Ranging Technology Manages Well-Collision Risk Without Affecting Rig Time

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 220770, “Managing Well-Collision Risk by Disruptive Ranging Technology Without Impacting Rig Time,” by Mahmoud ElGizawy, SPE, and Rustam Rakhmangulov, SPE, SLB, and William T. Allen, SPE, BP, et al. The paper has not been peer reviewed. _ Drilling a surface section from an offshore platform or a multiwell pad increases the risk of well collision. Managing well collision is currently performed by taking stationary surveys and projecting ahead of the bit to calculate the minimum allowable separation distance from the offset well. This approach, however, does not possess any means of confirming the distance and direction of the offset well. The complete paper presents a continuous passive magnetic ranging technique that can provide real-time distance and direction to the offset well while drilling without interrupting the drilling operation. Introduction The deployment of the ranging technique using definitive dynamic surveys (DDS) took place in Thunder Horse field, the largest offshore field in the Gulf of Mexico. The well was drilled in Thunder Horse North, where the subject Well A path came closer to two offset wells (Well B and Well C). Offset Well B’s center-to-center separation was closer to the subject Well A in the 26-in. section. The section interval is 4,068 ft (between 5,982 and 10,050 ft), where the equivalent center-to-center distance from offset Well B is closer to the subject well for more than one-third of the section, thus presenting a well-collision risk. DDS, in comparison with legacy stationary surveys to execute passive magnetic ranging (PMR), eliminate the added operational rig cost of taking static surveys that also could add drilling risk to operations. Adding to the complexity of the section, the bottomhole assembly already had a main measurement-while-drilling (MWD) service provider that was incompatible with the DDS MWD platform to demodulate on the same carrier. This complexity was overcome, however, by the ability of the DDS MWD platform to demodulate at higher frequencies. The technique permits dual-provider MWD survey services because of its independent telemetry frequency that does not affect the objectives of the section. Methodology PMR is a method of determining the relative distance and direction between the drilled well and a cased offset well. It uses magnetometer measurements within any traditional MWD or enhanced-measurement-system tool to detect external magnetic interference from the offset well casing. This method was first developed in the 1970s for a relief well drilling application. MWD technology featuring DDS was used in this case study. The ability of the MWD tool to take continuous six-axis dynamic surveys is not the only requirement for a successful real-time PMR job. Additionally, the tool should be able to provide sufficient surveying data density, an acceptable signal/noise ratio, and advanced ranging processing to interpret data in real time.