METHOD AND APPARATUS FOR PROCESSING HYDROCARBONS

Abstract

A method and apparatus break down compounds, typically hydrocarbons, through oxidation. The compounds may still be in-situ or in a man-made location. The method for the processing of hydrocarbons within a location, provides for: a) introducing two electrodes into the location containing the hydrocarbons; b) providing connections between a voltage source and the electrodes; c) applying a voltage of a first polarity to the connections for a first period of time, under the control of a voltage controller; d) applying a voltage of a second, reversed, polarity to the connections for a second period of time, under the control of the voltage controller; e) repeating steps c) and d); steps c), d) and e) promoting the generation of free radicals thereby promoting a reduction in the length of the carbon chain and/or a reduction in the sulphur content and/or a reduction in the heavy metal content of the hydrocarbons.

Claims

1. A method for the processing of hydrocarbons within a location, the method comprising: a) introducing at least two electrodes into the location, the location containing the hydrocarbons; b) providing connections between a voltage source and the at least two electrodes; c) applying a voltage of a first polarity to the connections for a first period of time, under the control of a voltage controller; d) applying a voltage of a second, reversed, polarity to the connections for a second period of time, under the control of the voltage controller; e) repeating steps c) and d) a plurality of times; steps c), d) and e) promoting a reduction in the length of the carbon chain for one of more species present in the hydrocarbon and/or a reduction in the sulphur content of the hydrocarbons and/or a reduction in the heavy metal content of the hydrocarbons.

2. The method according to claim 1, wherein the hydrocarbons are within a volume of material at the location, with the volume of material being a matrix, the matrix being a mixture of liquids and solids, including the hydrocarbons and the surrounding rock.

3. The method according to claim 1, wherein the location is a man-made location for hydrocarbons extracted by human activity, the location being selected from the group: a location built to contain the hydrocarbons; a storage location; a transport location; a conduit through which hydrocarbons pass; a processing location.

4. The method according to claim 1, wherein the voltage is the voltage necessary to achieve a voltage of greater than 0.2V/m across the separation between the electrode of one potential and the electrode of a different potential which is closest to that electrode.

5. The method according to claim 1, wherein the voltage applied is in the form of a voltage pulse profile, the voltage pulse having a first section during which the voltage is at a maximum value, the voltage pulse profile having a first reversed section during which the voltage is at a maximum value, but of opposing polarity.

6. The method according to claim 1, wherein a defined current pulse profile is provided.

7. The method according to claim 6, wherein the defined current pulse profile includes a first section, a second section following on directly from the first section and a third section, wherein a fourth section intermediate the second section and the third section of the defined current pulse profile is also provided.

8. The method according to claim 6, wherein the defined current pulse profile has a first section having a start current value and an end current value, the first section start current value being zero and the first section end current value being the maximum current for the defined current pulse profile

9. The method according to claim 6, wherein the defined current pulse profile has a second section having a start current value and an end current value, the second section start current value being the maximum current for the defined current pulse profile, with the current declining between the second section start current value and the second section end current value, the second section end current value being a declined current value.

10. The method according to claim 9, wherein the defined current pulse continues at that declined current value for a fourth section of a current pulse profile, with the fourth section intermediate the second section and the third section of the defined current pulse profile.

11. The method according to claim 6, wherein the third section has a start current value and an end current value, the third section start current value is less than the maximum current for the defined current pulse profile and/or is the declined current value and the third section end current value is zero.

12. The method according to claim 6, wherein the defined current pulse profile has a first section which lasts for a first time period, the first time period being less than 0.5 ms.

13. The method according to claim 6, wherein the second section of the defined current pulse profile has a duration of between 10 ms and 500 ms.

14. The method according to claim 6, wherein the duration of the fourth section is greater than 500 ms.

15. The method according to claim 6, wherein the third section lasts for a third time period, the third time period being less than 0.5 ms.

16. The method according to claim 6, wherein the first section and/or second section have a current value in excess of the fourth section current value due to the discharge of the charge provided to the volume or material or a part of the volume of material during the immediately previous fourth reversed section.

