A Free-Standing Organogel That Spontaneously Degrades to a Thin Sol After a Set Time

Many applications in the oilfield industry utilize a nonpolar organic solvent (i.e., an oil) to be gelled. The gel must be a shear-thinning fluid so that it can be pumped into an oil well. When the fluid reaches its destination in the oil-bearing formation, it must set into a gel. From a rheological perspective, this organogel must be sufficiently strong (high elastic modulus G’ as well as yield stress) so that it can act as an effective plug to block the flow of fluid (oil or water). However, the gel-like nature (and thus the plugging ability) may become undesirable after a period of time (2 to 4 weeks). Thus, after this time, there is a need for the gel to be degraded or dissolved. Numerous ‘degrading agents’ have been examined by the oilfield industry for a given type of gel, but they all have their drawbacks. Here, we present a solution to this vexing problem by designing a <i>self-degrading molecular organogel</i>. We use a small-molecule gelator, dibenzylidende sorbitol (DBS), that self-assembles into nanoscale fibrils in oils like n-alkanes or mineral oil, thereby gelling the oils. DBS organogels are highly robust and exhibit G’ above 10,000 Pa for just 2 wt% of added gelator – indeed the gels are free-standing, i.e., strong enough to manipulate between one’s fingers or place vertically on a countertop. At the same time, we have found that certain acid moieties can be introduced into the DBS organogel and induce slow degradation. Thus, the same strong organogel degrades into a thin liquid over a period of time, which can be tuned to be hours to days to weeks. In other words, we can formulate the gel with an in-built clock that sets in the degradation time. This avoids the need for injecting a degrading agent into the oil well. Our approach could be a game-changer for the oilfield industry.