FR2489835A1 - Pumpable synthetic crude prodn. from heavy oil - by desalting, visbreaking and distn. - Google Patents

Abstract

Process is claimed for converting heavy oils with a density of more than 0.933 kg/l and a viscosity of 0.1-100 Pa/sec. into pumpable synthetic crudes suitable for use in refineries, pref. with a viscosity below 0.2 Pa/sec. at 10 deg.C. The process comprises (a) desalting the heavy oil, (b) subjecting it to bisbreaking at 400-500 deg.C and less than 30 bar, and (c) distilling the prod. Visbreaking is pref. effected at 440-460 deg.C and 1-20 bar. Distn. conditions can be selected to give the desired prod. characteristics. The process can be operated on-site at the oil field, giVes a synthetic crude which can be transported by pipeline, and yields a by-product residue which can be used in the oil field (e.g. gasified and used to generate steam for enhanced oil recovery).

Description

 The invention relates to the use of a so-called visbreaking refining process for pretreating heavy oils on the production field.

 The object of the invention is to convert a heavy oil into a synthetic crude oil pumpable and transportable by conventional techniques (oil pipeline, boat) and a residue that can be used on the field of production, for example as a source of fuel gas to produce the steam required for assisted recovery techniques: the invention therefore has the effect of lightening the treated oil and thus produce a transportable crude and acceptable by refineries.

The name heavy crude oil can not be fixed on irrefutable experimental data. Heavy crude oil is considered to be those with a API degree of less than 20, a density greater than 0.933 kg / l. More specifically, the process is applicable to oils of API degree less than 15. However, viscosity poses the most difficult problems for the exploitation. The definition of heavy oils is therefore commonly supplemented by admitting that their viscosity is between 100 and 100,000 centipoises, ie 0.1 and 100
Pascals per second in the conditions of the deposit.

In addition to the density and the viscosity, heavy oils are characterized by: - a high value of the ratio aromatic hydrocarbons /
saturated hydrocarbons: Kuop below 11.7 - a high asphaltenes content, greater than 5, 0 -
commonly 10 Ó - a high sulfur content (commonly 3 - 8 0) - sometimes a high content of metal elements.

 The heavy oils treated according to the invention are first desalted according to known methods.

 Viscoreduction is a process commonly used in the refining industry to lower the viscosity of fuels. This is a mild thermal cracking of atmospheric distillation residues or vacuum distillation at low pressures and high temperature (400-5000C).

 Since the limitation of the heavy oils to oil transport is essentially related to their excessively high viscosity, the use of the visbreaking process is a solution to this problem.

 The operating conditions vary depending on the heavy oil to be converted. However, the pressure below 30 bar is more usually between 1 and 20 bar, the temperature is between 400 and 500 C.

 The invention is illustrated by the examples hereinafter given in a non-limiting manner.

 The objective being to manufacture a synthetic crude transportable by pipeline, the reference used is the South-European pipe in which the maximum permissible viscosity is 120 centistockes at 100C is still 21.5 centistockes at 500C, or 0.12 ms at 100C and 0-, 0215m2 s-1 at 50 ° C.

EXAMPLE 1
In this example, a Venezuelan BOSCAN desalted crude is processed, the characteristics of which are summarized in Table I.
TABLE I

<tb> Mass <SEP> volume <SEP> 150C <SEP> 1.0027
<tb> Viscosity <SEP> to <SEP> 50 C <SEP> 7ms-1 <SEP>
<tb><SEP> to <SEP> 1000C <SEP> 0.282m2s-1 <SEP>
<tb> Mass <SEP> volume <SEP> 209C <SEP> 131.5-141.5
<tb> dO <SEP> API <SEP> 9.6
<tb> Carbon <SEP>(<SEP> weight) <SEP> 83.01
<tb> Sulfur <SEP>(<SEP>"<SEP>"<SEP><SEP>)<SEP> 5.33
<tb> Nitrogen <SEP>("<SEP>"<SEP>)<SEP> 0.7
<tb> Vanadium <SEP> (ppm) <SEP> 1 <SEP> 200
<tb> Nickel <SEP>(<SEP>"<SEP>)<SEP> 130
<tb> Asphaltenes <SEP> nC7 (% <SEP> wt) <SEP> 11.0
<Tb>
The visbreaking is carried out under a pressure of 8 bar and at three temperatures: 440, 450, 460 C, which made it possible to manufacture an effluent whose properties are presented in Table 2.