17. The method according to claim 6, wherein the second section and/or the second reverse section include a current above the declined current value due to the voltage applied causing the one or more of the species to be treated and/or one or more components of the material, particularly of the matrix, to become charged according to the natural capacitance of the system.

18. The method according to claim 6, wherein the fourth section provides the, or a part of the, pulse during which the volume of material or a part of the volume of material becomes charged with the charge which contributes to the second reversed section of the current pulse profile.

19. The method according to claim 1, wherein the method promotes oxidisation by generating free radicals within the location.

20. The method according to claim 1, wherein the hydrocarbon has a first API value at a first time and the hydrocarbon has a second API value at a second time which is after the first time, the second API value being greater than the first API value, without the hydrocarbon being blended and/or mixed and/or contact with any further hydrocarbons of a different composition.

21. The method according to claim 1, wherein the hydrocarbon has a first viscosity value at a first time and the hydrocarbon has a second viscosity value at a second time which is after the first time, wherein the second viscosity value is less than the first viscosity value, without the hydrocarbon being blended and/or mixed and/or contact with any further hydrocarbons of a different composition.

22. The method according to claim 1, wherein the hydrocarbon has a first sulphur content at a first time and the hydrocarbon has a second sulphur content at a second time which is after the first time, the second sulphur content being less than the first sulphur content, without the hydrocarbon being blended and/or mixed and/or contact with any further hydrocarbons of a different composition.

23. The method according to claim 1, wherein the hydrocarbon has a first heavy metal content at a first time and the hydrocarbon has a second heavy metal content at a second time which is after the first time, the second heavy metal content being less than the first heavy metal content, without the hydrocarbon being blended and/or mixed and/or contact with any further hydrocarbons of a different composition.

24. An apparatus for the processing of hydrocarbons within a location, the apparatus including comprising: a) at least two electrodes, the at least two electrodes being introduced into the location, the location containing the hydrocarbons; b) connections between a voltage source and the at least two electrodes; c) a voltage controller for applying a voltage of a first polarity to the connections for a first period of time; d) the voltage controller applying a voltage of a second, reversed, polarity to the connections for a second period of time; e) the voltage controller repeating steps c) and d) a plurality of times; steps c), d) and e) promoting a reduction in the length of the carbon chain for one of more species present in the hydrocarbon and/or a reduction in the sulphur content of the hydrocarbons and/or a reduction in the heavy metal content of the hydrocarbons.

25. A method of calibrating the operating conditions to be used in a method of processing hydrocarbons within a location, the method comprising: a) introducing at least two electrodes into the location, the location containing a sample of the hydrocarbons for processing; b) providing connections between a voltage source and the at least two electrodes; c) applying a voltage of a first polarity to the connections for a first period of time, under the control of a voltage controller; d) applying a voltage of a second, reversed, polarity to the connections for a second period of time, under the control of the voltage controller; e) detecting the current arising within the sample or volume of material; f) varying one or more characteristics of the voltage; g) detecting the current arising within the sample or volume of material with the revised characteristics of the voltage; h) further varying one or more characteristics of the voltage until a defined current pulse profile is detected.

26. The method according to claim 25, wherein the sample is a sample taken from the location for which processing is to be applied and/or the sample is a sample of material believed to have or having equivalent properties to the volume of material.

27. The method according to claim 25, wherein the detected current varies according to one or more of the circuit resistance, the electrical conductivity of the material, the electrical conductivity of the matrix within the material, the electrical conductivity of the fluid within the material and/or one or more species within the material, and/or the number of electrodes provided within the material and/or the positions and/or separations of the electrodes within the material.

28. The method according to claims 25, wherein the defined current pulse profile includes a first section, a second section following on directly from the first section and a third section, wherein a fourth section intermediate the second section and the third section of the defined current pulse profile is also provided.

29. The method according to claim 25, wherein the defined current pulse profile has a first section having a start current value and an end current value, the first section start current value being zero and the first section end current value being the maximum current for the defined current pulse profile

30. The method according to claim 25, wherein the defined current pulse profile has a second section having a start current value and an end current value, the second section start current value being the maximum current for the defined current pulse profile, with the current declining between the second section start current value and the second section end current value, the second section end current value being a declined current value.

