Abstract

One of the perceived blockers for Underbalanced Drilling (UBD) operations globally is the necessity for flaring gas in most operations. As the world becomes more aware of the impact of CO2 emissions, oil and gas producers are implementing flaring reduction targets or, in some cases, flaring bans as a key component in their corporate strategies. Project teams make often argue that due to flaring requirements, UBD is not aligned with corporate directives and is is not environmentally acceptable. Thus the technology is eliminated as a considered option when finalizing field development plans. As the UBD industry has matured, use of UBD to increase production and reserve recovery from wells, which has resulted in a reduction of the number of wells needed to develop a field. Reservoir characterization from UBD has been used to better target wells in the reservoir, reducing the chances for "junk wells" with poor or no production. UBD is also used as an enabler to slim down wells with reduced steel requirements and to drill faster with reduced rig emissions. This paper will evaluate the trade off of increased CO2 emissions from UBD flaring against reduced CO2 emissions from fewer required wells, reduced steel requirements and reduced rig time. Case studies of several Shell UBD projects will be presented to determine the "CO2 cost neutral point" and if the projects reduced or increased global CO2 emissions. Conditions under which UBD may be justified to reduce project CO2 emissions will be determined and discussed.

Introduction

With acceptance that global CO2 is resulting in climate change governments and industry are adapting their expectations and behavior. In this environment it is easy to focus on "visible" CO2 emissions, which flaring from any source certainly is. If however we are going to make real reductions in CO2 emissions we must calculate the numbers and base our actions on technical/engineering study. In short, the following questions must be asked and answered:

  1. Do I want to do something because I think it will make my company or myself "look good"?

  2. Do I want to do something because it will make me "feel good"?

  3. Do I want to do something because I think it will reduce the CO2 emissions?

Obviously the optimum answer is "all of the above", but as with any complex issue detailed analysis can often lead to hard choices; UBD flaring is one of those cases. A position that flaring is necessary is paramount to "looking bad" in our cultures and can be a lightning rod for criticism from our peers and management, but what if it actually reduces overall CO2 emissions? A big part of the problem is people tend to accept what they feel comfortable with and focus on what they are uncomfortable with, independent of the facts. Calibration of this emotional response can be made with a comparison of global flaring from the oil and gas industry to the aviation industry. The oil and gas industry is estimated to have flared 1.2 TCF of gas in 2005, about halve of its worst annual flaring in the 1970s. This still constitutes a huge amount of CO2 emissions, with Russia and Nigeria competing for "worst place". This is enough "wasted gas" to supply the global natural gas consumption for approximately 13 days and unquestionably needs to be reduced. However as a comparison, the CO2 emissions for oil and gas industry flaring at 187 million tone annually is comparable to the airline industry emissions of 183 million tone annually. Yet emotionally seeing a picture of a flare in the jungles of Nigeria makes us feels bad and a picture of a smiling family flying on a vacation. The point being, that doing things that we know will reduce CO2 emissions from hard numbers will need to take priority over what makes us look good or feel good if we are to maximize CO2 emission reductions. Global emissions by source category should be considered when discussing how to make meaningful reductions to CO2 emissions. Simply put, we need to focus on the categories that have high CO2 emissions.

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