Dynamic Error Analysis of Measurement While Drilling Using Variable Geomagnetic In-Field Referencing

Abstract

Summary The safe and economical determination of a wellbore trajectory in directional drilling is traditionally achieved by measurement-while-drilling (MWD) methods, which implement magnetic north-seeking sensor packages. Inaccuracies in the determination of well path arise because of random and systematic errors in the measurements of the sensors. Multistation analysis (MSA) and magnetic in-field referencing (IFR) have already demonstrated the potential to decrease the effects of errors because of magnetization of drillstring components along with variable errors caused by irregularities in the magnetization of crustal rocks in the vicinity of wells. Advanced MSA methodologies divide a borehole into several sections and use the average reference values of the total magnetic field, declination, and dip angle for analysis of errors in each section. Our investigations indicate that the variable-reference MSA (VR-MSA) can lead to a better determination of errors, specifically in areas of high magnetization. In this methodology, magnetic reference values are estimated at each station using forward and inverse modeling of surface-magnetic observations from IFR surveys. The fixed errors in magnetometer components are then calculated by minimizing the variance of the difference between the measured and unique estimated reference values at each station. A Levenberg-Marquardt algorithm (LMA) is adopted to solve the nonlinear optimization problem. Examination of this methodology using MWD data confirms more than 20% improvement in well-path-determination accuracy by comparing the results with the corrected path from the conventional MSA method and gyro surveys.

Efficient Removal of Magnetic Contamination From Drilling Fluids: The Effect on Directional Drilling

“…Contamination of the drilling fluid by iron and steel particles resulting from erosion or wear from casing, drill pipe and BHA components during drilling and well operations and following fluid additives has earlier been found to be a source for errors in magnetic directional surveying [7,8]. Both from laboratory tests and field experience, it is observed as having a non-trivial effect of magnetic and paramagnetic contamination of the drilling fluid on wellbore position accuracy [9,10,11].…”

Quantifying Global and Random Uncertainties in High Resolution Global Geomagnetic Field Models Used for Directional Drilling

“…Directional drilling requires subsurface navigation to targets that are often distant from the drilling pad (Poedjono et al, 2018). To navigate underground surveyors collect magnetic and accelerometer data from survey tools which obtain measurements of geomagnetic-field strength and angle of dip at a drilling location (Kabirzadeh et al, 2018). These are compared against modelled estimates from a global model of the geomagnetic field and should match to within an expected tolerance (Jamieson, 2017).…”