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Short-Term Energy OutlookPetroleum Products Supply Model Description |
The Energy Information Administration (EIA) of the U.S. Energy Department (DOE) developed the Short-Term Integrated Forecasting (STIFS) model to generate short-term (up to 8 quarters), monthly forecasts of U.S. supplies, demands, imports, stocks, and prices of various forms of energy. The purpose of this report is to define the petroleum product supply model in STIFS and describe its basic properties. This report documents the May 1998 version of the petroleum product supply equations in STIFS.
This report is written for persons who want to know how short-term energy markets forecasts are produced by EIA. The report is intended as a reference document for model analysts, users, and the public.
The driving forces in the STIFS petroleum product supply model are estimated refinery inputs and refined product demands. Estimated refinery outputs of individual products yield share weights with which to disaggregate total refinery inputs. Net product imports and inventory change bear the burden of balancing product supply with product demand.
Inputs to refineries include crude oil, unfinished oils, liquefied petroleum gases (LPGs), pentanes plus, and "other" petroleum products. Refinery atmospheric distillation capacity presents a constraint on refinery inputs of crude oil and unfinished oils. The most recently reported operable refinery atmospheric distillation calendar day capacity is carried through the forecast period unless a change in capacity is exogenously specified by the analyst. If projected refinery inputs exceed a specified operating factor (e.g., 105 percent of operable calendar day capacity), crude and unfinished oils are proportionately scaled downwards so that the constraint is satisfied.
Six categories of refinery outputs - motor gasoline, jet fuel, distillate fuel, residual fuel, LPGs, and "other" petroleum products - are represented individually in the model. The sixth category, other petroleum products, consists of petrochemical feedstocks, petroleum coke, waxes, lubricants, etc. Total refinery output is adjusted to equal total refinery inputs plus an estimated refinery processing gain. Each refinery output is proportionately scaled upwards or downwards so that a refinery material balance holds.
The sources of crude oil supply to refineries include domestic production, net imports, inventory change, and imbalances between imports for the Strategic Petroleum Reserve (SPR) and the SPR fill rate (or withdrawal from the SPR for sales). Forecasts of domestic crude oil production are supplied by the EIA Office of Oil and Gas, Reserves and Natural Gas Division. Forecasts of the SPR balance are supplied by the DOE Office of Technical Management, Strategic Petroleum Reserve. Crude oil demand is represented by inputs to oil refineries, crude oil used directly as fuel, and losses. Imbalances between crude oil supply and demand are carried by an "unaccounted for" crude oil term.
Estimation periods for petroleum products supply model equations begin no earlier than January 1983. Before 1983, U.S. petroleum refining operations were significantly affected by the Emergency Petroleum Allocation Act of 1973 (PL 93-159, enacted November 27, 1973), which placed government controls of domestic petroleum prices and supply. For example, a bias towards small refiners was included, which resulted in the construction of small topping refineries. Price and allocation controls were eliminated in early 1981 (Petroleum Price and Allocation Decontrol, Executive Order 12287, January 28, 1981). In the 2 years following decontrol, 66 small topping refineries were shut down.
Six categories of refinery inputs are estimated: (1) crude oil; (2) unfinished oils; (3) liquefied petroleum gases; (4) pentanes plus; (5) motor gasoline blend components; and (6) other hydrocarbons/oxygenates. A seventh category, aviation gasoline blending components, is assumed to equal 0.
| Table 1. Refinery Inputs (million barrels per day) | ||||||||
| Description | Variable Name | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 |
| Crude Oil | CORIPUS | 13.613 | 13.866 | 13.973 | 14.195 | 14.662 | 14.889 | 14.804 |
| Unfinished Oils | UORIPUS | 0.696 | 0.536 | 0.513 | 0.416 | 0.399 | 0.350 | 0.367 |
| Liquefied Petroleum Gas | LGRIPUS | 0.327 | 0.296 | 0.289 | 0.278 | 0.263 | 0.253 | 0.238 |
| Pentanes Plus | PPRIPUS | 0.164 | 0.170 | 0.183 | 0.171 | 0.153 | 0.150 | 0.134 |
| Motor Gasoline Blend Components | MBRIPUS | 0.029 | - 0.041 | - 0.028 | 0.121 | 0.094 | 0.061 | 0.098 |
| Other Hydrocarbons/Oxygenates | OHRIPUS | 0.192 | 0.199 | 0.294 | 0.310 | 0.343 | 0.350 | 0.367 |
| Aviation Gasoline Blend Components | ABRIPUS | < 0.001 | - 0.003 | - 0.003 | - 0.004 | - 0.005 | - 0.002 | - 0.003 |
| Total Refinery Inputs | PARIPUS | 15.021 | 15.023 | 15.220 | 15.487 | 15.909 | 16.144 | 16.103 |
| Source: Petroleum Supply Annual, Volume 1, DOE/EIA-0340, Table 3. | ||||||||
Refinery input of crude oil (CORIPUS) is estimated as a linear function of current and lagged total petroleum product demand (PATCPUSX), and one- and two-month lags of end-of-month deseasonalized finished motor gasoline stocks (MGPSPUSA) and deseasonalized distillate fuel stocks (DFPSPUSA). The lagged relationship with demand is motivated by the notion that refiners do not adjust refinery runs immediately in response to short-run demand shifts, but will do so gradually. Refinery inputs of crude oil are also expected to be negatively related to refinery inputs of unfinished oils (UORIPUS), net refinery inputs of liquefied petroleum gases (LGRIPUS - LGROPUS), and refinery inputs of "other" liquids (PSRIPUS). Monthly dummy variables are also included to capture seasonality.
