Abstract: Fluid Identification and Pressure Transient Analysis in the Fractured Monterey (Using the Modular Dynamics Tester)
GRAYSON, STEPHEN, Schlumberger Wireline & Test
The highly fractured, Miocene age, Monterey formation, offshore California, is estimated by the MMS to contain over one billion barrels of remaining reserves. Quantitative wireline evaluation has traditionally been difficult in fractured reservoirs. Resistivity imaging of the Monterey using the FMI tool has provided 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, pressure build up tests can be performed on the selected fractures, allowing reservoir parameters to be revealed via pressure transient analysis. For testing the Monterey, the MDT was configured with the Inflatable Packer Module in order to straddle test fractured intervals of interest identified on the FMI image. This permitted downhole optical fluid identification, pressure tests, and multiple samples to be acquired. On a series of offshore Monterey wells, the FMI and MDT were used to identify fractures, 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 minimize gas production. Analysis of build up data provided formation pressures, permeability, and skin damage on selected fractures. Comparison of fracture permeability with the corresponding resistivity image provided a visual calibration for enhanced image interpretation. Analysis of formation pressures provided an understanding of pressure communication between different layers within the Monterey.
AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California