Patent Application
20140336088
The present application claims priority under 35 U.S.C. §119 to Chinese patent application 201310172790.7, filed May 10, 2013, the disclosure of which is incorporated herein by reference.
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1. Related Technical Field
The present invention relates to an instant-dissolving liquid polymer fracturing fluid thickener, or a liquefied thickener hereafter.
The present invention also relates to a method for preparing the liquefied thickener.
2. Background
Water-based fracturing fluid is among most critical technologies in improving oil/gas recovery. During a water-based fracturing process, solid fracturing fluid thickener consisting fine powders, such as guar gum powders, dry powders of synthetic polymer thickeners, are commonly used. Said thickeners' dispersing and hydrated tackifying capacities determine applications of the fracturing process, its fracturing quality and costs.
Currently, the fracturing process could be generally described as follows:
The first step, preparing a base fluid. Thickener powders are dispersed in water, then after a certain period of time they are fully swelled to form the base fluid having a certain viscosity;
The second step, conducting the fracturing process. The base fluid is mixed with a crosslinker and other agents to form the fracturing fluid.
The above 2-step of the fracturing process has following problems:
In order to overcome above shortcomings, technologies of diesel-based and water-based liquefied thickeners have been researched since 1980s. In 1993, Xi'an University and Tuha Oilfield cooperative researched and developed a low-residue boron crosslinked liquid guar gum fracturing fluid technology which may be used for on-site construction.
With the current increasing demands for the water-based fracturing fluid of guar gum, raw materials of guar are in shortly supply and their prices have gone up because its growth conditions restrict its planting area. Therefore, applications of the synthetic polymeric fracturing fluid thickener are gradually expending because of its thickening ability, gel breaking performance, less residue, and higher recovery rate. In order to overcome the shortcomings of the 2-step fracturing process and the guar gum, a novel technology for liquidating the synthetic polymeric fracturing fluid thickener may be needed.
An objection of the present invention is to provide a instant dissolving liquefied thickener.
Yet another objection of the present invention is to provide a method of preparing the liquefied thickener.
according to the present invention, the liquefied thickener has following evaluating indexes:
Said liquefied thickener is prepared by following steps:
According to one embodiment of the present invention, the synthetic polymer thickener has a formula as:
According to the present invention, the gelling time of said liquefied thickener is the time period for hydrating, swelling and dispersing processes.
Accordingly, the present invention has the advantages as follows:
1) No residue: during the whole fracturing process there is no residue of the liquefied thickener, therefore it is a low-damage fracturing fluid system.
2) Superior stability and performance of a fracturing fluid including: thermal-resistance, salt-resistance and shear-resistance; superior sand carrying and suspending capacities; reduced friction ratio, high rates of gel breaking and flowing back.
3) Ultra-fast instant dissolving: the hydrating, swelling and dispersing processes may be completed once thus the fracturing fluid may be prepared by a continuous operation with simply settings and equipment; the continuous operation allows the fracturing fluid to be mixed with sand and pumped immediately after prepared, thus eliminate on-site storages and liquid container for the reserves.
4) Simply preparation: the preparation of the present invention reduced components and steps of preparing, thus achieves high stability, high efficiency, low laboring, and simplified quality control.
5) Low cost: the preparation of the present invention minimizes requests for the equipment, which may be easy for relocation; its operation may be totally depended on demand, thus eliminates leftovers and prevents wasting; it reduces request for laboring and material costs, thus reduces overall costs.
Table 1A&B are lists showing components that might be applied to one embodiment of the present invention showing in
The present invention is related to a liquefied polymer fracturing fluid thickener (hereafter “liquefied thickener”). Said liquefied thickener is a homogeneous mixture of a synthetic polymer thickener and water-soluble organic solvent solution. Said synthetic polymer thickener (hereafter also termed “thickener powder”) is described in Chinese patent application having an application No. 201110223102.6.
Accordingly, the thickener powder has a molecular structure as:
Accordingly, the liquefied thickener disclosed and prepared by the present invention is a milky dispersion, wherein the thickener powder may consist up to 60% of the dispersion by weight thus it is highly concentrated. Said liquefied thickener includes following theoretical basis:
First, the thickener power is a synthetic water-soluble polymer, which is one of polymer-based fracturing fluid thickeners. The thickener powder is introduced with side groups which may form multi-level structures. After prepared into a fracturing fluid, its diluted solution contains a strong physical structure and may replace guar gum-based fracturing fluids. Because polymer structures of said thickener powder contain a large quantity of hydrophilic groups, which lead to excellent solubility and no insoluble objects remaining once dissolved, there is no residue produced during processes of preparation, crosslinking, gel breaking and flowing back. The multi-level structures of the side groups and the hydrophilic groups work together to produce the fracturing fluid with superior suspending capacity, reduced friction, and excellent thermo and salt resistances; all of which are especially suited for in situ operations, particularly, fracturing operations in large scales.