31. The method according to claim 30, wherein the defined current pulse continues at that declined current value for a fourth section of a current pulse profile, with the fourth section intermediate the second section and the third section of the defined current pulse profile.

32. The method according to claim 25, wherein the third section has a start current value and an end current value, the third section start current value is less than the maximum current for the defined current pulse profile and/or is the declined current value and the third section end current value is zero.

Description

[0166] In FIG. 1, a geological structure 1 is provided which contains a naturally occurring volume of hydrocarbons 5 in a layer of the geological structure 1. The layer in the geological structure 1 contains a mixture 3 that includes solids, liquids and potentially gases, including hydrocarbons 5. Water is a desirable component of the mixture, for instance at the 3 to 10% proportion by volume.

[0167] For example, the hydrocarbons 5 may be the subject of an extraction process 7 including which has provided a production well 9 and potentially an injection well 11. The mixture 3 may be difficult to extract or unsuitable for extraction using existing approaches. For instance, the mixture may contain a high level of heavy hydrocarbons and a relatively low level of light hydrocarbons. This renders the hydrocarbons 5 as a whole viscous and/or well bounded to the geological structure 1 and hence resistant to extraction.

[0168] Previous treatment attempts at the treatment of the hydrocarbons 5 have included the injection of steam or carbon dioxide into the geological structure 1 with a view to using the heat or pressure to reduce the viscosity or form of the hydrocarbons so as to promote movement and hence extraction at a production well. Burning has been used to generate heat and hence crack the oil in-situ. The in-situ treatments can be effective, but these all have limitations in terms of costs and/or effectiveness and they are also time consuming to achieve.

[0169] The present invention provides a series of electrodes 10 arranged along the length 12 and across the width 14 of a matrix 16 which forms a part of the geological structure and which contains the hydrocarbons 5. The electrodes 10 also have a depth 18 within the matrix 16. The electrodes 10 are provided in a regular array in this example, but other configurations can be used.

[0170] Titanium (with a mixed oxide coating or surface, to avoid any insulating layer) and steel represent preferred materials for the electrodes.

[0171] The electrodes are typically 100 m to 500 m apart from each other along the width and the length of the regular array. The electrodes 10 will typically extend down at least 50% of the depth of the matrix 16 being treated and may span the full depth or more. The electrodes typically have a diameter in excess of 5 cm. The electrodes 10 can extend from the surface the whole way down to the depth of the geological structure 1 being treated, or as shown, may only be present within the geological structure 1 itself (or a part therefor). The wiring 20 (only shown for some electrodes) for the electrodes 10 then provides the link to the surface 13.

[0172] The wiring 20 for the electrodes 10 connects them as a first set 22 of electrodes 10, a second set 24 of electrodes 10, a third set 26 of electrodes 10, a fourth set 28 of electrodes 10 and so on. The potential is applied so as to generate a voltage drop between the first set 22 of electrodes 10 and the second set 24. A voltage drop is also generated between the third set 26 and the fourth set 28. This also generates a voltage drop between the second set 24 and third set 26 and between other sets of electrodes 10. The flexibility of the connections provided by the wiring 20 allows for different combinations of electrodes 10 to be connected to form pairs.

[0173] Suitable power sources 30 and power control units 32 are provided at the surface 13 to generate the desired voltage drops and potentials within the system, and hence voltage pulses. The system is driven with a constant voltage supply, typically from 10 V to 2500 V. Typically voltages are used which provide between 0.5 and 5 V/m of separation between the electrodes; hence between 50 V and 500 V with a spacing between electrodes of 100 m.

[0174] The current output level depends upon the circuit resistance. The circuit resistance is affected by the electrical conductivity of the matrix 16, and particularly the fluid contained therein, as well as the number of electrodes provided and the separation between them.

[0175] The profile of the voltages applied and the impact of the applied voltages on the matrix and compounds are described further below.

[0176] During the method, the process conditions are most effective when the pH is within certain bounds. Natural redox reactions and/or reactions caused by the operation of the method can cause a decrease in pH around the anode and/or an increase in pH around the cathode. If the pH becomes too low then electro-osmosis at the anode stops which impairs the operation of the process. If the pH becomes too high then that can have deleterious effects on the process. However, it is believed that the process is still effective at lower pH's than can be tolerated in electro-osmotic based processes where transportation is being sought, as the process is seeking to provide oxidation of organic species.

