Published: Jan 2010
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TO COMPLETE THE HYDROCARBON CUSTODY transfer transaction, one needs to determine the quality of the hydrocarbons in addition to the volume. Samples of petroleum and petroleum products are examined by various methods of test for the determination of physical and chemical characteristics. The test results are used for quality, quantity, and price determinations that are part of the hydrocarbon custody transfer transaction. Because of the way the test results are used, it is important to note that sampling becomes the most important part of any analysis performed. Sampling is also required for inventory quality validation at many points in addition to the custody transfer points. The same care in sampling is required when sampling for regulatory compliance, process control, or internal quality validations. The samples should be representative of the petroleum or petroleum products in question. The automatic sampling method provides the most representative sample, but it is not always available because it is a dynamic method that requires the product be moving through a pipeline. When automatic sampling is not available then manual sampling becomes the best available method. Manual sampling is performed while the fluid is at rest in a tank or vessel. When manual sampling is used, there is no way to prove the samples are truly representative so they are usually deemed as representative because automatic sampling is not available and manual sampling is the only method of sampling that can be used. We will cover the procedures and equipment necessary to obtain a representative sample on which quantitative and qualitative analyses can be performed in the sections titled “Manual Sampling” and “Automatic Sampling.” We will also cover how sampling affects volume when performing static measurements in “Static Measurements.”
Kosewicz, Peter W.
Assistant Director, The University of Texas-Petroleum Extension Service, Houston, TX
Major, Del J.
Senior Measurement and Allocation Specialist, Shell Exploration and Production Company, Houston, TX
Training Specialist, The University of Texas-Petroleum Extension Service, Houston, TX