FISCHER-TROPSCH GASOIL FRACTION

Abstract

The present invention provides a Fischer-Tropsch gasoil fraction having: (a) an initial boiling point of at least 220 C.; (b) a final boiling point of at most 360 C.; (c) a kinematic viscosity at 25 C. according to ASTM D445 of from 3.8 to 4.4 cSt; and (d) of a flash point according to ASTM D93 of at least 100 C. In another aspect the present invention provides a composition and the use of a Fischer-Tropsch gasoil fraction according to the invention.

Claims

1. A Fischer-Tropsch derived gasoil fraction having an initial boiling point of at least 220 C. and a final boiling point of at most 360 C.

2. A Fischer-Tropsch derived gasoil fraction according to claim 1, having an initial boiling point of at least 230 C.

3. A Fischer-Tropsch derived gasoil fraction according to claim 1, having a final boiling point of at most 350 C.

4. A Fischer-Tropsch derived gasoil fraction according to claim 1, having a kinematic viscosity at 25 C. according to ASTM D445 of from 1.4 to 2.6 cSt.

5. A Fischer-Tropsch derived gasoil fraction according to claim 1, having a flash point according to ASTM D93 of at least 75 C.

6. A Fischer-Tropsch derived gasoil fraction according to claim 1, containing no more than 4 wt % of naphthenic paraffins, based on the Fischer-Tropsch derived gasoil fraction.

7. A Fischer-Tropsch derived gasoil fraction according to claim 1, containing isoparaffins and normal paraffins in a weight ratio of isoparaffins over normal paraffins in the range of 4 to 6.

8. A composition comprising a Fischer-Tropsch derived gasoil fraction according to claim 1.

9. A composition according to claim 8, wherein the composition is a drilling mud.

10. A composition according to claim 8, wherein the composition is an explosives composition.

11-12. (canceled)

Description

EXAMPLES

Example 1

Preparation of a Fischer-Tropsch Gasoil Fraction Having an Initial Boiling Point of 234 C. and a Final Boiling Point of 388 C.

[0047] A Fischer-Tropsch product was prepared in a process similar to the process as described in Example VII of WO-A-9934917, using the catalyst of Example III of WO-A-9934917. The C.sub.5+ fraction (liquid at ambient conditions) of the product thus obtained was continuously fed to a hydrocracking step (step (a)). The C.sub.5+ fraction contained about 60 wt % C.sub.30+ product. The ratio C.sub.60+/C.sub.30+ was about 0.55. In the hydrocracking step the fraction was contacted with a hydrocracking catalyst of Example 1 of EP-A-532118. The effluent of step (a) was continuously distilled under vacuum to give light products, fuels and a residue R boiling from 370 C. and above. The conversion of the product boiling above 370 C. into product boiling below 370 C. was between 45 and 55 wt %. The residue R was recycled to step (a). The conditions in the hydrocracking step (a) were: a fresh feed Weight Hourly Space Velocity (WHSV) of 0.8 kg/l.Math.h, recycle feed WHSV of 0.4 kg/l.Math.h, hydrogen gas rate=1000 Nl/kg, total pressure=40 bar, and a reactor temperature in the range of from 330 C. to 340 C.

[0048] The obtained fuels fraction (C5.sup.+370 C.) was continuously distilled to give a Fischer-Tropsch gasoil fraction having an initial boiling point of 234 C. and a final boiling point of 388 C. and an approximate gasoil fraction yield as given in Table 1. The physical properties are given in Table 2.

TABLE-US-00001 TABLE 1 Fischer-Tropsch gasoil fraction Yield 54 ASTM D2892 [wt %]

TABLE-US-00002 TABLE 2 Fischer-Tropsch gasoil fraction Kinematic viscosity at 25 C. 4.1 According to ASTM D445 [mm.sup.2/s] content of aromatics <200 According to SMS 2728 [mg/kg] content of n-paraffins 17.3 According to GCxGC - internal testing methodology [wt %] content of isoparaffins 81 According to GCxGC - internal testing methodology [wt %] Density at 15 C. according 811 ASTM D4052 [kg/m.sup.3] T10 vol. % boiling point 250 According to ASTM D86 [ C.] T90 vol. % boiling point 315 According to ASTM D86 [ C.] Smoke point >50 [mm] Carbon number range paraffins 10-27 Flash point 107 According to ASTM D93 [ C.] content of monomethyl 34 isoparaffins According to GCxGC - internal testing methodology [wt %, based on total isoparaffins] Visual Appearance Clear and bright

Example 2

[0049] To test the suitability of the Fischer-Tropsch gasoil fraction prepared in Example 1 for use in a drilling fluid composition, a drilling fluid composition was prepared composed of the components shown in Table 3.