Second, a dissolution process of the thickener powder may be divided into five steps:
The first three steps, hydrating, swelling and dispersing are of most time-consuming and require sufficient stirring. The liquefied thickener of the present invention contains a plurality of water-soluble organic solvents; it is highly hydrophilic thus it may carry fine powders of the thickener powder and instantly disperse into water without introducing “fish eyes”, resulting in reduced time requests for the first hydrating and the third dispersing steps. The thickener power has been homogeneously dispersed among the water-soluble organic solvents, thus leads to an increased specific surface area with the large quantity of the hydrophilic groups. It may instantly integrate with water thus result in a quick swelling, and reduced time request for the second swelling step.
In summary, the liquefied thickener of the present invention may preliminarily eliminate three most time consuming steps during the dissolution process for the thickener powder, wherein said liquefied thickener may be able to substantially form a solution within few seconds after mixed with the water, instantly tackify said solution, which then could be mixed with sand, crosslinked, and pumped, leading to a continuous process for preparing and applying of the fracturing fluid.
In one embodiment, the present invention is a method of preparing the liquefied thickener comprises following steps:
The first step: preparing the water-soluble organic solvent:
According to the present invention, the sulfoxide based organic solvents may include but not limited to at least one of the following: dimethylsulfoxide, sulfoxide, and n-butyl sulfone. The amide based organic solvents may include but not limited to at least one of the following: dimethyl formamide, dimethyl acetamide, and diethyl formamide. The organic alcohols consist of mono-hydroxy alcohol organic solvents and/or polyhydroxy alcohol organic solvents. The mono-hydroxy alcohol organic solvents may include but not limited to at least one of the following: ethanol, n-propanol, iso-butanol and the like. The polyhydroxy alcohol organic solvents may include but not limited to at least one of the following: ethylene glycol, propylene glycol, glycerin and the like. The formate based solvents may include but not limited to sodium formate, and potassium formate.
Compounds introduced into the water-soluble organic solvent have their functions described as: the sulfoxide based organic solvents are a key organic solvent; the amide based organic solvents are a secondary organic solvent; the organic alcohols are solubility modifiers; the formate salt based solvents are performance moderators.
Step two: add the thickener powder of 200-600 mesh:
Accordingly, giving the total weight of the water-soluble organic solvent and the thickener powder in the Step two as 100%, the water-soluble organic solvent is 40-55%, and the thickener powder is 45-60% by weight.
The liquefied thickener of the present invention has a certain viscosity, it may be stratified after left standing for a while but may regain its homogeousness with a quick stirring. Said liquefied thickener has its evaluating indexes as: density of 1.0-1.3 g/cm3; gelling time less than or equal to 15 s; and the viscosity of its 1.0% solution greater than or equal to 30 mPa·s.
The viscosity of the liquefied thickener described hereabove is obtained by measuring its viscosity at 170 s−1 using a rheometer (such as Haake Rheometer or equivalent instrument) or a six-speed rotational viscometer.
Embodiment 1, preparing and testing Liquefied thickener 1:
The Liquid Thickener 1 prepared from the Embodiment 1 is a milky dispersion having a density of 1.13 g/cm3; gelling time 15 s; and the viscosity of its 1.0% solution 42 mPa·s.
Embodiment 2, preparing and testing Liquefied thickener 2:
The Liquid Thickner 2 prepared from the Embodiment 2 is a milky dispersion having a density of 1.24 g/cm3; gelling time 15 s; and the viscosity of its 1.0% solution 56 mPa·s.
Embodiment 3, preparing and testing Liquefied thickener 3:
The Liquid Thickner 3 prepared from the Embodiment 3 is a milky dispersion having a density of 1.18 g/cm3; gelling time 15 s; and the viscosity of its 1.0% solution 48 mPa·s.
It is to be understood that the use of “including”, “comprising” or “consisting of” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items; the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item; and, the use of terms “first”, “second”, and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.
It is to be understood that the above embodiments and examples are provided as illustrations only, and do not in any way restrict or define the scope of the present invention. Various other embodiments may also be within the scope of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201310172790.7 | May 2013 | CN | national |
