Precise magnetic positioning technology for buried wellheads in underground gas storages

In construction of underground gas storage facilities, it is essential to ensure the sealing performance of the gas storages. When determining the location of abandoned and buried old wells for sealing, there exist certain errors and uncertainties with the common surveying methods. A precise magnetic positioning technology for buried wellheads was proposed. In conjunction with back-scattering signal survey technology, precise survey and positioning of buried wellheads can be achieved by actively exciting the magnetic field distribution characteristics around the buried wellheads. The system mainly consists of launcher, receiver and computing unit. By using positioning algorithms such as signal extraction, coordinate transformation, plane positioning and vertical positioning, the buried wellheads position can be determined. Meanwhile, potential interferences on magnetic positioning effect by winches, circuits and transmitters, etc. were analyzed. This technology was applied in the positioning operation of Well Qiaoxia S in national natural reserve in Liaohe Oilfield, where a total of four wells were drilled. After alternately surveying twice, the wellhead position of Well S was successfully locked, followed by successful excavation with an error less than 0.5 meters compared to the surveyed coordinates. The magnetic positioning technology solves the problem that has long plagued oil fields in the smooth construction of gas storages, and provides a reliable solution for the precise positioning of buried wellheads, which is of guiding significance.