A scale inhibitor "precipitation" squeeze is one of the two main types of treatment for preventing downhole scale deposition; the other type is an adsorption squeeze. However, unlike for the adsorption squeeze process, the mechanism for inhibitor retention within the formation through precipitation/re-dissolution is not fully understood and it is this issue that is considered in this work. Here, our central objective is to consider a range of possible models of the precipitation squeeze process and to determine which of these are consistent with the available laboratory core flood and field data. Such models range from pure precipitation through to more complex models which couple the precipitation process with an adsorption process or with a "mechanical transport" phenomenon. The various models are explained in terms of the chemical processes which are observed. Results from two inhibitor precipitation core floods and one field squeeze treatment are presented along with the modelled inhibitor return curves. Based on certain model assumptions, our understanding of the process allows us to optimise the squeeze design of both inhibitor solution and operational parameters for extending the precipitation squeeze life time.

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