Patent Application
20100210483
The present invention relates to a process for the removal of filtercakes formed in oil wells during drilling operations, by treating said filtercakes with aqueous solutions of particular oxidizing systems, also effective at low temperatures.
Increasing interest has been directed during the last few years towards the development of new drilling and servicing fluids capable of limiting damage to the productive formations induced by their use. This result is mainly due to the formation of filtercakes on the wall of the well, capable of reducing the inlet in the porous matrix of the fluids and solid used and/or products during the drilling of the well. When the well is put in production, however, the filtercake must be removed in a complete and homogenous manner to obtain high productivity values.
The removal technologies currently available are based on the use of various categories of chemical additives, for example, acids, chelating agents, enzymes, oxidants.
U.S. Pat. No. 5,607,905 describes a process for improving the removal of filtercakes by the use of inorganic peroxides as oxidizing agents. More specifically, the process of U.S. Pat. No. 5,607,905 envisages the incorporation in the filtercake of peroxides of alkaline earth metals or zinc followed by the subsequent treatment of the above filtercakes with acid solutions.
U.S. Pat. No. 5,247,995 describes a method for the removal of filtercakes containing polysaccharides, by treatment with aqueous solutions containing enzymes capable of degrading the polysaccharide or by treatment with an oxidant selected from non-metallic persulfates.
The methods which envisage the removal of filtercakes by the incorporation therein of solid precursors of oxidizing agents, are not entirely reliable as the above solids are not completely insoluble at the operating temperatures. Part of the oxidizing materials are therefore prematurely released with a consequent premature degradation of the polymers. These formulations, moreover, have two further disadvantages, i.e. they can only be used at high pH values and in the absence of significant quantities of reducing agents.
Finally, WO 00/08112 describes a process for the removal of filtercakes based on polysaccharides by treatment of the above filtercakes with saline solutions capable of generating bromine or bromate.
All these solutions to the technical problem of the removal of filtercakes have the drawback of functioning satisfactorily above all in vertical wells, characterized by high pressures and medium-high temperatures.
The necessity has therefore been felt in the art for finding solutions, which are equally if not even more effective, capable of also operating at medium-low temperatures and pressures, particularly in more or less depleted horizontal wells, characterized by medium-low pressures and temperatures.
A process has now been found which satisfies the above demands.
In accordance with this, the present invention relates to a process for the solubilization of polymeric material deposited on a porous medium, which comprises putting the above polymeric material in contact with an aqueous composition, the above aqueous composition comprising:
(a) a catalyst selected from:
(a1) a complex having general formula (I)
Fe++(L)n(Y)s (I)
wherein n is an integer selected from 1 to 3,
Y is independently a group of an anionic nature bound to Fe++ as anion in an ionic pair or with a covalent bond of the “σ” type;
“s” expresses the number of Y groups sufficient for neutralizing the formal oxidation charge of Fe++, and is equal to 2 if all the Y groups are monovalent;
L being a binder selected from those having general formula (II)
wherein X═CH, N;
R1 and R2, the same or different, are selected from —H, —COOH, and C1C5 alkyl radicals, preferably from H and COOH;
(a2) a hydrosoluble cobalt2+ salt, preferably cobalt acetate;
(b) an oxidizing agent selected from:
(b1) hydrogen peroxide,
(b2) MHSO5, wherein M is an alkaline metal, preferably potassium; with the constraint that the catalyst (a1) can only be used in the presence of the oxidizing agent (b1) and the catalyst (a2) can only be used in the presence of the catalyst (b2).
As far as the polymeric material is concerned, typical examples are polysaccharides, polyacrylamides, polyacrylic acid and relative copolymers; xanthan gum, amides with different cross-linking degrees, cellulose.
Typical examples of carboxylic acid binders having general formula (II) are pyridin-2-carboxylic acid, pyrazin-2-carboxylic acid, 2,6-pyridinedicarboxylic acid, 2,3-pyrazinedicarboxylic acid. The preferred compound having general formula (II) is pyridin-2-carboxylic acid.
The complex having general formula (I) can be preformed or, preferably, formed “in situ” by addition of the components, i.e. of the binder L and iron (II) salt. In this latter case, a molar ratio between binder and Fe++ ranging from 1/1 to 30/1, preferably from 1/1 to 10/1, can be used.
