Design Considerations in Drill Cuttings Re-Injection

Upstream environmental policies require the use of best available and economically sound technology to continually reduce discharge of mud and cuttings waste resulting from drilling operations. Downhole disposal of mud and cuttings waste through hydraulic fracturing is often the preferred waste management option because it can achieve true zero discharge without being limited by the drilling location. Although its first use about 15 years ago, drill cuttings re-injection (DCRI) has grown to become a routine operation performed around the world, this rapid development is due to increasingly stringent environmental regulations for overboard discharge of oil-based muds and synthetic muds cuttings and improved costs compared to alternative disposal options. This downhole disposal technology has shown success in both onshore and offshore drilling operations and it also economically favorable.The two critical engineering questions that must be answered for injection applications are: (1) where does the waste go and (2) how much can we safely inject into a well? Answering these questions require a data gathering for subsurface geology or formation description and logging analysis, criteria for disposal well and injection zone selection and requirement for slurry rheology quality control. Also designing injection strategy selection and injection parameters such as injection rate, batch size, shut-in time required for fracture to close on cuttings, injection equipment requirements, and the geometry of hydraulic fractures created during injection to estimate disposal capacity are the key issues to the success of waste disposal operations.