A Holistic Approach to Underbalanced Drilling for Ultimate Reservoir Recovery
Authors: Holt Calvin S. , Wilkes Ted M. 
Published: October 2008

Abstract
Of the many challenges facing the Petroleum Industry, the stemming of declining oilfield production around the globe is perhaps the most daunting. Achieving maximum reservoir recovery, has become the mantra for operators seeking more efficiency and productivity. Underbalanced Drilling (UBD), an emerging technology, promises to be the key component of that solution. However, in order to achieve this a whole new approach to the process of initial hydrocarbon discovery to ultimate recovery is required.
The impacts of modern drilling technology and integrated management models have advanced sufficently to where the reduction of exploration and production costs is undisputed. This evolutionary process has led to the current model of multidisciplinary teams, both operator and contractor, managing fields from discovery to abandonment. Though this approach has had some success, it still does not allow for the full interaction of most service providers. Though they are more involved than in the previous discrete business model, they are still not fully integrated in all aspects of field exploitation. With operating costs increasing, and oil prices failing to keep pace the industry cannot afford to ignore value-adding technologies or improvement opportunities in its operator-contractor relationships.
The authors contend that, in order to realize a significant improvement in reservoir performance, a holistic approach to UBD technology is necessary. The paper will briefly review the state of UBD and industry management models, address the first UBD operations in the Asia Pacific, discusss the integration of new enabling technologies and how industry practices impact the acceptance of UBD technology. It will conclude that:UBD, an emerging and enabling technology will be led towards an integrated approach for the benefit of all its stakeholders.That, by participating in a more interactive management model, that would inlcude a "Learning Team", in which UBD suppliers act as "Technology Partners" participating fully in all phases of design, planning, execution and evaluation, it is possible to utilise UBD for maximum reservoir recovery in a safe and profitable manner.

Introduction
Only some 20 years ago, the new technologies of drilling horizontal sections and top drive systems were in their infancy. Experience with conventional directional wells and kelly drive systems made it hard for the industry to accept that these emerging technologies could deliver value. Innovators and early adopters of these technologies, were rewarded with steep learning curves together with cost and safety challenges but ultimately with successful and very profitable wells.
UBD, as new technology, is experiencing the same characteristics of awareness, interest, evaluation, trial and adoption that adopters went through with older technologies. Although its product life cycle, is still in the introduction phase, horizontal well technology and top drive drilling have developed to the point where they could be considered mature and have become the rule, rather than the exception. (See Figure 1) Based on macroeconomic and information trends, UBD technology is expected to gain industry acceptance quicker, than its predecessors.