The presence of salt structures in prospects for oil and gasexploration is, in itself, a factor that increases the probabilityof success due to favorable conditions for the hydrocarbonsgeneration and trapping. However, many operational problemssuch as stuck pipes and casing collapse have been reported bythe industry when drilling through those salt layers.Historically, in Campos Basin – Brazil, several deep wellshave been drilled through thick salt intervals. Up to the 90’,the lack of a reliable ways to predict salt behavior at hightemperatures and high differential stresses led to very highcosts and even loss of wells.In this paper we present a methodology for mud weight andcasing design and also to define the drilling strategiesemployed for drilling through thick salt layers. The numericalsimulations to evaluate the creep behavior of salt submitted tohigh differential stresses and high temperatures were donethrough the applications of an in-house finite element codedeveloped. To calibrate the model, triaxial creep tests in saltsamples were performed to evaluate and isolate reologicalproperties to represent its creep behavior under differentdifferential stresses and temperatures. It was verified thatnumerical and experimental results matched and had a fineconformity.A recent application of this methodology in a sub salt well inCampos Basin allowed us to drill the salt without a problem.Results obtained by numerical simulations were used topredict the evolution of the well closure with time for variousmud weights and analyze several alternatives of casingscapable of supporting salt creep. As a result, stuck pipe andcasing collapse were avoided and drilling costs reduced.
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