Method to improve the efficiency of pipeline transportation of heavy oils

Abstract

Disulfide oil (DSO) compounds recovered as a by-product of the mercaptan oxidation of a hydrocarbon refinery feedstock and their oxidized derivatives, oxidized disulfide oils (ODSO) are effective as a diluent to lower the viscosity and thereby improve the pipeline transportation properties of heavy oils, and particularly of wellhead crude oil. The use of the DSO and/or ODSO compounds as diluents converts an otherwise extremely low value or waste oil product into a valuable commodity that has utility in improving the transportation properties of heavy oils, particularly in oil field pipeline applications.

Claims

1. A process for reducing the viscosity of a heavy oil feedstream comprising mixing the heavy oil feedstream in at least one mixing zone with a predetermined amount of a liquid hydrocarbon diluent to produce a heavy oil-diluent blend that has a lower density and a lower viscosity than that of the heavy oil feedstream, wherein the liquid hydrocarbon diluent is one or more oxidized disulfide oil compounds having the general formula:
O.sub.xRSSR where x is an integer in the range of from 1 to 4, R and R are straight, branched or cyclic hydrocarbons having 1, 2, 3 and up to 10 or more carbon atoms that are saturated or unsaturated, and where R and R can be the same or different.

2. The process of claim 1, wherein the heavy oil is selected from crude oil recovered at a wellhead, bitumens, heavy crude oil, coal liquids, atmospheric residue, vacuum residue, pitch from solvent deasphalting, and heavy oil derived from refinery processes such as distillation, solvent deasphalting, delayed coking, or FCC processing.

3. The process of claim 1, wherein the heavy oil-diluent blend comprises diluent in the range of from 1 to 99 W % of the total weight of the blend.

4. The process of claim 1, wherein the heavy oil-diluent blend comprises diluent in the range of from 5 to 50 W % of the total weight of the blend.

5. The process of claim 1, wherein the heavy oil has an initial viscosity of at least 1000 mPa.Math.s at 50 C.

6. The process of claim 1, wherein the heavy oil has an API gravity of less than or equal to 30.

7. A process for reducing the viscosity of a heavy oil feedstream for transportation in an oil pipeline, the process comprising: a. mixing the heavy oil feedstream with a predetermined amount of a fresh liquid hydrocarbon diluent in a mixing zone at a first location to produce a heavy oil-diluent blend that has a lower density and a lower viscosity than the heavy oil feedstream alone, wherein the fresh diluent stream comprises one or more DSO compounds, one or more ODSO compounds, or their combination, where the DSO and ODSO compounds are derived from the mercaptan oxidation of a refinery feedstream; b. recovering the heavy oil-diluent blend from the mixing zone as a product stream at the first location; c. introducing the recovered heavy oil-diluent blend product stream into a first transportation pipeline for transportation to a second location.

8. The process of claim 7, further comprising the steps of: d. receiving the heavy oil-diluent blend of step (c) in the second location and introducing the blend into a fractionation zone for separation of the heavy oil from the diluent; e. recovering the liquid hydrocarbon diluent; and f. recovering or further processing the heavy oil as a product stream.

9. The process of claim 8, further comprising the steps of: g. introducing the diluent recovered in step 14(e) into a second transportation pipeline and returning the diluent to the first location as a recycle diluent stream; and h. introducing the recycle diluent stream and fresh diluent for mixing with heavy oil to produce the heavy oil-diluent blend.

10. The process of claim 8, wherein the heavy oil feedstream is further processed in the second location fractionation zone to provide one or more feeds for downstream refinery operations.

11. The process of claim 7, wherein the heavy oil-diluent blend is free, or substantially free of sediment.

12. The process of claim 7, in which the heavy oil feedstream is wellhead crude oil.

13. The process of claim 7, wherein the heavy oil feedstream is selected from crude oil recovered at a wellhead, bitumens, heavy crude oil, coal liquids, atmospheric residue, vacuum residue, pitch from solvent deasphalting, and heavy oil derived from refinery processes such as distillation, solvent deasphalting, delayed coking, or FCC processing.

14. A process for reducing the viscosity of a heavy oil feedstream comprising mixing the heavy oil feedstream in at least one mixing zone with a predetermined amount of a liquid hydrocarbon diluent to produce a heavy oil-diluent blend that has a lower density and a lower viscosity than that of the heavy oil feedstream, wherein the liquid hydrocarbon diluent is one or more oxidized disulfide oil compounds having the general formula:
O.sub.xRSSOH, where x is 2, 3, or 4 and R can be straight, branched or cyclic hydrocarbons having 1, 2, 3 and up to 10 or more carbon atoms that are saturated or unsaturated.

