Gazprom Neft has undertaken multi-stage fracking in the eastern part of the Orenburg oil and gas condensate field (under development by Gazprom Neft Orenburg) using multi-stage fracking* combined with the use of a special component known as “divergent acid” — the first company in Russia’s oil and gas industry to do so. Five multi-stage fracking operations were undertaken in total, with the application of this new technology resulting in flow rates 50 percent up on planned performance.
The use of viscoelastic diverting acid (VDA**) in hydraulic fracking causes an extensive network of fissures to develop, allowing additional inflow of oil into the well. A key feature of this component is its capacity for forming a gel. This temporarily blocks any cracks which have already formed, directing the remaining acid to other parts of the strata, thereby increasing the coverage of the area affected. Thereafter, on interacting with hydrocarbons, the viscosity of the gel is reduced, and it is washed away together with the oil, into the well. In this case, moreover — and, again, under the first such application in Russia — VDA was used throughout the entire horizontal well shaft, not just in the fracked zone, further optimising oil recovery. The combination of various technologies — multi-stage fracking, the development and refinement of specialist drilling mud for use throughout the entire length of the well bore, and the use of high-technology VDA — have all served to significantly improve the impact of drilling operations.
Projects directed at improving oil recovery and increasing hydrocarbon inflow form one aspect of Gazprom Neft’s “Technology Strategy”. Well design and the technologies used, as well as in-field support, were managed by the Gazprom Neft Scientific Research Centre, together with specialists from Gazpromneft Orenburg. Further dissemination of these technologies could increase oil production at assets throughout the region by up to 15 percent.
Vadim Yakovlev, First Deputy CEO, Gazprom Neft, commented: “Combining multiple technologies significantly improves efficiency in field development. Continuing the implementation of our Technology Strategy, Gazprom Neft is successfully testing and improving the most up-to-date methodologies of enhanced oil recovery. Positive results from pilot projects mean the company has the opportunity to utilise experience gained at other assets.”
* Hydraulic fracturing (fracking) is a means of intensifying oil production, through the high-pressure injection of a mixture of fluids and a special proppant agent (proppant) into strata. The process of injecting the mixture creates highly conductive channels (“hydraulic fractures”) connecting the well (bore hole) and the strata. These fractures allow oil to flow that would not, under other circumstances, reach the well. Acid fracturing (acidizing) involves the use of a special acid, mixed with the propping agent. This too forms fissures in the strata under high pressure, but in this case also abrades the wall of the well (borehole) of any drilling-fluid residues that might impede oil inflow. Once production starts any remaining acid is completely flushed from the well.
** VDA — viscoelastic diverting acid.