In oil and gas drilling, cuttings transport related problems are a major contributor to well downtime and costs. As a result, solutions to these problems have been extensively researched over the years, both experimentally and through simulation. Numerous review articles exist, summarizing not only the research history but also the qualitative effect of individual case parameters such as e.g. pump flow rate, pipe rotation, rate of penetration on cuttings transport. However, comparing different studies is challenging, as there is no common reference basis defined in the form of typical and representative set of case parameters. In order to develop relevant and accurate cutting transport models, it is critical that both experiments and models are targeting flow cases, which are relevant for respective drilling operations. By developing a clear understanding of the industrial parameter space, as well as establishing critical benchmarks, the development of models and corresponding laboratory experiments will become much easier. Other industries have established such benchmarks (e.g. the "NREL offshore 5-MW baseline wind turbine" in wind power research), providing a standardized set of case parameters and profiles, readily available for use to researchers worldwide and resulting in straightforward benchmark and validation as well as faster project set-up and definition. For application to modeling of cuttings transport phenomena, we propose a methodology how to derive a well-defined and standardized set of geometrical, operational, and environmental case parameters describing various working points of actual drilling operations and procedures as well as simplified problems. The relevance and application of standard parameters is briefly discussed in the light of modeling, both experimentally and through simulations.

Summary In oil and gas drilling, cuttings-transport-related problems are a major contributor to well downtime and costs. As a result, solutions to these problems have been extensively researched over the years, both experimentally and through simulation. Numerous review articles exist, summarizing not only the research history but also the qualitative effect of individual case parameters such as pump-flow rate, pipe rotation, and rate of penetration (ROP) on cuttings transport. However, comparing different studies is challenging because there is no common reference defined in the form of a typical and representative set of case parameters. To develop relevant and accurate cutting-transport models, it is critical that both experiments and models are targeting flow cases relevant for respective drilling operations. Development of a clear understanding of the industrial-parameter space, as well as establishing benchmarks, will help achieve a more-concerted effort in development of models and corresponding laboratory experiments. Other industries have established research benchmarks, such as the “NREL offshore 5-MW baseline wind turbine” (Jonkman et al. 2009) in wind-power research, providing a standardized set of case parameters and profiles, readily available for use to researchers worldwide, and resulting in straightforward benchmarking and validation as well as faster establishment of projects. For application to the modeling of cuttings-transport phenomena, we propose a methodology for deriving a well-defined and standardized set of geometrical, operational, and environmental case parameters describing various operating points of drilling operations and procedures as well as simplified problems. The methodology is exemplified with an 8.5-in.-section drilling-ahead use case with aggregated wellbore data from the Norwegian Petroleum Directorate (NPD). The relevance and application of the derived parameters are briefly discussed in light of modeling, both experimentally and through simulations. Applying this methodology before any cuttings-transport study may enable a better definition of industry-relevant case parameters. In Part 2, we will apply and discuss the derived parameter sets in the context of nondimensional numbers for assessment of scalability.

Particle dynamics within Newtonian and viscoelastic shear thinning flows were investigated with a self-confined cloud of particles around an obstacle. Water and three aqueous Poly-Anionic Cellulose (PAC) solutions were test fluids. An experimental study of an upward vertical pipe was carried out using particle image velocimetry (PIV) techniques to measure the particle and liquid velocity profiles. The fluidized cloud height was measured for better assessing rheological and particle loading effects on particle interactions within liquid flows. It was observed that the dynamics of particles were closely associated with local shear rate, fluid rheology and particle loading. Additionally, it was noted that the slip velocity of particles was relative to the surrounding liquid and was high in regions with a high shear rate and depended significantly on the liquid rheological parameters. The experimental findings were compared against three-dimensional numerical CFD simulations. In the case of particle dynamics in the water sample, it was noted that the simulation results were comparable to the experimental observations. However, for PAC solutions, particles were completely flushed out from the computational domain. This was considered a consequence of inadequate drag and settling velocity formulation within the CFD model. These shortcomings of the drag model were rendered, as Newtonian drag laws were applied to a non-Newtonian fluid, and only used background shear rates of the fluid flow field in estimating the local viscosity experienced by these particles.

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