The oxidizing agent can be fed together with the aqueous solution (I), or subsequently or previously thereto.
When the oxidizing agent is hydrogen peroxide, an aqueous solution thereof at 5% by weight to 40% by weight, preferably from 10% by weight to 30% by weight, can be used.
The aqueous composition of the above invention has a content of Fe++ ranging from 0.5 to 10 millimoles/litre, preferably from 1 to 5 millimoles/litre.
Furthermore, when hydrogen peroxide is used, this is present in the final aqueous composition at a concentration ranging from 0.5 to 10% by weight, preferably from 1% to 5% by weight.
When the oxidizing agent is MHSO5, an aqueous solution thereof, preferably from 5 to 20% by weight, is also used in this case.
The considerable advantage of the process of the present invention lies in the fact that it is also effective at relatively low temperatures, i.e. from 25° C. to 60° C.
We would also like to point out that the process of the present invention, allows the initial permeability values to be re-established, as will be shown in the experimental part.
The efficacy of the process of the present invention was first examined under batch conditions, evaluating the time necessary for the reduction in the viscosity of the polymeric solutions or, in the case of amides, for the complete dissolution of the polysaccharide.
The experimental part describes tests effected according to the process of the present invention and comparative tests carried out in the presence of other oxidizing systems.
In particular, the following oxidants were evaluated: H2O2, KHSO5, (NH4)2S2O8, NaClO, tBuOOH and NaBO3.
The following catalysts were used: FeSO4, Co(OAc)2, Cu(OAc)2 or their complexes with nitrogenated binders (EDTA, phenanthroline, pyridin-2-carboxylic acid, pyrazin-2-carboxylic acid, 2,6-pyridinedicarboxylic acid, 2,3-pyrazinedicarboxylic acid), selected for their capacity of modifying the redox potential of the metal and for their high stability under oxidizing conditions.
Among all the various systems examined (see experimental part) only those of the present invention proved to be effective.
The effect of various types of brine (KCl 3%, CaCl2 25%, CaBr2 45%, HCOOK 20%) on the performances of the systems selected, were subsequently evaluated. This study showed that the oxidizing system based on hydrogen peroxide is also effective in the presence of brine.
In order to modulate the activity of the system based on hydrogen peroxide, studies were effected by varying the concentration of the catalyst and temperature. In this way, the degradation time of the polymers can be varied according to the demands. This is undoubtedly another considerable advantage of the present process.
The characterization of the products deriving from the oxidation was effected by ultra-filtration and GPC, revealing the complete disappearance of the polymers and the formation of low molecular weight fragments corresponding to 1-5 units of glucose.
The following examples are provided for a better understanding of the present invention.
Table 1 indicates the data relating to the degradation of xanthan gum in the presence of various oxidizing systems, possibly in the presence of catalysts (tests 1-24). The data specified in this table reveals the greater efficacy of the systems of the present invention.
Tables 2 (tests 25-29), 3 (tests 30-36), 4 (tests 37-41) and 5 (tests 42-46) respectively indicate the data of the degradation tests of scleroglucane, succinoglucane and two different starches, in the presence of the systems of the present invention. These tables also indicate various comparative tests.
Table 6 specifies the effect of the concentration of the catalyst on the degradation of scleroglucane with hydrogen peroxide catalyzed by the complex Fe/pyridin-2-carboxylic acid.
Table 7 indicates the effect of the temperature on the degradation rate in the presence of the system of the present invention.
Table 8 describes tests which show the effect of brine on the degradation time in the presence of the system H2O2/FeSO4/PyCOOH.
Finally, tests 60-62 refer to filtercake removal tests.
The degradation test was carried out using a solution of N-VIS® (supplied by Baroid), obtained by dissolving 1.2 g of polysaccharide in 200 ml of deionized water by means of a Silverson stirrer.
The initial value of the viscosity proved to be equal to 200, measured using a FANN 35 SA rotational viscometer at 5.1 sec−1 with a rotor-bob R1B1 configuration.
1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) were added to the resulting solution and the mixture was then maintained under static conditions at a temperature of 35° C.
The degradation rate was evaluated by measuring the time necessary for reaching a viscosity lower than 10 mPa·s.
Operating under the conditions described above, after 24 hours, the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, as catalyst (molar ratio oxidant/catalyst=18).
