WHARTON, STANLEY R., Trinidad and Tobago Petroleum Company Ltd., Santa Flora, Trinidad

ABSTRACT: Exploration within a Complex Thrust-Fold System -- Moruga East Field, Trinidad

The Moruga East field is located in the south-eastern part of Trinidad within an area bounded by basement-related thrust faults. The application of recent models has led to the interpretation of the structural styles of the field for refining play concepts for exploration. A cross-sectional network for well-to-well correlations, migrated seismic, conventional aerial photographs and Trend Surface Analysis, were used for the structural and stratigraphic interpretation of the area.

Structural elements are represented by asymmetrical thrust-folds, symmetrical anticlines, and a superimposed normal fault conjugate system which were generated by major phases of compressive deformation during the Miocene and Pliocene periods. Seismic evidence suggests that the intensity of compressional deformation shows diminished compression from the northwest to the southeast, where a deformation front is juxtaposed to a synclinal sedimentary basin that extends offshore.

Structural analysis reveals a northeast-southwest trending antiform plunging to the southwest and tilted to the southeast at 17 to 20 degrees . This structure is confirmed by Trend Surface Analysis using a 3rd order polynomial. Miocene asymmetrical thrust-folds and Pliocene thrust-splay faults within this structure represent the most attractive traps for exploitation. However, the superimposed normal fault conjugate system control the entrapment patterns of the field with the highest production realized in upthrown blocks bounding younger Pliocene reservoirs within the antiform. Stratigraphic analysis using Top Lower Gros Morne as a Time Stratigraphic Datum suggests an onlap unconformity between the Pliocene Lower Gros Morne sands and the Upper Miocene Lower Cruse sands on a northwest southeast high in the midsection of the field.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.