pressure is more than 6 days, and there is also a certain pressure fluctuation period. The converted theoretical conduction velocity is 102 days / m, 0.1×10 -3 μm 2 The exploitation effect of unconventional reservoirs is extremely poor, but there is also a certain pressure conduction velocity, which can be used as the lower limit of unconventional reservoir water injection development.

[0027] (2) 1MPa pressure conduction experiment

[0028] The core inlet maintains a constant pressure of 1 MPa, the core outlet maintains a certain back pressure, and the time required for the pressure at both ends of the core to balance is measured. The experimental results are shown in Figure 2 .

[0029] The average pressure gradient across these cores is 18 MPa / m, indicating pressure dissipation near the wellbore. Air permeability and pressure transmission velocity are poorly correlated, and the distribution and frequency of effective seepage channels determine reservoir permeability. This suggests that water injection fingering also occurs in unconventional reservoirs.

[0030] (3) 0.5MPa pressure conduction test

[0031] The core inlet maintains a constant pressure of 0.5 MPa, the core outlet maintains a certain back pressure, and the time required for the pressure at both ends of the core to balance is measured. The experimental results are shown in Figure 3 .

[0032] The conduction velocity decreases, and the conclusion is similar to that of 1MPa. If the experimental guidance is used for field water injection, the permeability is 0.46×10 -3 μm 2 The reservoir has an injection pressure of 18 MPa. It takes at least 36 days for the injected water to advance 1 m in the reservoir. The pressure conduction rate is extremely low, which is the main reason for the low oil production rate in unconventional reservoirs.

[0033] (4) 1MPa pressure relief test

[0034] A pressure of 1 MPa was applied to the core inlet, and the outlet was open to the atmosphere. The time required for pressure relief was recorded. -3 μm 2 In the reservoir, during the pressure relief process, the time required for the fluid to seep 1 meter underground is more than 80 days.

[0035] The experimental results, combined with the well's production, show that the pressure relief rate near the wellbore is much lower than that observed under laboratory conditions. The seepage area within the reservoir is very small, and pressure relief occurs primarily in the high-permeability layer. Formation pressure is maintained in the reservoir 1 meter beyond the fracture.

[0036] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A pressure conduction experimental method for an effective displacement system of an oil and water well, characterized in that: Here are the steps: S1. Core pretreatment; S2. Laboratory pre-processing; S3. Pressure conduction experiment; S4. Pressure relief test.

2. The pressure conduction experimental method for an effective displacement system of an oil and water well according to claim 1, characterized in that: The specific operations of step S1 are: drilling a core in a horizontal direction, cutting the core into core columns, washing the core with ethanol and benzene until the fluorescence reaches level 3 or above, and drying the core columns.

3. The pressure conduction experimental method for an effective displacement system of an oil and water well according to claim 2, characterized in that: The core column cut in step S1 has a diameter of 2.5 cm and a length of more than 4.5 cm.

4. The pressure conduction experimental method for an effective displacement system of an oil and water well according to claim 2, characterized in that: The specific parameters of the drying operation in step S1 are: drying in a constant temperature drying oven at 90° C. for more than 8 hours.

5. The pressure conduction experimental method for an effective displacement system of an oil and water well according to claim 1, characterized in that: The step S2 measures the gas permeability of the core, weighs the dry weight, evacuates the core, saturates the core with simulated formation water with the same salinity as the formation water for more than 6 hours, turns off the vacuum pump, and vents the core to prevent formation water from flowing back into the vacuum pump.

6. The pressure conduction experimental method for an effective displacement system of an oil and water well according to claim 5, characterized in that: The specific operation of vacuuming in step S2 is: vacuuming with a vacuum pump at a vacuum degree of -0.1 MPa.

7. The pressure conduction experimental method for an effective displacement system of an oil and water well according to claim 1, characterized in that: The specific operations of step S3 are as follows: setting the temperature of the thermostat to the formation temperature, maintaining a constant pressure at the core inlet and a certain back pressure at the core outlet, conducting a pressure conduction experiment, recording the experimental time required for the inlet and outlet pressures to balance, and conducting comparative experiments at 1 MPa and 0.5 MPa respectively.

8. The pressure conduction test method for an effective oil-water well displacement system according to claim 1, characterized in that: The specific operation of step S4 is: setting the temperature of the thermostat to the formation temperature, the pressure at the core inlet to 1 MPa, the core outlet directly to the atmosphere, conducting a pressure relief experiment, and recording the experimental time required for the outlet pressure to return to zero.

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