GB2212811A

GB2212811A - Increasing the filterability of a polysaccharide wort and its use in enhanced oil recovery

Info

Publication number: GB2212811A
Application number: GB8826391A
Authority: GB
Inventors: Christine Noik; Jacqueline Lecourtier; Guy Chauveteau
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 1987-11-13
Filing date: 1988-11-11
Publication date: 1989-08-02
Anticipated expiration: 2008-11-11
Also published as: DE3838352A1; CA1324776C; DE3838352C2; FR2623207A1; FR2623207B1; NO885031D0; GB2212811B; NO885031L; GB8826391D0; JPH01153787A

Description

1 1 PROCESS FOR PURIFYING A POLYSACCHARIDE WORT AND ITS USE IN ENHANCED

OIL RECOVERY 01 221281 1 The invention relates to a process for purifying polysaccharice worts in order to increase their filterability. It also relates to the improved fermentation wort which results from this process.

Polysaccharide worts are obtained with a well-known fermentation process: a micro-organism (fungus, bacterium) which produces polysaccharide, for example a Scleroglucane-producing fungus of the Sclerotium type, is grown in a nutrien aqueous medium containing a carbohydrate.

lized for the Sclerotium Rolfsii can, for example, be ut production of Scleroglucane. As for the production of Schizophyllane and of Xanthane, the Schizophyllum Commune fungus and the Xanthomonas Campestris bacterium can be respectively used.

After the fermentation, a fermentation wort comprising about 0.5 to 4% by weight of polysaccharide as well as salts, residual nutrient elements, cells or fungus residues and other insoluble compounds is collected.

The insoluble particles in the raw wort, such as cell residues, can be removed through filtration. This process has aroused many proposals. US Patent 4 337 157 for example suggests to filter on minerals of the calcium silicate or of the magnesium oxide type, which naturally have a basic pH. US Patent 4 119 491 suggests an enzymatical clarification-filtration which destroys and removes the cell residues.

After filtering, there still are some impurities of the proteinaceous type left, which cause the growth of macromolecule aggregates that are hard to filter, show a clogging behaviour and can obstruct the pores of the underground formations during enhanced recovery operations.

These residues of the proteinaceous type can be removed by heating the wort and then ultraf iltering, as suggested in US Patent 4 299 825,. or by heating and filtering as proposed y US Patent 3 355 447.

The results which have been obtained with the processes described above are not really performing.and another process, wnich will allow to obtain a polymer with a good filterability and, above all, a 2 filterability that will show stable in time, is necessary. DETAILED DESCRIPTION OF THE INVENTION

The process according to the invention for treating a polysaccharide wort which has been previously filtered in order to remove at least the main part of the cell or fungus residues from it comprises:

- Contacting the wort with a material of the siliceous type, for example silica gel, for instance by agitation or by letting flow through the siliceous material, at a temperature of at least 500C, for example 50-1300C.

The wort can either be a raw pre-filtered fermentation wort or a solution of a powdery polysaccharide that has been extracted from such a wort.

The preferred embodiments of the invention are described 15 hereafter:

At the time of the contact with the siliceous particles, the polymer concentration of the wort advantageously ranges from 0.5 to 100 g/l. The choice of the siliceous material is not determining and good results have for example been obtained with silica gels, 20 diatomaceous earths and natural sand.

During the treatment, the pH advantageously ranges from 5 to 11, preferably from 6 to 8, and the salinity preferably goes from 0.1 to 20 g/l, expressed in NaCl, of one or several alkali-metal salts. to 100 kg, preferably 5 to 40 kg of siliceous material per m3 of wort are 25 utilized.

The duration of the contacting and the heating temperature depend on the required result and on the nature of the polysaccharide: it preferably goes from 1 to 24 hours at 70-1100C for Scleroglucane and Schizophyllane, and from 5 to 60 minutes at 50-1100C for Xanthane.

The wort which is subjected to the treatment with a siliceous material has been previously cleared of the cell residues by an adequate treatment according to one of the well-known techniques, for example filtration on diatomaceous earth, in order to remove at leat 90% of the residues larger than 20wn and preferably at least 90% of the residues larger than 1 pm.

The following comparative examples illustrate the implementation of the invention.