CORIPUSX = COR_B0
+ COR_PATC * PATCPUSX
+ COR_PAT1 * PATCPUSX(t-1)
+ COR_MGPS * MGPSPUSA(t-1)
+ COR_MGP1 * MGPSPUSA(t-2)
+ COR_DFPS * DFPSPUSA(t-1)
+ COR_DFP1 * DFPSPUSA(t-2)
+ COR_UORI * UORIPUS
+ COR_LGRI * (LGRIPUS - LGROPUS)
+ COR_PSRI * PSRIPUS
+ monthly dummy variables
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Figure 1. CORIPUS, Refinery Inputs of Crude Oil
January 1976 - December 1999 |
Refinery input of unfinished oils (UORIPUS) generally increased between 1980 and 1993, declined through 1997, and then began to increase again. The regression attempts to capture the overall time trend with the mid-1990s correction:
UORIPUSX = UORI_B0
+ UORI_T * TIME
+ UORI_D9497 * (D94ON - D98ON) * TIME
+ UORI_D98ON * D98ON
+ monthly dummy variables
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Figure 2. UORIPUS, Refinery Inputs of Unfinished Oils
January 1980 - December 1999 |
Total inputs to atmospheric (primary) crude distillation (CODIPUS) is estimated from refinery inputs of crude oil and unfinished oils.
CODIPUSX = CODI_CO * CORIPUSX
+ CODI_UO * UORIPUSX
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Total inputs to atmospheric crude distillation are restricted to be less than or equal to 105% of total operable refinery atmospheric distillation calendar day capacity (ORCAPUS). The most recently reported capacity is carried through the forecast period unless a change in capacity is exogenously specified. If this restriction is violated, crude oil and unfinished oil inputs to refineries are proportionately adjusted downwards. Because distillation capacity is in barrels per calendar day on an annualized basis, refinery runs during a single month are allowed to exceed capacity.
CODIPUS = min (CODIPUSX, ORCAPUS * 1.05)
CORIPUS = CORIPUSX * CODIPUS / CODIPUSX
UORIPUS = UORIPUSX * CODIPUS / CODIPUSX
Refinery utilization rate (ORUTCUS) is defined as total inputs to atmospheric crude distillation units divided by operable refinery atmospheric distillation calendar day capacity:
ORUTCUS = CODIPUS / ORCAPUS
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Figure 3. ORUTCUS, Refinery Distillation Capacity Utilization Rate
January 1976 - December 1999 |
Refinery inputs of liquefied petroleum gases (LGRIPUS) is a function of refinery output of motor gasoline (MGROPUS) and dummy variables representing the Phase I and Phase II vapor pressure summer control seasons (RVPI and RVPII) and winter off-seasons (RVPIW and RVPIIW), and the reformulated gasoline program summer (RVPIII) and winter periods (RVPIIIW). Refer to the EIA forecast analysis feature article "Environmental Regulations and Changes in the Petroleum Refining Operations," for an explanation the impact of environmental regulations for motor gasoline vapor pressure on refinery inputs of liquefied petroleum gases.
LGRIPUS = LGRI_B0
+ LGRI_MG * MGROPUS
+ LGRI_R1 * RVPI
+ LGRI_R1W * RVPIW
+ LGRI_R2 * RVPII
+ LGRI_R2W * RVPIIW
+ LGRI_R3 * RVPIII
+ LGRI_R3W * RVPIIIW
+ monthly dummy variables
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Figure 4. LGRIPUS, Refinery Inputs of LPGs
January 1976 - December 1999 |
A volume ratio (DUMYRPP) of the average annual refinery inputs of pentanes plus to total average annual motor gasoline production is included as an explanatory variable in the pentanes plus refinery inputs (PPRIPUS) regression. Thus, DUMYRPP is the same for all months within a year, but differs from year to year. The value of the DUMYRPP for the last full year of the estimation period is retained as the value for the forecast period.
PPRIPUS = PPRI_B0
+ PPRI_MG * MGROPUS
+ PPRI_DP * DUMYRPP
+ monthly dummy variables
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Figure 5. PPRIPUS, Refinery Inputs of Pentanes Plus
January 1981 - December 1999 |
Refinery inputs of other petroleum products includes motor gasoline blending components, other hydrocarbons/oxygenates, and aviation gasoline blending components (usually a negligible volume).
Refinery inputs of motor gasoline blend components (MBRIPUS) is estimated as a linear function of field production of motor gasoline blend components (MBFPPUSX) and a dummy variable (DY9697) representing a period of unusually high imports of blend components (possibly associated with the 1-1/2 year shutdown of the Tosco, Trainer, PA., refinery).
