Hereditary wells and early extraction
Long before the first industrial oil derrick, the region of central Myanmar was dotted with wells that produced petroleum, or "earth-oil." This indigenous industry dates back centuries, with records of oil extraction beginning as early as the Bagan period around 905 CE. At Yenangyat and the nearby Yenangyaung field, families operated these wells under a hereditary system. The rights to dig for and extract oil belonged to a group of 24 families known as the twinzayo. This entitlement was passed down through generations, creating a unique socio-economic structure centered on petroleum.
The digging process was a significant undertaking, sometimes lasting up to two years for a single well. Workers dug pits by hand, reaching depths of over 100 feet (30 meters), with some exceptional wells reportedly reaching 400 feet. To lower a digger and haul out soil and, eventually, oil, they used a simple rope and pulley system mounted on two wooden posts. The crude oil was collected in earthenware jars, each holding about 20 kilograms, and transported by bullock cart to the riverside. Archaeological evidence and historical accounts show that bamboo was a primary material, used for scaffolding but also for lining the well shafts to prevent collapse. This early use of casing shows a sophisticated understanding of geological pressures.
The industrial transition
The arrival of the British and the formation of the Burmah Oil Company in 1886 marked a turning point for the region's oil industry. The company began mechanical drilling at Yenangyat in 1891, applying new technologies developed in Europe and America. They introduced steam-powered cable-tool drilling rigs in 1888, followed by rotary tools in 1911, which allowed for much deeper and faster well completion. The first mechanically drilled discovery on the Yenangyat anticline occurred in 1893. By the end of the 19th century, production from these new wells averaged 500 barrels per day of a high-quality, light crude.
The geology of the Yenangyat field is a distinct anticline, an upward-arching fold of rock strata that traps oil. This structure was first scientifically identified in relation to petroleum accumulation by geologist Thomas Oldham in 1855, who observed that traditional wells were concentrated on the highest point of the fold. This was one of the earliest documented applications of structural geology to oil exploration. The industrial wells drilled by Burmah Oil targeted these same Pliocene and Miocene sandstone reservoirs but could reach them at greater depths and with higher efficiency than was ever possible by hand. By the early 20th century, the region was a major producer within the British Empire, with a pipeline constructed in 1908 to carry crude oil to refineries near Rangoon.