The Energy Information Administration (EIA) released complete details of its new weekly gas storage survey methodology in preparation for the release on Thursday morning of the first weekly gas storage estimates using the new design. The agency also said last week that on Thursday it would revise 16 weeks of previously released weekly gas storage data back to July 4 (see Daily GPI, Oct. 24).

Under the new methodology, the weekly survey will include data from 55 storage operators rather than the previous 44 companies. The new sample will cover the equivalent of 91.4% of the working gas storage capacity in the Consuming Region East, 95.5% of the Consuming Region West and 93.2% of the Producing region.

Because the sample percentages will not change, EIA will remove the survey sample coverage column of data as well as the estimated standard error column from its weekly storage report.

Another major change is the way EIA will group the storage companies for the estimation process in the weekly survey. Operators will be put into two groups: those whose data can be used to more reliably predict the working gas levels of non-sampled companies and those whose data do not correlate as well with the data from non-sampled companies. The EIA will use the first group to estimate the working gas volumes of non-sampled operators for each region, while the data from the latter group simply will be included in the survey estimates. These changes are expected to lead to more accurate predictions of total and regional working gas volumes.

Significant differences this year between the weekly storage estimates, which are based on a sampling of companies, and the actual monthly data EIA received from all of the nation’s underground storage operators prompted the agency to plan these sweeping changes to its weekly survey. Over the first six months of this year, there was an average monthly difference of 50 Bcf between the storage data collected from all underground storage operators through EIA Form 191 and the weekly estimates that were based on the storage data collected from the sample of storage operators through Form 912. The difference was greatest in April and May at 83 Bcf/month and smallest in January at 13 Bcf/month. EIA’s goal is to make the weekly estimates more closely match the monthly data.

The agency would not say what the net change in current working gas levels will be. However, last week it reported that the new methodology led to a net change of 32.3 Bcf/month to weekly working gas estimates over the first six months of the year. There was a net increase in weekly working gas estimates in five of the first six months of the year. While there was a 10 Bcf/month drop in January estimates, there were 40 Bcf, 16 Bcf, 40 Bcf, 51 Bcf and 37 Bcf increases for each of the following months through June, respectively.

EIA intends to continue an investigation of its estimation approaches, and will make additional changes when revisions exceed a certain threshold. It also will continue an examination of its survey sampling and may further enlarge the sample size or make other sample modifications.

A detailed discussion of the current changes to the weekly survey methodology is available at https://tonto.eia.doe.gov/oog/info/ngs/methodology.html.

©Copyright 2003 Intelligence Press Inc. All rights reserved. The preceding news report may not be republished or redistributed, in whole or in part, in any form, without prior written consent of Intelligence Press, Inc.