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 4 hours.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.51 g (1.74 mmoles) of EDTA (ethylenediaminotetra-acetic acid), as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 1 hours.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.34 g (1.74 mmoles) of 1,10-phenanthroline, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 4 hours.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 3 minutes.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.22 g (1.74 mmoles) of pyrazinecarboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 10 minutes.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.29 g (1.74 mmoles) of 2,6pyridinedicarboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 10 minutes.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.29 g (1.74 mmoles) of 2,3-pyrazinedicarboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 3 minutes.
The test was carried out under the same conditions described in Example 1, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent, in the absence of a catalyst.
Operating under static conditions at 35° C., after 24 hours, the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 1, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 16 hours.
The test was carried out under the same conditions described in Example 1, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 8 minutes.
The test was carried out under the same conditions described in Example 1, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.21 g (1.74 mmoles) of pyrazinecarboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 4 hours.
The test was carried out under the same conditions described in Example 1, using 2.3 g of ammonium peroxydisulfate [(NH4)2S2O8] (10.1 mmoles) as oxidizing agent in the absence of a catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 12 hours.
The test was carried out under the same conditions described in Example 1, using 2.3 g of ammonium peroxydisulfate [(NH4)2S2O8] (10.1 mmoles) as oxidizing agent and 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 2 hours.
The test was carried out under the same conditions described in Example 1, using 2.3 g of ammonium peroxydisulfate [(NH4)2S2O8] (10.1 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 4 hours.
The test was carried out under the same conditions described in Example 1, using 2.3 g of ammonium peroxydisulfate [(NH4)2S2O8] (10.1 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O and 0.22 g (1.74 moles) of pyrazinecarboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 2 hours.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and 0.15 g (0.60 mmoles) of Co(CH3COO)2.4H2O as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 10 hours.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.15 g (0.60 mmoles) of Co(CH3COO)2.4H2O and 0.21 g (1.74 moles) of pyridin-2-carboxylic acid as catalyst.
Operating under static conditions at 35° C., after 24 hours the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 1, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.15 g (0.60 mmoles) of Co(CH3COO)2.4H2O as catalyst. Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 3 minutes.
The test was carried out under the same conditions described in Example 1, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.15 g (0.60 mmoles) of Co(CH3COO)2.4H2O and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst. Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 7 hours.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 moles) as oxidizing agent and 0.12 g (0.60 mmoles) of Cu(CH3COO)2.H2O as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 30 minutes.
The test was carried out under the same conditions described in Example 1, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.12 g (0.60 mmoles) of Cu(CH3COO)2.H2O and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid as catalyst.
Operating under static conditions at 35° C., after 24 hours the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 1, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.12 g (0.60 mmoles) of Cu(CH3COO)2.H2O as catalyst.
Operating under static conditions at 35° C., after 24 hours the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 1, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.12 g (0.60 mmoles) of Cu(CH3COO)2.H2O and 0.22 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under static conditions at 35° C., after 24 hours the viscosity remained substantially unaltered.
The degradation test was carried out using a solution of BIOVIS (supplied by SKW Trostberg), obtained by dissolving 1.2 g of polysaccharide in 200 ml of deionized water by means of a Silverson stirrer.
The initial viscosity value proved to be equal to 200, measured using a FANN 35 SA rotational viscometer at 5.5 sec−1 with a rotor-bob R1B1 configuration.
1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) were added to the resulting solution and the mixture was then maintained under static conditions at a temperature of 35° C.
The degradation rate was evaluated by measuring the time necessary for reaching a viscosity lower than 10 mPa·s.
Operating under the conditions described above, after 24 hours, the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 25, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst (molar ratio oxidizing agent/catalyst=18).
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 20 minutes.
The test was carried out under the same conditions described in Example 25, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent without a catalyst.
Operating under static conditions at 35° C., after 24 hours the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 25, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O and 0.21 g (1.74 moles) of pyridin-2-carboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 1 hour.
The test was carried out under the same conditions described in Example 25, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.15 g (0.60 mmoles) of Co(CH3COO)2.4H2O as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 15 minutes.
The degradation test was carried out using a solution of FLOPAC® (supplied by Halliburton), obtained by dissolving 6.0 g of polysaccharide in 200 ml of deionized water by means of a Silverson stirrer.
