The North Dakota Petroleum Council (NDPC) has published its report on the Bakken crude oil as the result of the crude by rail accidents over the past several years. The report outlines the Recomended Best Practices for treating, handling and testing the crude prior to rail car loading and shipment as excerpted below from the article at http://ndoil.org/resources/bkn/
Bakken Field Operations Recommended Best Practices
In addition to reinforcing the preliminary findings presented in May, the final report also outlined Field Operations Recommended Best Practices to ensure consistent operation of field treating equipment, Bakken crude oil quality and testing procedures and shipping classification:
Field Treating Equipment (in an effort to standardize light ends in crude oil presented for market):
Design and operate all equipment within manufacturers recommended operating limits.
Operate Gas/Liquid Separator (if utilized) at the lowest pressure to accommodate gas sales and fluid delivery to the Emulsion Separator/Heater Treater.
Operate Emulsion Separator/Heater Treater pressure to the lowest operating pressure to safely accommodate gas sales and fluid delivery to the production tank battery.
Maintain all fired treating equipment (Emulsion Heater Treater, etc.) temperature between 90° and 120° F+ year round.
Provide maximum tank settling time possible prior to shipment.
Reduce stock tank pressure to lowest pressure possible to maintain vapor collection equipment (engineered flare, vapor recovery, etc.) operational integrity.
Established Typical Bakken (BKN*) Specifications (ranges reflect expected seasonality):
Range
Typical
API Gravity (hydrometer at 60°F)
35° to 45°
42°
Vapor Pressure (ASTM D6377 @ 100°F)
8 to 15 psi
11.5 psi
Initial Boiling Point (ASTM D86)
90°F to 105°F
95°F
Sulfur
<0.3%
0.15%
H2S
<10 ppm
<1 ppm
Light Ends (C2 – C4s)
3% to 9%
5%
*BKN refers to light sweet crude aggregated at rail and pipeline terminals within the Williston Basin. This crude is predominantly sourced from the Bakken common source of supply, but also includes legacy production from various other producing formations located within the proximity of the Bakken field. BKN does not include nonstabilized condensate recovered from wet gas gathering pipelines or from product derived outside the U.S. Williston Basin. Individual well values may be higher or lower than the aggregated values observed at the rail terminals.
Testing Procedures:
Well Site Operators/Purchasers – Prior to each custody transfer or LACT EOM
API gravity corrected to 60° F using hydrometer
Basic Sediment & Water (BS&W) by field centrifugal grind-out
Spot test vapor pressure pending available field testing equipment
Rail/Pipeline Terminal Operators
Test each unit train loading or tank shipment batch
BS&W by field centrifugal grind-out
Test at least midmonth and EOM
ASTM D6377 @100° F vapor pressure using certified laboratory
DOT PHMSA Hazmat Shipping Category
Flammable Liquid Category 3
Packing Group I**
** PG I is recommended even though the majority of samples tested for the study would fall within specifications for PG II. The margin of error for the test methodology can result in different labs testing the same sample with values meeting both PGs. PG I has the more stringent standards and is therefore recommended to avoid further confusion.
Other recommended procedures:
DO NOT deliver fluid recovered from gas pipe lines (a.k.a. “pigging operations”) to crude oil sales system unless processed by stabilization unit capable of lowering vapor pressure below 10 psi at 100° F.
DO NOT blend non-Williston Basin crude oils into the BKN common stream.
DO NOT blend plant liquids (plant condensates, pentanes, butanes or propane) into the BKN common stream.
The full report is available at http://ndoil.org/image/cache/NDPC_Bakken_Crude_Study_-_Final_Report.pdf