The use of planning tools to minimize waste and discharges to the environment during well construction is fast becoming the norm in the oil and gas industry. Air emission control through the same approach is also desirable. Calculating the carbon footprint of a well construction operation is however usually done after the event. When planning the well, air emissions are generally taken into account through qualitative evaluations, and consideration of emissions from disposal activities appears to be somewhat rare. Nevertheless there is a clear advantage in a quantitative analysis of the operation, as it supports emission mitigation at source and allows the engineer to compare different operational choices.

The objective of the development work undertaken was to create a user-friendly yet scientifically defensible methodology for calculation of greenhouse gas (GHG) emissions, air pollutants, fuel consumption and fuel costs before well construction takes place. The aim was to enable engineers to compare different operational choices in a quantitative manner. The developed methodology utilises databases of equipment, specific energy consumption and specific emission factors and allows pre- operational calculations without the need for detailed data on actual power consumption or fuel use. This allows targeted emission mitigation to be incorporated into the planning stage.

The initial phase of the project included a review of GHG calculation methodologies and the air emission reporting requirements in the EU and the USA. Existing methodologies appear to have been designed to support post-operational calculations, where accurate data on fuel consumption and fuel consistency is known, thus some methodology development was required as such data is not available before an operation.

The approach used in this calculator takes into account all aspects of the operation that can be influenced by the operator: Logistics, equipment, fluid choices and waste management options, including different end disposal options. The results include both detailed breakdowns and rapid overviews of emission sources both for greenhouse gases and the traditional air pollutants. Applying the concepts developed in the planning stage supports identification of best practices and allows targeted improvement efforts towards areas of greater emissions. The actual tool can be used for both comparisons during the design stage and as an aid to audits for accurate post-operational emissions audits.

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