Crude Stability Model Output
RELATIVE INSTABILITY INDEX (RX)
Parameter
Value
Critical
Severe
Stable
Unstable 1.5 - 3.0
RIX
– – ppm* ˚ cSt mg KOH/gm
1.70
<1.5
3.0 - 6.0
6.0 - 10.0
CPI
3.93 <5 31.3 11.0
Stabiliser 2168 Demand
Stable emulsion, oily water & solids Desalter
Viscosity TAN API Gravity
Cold preheat, Hot preheat & Heater fouling
0.3 1.8 2.1
% w/w % w/w % w/w % w/w % w/w % w/w
Sulphur
FOULING POTENTIAL INDEX (FPX)
YC7-Asphaltenes
Critical 3.0 - 6.0
<1.0 1.0-2.0 2.0-3.0 Low Moderate Medium
6.0 - 10.0
51.9 31.8 10.6
YSaturates YAromatics
Severe
YResins
Unconventional Fouling
Conventional Fouling
5.6 1.4 1.7
YC5-Asphaltenes
– –
YCII
Hot Preheat fouling
True RIX
Heater fouling
*Based on total charge rate
Figure 2 CrudePlus study: crude stability and emulsion and fouling predictions
80-120 amps for most crude blends. The design residence time for the desalter is 12 minutes for crude oil and 160 minutes for water. The dosage strategies followed split feed technologies.1 The proprietary emulsion breaker (Embreak) feeding rate will be 5-10 ppm, with the dosage split into two locations: one before the cold preheat and another at the mix valve of each stage. The solids wetting agent feed rate will be 3-5 ppm based on incoming crude solids (>60 ppm in raw crude). These chemistries help reduce interfacial film ten - sion, promoting oil and water separation. The desalted crude achieves the key performance indica- tors (KPIs). Specifically, it achieves a crude outlet salt con - centration of <0.5 per thousand barrels (PTB) and 0.2 vol%
basic sediment and water (BS&W) as free water, with 8% wash water and <12 ppm chloride in the wash water. The crude oil inlet is designed for 20 PTB salt and 0.5 vol% BS&W. However, most of the crude blends processed have a salt concentration of <10 PTB. Chloride in the over- head is controlled to <30 ppm without any caustic injection into the desalted crude, ensuring sodium levels are main- tained below 1 ppm in the atmospheric residue. The following section covers the basics of key parame- ters and how each key parameter optimisation approach was followed, considering interdependent variables. Crude oil characteristics and benchmarking study Any desalter optimisation strategy begins with under-
standing the characteristics of the crude oil before moving on to operational parameter optimisation. A detailed crude blend quality analysis was conducted periodically based on crude blend changes and whenever KPIs were not in control for any short period. The crude characterisation testing focused on desalter impact variables, such as crude oil API/density, vis- cosity, salt content, water content, metal content, con- ductivity, compatibility, foul- ing potential, and filterable solids. An emulsion potential study was also conducted using a portable electric desalter
Feed crude characteristics study
Results
Ref method
Feed crude API
29.6
ASTM D287-22 ASTM D7945-21a
Viscosity at 40C, cst Total chloride, ptb
10.73
8.0 7.9 < 1
Inorganic chloride, ptb (extractable) Organic chloride, ppm (non-extractable)
ASTM D6470
ASTM D4929-19a
Solids in crude, ptb
104 104
Filterable solids, ptb (>0.42 micron)
ASTM D4807-88
Iron, ppm
4.3
XRF *
Crude compatibility RIX – Relative instability index CPI – Crude precipitation index FPX – Fouling potential index Crude emulsification study Emulsification tendency
1.7 3.9
CrudePlus * CrudePlus * CrudePlus *
2.02
High
PED PED PED
Emulsification precursor
Iron/filterable solids
Emulsion resolved with solids wetting agent
Synergistic performance
Table 1
32
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