ABSTRACT: Laboratory Techniques for Migration Studies
BOULT, PETER, and ROBERT EAST, University of South Australia, South Australia, Australia
Laboratory measurement of displacement pressure on seal type lithologies can be performed using actual formation fluids or calculated using the less-rigorous but routine mercury injection method. Data obtained from the mercury injection technique can be equated with data from breakthrough tests using actual formation fluids by measuring the static adhesion tension between the formation fluids and applying the well-known equation to convert laboratory data to reservoir data, i.e., breakthrough pressure reservoir = breakthrough pressure laboratory x (adhesion tension reservoir/adhesion tension laboratory). These data can then be used to determine hydrocarbon column heights beneath seal lithologies.
As leakage occurs through the seal, capillary forces are reduced and migration occurs until the upward buoyancy forces acting on the hydrocarbons are insufficient to overcome the capillary forces associated with the pore-throat size of the seal. Residual oil zones can be explained by the interplay of capillary forces, which cause leakage (static adhesion tension) and snap off (dynamic adhesion tension).
This presentation reviews and compares laboratory displacement pressure data from the two methods and status versus dynamic adhesion tension data obtained using a Wilhemy plate technique. The practical applications of the data in assessing hydrocarbon column height beneath the major regional seal of the Eromanga basin in Central Australia (the Birkhead Formation) is illustrated. Also discussed and illustrated is data which provides an explanation for the presence and magnitude of residual zones beneath hydrocarbon accumulations.
AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)