[0177] To ensure the appropriate pH, the system can include treatment apparatus, not shown, which receives electrode electrolyte from around the electrodes 10. A perforated tube may be provided around each electrode 10 so as to provide a reservoir of electrode electrolyte in contact with the matrix 16. Pumps draw the electrode electrolyte from the reservoirs along pipes to the treatment apparatus. The treatment apparatus includes a pH adjustment stage and potentially other stages for other desirable treatments for the electrode electrolyte. Cleaned pH adjusted electrolyte arises from these stages and can be returned via pipes to the reservoirs. In this way optimum conditions are provided within the reservoirs and for the process as a whole.

[0178] Significantly, the power consumption with the approach of the invention is very low. The voltage pulse profile is illustrated in FIG. 2a. As can be seen, the voltage pulse profile consists of alternate pulses of opposite polarities with time. The voltage pulses are generally square shaped pulses for both polarities and are of equal duration. Hence, the pulses are used to apply the voltages to the matrix 16 but have no net transport effect on the matrix 16 or more particularly the liquid and compounds within it. The transport effect can be provided by the process as described below. However, where the voltage pulse profile does not provide the net transport effect, then other mechanisms may be used, for instance injection of other materials, application of pressure or forms of displacement.

[0179] Where the pulse profile is to provide at least a part of the net transport effect, then a pulse profile of the form illustrated in FIG. 2b may be used. The difference in duration of application of the pulse with one polarity and the duration of application of the pulse with the opposing polarity provides the net transport effect, potentially through electro-osmotic and/or electro-kinetic effects. Generally the pulse operative in the direction of travel will be between twice and five times the duration of the opposing polarity pulse in such cases. A rest with no or little applied voltage may be used between polarity reversals.

[0180] The square voltage pulse profile features a rapid change from one polarity to the other and then back again. Thus regular square shaped pulses are provided rather than a sinusoidal or other gradual form of changing pulse.

[0181] Whilst the voltage pulse profile is generally square shaped, there are important details in the shape of the current pulse which are sought for the optimum operation of the invention. These apply whether the voltage pulse profile is of the FIG. 2a or FIG. 2b type. As shown in FIG. 3a, when the rapid change in polarity is applied, the current profile rises quickly and reaches a maximum level 100. From the maximum level 100 the level gradually declines, for instance along an elliptical curve 102, to a reduced consistent level 104. A short time 106 after the reduced consistent level 104 is reached, the polarity is reversed and the current profile quickly switches to a maximum level, not shown, of the opposing polarity.

[0182] Typical voltage pulse lengths are between 20 and 200 ms. Short rests may be provided to the system between pulses of one polarity and the other. The rests may be 0.5 ms to 50 ms in duration.

[0183] The maximum level 100 is reached as a consequence of the voltage applied causing the matrix, and potentially the liquid, to become charged according to the natural capacitance of the system. This charge is gradually discharged overtime as reflected in the current pulse shape. The maximum level 100 and gradual reduction is indicative of the formation of free radicals within the matrix. These are very beneficial to the overall process, in particular these free radicals are believed to be involved in the oxidation reactions which treat the compounds, such as hydrocarbons. The presence of water, which usually occurs naturally in-situ, is believed to be beneficial in the promotion of the formation of free radicals.

[0184] Beneficially the free radicals are generated exactly where they are needed for the method to provide the desired treatment, namely at the pore surfaces within the matrix. As a consequence, redox reactions are promoted at those locations too.

[0185] The duration of the pulse is beneficial in generating electro-osmotic forces in a first direction, and then when the polarity is reversed, in the opposite direction for any one species present (depending upon its charge). Thus the charged contents of the pore water move quickly back and forward with the polarity changes. This causes freshly formed oxygen and hydroxyl free radical formed in these electrochemical reactions to move back and forth. This also promotes their involvement in the oxidisation of the compounds present. For instance the free radicals can cause hydrocarbon chains to breakdown into lighter fractions and form carbon dioxide and water as by products. The capacitive nature of the matrix and reactions occur at the grain surface where the pollution is.

