Top ten well completion tools

The types of downhole tools commonly used in offshore oil field completion and production strings include: Packer, SSSV, Sliding Sleev , (Nipple), Side Pocket Mandrel, Seating Nipple, Flow Coupling, Blast joint, Test Valve, Drain Valve, Mandrel, Plug, etc.

1.Packers

The packer is one of the most important downhole tools in the production string, and its main functions are as follows:

Separate production layers to prevent collusion and interference of fluid and pressure between layers;

Separation of killing fluid and production fluid;

Meet various requirements of oil (gas) production and workover operations;

Retain the packer fluid in the casing annulus to protect the casing and ensure safe production.

The packers used in offshore oil (gas) field completions can be divided into two types: retrievable and permanent, and according to the setting method, they can be divided into hydraulic setting, mechanical setting and cable setting. Packers can be divided into many types, and a reasonable selection should be made according to actual production needs. The most important parts of the packer are slips and rubber, and some packers do not have slips (packers for open wells). There are many types of packers, the main function of which is the support between the slips and the casing and the sealing between the slips and the casing to seal a certain position.

2.Downhole safety valve

The downhole safety valve is a control device for the abnormal flow of fluid in the well, such as fire on the offshore oil production platform, pipeline rupture, blowout, out of control of the oil well caused by the earthquake, etc., so that the downhole safety valve can be automatically closed to realize the flow control of the fluid in the well.

1) Classification of safety valves:

• Steel wire retrievable safety valve
• Oil pipe portable safety valve
• Casing annulus safety valve The most commonly used safety valve is the tubing portable safety valve

2) Principle of action

Pressurized through the ground, the hydraulic oil is transmitted to the pressure transmission hole to the piston through the pressure hydraulic control pipeline, pushing the piston down and compressing the spring, and the flap valve is opened. If the hydraulic control pressure is maintained, the safety valve is in the open state; release The pressure of the hydraulic control line is pushed upward by the spring tension to move the piston upward, and the valve plate is in a closed state.

3.Sliding sleeve

1) The sliding sleeve can close or connect the connection between the production string and the annular space through the cooperation between the inner and outer sleeves. Its main functions are as follows:

• Inducing blowout after well completion;
• Circulation kill;
• Gas lift
• Sitting jet pump
• Multi-layer wells can be used for separate production, layered testing, layered injection, etc.;
• Multi-layer mixed mining;
• Run the plug into the well to shut down the well or to test the pressure of the tubing;
• Circulating chemical agent anticorrosion, etc.

2) Working principle

The sliding sleeve closes or connects the passage between the oil pipe and the annular space by moving the inner sleeve. When the channel of the inner sleeve is facing the passage of the sliding sleeve body, the slideway is in an open state. When the two are staggered, the sliding sleeve is closed. There is a working cylinder on the upper part of the sliding sleeve, which is used to fix the downhole flow control device related to the sliding sleeve. There is a sealing end surface on the upper and lower sides of the inner sleeve, which can cooperate with the sealing packing of the downhole device for sealing. Connect the sliding sleeve switch tool under the basic tool string, and carry out steel wire operation. The sliding sleeve can be switched on and off. Some of them need to shock downward to move the sleeve down to open the sliding sleeve, while others need to shock upward to make the inner The sleeve moves up to open the sliding sleeve.

4.Nipple

1) Classification and use of working Nipple

Classification of Nipples:

(1) According to the positioning method: there are three types: selictivity, Top NO-GO and Bottom NO-GO, as shown in Figures a, b, and c.

Some mandrels can have both optional type and top stop (as shown in Figure b). The so-called optional type means that the inner diameter of the mandrel has no diameter reduction part, and the same size of the sitting tool can pass through it, so multiple mandrels of the same size can be lowered into the same pipe string, and the top stop means that the inner diameter of the sealed mandrel is The top of the stopper with a moving step at the reduced diameter part acts on the top, while the reduced diameter part of the bottom stopper is at the bottom, the sealing section of the plug cannot pass through, and the stopper at the bottom is generally installed at the bottom of the same pipe string. As an instrument hanger and to prevent wire tool strings from falling into the bottom of the well.

