FAULT DELINEATION IN OIL BASED MUD AT WEST MONTALVO FIELD USING A 3-D RESISTIVITY TOOL

The exploitation of West Montalvo field has been recently invigorated when the field was purchased by Venoco in 2007. Long term success in this effort is dependent on gaining an accurate picture of the faults that segment the field. Data available from the previous drilling programs is from the 1950s & 60s and has some structural ambiguities. The recent drilling program helped to gain a better understanding of the reservoir characterization and also the structural geology. The delineation of important faults is made more complex because of the required oil based mud system and the large amount of sedimentary effects on the observed bedding dips. However, a new 3-D resistivity tool was run on wireline to provide dip corrected resistivities and formation structural dip. This induction tool contains a series of 3-axis, co-located, transmitter and receiver coils which provide sensitivity to resistivity anisotropy in the formation. Dipping beds or angled boreholes can be accurately measured with this tool. So in the oil based mud environment where standard resitivity imaging and dip analysis is more difficult, this tool provided both resistivity and formation dip information that allowed the identification of a major fault in West Montalvo field. These data has been integrated into the 3-D geologic model as an important control on the fault characterization. Currently these data are used to further constrain the 3-D geologic model that will aid in the future development of the West Montalvo field.