Resources
Technical resources.
How wellbore positioning actually works: the confusing parts of the surveying industry, explained by the engineers who run the corrections.
Explainers
The concepts.
- 01Ellipse of UncertaintyHow survey errors affect estimated wellbore position, and what determines the size and shape of the uncertainty.
- 02Collision AvoidanceHow well spacing, survey uncertainty, and operator rules determine clearance.
- 03Geological Target AnalysisHow survey uncertainty and target geometry affect confidence in well placement.
Articles
The deep dives.
- 01How a Gz bias reaches inclination, dip and azimuthWhat a bias on the axial accelerometer does to inclination, TVD, magnetic dip, and long and short collar azimuth, why a gravity check misses it in a lateral, and what multi-station analysis does with it.
- 02Travelling cylinder plots: what they show, and why two can disagreeHow the reference trajectory, point selection, and plot orientation change a travelling cylinder diagram.
- 03Long collar vs short collar: choosing the azimuth method and error modelHow axial magnetic interference, reference uncertainty, and well geometry affect the choice of MWD azimuth calculation and error model.
- 04How your main field model shapes the ISCWSA error modelHow magnetic reference uncertainty and modeled correlation between wells enter the ISCWSA error model, from the original MWD terms to Rev5 and location-specific estimates.
- 05Diurnal variation: effects on magnetic MWD surveysHow solar-quiet currents, latitude, seasons, and geomagnetic storms change the magnetic reference used for MWD surveys, with measured observatory examples.
- 06Choosing a magnetic reference model for MWD surveysCompare IGRF, WMM, WMMHR, BGGM, and HDGM by spatial resolution, validity, data coverage, and uncertainty for magnetic MWD surveys.
- 07Bias vs Scale Factor Error in MWD SurveysHow sensor offsets and gain errors affect MWD readings, calculated angles, and position uncertainty, with examples and MSA limitations.
- 08Systematic vs Random Errors in Wellbore SurveyingHow error magnitude, survey geometry, and correlation affect wellbore position uncertainty, with ISCWSA propagation modes and a straight-section example.
Accuracy enhancements
The corrections, one by one.
- MFMMain Field ModelCalculate magnetic reference values and document their uncertainty for MWD survey processing.
- IFR1In-Field ReferencingEstimate local crustal magnetic contributions and their uncertainty for MWD survey references.
- IFR2Interpolation In-Field ReferencingEstimate temporal magnetic variation at the wellsite using suitable observatory data.
- SAGBHA MisalignmentEstimate directional sensor misalignment from BHA deflection and apply accepted inclination corrections.
- MSAMulti-Station AnalysisEstimate systematic directional sensor corrections during drilling when suitable survey data is available.
- HFSHigh Frequency SurveyingUse suitable high-density directional measurements to improve estimates of the path between conventional survey stations.
- BYSIn developmentBHA Yield SurveyingIn development: estimates of BHA build and turn tendencies under stated conditions.
Next step
Send us one well.
Tell us about one well. We reply within 24 hours, and once the raw sensor data arrives we review it and tell you what we find.