DIRECTIONAL HOLE CLEANING PROCESS REVIEW: A SYSTEMATIC VIEW

Hole cleaning is one of the most important processes that needs to be monitored and controlled during a drilling operation. Some shortcomings in drilling operations such as low mud rate, low rotational speed or wrong mud system may cause less lift or drag forces and interrupt the cuttings transportation. The best way of facing an industrial problem is to deal with it as a combination in a physical‑systematical model. This paper reviews all different types of hole cleaning studies since 1972. One of the advantages of this review is that the drilling process has been looked upon in a systematic method approach. Output and internal states vectors are related to the input vectors. This form of a modeling is obtained by physical rules and relations of the parameters. Concepts of a systematic analysis are defined for drilling operations such as classification of drilling parameters and defining observability and controllability of internal states in a drilling procedure. Hole cleaning as an internal state has been represented by different parameters such as bed thickness or cuttings concentration over the years. Generally all previous studies on hole cleaning can be divided into four categories: ‑ Sensitivity analysis of hole cleaning: Variation of an internal state by changing a combination of inputs. ‑ Hole cleaning modeling: Systematic presentation of physical relation of inputs and internal states. ‑ Hole cleaning monitoring: Estimation of internal states using measured data. ‑ Controlling the hole cleaning: Desirable internal state value by changing inputs. In addition to a complete survey on previous studies on hole cleaning, this paper defines a new systematic‑physical framework to investigate the drilling operation. Applying such a framework for drilling procedures, any tool or combination of different methods of data analysis, modeling, monitoring and controlling of the procedure can be applied for drilling operational analysis.