TABLE-US-00003 TABLE 3 Ingredient Fischer-Tropsch gasoil fraction* [g] 190.8 Emulsifier [g] 10 (Le Supermul, ex. Halliburton) Lime [g] 2.0 (alkalinity buffer, pH controller, carbonate remover) filtration reducer [g] 1.0 (Adapta, ex Halliburton) 25% CaCl.sub.2 Brine [ml] 94.5 Organophilic clay [g] 2.0 (viscosifier, Geltone V, ex Halliburton), Barite [g] 225.0 (weighting agent) Viscosifier [g] 1.0 (Rhemod L, ex. Halliburton) *as prepared in Example 1

[0050] The resulting drilling fluid composition has a density of 1438 gram/l (12 lb/gallon (US)) and a 70/30 oil to water ratio.

[0051] The following characteristics of the resulting drilling fluid composition were tested:

Plastic Viscosity

[0052] The plastic viscosity is determined at a set temperature as the delta between the viscosity of the drilling fluid composition measured at 600 rpm and the viscosity the drilling fluid composition measured at 300 rpm in centipoise. The viscosity measurement is performed using a Fann 35 viscometer and measured at multiple shear rates.

[0053] A low plastic viscosity is preferred and indicates that the fluid is capable of drilling rapidly because of the low viscosity of fluid exiting at the bit (high Rate of Penetration (ROP)).

Yield Point

[0054] The yield point is the viscosity of the drilling fluid composition measured at 300 rpm minus plastic viscosity measured in centipoise at a set temperature.

[0055] Yield point is a measure for the resistance to initial flow, i.e. the stress required to start fluid movement. The yield point is reported in lbf/100 ft.sup.2.

[0056] The yield point is used to evaluate the ability of fluid to lift cuttings out of the annulus. A higher YP is preferred and implies that drilling fluid has ability to carry cuttings better than a fluid of similar density but lower yield point.

Electrical Stability

[0057] Electrical stability value (measured in volts) reflects to the stability of the emulsion of the fluid. If water disperses well in oil phase (good emulsion), the resistivity of drilling fluid will be higher. In contrast, if water disperses badly in oil phase (bad emulsion), the resistivity of drilling fluid will be lower. Using an electrical stability meter, electricity from the electrical stability meter is emitted in to fluid and voltage is measured by the electrical probe electrical stability meter.

Gel Strength

[0058] The gel strength (measured in lbf/100 ft.sup.2) is a measure for the ability of a fluid to suspend solids while the drilling fluid composition is in static condition. Before testing gel strength, the drilling fluid composition must be agitated for a while in order to prevent solids precipitation and subsequently allow the drilling fluid composition remain in static condition for a certain set time (10 seconds, 10 minutes) and then open the viscometer at 3 rpm and read the maximum reading value.

[0059] In Table 4 the measured plastic viscosity, yield point, electrical stability value and gel strengths are reported at two temperatures, 21.1 C. and 48.8 C. (70 F. and 120 F.).

TABLE-US-00004 TABLE 4 Temperature [ C.] 21.1 48.8 Plastic Viscosity [cP] 25 18 Yield point [lbf/100 ft.sup.2] 18 18 Gel Strength [lbf/100 ft.sup.2] 10 sec 12 9 10 min 15 15 Electrical [V] 450 450 stability

[0060] The characteristics as reported in Table 4 are similar to those that can be obtained when preparing the drilling fluid composition with a prior art crude oil based gasoil fraction. However, the Fischer-Tropsch gasoil fraction of the present invention allows for a combination of the characteristics as shown in Table 4, with i.e. compared to prior art crude oil based gasoil fractions, an improved biodegradability as well as a favorable combination of a low viscosity with a high flash point. This combination of properties of the Fischer-Tropsch gasoil fraction of the present invention gives the Fischer-Tropsch gasoil fraction of the present invention a clear advantage over the use prior art crude oil based gasoil fractions.