Case Histories of MWD as Wireline Replacement: An Evolution of Formation Evaluation Philosophy

Abstract

ABSTRACT Since its introduction in the late 1970's, measurement while drilling (MWD) technology has evolved from an auxiliary directional drilling service to a fully integrated logging package for quantitative reservoir characterization. Many major and independent oil companies are now re-evaluating traditional formation evaluation methods, commonly utilizing MWD technology as a replacement for routine wireline logging services. Recent MWD logging case histories are presented from the Texaco operated Kilauea (Green Canyon Blocks 6 and 50) and Tick (Garden Banks Block 189) Projects from the Gulf of Mexico Flexure Trend for the purpose of evaluating their utility for quantitative reservoir characterization. Single and multiple depth of investigation resistivity, formation density, neutron porosity, and dual gamma ray MWD responses are compared and contrasted with their correlative wireline counterparts. Petrophysical evaluations are corroborated by conventional core data, borehole images, sidewall core, and production data. MWD "near/far" neutron count rate overlays were employed for qualitative evaluation of hydrocarbon type. Measurements after drilling (MAD) were recorded for indication of relative permeability and detection of moveable hydrocarbons. Comparative evaluations proved conclusively that MWD could be used as a substitute for correlative wireline logging suites where borehole size was not a limiting factor. Texaco's recent experience with MWD has evolved from that of a "last resort" application toward that of a primary logging suite for formation evaluation. This philosophical change in utilizing MWD has resulted in significant savings in rig time and associated costs. Additionally, difficult, well plans were drilled and evaluated with confidence; geopressure was safely monitored; and tops of conventionally cored intervals were selected. Geological interpretations and quality operational decisions were made before the wells reached total depth, creating a more efficient business process.