15. The process of claim 14, wherein the heavy oil feedstream is selected from crude oil recovered at a wellhead, bitumens, heavy crude oil, coal liquids, atmospheric residue, vacuum residue, pitch from solvent deasphalting, and heavy oil derived from refinery processes such as distillation, solvent deasphalting, delayed coking, or FCC processing.

16. A process for reducing the viscosity of a heavy oil feedstream comprising mixing the heavy oil feedstream in at least one mixing zone with a predetermined amount of a liquid hydrocarbon diluent selected from the group consisting of: one or more DSO compounds, one or more ODSO compounds, or a combination thereof to produce a heavy oil-diluent blend that has a lower density and a lower viscosity than that of the heavy oil feedstream, wherein the heavy oil-diluent blend is passed from the at least one mixing zone to a transportation pipeline.

17. The process of claim 16, wherein the heavy oil-diluent blend has a viscosity of less than or equal to 380 mPa.Math.s under the conditions in the transportation pipeline.

18. The process of claim 17, wherein the viscosity of the heavy oil-diluent blend is less than 200 mPa.Math.s.

19. The process of claim 16, wherein the heavy oil-diluent blend passed to the transportation pipeline is at temperatures in the range of from 20 C. to 80 C. and at a pressure in the range of from 1 bar to 5 bars.

20. The process of claim 16, wherein the heavy oil feedstream is selected from crude oil recovered at a wellhead, bitumens, heavy crude oil, coal liquids, atmospheric residue, vacuum residue, pitch from solvent deasphalting, and heavy oil derived from refinery processes such as distillation, solvent deasphalting, delayed coking, or FCC processing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The process of the disclosure will be described in more detail below and with reference to the attached drawings in which the same number is used for the same or similar elements, and where:

(2) FIG. 1 is a simplified schematic diagram of a generalized version of the mercaptan oxidation or MEROX process of the prior art for the liquid-liquid extraction of a combined propane and butane stream;

(3) FIG. 2 is a simplified schematic diagram of an embodiment of the process of the present disclosure; and

(4) FIG. 3 is a graph illustrating the reduction in the viscosity of a heavy oil after addition and mixing with DSO recovered from a refinery mercaptan oxidation process.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) Referring now to FIG. 2, the process and system of the present disclosure includes a mixing zone (110), and a first transportation zone (130), and optionally a fractionation zone (150) and second transportation zone (170). A DSO stream recovered as a by-product of the mercaptan oxidation of a hydrocarbon refinery feedstock and/or an ODSO stream, or mixed DSO/ODSO compounds are used as a diluent stream. A fresh diluent stream (102) and a heavy oil stream (112) are introduced into the mixing zone (110) at a first location for mixing to produce a heavy oil-diluent blend (116). The heavy oil-diluent blend (116) is introduced into the first transportation zone (130) for transport to a second location, e.g., a GOSP or a refinery. The heavy oil-diluent blend (134) that arrives at the second location is unaltered with respect to the heavy oil-diluent blend (116) that passed from the mixing zone. It will be understood that the terms transportation zone comprehends a conventional oil pipeline and/or a pipeline system. Included are collection pipelines extending from multiple wellheads in an oil field to one or more local/regional storage tanks, as well as long-distance pipelines from wellheads to processing facilities.

(6) The heavy oil-diluent blend (134) can optionally be sent to a fractionating zone (150) for separation into a heavy oil stream (152) and a recovered diluent stream (154). Diluent stream (154) can either be discharged for disposal as stream (158) or preferably is recovered as DSO recycle stream (156) and passed to a second transportation zone (170) for its return to the first location as DSO recycle stream (176) at the first location where it is mixed with the fresh diluent stream (102) upstream of the mixing zone (110). In certain embodiments, up to 90 W %, or 95 W %, or even 99 W % of the DSO introduced as the fresh diluent stream (102) is recovered as DSO recovered recycle stream (176) In a further embodiment (not shown), DSO recycle stream (156) is passed to another location for further use.

(7) The heavy oil stream (152) can be processed routinely in downstream refinery operations.

