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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 988

Last Page: 988

Title: Prediction of Lateral Seal Capacity from Core Data: ABSTRACT

Author(s): Tim T. Schowalter

Article Type: Meeting abstract


Mystery Reef field produces oil from a porous stromatoporoid, limestone reef buildup. Only a small part of the total reef porosity is filled with oil. The maximum oil column in the field is 120 ft (37 m). The upper half of the column is sealed by marine shales that filled in depositional topography. The lower half of the oil column is sealed by the reservoir-equivalent fore-reef facies.

Lateral seal capacity, in terms of vertical oil column, were calculated from capillary pressure curves for five wells updip from the field. The seal capacity for the lowest displacement pressure rock in each well ranged from 10 to 150 ft (3 to 46 m). This spread of values for the updip reservoir equivalent facies at Mystery Reef field suggests that the prediction of lateral seals from core samples can provide only a very rough approximation of seal capacity in heterogenous carbonate rocks.

Two of the five wells studied updip from the field were oil stained in the reservoir equivalent horizon. Calculations of the minimum oil column necessary to explain the oil shows in these rocks range from 10 to 84 ft (3 to 26 m). Seal capacity of the higher displacement pressure oil stained rocks ranges from 60 to 84 ft (18 to 26 m). These values are similar to the oil column known to be trapped by the sampled fore-reef facies. Estimates of lateral seal capacity from core data should put the greatest emphasis on the oil stained samples with the highest seal capacity.

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