Offshore downhole elastic casing centralizer

Abstract

Disclosed in the present utility model is an offshore downhole elastic casing centralizer, comprising a circular first end ring. A plurality of branch rib plates are evenly distributed at the bottom o

Description

Elastic casing centralizer for offshore wells

[0001] This application claims priority to a patent application filed with the State Intellectual Property Office of China on March 26, 2024, with application number 202420603398.7 and invention name “Elastic Casing Centralizer for Offshore Wells”. Technical Field

[0002] The utility model belongs to the technical field of petroleum drilling and cementing equipment, in particular to an elastic casing centralizer in an offshore well. Background Art

[0003] The centering of the casing in the wellbore is one of the key factors determining the quality of cementing in oil and gas wells, and the placement of the centralizer is fundamental to this. The centralizer's function is to ensure the casing is properly centered in the wellbore, ensuring a strong cement bond between the casing and the wellbore wall, and guaranteeing high-quality cementing.

[0004] In daily drilling and production, there is a downhole expansion condition in offshore wells. In this well condition, there is a narrow wellbore in the middle that is close to the size of the casing, and large-sized open holes at both ends.

[0005] Existing centralizers are unable to pass through such extremely narrow working conditions, or require a significant operating force to do so. However, excessive operating force can cause permanent deformation of the working branch ribs, resulting in insufficient restoring force (support) for the elastic casing centralizer. Such centralizers can lead to difficulties in lowering the casing, slowing lowering speeds, and insufficient centering of the casing in the wellbore during cementing, thus reducing cementing quality and potentially causing cementing failure or oil and gas cross-linking.

[0006] Utility Model Content

[0007] The utility model aims to provide an elastic casing centralizer for offshore wells, which solves the problem in the prior art that the centralizer cannot pass through extremely narrow working conditions or requires a large operating force to pass through.

[0008] The technical solution adopted by the utility model is that the elastic casing centralizer for offshore wells includes a circular first end ring, a plurality of branch ribs are evenly distributed on the bottom end of the first end ring, a second end ring is fixedly connected to one end of the branch rib away from the first end ring, a plurality of stress relief grooves are opened on the surface of the branch rib, and a longitudinal straight line or jujube-shaped weakening groove is opened in the middle of the surface of the branch rib.

[0009] The utility model is also characterized in that:

[0010] The shape of the stress relief groove is arc-shaped;

[0011] The stress relief grooves are arranged in a herringbone pattern on the surface of the branch ribs, and the distance between the stress relief grooves and the edge of the branch ribs on the same side is 10mm to 20mm;

[0012] The radius of the stress relief groove ranges from 20mm to 80mm, the length of the stress relief groove ranges from 20mm to 100mm, and the width ranges from 1mm to 5mm.

[0013] Several stress relief grooves are also provided at the connection between the branch ribs and the first and second end rings, and the upper and lower connection points are symmetrically distributed.

[0014] The length of the weakening groove is 100mm to 300mm, the width is 1mm to 10mm when it is straight, and the distance from the edge of the branch reinforcement plate on the same side is 10mm to 30mm when it is jujube-shaped.

[0015] The beneficial effects of the utility model are:

[0016] 1) The utility model provides an elastic casing centralizer for offshore wells with stress relief grooves on the outer surface of the branch ribs. The size and number of the stress relief grooves can be adjusted according to actual needs. When the branch ribs are subjected to excessive pressure, the stress relief grooves provide stress deformation space for the elastic material of the main body, thereby preventing damage or partial damage to the structural structure of the main body elastic material. This also prevents the elastic centralizer from attenuating its restoring force after being subjected to large loads, thereby maintaining the design performance of the elastic centralizer.

[0017] 2) The centralizer of the utility model has a weakening groove in the center of the outer surface of the branch rib, and limits the shape and size range of the weakening groove, which is adjusted according to actual working conditions. During the compression process of the branch rib, the force increases linearly at the beginning, which does not affect the reset force in a large wellbore; however, when it is about to be flattened, the force becomes significantly smaller, so the operating force in a narrow wellbore is relatively small; after passing through the narrow hole, the outer diameter of the product is reduced very little, so good elasticity can be guaranteed even after passing through the narrow hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a schematic structural diagram of an elastic casing centralizer for an offshore well according to the present invention when the weakening groove is in a longitudinal straight line shape;

[0019] FIG2 is a schematic structural diagram of the utility model when the weakening groove in the centralizer is in the shape of a jujube pit.

