<p>Drilling and completion fluids (mud) are complex suspensions which typically contain weight material particles (such as barite) for increased density and clay particles to increase viscosity and providing yield stress. In a static column of fluid, barite will inevitably sediment. &nbsp;The density of the sedimented mud column gradually increases from fluid at the top to a compact, and possible gas tight solid at the bottom. The separation mechanism in different sediment phases is very complex, and there is a need for detailed and systematic fluid experiments in order to fully understand the properties of settled barite. Wave velocity, commonly used to characterize the borehole condition, could be used to separate and possible identify the different sediment phases in the mud column, as well as the contact between the solid barite and cement.</p><p>The current study investigates the evolution of P-wave velocity during the settling process. A laboratory setup which allows the fluid to escape in a control manner using a quizix pump was used to resemble the sedimentation process of three different fluids. Two synthetic fluids (bentonite and KCl based) and one commercial polymer-based fluid. &nbsp;For all fluids, a decrease in the P-wave velocity was observed with compaction of the sample. A decrease of velocity could either be caused by a decrease in bulk modulus or due to an increase of the density. However, in this case, a significant increase in the density has most likely overridden the slight increase observed the bulk modulus during compaction which lead to decrease in velocity of the compacting mud. The observation is modelled (qualitatively) with very simple rock physics model and show somewhat similar trend.</p>

Evolution of P-Wave Velocity in Settling Drilling Fluids

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

OMAE 2021

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