In the early years of oil well drilling the process of drilling the borehole was more of an art than a science. The general principals of geology and exploration were understood and followed but the effects of formation changes and dip on bit deflection and hence borehole trajectory were not clearly understood and largely ignored. This perpetuated state of ignorance lead to many unresolved lease disputes, where wells drilled and brought on stream, close to an adjacent lease, would often result in diminished production rates on the adjacent lease wells. However, as now, wells already in production were cased and the magnetic compass based survey instruments available, could not provide post completion trajectory data. Throughout this time, many inclination-only devices were developed, later versions of which were accurate to 1 or 2 degrees throughout their operating range.
In 1928 Alexander Anderson published a study of Borehole Survey Inclination Data obtained from a significant population of wells from various locations. Anderson had developed a Pendulum Instrument, the position of which was recorded on film as the tool was lowered in the borehole. This publication, illustrating universal and significant wellbore deviation, brought focus on the extent of the problem within the industry. As a direct result of Andersons study, J. N. Pew, then the Vice President of Sun Oil Co. instructed a team of Engineers working out of the Sun Research Laboratory in Dallas, to design and develop instruments which would provide the Inclination of the borehole and the Direction of that Inclination within casing. The 5.5” SURWEL Gyro Instrument incorporated a Gyro Compass Face superimposed over a Bubble Level Unit with the permanent record obtained with a Camera.
The Sperry Gyroscope Co. was chosen as the Gyro supplier and with each company holding a 50 per cent stake in the new company, the Sperry-Sun Well Surveying Company was formed and gyro referenced borehole surveying became a reality on 9th October 1929.
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