Abstract
The fractured Monterey formation of offshore California is estimated by the MMS to contain over one billion barrels of remaining reserves. Quantitative wireline evaluation in fractured reservoirs had been difficult in the past. Resistivity imaging using the FMI tool now provides the clarity to identify, orient, and quantify individual fractures. And recently, with the addition of the Modular Formation Dynamics Tester (MDT) tool, the fluid content of selected fractures can be positively identified while the tool is downhole. In addition, transient pressure analysis can be performed to reveal critical reservoir parameters. On a series of offshore Monterey wells, the FMI and MDT were used to identify and test fractures. The MDT was configured with the Dual Packer module in order to straddle-test fractured intervals selected from the FMI image. Tests were conducted to identify the fluid contained in the fractures, locate the reservoir gas cap, acquire pressure data, and take fluid samples. Perforations were confidently selected in the zones with the best quality fractures to maximize oil and to minimize gas production. Analysis of the buildup data provided formation pressure, permeability, and skin damage information. Comparisons of the fracture permeability with the corresponding resistivity image gave a visual calibration for enhanced image interpretation. Analysis of the formation pressures also provided an understanding of the hydraulic communication between different layers within the Monterey.
