Mar-2015

Light tight oil crude comparison

The production method for Eagle Ford and Bakken is via fracturing of the tight or shale formations in two different North America regions. Crude from the fracturing production method is termed Light Tight Oil (LTO).

Scott Sayles
KBC Advanced Technologies

Article Summary

The LTO crudes from the two different formations have different properties although sharing a common crude production technique. The Pacific Asian crudes are produced using conventional methods and qualities also vary by production location. Crudes from both the North America and Pacific Rim are low sulphur, nitrogen and metals making them good candidates for refinery operations.

LTO formations are providing a new crude source to North America and soon to the world1. The economic advantages of processing LTO crudes are the low cost relative to the world market and high quality7,16. The production of LTO crudes is relatively new in North America. However, Asian Pacific conventional crudes having similar crude quality have been in production for a long time. A comparison of crude quality between the two crude sources presents a possible way to provide operating insight and product quality. A comparison between North American LTO (Bakken and Eagle Ford) to Asian Pacific conventional crudes (Bach Ho, Gippsland, Cossack, and Kutubu) with similar crude physical properties is discussed below. Future articles will discuss the crude quality processing impacts to downstream units.

Crude evaluation methodology
Crude evaluation methodology varies and is changing as the upstream production methods change. For example, advanced analytical testing of the crude is required to determine the many different chemicals that might be in the crude2.

Data Source for Comparison
The data tables below are from the KBC™ Petro-SIM® simulation model. The crude assay data are a combination of either the H/CAMS Haverly Systems Incorporated crude data base or as modified by KBC. Eagle Ford assay is an estimate made by KBC and as provided by others19. The reported Eagle Ford crude properties vary significantly depending on the well and a typical assay is not published. The Eagle Ford assay estimate assumes qualities similar to crudes having similar API gravities and properties as reported 6,10,14,19.
Although not shown in the tables, the individual test methods are the typical ASTM type for each reported quality.

Refinery Crude Evaluation Procedure
Changing crude source may trigger a Management Of Change (MOC) process and thus the hazards of a new crude must be carefully considered15. KBC proposes a stepwise process that assists in meeting the standards of the MOC. These steps are:
1. Review the crude assay provided by the supplier.
a. Determine the actual sample source (single well, pilot testing etc.).
b. Request information on method of production (e.g. chemical additions, hydraulic fracturing, or other possibilities).
2. Data reconciliation between the cut testing and the whole crude is required. At a minimum include balances on mass, volume, sulphur, nitrogen and Conradson Carbon Residue with a closure between 99 to 101% for all results.
3. Determine deficiencies and corrective action(s). For example:
a. Mass balance errors.
b. Missing data (sulphur speciation, sediment, trace metals, etc.).
c. Focus on areas the data indicates are possible causes for concern; high TAN, low kerosene yield, etc.
d. Request additional data from the supplier.
4. Using the reconciled data, enter this information into a modeling tool such as KBC’s Petro-SIM to prepare an assay file of whole crude from the cut data. Comparison of the assay may indicate deviations that require additional corrective action, such as poor matching of the cut nitrogen contents.
5. Using a heat and material balanced model of the refinery, such as KBC’s Petro-SIM, evaluate the processing potential for running the crude in the refinery. This allows prediction of the potential value to the refinery for the new crude. Provide runs with multiple crude blends to determine flexibility to process the crude and establish a concentration ceiling at unit constraints.
6. Using realistic crude blends, determine the crude compatibility and requirements for tankage or processing requirements2.
7. Determine an estimate of the incremental variable operating costs for the new crude.
a. Petro-SIM is a heat and material balanced tool that allows accurate prediction of the energy consumption changes for the new crude.
b. The Kinetic Models in Petro-SIM produce projections of hydrotreater catalyst life or FCC catalyst addition requirements.
c. Review the literature, chemical vendors, and other industry sources for possible additional information on the crude.
8. Update the refinery LP for non-linear items using the Petro-SIM output. Run the LP to verify the performance criteria.
9. Use updated crude evaluation data from the supplier to update the simulations.
10. Conduct a preliminary MOC
a. Highlight crude qualities that are outside the current crude types being processed.
b. Evaluate the potential impact on unit performance using the Petro-SIM model output.
c. Metallurgical assessment for increases to TAN, sulphur, nitrogen and other constituents.
11. Prepare a high-level corrective action list of mechanical and process modifications required to meet the new crude’s specific processing needs. Using Petro-SIM, the high-level review can include major equipment sizing and tray performance for example. Update the variable operating costs and prepare a fixed or capital cost summary.
12. If the crude is still of interest, then request a representative sample for independent confirmation of the quality.
Economic evaluation of the new crude requires accurate market pricing data that is often not available. The best initial estimate is determined by understanding the crude’s value to the refinery and back-calculating a breakeven cost for processing the crude. A critical component of the business case is an accurate estimate of both the operating and capital costs associated with the new crude. KBC, working with our clients, develops the impacts allowing ranking of crudes specific to a given refinery’s configuration and operation.

Light tight oil crude quality
lTO crude indicates the formation from which the oil is derived and not necessarily the quality. The common link between different formations is the production chemicals used in the fracturing process. LTO crudes tend to be low sulphur and high nitrogen and the bottoms concentration is low. The low cost, favorable quality aspects and quantity of the crude make it a very attractive choice for the refineries able to process it.
The next sections discuss operational issues to consider during processing of these crudes.

Lto general observations
Common observations about LTO crudes are they produce high value low sulphur products but require changes to the operation to adjust to the differences in quality. Some general observations are discussed below.