Water Base Fracturing Fluids for Deep Lava Gas-Bearing Reservoir Stimulation

In hydrofracturing operations for stimulating the deep lava gas-bearing reservoirs in faut depression Xujiaweizi,Daqing,in which the highest formation temperature 170℃ and the largest layer thickness 120 m,the proppant load might be larger than 100 m~3 and an operation—be prolonged to 2.5—3.0 hrs using the fracturing units presently available thus outstanding water base fracturing fluids(WBFFs) are needed.A series of such WBFFs for use at different formation temperatures of 120—170℃ are developed and the basic recept is presented as follows: 0.55—0.65% hydroxypropyl guar gum,0.10—0.15% surfactant ZP-1,0.25—0.30% titanium/bor organic high temperature crosslinker, 0.002—0.003% persulfate gel breaker,and others(clay,gel,and temperature stabilizers,crosslinking controller,filtrate loss reducer etc).The performance properties of the WBFF for 150℃ are pesented: apparent viscosity is of 80 mPa·s when having been sheared over 4 hrs at 150℃ and 170 s~(-1);initial filtrate loss is of 3.13×10~(-4) m~3/m~2 and filtration coefficient—4.59×10~(-4) m/min~(1/2);for the brokendown WBFF at 150℃,the viscosity is of 5.6 mPa·s,the surface tension—30.96 mN/m and the interfacial tension with kerosene—1.83mN/m;the friction loss of the WBFF is decreased by 30% along the flow path in a field fracturing operation with the help of crosslinking control.Since 2002,these fluids have been used successfully in stimulating 24 reservoir layers in 12 deep gas wells in Xujiaweizi with the largest proppant load 100 m~3 and also in hydrofracturing 2 deep exploratory wells for gas in Jilin.