from grapho- + -oil + -logie-logy: inference of future production from an oil production profile. The theory underlying graphoilogy is that production profile is an expression of limited oil reserves; hence, a systematic analysis of the way production profiles are shaped can reveal traits of actual ressources.
Hubbert, M. King. (1956)
Thursday, April 20, 2006
Status of the US Gasoline Stockpiles
This is a quick post about the spectacular drop in gasoline stock that have been reported by the EIA this week:
Fig 1. US gasoline stocks (EIA, 14th April 2006).
I was wondering how significant is this drop in terms of equivalent Number of Day of Forward Consumption (NDFC). The NDFC is a convenient way to take into account the current level of gasoline consumption which is rising every year. I used the data from the spreadsheet available on the EIA website that gives the historical stock and demand levels for gasoline since February 1991. The NDFC values are simply computed by dividing each stock volume by the gasoline demand at each available point int time. Because the EIA produces data only on a weekly basis, I interpolated the data for the remaining days of the year (spline interpolation). Then, for each day of the year, I computed the observed NDFC value distribution (i.e. the frequency of each NDFC value for a given day). The resulting probability map is shown in the background of Fig. 2, the darkest areas indicate the more probable NDFC values from the available historic data (1991-2006).
Fig 2. Observed NDFC values: the shaded gray values are the observed distribution of NDFC values for each day of the year from all the available years (1991 to 2006) (dark means high probability, white means low probability). The lines are for the last 5 years.
Clearly, we can observe that the current stock levels, as well as for the last five years, are in the lower range of what have been observed over the past 15 years. However, this week NDFC value is still near the most probable NDFC value for this days of the year (around 23 days).
For more discussion, there is also a thread on theoildrum and interesting graphs by Oil CEO.