The loss circulation composition comprising the nanosilica based dispersion and a chemical activator has been designed to treat moderate to severe losses. The nanomaterial used in this loss circulation composition is an environmentally friendly material and a chemical activator. The loss circulation composition is so designed so as to give delayed gelling of the nanoparticle based dispersion. A major advantage of this technology is its ability to place the loss circulation treatment composition in to the target loss circulation zone before the nanoparticle based dispersion gels up. Premature gelling of the nanoparticle based dispersion would avoid premature setting of the treatment fluid before it reaches the target zone. The newly developed system can be used effectively up to 300°F.
In this paper, experiments have been performed with three different types of nanoparticles differing in their surface charges and particle sizes. Two negatively charged nanoparticle-based dispersion with a particle size of 5nm and 17nm respectively and one positively charged nanoparticle with a particle size greater than 17nm have been evaluated as loss circulation materials. Two different types of chemical activators, one organic and the other inorganic have been used in this study and their effect on the gelling time has been evaluated. The gelling time experiments have been done at four different temperatures viz. 150°F, 200°F, 250°F and 300°F. The effect of activator concentration and different shear rates on the gelling time of the three nanoparticle-based dispersions has been studied. Permeability plugging tests have been performed on the three nanoparticle-based dispersions using 2mm slotted disks and their effectiveness in controlling moderate to severe losses has been evaluated
The loss circulation composition can be designed so as to control its gelling time by adjusting the activator concentration. The results show that a specific gelling time of the loss circulation composition can be obtained to achieve a predictable and controllable pumping time. This pumping time can range from a few minutes to several hours at over a wide range of temperatures. A predictable gelling time would allow the nanoparticle-based dispersion to remain pumpable for sufficient time before being placed in the loss circulation zone. The loss circulation composition which turns from a liquid to a gelled solid is then expected to seal off the loss circulation zone and thereby prevent fluid loss.