generally include: magnetic positioning pup joints and casing pup joints
Magnetic positioning pup joints: A short casing used to accurately determine the depth of oil and gas layers when perforating. The casing is usually connected to the top 30m above the oil (gas) layer. No magnetic treatment.
Casing pup joint: A short casing that is smaller than the standard length casing. The top casing is connected to the last casing when it is used to adjust the position of the top surface of the casing string and connect the short casing to the cement head. (This is to adjust the length of the casing for drilling, to meet the depth of the casing to meet the cementing needs)
The tubing stub is actually a short tubing whose length is shorter than the tubing length range R1 in the API 5CT standard. Except that the length is different from the tubing, the other dimensions and requirements are the same as those of the tubing.
Magnetic positioning depth technology, using the composite perforation depth technology of natural gamma (GR) and magnetic positioning (CCL) oil jackets, to synthesize the single-well testing depth curve, integrated logging curve and casing short section curve assessment. Through calculation, using this technology can not only avoid the disadvantages of high error of single magnetic positioning depth, but also the accuracy of perforation depth can be increased to 99.98%.
Before the perforation and other measures, insert a magnetic probe. On the test curve, the casing collar can have a jump point on the curve, that is, the position of different casing collars can be found. Because the special casing is shorter, the two points of change that are close to each other are reflected in the depth of the short casing. Looking down from this point to find the required depth can reduce the error.