(8) In certain embodiments, the second transportation zone (170) is eliminated. In this embodiment, a separate pipeline is used within the first transportation zone (130) to transport the DSO recycle stream (156) so that it is not commingled with the heavy oil-diluent blend.

(9) In embodiments where the heavy oil-diluent blend (134) is not processed to recover the DSO in a fractionation zone (150), the blend is routinely processed in downstream refinery operations (not shown) at the second location.

(10) Fractionating zone (150) can include a flash drum, a distillation column, a stripper operated with steam, or nitrogen, or a combination thereof, or other fractionation means known in the art.

(11) Examples of suitable feeds constituting the heavy oil stream (112) include crude oil produced at a wellhead, bitumens, heavy crude oil, coal liquids, atmospheric residue, vacuum residue, pitch from solvent deasphalting, and heavy oil derived from refinery processes such as distillation, solvent deasphalting, delayed coking, FCC processing. Suitable feeds include crudes in the categories of Class A, Class B and Class C, as defined above.

(12) In certain embodiments, the heavy oil has an API gravity of less than 30, less than 20, or less than 10. In certain embodiments, the heavy oil has a viscosity greater than about 1,000 mPa.Math.s, and in preferred embodiments, greater than about 380 mPa.Math.s.

(13) The DSO, ODSO, or mixed DSO/ODSO diluent stream is mixed with the heavy oil in a predetermined amount in the range of from 1 W % to 99 W %, and a preferred range of from 5 W % to 50 W %. The diluent stream is compatible with asphaltenes and therefore no sediment formation occurs after mixing with the heavy oil.

(14) In certain embodiments, the heavy oil-diluent blend has a viscosity less than about 400 mPa.Math.s, less than about 380 mPa.Math.s, or less than about 200 mPa.Math.s, as suggested by Hart, A. J Petrol Explor Prod Technol (2014) 4: 327, which is incorporated herein in its entirety by reference.

(15) In certain embodiments, the heavy oil-diluent blend is transported in a pipeline at a temperature in the range of from 20 C. to 80 C., or in the range from 20 C. to 80 C. and at a pressure in the range of from 1 bar to 5 bars.

(16) The refinery operations downstream include, but are not limited to, gas/oil separation plants, processes such as distillation, naphtha hydrotreating, kerosene hydrotreating, diesel hydrotreating, and hydrocracking operations.

(17) In certain embodiments, the diluent stream is comprised of one or more disulfide oil compounds having the general formula RSSR, where R and R are straight, branched or cyclic hydrocarbons having 1, 2, 3 and up to 10 carbon atoms that are saturated or unsaturated, and where R and R can be the same or different.

(18) In other embodiments, the diluent stream is comprised of one or more oxidized disulfide oil compounds having the general formula O.sub.xRSSR, where x is an integer in the range of from 1 to 4, R and R are straight, branched or cyclic hydrocarbons having 1, 2, 3 and up to 10 or more carbon atoms that are saturated or unsaturated, and where R and R can be the same or different.

(19) Other compounds formed in the mixture of oxidized disulfide oil compounds can have the structure O.sub.xRSSOH, where x is 2, 3, or 4 and R can be straight, branched or cyclic hydrocarbons having 1, 2, 3 and up to 10 or more carbon atoms that are saturated or unsaturated.

(20) Table 3 includes ODSO compounds that are polar and water-soluble, and also those that are non-polar and water insoluble. ODSO compounds that contain 1 and 2 oxygen atoms are non-polar and water insoluble. ODSO compounds that contain 3 or more oxygen atoms are water-soluble. The production of either polar or non-polar ODSO compounds is in part dependent on the reaction conditions during the oxidation process. The structure of some of the compounds in Table 3 were derived by comparing experimental .sup.13C-135-DEPT-NMR spectra of the oxidized DSO mixture with a saved database of predicted spectra for the closest correspondence.

(21) TABLE-US-00003 TABLE 3 ODSO Name Formula Structure Examples Dialkyl- thiosulfoxide or alkyl-alkane- sulfinothioate (RSOSR) Dialkyl- thiosulfones or Alkyl-Alkane- thiosulfonate (RSOOSR) Dialkyl- sulfone- sulfoxide Or 1,2-alkyl- alkyl- disulfane 1,1,2-trioxide (RSOOSOR) Dialkyl- disulfone Or 1,2-alkyl- alkyl- disulfane 1,1,2,2- tetraoxide (RSOOSOOR) Dialkyl- disulfoxide (RSOSOR) Alkyl- sulfoxide- sulfonate (RSOSOOOH) Alkyl-sulfone- sulfonate (RSOOSOOOH) Alkyl- sulfoxide- sulfinate (RSOSOOH) Alkyl-sulfone- sulfinate (RSOOSOOH)

