Calculating Carbon Intensity¶
OPGEE calculates carbon intensity (CI) as the total CO2-equivalent emissions divided by the flow of either oil or gas at one of possibly multiple system boundaries. Emission and flows are represented as the quantities used or emitted per day.
The user can select functional units of “1 MJ Oil” or “1 MJ Gas” by setting the
functional_unit attribute. Total daily emissions are divided by the daily flow of oil or
gas to produce CI values with units of CO2-eq MJ-1.
Emissions¶
Total CO2-equivalent emissions are computed as the sum of a designated set of greenhouse gases (GHG; see below), weighted by the user’s choice of global warming potential (GWP) values, for all processes in an oil or gas field, plus upstream emissions per unit of imported energy (e.g., grid electricity or pipeline gas.)
The GHGs tracked by OPGEE processes are:
CO2
CO
CH4
N2O
VOC (non-methane volatile organic compounds)
Per-process emissions are grouped into the following categories for reporting:
Combustion
Land-use
Venting
Flaring
Fugitives
Other
Global Warming Potentials¶
Users can choose which set of GWP values to use by setting attributes GWP_horizon
(20 or 100) and GWP_version, which is one of the following:
AR4 – the 4th Assessment Report
AR5 – the 5th Assessment Report
AR5_CCF – AR5 with carbon cycle feedbacks).
The values associated with these choices are shown below.
Gas |
AR4 |
AR5 |
AR5_CCF |
|---|---|---|---|
CO2 |
1 |
1 |
1 |
CO |
1.6 |
2.7 |
5.3 |
CH4 |
25 |
28 |
34 |
VOC |
3.1 |
4.5 |
4.5 |
N2O |
298 |
265 |
298 |
Gas |
AR4 |
AR5 |
AR5_CCF |
|---|---|---|---|
CO2 |
1 |
1 |
1 |
CO |
7.65 |
7.65 |
18.6 |
CH4 |
72 |
84 |
86 |
VOC |
14 |
14 |
14 |
N2O |
289 |
264 |
298 |
Energy use¶
OPGEE tracks the consumption of energy by each process, including:
Natural gas
Upgrader proc. gas
Natural gas liquids
Crude oil
Diesel
Residual fuel
Petroleum coke
Electricity
System Boundaries¶
OPGEE models can define one or more system boundaries which define the set of processes to include when calculating CI. The standard boundaries are Production, Transportation, and Distribution. The Production boundary is defined where oil or gas leaves the field itself, while the Tranportation boundary includes transport (by vehicle or pipeline) to refineries or other downstream processing facilities.
TODO: define distribution boundary
Additional boundaries may be defined by the user by setting the configuration variable
OPGEE.Boundaries. The default value of this variable is:
OPGEE.Boundaries = Production, Transportation, Distribution