[0186] The physical nature of the matrix in many cases, small particulate matter with a moderate or low degree of compaction or with loose material within a more fixed body of material, means that the electrophoretic forces generated (which generally oppose the direction of electro-osmotic forces) cause small amounts of movement by the particulate material. The movement is believed to be beneficial in causing reaction product displacement away from the surfaces and/or pH balance.

[0187] The process conditions are optimised to give the desired current pulse profile illustrated in FIG. 3a in one embodiment. The overshoot in the level and the current pulse length which gives the full gradual discharge are desirable.

[0188] FIG. 3b illustrates a situation where the duration before the polarity is reversed is potentially too long. As a consequence, the same maximum level 100 is provided and the same gradual decay to the reduced consistent level 104, but that level is present for a much longer time frame. This reduced consistent level 104 is believed to reduce the efficiency of the process reactions as the free radical generation has stopped or is present at a lower rate during this phase. However, it may assist with the charging for the reversed polarity part and hence with the effects desired from that reverse polarity when it too discharges.

[0189] FIG. 3c illustrates another version of the same current pulse, but with a shorter time period before the polarity is reversed. As a result, the maximum level 100 is present but the reduced consistent level 104 has not been reached by the time the polarity is reversed. As a result it is believe that some of the free radical generating capacity within the system is not exploited and instead energy must be used to reverse the remaining natural part of the capacitance of the system. A detrimental effect on the charging for the reverse polarity part may also occur as a result.

[0190] The power supply conditions needed to provide the current pulse profile of FIG. 3a may vary from matrix to matrix and/or according to the compound to compound situations encountered within different hydrocarbons. However, investigative measurements can be conducted on the particular system to provide the power supply conditions necessary for the desired profile shape and hence process conditions within the matrix.

[0191] The role of the free radicals generated is to promote oxidisation reactions. The conditions in the matrix are optimised in the present invention, thus adding strength of oxidising to any other form of physical and/or chemical treatment.

[0192] Test operations have demonstrated that the process is effective to oxidise a wide variety of organic compounds. Examples include aliphatic organics with C10 to C40, benzene, toluene, ethyl benzene, xylenes, and polycyclic aromatic hydrocarbons amongst other compounds.

[0193] Particularly in the context of hydrocarbons in forms conventionally considered as oils, the process is effective in breaking down the hydrocarbons from heavy forms to lighter forms. This involves increasing the hydrogen to carbon ratio, normally by reducing the length of the average carbon chain within the hydrocarbon; obviously a variety of different lengths are present. The process is particularly effective in acting on asphaltenes, which as can be seen in FIG. 4, are at the heavy end of the spectrum of hydrocarbons encountered in oils. Breakdown of the carbon chains, proceeding from right to left, gives rise to smaller and shorter carbon chains.

[0194] The process is also believed to act on sulphur present, as inorganic species such as hydrogen sulphide, and/or as organic species such as mercaptans and thiophenes. The impact of the oxidation follows a potentially complex route, but leads to less problematic species such as sulphuric acid and sulphates.

[0195] This breakdown to lighter forms is particularly useful in the context of heavy crude oils, such as those extracted in Canada and Venezuela.

[0196] Heavy crude oil is generally considered to be oil with an API gravity of less than 20 (where an API gravity of 10 matches the density of water). An API below 10 leads to the oil sinking in water, and may be classified as extra heavy oils. The classification of oils as light oils varies with geography, but typically are US originating oils with an API of 37 to 42 and are non-US originating oils with an API of 32 to 42 degrees, such as Brent crude at an API 38.06.

[0197] In general, the heavier a crude oil is, then the greater its viscosity, the more resistant it is to flow and the more it binds or adheres to materials it contacts (including the matrix it is found in).

[0198] In general, heavy crude oil also has a higher, undesirable, sulphur content compared with light oil; potentially as high as 4.5%. The process of the invention is believed to have a role in reducing the sulphur content via oxidation and/or conversion to more readily separable forms. In general heavy oil also typically has a higher heavy metal content and that too needs to be reduced. Again the process of the present invention is believed to have a valuable role in the oxidation and/or conversion of those species and may easy separation.

