Heat flow study results and geothermal energy distribution in the Vietnam offshore sedimentary basins

The study of the heat flow in Vietnam’s offshore oil basins has been carried out at the Vietnam Petroleum Institute by using data from 80 exploratory wells, distributed from the Song Hong basin in the North to the Nam Con Son basin in Southern part of the Vietnam East sea. The thermal conductivities of 427 cores were measured using equipment from CCOP, brought to Vietnam by Dr. O.Matsubayashi and simultaneously using the Thercon 2 - 1992, high quality new Vietnamese-made equipment designed and manufactured by Prof. Dam Trung Don of Hanoi University. The temperature gradients of wells were calculated from well log data and from well tests data. The average heat flow values of sedimentary basins in offshore Vietnam are as follows: Song Hong basin (119mW/m2), Da Nang basin(89mW/m2), Cuu Long basin (64mW/m2), Nam Con Son basin (80mW/m2). The distribution pattern of heat flow in a sedimentary basin is believed to be related to its tectonic history. The heat flow and temperature history are the consequence of the geological history of a basin, therefore the main phases of rifting and phase of recent volcanic activity will be the primary sources of thermal energy in Vietnam’s sedimentary basins (Fig.2). The Red River Fault (RRF) in the Song Hong basin, the North - South trending fault in the Bac Bo gulf, and others faults are important thermal channels in offshore Vietnam. The coal beds in the Song Hong basin, the Rotalit shale in the Cuu Long basin and the local shale layers in all basins are good thermal sealing layers. Due to the differences in geological characteristics and heat flow regime, Vietnam’s sedimentary basins have different geothermal energy distributions. Their thermal regimes are generally conducive for providing the conditions necessary for the maturation of hydrocarbon source rocks and facilitating the migration of oil to the traps. Also, with high heat potential, the geothermal energy of some regions is favourable for power generation and for other industrial and human needs.