Application of Real-Time Resistivity and Annular Pressure Datain Reducing Lost-Circulation Events

摘要

Lost circulation is one of the major risks associated withdrilling in a deepwater or subsalt environment. The downtimespent regaining circulation and the associated well controlissues increase the already high operating costs and introducecritical safety concerns. This paper illustrates how formationresistivity and annular pressure measurements, combined withtime-lapse logging data, can be used to determine a moreaccurate fracture pressure, enabling cost-effective real-timedrilling decisions.Two examples are presented to demonstrate that ananalysis of the resistivity and pressure data, viewed in bothtime and depth domains, contributes to a better understandingof fracture behavior. Lost-circulation problems occurring inweak formations far below the casing shoe can be located withlogging data. Additional information enables relevant-timedrilling decisions such as selecting proper mud weight,spotting fluids, and optimizing cementing programs.The first example shows how abnormal real-timeresistivity readings, suggesting the initiation of fractures, wereconfirmed with time-lapse measurements made while trippingout of the hole. The real-time resistivity data showed elevatedresistivities suggesting fracture growth. This interpretationwas confirmed with time-lapse measurements. The analysisprovided the location of the problem zone, the formation type,and the wellbore pressure activating the fractures. In thesecond example, a minor water kick prompted the acquisitionof a real-time openhole leakoff test followed by real-timeresistivity logging. The additional information provided abetter understanding of the initiated fracture characteristicsand enabled drilling the section to total depth withoutmud losses.