Wellbore Positioning, Quality Control and Error Models
Nestor Eduardo Ruiz
Gyrodata
Abstract:
Good wellbore positioning; including techniques for avoiding collisions or finding and intersecting other wells is critical to control catastrophic blow out accidents, rescue stranded miners, drill close proximity wells with minimal environmental impact, or drill wells with complicated trajectories that access new reservoirs.
The trajectory of an oil well is at best an estimation of where the well is, based on available measurements. Uncertainties on the position of the wellbore increases as points on the wellbore trajectory are further away from the wellhead. An error model represents the survey tool behavior, modeling errors and uncertainties of the tools and accounting for measurement procedure. The result is a statistical representation of the uncertainty, with a 3D ellipsoid centered at each survey point of the wellbore trajectory.
Quality control of the data to assure the correct measurements, readings taken within the range of tool calibration, magnetic measurements free of magnetic interference, etc. is crucial to avoid gross errors. Internal quality control in a survey is not by itself sufficient to assure a survey free of gross errors. Performing two independent surveys is the best way to detect gross errors and to confirm that a survey can be represented by its error model. The use of data without the adequate QC is risky and does not provide assurance of the position of the well or its uncertainty. Several examples will be used to illustrate the benefits of directional data quality control.
Biography:
Nestor Eduardo Ruiz received his Electronic Engineer degree at the University of Buenos Aires Argentina. He started his career in 1983 as a field services engineer and then moved into development and producing directional software, for planning and controlling wellbore trajectories, of directional wells. He was in charge of the directional drilling magnetic survey tools and software. He planned the trajectories of the first horizontal wells drilled in Argentina which also included blow out well experience. As LAS manager for Gyrodata, In 2010 he was involved in the planning and supervision of the gyro directional drilling surveys, in the C miner rescue plans in Chile.
Nestor also was SPE chairperson of the Patagonia section and gave presentations of directional surveys in universities of Argentina, Brazil and Peru in the last years. He also participate in several ISCWSA meetings. In addition to English, he speaks Spanish and Portuguese.