Abstract
This paper presents aspects of formation stress sensitivity influencing the successful simulation of the Tar Zone in Fault Block IIA of the Wilmington Oil Field in Los Angeles County, CA, USA. The Tar Zone is a slope and basin clastic type reservoir. The significant compaction experienced during the primary phase and the subsequent rebound during the following waterflooding created a complex case of reservoir definition for projection purposes. Uncertainties regarding stress effects on physical properties such as porosity, permeability, compressibility and formation thickness complicated the representation. The history matching attempts revealed the insufficiency of using conventional compaction models in the appropriate modeling of the compaction-rebound process. A new compaction-rebound feature was developed based on rock mechanics considerations and was incorporated into a commercial simulator, Computer Modelling Group's STARS™ simulator. This method allows for meticulous representation of the spatial dynamics of compaction/rebound based on the local pressure field.
A successful history match of the primary and waterflooding production was achieved with the new compaction/rebound algorithm. The model was successfully tested by predicting the 20 acre steamflooding pilot. The case under consideration is unique and relates to high pressure and temperature steamflooding. The proposed methodologies have widespread application in other stress-sensitive heavy oil reservoirs.
