--> Abstract: Evaluation of Oil Bearing Fractured Reservoirs (Type I) Using Data Acquired While Drilling, by B. Douglas Bearinger; #90039 (2005)

Datapages, Inc.Print this page

Evaluation of Oil Bearing Fractured Reservoirs (Type I) Using Data Acquired While Drilling

B. Douglas Bearinger
Nexen Petroleum International Ltd, Calgary, AB

Fractured reservoirs that lack matrix porosity are very difficult to evaluate with conventional petrophysical analysis. They are more readily characterized by the hydrocarbons released during the drilling process. The quantity of hydrocarbon released is mostly indicative of the amount of storage (porosity) but is also influenced by the interconnectivity and conductivity of the fracture network. Quantification of the movement of fluids between the wellbore and the surrounding fractured reservoir provides an indication of the production potential of wells.

Gaslogging provides a continuous record of hydrocarbons released from the reservoir into the circulating drill fluid. Gas component ratios can be used to characterize the hydrocarbon type and the reservoir quality. Oil stain and fluorescence observed in drill cuttings provide further indications of hydrocarbon saturation and reservoir quality.

Continuously recorded fluid loss/gain information allows accurate location of conductive fractures. A loss index (LI) can be calculated to estimate the productivity or injectivity of a well.

Image logs provide rock fabric information and help characterize the fracture network. Fracture intensities and apertures can also be used to calculate fracture porosity and estimate well productivity.

Conventional openhole log suites can be used to interpret lithology/compositional changes, lithologic contacts, and to evaluate brecciated fault zones and diagenetically altered zones where matrix porosity can be developed.

Examples from a fractured granitic Basement reservoir located in Yemen and being developed by Nexen International will be used to illustrate data and techniques that can be used to evaluate a type I fractured reservoir.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005