Although operators have deployed particulate diverter technology widely, there is space for improvement on the underlying mechanisms, physics and controlling parameters for a successful diversion. One of the missing factors during the application of solid particulate diverters is the transport of the particle slurry from surface to downhole. The aim of this work is to identify the operational parameters dictating the integrity of a particle slug and optimize these critical parameters to ensure efficient diverter slurry transport and fluid diversion efficiency and effectivenes.
Particulate system properties such as concentration and particle size ratio are usually selected based on downhole plugging and diversion goals (Shahri et. al., 2017). However, these properties might change during slurry displacement due to particle dispersion and interface instability. In order to identify parameters dictating slurry integrity, coupled computational fluid dynamics (CFD) and discrete element method (DEM) are used to simulate particulate system transportation and plugging. The CFD-DEM model is used to determine characteristics of the particulate slurry to ensure no particle dispersion, settling and to maintain particle slug integrity when traveling within the wellbore.
By honoring interactions between particles, slurry fluid and wellbore schematics, we have developed an analytical model to optimize the operational parameters required for an efficient diverter slurry transport. This includes adjusting displacement rates during diverter injection and determining and adding required volumes of spacer to ensure integrity of the diversion pill. The proposed analytical engine has been verified against numerical simulations and experimental data. Both the numerical and analytical analysis show that the extent and growth of the disturbing and mixing zone during the slurry transport is dictated by fluid density, viscosity, flow rate and travel distance. In addition to the diffusion related dispersion, interface instabilities may influence the mixture of the displaced fluids and raise the turbulent effect along the contact between different fluids, which could further promote the dispersion and damage the integrity of the designed particle slug.
Based on these learnings, different field guidelines are developed for determining the optimum displacement rate and required spacer volume under different operational conditions. As proven from our study, it is operationally feasible to keep the integrity of the particle slug to ensure efficient plugging, pressure build-up and diversion every time and without uncertainty. The applications of the proposed design methodologies for different field case studies are also presented and discussed.
This work presents a new model and workflow to deliver the particulate slurry in batch mode to targeted sealing locations. The design workflow better enables us to mitigate particle dispersion and achieve efficient particulate slurry transport. Depending on the reservoir and wellbore condition, operational guidelines can be customized and optimized to maintain the integrity of slurry while being transported downhole and improve the quality of the sealing structure.