Obtaining Porosity and Density in Cased Holes for Formation Evaluation in Nigeria
Mohammed Doghmi1, Parijat Mukerji1, Luca Zanichelli2, and Francesco Zanin2
1 Schlumberger Oilfield Services, PortHarcourt, Nigeria
2 Nigeria Agip Oil Company Ltd, Port-Harcourt, Nigeria
When drilling new wells, operators often encounter conditions that make openhole logging difficult. Borehole stability issues dictate changes in plan and sometimes require the section to be cased before acquiring open hole
data. To meet the challenge of obtaining formation evaluation data in cased holes, a new suite of services has been developed to offer operators an alternative to open
hole
logging that presents unacceptable risks. Cased
hole
logs can be used to obtain formation evaluation information or to complement logs acquired while drilling. In areas where open
hole
logging is difficult, preplanning for cased
hole
logging operations can save time and costs.
This paper presents a field example demonstrating the use of these new services in a Niger Delta well that was cased before open hole
logs were obtained. The logging program included standard devices to evaluate cement quality, and density and porosity tools to evaluate the formation. The operation was executed without problems. The porosity and density logs obtained behind casing closely matched the openhole logs from overlapping intervals and other offset wells. Logging while drilling
resistivity and gamma ray measurements were combined with the cased
hole
logs to perform a complete evaluation in a well section where other alternatives did not exist.