MASSONAT, GERARD, and G. GUERINE, Elf Aquitaine, Pau, France, and P. RETAIL and B. CASEY, Elf Enterprise Caledonian, Aberdeen, Scotland

ABSTRACT: Oil Recovery Through a Horizontal Well in a Fractured Granitic Basement

This paper describes the geologic and reservoir approaches to optimize oil recovery in a United Kingdom field. The reservoir consists of several hundred meters of sandstones, conglomerates, siltstones, and shales sequences with poor reservoir characteristics.

Generally, the well productivity is low. Nevertheless, a vertical well has shown higher productivity coming from both the sandstones and the underlying fractured basement. Consequently, we expected that a horizontal well within the basement and intersecting the major fracture orientations could produce hydrocarbons from the overlying and adjacent accumulation with good productivity.

The fracture characterization was developed by reference to an onshore reservoir analog, and by interpretation of geophysics and well data. This field fracture model, linked to a reservoir simulation, lead to the drilling of the horizontal well through the basement in order to test this producing mechanism. The results from this horizontal well are very close to the expected simulation results.

An analysis of the fracturation (orientation, fracture density, width, and spacing of highly fractured zones) was performed in the horizontal well. This determination of the fracturation pattern, and a comparison with the former analog model and with new field-trip observations allow a better understanding for future modeling of the field.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.