High rate of gas production from a well may result in brine production from different formations. When incompatible brines with different degree of saturation are mixed, precipitation of the salt could plug the well. Evaluation of openhole section was performed on a well in a gas field in Iran to check the well productivity. Unexpectedly, the tool was blocked a few feet below the casing shoe indicating the reason for production reduction. Attempts to remove scale deposition were unsuccessful and motivated comprehensive review of potential reasons to identify the properties of precipitated mineral. Crystal overgrowth of sulfate salt was considered to be the most likely mechanism, because the production zone was located in Nar formation which was mainly composed of anhydrite.

A comprehensive investigation was conducted in order to verify the type of bridged section. In-situ chemical conditions were identified based on general geological data, rock formation, rock types and brine sampling in reservoir rock. In such case at each production rate a different volume of brine was observed. Therefore, aqueous environment, ions and other in-situ conditions were modeled. The model was constructed using dynamic simulation software. Based on this model salt precipitation was reproduced confirming in-situ scaling problem. A prototype was developed to disperse this material based on previous laboratory experiments. Quantity and volume of additives for well treatment and scale removal were calculated accordingly. A scheduled production plan was proposed to identify the potential problems and appropriate strategy at each production rate. Study of this case in terms of site investigation, problem definition, and solution identification could accumulate valuable knowledge to quickly solve the problems in similar cases. In addition, presented simulation method would be the most economical method for scaling prevention and production optimization.

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