MBRIPUS = MBRI_B0
+ MBRI_MB * MBFPPUSX
+ MBRI_DY * DY9697
+ monthly dummy variables
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Figure 6. MBRIPUS, Refinery Inputs of Motor Gasoline Blend Components
January 1981 - December 1999 |
Refinery inputs of other hydrocarbons/oxygenates (OXRIPUS) is estimated as a function of MTBE demand (MTTCPUS), the volume of fuel ethanol that is blended at refineries or major terminals (EOPRPUS - EOFPPUS):
OXRIPUS = OXRI_B0
+ OXRI_MT * MTTCPUS
+ OXRI_EO * (EOPRPUS - EOFPPUS)
+ monthly dummy variables
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Figure 7. OXRIPUS, Refinery Inputs of Other HC/Oxygenates
January 1981 - December 1999 |
Refinery inputs of aviation gasoline blend components are assumed to equal 0 over the forecast:
ABRIPUS = 0.0
A subaggregate measure of refinery inputs of "other" petroleum products (PSRIPUS) is then calculated from the identity:
PSRIPUS = MBRIPUS + OXRIPUS
Total refinery inputs (PARIPUS) is calculated from the identity:
PARIPUS = CORIPUS + UORIPUS + LGRIPUS + PPRIPUS + PSRIPUS + ABRIPUS
Six categories of refinery outputs are estimated: (1) motor gasoline; (2) distillate fuel oil; (3) jet fuel; (4) residual fuel; (5) liquefied petroleum gases (LPGs); and (6) "other" petroleum products. The sixth category, other petroleum products, consists of petrochemical feedstocks, petroleum coke, waxes, lubricants, still gas, asphalt and road oil, special naphtha, kerosene, finished aviation gasoline, and miscellaneous products.
The independent variables in the refinery output regression equations are specified on the basis of whether the product (dependent variable) is a substitute or complement to other products. All variables, for example, are treated as complements in production when the level of refinery input is changed, i.e., all dependent variables are positive functions of refinery inputs.
Substitution effects are captured by the relationship of product output to inventories and product prices. Refiners are expected to respond to a lower than normal seasonal stock level or a higher product price by increasing output of that product relative to all other products. This substitution effect is captured in the motor gasoline and distillate fuel equations by using a ratio of the gasoline-to-distillate fuel stock levels and the difference between the wholesale gasoline and distillate prices.
| Table 2. Refinery Outputs (million barrels per day) | ||||||||
| Description | Variable Name | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 |
| Motor Gasoline | MGROPUS | 7.304 | 7.181 | 7.459 | 7.565 | 7.743 | 7.892 | 7.934 |
| Distillate Fuel Oil | DFROPUS | 3.132 | 3.205 | 3.155 | 3.316 | 3.392 | 3.424 | 3.399 |
| Jet Fuel | JFROPUS | 1.422 | 1.448 | 1.416 | 1.515 | 1.554 | 1.526 | 1.565 |
| Residual Fuel | RFROPUS | 0.835 | 0.826 | 0.788 | 0.725 | 0.708 | 0.762 | 0.698 |
| Liquefied Petroleum Gas | LGROPUS | 0.592 | 0.611 | 0.654 | 0.663 | 0.691 | 0.674 | 0.684 |
| "Other" Petroleum Products | PSROPUS | 2.503 | 2.520 | 2.522 | 2.541 | 2.671 | 2.753 | 2.709 |
| Total Refinery Outputs | PAROPUS | 15.787 | 15.791 | 15.994 | 16.324 | 16.759 | 17.030 | 16.989 |
| Source: Petroleum Supply Annual, Volume 1, DOE/EIA-0340, Table 3. | ||||||||
The motor gasoline output (MGROPUS) and distillate fuel output (DFROPUS) regressions treat these two products as substitutes in production from a fixed supply of refinery inputs--both variables are a function of the difference between the motor gasoline wholesale price (MGWHUUSX) and distillate wholesale price (D2WHUUS), corrected for inflation (WPCPIUS), and the ratio of deseasonalized stocks of gasoline-to-distillate fuel (MGPSPUSA / DFPSPUSA).
MGROPUSX = MGRO_B0
+ MGRO_C1 * CORIPUS
+ MGRO_C2 * UORIPUS
+ MGRO_C3 * MBRIPUS
+ MGRO_C4 * OXRIPUS
+ MGRO_C5 * (LGRIPUS - LGROPUS)
+ MGRO_C6 * PPRIPUS
+ MGRO_PR * (MGWHUUSX - D2WHUUS) / WPCPIUS
+ MGRO_PS * MGPSPUSA(t-1)/DFPSPUSA(t-1)
+ monthly dummy variables
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Fig. 8. MGROPUS, Refinery Production of Motor Gasoline
January 1976 - December 1999 |
DFROPUSX = DFRO_B0
+ DFRO_C1 * CORIPUS
+ DFRO_C2 * UORIPUS
+ DFRO_C3 * PSRIPUS
+ DFRO_PR * (MGWHUUSX - D2WHUUS) / WPCPIUS
+ DFRO_PS * MGPSPUSA(t-1)/DFPSPUSA(t-1)
+ monthly dummy variables
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Fig. 9. DFROPUS, Refinery Production of Distillate Fuel
January 1976 - December 1999 |
Jet fuel output (JFROPUS) is assumed to be a substitute in production of both gasoline and distillate (though statistical significance does not hold for the reciprocal relationship in the gasoline and distillate equations). A weather variable, heating degree-day deviation from normal (ZWHDDUS), is included to capture blending of jet kerosene into diesel fuel during the cold winter months. Two time trend variables (TIME and D9101ON*TIME) are included to reflect the slowing of the upward trend in jet fuel output that occurred around 1991.
