Patent Application
20070287638
The biopolymer component according to the present invention should preferably be a polysaccharide prepared by fermentation, members of the series consisting of scleroglucan, welan gum, diutan, rhamzan and succinoglycan being regarded as being particularly suitable.
In connection with the oil and gas exploration applications essential to the invention, those aqueous liquid phases which constitute a drilling fluid are particularly suitable. The observed effect of the increase in the thermal stability is observed to be particularly pronounced in the case of dicarbonyls if this drilling fluid preferably contains fresh water and/or sea water. Particularly preferably, it should be a salt-containing system of the “brine” type. However, the present invention also includes a variant in which the drilling fluid is an oil-containing emulsion or an invert emulsion.
From the series of the suitable dicarbonyl components which effect the increase in the thermal stability of biopolymers, dialdehydes, such as malonaldehyde CH2(CHO)2, succinaldehyde C2H4(CHO)2, glutaraldehyde C3H6(CHO)2 and preferably the simplest member, glyoxal CHOCHO, have proved to be particularly suitable. Furthermore, certain diketones, such as, for example, dimethylglyoxal (COCH3)2 or acetylacetone CH2(COCH3)2, are also claimed as typical members of the dicarbonyls in the context of this invention. However, dicarboxylic acids and their derivatives, namely salts, esters and ethers, are also preferred dicarbonyl components. Overall, it should be stated that compounds having vicinal carbonyl groups have proved to be particularly suitable. In addition to these α-dicarbonyl compounds, however, β-dicarbonyl compounds, such as, for example, malonic acid, also fulfil the purpose according to the invention.
The present invention also comprises that the dicarbonyl component is admixed with the liquid phases independently of its chemical composition, although a variant in which the dicarbonyl component is incorporated into the biopolymer in the course of the preparation of said biopolymer is being regarded as being particularly preferred.
The effect, according to the invention, of the dialdehyde component, namely the increase in the thermal stability, can be additionally increased by using, in addition to the dicarbonyl component, other compounds which serve for stabilizing the drilling fluid, in particular the biopolymers present therein, and especially for increasing the thermal stability thereof. From the series of the suitable compounds, in particular “oxygen scavengers”, such as, for example, lignosulfonates and tannates, may be mentioned at this point. Preferably, sodium sulfite, sodium bisulfite or formates, i.e. salts of formic acid, which are generally known as reducing agents (cf. “Composition and Properties of Drilling and Completion Fluids”, 5th Edition, Darley H. C. H. & Gray G. R., Gulf Publishing Company, Houston, Tex., Pages 480 to 482) are also suitable. However, primary, secondary and tertiary amines and in particular triethanolamine are suitable as well.
It should also be noted that the performance of said “oxygen scavengers” or radical scavengers, such as, for example, sodium sulfite, can additionally be markedly increased by Fe2+, Ni2+ or Co2+ salts. These salts presumably act as free radical mediators and thus catalyse the binding of free oxygen radicals.
The use according to the invention is in principle not bound to any defined temperature range, but the effect of thermal stability is particularly pronounced if the temperatures in the rock formation are >250° Fahrenheit, preferably >75° Fahrenheit and particularly preferably >300° Fahrenheit.
In summary, it remains to be stated that dicarbonyls are surprisingly excellently suitable for increasing the thermal stability of biopolymers in aqueous liquid phases which are used in oil and gas exploration. The success of the use according to the invention is therefore all the more unexpected since compounds having dicarbonyl features cannot be assigned to the classes of compounds known to date which are already known to increase the thermal stability of biopolymers markedly.
The following examples illustrate the advantages of the present invention.
The properties of the respective drilling fluids were determined according to the methods of the American Petroleum Institute (API), guideline RP13B-1. Thus, the rheologies were measured using an appropriate FANN 35 viscometer at 600, 300, 200, 100, 6 and 3 revolutions per minutes [rpm]. As is known, the measurements at the slow speeds of 6 and 3 rpm are particularly relevant with regard to the structural viscosity and carrying capacity of the fluids. In addition to this, the so-called “low shear rheology” was also determined using a Brookfield HAT viscometer at 0.5 rpm. Specifically, the measurements were conducted in each case before and after a thermal treatment (“ageing”) over 16 hours in a roller oven customary in the industry, at the temperatures stated in each case.
