Well Planning Based On Passive Magnetic Ranging And Magnetized Casing

Abstract

Abstract No one wants or expects to have to drill a relief well; however, it is a fact that a number of relief wells are required each year. Recent events have drawn attention to the need for, and the benefit of, comprehensive contingency relief well planning. On a deepwater Gulf of Mexico (GOM) well, it was noted that "Active Electro Magnetic Ranging" technology would not work at the planned intercept depth due to the presence of a large salt body. Furthermore, the planned survey program would result in a relatively large Ellipse of Uncertainty (EOU) at the desired intercept depth, which would make a relief well intercept on a first pass unlikely to succeed. A combination of "Passive Magnetic Ranging" and a modified survey program was identified as the solution to demonstrate the ability to intercept the target well on the first attempt. Due to the inherent problems associated with "active" ranging technologies in salts (De Lange, J.I., Darling, Toby J., 1990), "passive" MWD Ranging was identified as the likely ranging technique due to the fact that it is not impacted by formation type (salt). Based upon the modified survey program, it was determined that a reliable range of detection of eighty feet (80’) would be required to qualify passive magnetic MWD Ranging technology as the primary ranging technique should a relief well be required. This detection range would allow a "no flyby" intercept (also referred to as a direct intercept) by the theoretical relief well. To confirm this capability, a qualifying demonstration protocol was established and executed using casing joints that would ultimately be run into the well. The proving tests were conducted first with only remnant magnetization of the casing joints and then again after the casing joints had been magnetized with a coil.