ABSTRACT

Turtle Bay Field, located about 40 miles due east of Houston, occupies a low-relief anticline which was formed by subsidence into rim synclines around several salt domes regionally up-dip (north) from the field. The southeast flank of the anticline remained stable as the regional southeast dip was reversed to form a northwest flank by subsidence of the strata into rim synclines around Moss Bluff, Lost Lake and Hankamer salt domes. The Heterostegina limestone of the Anahuac formation (Oligocene) is thicker than normal in the area showing reversal of regional dip, a change which may be used as a criterion to localize the search for more such structures in the Houston district.

The field produces oil and gas from the stratigraphically highest extensive sandstone (about 10 feet thick) in the Marginulina zone of the shaly Anahuac formation. It is believed that this sandstone served as an aquifer to carry off the water squeezed from the enclosing shales as they were compacted, that the oil and gas travelled with the water, and that these were left behind through gravitational separation in the anticline. Continued flow of compaction water in a regionally up-dip direction is suggested by an apparent northwest tilt of the oil-water contact.