Geometry-driven Inventory Shrinkage and Storage Asset Selection for Natural Gas Liquids: A Techno-Economic Evaluation

Abstract

Natural gas liquids (NGLs) experience storage observed apparent shrinkage through volatilization and vapor-space dynamics, reducing saleable yield and degrading inventory integrity. In this study, a short storage period of 7 days and triplicate runs were used to assess the retention of NGL in storage vessels with varied geometries (conical, vertical cylindrical, horizontal cylindrical, cuboidal, spherical), under short-duration, bench-scale, atmospheric screen conditions identical to monitored ambient laboratory conditions (25–31 °C). Readings from the daily manual innage process were used to produce shrinkage curves and cumulative losses. From the third through the seventh day, a slower geometry-dependent loss regime was observed. On the seventh day, retained fractions of 0.384 and 0.186, for conical and spherical vessels, respectively, were obtained. The first 24 hours accounted for ~60–84% of the week-long loss. A scale-independent levelized loss indicator measured in United States dollars per liter per day ranked conical (0.0146) best and spherical (0.0192) worst. Physical loss was translated into production-economics evidence, laboratory loss fractions were annualized for a 1,600 bbl/d NGL facility, and priced at $26.29/bbl. Annual retained revenue ranged from $5.89M/yr (conical) to $2.85M/yr (spherical), implying $3.04M/yr additional retained sales value for conical storage relative to spherical. Metrics for capital recovery were applied to three dewpointing pieces of equipment, which gave payback periods of 0.226–0.758 years and return-on-investments (ROIs) of 132–443%. The data generated showed vessel geometry as a first-order lever for shrinkage mitigation, retained-value capture, and provided metrics for storage asset selection and operating policies.