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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Effects of Contemporaneous Structural Movement on the Sedimentation at Thornwell Field, Jefferson Davis and Cameron Parishes,
Louisiana *
By
Consulting Petroleum Geologist, Houston, Texas
*Presented before the Houston Geological Society June 12, 1961.
The Lower Miocene producing trend of Southwestern Louisiana is one of the more prolific gas producing trends of the Gulf Coast Province. Thornwell field is located along this trend in Jefferson Davis and Cameron Parishes. The field was discovered in 1942 by Cities Service Oil Company which produced gas and condensate from a Planulina palmerae sand between 9,600 and 9,700 feet. After this shallower production was depleted Pan American and Austral Oil drilled deeper test wells and discovered gas and condensate in the Discorbis gravelli, Marginulina vaginata, Marginulina howei and Miogypsinoides "A" sand sections.
The stratigraphic section penetrated in this area consists of sands and
shales of varying thickness. This thickness depends on the location with reference
to contemporaneous faulting where present and large structural features
when the faulting is not present. The contemporaneous faulting appears not to
be present on the Thornwell structure prior to Camerina time and the thickness
of the older section is dependent on the structural position on the dome. After
the beginning of Camerina time contemporaneous movement was taking place
and the structurally high fault
blocks have thin stratigraphic sections with poor
sands and the section becomes thicker and the sands better in each successively
lower
fault
block.
The Thornwell field produces from domal type structure with a complex
fault
pattern consisting of a large normal northeast striking
fault
that branches
into smaller radial faults as it enters the field from the Southwest. The
structurally higher
fault
block is the northwesterly block and each block becomes
successively lower around the structure in a clockwise direction.
The Thornwell field has not been sufficiently drilled to determine its true
reserves. Production has been established in six sands, most of which have not
been tested or developed on the south side of the structure because of the
extreme depths. The Cibicides hazzardi and Marginulina texana sections have
only been penetrated in the structurally highest fault
block where no sands were
found. Both of these sections may possibly have productive sands in the lower
fault
blocks if they can be reached by the drill.
End_Page 13-------------------------
Unnumbered Figure. Structure Contour Map, Thornwell Field.
End_of_Record - Last_Page 14--------