Abstract

Various sized bridging materials (SBMs) such as ultra-fine, fine, medium and coarse grade SBMs are frequently used in drill-in fluid formulations to improve drilling fluid properties, enhance mudcake quality and reduce near wellbore formation damage. The mechanical properties, especially the material toughness of the SBMs play an important role in fulfilling these functional tasks. Weak and easily disintegrating SBMs are unable to maintain the functional capability of drill-in fluid due to a major change in the planned particle size distribution in the fluid. Hence, drill-in fluid containing rapidly degrading SBMs shows poor performance while drilling. This highlights the need for selection of very tough and high strength SBMs to design superior drill-in fluid for non-damaging drilling operation in the pay zone. However, the industry lacks a suitable method for screening, testing, evaluation, quality control and quality assurance of SBM products to select the best and reject the worst and the inferior. Hence, there is a need of development of a quick and reliable SBMs characterization method to use as a guiding tool for designing superior and high performance drill-in fluid for non-damaging drilling operation.

Historically, color, provenience, origin, degree of diagenesis and metamorphism of the SBM samples or acid solubility were evaluated to use as a guiding tool to select highly durable and mechanically strong SBM products. These subjective and inappropriate methods of assessment frequently lead to disastrous SBMs performance. Due to the limitation and ambiguity of the petrographic and acid solubility methods, attempt was made to identify high quality SBMs by using Brinnel Hardness Tester. The outcome of the research was inconclusive and provided no guiding tool for SBMs performance evaluation. Failure of the above approaches lead to the development of the Aramco method for characterization, quality control and quality assurance of SBMs. Though the method is good for coarse and medium grades SBMs, it has some limitations for fines and ultra-fine SBMs. To overcome the limitations of the Aramco method, it was extended by introducing a dedicated software driven laser particle size analyzer that can measure the PSD of all grades of SBMs quickly and accurately.

This paper describes the Extended Aramco Method and its application in various SBMs evaluations to select the superior and reject the inferior for high performance drill-in fluid design. Experimental results demonstrate the universal application of the Extended Aramco Method and its usefulness in SBM performance evaluation for superior fluid formulations and non-damaging drilling operations.

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