Abstract
Accurate placement of emulsions containing formulated inhibitors in the casing-tubing annulus can provide more effective and long term well treatment than the standard batch methods. This paper presents the results of experimental investigation and correlation of experimental data based on a large-scale model well constructed to simulate flow within the typical well annulus. The wellhead and bottom hole assemblies were designed to closely simulate those found in producing oil and gas fields.
Various chemicals were injected at the wellhead to flow through the annulus, to determine the role of viscosity, density, and surface tension, which were then followed by brine flush. The flow of emulsion and flush through the annulus was recorded at fixed positions and with mobile cameras. The observation and identification of the flow patterns during the treatment was made. A set of pins was inserted into the casing wall. This allowed the measurement of thickness of the emulsion coating the annular surface. The surface area coated by the emulsion was traced and measured. Downhole emulsion delivery was thus determined by performing the emulsion material balance. The amount of emulsion retained in the system is based on deposited chemical thickness, coated surface area and concentration of chemical in the annular fluids after the tests.
The results were correlated using dimensionless groups to allow extrapolation to well depths encountered in a typical oilfield production. The effectiveness of emulsion delivery and the flow patterns in the annulus were determined to strongly depend on the application type and conditions.
