Drill cuttings have always been used to gather data from subsurface formations. Since the onset of the drilling industry, mud loggers have used cuttings to plot the lithology column. Reservoir drill cuttings have also been used to further understand formation properties, such as porosity and permeability. In addition, cuttings have been the subject of waste management research for years. Cuttings analysis is an important aspect of real-time drilling operations and the correct sampling, measurement, and interpretation of cuttings help prevent problems and improve drilling performance. The first part of this study describes the sampling and measurement of drill cuttings, while the second examines data interpretation.
Historically, cuttings analysis has been done by the solid control crew to enhance solids-removal efficiency and by mud loggers to obtain subsurface data. Although these two groups communicate their analyses with the drilling engineer, current visual inspection and sampling procedures provide information that is potentially unreliable for real-time drilling decisions. Cuttings affect drilling fluid properties, annular-pressure losses, hole cleaning, wellbore stability/integrity, penetration rate and many other drilling considerations. Cuttings properties such as particle-size distribution, volume, shape, etc., can reveal the start of a drilling problem or offer justifications for decisions to improve performance. Reliable measures must be in place for taking accurate samples and reporting related properties to enable the drilling engineer to make meaningful correlations. This study intends to provide guidelines on sampling and measurement methodology for the benefit of drilling engineers.
With recent advancements and the introduction of real-time particle-size distribution and Coriolis in-line flowmeters, new data sources are available. These tools provide plenty of valuable information, but decisions need to be made about where, when, and how to take samples for reliable output data. Particles mixed with cuttings that are not generated by bit action, e.g., cavings and mud additives, also need to be accounted for and differentiated while sampling and measuring cuttings. There are correlations between drilling problems and cuttings properties; however, if detected early, these problems can be prevented to enhance drilling performance. Early detection is contingent upon a reliable sampling method, which represents the annular cuttings, interacting with the formation. Thus, a procedure is proposed for proper sampling and measurement of cuttings.