[0199] In general, heavy crude oil needs cracking, refining and purification to make gasoline from it. This increased processing cost makes heavy oils less valuable than light oils; they are less useful and have less demand without the processing and the processing itself is expensive. Heavy oils are also often more expensive to extract and so have higher production costs too. Transportation costs are also often higher due to the viscosity having a negative impact upon pumping and the like. Heavy crude oil also faces environmental problems as the quantity of carbon dioxide released during burning is also much higher.

[0200] The process has many beneficial effects upon the matrix and/or upon the compounds within it. These include:

[0201] Breaking down one or more compounds present to smaller compounds—these may have increased commercial value and/or may be more mobile within the matrix;

[0202] Reducing the level of contaminants present in the water drawn off the system, other through breakdown those compounds or changing their form;

[0203] Changing the surface chemistry of the matrix or species which form the matrix—either in terms of the physical chemistry of the matrix itself or in terms of the ions or other species present at the surface or the charge level of the surface—these can promote better release of the hydrocarbons from the matrix.

[0204] In the FIG. 1 illustration, the process is shown providing in-situ processing of the hydrocarbon within a geological structure 1. The process can be used to treat a wide variety of structures or situations where hydrocarbons are present and would benefit from a degree of oxidation. The matrices can include soil, groundwater bearing matrices, aquifers or other forms of geological structure containing the hydrocarbons to those described, including oil sand situations. Many or even all of these situations include naturally occurring water within the matrices to be treated. The addition of water, in liquid, gaseous or steam form, before or during the proposed processing is also a possibility.

[0205] FIG. 5 illustrates a further embodiment of the invention in which the similar principles and elements of the process are deployed in a quite different situation again. In this case, a tank 300 is provided which contains a volume of hydrocarbons which are too heavy or too sour. Rather than blend this oil with a lighter oil (potentially imported to the country or transported a long way within the country) to produce a blended oil with a higher API, the process seeks to treat the heavy oil. Blending is effective to a degree, but requires the mixing of large volumes of expensive light oil with the heavy oil to reach a commercial product. This increases the costs of reaching that commercial product and involves material amounts of financial capital to secure and put through the process the lighter oil. Many countries which have the heavy oil do not have their own sources of light oils. If the hydrocarbon to be treated is devoid of water or low in water, then water may be added before and/or during processing. The water may be added as a liquid, gas or steam form.

[0206] In FIG. 5, the electrodes 302 are provided near the walls 304 of the tank 300. A smaller number of electrodes 306 are placed towards the centre of the tank 300. Again, voltage pulses, current pulses and the other features described for the invention are provided so as to provide the oxidation effects and breakdown the oil in the tank 300. In an alternative form, not shown, the walls of the tank act as one of the electrodes or as a series of electrodes. The tank 300 is provided with an outlet 308 which leads to a pump and return inlet 310 so as to circulate oil and cause the oil in the tank to mix and have homogenous properties. The residence time within the tank 300 is controlled so as to give the desired form for the oil produced from it. This light oil can be sold as is, and/or can be used in a subsequent blending processes, for instance to blend with volumes of untreated heavy oil from the same or different extraction locations. The tank 300 can be a specifically constructed processing tank or could be a tank normally used for storage purposes. The technique is suitable for use in relatively large tanks, such as tanks which are 30 m of more in diameter. Suitable provision may be provided for collecting and dealing with any off gassing arising from the processing.

[0207] As well as the vertically arranged electrodes discussed above, further electrodes 320 are provided in a similar regular array across the width and length of the tank 300. In this case a series of horizontally extending electrodes 320 are provided. These are connected to the same wiring system. They can be used to form pairs of electrodes amongst themselves and/or be combined with vertically provided electrodes 302. These electrodes are provided at a depth d below the surface of the volume of material. These electrodes can be provided in a fixed position within the tank 300 or can be raised and lowered within the tank 300 as desired. They are used in a similar manner to the vertical electrode operation described above. The combination of electrode arrangements is used to increase the volume of material being treated or in closer proximity to an electrode.

[0208] Tanks of the type illustrated above could be used at the extraction site, at intermediate storage locations receiving oil from multiple extraction sites, at initial blending installations or at refineries where other processing is also provided.