JFROPUSX = JFRO_B0
+ JFRO_P1 * (MGWHUUSX - JKTCUUS) / WPCPIUS
+ JFRO_P2 * (D2WHUUS - JKTCUUS) / WPCPIUS
+ JFRO_C1 * CORIPUS
+ JFRO_C2 * UORIPUS
+ JFRO_PS * JFPSPUSA(t-1)
+ JFRO_Z * ZWHDDUS / ZSAJQUS
+ JFRO_T * TIME
+ JFRO_D1 * D9101ON * TIME
+ monthly dummy variables
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Fig. 10. JFROPUS, Refinery Production of Jet Fuel
January 1976 - December 1999 |
Residual fuel oil output (RFROPUS) was not found to be significantly associated with relative petroleum product prices. A time trend variable (TIME) is included to reflect the steady decline in the yield of residual fuel oil because of the increase in refinery secondary processing capacity and conversion of heavy liquids to lighter products.
RFROPUSX = RFRO_B0
+ RFRO_C1 * CORIPUS
+ LGRO_C2 * UORIPUS
+ RFRO_PS * RFPSPUSA(t-1)
+ RFRO_T * TIME
+ monthly dummy variables
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Fig. 11. RFROPUS, Refinery Production of Residual Fuel
January 1976 - December 1999 |
Refinery output of LPGs (LGROPUS) is found to be inversely related to the yield of motor gasoline from crude and unfinished oils (MGYLD). Dummy variables representing the reformulated gasoline program summer (RVPIII) and winter seasons (RVPIIIW) are also included. Refer to the EIA forecast analysis feature article "Environmental Regulations and Changes in the Petroleum Refining Operations," for an explanation the impact of environmental regulations on motor gasoline vapor pressure on refinery inputs of liquefied petroleum gases.
LGROPUSX = LGRO_B0
+ LGRO_MG * MGYLD
+ LGRO_C1 * CORIPUS
+ LGRO_C2 * UORIPUS
+ LGRO_R3 * RVPIII
+ LGRO_R3W * RVPIIIW
+ monthly dummy variables
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Figure 12. LGROPUS, Refinery Production of LPGs
January 1981 - December 1999 |
The refinery output of "other" petroleum products (PSROPUS) presents problems in modeling because of the variety of products carried under its umbrella. For simplicity, refinery output of other petroleum products is posited to be a function of its own demand (PSTCPUS), in addition to being directly related to primary refinery inputs.
PSROPUSX = PSRO_B0
+ PSRO_C1 * CORIPUS
+ PSRO_C2 * UORIPUS
+ PSRO_TC * PSTCPUS
+ monthly dummy variables
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Figure 13. PSROPUS, Refinery Production of Other Products
January 1981 - December 1999 |
Because of the various cracking processes within refineries (conversion of heavy oils to lighter petroleum products), total refinery outputs are greater than total refinery inputs. Refinery processing gain (PAGLPUS) is estimated as a linear function of refinery inputs of crude oil (CORIPUS) and inputs of unfinished oils (UORIPUS):
PAGLPUS = PAGL_B0
+ PAGL_CO * CORIPUS
+ PAGL_UO * UORIPUS
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Figure 14. PAGLPUS, Refinery Processing Gain
January 1976 - December 1999 |
Refinery outputs are scaled upwards or downwards based on total refinery inputs and estimated refinery processing gain. Total estimated refinery input plus processing gain is multiplied by calculated refinery output shares for corrected refinery output volumes.
PAROPUSX = MGROPUSX + DFROPUSX + JFROPUSX + RFROPUSX + LGROPUSX + PSROPUSX
MGROPUS = ( MGROPUSX / PAROPUSX ) * ( PARIPUS + PAGLPUS )
DFROPUS = ( DFROPUSX / PAROPUSX ) * ( PARIPUS + PAGLPUS )
JFROPUS = ( JFROPUSX / PAROPUSX ) * ( PARIPUS + PAGLPUS )
RFROPUS = ( RFROPUSX / PAROPUSX ) * ( PARIPUS + PAGLPUS )
LGROPUS = ( LGROPUSX / PAROPUSX ) * ( PARIPUS + PAGLPUS )
PSROPUS = ( PSROPUSX / PAROPUSX ) * ( PARIPUS + PAGLPUS )
Individual corrected refinery outputs are then summed to arrive at total refinery output (PAROPUS):
PAROPUS = MGROPUS + DFROPUS + JFROPUS + RFROPUS + LGROPUS + PSROPUS
The yields of the individual petroleum products from crude oil plus unfinished oils are calculated. Refinery output of motor gasoline is reduced by the volume of refinery inputs of LPGs, pentanes plus, motor gasoline blend components, and oxygenates before calculating the gasoline yield.
MGYLD = (MGROPUS - LGRIPUS - PPRIPUS - PSRIPUS) / (CORIPUS + UORIPUS) DFYLD = DFROPUS / (CORIPUS + UORIPUS) JFYLD = JFROPUS / (CORIPUS + UORIPUS) RFYLD = RFROPUS / (CORIPUS + UORIPUS) LGYLD = LGROPUS / (CORIPUS + UORIPUS) PSYLD = PSROPUS / (CORIPUS + UORIPUS)
The sources of crude oil supply to U.S. refineries include domestic production, net imports, inventory change, and imbalances between imports for the Strategic Petroleum Reserve (SPR) and the SPR fill rate. Crude oil demand is represented by inputs to oil refineries, crude oil used directly as fuel, and crude oil losses. Imbalances between crude oil supply and demand are carried by an "unaccounted for" crude oil term.
