Deviations from a straight line in a planned wellbore path are commonly referred to as the well’s tortuosity. Such deviations have historically been difficult to assess and quantify based on the limitations of technology to provide a true understanding of the downhole environment. Large changes in trajectory in a wellbore’s path over a short distance—that is, high tortuosity in the wellbore—create a variety of problems, including issues with running casing, tool damage, and production equipment failure. Existing solutions largely rely on calculating doglegs in the wellbore to understand where there are areas of tortuosity, but such solutions are lacking in data precision and granularity, as stationary surveys are only measured at 100-ft intervals. This, combined with relatively little evolution in this field of study over the past several decades, have made explaining the difficulties of running and operating equipment in deviated, highly tortuous wells a hit-or-miss endeavor.
MicroGuide™, a patented process developed by Gyrodata, is a high-density wellbore logging technology that generates high-resolution 1-ft survey data, enabling more accurate calculation of a well’s tortuosity. The survey data is obtained from a number of survey stations on the wellbore log via gyroscopic tools, MWD magnetic survey instruments, or a combination of both. As the data is processed, the system calculates the wellbore path, dogleg, tortuosity, effective diameter, and uniform bend. The resulting 3D diagram allows an operator to visualize the wellbore’s trajectory and all the microdoglegs along that path, helping them identify issues in the hole before running casing and make more informed decisions on where to place artificial lift equipment. Previous technologies that relied solely on dogleg severity calculations often involved so many assumptions and so much guesswork that they led to placement decisions that resulted in more unpredicted failures.
A primary application of MicroGuide is in improving the placement of electrical submersible pumps, or ESPs. Typically, ESPs are placed in areas of low dogleg severity as indicated in conventional MWD surveys, but such surveys do not capture detailed, high-resolution tortuosity, nor do they allow the estimation of the effective diameter, among other well-related measurements. As a result, ESPs have been wrongfully placed in areas of high tortuosity not identified by MWD surveys, leading to equipment damage and failure, nonproductive time, and production losses in the well. Using the MicroGuide service can not only mitigate the risk of lost production but potentially help to increase production. The system also eliminates damage to the ESPs that could have necessitated costly workover operations and early equipment replacements.
In one case history, an operator decided to place a 126-foot-long ESP in a well using dogleg severity values derived from standard MWD surveys at a depth of 7,760 to 7,886 ft. The pump failed after only 5 days of operation with a broken shaft, which had most likely been caused by excessive bending. To get a better picture of the wellbore shape, the operator decided to run a high-density gyroscopic survey and conduct a tortuosity analysis with MicroGuide wellbore logs. The tortuosity of the wellbore where the first ESP was set showed an effective diameter smaller than the pump and a uniform bend exceeding 2°/100 ft, with the system identifying a new location at 7,610 to 7,736 ft that had a sufficient effective diameter and a uniform bend of 1.637°/100 ft. The ESP placed here ran for 10 months before being replaced by a beam pump due to production declines in the well.