Ronald J. Hill1,
Lloyd M. Wenger2
(1) Exxon Production Research Co, Houston, TX
(2) Exxon Exploration Company, Houston, TX
Abstract: Reservoir geochemistry of Tertiary and Cretaceous hydrocarbon systems at Grand Isle 16, Offshore Louisiana: Impact on production and development strategies
The Grand Isle 16 Field, located offshore Louisiana in the northern Gulf of Mexico, is in the mature stages of oil and gas production with 370 wells drilled from 20 platforms. To date, more than 350 MBO and 665 GCF gas have been produced and substantial reserves remain to be exploited. Optimizing future development depends on understanding the complete hydrocarbon system (source, maturation, migration, emplacement and alteration of hydrocarbons). Within this framework, field and reservoir-scale processes can then be evaluated to refine production strategies.
Hydrocarbons from the Grand Isle area are reservoired in Miocene sands on the flanks of salt domes along the Terrebonne Trough Fault. Detailed geochemical analyses on approximately 90 liquid and 40 gas samples from various reservoir sands in 50 different wells indicate two distinct petroleum systems originating from Cretaceous marine and from Tertiary marine source rocks. Reservoirs have been selectively filled with either Cretaceous or Tertiary-sourced hydrocarbons, and occasionally with mixtures, as a result of their connectivity to trough and salt dome fault systems.
Variations in hydrocarbon source type and thermal maturity suggest distinct reservoir compartments at Grand Isle 16. Superimposed on differences due to source and maturity, more subtle variations in geochemical signature suggest migration effects and/or post-emplacement alteration of hydrocarbons within individual reservoirs. These subtle variations, elucidated by high-resolution geochemical techniques, have been used in conjunction with engineering, geophysical and geologic data to assess reservoir compartmentalization in the Grand Isle 16 Field. In addition, geochemical effects of migration-fractionation and post-emplacement processes have implications for the prediction of up-dip and down-dip fluid types and quality.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana