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Abstract In order to understand better the effects of lithology, an anomalous log from a 2-MHz Logging While Drilling propagation resistivity tool is compared to a log from a wireline dual induction - SFL Spherically Focussed Tool. The C-sand in the Kuparuk River Field contains the minerals siderite and glauconite which exhibit atypical dielectric properties. For several wells in the Kuparuk River Field where both the 2-MHz and wireline logs were obtained, the agreement is good after dielectric processing. However in this well, the 2-MHz tool reads differently from the wireline induction tool. In this well, the 2-MHz tool had been run during a washdown trip rather than while drilling. A combination of laboratory core characterization and forward modeling is used to reconcile the differences between the two logs. The 2-MHz and induction tool responses were modeled based on the laboratory results. The remaining differences between the 2-MHz and induction resistivity were caused by invasion effects in the washdown mode. Introduction The Kuparuk River Field is located near the western margin of Prudhoe Bay on the North Slope of Alaska. The field produces from two distinct intervals; the upper unit is the C-sand, and the lower unit is the A-sand. The C-sand contains local concentrations of siderite and glauconite, and the A-sand contains ankerite. Until recently, wireline induction logging has been used exclusively as the resistivity component of the logging suite. Because of the higher well angles and the desire to reduce rig costs, the use of logging-while-drilling (LWD) has increased. The CDR Compensated Dual Resistivity tool provides a shallow borehole compensated, 2 MHz, propagation resistivity measurement while drilling. The Phasor-Induction tool provides a deep-penetration, 20-kHz, induction resistivity measurement on a wireline. The CDR tool is expected to obtain a Rt because its measurement while drilling precedes deep invasion; while the Phasor-Induction tool is expected to obtain Rt because its region of investigation is sufficiently deep to sense beyond deep invasion. P. 155^ |
