Underbalanced Drilling In The Reservoir, An Integrated Technology Approach

Abstract

Abstract Shell is a major player in the Global deployment of Managed Pressure Drilling (MPD) technology to reduce drilling problems, minimize formation damage and improve reservoir management techniques. The impetus is a recognition that most of the world's mature hydrocarbon reservoirs are in the lower end of the depletion cycle and an increasing number of horizontal wells are left with un-cemented completions. In addition, to access new untapped reserves, requires venturing into deeper water depths and the exploitation of deeper tight gas reservoirs, each with its own challenges. This paper describes the process involving rigorous pre-screening, planning, execution and feedback of learning developed that enables fast implementation of underbalanced drilling (UBD) and integrated technologies into "Brown Field" areas and new business opportunities in "Green Field" development. This begs the question; what is Managed Pressure Drilling technology and what is the relationship with underbalanced drilling? The International Association of Drilling Contractors (IADC) defines Managed Pressure Drilling as "an adaptive drilling process used to precisely control the annular pressure profile throughout the well bore. The objectives are to establish the down-hole pressure environment limits and to manage the annular hydraulic pressure profile accordingly". In a sense managed pressure drilling, covers all drilling, since management of pressure is the goal of all drilling activities. However, there is general industry agreement that Managed Pressure Drilling is an umbrella term that refers to drilling activities conducted in a closed loop system. Conventional overbalanced drilling sits at one end of the Managed Pressure Drilling spectrum and underbalanced drilling at the other end. In conventional drilling, bottom hole pressure is managed by controlling the density of the drilling fluid to maintain well bore pressure profile above the pore-pressure throughout the well bore. Underbalanced drilling on the other hand, the well bore pressure profile is intentionally kept below the pore-pressure of all the exposed formations in the well bore. In between these two extremes are various techniques used to control the annular pressure profile and overcome constraints imposed as a result of the equivalent circulating density of the mud system. Seen from Shell's perspective, Managed Pressure Drilling is a basket of drilling techniques that can be adapted to solve drilling related problems, reduce formation damage and or dynamically characterize production reservoirs (while drilling) to enable improved reservoir management. It is also worthy to note that not all Managed Pressure Drilling techniques require a closed loop system.