The performance of oil well pipes includes anti-galling performance, anti-collapse performance, anti-corrosion performance, and perforation performance.
(1) Anti-galling performance: According to the standard requirements, the threaded joints of oil and casing need to be tested for make-up and make-down. It is stipulated that each joint must be made up and made down 6 times each. Makeup to the maximum torque recommended by the manufacturer, then remove and check the galling of the internal and external threads of the oil and casing. The galling of oil and casing threads is related to factors such as thread quality, thread surface hardness, make-up speed, surface friction coefficient, and contact stress (coupling torque). To improve the anti-galling performance of oil and casing threads, the finish of the thread, the hardness and uniformity of the thread should be improved, and the make-up speed and the tightening torque should be reduced. At the same time, a softer metal or non-metal film layer should be plated on the surface of the inner thread of the coupling to separate the pipe body of the oil and casing and the coupling to prevent the metal surface between the two threads from adhering to each other and avoid tearing or even tearing of the thread. Before the coupling is screwed on, the thread surface needs to be coated with thread grease to prevent the thread from sticking after the coupling is screwed on and to improve the sealing performance of the thread.
There are many coating methods for the surface of the coupling thread: such as galvanizing and phosphating; for some special materials and special connection threads, copper plating is often required. Factors related to sticking in the factory: thread parameters (pitch, tooth height, taper, tight moment, tooth profile half angle, etc.), matching of internal and external threads (surface treatment, surface finish, phosphating, galvanizing, copper plating, etc.), thread grease (function: lubrication, filling and sealing, etc., composed of metal powder and grease), make-up control (make-up torque, make-up speed, etc.), material factors, etc.
Factors related to oilfield use and operation: lifting without wire guard, skewed buckle (the pipe swings in the air and is not concentric with the well buckle), no buckle and less buckle, thread grease (not meeting standard requirements, sand, and other debris), make-up speed and make-up torque, and clamping force of large tongs, etc.
(2) Anti-squeeze (crush) performance: As the drilling depth increases, the pressure on the oil and casing in the oil and gas wells increases, especially in deep wells, ultra-deep wells, or oil and gas wells in complex formations such as rock salt, salt paste, shale, and soft rock formations that need to isolate plastic flow. When the external pressure exceeds a certain limit, the oil well pipe body will produce groove-shaped or elliptical deformation, which is called oil well pipe collapse.
(3) Anti-corrosion performance: Some oil and gas fields contain a large amount of corrosive media such as hydrogen sulfide, carbon dioxide, or chloride ions, which puts forward corrosion resistance requirements for oil and casing, including resistance to sulfide stress corrosion, resistance to CO2 and Cl- corrosion, etc. The corrosion resistance of oil and casing is mainly related to factors such as the chemical composition of steel and the residual stress value of steel pipes. Reducing the content of non-metallic inclusions and harmful elements in steel, increasing anti-corrosion elements such as Cr and Ni, reducing the residual stress in steel pipes, and improving the yield strength ratio of steel pipes are all conducive to improving the corrosion resistance of oil and casing.
(4) Perforation performance: The oil production part of the oil layer casing (layered oil production in a multi-layer oil well) needs to be perforated to allow crude oil to flow into the casing from the designated oil-bearing oil sand layer. For this reason, the oil layer casing is required to have good perforation performance, especially when using gunless perforation operations, the perforation performance of the casing is required to be higher. The perforation performance of the casing is obtained through perforation tests. That is, the test casing is hung in a simulated well, and a certain number of shaped perforators with a certain distance and different directions are hung in the casing. Then perforation is carried out. After perforation, if there are no cracks around each hole of the test casing, the perforation performance is evaluated as good; if there are a small number of small cracks around each hole, but their number and length do not exceed the requirements of the technical conditions, then the perforation performance is evaluated as qualified; and if the number or length of cracks around each hole exceeds the requirements, especially if the cracks between two adjacent holes are connected, the perforation performance is evaluated as unqualified. The oil field also has clear requirements on the amount of outward expansion of the casing after perforation and the height of the internal and external burrs around the hole.
Post time: Jan-17-2025