The initial viscosity value proved to be equal to 450, measured using a FANN 35 SA rotational viscometer at 5.5 sec−1 with a rotor-bob R1B1 configuration.
1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) were added to the resulting solution and the mixture was then maintained under static conditions at a temperature of 35° C.
The degradation rate was evaluated by measuring the time necessary for reaching a viscosity lower than 10 mPa·s. Operating under the conditions described above, after 24 hours, the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 30, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 10 minutes.
The test was carried out under the same conditions described in Example 30, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 moles) as oxidizing agent without a catalyst.
Operating under static conditions at 35° C., after 24 hours the viscosity remained substantially unaltered.
The test was carried out under the same conditions described in Example 30, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 2 hours.
The test was carried out under the same conditions described in Example 30, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.15 g (0.60 mmoles) of Co(CH3COO)2.4H2O as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 10 minutes.
The test was carried out under the same conditions described in Example 1, using 2.3 g of ammonium peroxydisulfate [(NH4)2S2O8] (10.1 mmoles) as oxidizing agent in the absence of a catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 14 hours.
The test was carried out under the same conditions described in Example 1, using 2.3 g of ammonium peroxydisulfate [(NH4)2S2O8] (10.1 mmoles) as oxidizing agent and 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, as catalyst.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 1 hour.
The degradation test was carried out using a suspension of FLOTROL® (supplied by MI), obtained by adding 2 g of polysaccharide to 200 ml of deionized water.
1.2 g of hydrogen peroxide at 30% by weight (10.6 moles) were added to the resulting mixture which was then maintained under bland stirring at a temperature of 35° C.
The degradation rate was evaluated by measuring the time necessary for the complete dissolution of the polysaccharide.
Operating under the conditions described above, after 24 hours, the suspension remained substantially unaltered.
The test was carried out under the same conditions described in Example 37, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under the conditions described above, at 35° C., the time necessary for the complete dissolution of the polysaccharide proved to be equal to 50 minutes.
The test was carried out under the same conditions described in Example 37, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent without a catalyst.
Operating under the conditions described above, after 24 hours the suspension remained substantially unaltered.
The test was carried out under the same conditions described in Example 37, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst. Operating under the conditions described above, at 35° C., the time necessary for the complete dissolution of the polysaccharide proved to be equal to 3 hours.
The test was carried out under the same conditions described in Example 37, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.15 g (0.60 mmoles) of Co(CH3COO)2.4H2O as catalyst.
Operating under the conditions described above, at 35° C., the time necessary for the complete dissolution of the polysaccharide proved to be equal to 25 minutes.
The degradation test was carried out using a suspension of DUALFLO® (supplied by MI), obtained by adding 2 g of polysaccharide to 200 ml of deionized water.
1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) were added to the resulting mixture which was then maintained under bland stirring at a temperature of 35° C.
The degradation rate was evaluated by measuring the time necessary for the complete dissolution of the polysaccharide.
Operating under the conditions described above, after 24 hours, the suspension remained substantially unaltered.
The test was carried out under the same conditions described in Example 42, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 moles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O, and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under the conditions described above, at 35° C., the time necessary for the complete dissolution of the polysaccharide proved to be equal to 40 minutes.
The test was carried out under the same conditions described in Example 42, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent without a catalyst.
Operating under the conditions described above, after 24 hours the suspension remained substantially unaltered.
The test was carried out under the same conditions described in Example 42, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and the complex obtained by adding 0.16 g (0.58 mmoles) of Fe2SO4.7H2O and 0.21 g (1.74 mmoles) of pyridin-2-carboxylic acid, as catalyst.
Operating under the conditions described above, at 35° C., the time necessary for the complete dissolution of the polysaccharide proved to be equal to 1 hour.
The test was carried out under the same conditions described in Example 42, using 3.2 g of potassium monopersulfate (KHSO5) at 47% by weight (9.9 mmoles) as oxidizing agent and 0.15 g (0.60 mmoles) of Co(CH3COO)2.4H2O as catalyst.
Operating under the conditions described above, at 35° C., the time necessary for the complete dissolution of the polysaccharide proved to be equal to 20 minutes.
