The control of inorganic scale deposition within production wells by deployment of scale squeeze treatments is a well-established method for both onshore and offshore production wells.
Over the past 25 years the science of designing and optimising these treatments has advanced significantly with a better understanding of chemical/rock interaction, more effective modelling software to design the treatments and improved analysis methods for the determination of returning residual concentrations.
Scale squeeze treatments have in general been designed to treat between 6 to 12 months of water production before either the production layer or bulk produced water composition falls below minimum inhibitor concentration (MIC). In this paper examples of the process followed to design treatments for 24 months produced water for three offshore fields (North Sea, West Africa and Middle East) are outlined.
Factors that have influenced the change from 12 to 24 months squeeze treatments include changing MIC values, rising operation expenditure related to subsea vs platform deployment costs and in all cases assessing total operational cost vs simply chemical costs alone.
This paper presents the field treatment designs from 4 case study fields, changing MIC values based on produced water composition which impacts chemical volumes required. The balance between cost of operation to deploy the chemical treatments to subsea vs platform wells are discussed. The implication of deferred oil associated with delayed production during pumping and post squeeze well clean-up was also considered in the design process for these wells. These case studies describe squeeze treatments which in certain wells treat over 25,000,000 bbls to MIC.
The paper outlines the elements of the process that should be considered/reviewed when making the decision to change from the conventional 12 months to 24 months squeeze treatment. Designs and field results from three oil producing basins, each with different cost drivers, have been used to illustrate how it is possible to maintain effective scale management through the life cycle of these production wells.