| Table 3. Crude Oil Supply (million barrels per day) | ||||||||
| Description | Variable Name | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 |
| Domestic Crude Oil Production | COPRPUS | 6.847 | 6.662 | 6.560 | 6.465 | 6.452 | 6.252 | 5.881 |
| Production - Alaska | PAPRPAK | 1.582 | 1.559 | 1.484 | 1.393 | 1.296 | 1.175 | 1.050 |
| Production - Lower-48 States | PAPRP48 | 5.264 | 5.103 | 5.076 | 5.071 | 5.156 | 5.077 | 4.831 |
| Unaccounted for Crude Oil | COUNPUS | 0.168 | 0.266 | 0.193 | 0.215 | 0.145 | 0.115 | 0.191 |
| SPR Net Withdrawal Rate | CONQPUS | - 0.034 | - 0.013 | < 0.001 | 0.071 | 0.007 | - 0.022 | 0.011 |
| Crude Oil Product Supplied | COTCPUS | 0.010 | 0.009 | 0.007 | 0.007 | 0.002 | 0.000 | 0.000 |
| Crude Oil Net Imports (excl SPR) | CONXPUS | 6.674 | 6.952 | 7.135 | 7.398 | 8.117 | 8.596 | 8.613 |
| Source: Petroleum Supply Annual, Volume 1, DOE/EIA-0340, Table S2. | ||||||||
Total domestic crude oil production (COPRPUS) is calculated from exogenously specified production in the lower-48 states (PAPRP48) and Alaska (PAPRPAK) by the identity:
COPRPUS = PAPRP48 + PAPRPAK
Forecasts of crude oil production for the two U.S. regions are provided by the Energy Information Administration's Office of Oil and Gas.
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Figure 15. COPRPUS, Domestic Crude Oil Production
January 1976 - December 1999 |
Unaccounted for crude oil (COUNPUS) is assumed to be a fixed fraction of refinery inputs of crude oil:
COUNPUS = 0.014 * CORIPUS
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Figure 16. COUNPUS, Unaccounted For Crude Oil
January 1976 - December 1999 |
The SPR fill rate from domestic sources (CODQPUS), fill rate from foreign sources (COCQPUS), and withdrawals for domestic sale (COWQPUS) are supplied by the Department of Energy's Office of Strategic Petroleum Reserve. The net withdrawal rate from the SPR (CONQPUS) is defined by the identity:
CONQPUS = COWQPUS - CODQPUS - COCQPUS
Imports of crude for the SPR (COQMPUS) are set equal to the SPR fill rate from foreign sources:
COQMPUS = COCQPUS
The SPR end-of-month inventory level (COSQPUS) is calculated from opening inventory minus the net SPR withdrawal rate:
COSQPUS = COSQPUS(t-1) - CONQPUS * ZSAJQUS
Crude oil losses (COLOPUS) have historically been very small (less than 5,000 barrels per day since 1981 and less than 500 barrels per day since 1986). Crude oil loss is set equal to 0 for the forecast period:
COLOPUS = 0.0
Crude oil product supplied (COTCPUS), which primarily represents crude oil used directly as fuel, is constrained to 0.0 in the forecast:
COTCPUS = 0.0
A balance between crude oil supply and demand is attained by the identity for net imports of crude oil excluding imports for the SPR (CONXPUS). This balance includes the net withdrawal rate from the SPR:
CONXPUS = - COPRPUS - COUNPUS - CONQPUS
+ COLOPUS + COTCPUS + CORIPUS
+ [COSXPUS - COSXPUS(t-1)]/ZSAJQUS
Total crude oil net imports including the SPR (CONIPUS), is defined by the following identity:
CONIPUS = CONXPUS + COQMPUS
Several other refinery inputs are also domestically produced: LPG's, pentanes plus, other hydrocarbons/oxygenates, motor gasoline blend components, and finished motor gasoline. LPG's and pentanes plus are recovered as liquids from natural gas production. Other hydrocarbons/alcohols represent several sources of refinery inputs, such as methyl tertiary butyl ether (MTBE) produced by petrochemical plants. The sum of field production of motor gasoline blend components and finished motor gasoline represent fuel ethanol field production. Refer to "Finished Motor Gasoline Product Supplied Adjustment," Petroleum Supply Annual 1995, DOE/EIA-0340(94)/1 (Washington, DC, May 1995), pp. 151-152, for an explanation of fuel ethanol field production reporting.
