Drilling Approach Selection Scheme (DASS) for Managed Pressure Drilling Techniques

Conventional and overbalance well drilling practices have been always the main style to reach energy and hydrocarbon resources underground. But as time advances, the conventional energy resources in conventional settings are becoming scarcer. That makes reaching new energy resources a challenging job using conventional ways of drilling. In other words, more resources will be needed to explore deeper in the earth in reduced tolerability, and strict conditions (e.g., Narrow Formation pressure/Fracture pressure window). These strict conditions will need more than the conventional drilling approaches in order to pass through them safely and optimally. That was the rising argument of unconventional drilling techniques as Under Balance Drilling (UBD) and Managed Pressure Drilling (MPD) Techniques. Managed pressure Drilling (MPD), had acknowledged much of attention in past years. The market trends show an increasing interest in using it day after day. The main objective of MPD systems is to provide more tools and methods that would help in controlling downhole pressure within a narrow window between formation and fracture pressures without compromising Health, Safety and Environment (HSE) Values. MPD systems are adding to the value of the well by reducing time and cost, but also they require special considerations (e.g., Rig Modifications, more equipment, higher experience levels….etc.) when utilized. These considerations makes the drilling process more complex. Benjamin Franklin once said “An investment in knowledge pays the best interest.”. That can be applied in well planning phase, by making sure to have a complete understanding of the well situation and conditions to decide the optimum approaches, equipment, and experience level needed in order to develop a vigorous drilling plan. This research aims to develop a fast yet robust well screening criteria for the most used and widespread MPD technique ‘Constant Bottom Hole Pressure (CBHP)’. The study led to the development of ‘Drilling Approach Selection Scheme - DASS’. DASS provides an understanding of different drilling parameters and operations, and their effect on downhole pressure. Moreover, DASS provides an understanding of the benefits on CBHP MPD systems utilization. DASS involves two interconnected steps. The first is to perform hydraulic calculations and sensitivity analysis of drilling parameters (e.g., Rheological model, Surge/swab,….etc.) with respect to API recommended practices “API RP 13D” using a visual basic based software. The second step, is to provide a judgment and decision making scheme that yields the best drilling approach to be applied, depending on the hydraulic calculations and underground geological and pressure parameters. DASS had been applied to a narrow pressure window conditions for a well in Darquain field in Iran, showing that CBHP MPD techniques will be useful if applied in such well conditions, unlike the conventional drilling, which will not be applicable.