Importance of Deep Borehole Surveying

Abstract

DESIGNERS of apparatus for surveying deep boreholes have in the past consistently underestimated difficult engineering problems necessarily attendant on such surveys. On April 10, W. E. Bruges read a paper before the Institution of Petroleum Technologists in which he made some pertinent remarks on the usefulness of well surveys as an adjunct to drilling logs and geological data. Geologists can utilise the results of accurate surveys for correcting underground contours, choosing such surface locations as will ensure economic spacing of wells in the oilsand below and making deductions as regards the formation as a whole from direction, deviation and irregularities of the hole as portrayed by the survey. Administration is facilitated by a knowledge of exact spacing of wells in an oilsand. Decisions regarding drilling activities can be taken with confidence, and the risk of overcrowding, hence decreasing production, is minimised. Recent experiments in Burma have shown that of available apparatus for this work, that designed and manufactured by Martienssen is the most satisfactory. The instrument is fitted with a gyroscope for obtaining direction and two pendulums for inclination, results being recorded photographically. It has the advantage that the gyroscope is unaffected by magnetic influences, while the pendulum method of obtaining inclinations allows a number of readings to be taken at one run. Photographic recording of results means that the instruments below ground can be light, obviating necessity of following-up gear; moreover, their relative places in the well can be photographed without disturbing position or setting.