Abstract

The drilling industry routinely encounters formations with pore pressures that are lower than anticipated. In some cases, these pore pressures require specialized treatments to control the loss of whole drilling fluid. A massive loss of whole drilling fluids, whether water-based or oil-based, can be costly, result in nonproductive time (NPT), and if encountered near potential productive zones, also result in damage to the producing capability once completion has been performed. Key wellbore data, such as actual hole size versus drilled hole size, accurate bottomhole circulating temperature (BHCT), and placement technique with optimum bottomhole assembly (BHA) for accurate placement of treatment design is critical for job success.

Placing a successful treatment for the control of whole mud losses and to minimize possible formation damage can be a complex and often expensive undertaking. Numerous solutions have been identified in the industry ranging from effective bridging or lost circulation material (LCM) incorporated in the mud to complete process solutions such as crosslinked fluid structures to ultimate cement slurries. The damage that is left as a result of the fluids pumped is a major disadvantage of most systems.

This paper presents a novel approach using a rigid setting fluid (RSF) that can be engineered to maintain a low viscosity during placement and activate by temperature to transition from a fluid to a set state almost immediately to effectively control further losses to the formation. In addition, using the right angle set (RAS) created by the exothermic reaction, the system can tolerate contamination of extraneous fluids up to 50% and still provide adequate compressive strength. Lastly, the material is soluble in acid with a predicted 99% regained permeability. A case history will be presented where the RSF treatment was used and effectively controlled, eliminating further whole mud losses to the weak formation.

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