ABSTRACT

Gay (1989) described the concept of lateral variations in compactibility within a stratigraphic section, specifically lateral variations from sand to shale. Cross sections and net sand maps from West Cameron Block 225 Field were chosen to illustrate this concept where several channel sands are seen to strongly influence the structure.

The basic structure within the field consists of a gentle southerly dipping ridge, bounded by faults to the west and north. Gentle roll into these faults closes the north flank of the structure.

The stratigraphic section consists of alternating sands and shales of Miocene and Pliocene age. Several of these sands map as linear bodies interpreted to be channels oriented in a general east-west direction.

The juxtaposition of the basic structural orientation with the orientation of the channel sand sets up a crossing point on the southern flank of the structure. With the advent of the differential compaction of the channel sand versus the bounding shale facies, a structure is generated. This resulting compaction structure is mapped as a double-crested or saddled high.

This effect is amplified as additional channels stack out over the southern flank of the structure. The overall result is one of migrating structural crests due to variations in compactibility within the stratigraphic section. With adequate well control, stratigraphic analyses can identify similar subtleties in structure due to compaction.