(2) According to the working pressure: there are normal pressure and high pressure, the former is used for conventional wells, and the latter is used for high pressure oil and gas wells.

Application of Nipples:

• Sit into the jammer.
• Sit in the underground to automatically control the safety valve.
• Sit into the check valve.

Run in a relief tool (choke nozzle) to reduce wellhead pressure.

•  Cooperate with Polished Nipple , install separation sleeve or pup joint, repair damaged oil pipe or thickened pipe near oil layer.
• Sit and hang downhole measuring instruments.
• It can prevent the tool string from falling into the bottom of the well during wireline operation.

5. Side Pocket Mandrel

1) Functional structure

The Side Pocket Mandrel is one of the important downhole tools for well completion. It is combined with various gas lift valves to realize different gas lift methods, run water nozzles of different sizes, and realize layered injection. Its structure is shown in the figure , consists of two parts, the base pipe and the eccentric cylinder, the size of the base pipe is the same as that of the oil pipe, the upper part has a positioning sleeve, and the eccentric cylinder has a tool identification head, a locking groove, a sealing cylinder and an external communication hole.

2) Features of  Side Pocket Mandrel:

Positioning: Make all kinds of downhole tools eccentric and accurately orientate into the eccentric barrel.

Recognizability: Downhole tools of the correct size are run eccentrically into the eccentric barrel, while other tools of larger size pass through the base pipe.

Greater test pressure is allowed.

2) The function of  Side Pocket Mandrel: gas lift, chemical agent injection, water injection, circulation killing, etc.

6. Plug

When there is no downhole safety valve or the safety valve fails, the steel wire works, and a plug of corresponding size is lowered into the working cylinder to close the well. Pressure testing of tubing and setting of hydraulic packers during well completion or workover operations.

7. Gas lift valve

The gas lift valve is lowered into the eccentric working cylinder, which can realize different gas lift production methods, such as continuous gas lift or intermittent gas lift.

8.Flow couping

The flow couping is actually a thickened pipe, whose inner diameter is the same as that of the oil pipe, but the outer diameter is slightly larger, and is usually used for the upper and lower ends of the safety valve. For high-yield oil and gas wells, oil wells with general output can choose to use or not. When high-yield oil gas flows through the safety valve, it will cause throttling due to diameter reduction, resulting in eddy current erosion and wear at its upper and lower ends.

9.Oil Drain valve

The oil drain valve is generally installed at 1-2 oil pipes above the check valve. It is the discharge port of the fluid in the oil pipe when the pump inspection operation is lifted up, so as to reduce the load of the workover rig and prevent the well fluid from polluting the platform deck and the environment. There are currently two types of oil drain valves: rod-throwing drain and ball-throwing hydraulic drain. The former is more suitable for thin oil and heavy oil wells with high water cut; the latter is used for heavy oil wells with low water cut and has a high success rate.

10.Pipe scraper

1) Purpose: It is used to remove cement block, cement sheath, hard wax, various salt crystals or deposits, perforation burrs and iron oxide and other dirt remaining on the inner wall of casing, and to Unimpeded access to various downhole tools. Especially when the annular space between the downhole tool and the inner diameter of the casing is small, the next step of construction should be carried out after sufficient scraping.

2) Structure: It is composed of body, knife plate, fixed block, pressing block and other parts.

3) Working principle: before entering the well, the maximum installation size of the large piece of the scraper is larger than the inner diameter of the casing. After entering the well, the blade is forced to press down the spring, and the spring provides radial feed force. When scraping hard materials, it takes several scrapes to scrape to the inner diameter of the casing. The scraper is connected to the lower end of the downhole pipe string, and the up and down movement of the pipe string is the axial feed during the hanging down process.

It can be seen from the structure of the blade that each spiral blade has two arc-shaped cutting edges inside and outside. Grinding effect. The strip-shaped blades are evenly distributed on the surface of the scraper according to the left helical line, which is beneficial to the upper return mud to take away the scraped debris.