| Table 4. Field Production (million barrels per day) | ||||||||
| Description | Variable Name | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 |
| Natural Gas Liquids (NGLs) | NLPRPUS | 1.736 | 1.727 | 1.762 | 1.830 | 1.817 | 1.759 | 1.850 |
| NGLs - Liquefied Petroleum Gas | LGFPPUS | 1.402 | 1.400 | 1.428 | 1.494 | 1.499 | 1.450 | 1.547 |
| NGLs - Pentanes Plus | PPFPPUS | 0.334 | 0.326 | 0.335 | 0.337 | 0.318 | 0.309 | 0.303 |
| Other Hydrocarbons/Oxygenates | OHRIPUS | 0.187 | 0.183 | 0.238 | 0.279 | 0.293 | 0.322 | 0.320 |
| Motor Gasoline | MGFPPUS | 0.056 | 0.131 | 0.130 | 0.082 | 0.127 | 0.190 | 0.177 |
| Motor Gasoline Blend Components | MBFPPUS | 0.010 | - 0.057 | - 0.064 | - 0.048 | - 0.078 | - 0.132 | - 0.120 |
| Fuel Ethanol | EOFPPUS | 0.066 | 0.074 | 0.065 | 0.034 | 0.050 | 0.058 | 0.057 |
| Source: Petroleum Supply Annual, Volume 1, DOE/EIA-0340, Table 3. | ||||||||
"Wet" natural gas from wells is processed in natural gas liquids recovery plants to separate LPGs and pentanes plus from "dry" natural gas. NGL plant liquid production (NLPRPUS) is estimated from the production of wet marketed natural gas (NMGPPUS), heating degree-days (ZWHDPUS), and monthly dummy variables:
NLPRPUS = NLPR_B0
+ NLPR_NG * NGMPPUS
+ NLPR_ZW * ZWHDDUS / ZSAJQUS
+ NLPR_D1 * D8912
+ monthly dummy variables
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Figure 17. NLPRPUS, Field Production Natural Gas Liquids
January 1981 - December 1999 |
Field production of natural gas liquids is disaggregated into pentanes plus (PPFPPUS) and LPGs (LGFPPUS). Field production of pentanes plus is estimated as an annual average share of natural gas liquids field production (PPNLSUS) and monthly dummy variables. The pentane plus share of NGL plant liquid production for the forecast period is the most recent full year of field production data.
PPFPPUS = PPNLSUS * NLPRPUS
+ monthly dummy variables
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Figure 18. PPFPPUS, Field Production Pentanes Plus
January 1981 - December 1999 |
Field production of LPGs is calculated as the difference between field production of natural gas liquids and field production of pentanes plus:
LGFPPUS = NLPRPUS - PPFPPUS
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Figure 19. LGFPPUS, Field Production LPGs
January 1981 - December 1999 |
Field production of other hydrocarbons/oxygenates (OHRIPUS) is estimated as a function of MTBE production (MTPRPUS), fuel ethanol blended at refineries and bulk terminals (EOPRPUS - EOFPPUS), a dummy variable representing January 1993 (when the new MTBE inventory survey data was incorporated into the data series), and monthly dummies:
OHRIPUS = OHRI_B0
+ OHRI_MT * MTPRPUS
+ OHRI_EO * (EOPRPUS - EOFPPUS)
+ OHRI_D9301 * D9301
+ monthly dummy variables
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Field production of motor gasoline blend components is estimated as a linear function of time and monthly dummy variables:
MBFPPUSX = MBFP_B0
+ MBFP_T * TIME
+ monthly dummy variables
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Figure 20. MBFPPUS, Field Production Motor Gasoline Blend Components
January 1981 - December 1999 |
Fuel ethanol field production (EOFPPUS) is derived from estimated ethanol demand (EOTCPUS):
EOFPPUS = EOTCPUS - 0.030
Field production of motor gasoline is then derived using the identity:
MGFPPUS = EOFPPUS - MBFPPUSX
Inventories of most raw materials and refined products for the forecast period are exogenously specified.
| Table 5. Inventories (million barrels end-of-year) | ||||||||
| Description | Variable Name | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 |
| Crude Oil | COSXPUS | 335.4 | 337.2 | 303.3 | 283.9 | 304.7 | 323.5 | 284.5 |
| Unfinished Oils | UOPSPUS | 88.4 | 91.3 | 86.5 | 87.9 | 88.8 | 90.8 | 86.3 |
| Pentanes Plus | PPPSPUS | 10.6 | 8.6 | 7.1 | 6.4 | 5.7 | 8.7 | 5.4 |
| Finished Motor Gasoline | MGPSPUS | 187.1 | 175.9 | 161.3 | 157.0 | 166.4 | 171.8 | 154.1 |
| Distillate Fuel Oil | DFPSPUS | 140.9 | 145.2 | 130.2 | 126.7 | 138.4 | 156.1 | 125.5 |
| Jet Fuel | JFPSPUS | 40.4 | 46.8 | 40.0 | 39.9 | 44.0 | 44.7 | 40.5 |
| Residual Fuel | RFPSPUS | 44.2 | 41.9 | 37.2 | 45.9 | 40.5 | 44.9 | 35.8 |
| Liquefied Petroleum Gas | LGPSPUS | 106.5 | 99.5 | 93.1 | 86.2 | 89.5 | 115.1 | 89.3 |
| Motor Gasoline Blend Components | MBPSPUS | 39.4 | 39.2 | 41.0 | 38.0 | 43.4 | 43.8 | 39.2 |
| Other Hydrocarbons/Oxygenates | OHPSPUS | 12.7 | 17.2 | 11.6 | 13.1 | 12.5 | 14.2 | 13.6 |
| "Other" Petroleum Products | PSPSPUS | 54.7 | 58.4 | 59.9 | 56.7 | 62.5 | 62.0 | 51.5 |
| Total Refinery Inventories | PASXPUS | 1,060.2 | 1,061.2 | 971.2 | 941.6 | 996.4 | 1,075.6 | 925.7 |
