Basin-centred gas in the Makó Trough, Hungary: a 3D basin and petroleum system modelling investigation

World-wide exploration for unconventional hydrocarbon accumulations has been increasing in the last decade. The deep Makó Trough of the Pannonian Basin in southeast Hungary has become a new target for companies looking for unconventional gas resources, but so far the exploration drilling has been unsuccessful.

To investigate the size of the assumed basin-centred gas accumulation we have studied the hydrocarbon potential of the source rocks in the Makó Trough using 3D basin and petroleum system modelling technology. The thermal and maturity history and timing of hydrocarbon generation were assessed, and the generated volume of hydrocarbons estimated and compared with the pore volume of the assumed unconventional reservoirs. The estimated mean volume of gas generated in the drainage area (490–650 × 109 Sm3) [given at surface conditions] is much less than the volume (>14 × 1012 Sm3) needed to fill the basin-centred gas accumulation. Therefore, the Makó Trough is unlikely to contain a large tight-gas sand accumulation. The Endrőd Marl is a fair quality, gas-prone source rock with average original TOC values of 0.75 wt%, reaching 1.5 wt% in the Hód-I and Makó-7 wells. These are below the TOC values of the proven gas shales of North America.