| Popis: |
Drilling and completion fluids (muds) are complex suspensions that typically contain weight material (such as barite) to increase the density, and clay particles to increase the viscosity and provide yield stress. In a static column of fluid, barite will inevitably settle. The density of the mud column gradually increases, from free fluid at the top to a compact, and possible gas tight solid at the bottom. The separation mechanism into different phases is complex, thus detailed, systematic fluid experiments is needed to fully understand the properties of settled barite. Wave velocity, commonly used to determine the condition of the borehole (and annulus), could be used to characterize, and possibly identify the different sediment phases in a mud column. The current study investigates the evolution of acoustic wave velocity during compaction/gravity separation of mud. A laboratory setup which allows for a controlled drainage of fluid was used to resemble the sedimentation process. The study was performed on three drilling fluids: two synthetic and one commercial polymer, and three compacted barite samples using two test procedures. The first procedure focuses on investigating acoustic properties during settling. The second procedure was used to investigate the behavior of compacted barite. The result shows a decrease in the wave velocity during settling, whereas increase in the wave velocity in consolidated barite with compaction. The increase or decrease of velocity with compaction can be explained by the relative changes of modulus/stiffness and density of the studied material. |