| Source: Petroleum Supply Annual, Volume 1, DOE/EIA-0340, Table 30. | ||||||||
Total raw material (excluding the SPR) plus refined product inventory (PASXPUS) is specified by the following identity:
PASXPUS = COSXPUS + UOPSPUS
+ MGPSPUS + DFPSPUS + JFPSPUS + RFPSPUS
+ LGPSPUS + PPPSPUS + MBPSPUS + OHPSPUS + PSPSPUS
Inventory of pentanes plus (PPPSPUS) is estimated as a fixed stock with seasonal variation:
PPPSPUS = PPPS_B0
+ monthly dummy variables
|
[Click here for Regression Results] |
The inventory of propane (PRPSPUS) is estimated as a function of the total inventory of LPGs (LGPSPUS) with a correction for heating degree-day deviations from normal (ZWHDDUS):
PRPSPUS = PRPS_B0
+ PRPS_LG * LGPSPUS
+ PRPS_ZW * ZWHDDUS / ZSAJQUS
+ monthly dummy variables
|
[Click here for Regression Results] |
Inventories of MTBE (MTPSPUS) and fuel ethanol (EOPSPUS) are aggregated into stocks of Other Hydrocarbons/Hydrogen/Oxygenates (OHPSPUS). Fuel ethanol stocks are assumed to remain constant at the last reported end-of-month inventory.MTBE stocks are estimated from an MTBE balance (see discussion under Oxygenate Balance below). Also included in this category are stocks of other oxygenates such as methanol, which are assumed to remain constant at 700 thousand barrels, through the forecast period, and other hydrocarbons/hydrogen, which are assumed to remain constant at 50 thousand barrels:
OHPSPUS = EOPSPUS + MTPSPUS + 0.750
The STIFS model calculates net imports by means of a material balance around refinery output, inventory change and product demand. Gross exports and gross imports are not estimated
| Table 6. Net Imports (million barrels per day) | ||||||||
| Description | Variable Name | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 |
| Motor Gasoline | MGNIPUS | 0.142 | 0.259 | 0.161 | 0.232 | 0.173 | 0.186 | 0.271 |
| Distillate Fuel Oil | DFNIPUS | - 0.090 | - 0.030 | 0.010 | 0.040 | 0.076 | 0.086 | 0.088 |
| Jet Fuel | JFNIPUS | 0.040 | 0.097 | 0.080 | 0.063 | 0.056 | 0.098 | 0.096 |
| Residual Fuel | RFNIPUS | 0.250 | 0.189 | 0.051 | 0.147 | 0.074 | 0.137 | 0.108 |
| Liquefied Petroleum Gas | LGNIPUS | 0.117 | 0.144 | 0.089 | 0.115 | 0.119 | 0.152 | 0.132 |
| Pentanes Plus | PPNIPUS | 0.031 | 0.039 | 0.044 | 0.043 | 0.029 | 0.023 | 0.038 |
| Unfinished Oils | UONIPUS | 0.491 | 0.413 | 0.349 | 0.367 | 0.353 | 0.302 | 0.317 |
| "Other" Petroleum Products | PSNIPUS | - 0.053 | - 0.021 | - 0.033 | 0.094 | 0.162 | 0.184 | 0.250 |
| Total Petroleum Product Imports | PANIPUS | 0.929 | 1.089 | 0.751 | 1.100 | 1.040 | 1.168 | 1.300 |
| Source: Petroleum Supply Annual, Volume 1, DOE/EIA-0340, Table 3. | ||||||||
Net imports of refined products are derived using a material balance identity around product demand, inventory change, refinery inputs, refinery output, and field production:
MGNIPUS = MGTCPUS + [MGPSPUS - MGPSPUS(t-1)] / ZSAJQUS - MGROPUS - MGFPPUS
DFNIPUS = DFTCPUS + [DFPSPUS - DFPSPUS(t-1)] / ZSAJQUS - DFROPUS
JFNIPUS = JFTCPUS + [JFPSPUS - JFPSPUS(t-1)] / ZSAJQUS - JFROPUS
RFNIPUS = RFTCPUS + [RFPSPUS - RFPSPUS(t-1)] / ZSAJQUS - RFROPUS
LGNIPUS = LGTCPUS + [LGPSPUS - LGPSPUS(t-1)] / ZSAJQUS + LGRIPUS - LGROPUS - LGFPPUS
PPNIPUS = PPTCPUS + [PPPSPUS - PPPSPUS(t-1)] / ZSAJQUS + PPRIPUS - PPFPPUS
UONIPUS = UOTCPUS + [UOPSPUS - UOPSPUS(t-1)] / ZSAJQUS + UORIPUS
Net imports of "other" petroleum liquids (PSNIPUS) includes miscellaneous petroleum products, petrochemical feedstocks, and motor and aviation gasoline blending components. Field production was classified in the "other" category (PSFPPUS) only during the period January 1981 through December 1988.
PSNIPUS = PSTCPUS - COTCPUS - PPTCPUS + MBTCPUS + ABTCPUS
+ [PSPSPUS - PSPSPUS(t-1)] / ZSAJQUS
+ [MBPSPUS - MBPSPUS(t-1) / ZSAJQUS
+ [OHPSPUS - OHPSPUS(t-1)] / ZSAJQUS
+ PSRIPUS - PSROPUS - PSFPPUS - MBFPPUS - OHRIPUS
Total net imports (PANIPUS) is:
PANIPUS = MGNIPUS + DFNIPUS + JFNIPUS + RFNIPUS
+ LGNIPUS + PPNIPUS + UONIPUS + PSNIPUS
The blending of oxygenates, such as fuel ethanol and methyl tertiary butyl ether (MTBE), into motor gasoline has increased dramatically in the last few years because of the oxygenated and reformulated gasoline programs. (For a more detailed discussion of oxygenate blending refer to EIA forecast analysis feature article, "Oxygenate Supply/Demand Balances in the Short-Term Integrated Forecasting Model.") Oxygenated gasoline must contain a minimum 2.7 percent oxygen by weight while reformulated gasoline requires a minimum 2.0 percent oxygen by weight. Oxygenate balances are in MTBE-equivalent volume (about 0.5 gallons of ethanol has the same oxygen content as 1 gallon of MTBE.)
