With ever-tightening environmental regulations and the green initiatives of most operators, drilling waste disposal through downhole hydraulic fracturing often becomes the preferred waste management option. This is because the technology allows drilling wastes to be handled at the drilling site to achieve true zero discharge. However, formation damage due to solid-laden slurry injection can cause large uncertainties in injection well performance and waste containment assurance. Complicating the problems are the many formation damage mechanisms that are often difficult to model with confidence. A holistic approach based on Monte Carlo simulations has been developed for modeling formation damages and their competing contributions to injection well performance and waste containment assurance.
This paper presents a probabilistic approach to modeling and evaluating associated uncertainties, particularly geology and formation damage, and their impacts on waste containment assurance and risk assessment in cuttings reinjection operations. Probabilistic results are important in designing cuttings injection operational procedures, and risk management, and in obtaining regulatory approval. Examples are given to illustrate how to model formation damage caused by intermittent slurry injections and its impacts on waste containment. Monitoring and validation procedures are given to increase quality assurance through operational data evaluation and risk-based modeling result validation.