Chapter 10 Historical review of the contribution of geophysics to petroleum discoveries in the Tertiary basins of Myanmar

Abstract

Petroleum resources from seeps or shallow excavations have been exploited by local people in Myanmar for at least 900 years for use in lighting, for medicinal purposes or as an insect repellent. When the British took over Lower Myanmar, crude oil obtained from Yenanchaung and refined in Duneedaw was supplied to India and exported to the United Kingdom or the United States of America. After the British occupied the whole of Myanmar in 1884, the Scottish Burmah Oil Company was established in the following year and commenced commercial extraction of oil from Yenangyaung; in 1902 Chauk was discovered. After 40 years of exploitation production began to decline, and further resources were sought. In 1938–40, before the Second World War in the Pacific, geophysical methods of gravity measurement by Shell and the Anglo-Iranian Oil Company (now BP) covering the whole of Myanmar were planned to aid oil exploration. A network of measurements were established along all accessible roads and navigable rivers throughout the Tertiary Belt of Central Myanmar using Holweck, Thyssen and Ising torsion balance and pendulum gravimeters. The Holweck instrument uses an inverted pendulum to measure absolute values of gravity to an accuracy of 2–3 mGal. The best results were obtained with the Thyssen gravimeter, producing weighted deflection readings for about 90 stations a month, to an accuracy of 0.5 mGal or less. The Ising gravimeter, also using an inverted pendulum, can provide drift readings with a better productivity from 149 stations a month, with an accuracy of ±1 mGal. In all these surveys, with station intervals ranging over 1–5 km a total of 5–12 km could be covered each day. Elevation corrections were made from contours obtained during the topographic survey. The AA company completed gravity pendulum measurements over 80 000 square miles in Myanmar at a total cost …