Z) 4 3 EXAMPLE 1

The test relates to a wort that has been prefiltered on a diatomaceous earth with a particle size mainly grading between 10um and 801im. After the filtration, more than 90% of the residues larger than 10 um are thus removed. The Scleroglucane wort with a polymer concentration of 3 9/1 is directly contacted, at a temperature of 900C, wih silica particles with a specific surface of 200 m2/g at the rate of 40 kg of silica per M3 of wort. The contact duration is 24 hours. The solutions of wort before andafter the treatment (solutions Ia and IIa) are diluted with distilled water uhtil they reach a concentration of 250 ppm by weight and are subjected to a filterability test. This filterability test consists in injecting, under low shear rate conditions (y = 5 s-1) and at 900C, the polymer solution through a block of silicon carbide particles with a permeability of 400 m Darcy.

The mobility reduction (R) in the block is determined according to the filtered volume (V). The mobility reduction is the A P polymer/ A P water ratio, where 6 P polymer is the pressure drop for the polysaccharide solution and L P water is the pressure drop for the corresponding aqueous phase without polysaccharide.

Figure 1 shows the tests corresponding to a pre-filtered solution which has not been treated with the silica Ia but which has been treated according to invention IIa. It can be seen that the first solution quickly clogs the filters and that the treated solution shows an excellent filterability.

If the treatment described above is exactly repeated, except for the temperature which will be maintained at 300C, the filterability of the obtained product is not so good as that of the product which has been treated according to the invention, as shows curve IIIa of Figure 1. Again, if the treatment according to the invention, that is contacting with silica at 900C, is applied to a raw wort which has not been pre-filtered and contains fungus residues, the filterability of the raw wort is of the clogging type (curve IVa), which shows that it is necessary to remove the insoluble residues before carrying out the treatment according to the invention.

4 EXAMPLE 2

A raw Xanthomonas Campestris fermentation wort has been diluted in order to have a concentration of 500 ppm by weight. Its alkalimetal concentration has been brought to 5 g/l, expressed in NaCl, after 5 adding sodium chloride.

The polymer solution has been cleared of the bacterial cells larger than about 5 lim by filtration, brought to 600C and then contacted with silica particles (40 kg per m3) with a specific surface of 200 m2g. The contacting duration is 15 mn.

The solutions before and after the treatment are brought to a concentration of 300 ppm by dilution with a water comprising 5 g/1 of sodium chloride and subjected to a filterability test.

The filterability test consisted in injecting, under low shear rate conditions (y = 5 s-1) and at 300C, the polymer solution through three Millipore filters with an average pore diameter of 5 Ums and determining the mobility reduction (R) in the filters according to the filtered volume (V).

Figure 2 shows the results of the tests corresponding to a solution which has not been treated (Ib) and a solution which has been subjected to the treatment according to the invention (IIb). It can be seen that the first solution leads to a clogging of the filters whereas the solution treated according to the invention shows a constant R, that is an excellent filterability.

t

Claims

1. Process for treating a polysaccharide wort in order to increase its filterability, characterized in that the wort is first filtered to remove at least 90% of the solid residues larger than 20 #w and then contacted with a siliceous material at a temperature of at least 500C.

2. A process according to Claim 1, wherein the siliceous material comprises sand, silica or diatomaceous earth particles.

3.

wort.

A process according to Claim 1, wherein the wort is a Xanthane

4. A process according to Claim 1, wherein the wort is a 15 Scleroglucane wort.

5. A process according to Claim 1, wherein the wort is a Schizophyllane wort.

6. A process according to Claim 1, wherein the wort comprises at least one alkali-metal salt with a concentration from 0.1 to 20 g calculated in NaCl per litre.

7. A process according to Claim 1, wherein the wort is a 25 Scleroglucane or a Schizophyllane wort and the contacting with a siliceous material is carried out at 90-1100C for 1 to 24 hours.

8. A process according to Claim 1, wherein the wort is a Xanthane wort and the contacting with a siliceous material is carried out at 5030 1100C for 5 to 60 minutes.

9. A process according to Claim 1, wherein 1 to 100 kg siliceous material per m3 of wort is used.

10. A process according to Claim 1, wherein 5 to 40 kg siliceous material per m3 of wort is used.

6

11. A process according to Claim 1, substantially as hereinbefore described in Example 1 or 2.

PabIlshed. 1989 atThe Patent Office. State House,88.71 High Holborn. London. WC1R 4TP. Further copies maybe obtained from The PatentOffice. Was Branch, St MaT7 Cray, Orpington, Kent BM 3RD. Printed by Multiplex techniques Itd, St Mary Cray, Kant, Con- 1187