煤层气井用锆冻胶压裂液低温破胶体系

用于煤层压裂的锆冻胶压裂液是由无机锆(ZrOCl2)将聚丙烯酰胺(PAM)交联而成的,其优点是在低温下交联成冻。常规使用不同浓度的氧化体系(如过硫酸铵)破胶速度太慢,难以使压裂液在指定的时间内破胶水化,不利于压裂后返排,易对煤层造成伤害。为此,采用氧化还原体系在低温下破胶,研究了温度、聚合物浓度、交联剂浓度、氧化剂浓度、低温活化剂浓度、pH值、矿化度等因素对氧化还原体系低温破胶的影响。结果表明:在所选实验条件范围内,聚合物、交联剂浓度越高,加入盐的浓度越大,则越难破胶;氧化剂、低温活化剂浓度越高,pH值越高(2～5),越容易破胶。

A low temperature breaking system for zirconium gel fracturing fluids in coalbed methane gas wells

The aqueous polymer/zirconium gel used for fracturing in coalbed methane gas wells is formed by the cross link of poly acryl amide（PAM）and ZrOCl2, and its advantage is that the gel can be formed at low temperatures. However, the conventional oxidation gel breaking system breaks too slowly, which makes it difficult for the fracturing fluid to break down within the specified time and to flow back after fracturing. Meanwhile, it is easier to do damage to the coal beds. In view of this, an experimental study is made on the factors influencing the breaking time of redox system at low temperature, including temperature, polymer concentration, oxidizer concentration, deoxidizer concentration, pH value, and salinity, etc. The results show that under the conditions of this experiment, the higher the concentrations of the polymer, cross linker and salt, the more difficult for the gel to break, meanwhile, the higher the pH value (within the range of 2 - 5) , the easier for the gel to break.