A Joint Industry Project to Assess Circulating Temperatures in Deepwater Wells

Abstract

Abstract Drilling oil wells offshore in water depths exceeding 1000 m is not uncommon in many parts of the world. These conditions present a number of challenges for successfully cementing even the shallowest strings. A major challenge is predicting the temperature to which the cementing fluid(s) will be submitted during and after placement so that laboratory procedures can best simulate the actual situation. What sounds like an easy task for the majority of land wells or offshore wells with shallow water depths turns out to be much more difficult for deepwater wells. This is due in particular to inverse temperature gradients across the sea and convective thermal exchanges between the sea and the fluids in the riser and/or drill pipe. To better understand the phenomena involved, a series of temperature measurements was made as part of a joint industry project. The primary objective of these measurements was specifically to monitor the cooling effect of the sea through the measurement of the fluid temperature at the mud line depth. All temperature data were measured by a sensor deployed inside the bottomhole assembly while circulating or drilling. This method was selected for its low cost and lack of interference with drilling operations. Data were collected in the Gulf of Mexico, Brazil, Indonesia and West Africa with an average water depth of 1200 m. A summary of the temperature measurements is presented. Comparison is also made with the predictions of a numerical simulator. The detailed interpretation of these data gathered pinpoints the importance of correctly accounting for the exact temperature profile in the sea as well as the velocity of sea currents versus depth. The outcome of this study helps to define better cement slurry testing procedures for deepwater applications. As a result the technology that is best suited for these specific conditions can be selected on a more rigorous technical basis.