TABLE II

<tb><SEP> TEMPERATURE <SEP> 440 <SEP> 450 <SEP> 460
<tb><SEP> M <SEP> V <SEP> to <SEP> 15 C <SEP> 0.9928 <SEP> 0.9932 <SEP> 0.983
<tb><SEP> Viscosity <SEP> 50 C <SEP> in
<tb><SEP> m2s-1 <SEP> 0.538 <SEP> 0.274 <SEP> 0.291
<tb><SEP> Viscosity <SEP> 500C <SEP> in
<tb><SEP> cst <SEP> 538 <SEP> 274 <SEP> 291
<tb><SEP> d <SEP> API <SEP> 11 <SEP> 11.0 <SEP> 12.4
<tb> Sulfur <SEP>% <SEP> 4.85
<Tb>
The viscosity gain measured as the viscosity of the treated oil, divided by the viscosity of the effluent 150+ varies between 6 and 10.

 By distillation of this effluent at a temperature below that of visbreaking, a synthetic crude having a viscosity of 21.5 centistokes at 50 ° C. (0.0215 ms -1) was prepared.

 The yields of synthetic crude are given according to the temperature in Table 3.

TABLE III

<tb><SEP> TEMPERATURE <SEP> C <SEP> 440 <SEP> 450 <SEP> 460
<tb> of <SEP> visbreaking <SEP> 440 <SEP> 450 <SEP> 460 <SEP>
<tb><SEP> YIELD <SEP>% <SEP> 66 <SEP><SEP> 75 <SEP> 75
<Tb>
The synthetic crude thus prepared has, by way of example, for a temperature of 450 ° C., the following characteristics:
Density MV at 15 C 0.9205
Viscosity at 500C (cSt) 21.5 (0.0215m2s 1)
SS 4.1 of API 22.2
EXAMPLE 2
The oil treated in this example comes from the deposit of
GRENADE on ADOUR in FRANCE. It possesses the characteristics which are related to heavy oils (Table 4) and such that it is practically impossible to treat this pure crude in a refinery. In this case, pre-refining on the field would be necessary.

TABLE 4
MV 15 C 1.0206
Viscosity 50 C 0.7660ms-1 (7660cst)
100 C 0, 338m2s ~ l (388cst)
Sulfur (X%) 8.3
Vanadium (ppm) 7.5
Nickel (ppm) 48
Asphaltenes nC7 (% wt) 12.0
The procedure is as in Example 1.

The visbreaking is performed at 4500C with a furnace pressure of 10 bar. The viscosity gain obtained (viscosity of the load / viscosity of the effluent) is 11.

The effluent has a C gravity of 1.0102 and a viscosity at 500 of 256 cSt. (0,256m2s1).

The synthetic crude after distillation at 50 ° C. is prepared with a yield of 57, it has the following characteristics:
Viscosity at 50 C 21.5 cst 0.0215m-1
degree API 19.1
S% 7.2

Claims (1)

1. A process for converting heavy oils, having a density greater than 0.933 kg / l and a viscosity of between 0.1 and 100 Pascals per second, in pumpable synthetic crude, with a viscosity of preferably less than 0.2 Pascals. per second at 100C, usable in refineries characterized in that it comprises: - a desalting step of heavy oils, - a moderate thermal cracking step between 4000C and 5000C under a pressure lower than  30 bars, called "visbreaking"  a distillation step of the effluent of  visbreaking. 2. Process according to revendicaitation 1 in that the temperatures  visbreaking are preferably between  4400C and 460 C inclusive. 3. Method according to claim 1 characterized in that the  visbreaking pressures are preferably included  between 1 and 20 bar. 4. Method according to claim 1 characterized in that the  distillation of the visbreaking effluent is effec  killed, under pressures and temperatures  with the desired separation.