The test was carried out under the same conditions described in Example 26, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 moles) as oxidizing agent and the complex obtained by adding 64 mg (0.23 mmoles) of Fe2SO4.7H2O, and 84 mg (0.69 mmoles) of pyridin-2-carboxylic acid, as catalyst (molar ratio oxidizing agent/catalyst=46).
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 30 minutes.
The test was carried out under the same conditions described in Example 26, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 mmoles) as oxidizing agent and the complex obtained by adding 32 mg (0.12 mmoles) of Fe2SO4.7H2O, and 44 mg (0.36 mmoles) of pyridin-2-carboxylic acid, as catalyst (molar ratio oxidizing agent/catalyst=88).
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 4 hours.
The test was carried out under the same conditions described in Example 26, using 1.2 g of hydrogen peroxide at 30% by weight (10.6 moles) as oxidizing agent and the complex obtained by adding 16 mg (0.06 mmoles) of Fe2SO4.7H2O, and 22 mg (0.18 mmoles) of pyridin-2-carboxylic acid, as catalyst (molar ratio oxidizing agent/catalyst=177).
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 18 hours.
The test was carried out under the same conditions described in Example 26.
Operating under static conditions at 25° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 90 minutes.
The test was carried out under the same conditions described in Example 26.
Operating under static conditions at 50° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 10 minutes.
The test was carried out under the same conditions described in Example 29.
Operating under static conditions at 25° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 60 minutes.
The test was carried out under the same conditions described in Example 29.
Operating under static conditions at 50° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 8 minutes.
The test was carried out under the same conditions described in Example 38.
Operating under static conditions at 25° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 75 minutes.
The test was carried out under the same conditions described in Example 38.
Operating under static conditions at 50° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 6 minutes.
The test was carried out under the same conditions described in Example 26 by dissolving polysaccharide in 200 ml of an aqueous solution of KCl at 3% by weight.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 25 minutes.
The test was carried out under the same conditions described in Example 26 by dissolving polysaccharide in 200 ml of an aqueous solution of CaCl2 at 25% by weight.
Operating under static conditions at 35° C., the time necessary for lowering the viscosity to 10 mPa proved to be equal to 25 minutes.
The test was carried out under the same conditions described in Example 26 by dissolving polysaccharide in 200 ml of an aqueous solution of CaBr2 at 45% by weight.
Operating under the conditions described above, after 24 hours, the suspension remained substantially unaltered.
The decomposition of the CaBr2 was verified, with the formation of Br2.
The test was carried out under the same conditions described in Example 26 by dissolving polysaccharide in 200 ml of an aqueous solution of potassium formiate at 20% by weight.
Operating under the conditions described above, after 24 hours, the suspension remained substantially unaltered.
The decomposition of the potassium formiate was verified with the formation of CO2.
The initial permeability of a ceramic filter (diameter: 2.5″, thickness: 0.25″, porosity: 5 microns) was determined using a HTHP dynamic filterpress, measuring the time necessary for the passage of 200 ml of an aqueous solution of KCl at 3%, at a pressure of 7 bars, at 40° C.
The cell was then filled with a fluid having the following composition:
The formation of the filtercake was obtained by pressurizing the cell at a pressure of 21 bars, under stirring (600 rpm) for 30 minutes. After a washing with water, the removal of the filtercake was effected by adding, to the cell, a breaker solution having the following composition:
The solution was kept under static conditions for 4 hours at 40° C.
After washing with water, the residual permeability was determined by measuring the time necessary for the passage of 200 ml of aqueous solution of KCl at 3% at a pressure of 7 bars at 40° C.
The following results were obtained:
Initial permeability: 20 sec/200 ml
Final permeability: 20 sec/200 ml
Permeability recovery: 100%
The test was carried out under the same conditions described in Example 60, using however the following fluid for the formation of the filtercake:
After treatment with the breaker solution, the following results were obtained:
Initial permeability: 20 sec/200 ml
Final permeability: 20 sec/200 ml
Permeability recovery: 100%
The test was carried out under the same conditions described in Example 60, using however the following fluid for the formation of the filtercake:
After treatment with the breaker solution, the following results were obtained:
Initial permeability: 20 sec/200 ml
Final permeability: 20 sec/200 ml
Permeability recovery: 100%
| Number | Date | Country | Kind |
|---|---|---|---|
| MI2005A001559 | Aug 2005 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP06/07596 | 7/28/2006 | WO | 00 | 8/4/2008 |
