Transport of Fine Sand From a Wellbore

Abstract

Abstract This paper presents the results of an experimental study on the transport of fine sand in the entrance region of a progressing cavity pump. The study was performed to provide additional information on the behaviour of the sand slurry flow within a heavy oil well. Tests were carried out with both glycerine and water flows, with the addition of sand in the form of slugs or as a continuous feed to form a sand slurry. Several geometries of the pump intake were used. The different flow regimes observed suggest modes of operation of heavy oil wells that may be used to better avoid sanding or shutting in of wells. These results, in addition to being useful to industry, should also inspire more theoretical studies to explain the formation of the various flow features. Introduction The flow in a heavy oil well consists of a mixture of very viscous heavy oil, gas, water, and fine sand. For these wells, sand production can be a costly problem(1). Within the pump entrance area, there is potential for the sand to choke the flow within the well ("sanding") and production equipment. Sand may form bridges or arches within the annulus of the well to reduce flow tothe pump. Sand may also restrict flow at the intake to the pump, which can result in pump damage. It is possible that the problems associated with sand production are so costly that the well does not operate within economic limits, and is subsequently shut in or abandoned. Field monitoring of solids production in heavy oil wells typically classifies sand entrance into the wellbore to be either "continuous," where a reasonably constant value of sand is produced, or "sluggery," where slugs with high sand concentrations enter the wellbore(1). This paper presents the results of a visualization study to investigate the mechanics of slurry flow in a heavy oil well in the area around the entrance of a progressing cavity pump(2, 3). The purpose of the study was to investigate the flow regimes created in the pump entrance area by changes in the flow rate and properties of the sand slurry fed into the well, and to assess the impact of each on sand removal in the area around the pump intake. Both a very viscous glycerine-sand slurry and a water-sand slurry were used in the experiments to examine the effect of fluid viscosity. The transport of sand was observed in a single liquid phase, with the sand added in slug form or as a continuous feed. The study also investigated the effect of the geometry of the pump intake region on sand removal from the area. Several interesting flow phenomena were observed, and are described herein. Experimental Arrangement and Experiments The visualization model, shown in Figure 1, examined a 1.35 m section around the pump entrance and was close in size to typical heavy oil wells in Western Canada.