The increase in the temperature stability of a salt-containing aqueous solution of scleroglucan by glyoxal is described. The scleroglucan component used was the BIOVIS® product from Degussa Construction Polymers GmbH (comparison); in the experiments according to the invention, the BIOVIS® product contained an amount of <1% of glyoxal (“+G”) in addition to scleroglucan.
350 ml of an NaCl-saturated aqueous solution (109 g of NaCl and 311 g of water) were initially introduced into a Hamilton Beach Mixer (HBM) customary in the industry, at “low” speed. Thereafter, 3.5 g of the respective BIOVIS® component and 1 g of sodium sulfite (stabilizer) and 1 ml of tributyl phosphate (antifoam) were added. After stirring for 20 minutes in the HBM, the rheology was measured at a temperature of 140° F. (BHR=before hot roll). Further rheology measurements at 140° F. were effected after thermal loading over 16 hours at the ageing temperatures of 300 to 350° F. stated in each case (AHR=after hot roll).
Firstly, the data makes it clear that moderate temperatures up to 300° F. even improve the rheological performance of scleroglucan. However, this is purely a hydration effect in salt-saturated “brines”; i.e. the biopolymer goes completely into solution only under a thermal conditioning. This subsequent dissolution is less pronounced in the case of BIOVIS®+G (invention) since this glyoxal-containing type is very readily soluble from the beginning and at customary ambient temperatures.
Finally the further experimental series at demanding temperatures of 300 to 350° F. substantiates the improvement of the thermal stability by the presence of a glyoxal, which is found according to the invention.
The increase in the thermal stability of a calcium chloride-loaded, aqueous solution of scleroglucan by glyoxal is described. The scleroglucan component used was the BIOVIS® product from Degussa Construction Polymers GmbH (comparison); in the experiments according to the invention, the BIOVIS® product contained an amount of <1% of glyoxal (“+G”) in addition to scleroglucan.
350 ml of a CaCl2-containing aqueous solution (155 g of CaCl2 and 307 g of water) were initially introduced into a Hamilton Beach Mixer (HBM) customary in the industry, at “low” speed. Thereafter, 3.5 g of the respective BIOVIS® component, 1 g of sodium sulfite (stabilizer), 0.25 g of FeIISO4 as a free radical mediator and 1 ml of tributyl phosphate (antifoam) were added. After stirring for 20 minutes in the HBM, the rheology was measured at a temperature of 140° F. (BHR=before hot roll). Further rheology measurements at 140° F. were effected after thermal loading over 16 hours at the ageing temperatures of 300 to 350° F. stated in each case (AHR=after hot roll).
Once again, the data, particularly at the very demanding temperatures above 300° F., substantiate the improvement in the thermal stability by the addition of glyoxal, which was found according to the invention.
Increasing the thermal stability of an aqueous solution of welan gum by addition of glyoxal is described. The welan gum component used was the product BIOZAN® from CP Kelco. Glyoxal was used in the form of a commercially available 40% aqueous solution. Furthermore, the fluid was contaminated by addition of a freshly prepared cement slurry in order to simulate the conditions of use as “spacer fluid”.
350 ml of water were initially introduced into a Hamilton Beach Mixer (HBM) customary in the industry, at “low” speed. 3.5 g of BIOZAN® and 1.0 g of Na2SO3 (stabilizer) and 1 ml of tributyl phosphate (antifoam) were added. 0.35 ml of glyoxal solution was added to one of the two batches of this type which were prepared simultaneously (invention). Thereafter, in each case 50 g of a cement slurry (consisting of 800 g of class H cement from Lafarge and 304 g of water, stirred beforehand for 20 min in an atmospheric consistometer at 60° C.) were mixed in. After stirring for 20 minutes in the HBM, the rheology was measured at a temperature of 140° F. (BHR=before hot roll). Further rheology measurements were effected after thermal loading over 4 hours at 300° F. (AHR=after hot roll).
Once again, the data substantiate the improvement of the thermal stability by the addition of glyoxal, which is found according to the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 029 265.0 | Jun 2006 | DE | national |
