Oil and natural gas exploration and development can be divided into land exploitation and offshore exploitation. The oil and natural gas contained in the earth's crust roughly accounts for 60% of the land and 40% of the offshore oil.
Before the industrialization and large-scale application of titanium alloys, the shells of commonly used logging tools were made of 45 steel, 40Cr steel, and 30 MoVNb steel, but none of them could meet the needs of modern logging technology. Modern high-tech oil and gas exploration And the development requires that the metal casing of the logging tool can withstand pressures> 98 MPa, and it must also be resistant to corrosion by underground crude oil and various media. In addition, it must have a low absorption rate of natural gamma rays during logging. In magnetic logging , It should not have a shielding effect on the earth's magnetic field. From these performance requirements, titanium alloy is a good material for the casing of logging tools.
In the mid-1980s, the China Petroleum Administration introduced 6 sets of integrated logging tools with Ti-6Al-4V titanium alloy shells from Schlumberger of France and Dresser of the United States. However, the shells of domestic logging tools made of titanium alloy were not available at that time. Ti﹣6Al﹣4V is a kind of alloy with good comprehensive performance, mature and good price, since then, Baoji Nonferrous Metal Processing Plant has done detailed research on all aspects of this alloy extruded pipe.
The working conditions of the logging tool are very harsh, and the shell material is required to have high corrosion resistance. Studies have shown that Ti-6Al-4V alloy has strong corrosion resistance in crude oil media and in sulfide and chloride-containing media. The corrosion rate is less than 0.017 mm/a. Therefore, the casing of the logging tool made of Ti-6Al-4V alloy can avoid the reduction of the critical damage pressure caused by the thinning of the casing due to corrosion for a long time.
In petroleum exploration and development logging, some magnetic physical quantities must be measured. The magnetic susceptibility of the casing of the logging tool will also affect logging. If the magnetic susceptibility is too large, the casing will have a shielding effect and affect the normality of the magnetic measuring instrument. So the magnetic susceptibility of the metal casing is required to be as small as possible. Therefore, titanium alloy is the best material for manufacturing the casing of magnetic logging tool. The magnetic susceptibility of Ti﹣6Al﹣4V alloy is X=3.2×10﹣6 cm3/g, which is a non-ferromagnetic material. At the same time, titanium alloy is also good in processing and forming performance.