A New Wellbore Position Calculation Method (2002)

A New Wellbore Position Calculation Method C.R. Chia; C.R. Chia Schlumberger Search for other works by this author on: This Site Google Scholar W.J. Phillips; W.J. Phillips Schlumberger Search for other works by this author on: This Site Google Scholar D.L. Aklestad D.L. Aklestad Schlumberger Search for other works by this author on: This Site Google Scholar Paper presented at the IADC/SPE Asia Pacific Drilling Technology, Jakarta, Indonesia, September 2002. Paper Number: SPE-77221-MS https://doi.org/10.2118/77221-MS Published: September 09 2002 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Chia, C.R., Phillips, W.J., and D.L. Aklestad. "A New Wellbore Position Calculation Method." Paper presented at the IADC/SPE Asia Pacific Drilling Technology, Jakarta, Indonesia, September 2002. doi: https://doi.org/10.2118/77221-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)IADC/SPE Asia Pacific Drilling Technology Conference and Exhibition Search Advanced Search AbstractA method is described for combining multiple wellbore surveys to obtain a single composite, more accurate, well position. Established methods for defining the wellbore position, and its associated uncertainty, rely upon accepting the position obtained from the most accurate survey instrument used in each section of the wellbore. This position is then assigned an uncertainty based on the information from this single survey instrument run. Today, when a modern wellbore is constructed, each section may be surveyed for position many times using one or more magnetic, gyroscopic or inertial survey instruments. By statistically combining the wellbore positions obtained from all of the survey instruments run in a given section of the wellbore a new position, designated the 'Most Accurate Position' (MAP), is calculated. The main advantage of the MAP is that its uncertainty is smaller than the uncertainty of any of the constituent surveys. The major benefits of this technique will be to facilitate the drilling of smaller targets at greater distances, allow the drilling of new wellbores in closer proximity to existing wellbores while maintaining accepted safety clearance rules, and improved reservoir delineation.Describing Well PositionThe wellbore trajectory is defined as a series of surveyed points in three-dimensional space typically described in a North, East and Down reference system. These points are joined together to form a continuous trajectory using a geometrical calculation method1. Most magnetic or gyroscopic survey instruments in use today provide a survey point that is referenced to measured [or along hole] depth that is obtained from the driller's pipe tally, or from a wireline spooling measurement. The survey instrument provides inclination (hole angle) and azimuth (direction) measurements. When these parameters are used to calculate trajectory with an assigned survey depth, the horizontal displacement [or North and East coordinates] from the origin, and the vertical depth [or Down coordinate] from the elevation reference can be derived. Alternatively, some inertial survey instruments measure displacement in three-dimensional space from a known initialization point, and from which all of the above parameters [including depth] can be obtained to achieve the same purpose.Wellbore Position UncertaintyWellbore survey requirements are typically driven by the need to guide the well to a geological target, to avoid other wells, to ensure that property boundaries are respected, and to record the position of the wellbore for future reference. In order to visualize and quantify our ability to hit a target or avoid colliding with another well, position uncertainty is assigned to wellbore trajectories. This position uncertainty represents our modeled knowledge of the collective errors arising from both the intrinsic performance limitations of the survey sensors and those induced by the operating environment2. This uncertainty is defined as a statistical confidence region with an associated confidence level. In three dimensions the confidence region is most often depicted as an ellipsoid3 because ellipsoids are the constant value contours of the three-dimensional Guassian probability density function. Such a confidence region is commonly referred to as an 'Ellipsoid of Uncertainty' (EOU). The EOU is used in target analysis, for example, by reducing the size of the geological target by the size of the EOU to define a drilling target. In this fashion, the geological target will be achieved if the wellbore penetrates the drilling target. Likewise EOUs are used to assess collision risk by considering the proximity of the EOUs from adjacent wells. Keywords: machine learning, upstream oil & gas, drilling operation, position uncertainty, well position, survey program, artificial intelligence, well planning, wellbore position calculation method, covariance matrix Subjects: Well Planning, Drilling Operations, Trajectory design This content is only available via PDF. 2002. 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