Nanomaterials in Fracturing Applications
- Valerie Lafitte (Schlumberger) | Gary John Tustin (Schlumberger) | Bruno Drochon (Schlumberger Cambridge Research) | Michael D. Parris (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE International Oilfield Nanotechnology Conference and Exhibition, 12-14 June, Noordwijk, The Netherlands
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 2.5.2 Fracturing Materials (Fluids, Proppant), 5.8.4 Shale Oil
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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.
Borate crosslinked fluids have been used for more than 40 years in hydraulic fracturing. These fluids are economic and are effective in terms of proppant transport and fluid loss and now such fluids can withstand temperatures up to 250°F. Significant performance improvements came via formulation optimization, little from improving the chemistry itself. Today, due to new challenges that face the industry in terms of deeper wells, harsher conditions and tighter environmental legislation, the development of novel crosslinker chemistry is becoming a necessity.
Three challenges have certainly emerged over the last couple of years. First, the cost of guar has increased which has had a strong economic impact within our industry. In addition, the increase of shale oil activity in North America has considerably amplified the amount of guar needed to maintain this level of activity. Therefore, reducing the amount of guar will not only have a positive impact on the clean-up of the polymer and ultimately the production of the well, this will also improve treatment economics.
A second challenge arises from tight environmental legislation which is limiting the use of specific boron crosslinker in certain onshore and offshore operations.
Finally, we reported in 2008(1,2), that borate crosslinked fluids show viscosity dependency as a function of pressure. The effect of this pressure dependency upon the effectiveness of the fracturing process is currently under investigation.
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