The author presents Texas Gas's approach and methodology for complying with the design and operational aspects of Order 636, while maintaining system security, accounting for real-time constraints, and providing the services required to meet each customer's needs. The process of unbundling Texas Gas's supply, pipeline and storage capacity are described, including some of the dificulties encountered. Texas Gas's eforts to work interactively with their customers during the various stages of the compliance process are also discussed
Order 636 requires natural gas pipelines to separate, or ‘unbundle’, traditional sales services and allocate capacity attributable to each individual aspect of the service. Because Texas Gas has always relied heavily on bundled operation to provide efficient, reliable service to their end-users, Order 636 has had a profound impact on projected design and operational strategies. The greatest challenge was to maintain or exceed historically high levels of safety, reliability, efficiency and customer satisfaction in the post-636 environment as enjoyed in the current environment.
Unbundling of services most be performed in such a manner as to most nearly replicate current bundled service to traditional firm customers. This must be equitable and non-discriminatory, while protecting real-time capacity constraints. To achieve these results, a thorough understanding of how the parts of a specific pipeline system interact is essential.
The contiguous Texas Gas system extends generally from offshore Louisiana to Lebanon, Ohio and physically delivers gas to locations in Louisiana, Arkansas, Mississippi, Illinois, Kentucky, Indiana and Ohio (see Figure 1). Facilities include over 6,000 miles of transmission pipelines, nearly 500,000 installed horsepower, and 10 gas storage fields in Kentucky and Indiana. Major supply areas include east Texas, north Louisiana, south Louisiana, offshore Louisiana and offshore Texas. As shown on the system map, Texas Gas's storage fields are located deep within its market area with over 98% of the total storage capacity interacting with the mainline at the Slaughters, Kentucky compressor station. Storage is Texas Gas's savior on winter peak days, providing needed capacity as the mainline upstream of Slaughters reaches full capacity. In fact, the winter pipeline capacity upstream of storage is roughly 2.0 Bcf/D, while contractual requirements system-wide are over 2.7 Bcf/D. Without storage, Texas Gas would require over 250 miles of 36" pipeline loop and over 100,000 new horsepower to provide current contractual deliveries. Maximum peak day storage withdrawal capabilities are about 1.1 Bcf/D in the latter part of the winter. Because it is not uncommon to experience supply interruptions during extremely cold weather, this peak capability is needed to provide supply security as well as normal requirements. During normal winter days, net withdrawals are usually in the 200-300 MMscf/D range.