Peter K. Currie

Filtration of micron-sized particles in granular media revealed by x-ray computed tomography

We investigate the deep-bed filtration of micron-sized hematite particles suspended in distilled water during flow in siliceous granular porous media, where particle retention is mostly due to surface (van der Waals and electrostatic) interactions. We show that x-ray computed tomography enables three-dimensional images of the filtration process to be generated. The one-dimensional filtrate concentration profiles obtained by averaging the images over sections perpendicular to the flow direction are rapidly decaying functions of the distance from the porous medium inlet and slide upward in the course of time, consistently with the filtration model presented by Herzig et al. [Ind. Eng. Chem. 62, 8 (1970)]. Finally, the filtration coefficient is found to decrease rapidly as a function of time: This indicates that the attractive interaction responsible for the retention of the hematite particles is strongly attenuated as the particles accumulate of the pore surfaces.

Deep-Bed filtration under multiple particle-capture mechanisms

This paper (SPE 98623) was accepted for presentation at the International Symposium and Exhibition on Formation Damage Control, Lafayette, Louisiana, 15–17 February 2006, and revised for publication. Original manuscript received for review 24 October 2005. Revised manuscript received for review 1 March 2009. Paper peer approved 21 March 2009. Summary Severe injectivity decline during seawater injection and producedwater reinjection is a serious problem in offshore waterflood projects. The permeability impairment occurs because of the capture of particles from injected water by the rock, both internally in the pores and externally in a filter cake. The reliable modeling-based prediction of injectivity decline is important for injected-watertreatment design and management (injection of seawater or produced water, water filtering, etc.). The classical deep-bed filtration model includes a single overall description of particle capture. During laboratory or field data interpretation using this model, it is usually assumed that several simultaneously occurring capture mechanisms are represented in the model by a single overall mechanism. The filtration coefficient, obtained by fitting the model to the laboratory or field data, represents the total kinetics of the particle capture. The purpose of this study is to justify this approach of using an aggregated single filtration coefficient. A multiple-retention deep-bed filtration model needs to describe several simultaneous capture mechanisms. The kinetics of the different capture mechanisms can differ from one another by several orders of magnitude. This greatly affects the particle propagation in natural reservoirs and the resulting formation damage. In this study, a model for deep-bed filtration taking into account multiple particle-retention mechanisms is discussed. It is proven that the multicapture model can be reduced to a single-capture-mechanism deep-bed filtration model. The method for determination of the capture kinetics for all individual capture processes from the breakthrough curve is discussed. As an example, the complete characterization of filtration with monolayer and multilayer deposition of iron oxide colloids is performed using particle-breakthrough curves from coreflooding.

Modelling the gas well liquid loading process

Liquid loading is a serious problem in maturing gas fields. Analysis shows that these wells can operate at two different rates, a stable rate at which full production is taking place and a lower metastable rate at which liquid loading affects production. A model was constructed that enhances understanding of the process of water buildup and drainage in gas wells. A metastable flow rate occurs when the water-reinjection and water-coproduction rates are equal and the water-column height stabilizes.

Reduction of Oil Droplet Breakup in a Choke

Abstract This paper reports on experimental work focused on modifying choke design with the aim of reducing oil droplet break-up in the choke in high water-cut production wells. Producing oil under such conditions, with the oil dispersed in the produced water, leads to severe break-up of the dispersed oil droplets. This break-up is caused by high energy dissipation in the choke. Previous work carried out in Delft indicated that, under identical process circumstances (tubing diameter, flow-rate, pressure drop, oil type and concentration), the break-up process is significantly influenced by the choke geometry. In this work we discuss possible ways of modifying the choke geometry to reduce droplet break-up. Three model chokes were tested in the laboratory: an orifice, a small choke consisting of 7 parallel tubes and a larger choke consisting of 13 parallel tubes. These chokes were tested at identical flow rates and with the same pressure drop across the chokes. The larger model choke was the superior one in the sense that in this device the least break-up of oil droplets took place. In the small model choke more break-up occurred, while the most severe break-up was observed for the circular orifice. A general conclusion of the investigation is that the intensity of the break-up process occurring in the (model) choke can be considerably reduced by adaptation of the choke design. A choke design based on parallel tubes gives opportunities for improving the choke performance with regard to oil droplet break-up, while still making it possible to vary and control the volume flow-rate as with a conventional choke. This investigation suggests that it will be possible to construct chokes with improved characteristics with regard to oil-droplet break-up in high water-cut wells. This will result in easier separation and less emulsion-forming downstream of the choke.