Choice of method decision trees tiers

There are three methodological tiers for determining fugitive emissions from oil and natural gas systems, as set out in Section 4.2.2.2. It is good practice to disaggregate the activities into Major Categories and Subcategories in the Oil and Gas Industry (see Table 4.2.2 in Section 4.2.2.2), and then evaluate the emissions separately for each of these. The methodological tier applied to each segment should be commensurate with the amount of emissions and the available resources. Consequently, it may be appropriate to apply different methodological tiers to different categories and subcategories, and possibly even include actual emission measurement or monitoring results for some larger sources. The overall approach, over time, should be one of progressive refinement to address the areas of greatest uncertainty and consequence, and to capture the impact of control measures.

Figure 4.2.1 provides a general decision tree for selecting an appropriate approach for a given segment of the natural gas industry. The decision tree is intended to be applied successively to each subcategory within the natural gas system (e.g., gas production, then gas processing, then gas transmission, then gas distribution). The basic decision process is as follows:

• check if the detailed data needed to apply a Tier 3 approach are readily available, and if so, then apply a Tier 3 approach (i.e., regardless of whether the category is key and the subcategory is significant), otherwise, if these data are not readily available:

• check if the detailed data needed to apply a Tier 2 approach are readily available, and if so, then apply a Tier 2 approach, otherwise, if these data are not readily available:

• check to see if the category is key and the specific subcategory being considered is significant based on the IPCC definitions of key and significant, and if so, go back and gather the data needed to apply a Tier 3 or Tier 2 approach, otherwise, if the subcategory is not significant:

The ability to use a Tier 3 approach will depend on the availability of detailed production statistics and infrastructure data (e.g., information regarding the numbers and types of facilities and the amount and type of equipment used at each site), and it may not be possible to apply it under all circumstances. A Tier 1 approach is the simplest method to apply but is susceptible to substantial uncertainties and may easily be in error by an order-of-magnitude or more. For this reason, it should only be used as a last resort option. Where a Tier 3 approach is used in one year and the results are used to develop Tier 2 emission factors for use in other years, the applied methodology should be reported as Tier 2 in those other years.

Similarly, Figures 4.2.2 and 4.2.3 apply to crude oil production and transport systems, and to oil upgraders and refineries, respectively.

Where a country has estimated fugitive emissions from oil and gas systems based on a compilation of estimates reported by individual oil and gas companies, this may either be a Tier 2 or Tier 3 approach, depending on the actual approaches applied by individual companies and facilities. In both cases, care needs to be taken to ensure there is no omitting or double counting of emissions.

Figure 4.2.1 Decision tree for natural gas systems

Figure 4.2.1 Decision tree for natural gas systems

Note: See Volume 1 Chapter 4, "Methodological Choice and Key Categories" (noting section 4.1.2 on limited resources) for discussion of key categories and use of decision trees

Figure 4.2.2 Decision tree for crude oil production

Figure 4.2.2 Decision tree for crude oil production

Methodical Choice Tree Tier Ipcc

Note 1: See Volume 1 Chapter 4, "Methodological Choice and Key Categories" (noting section 4.1.2 on limited resources) for discussion of key categories and use of decision trees

Note 2: GOR stands for gas/Oil Ratio (see Section 4.2.2.2).

Figure 4.2.3 Decision tree for crude oil transport, refining and upgrading

Figure 4.2.3 Decision tree for crude oil transport, refining and upgrading

Decision Tree And Enpv Oil And Gas

Note 1: See Volume 1 Chapter 4, "Methodological Choice and Key Categories" (noting section 4.1.2 on limited resources) for discussion of key categories and use of decision trees

0 0

Post a comment