Clean fracturing fluid thickener of multi-block associative copolymer (apcf) and method preparing thereof

A Clean Fracturing Fluid Thickener of Multi-block Associative Copolymer (APCF) having evaluating indicators described as:

• a viscosity of its 0.3% water solution at 20° C.≧30 mPa·s, a viscosity of said solution after gel breaking≦5 mPa·s, and, a static sand-suspending time of said solution≧10 min;
• prepared by a process comprising the steps of:
• (i), preparing multi-block associative monomers;
• said monomers all have a length of carbon chains between 8 and 22 and are selected from following:
• maleic acid n-alkyl ester sodium salt, n-alkyl acrylamide, n-alkyl dimethylallyl ammonium chloride or n-alkyl dimethyl p-methyl-phenylethenyl ammonium chloride, and/or dimethyl-n-alkylamine.
• wherein preparing the maleic acid n-alkyl ester sodium salt further comprises steps:
• (a) maintaining a temperature within a reactor at 10-30° C., (b) adding by total weight:
• 49.5-56.9% of methylbenzene, and 12-14% of maleic anhydride, stirring till dissolved, (c) adding by total weight:
• 26-30% of alcohol having the length of the carbon chains between 8 to 22, and 0.1-0.5% 4-methylbenzensulfonic acid, stirring till dissolved, (d) sealing the reactor air-tight, (e) raising the temperature within the reactor to 60-80° C. to initiate a reaction, (f) neutralizing the reaction by alkali 5-6% by total weight, (g) cooling down the reaction to a room temperature, and, (h) filtering the reaction to collect the maleic acid n-alkyl ester sodium salt,
• wherein preparing the n-alkyl acrylaminde further comprises steps:
• (a) maintaining a temperature of a reactor at 10-30° C., (b) adding by total weight:
• 45.1-51.9% of methylbenzene, and 38-42% of long chain alkyl amine having the length of the carbon chains between 8-22, stirring till dissolved, (c) adding by total weight 10-12% of acrylic acid, 0.1-0.5% of 4-methylbenzenesulfonic acid, stirring till dissolved, (d) sealing the reactor air-tight, (e) raising the temperature of the sealed reactor to 85-95° C. for reacting, (f) removing water from the reactor, (g) distilling by a reduced pressure distillation at 80-90° C. until no distillates distilled, (h) collection the n-alkyl acrylaminde from the reactor,
• wherein preparing the n-alkyl dimethylallyl ammonium chloride or the n-alkyl dimethyl p-methyl-phenylethenyl ammonium chloride comprises steps:
• (a) maintaining a temperature of a reactor at 10-30° C., (b) adding following components by total weight:
• 30-32% of ethanol, and 48-50% dimethyl-n-alkylamine having the length of the carbon chains between 8-22, stirring till dissolved, (c) adding following components by total weight:
• 18-22% chloroacrylate or 1-(chloromethyl)-4-ethenyl-benzen, stirring till dissolved, (d) sealing the reactor air-tight, (e) raising the temperature of the reactor to 50-60° C., (f) distilling by the reduced pressure distillation at 80-90° C. until no distillate distilled, and, (g) collecting the n-alkyl dimethylallyl ammonium chloride or the n-alkyl dimethyl p-methyl-phenylethenyl ammonium chloride from the reactor;
• and,
• (ii), synthesizing the Clean Fracturing Fluid Thickener of Multi-block Associative Copolymer (APCF), wherein synthesizing the Clean Frac Fluid Thickener of Multi-block Associative Copolymer (APCF) further comprises steps:
• (a) maintaining a temperature of a stirring reactor at 10-30° C., (b) adding by order and by total weight:
• 75% of de-ionized water, 20-35% of at least two water-soluble monomers containing vinyl groups, and 5-10% of two or more of the associative monomers, stirring till dissolved, (c) adding by total weight:
• 0.1-0.5% of redox initiators and 0.1-0.5% of azo-initiators, wherein the redox initiators consist of oxidizers and reducers, (d) raising the temperature of the stirring reactor at 80-95° C. for a multi-step initiation, and, (e) collecting polymers produced, which has a molecular weight between 200-400 million.