Field Experience of Inorganic Gels Application with Cyclic Steam Stimulation

In this paper we present the experience of using inorganic thermotropic gel-forming compositions, combined with cycle-steam stimulation of wells, at the Permian-Carboniferous deposit of the Usinsk oilfield, Russia, the Komi Republic, over the last 5 years. The compositions are aqueous solutions of salts with a viscosity close to water and are injected immediately before or at the initial stage of steam injection. Then, under the temperature of the injected steam, the composition forms a gel that ensures the leveling of the injectivity profile, the increase in the formation sweep by the steam, and the reduction of the water cut of the product. Inorganic gel based on aluminum salts, in contrast to many polymer compositions, is able to withstand high temperatures, typical for steam treatments, about 300 C.

The object under consideration, the Permian-Carboniferous deposit of the Usinsk oilfield is a carbonate fractured reservoir, characterized by a high oil viscosity, 710 mPa∙s, and a heterogeneous geological structure. The initial reservoir temperature is 23 C, which together with the high viscosity of oil gives the prerequisites for the application of thermal methods of recovery.

Over the past 5 years, from 2014 to the present, several dozens, and more recently, more than a hundred, of steam cyclic treatments are being conducted at the field in question. Of these, about 15–20 wells are treated annually with the use of inorganic thermotropic composition GALKA, in its different variations. The average oil production rate in the wells before treatment is 2–3 t/day, in the first month after treatment 15 t/day or more. Water cut before treatment is 85–95 %, after treatment with application of the composition and injection of steam is reduced by an average of 20 %, up to 65–75 %, whereas for steam treatments without reagents, an increase in water cut is observed, as the vapor condenses and is extracted along with oil in the form of water.

Also, it has been assumed that there is some critical, or optimal, well capacity by the amount of injected steam during steam cycling treatment, about 4–6 thousand tons for processing for a particular field. Exceeding this value does not increase the efficiency, but, on the contrary, can cause additional watering at the initial stage of extraction after processing. The use of gel-forming compositions increases steam coverage and reduces water cut, which allows to increase this critical capacity.