[0020] In the figure, 1. first end ring, 2. branch rib plate, 3. second end ring, 4. stress relief groove, 5. weakening groove. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0022] Example 1

[0023] As shown in Figures 1 and 2, this embodiment provides an elastic casing centralizer for an offshore well, including a circular first end ring 1, and a plurality of branch ribs 2 are evenly distributed at the bottom end of the first end ring 1. The branch ribs 2 are made of high-strength metal and are sturdy and durable.

[0024] The branch rib 2 is fixedly connected to the second end ring 3 at one end away from the first end ring 1. The first end ring 1 and the second end ring 3 help to connect with the sleeve. A plurality of stress relief grooves 4 are opened on the surface of the branch rib 2. The shape of the stress relief grooves 4 is arc-shaped. The stress relief grooves 4 are arranged in a herringbone pattern on the surface of the branch rib 2. The horizontal distance between the stress relief grooves 4 and the edge of the branch rib 2 on the same side is 10mm to 20mm.

[0025] The stress relief groove 4 extends along an arc trajectory. The radius of the arc where the stress relief groove 4 is located is in the range of 20mm to 80mm. The length of the arc where the stress relief groove 4 is located is 20mm to 100mm; the width is 1mm to 5mm. Several stress relief grooves 4 are also provided at the connection between the branch rib plate 2 and the first end ring 1 and the second end ring 3. The branch rib plate 2 is connected to the first end ring 1 through an upper connection part, and the branch rib plate 2 is connected to the second end ring 3 through a lower connection part. The upper connection part and the lower connection part are respectively provided with several stress relief grooves 4, and the upper connection part and the lower connection part are symmetrically distributed. The stress relief groove 4 provides stress deformation space for the main elastic material when the branch rib plate 2 is subjected to excessive pressure, thereby preventing the main elastic material from being damaged or partially damaged.

[0026] A longitudinal linear or jujube-shaped weakening groove 5 is provided in the middle of the surface of the branch rib plate 2. The length of the weakening groove 5 is 100mm to 300mm, the width is 1mm to 10mm when linear, and the horizontal distance from the edge of the branch rib plate 2 on the same side is 10mm to 30mm when jujube-shaped. A weakening groove 5 is provided in the center of the outer surface of the branch rib plate 2, and the shape and size range of the weakening groove 5 are limited and adjusted according to the actual working conditions. During the compression process of the branch rib plate 2, the force increases linearly at the beginning, which does not affect the reset force in the large wellbore; however, when it is about to be flattened, the force becomes significantly smaller, so the operating force in the narrow wellbore is relatively small; after passing through the narrow wellbore, the outer diameter of the product is reduced very little, so good elasticity can be guaranteed even after passing through the narrow wellbore.

[0027] The working process of this utility model is as follows:

[0028] When the casing is lowered into the well, it may come into contact with the wellbore wall, causing wear and seizure. Therefore, the centralizer body is mounted on the casing via a first end ring 1 and a second end ring 3. During the cementing process, as the casing is lowered, the centralizer moves with it. When the casing encounters borehole narrowing or formation changes, the stress relief grooves 4 and weakening grooves 5 on the surface of the branch ribs 2 prevent damage to the elastic material structure of the body or partial damage. They also prevent the elastic centralizer from attenuating its restoring force after heavy loads.

[0029] Example 2

[0030] As shown in Figure 1, this embodiment provides an elastic casing centralizer for offshore wells. The central portion of the first end ring 1 is evenly distributed with several branch ribs 2. A second end ring 3 is fixedly connected to the end of each branch rib 2 facing away from the first end ring 1. Several stress relief grooves 4 are formed on the surface of each branch rib 2, and a longitudinal linear weakening groove 5 is formed in the middle of each branch rib 2. The stress relief grooves 4 are arc-shaped and arranged in a herringbone pattern on the surface of the branch rib 2. The horizontal distance between the stress relief grooves 4 and the edge of the branch rib 2 on the same side is 10 mm. The radius of the arc containing the stress relief grooves 4 is 20 mm, and the length and width of the arc are 20 mm. Several stress relief grooves 4 are also formed at the junctions between the branch rib 2 and the first and second end rings 1 and 3, with the upper and lower junctions symmetrically arranged. The weakening grooves 5 are 180 mm long, and the linear weakening grooves 5 are 3 mm wide.

