Abstract

Conventional approaches to petroleum exploration rely on the estimation of trap capacity as their guide for resource assessment. However, all too often hydrocarbon traps are devoid of hydrocarbons or contain insufficient quantities of hydrocarbons to reach the spill-point. Under such circumstances the availability of hydrocarbons to the trap, not trap capacity, is the factor limiting the quantity of hydrocarbons in place.

Advances in petroleum exploration geochemistry now permit a reliable means of addressing the supply-side of resource assessment, i.e., the quantity of hydrocarbons generated, migrated and entrapped within a basin or sub-basin. This technique, called the supply-side approach, incorporates the measurement or prediction of certain geochemical attributes, including hydrocarbon generation potential (commonly represented by the S₁ + S₂ of "Rock-Eval" pyrolysis), nature of the kerogen (gas vs. oil-proneness), and level of thermal maturity. These parameters are then used to define both the quantity of oil generated per rock volume and the generative volume itself. Geologic considerations are used to constrain the transfer efficiency from the source rock to the reservoir. These considerations include, but are not limited to, the relative timing of hydrocarbon generation and trap development, the nature of the carrier system (i.e., clay-rich vs. quartz-rich), and tectonic stability. An example of this supply-side approach is presented for a portion of the Central Sumatra region.