Schlumberger

Technical Paper: Application of Real-Time Resistivity and Annular Pressure Data in Reducing Lost-Circulation Events

Society: SPE
Paper Number: 79847
Presentation Date: 2003
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Abstract

Lost circulation is one of the major risks associated with drilling in a deepwater or subsalt environment. The downtime spent regaining circulation and the associated well control issues increase the already high operating costs and introduce critical safety concerns. This paper illustrates how formation resistivity and annular pressure measurements, combined with time-lapse logging data, can be used to determine a more accurate fracture pressure, enabling cost-effective real-time drilling decisions.

Two examples are presented to demonstrate that an analysis of the resistivity and pressure data, viewed in both time and depth domains, contributes to a better understanding of fracture behavior. Lost-circulation problems occurring in weak formations far below the casing shoe can be located with logging data. Additional information enables relevant-time drilling decisions such as selecting proper mud weight, spotting fluids, and optimizing cementing programs.

The first example shows how abnormal real-time resistivity readings, suggesting the initiation of fractures, were confirmed with time-lapse measurements made while tripping out of the hole. The real-time resistivity data showed elevated resistivities suggesting fracture growth. This interpretation was confirmed with time-lapse measurements. The analysis provided the location of the problem zone, the formation type, and the wellbore pressure activating the fractures. In the second example, a minor water kick prompted the acquisition of a real-time openhole leakoff test followed by real-time resistivity logging. The additional information provided a better understanding of the initiated fracture characteristics and enabled drilling the section to total depth without mud losses.

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