(22) As will be understood by those skilled in the art, the temperature of the heavy crude at the wellhead can be in the range of from 45 C. to 120 C. or 150 C., or even up to 200 C. and will exhibit a much lower initial viscosity. The hot produced crude oil can be introduced into a pipeline for long distance transportation to a remote GOSP and/or refinery, or transferred at the elevated temperature into an accumulation tank. Depending upon the season and location of the wellhead and the GOSP, refinery or other holding or processing facility, the temperature of the crude oil will undergo a calculable reduction with a concomitant increase in viscosity that will result in an increase in the energy required to move the heavy oil through the transportation pipeline, and a corresponding reduction in the overall efficiency of the transportation.

(23) In an embodiment of the present method and system, the DSO diluent stream is introduced into the pipeline in predetermined locations along the transport path and in predetermined amounts for the purpose of increasing the overall weight % of the DSO diluents in the heavy oil to periodically or intermittently reduce the viscosity of the heavy oil-diluent blend as it moves through the pipeline. As is well known from fluid mechanics, turbulence and associated loss of energy due to frictional forces occur at pipeline bends and junctions when the heavy oil undergoes a change in direction. The addition of DSO diluents to further reduce viscosity upstream of a section of pipeline in which the heavy oil will undergo significant changes in its flow path that create turbulence can serve to improve the efficiency of the transport through the zone of turbulent flow.

(24) Additional savings can be achieved where the DSO diluent is recovered and recycled to a number of diluent addition stations that are located intermediate the wellhead or first addition station and the GOSP or refinery where the DSO diluent is separated and recovered from the heavy oil for return to one or more intermediate addition stations along the pipeline for use as recycled diluent.

(25) Similarly, additional DSO diluent can be added to the moving heavy oil flowing in the pipeline as the temperature is reduced due to cooling under the prevailing ambient conditions, i.e., the conductive loss of heat through the pipeline walls. The addition of the DSO diluents at predetermined geographically separated locations along a generally straight pipeline that traverses distances extending hundreds of miles, or more, will serve to maintain the viscosity of the blended flow at, or within a desired viscosity range. Diluents can also advantageously be added to pipelines at intermediate locations between wellheads and oil field storage tanks, and between storage tanks and a GOSP or refinery during which transit the flowing heavy oil undergoes a significant reduction in temperature. Use of intermediate addition stations can provide savings in the volume of DSO diluent required to maintain the desired viscosity across the entire length of the pipeline. A savings will also be recognized because only a portion of the recycle diluent is transported to the initial injection point at the distant end of the pipeline.

(26) As will be apparent to those of ordinary skill in the art, the use of one or more intermediate addition stations will require recycle diluent storage tanks, pumps, dedicated recycle transportation pipelines, means for mixing and/or injecting the diluent into the heavy crude, and associated control devices and utilities. Customary and conventional cost-to-benefit calculations can be applied to determine the number and location of intermediate addition stations.

(27) In certain embodiments, not shown, the DSO diluent is simply mixed with the heavy oil stream to lower the viscosity of the heavy oil to facilitate pipeline transport for processing within the battery limits of the refinery.

Example 1

(28) The viscosities of samples of a vacuum residue and a DSO diluent recovered as a by-product of the mercaptan oxidation of a hydrocarbon refinery feedstock were measured at 37.7 C. and found to be 31,116 mPa.Math.s and 0.61 mPa.Math.s, respectively. The properties and composition of the DSO are provided in Table 2. A blending calculation for the vacuum residue-DSO diluent stream was carried out with the results shown in FIG. 3, with the simulated viscosity data for the heavy oil-diluent blend as a function of DSO diluent content in the blend. The results indicated that when the blend included 20V % of the DSO diluent, the viscosity of the blend is sufficiently lowered to meet the pipeline specification of <380 mPa.Math.s,

(29) It will be understood from the above description that the process of the present disclosure provides a cost effective and environmentally acceptable basis for diverting by-product disulfide oils and their oxidized DSO derivatives to a beneficial use.

(30) The process of the present invention has been described above and in the attached figures; process modifications and variations will be apparent to those of ordinary skill in the art from this description and the scope of protection is to be determined by the claims that follow.