Characteristics of petroleum geology of the Baise Basin in Guangxi, China

Abstract

Baise Basin, which covers an area of 830 km2 (320 mi2) with a length of 109 km (70 mi) and a width of 7–14 km (4–8 mi) and strikes northwest, is a Paleogene lacustrine-faulted basin. Its formation experienced synrift, regional subsidence, and uplift and erosion. Its Paleogene depositional environments experienced changes from flood-plain or alluvial-fan facies to fluvial facies, delta facies, lacustrine (fan-delta facies), and then fluvial facies, all of which combine to reflect the evolution from individual fault-controlled depocenter through maximum areal development and subsidence and then shrinkage. The Nadu Formation lacustrine mudstones, with thickness ranging from 300 to 600 m (980 to 1970 ft), are the main source rocks. The in-place potential resources in the Baise Basin have been estimated to be 73 106 t (540 million bbl) of oil and 77 108 m3 (270 bcf) of gas. Three biodegraded oil pools, seven oil fields, and five gas pools have been discovered. Oil and gas pools are characterized by thin reservoirs, small area distributions, and shallow burial depth and can be classified into three types: structural, stratigraphic, and combined structural stratigraphic. The proven reserves of oil total 123 105 t (91 million bbl), and those of gas total 7.7 108 m3 (27 bcf). The ratio of proven oil reserves to in-place potential oil resource is about 16.9%, suggesting that the basin still has considerable potential for oil exploration. Reservoirs deeper than 2000 m (6500 ft) in stratigraphic and subtle traps have a major potential for exploration and are the favorable targets of the future.