--> Abstract: Use of Gas Chromatography to Differentiate Oils in Solving Development and Production Problems in the Gulf of Mexico, by R. J. Elsinger; #90987 (1993).

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ELSINGER, ROBERT J., Humble Instruments & Services Inc., Humble, TX

ABSTRACT: Use of Gas Chromatography to Differentiate Oils in Solving Development and Production Problems in the Gulf of Mexico

In petroleum exploration, gas chromatography of crude oils has been used traditionally to identify the geologic character of the oil, and for correlating oil to source rock and oil to oil. Oil to oil correlation can also be used to answer questions associated with developing an oil field because oil within a continuous reservoir has a unique chromatographic fingerprint. The differences in the fingerprints between oils in adjacent or nearby reservoirs can be very subtle, but they are measurable. Geologists and engineers can use these differences as an aid in defining reservoir's continuity and identifying leaky casings and tubing strings.

In many oil fields in the Gulf of Mexico, it is very difficult to structurally map the extent of reservoirs because of the complex nature of the faulting. An example will be shown where chromatography was used to compare and group oils from several wells completed in the same structural sand. These groupings contributed to a revised structural interpretation and successful positioning of a new well. The chromatographic fingerprint of the oil from the new well matched the other oils in the same fault block.

Many wells in the Gulf of Mexico are completed as dual producers and may also contain several selective zones. Over time, these wells can become plumbing nightmares, with tubing string communication, leaking packers, cement failures, etc. An example will illustrate where chromatography was used to discover and quantify a tubing string communication problem in a dual completion well. The fingerprints of oil samples collected throughout the history of the well, showed when the leak was developing and when there was total communication. Laboratory mixing experiments were used to quantify the extent of the communication. A workover of the well confirmed the leak inone of the tubing strings.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.