Accurate Wellbore Placement with Rotating Continuous Surveys while Saving Time and Cost in Non-Conventional Shale Play

Drilling Departments aim to drill wells faster, with improved hole quality, and in a safe manner. Wellbore surveying is an important aspect of delivering wells safely. More specifically wellbore surveying should allow: To drill wells without colliding into other wells.To measure a wellbores position accurately enough, that in case of a blowout, a relief well can be drilled quickly and intercept the blowing well at the desired depth, where the accuracy (i.e. positional uncertainty) is transferable between different operators and different service companies.To perform the surveying and anti-collision (AC) calculations in a straightforward and repeatable manner For the past 30 to 40 years, 6-axis Measurement While Drilling (MWD) tools have been providing downhole surveys that allowed estimating the actual wellbore trajectory. Since the 1990s the same fundamental MWD tool technology has largely been adapted between vendors. The difference has been in procedures and calibration. It was known that the measurements were not without uncertainty, but initially there was no single mutually agreed way to describe and quantify the uncertainties. The SPE Wellbore Positioning Technical Section (WPTS), also known as the Industry Steering Committee on Wellbore Survey Accuracy (ISCWSA), was founded in 1995 by a group of operators and service companies to agree on a common Positional Uncertainty Model (PUM) that could describe a common way of calculating the Ellipses of Uncertainty (EOU) describing the accuracy of a generic MWD survey. This resulted in the publication of the SPE paper 67616 in 2000 (Williamson 2000). The ISCWSA briefly describes its purpose as: "The Industry Steering Committee on Wellbore Survey Accuracy (ISCWSA) was founded to dispel the confusion and secrecy commonly associated with wellbore surveying. And to enable the industry to produce consistent, reliable estimates of survey-tool performance in today's wells. We achieve these goals through the production and maintenance of standards covering the construction and validation of tool error models" (ISCWSA 2025a). "In general, ISCWSA does not define or supply the detailed magnitudes (error models, tool codes or IPM files) for a particular survey tool. It is our position that the tool provider is the one who is best placed to assess the uncertainty when using their equipment. Therefore, users should request tool codes from their tool provider. ISCWSA does not supply, check, certify or in any way warrant such error models created by tool providers." (ISCWSA 2025b). What is commonly referred to as the ISCWSA MWD error model, is in fact a generic conservative model. However, using the huge amount of MWD survey data available to most operators, most large vendors’ MWD tools—when the correct procedures are followed—have been shown to qualify for the error model. The raw survey data and the algorithms are also commonly shared, such that third parties can provide Quality Assurance (QA) and Quality Control (QC) for the surveys. What hitherto has been referred to as MWD surveys, will in this paper be referred to as static-six-axis-MWD-surveys (SSAMWD). These surveys are not acquired during drilling operation, but during a halt in the drilling operation, where the bit is pulled off bottom and the drill-string is stationary. Contrary to this, a continuous-6-axis survey that is acquired during rotation of the drill string and while actively drilling, may be called "Continuous-rotating six-axis-magnetic measurements" (CRSAM). This type of continuous-6-axis survey was proposed (Lowdon 2019) and executed survey cases presented (Elgizawy 2020, Herrera Anda 2024). What the continuous 6-axis survey lacked was a commonly agreed PUM. Following a pragmatic comparison of SSAMWD and CRSAM surveys (Dreisig and Reynaud 2023), the work on an ISCWSA PUM was kicked off at the 59th ISCWSA meeting (Willerth 2024). A preliminary PUM for 6-axis continuous surveys was presented at the 60th ISCWSA meeting (Willerth and Akklestad 2024) that as time of writing this paper has turned into a release candidate (ISCWSA 2025c). For a vendor to justify using the error model, they need to provide sufficiently large datasets to show that their tool and procedures qualify for using the proposed PUM. Without appropriate confidentiality agreements, it can be hard to share these datasets. What is required is a method to show that the continuous six-axis surveys for a specific tool and wellbore can be shown via statistical analysis of the survey data, to be likely to qualify for the proposed PUM. This paper presents results from field tests executed on onshore horizontal wells in a non-conventional play in an Argentinian field, with a history of over 50 analogous wells already drilled. Furthermore, the paper outlines an approach for qualifying CRSAM survey performance in real-time during drilling operation. The paper demonstrates that CRSAM surveys offer a method to achieve this objective with quantifiable uncertainty and demonstrate the applicability of CRSAM surveys as a definitive reference to drilling automation algorithms.