Making Economic Decisions To Mitigate Lost Circulation

Abstract

Proposal Well construction optimization involves many decisions during the planning and implementation stages. One of the most difficult decisions during the planning stage—choosing the system and the approach to prevent lost circulation— becomes even more difficult during the actual drilling operation due to the "heat of battle" environment. What is generally understood is that lost circulation will be one of the major trouble costs during well construction. In the past, a favored system or approach may have been used for most or all lost circulation incidents. However, improvements in understanding all aspects of lost circulation show that the "favored system" method is technically unwise today in view of logging-while-drilling (LWD) data and other recently developed sources of information. The delineation of fracture geometry induced during drilling, based on rock properties, may point out significant differences in the length and width and seriousness of anticipated induced fractures. Major differences in permeability between shale, sandstone and vugular limestone also show immediately that one-size-fits-all solutions are not going to be effective or efficient. These kinds of potential information need to be incorporated into any plan for controlling lost circulation. This paper discusses models and tools to evaluate differences in the resistance of the borehole to lost circulation and also discusses the rationale for choosing a particular approach to a potential lost circulation problem. The rationale for preventative measures is also explored, along with a method to make an economic decision whether to stop drilling and treat for lost circulation or to keep drilling.