[0209] As well as the heavy oils discussed above, the embodiment illustrated in FIG. 6 shows the invention in use at an extraction site which is concerned with oil sands (including tar sands and bituminous sands). Such deposits are to be found in Canada, Russia and Kazakhstan. They generally consists of loose sand or partially consolidated sandstone which contains viscous hydrocarbons (often classified as bitumen) as well as the matrix of sand, clay and water. In this embodiment, the array of electrodes 400 are driven into the ground 402 over the area 404 to be treated and the same type of general processing using the voltage pulse profiles and current pulse profiles is provided.

[0210] The viscosity of the hydrocarbons may be too high to achieve any transport at the outset and so no net transport effect may be provided to begin with. With time, the processing breaks the hydrocarbons down and reduces the viscosity. In a further phase, a net transport effect may be provided, using the voltage pulse profiles of a different form and/or using other transport mechanisms, such as “cold heavy oil production with sand” or “cyclic steam stimulation” or “steam assisted gravity drainage” or “vapour extraction” or “toe to heel air injection” or other such techniques for extraction assistance which are known in the art.

[0211] FIG. 7 shows a further situation in which the treatment process is provided. In this case, the treatment is provided during transportation. A form of on-line blending is provided. However, rather than add to the pipe 500 providing the transportation of the oil 502 different types of oil and allowing those to mix as they pass along the pipe 500, this embodiment of the invention applies the invention's processing during transportation. Thus, the pipeline 500 is provided at periodic intervals with a series of electrodes 504 inside the pipe and in contact with the oil 502. The processing is achieved in the same manner. A variety of electrodes 504 can be used including elongate electrodes of the type illustrated above, mesh or grid style electrodes extending across the cross-section of the pipe 500 or others. The aim is to apply the conditions to the oil as it passes and give a reduction in density and in viscosity, an increase in value and easier handling, pumping and transportation of the oil 502. Again, if the hydrocarbon to be treated is devoid of water or low in water, then water may be added before and/or during processing. The water may be added as a liquid, gas or steam form.

[0212] FIG. 8 illustrates the variation observed in a number of characteristics of a mixture when treated according to the method of the present invention over an extended time (in hours) on the x axis.

[0213] At the start of the method, the heavier hydrocarbons (black line) are present at a concentration of over 200,000 mg/kg of the mixture. As the method is performed, the method serves to breakdown the heavier hydrocarbons to lighter forms and so the concentration declines. The method reduces the concentration to around ¼ of its original value.

[0214] At the start of the method, the lighter hydrocarbons (red line) formed a relatively small part of the mixture and hence the concentration is low at less than 20,000 mg/kg of mixture. As the process converts the heavier hydrocarbons to lighter hydrocarbons, then this concentration increases. The method increases the concentration to around 10 times its original value.

[0215] FIG. 9a illustrates a preferred current pulse profile for some methods. Each cycle includes a positive polarity triggered current part 500 and a negative polarity triggered reverse current part 502. The current part 500 is formed of a first section 504, second section 506, fourth section 508 and third section 510 which occur in that sequence. Matching but reversed sections are provided for reverse current part 502, such that it has a first reversed part 512, second reversed part 514, fourth reversed part 516 and third reversed part 518. The next positive current part would then be present as the cycle is repeated over and over by the application of an appropriate voltage pulse profile (not shown).

[0216] FIG. 9b shows the peak part of the pulse in more detail. The first section 504 shows the current increasing quickly as it is encouraged by the change in the voltage pulse profile. As a result the voltage induced current and the current caused by the discharge of the capacitance built up during the previous reversed current part (not shown) occurs. These two current elements rapidly cause the peak current 520 to be reached.

[0217] As the capacitance of the system is discharged, then the current element from that diminishes in a curved decay through the second section 506. The voltage pulse still maintains a current though. Once the capacitance has effectively discharged, then the second section 506 transitions into the fourth section 506. The steady current occurs through the fourth section 506 before a further change in the voltage pulse (not shown) causes the rapid reduction of the current to zero during the third section 508, shown in FIG. 9a. A similar or matching peak occurs for the reverse polarity part and so on through the cycles.

[0218] The voltage pulse profile can be used to control the shape and timing of all of the sections of the current pulse profile.