Thermal Stability And Application Of Emulsion Composed Blocking Agents For Steamflooding
Authors: Decker A.M. , Flock D.L. 
Published: March 2010

The investigation into mobility control and blocking agents to improve steamflood conformance has been of ongoing interest. This paper examines the thermal stability and application of oil-in-water macroemulsions to block high permeability channels created by steam injection.

The stability of 5% (by volume) Primrose and Lloydminster heavy oil-in-water emulsion was screened using both an anionic (Vista 250) and a nonionic (Triton X-100) surfactant. Surfactants were used in active concentrations of 25 to 5000 ppm to create the emulsions. Visual observations of the droplet character and the emulsion pH behaviour at different surfactant concentrations, over cure temperatures of 25 °C to 225 °C. were the criteria used to determine stability. Results of this work indicate the Vista 250 was superior to the Triton X-100 with respect to maintaining emulsion stability at high temperatures. The optimal surfactant concentration for creating 5% oil-in-water emulsions and maintaining their stability was found to be in the range of 50 to 300 ppm jar the surfactants used here.

Recovery and steamflood behaviour were observed in an unscaled linear model containing an oil saturated single size sand. Comparative results using a heterogeneous model containing two parallel oil saturated sand beds of different permeabilities show early breakthrough and reduced recovery due to steam channelling. Externally prepared emulsion (5% oil content. 100 ppm Vista 250) was then injected to block the more permeable channels.

Blockage was tested using the emulsion injected as a slug followed by steam and with the emulsion co-injected with steam. During slug injection the emulsion was injected at a constant pressure with a permeability reduction on the order of 90% inferred from a change in flow rate data, Emulsion slug injection was more effective with respect to improved blocking and recovery than was the co-injection of emulsion and steam for both heavy oils.

The strategy behind this research was to examine from a mechanistic standpoint if the application of a stable heavy oil emulsion as a high temperature blocking agent would result in improved oil recovery in an unsealed physical model- No attempt was made to assess the economic viability of the process for implementation in the field. Laboratory assessment of the process for field implementation would require a scaled physical model. Currently, the integration of scaled emulsion criteria with scaled reservoir criteria for physical and numerical simulation poses a challenging problem.

The authors believe this process would warrant further investigation for potential application to a heavy oil reservoir with a bottom water zone as well as stratified or heterogeneous reservoirs.

Introduction

In the application of steam injection to heterogeneous reservoir there is a tendency for steam and steam condensate to channel through high-permeability zones, thus leaving a significant amount of oil unrecovered. Many techniques have been proposed from controlled permeability reduction to outright plugging of channel zones through the use of blocking agents(1,2). However, to be successful the blocking agent must withstand the harsh environment associated with hightemperature steamflooding.

The use of oil-in-water macroemulsions as the blocking agent for steamflood application is examined here.