Packer and nitrogen composite heat insulation pipe column suitable for heavy oil thermal recovery and implementation process

Abstract

The invention belongs to the technical field of heavy oil thermal recovery, and discloses a packer suitable for heavy oil thermal recovery, a nitrogen composite heat insulation pipe column and an implementation process. The packer and nitrogen composite heat insulation pipe column comprises a constant pressure valve, a thermal recovery packer, a check valve, a compensator and a heat insulation oil pipe. In order to solve the problems of limitation of a thermal insulation technology of an existing thickened oil thermal production well, limited thermal insulation effect of a packer and the like, thermal insulation of the packer is combined with a nitrogen thermal insulation technology, a tubular column structure utilizing the thermal production packer, a check valve, a constant pressure valve and a thermal insulation oil pipe is designed, and a continuous and efficient thermal insulation process method is formed by matching with nitrogen injection. Longer-time intermittent injection of nitrogen can be achieved, the steam injection heat insulation effect is effectively improved, and meanwhile the nitrogen consumption can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy oil thermal recovery, and in particular relates to a packer and a nitrogen composite insulation pipe string suitable for heavy oil thermal recovery and an implementation process. Background Art

[0002] Currently, two insulation methods exist for heavy oil thermal recovery wells: nitrogen insulation and packer insulation. Both methods have shortcomings in practical application. Nitrogen insulation involves injecting nitrogen into the annulus formed between the exterior of the steam injection string and the interior of the casing during steam injection into the well to achieve thermal insulation between the two. The amount of nitrogen injected at a time is generally slightly larger than the annulus volume, and nitrogen injections are required two to three times during the entire main steam injection process. In actual production, the annulus volume between the oil and casing is relatively small, and formation pressure fluctuates constantly, leading to rapid nitrogen diffusion within the annulus. For thermal recovery wells within 1,000 meters, nitrogen in the annulus diffuses into the formation within approximately three hours, rendering it ineffective. Thermal recovery operations typically last between 3 and 20 days. Due to the high price of nitrogen, continuous nitrogen replenishment is not possible throughout the steam injection process. Consequently, nitrogen insulation is limited and cannot meet the requirements for long-term continuous insulation. During steam injection into an oil well, a packer is used to isolate the casing annulus using a packer, preventing steam from entering the annulus and achieving thermal insulation. However, before the packer is set, a certain amount of water typically remains in the annulus. Once the packer is set, this water is trapped within the annulus, compromising the annular insulation during steam injection. Therefore, it is necessary to develop a packer and nitrogen composite insulated string and process suitable for heavy oil thermal recovery to meet field requirements. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, the present invention provides a packer and nitrogen composite insulation string suitable for heavy oil thermal recovery, and its implementation process. Within the annular, enclosed space formed by the steam injection string, check valve, packer, and casing, high-purity nitrogen is used to displace the medium in the oil-casing annulus, filling the annulus with nitrogen. This ensures long-term, high-quality thermal insulation of the oil-casing annulus, minimizing heat loss and improving steam injection quality.

[0004] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0005] A packer and nitrogen composite insulated tubing string suitable for heavy oil thermal recovery comprises a constant pressure valve, a thermal recovery packer, a check valve, a compensator, and an insulated oil pipe, wherein the insulated oil pipe is arranged in an oil well, and the compensator and the check valve are arranged on the insulated oil pipe in sequence from top to bottom, a constant pressure valve is arranged at the bottom of the insulated oil pipe, and a thermal recovery packer is arranged on the lower outer end of the check valve, and the outer side of the oil well facing the lower end of the insulated oil pipe is an oil layer.

[0006] Furthermore, the packer and nitrogen composite insulation pipe string suitable for heavy oil thermal recovery, wherein the specification of the insulation oil pipe is Φ114mm.

[0007] Furthermore, the inner diameter of the oil well is Φ161 mm.

[0008] Furthermore, the pressure between the oil well and the insulated oil pipe is 15 MPa.

[0009] Furthermore, the pressure between the oil well and the insulated pipe is 273K.

[0010] The implementation process of the above-mentioned packer and nitrogen composite insulated tubing string suitable for heavy oil thermal recovery includes the following steps: lowering the insulated tubing string into the designed position, pressurizing it with a ground cement truck, injecting steam into the oil well, and when the pressure reaches the opening pressure of the pressure regulating valve, the thermal recovery packer is set, and the packer seals the annulus.

[0011] Furthermore, when steam is injected into the oil well, nitrogen is simultaneously injected into the casing annulus.

[0012] In a further preferred embodiment of the present invention, the displacement of nitrogen injected into the oil casing annulus is 800-1200 standard cubic meters per hour.

[0013] In a further preferred embodiment of the present invention, the amount of nitrogen injected into the casing annulus is calculated based on the volume of the casing annulus, and the amount of nitrogen injected is 20%-30% of the volume of the casing annulus.

[0014] Design basis:

[0015] For steam injection oil wells that require continuous and efficient insulation, high-purity nitrogen is used to replace the medium in the annulus, and then the nitrogen is sealed in the oil casing annulus with a packer. This can effectively improve the insulation effect and efficient insulation time of the steam injection string. At the same time, the volume of the oil pipe annulus is generally small, and the amount of nitrogen required is also very small. Therefore, this method has high economic applicability and is worthy of promotion and application.

