Deviated well sections are common in modern well construction. In mature areas like the North Sea region, practically all producers or injector wells will have highly deviated sections. These wells must be drilled and completed in an optimal manner with respect to drill time, cost, risk and functionality. Most cuttings transport and hydraulic models are developed based on tests with model fluids and often in small diameter test sections. Hole cleaning and hydraulics with field fluids are different than the properties considered with most model fluids. Furthermore, results from small diameter tests with model fluids may not always be relevant for, nor scalable to, field applications due to time, length and other scales. Hence, there is a need for studies in controlled laboratory environments with various field application designed drilling fluids to improve engineering models and practices.This paper presents results from laboratory tests using field applied fluids. The drilling fluids have similar density and viscosity within the relevant shear rate range applied during drilling operations and in the tests. One of the fluids is oil-based and the other one is an inhibitive water-based drilling fluid.The experiments have been performed in a flow loop that consists of a 10 meters long test section with 2" OD freely rotating steel drill string inside a 4" ID wellbore made of cement. Sand particles were injected while circulating the drilling fluids through the test section. Experiments were performed at three wellbore inclinations: 48, 60 and 90 degrees from vertical. The applied flow loop dimensions are designed so that the results are scalable to field applications; especially for the 12,25" and 8,5" sections. The selected setup is designed to provide correct shear rate ranges and equal Reynolds number to the field application when the same fluids are applied.Results show that hole cleaning abilities of the tested fluids vary significantly with well angle, drill string rotation and flow rate. Results support field experience showing that the typical oil-based fluid in most conditions is more efficient for hole cleaning than the similar viscosity water-based fluid. The results show the effect of cuttings transport efficiency as function of hydraulic frictional pressure drop, demonstrating methods to achieve more optimal hydraulic design in the tested conditions.

Cuttings Transport With Oil- and Water-Based Drilling Fluids

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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