Abstract/Excerpt

Hydrocarbon Accumulation Mechanism and Fluid Phase Determination: A New Workflow Guiding Exploration

Alan Z. Yu
BHP Billiton Petroleum, Houston, TX, USA

An innovative methodology is presented to determine the hydrocarbon accumulation mechanism, reservoir fluid phase and properties, and column heights in a basin. The method demonstrates the intrinsic relationships between all necessary elements including source rock, basin evolution, structure, reservoir, seal, hydrocarbon migration and fluid property, and reveals the fundamental controls during hydrocarbon accumulation processes.

The primary controls of in situ hydrocarbon phase are source rock characteristics, its burial and thermal history, and the temperature and pressure in the reservoir (Figure 1). These determine if the reservoir contains an under saturated single -phase or saturated two-phase hydrocarbon columns. The secondary controls comprise the oil and gas volumes available to trapping, top seal capacity, structure closure height, container volume, and physical properties of the fluid. These are factors which influence the dynamic state of accumulations (i.e. undercharged, top leaking, bottom spilling, or both of leaking and spilling) and determine if the reservoir contains a saturated two-phase or single-phase hydrocarbon column. The most likely accumulation scenarios with the secondary controls are identified and discussed (Figure 2).

This new understanding of hydrocarbon accumulation mechanism is of critical importance in exploration decisions. A generic workflow incorporating the methodology applicable at any stage/scale from regional, through basin, to individual prospects is also presented.

Figure 1.

Figure 2.

AAPG Search and Discovery Article #120098©2013 AAPG Hedberg Conference Petroleum Systems: Modeling the Past, Planning the Future, Nice, France, October 1-5, 2012