[0031] Example 3

[0032] As shown in Figure 2, this embodiment provides an elastic casing centralizer for offshore wells. The difference from Example 2 is that the weakening groove 5 is in the shape of a jujube pit, the length of the weakening groove 5 is 180 mm, and the distance between the jujube pit-shaped weakening groove 5 and the edge of the branch rib 2 on the same side is 20 mm.

[0033] The utility model of elastic casing centralizer for offshore wells has been used to compare the test data of two groups of centralizers with different sizes. The comparative data are shown in Table 1 and Table 2:

[0034] Table 1

[0035] Table 2

[0036] Comparing the test data above, we found that products with weakening grooves significantly reduced operating force through narrow wellbores, by approximately 38% to 55%, while increasing the restoring force. This means that in actual operating conditions, centralizers with reduced operating force and increased restoring force should experience virtually no deformation when traversing narrow wellbores.

Claims

1. Offshore elastic casing centralizer, characterized by: The invention comprises a circular first end ring (1), a plurality of branch ribs (2) are evenly distributed on the bottom end of the first end ring (1), a second end ring (3) is fixedly connected to one end of the branch rib (2) away from the first end ring (1), a plurality of stress relief grooves (4) are provided on the surface of the branch rib (2), and a longitudinal straight line or jujube-shaped weakening groove (5) is provided in the middle of the surface of the branch rib (2).

2. The elastic casing centralizer for offshore wells according to claim 1, characterized in that: The stress relief groove (4) is in the shape of a circular arc.

3. The elastic casing centralizer for offshore wells according to claim 1, characterized in that: The plurality of stress relief grooves (4) on each branch rib plate (2) are arranged in two rows, and the two stress relief grooves (4) arranged in parallel are arranged in a herringbone shape.

4. The elastic casing centralizer for offshore wells according to claim 1, characterized in that: The stress relief grooves (4) are arranged in a herringbone pattern on the surface of the branch rib plate (2), and the distance between the stress relief grooves (4) and the edge of the branch rib plate (2) on the same side is 10 mm to 20 mm.

5. The elastic casing centralizer for offshore wells according to claim 1, characterized in that: The stress relief groove (4) extends along an arc track, the radius of the arc where the stress relief groove (4) is located ranges from 20 mm to 80 mm, the length of the stress relief groove (4) ranges from 20 mm to 100 mm, and the width ranges from 1 mm to 5 mm.

6. The offshore downhole elastic casing centralizer according to claim 1, characterized in that: A plurality of stress relief grooves (4) are also provided at the connection between the branch rib plate (2) and the first end ring (1) and the second end ring (3), and the upper connection and the lower connection are symmetrically arranged.

7. The elastic casing centralizer for offshore wells according to claim 1, characterized in that: The branch rib plate (2) is connected to the first end ring (1) via an upper connecting portion, and the branch rib plate (2) is connected to the second end ring (3) via a lower connecting portion. The upper connecting portion is provided with a plurality of stress relief grooves (4), and the lower connecting portion is provided with a plurality of stress relief grooves (4). The plurality of stress relief grooves (4) in the upper connecting portion and the plurality of stress relief grooves (4) in the lower connecting portion are symmetrically arranged.

8. The offshore downhole elastic casing centralizer according to claim 1, characterized in that: The length of the weakening groove (5) is 100mm to 300mm, the width is 1mm to 10mm when it is in a straight line shape, and the distance from the edge of the same-side branch rib plate (2) is 10mm to 30mm when it is in a jujube-shaped shape.

9. The elastic casing centralizer for offshore wells according to claim 1, characterized in that: Each of the branch ribs (2) comprises a first plate body, a second plate body and a third plate body connected in sequence, wherein the first plate body is connected to the first end ring (1), and the third plate body is connected to the second end ring (3); a plurality of stress relief grooves (4) are respectively arranged on the first plate body and the third plate body, and the weakening groove (5) is arranged on the second plate body.

10. The elastic casing centralizer for offshore wells according to claim 9, characterized in that: From the middle of the branch rib plate (2) to the first end ring (1), the width of the first plate body gradually increases; From the middle of the branch rib plate (2) to the second end ring (3), the width of the third plate body gradually increases.

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