On/Off Loading Stations

Analytical options for midstream processors.

When hydrocarbons are moved from production facilities to midstream facilities, it is necessary for the receiving party to confirm the contents and quality of the unloaded product. Failing to perform an accurate analysis of the unloaded product will ultimately cost money, as will taking too long to perform said analysis. As a result, it is essential that the product is analyzed both quickly and accurately.

By all accounts, oil and gas production is expected to increase over the coming years. As it does, there will be an increased pressure on midstream processing plants and pipelines. The greater the volume of product being handled, the greater the cost associated with mistakes and delays. As an extension of this, the AAR has predicted a sharp climb in the amount of crude oil being produced and shipped. This means there will also be an increase in the need for, and value of, analytical options that can properly process crude oil.

Gas Chromatographs:

The analytical methods most commonly employed by midstream processors are based on gas chromatography. These gas chromatographs (GCs) are either stored on-site, or off-site in a lab.

Off-site lab analysis through gas chromatography offers the gold standard in terms of accuracy. Unfortunately this accuracy comes at the cost of expediency. An off-site lab can take up to 6 weeks before returning usable results. Suffice to say, results more than a month after the fact are not particularly useful.

On-site gas chromatography seems the logical response to the long wait times associated with off-site gas chromatography. By moving the GC (and by extension, the analysis) on-site, actionable results can be obtained in minutes instead of weeks. Unfortunately, taking a GC out of the lab environment imposes restrictions on its functions. On-site gas chromatographs lack the temperature ramping oven used in the labs. This means that the heavier components of the sample cannot be boiled off and remain in the liquid. Over time, these tend to accumulate in sample valves, columns, and detectors resulting in increased downtime and maintenance costs. Another limitation of on-site gas chromatographs is their limited ability to handle condensate or crude oil. Simply put, they are too heavy for a GC lacking a temperature ramping oven.

Near Infrared Spectroscopy:

Insight Analytical offers a alternative analytical option, near infrared spectroscopy (NIRS). Unlike gas chromatography, NIRS does not require the use of an oven to boil off the heavier components of liquids. Rather, the design of the NIRS analyzer means that the relative weight of the product does not have a significant impact on the functionality of the analyzer. NIRS can work equally well for natural gas liquids, condensate, and crude oil. This improved versatility does not come at the cost of accuracy or speed. All told, as long as the process pressure is sufficient to maintain a single phase sample without bubbles, the NIRS analyzer can achieve the accuracy of a GC with much greater speed and reliability.

Proper use of a NIRS analyzer requires the creation of a model based on collected samples. A separate model would be required for natural gas liquids, condensate, and crude oil. However, once the models are complete, the analyzer would be capable of detecting and recognizing any of these products and analyze them accordingly. This means that, unlike a GC, a NIRS analyzer does not require prior knowledge of what product is being analyzed.

The following chart offers a comparison of the various analytical options:

If you want to know more about the sampling options available: