Exxon Production Research Company

William E Kline

Yuh-Hwang Tsao

Eugene A Sikirica

Marco Rasi

Michele M Thomas

Albert T Wang

Richard C Haut

Mark E Jordan

The current invention is a method for modeling the probability of a drill string becoming stuck within a given time frame and a method for applying the model to a well being drilled to reduce the probability of sticking. The model is constructed by performing canonical discriminant analysis on engineering parameters derived from observations taken in historical wells and creating a canonical space with the resulting canonical functions. Posterior probabilities of sticking are then calculated from the historical observations and mapped into the canonical space. To apply the model to a particular well being drilled, the values of the previously derived engineering parameters are calculated from observations in the well being drilled, multiplied by their corresponding canonical coefficients, and summed to obtain a canonical point representation for drilling in that well. This canonical point representation is then mapped into the canonical space to obtain the probability of sticking. The probability of sticking is then compared to probabilities experienced in the past under similar drilling conditions. If the probability of sticking in the well being drilled is found to be higher than average historical probability, it can be reduced by implementing remedial measures that are suggested by simple inspection of the values of the engineering parameters.

Method to combine statistical and engineering techniques for stuck pipe

A method for logging a cased well to determine the quantity and location of any barite weighted drilling fluid in the annulus between the casing and the wall of the wellbore. A tool assembly having a neutron generator and a gamma scintillation detector is used to log the zone of interest. The neutrons introduced into the well by the neutron generator convert a portion of the barium-138 in the drilling fluid to barium-137m. The magnitude of the gamma photon peak charactristic of the decayof barium-137 is used to identify the quantity of drilling fluid present in the annulus as a function of depth. This method is especially useful identifying the existence of channels in a cemented wellbore annulus.

Method for detecting drilling fluid in the annulus of a cased wellbore

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Houston, TX, United States of America

William E Kline