[0016] Compared with the prior art, the present invention has the following advantages: in view of the limitations of the existing heavy oil thermal recovery well insulation technology and the limited insulation effect of the packer, the insulation of the packer is combined with the nitrogen insulation technology, and a pipe string structure is designed using a thermal recovery packer, a check valve, a constant pressure valve, and an insulated oil pipe. In combination with the injection of nitrogen, a continuous and efficient insulation process method is formed, which can realize intermittent injection of nitrogen for a longer time, effectively improve the steam injection insulation effect, and at the same time reduce the nitrogen consumption. 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 The diagram is a structural diagram of a packer and a nitrogen composite insulation pipe string suitable for heavy oil thermal recovery according to the present invention.

[0019] In the figure, 1. constant pressure valve; 2. thermal recovery packer; 3. check valve; 4. compensator; 5. insulated oil pipe; 6. oil well; 7. oil layer. DETAILED DESCRIPTION

[0020] 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.

[0021] Example 1

[0022] The insulation string is lowered into the designed position and pressurized by a cement truck on the ground. When the pressure reaches the opening pressure of the pressure regulating valve, the thermal recovery packer is set and the annulus is sealed by the packer.

[0023] During steam injection into an oil well, nitrogen is simultaneously injected into the annulus at a rate of 800-1200 standard cubic meters per hour, with the amount of nitrogen injected calculated based on the annulus volume. A 20%-30% excess nitrogen injection is typically used to ensure that all air and water in the annulus is expelled through the check valve, ensuring that the annulus is filled with high-purity nitrogen. The nitrogen in the annulus acts as a highly effective thermal insulation medium, improving the thermal insulation of the tubing string and also extending the service life of the packer seals. During the initial stages of steam injection into an oil well, the injected steam pressure is generally low, allowing excess nitrogen to enter the tubing through the check valve and into the formation along with the steam flow. After nitrogen injection is stopped, the check valve closes, leaving the annulus filled with high-purity nitrogen, achieving nitrogen insulation.

[0024] The inner diameter of the casing of Well A is Φ161mm, the casing pressure is 15MPa, the insulation pipe specification is Φ114mm, the well depth is 1000m, the nitrogen starting temperature is 50℃, the standard pressure is 0.101KPa, and the standard casing temperature is 273K.

[0025] (1) Casing volume

[0026]

[0027] (2) Annular volume

[0028]

[0029] (3) Nitrogen volume V under standard casing conditions 标套

[0030]

[0031] 15×20 / (50+273)=0.101×V 标套 / 273

[0032] V 标套=2510.5 standard square meters

[0033] The insulation string is lowered into the designed position and pressurized by a cement truck on the ground. When the pressure reaches the opening pressure of the pressure regulating valve, the thermal recovery packer is set and the annulus is sealed by the packer.

[0034] While steam is being injected into the well, nitrogen is simultaneously injected into the annulus at a rate of 800-1200 Nm3 / hour. The calculated volume of nitrogen required to be injected into the annulus is 2510.5 Nm3. To ensure that all air and water in the annulus are expelled through the check valve and that the annulus is filled with high-purity nitrogen, 3000 Nm3 of nitrogen is injected. After nitrogen injection is stopped, the check valve is closed, and steam injection into the tubing continues until the designed steam volume is reached, completing the entire steam injection process.

[0035] 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 packer and nitrogen composite insulation string suitable for heavy oil thermal recovery, characterized in that: It includes a constant pressure valve, a thermal recovery packer, a check valve, a compensator, and an insulated oil pipe. The insulated oil pipe is installed in the oil well. The compensator and the check valve are installed on the insulated oil pipe from top to bottom. A constant pressure valve is installed at the bottom of the insulated oil pipe. A thermal recovery packer is installed at the lower outer end of the check valve. The outer side of the oil well facing the lower end of the insulated oil pipe is the oil layer.

2. The packer and nitrogen composite insulation string suitable for heavy oil thermal recovery according to claim 1, characterized in that: The specification of the heat-insulated oil pipe is Φ114mm.

3. The packer and nitrogen composite insulation string suitable for heavy oil thermal recovery according to claim 1, characterized in that: The inner diameter of the oil well is Φ161 mm.

4. The packer and nitrogen composite insulation string suitable for heavy oil thermal recovery according to claim 1, characterized in that: The pressure between the oil well and the insulated oil pipe is 15 MPa.

5. The packer and nitrogen composite insulation string suitable for heavy oil thermal recovery according to claim 1, characterized in that: The pressure between the oil well and the insulation pipe is 273K.

6. A process for implementing a packer and nitrogen composite insulation string suitable for heavy oil thermal recovery, characterized in that: The steps are as follows: lower the insulated tubing string into the designed position, pressurize it with a ground cement truck, inject steam into the oil well, and when the pressure reaches the opening pressure of the constant pressure valve, the thermal recovery packer is set and the annulus is sealed by the packer.

7. The process for implementing the packer and nitrogen composite insulation string for heavy oil thermal recovery according to claim 6, characterized in that: When steam is injected into the oil well, nitrogen is injected into the casing annulus simultaneously.

8. The process for implementing the packer and nitrogen composite insulation string for heavy oil thermal recovery according to claim 7, characterized in that: The displacement of the nitrogen injected into the oil casing annulus is 800-1200 standard cubic meters per hour.

9. The process for implementing the packer and nitrogen composite insulation string for heavy oil thermal recovery according to claim 7, characterized in that: The amount of nitrogen injected into the casing annulus is calculated based on the volume of the casing annulus, and the amount of nitrogen injected is 20%-30% of the volume of the casing annulus.

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