ARCO's High Island 24L field, located in the Texas State waters of the Gulf of Mexico, was discovered in 1967. It had produced 320 billion cubic feet of gas and 3.0 million barrels of oil by 1986. An engineering field study completed in 1986 showed the field to be declining to the point of unprofitability within 3 years. The study found the reservoir maps to have three basic problems: volumetric reserve calculations did not equal reserves produced, hydrocarbon-water contacts were inconsistent between wells thought to be in communication, and ultimate recoveries could not be accurately calculated. Attempts to remap the field with the existing 2D seismic data base and well logs proved unsuccessful.

In 1986 a 3D seismic survey was acquired and the field was remapped in 1987, starting with the key producing horizons. Integration of detailed well log correlations tied to the dense grid of 3D seismic allowed construction of accurate reservoir maps. These helped solve the engineering problems by more accurately defining the configuration of the reservoirs, closely matching volumetrics and fluid contacts as well as defining new extension opportunities. The 3D seismic survey and its products along with engineering modifications and operations cost containment resulted in the extension of the fields economic life by at least 8 years. As more wells are drilled and current explorationists work with the data, additional reserves are being found.

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