Case Study: Cased-Hole Density Application, North Slope, Alaska

摘要

This paper provides a case study of the techniques used tornacquire, process, and interpret cased hole density datarncombined with logging-while-drilling (LWD) resistivity datarnfor completion decisions in a sidetrack well from the NorthrnSlope, Alaska. Density data, acquired through 3.5-in. casing,rnaugmented the openhole LWD resistivity and gamma ray datarnused to investigate possible water breakthrough and formationrnwater saturation before completing this well. The cased holerndensity data were critical to this decision because they werernnot available with LWD, could not be acquired in an openrnhole because of borehole conditions, and were necessary forrnporosity determination. Formation lithologic effects precludedrnthe use of alternative through-casing porosity measurementsrnsuch as neutron log data.rnAfter acquisition, the density data were processed tornaccount for casing and cement effects and were then comparedrnwith offset density data for quality-control purposes. Arnpetrophysical analysis was performed using this processedrndensity with the LWD resistivity and gamma ray (GR)rninformation to aid in the completion decisions. The objectivernof determining if water breakthrough had occurred was met,rnand this well was perforated and fractured accordingly. Wellrntests indicated the presence of low water cut and competitivernoil rates, which confirmed the petrophysical interpretation.rnThe ability to acquire accurate formation density data afterrncasing had been set reduced completion decision uncertainty.rnThis added another tool to the completion decision processrnwhile this field was developed.