Performant Non-Emulsifiers for High-Brine and Acidizing Applications

Oil production is accompanied by water production in various ratios. This poses additional challenges to the industry as oftentimes the typically immiscible liquids form stable emulsions that need to be broken further and the two phases separated, incurring supplemental production costs. In stimulation operations such as hydraulic fracturing or acidizing, emulsions can form due to the presence of aromatic and naphthenic compounds in the crude oil along with surfactants present in the pumped fluid. Additional complications arise in the acidizing treatments since the acids used can further stabilize the emulsion with crude oil, making the phase separation even more difficult. This paper discusses simple 3- and 4-component formulations based on non-ionic surfactants and solvent/co-solvent that were successfully used as demulsifiers (DE), non-emulsifiers (NE) and weakly emulsifiers (WE) over a range of medium and heavy crude oils. A range of 3 medium and heavy crude oils were emulsified in a 1:1 ratio with either synthetic seawater or with 15-20% HCl. A composition analysis was run on the selected crude oils to determine the likelihood of the best formulation candidates to maintain their effectiveness in other crude oils. A comprehensive solvent/surfactant screening was performed aiming to find the best formulation that would work in each case. The best performers from the screening were further optimized and tested against commercial demulsifiers and their performance evaluated and discussed. The study resulted in the design of a few successful formulations that showed great performance over the range of crude oils utilized. The top candidates consisted of a 4-component formulation for the high brine and a 3-component formulation for the acidizing application and they worked well both as NE and as DE. Other formulations showed good performance as WE. The NE/DE compositions met the general performance criteria of providing complete phase separation within 5 minutes and with no emulsification. The WE formulations provided similar performance with the only difference that some emulsification occurred, as evidenced by the water layer taking up a slight color. The formulations discussed in this paper provide the operator with a series of benefits, among which: on par or better performance with similar commercial products, do not involve use of polymers that can have adverse effects on the downhole formation or pose supplemental challenges during downstream processing and have a better environmental profile, as they are not based on phenol, amine or sulfonate derivatives.