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青海涩北气藏地层压力系数在1.3左右,盐敏性强,临界矿化度为8×104mg/L。针对该气藏及类似油气藏研制了中高密度(1.05~1.70 g/cm3)VES压裂液。讨论了VES压裂液的形成及破胶机理。压裂液密度由盐水提供,给出了盐水密度与无机盐种类、浓度关系式。所用表面活性剂是专门研制的,代号CFP-Ⅲ,在基本配方中用量15~40 g/L。密度1.30 g/cm3、CFP-Ⅲ浓度30 g/L的VES压裂液的性能如下:20℃下的流变性显示剪切变稀特性;在20~45℃粘度基本恒定,在45~90℃粘度随温度上升而增大,>90℃后粘度下降,在110℃时为53 mPa.s,因此该VES压裂液可用于120℃地层;在20℃1、70 s-1下剪切60分钟使粘度降低25%,继续剪切时粘度不变;加入0.5%多烃类处理剂时彻底破胶,破胶液粘度与盐水相当;对储层岩心渗透率的伤害率仅为6.08%~11.14%。使用该VES压裂液在涩北13口气井进行压裂防砂先导性试验,气井不出砂日产气量增加75%~180%;给出了一口井的施工参数曲线图。图7表1参6。
The formation pressure coefficient of the Sebei gas reservoir in Qinghai is about 1.3 with strong salt sensitivity and a critical salinity of 8 × 104 mg / L. A medium to high density (1.05 ~ 1.70 g / cm3) VES fracturing fluid was developed for this reservoir and similar reservoirs. VES fracturing fluid formation and gel breaking mechanism are discussed. The fracturing fluid density is provided by the brine, and the relationship between the brine density and the type and concentration of inorganic salts is given. Surfactants used are specially developed, code-named CFP-III, the amount of 15 ~ 40 g / L in the basic formula. VES fracturing fluids with a density of 1.30 g / cm3 and a CFP-III concentration of 30 g / L have the following properties: Rheology at 20 ° C shows shear thinning properties; viscosity at 20-45 ° C is essentially constant at 45-90 ° C The viscosity increases with increasing temperature, and the viscosity decreases after> 90 ° C, which is 53 mPa.s at 110 ° C. Therefore, the VES fracturing fluid can be used in 120 ° C formation; sheared at 20 ° C at 1, 70 s-1 60 Min viscosity will be reduced by 25%, continue to shear the same viscosity; adding 0.5% more hydrocarbon agent completely broken plastic, broken gel viscosity and brine equivalent; damage to the permeability of reservoir core is only 6.08% 11.14%. Using this VES fracturing fluid, pilot production of fracturing and sand control was carried out in Sebei 13 gas well, gas production was increased by 75% -180% with respect to gas without sand production. The construction parameter curve of a well was given. Figure 7 Table 1 参 6.