Preparation And Performance Evaluation Of CO 2 Switch Microemulsion

In the process of oil and gas field production assignments, the cleanup additive not only can promote the gel breaking liquid timely flowback, at the same time also can minimize the damage of formation. Due to the fluid flowback tend to produce large amounts of foam, this is a difficult problem for post-processing of gel breaking liquid. So this article with CO2 switchable microemulsion as a role of cleanup additive, in the process of fracturing can not only promote the fracturing fluid flowback timely and effectively, at the same time also can make the gel breaking liquid defoaming automatically when contact with CO2.N,N-dimethyl oleoaminde-propylamine (DO APA) was synthesized through Oleic acid and N,N-dimethyl-1,3-pro-panediamine. The structure of N,N-dimethyl oleoaminde-propylamine was confirmed by 1H NMR and FT-IR. With the Shah method, the water droplets were into the system mixture by sodium dodecyl sulphate (SDS)/n-hexane/n-butanol drop by drop. The pseudoternary phase diagram of miroemulsion was obtained. At the same time, we have choosed a formula (12.24% SDS,2.76% TMPDA,20% hexane,15% butanol and 50% water) at the single-phase microemulsion phase area in the pseudoternary phase diagram. Through the above formula, we have preparation a CO2-switchable W/O microemulsion. And its CO2 switch characteristics were studied by Zeta potential and Dynamic Light Scattering (DLS). The phase separation was occurred when bubbling CO2 after 15min at 25?, and the microemulsion was reformed when bubbling N2 with the same flow rate of CO2 at 50?. The nanoemulsion was obtained after diluted miroemulsion with purified water and the diameter of nanoemulsion is nearly 80nm. When bubbling CO2 into the nanoemulsion system at 25? the phase sepration happened immediately. Displacing CO2 with N2, after 3h the nanoemulsion was reformed at 50 ?. The CO2 switchability of nanoemulsion was measured by DLS, Conductivity and Zeta potential. Surface activity, wettability and fracturing fluid compatibility was measured, the microemulsion cleanup additive has a superior performance.We have preparation another CO2 switchable microemulsion system based on N,N,N',N'-tetramethyl-1,3-propanediamine(TMPDA)/sodium dodecyl sulphate (SDS)/n-hexane/n-butanol and water, and the molar ratio of SDS and TMPDA is 2:1. Through change the proportion of O(hexane) and S+A(SDS/TMPDA+butanol), the pseudoternary phase diagram of microemulsion was obtained. The formula as follow:12.24% SDS,2.76% TMPDA,20% hexane,15% butanol and 50%water was choosed from single-phase microemulsion phase area in the pseudoternary phase diagram. The bicontinuous miroemulsion (B.C) was obtained and the CO2 switchability was confirmed by Conductivity and DLS. When bubbling CO2 into the microemulsion at 25?, the phase separation was observed and displacing CO2 with N2 at 50 ?, the nanoemulsion was reformed. The switchable of nanoemulsion was measured by conductivity. As the cleanup additive it has a good surface activity, wettability, and compatibility.