Cross-linked fluids have been used in the oil industry for more than 40 years in applications such as hydraulic fracturing and water control. Today, these fluids need to be reformulated in order to respond to new challenges, such as harsher reservoir conditions and they also need to comply with tighter environmental legislation. Nanotechnology may well provide an answer to this end. By utilizing unique features such as high surface/volume ratio and specific surface functionalisation, we are able to change the nature of the cross-linking and hence better achieve the required gel properties.
This paper describes the synthesis of a series of boronic acid functionalised nanoparticles and their application to guar crosslinking. In particular, the synthesis of 15 nm boronic acid functionalized polymeric nanomaterials (also called nanolatexes), using microemulsion polymerization were investigated. Such nanodevices showed, for the first time to our knowledge, unique crosslinking properties with guar. It was found that these larger crosslinkers, as compared to standard borate molecules, can crosslink guar at much lower polymer concentrations, effectively lowering the critical overlap concentration of the polymer. We were also able to generate stronger gels over a wide range of guar concentrations. Furthermore, the optimal amount of boron required to achieve these gels was of the order 20 times lower than that with conventional borates.
This result suggested that the efficiency of the crosslinking was much higher in the case of the nanoparticles. Several rheological and stability tests were performed under field conditions and these indicate these systems have potential uses as oilfield materials. The influence of the surface chemistry of the nanoparticles was also studied along with other functionalization of other nano-materials, such as nano-silica and graphite. These results will also be presented.