| Table 7. Oxygenates | |||||||||
| Description | Variable Name | Units | 1993 | 1994 | 1995 | 1996 | 1997 | 1998 | 1999 |
| Oxygenated Gasoline Share of Total Gasoline Production | OXFRAC | frac | 0.110 | 0.091 | 0.026 | 0.023 | 0.026 | 0.032 | 0.032 |
| Reformulated Share of Total Gasoline Production | RFFRAC | frac | 0.000 | 0.028 | 0.251 | 0.296 | 0.302 | 0.306 | 0.321 |
| Oxygenated-Reformulated Share of Total Gasoline Production | OPFRAC | frac | 0.000 | 0.012 | 0.032 | 0.017 | 0.019 | 0.020 | 0.008 |
| Ethanol Production | EOPRPUS | mmb/d | 0.075 | 0.083 | 0.088 | 0.063 | 0.083 | 0.089 | 0.096 |
| Ethanol Net Imports | EONIPUS | mmb/d | 0.001 | 0.001 | 0.001 | 0.001 | < 0.001 | < 0.001 | < 0.001 |
| Ethanol Inventory (end of year) | EOPSPUS | mmb | 2.114 | 2.393 | 2.186 | 2.065 | 2.925 | 3.406 | 4.024 |
| Ethanol Demand | EOTCPUS | mmb/d | 0.075 | 0.083 | 0.090 | 0.064 | 0.082 | 0.088 | 0.094 |
| MTBE Production | MTPRPUS | mmb/d | 0.136 | 0.144 | 0.163 | 0.185 | 0.198 | 0.206 | 0.216 |
| MTBE Net Imports | MTNIPUS | mmb/d | 0.013 | 0.028 | 0.039 | 0.036 | 0.048 | 0.033 | 0.046 |
| MTBE Inventory (end of year) | MTPSPUS | mmb | 10.035 | 13.769 | 8.702 | 10.008 | 8.229 | 9.653 | 8.094 |
| MTBE Demand | MTTCPUS | mmb/d | 0.160 | 0.161 | 0.216 | 0.218 | 0.251 | 0.235 | 0.267 |
| Source: Petroleum Supply Annual, Volume 1, DOE/EIA-0340, Tables 4, 33, 45, D1.
OXFRAC, OPFRAC, and RFFRAC are estimated values based on control area population/demand shares. | |||||||||
| Units:
frac - Fraction of total mmb - Million barrels mmb/d - Million barrels per day | |||||||||
Oxygenate demand forecasts are based on exogenously specified market shares for the following types of regulated motor gasoline:
Oxygenated motor gasoline and OPRG are assumed to contain 15.2 percent MTBE by volume, and RFG is assumed to require 11.7 percent MTBE by volume. Given estimates of total refinery production of motor gasoline (MGROPUS), regulated gasoline production shares, and required oxygenate content, oxygenate demand for blending into regulated motor gasoline can be derived.
Continued demand for ethanol in gasohol blending, and demand for MTBE as an octane blendstock, is exogenously specified (OZTCPAD) and added to the demand for oxygenates in regulated motor gasolines to arrive at total oxygenate demand. A typical forecast assumption is for continued demand for oxygenates in gasohol and octane blending of 70 thousand barrels per day MTBE-equivalent volume during the summer months and 40 thousand barrels per day during the winter.
OZTCPUS = [0.152 * (OXFRAC + OPFRAC) + 0.117 * RFFRAC] * MGROPUS + OZTCPAD
Total oxygenate demand is then disaggregated into ethanol and MTBE (and other ethers) demands based on the assumption that ethanol demand is supply-driven and that MTBE and other ethers satisfy the remaining demand.
Ethanol production (EOPRPUS) and net imports (EONIPUS) are assumed to remain constant over the forecast period:
EOPRPUS = 0.090
EONIPUS = 0.0
Fuel ethanol inventory (EOPSPUS) is also assumed to remain constant and is exogenously fixed at the most recent level reported in the Petroleum Supply Monthly.
Fuel ethanol demand for gasoline blending (EOTCPUS) is calculated from a material balance around production, imports, and stock change:
EOTCPUS = EOPRPUS + EONIPUS - [EOPSPUS - EOPSPUS(t-1)]/ZSAJQUS
The MTBE demand (MTTCPUS) forecast is derived from the difference between estimated total oxygenate demand and assumed ethanol demand (converted to MTBE-equivalent volume - about 2 gallons of MTBE have the same oxygen content as 1 gallon of ethanol):
MTTCPUS = OZTCPUS - 2.0 * EOTCPUS
MTBE net imports (MTNIPUS) are assumed to remain constant at 40 thousand barrels per day over the forecast period.
MTNIPUS = 0.045
An MTBE production (MTPRPUS) forecast is exogenously specified, and adjusted to produce a reasonable stock path (MTPSPUS).
MTPSPUS = MTPSPUS(t-1) + (MTPRPUS + MTNIPUS - MTTCPUS) * ZSAJQUS
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