| 摘要 |
A continuous process of hydraulic fracturing of a well with in situ nitrogen foam generation, comprising the steps of: (a) preparing an aqueous solution of NH4Cl having a concentration of from 2.0-6.0M; (b) preparing an aqueous solution of NaNO2 having a concentration of from 6.0-9.0 M; (c) preparing an aqueous solution of acetic acid having a concentration of about 40% v/v; (d) adding hydroxyethylcellulose (HEC) to said NH4Cl solution at a concentration of from 0.3-1.2% w/v to form a viscosified NH4Cl solution; (e) simultaneously pumping said viscosified NH4Cl solution and said NaNO2 solution to form a mixture having a equimolar amounts of NH4Cl and NaNO2 thereby initiating an equimolar reaction between the components of said mixture; (f) pumping the acetic acid solution into the equimolar mixture of NH4Cl solution and NaNO2 solution, so as to initiate foam generation, while keeping the pH of the mixture between 4.75 and 5.50; (g) injecting a cushion of the generated foam into the well (pre-flash); (h) initiating the fracturing of the formation by injecting foam to which is added sand as a propping agent, said agent being added to the viscosified NH4Cl solution, in amounts varying from zero to 0.92 kg/l of the foaming mixture; and (i) after the fracturing, injecting in the well a cushion of sand-free foam (over-flash) of the same composition as the fracturing foam.
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