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Intergranular Tar in a Deepwater Reservoir: Part II – Migration Modeling of Asphaltene Precipitation

David Kennedy1, Nishanth Kalyanaraman2,3, Keith Mahon2, and Dan Carruthers1
1The Permedia Research Group, 577 Somerset St. W, Ottawa, Ontario, Canada
2Anadarko Petroleum Corporation, 1201 Lake Robbins Drive, The Woodlands, TX 77382
3Bureau of Economic Geology, Jackson School of Geosciences, Austin, TX 78758

The processes by which fluids (and rocks) can be altered during petroleum migration are manifold, and including all possible mechanisms in a numerical model is a significant challenge. These challenges are related to the sheer number of processes which could be modeled, arriving at a consensus on their respective numerical implementations and the interdependencies of the processes. Traditional petroleum migration software modeling tools are fixed in what processes they model, with most modeling buoyancy driven migration with little to no rock-fluid interaction and alteration. Modelers would like to account for various syn-migration processes in their numerical migration experiments, and have the flexibility to alter the process implementations as appropriate.

This poster will describe a "Reaction Plugin Interface (RPI)" that we have developed to facilitate these numerical experiments. The RPI is a public C interface which allows modelers to create reaction plugins for proprietary fluid and rock property alteration schemes. The RPI can be used to create a reaction plugin to alter the rock or fluid properties of a migration model. The processes by which this alteration can occur can be chemical, biological or otherwise. Because the interface is programmatic, any method can be used to provide the alteration. This can include calls to various user functions, the use of lookup tables stored in external files, formulas, links to an external database or hard coded values. Typical reactions could include biodegradation, secondary cracking, diagenesis and more. Virtually any operation that can be characterized by rock and/or fluid property changes can be accessed through this interface.

Having better tools to predict asphaltene levels are important since asphaltenes can create significant production challenges by diminishing reservoir production quality, by plugging wells and flowlines through deposition, and fouling facilities. A Gulf of Mexico case study, using the RPI to model asphaltene precipitation, will be shown. In addition, the precipitation algorithms will be described. The case study will show how asphaltene precipitation can occur along hydrocarbon migration pathways, within the reservoir, and in migration baffles. The highest concentration of intergranular tar are predicted in breeched paleo-traps and near the top of the main reservoir intervals.


AAPG Search and Discovery Article #90091©2009 AAPG Hedberg Research Conference, May 3-7, 2009 - Napa, California, U.S.A.