U.S. oil and gas services companies were the most active filers of patents for fracking technology last year, with major sector players Halliburton Co., Baker Hughes and Schlumberger Ltd among those seeking most vigorously to expand their operations in the field.

According to Thomson Reuters estimates, the number of patents filed on a global level has touched a historic high, hitting 706 in 2013. This is 28% more than the number of applications submitted the previous year, when they stood at 550.

Thomson Reuters also counted Russian and Chinese oil and gas companies among the most prolific patent seekers. The presence of firms from these countries in the list, including Tatneft, Petrochina and Daqing Oilfield, is a relatively new development, particularly given the Russian industry's relative reluctance to use the global patent system compared to companies in the United States and Europe.

Fracking already accounts for a substantial portion of the overall gas output of the United States and companies are now treating the expansion of their fracking activities as top priority. Boosting their share of international projects is a major part of their strategies and many are now seeking to extend their geographic footprint by starting projects in more challenging locations, commented Gwilym Roberts, partner at Kilburn & Strode LLP.

A significant number of the fracking patents lodged last year sought to facilitate the expansion of businesses' fracking operations in remote areas, Thomson Reuters noted. For example, there were patents for systems intended to supply energy to projects in isolated sites and for technology to heat water in fracking operations without electricity.