Mobility and Viscosity Enhancement of Fluids in Heavy & Extra-Heavy Oil Sandstone Reservoirs
Authors: Diaz J. Torres , Merchand G. Guillot , Rodriguez L. Gallegos , Jimenez R. C. Tejero , Nieto N. L. Acosta , Portillo E. A. Juarez 
Published: November 2024

In Mexico, oil reserves are estimated at 9,711 MMb (Million barrels), corresponding to 62.2% of heavy oil, 28.9% of light oil and 8.9% super light oil. Exploiting the hydrocarbon reserves contained in Cretaceous and Tertiary periods in southern of Mexico is extremely important to maintain the oil production. Samaria field located in Tabasco, Mexico contains reserves producing heavy and extra-heavy oil in unconsolidated sandstone reservoirs, porosities range from 25 to 30% and permeabilities are greater than 1 Darcy, in certain areas. The remaining reserves are between 11.66 and 63.2 MMb and with the current technologies used it is intended to achieve a final recovery factor of 15.6% up to 30.2%. Oil is between 5 and 22 °API gravity, the reservoir temperature ranges are 110 to 150 °F. Under these conditions, the oil behaves as a Newtonian fluid; however, when oil is at surface and its temperature decreases, it reaches viscosities between 20,000 to 40,000 cp (centipois). The near wellbore contribution zone in this type of unconsolidated heavy and extra-heavy oil sand reservoirs presents limitations to production such as high-water saturation and fines migration derived from drag due to high viscosity, and this is where the greatest pressure drop in the reservoir-well system occurs.

Our methodology focuses on improving the behavior of the rheological properties and mobility of fluids in the critical matrix, applying chemical systems specifically designed to reduce viscosity, improve mobility and thereby reduce the associated skin damage. The purpose of this work is to present the results of an innovative methodology to increase or reactivate production and with this to support the growth of the current recovery factor of the reservoir.

The work culminates with the execution of appropriate measurements (or gauging) to evaluate the effectiveness of the methodology. The treatment was applied in a 13° API heavy oil well with beam pumping installed, of the Samaria Luna Production Asset in the Southern Region of Mexico, achieving in 110 days -of evaluation- an accumulated contribution of crude oil of 5,500 barrels in addition to the initial production, representing gross income of USD $388,000.00 with a net profit of USD $68,000.00 and investment recovery time of 47 days. These results demonstrate that the methodology is technically and economically feasible as an alternative solution in fields of this type that, together with an adequate artificial lifting system, contributes to increasing the final recovery factor of the reserves. The artificial lift system was already installed in the well before the treatment. That net profit doesn't include that cost.

The design of the chemical system carried out through a base of consistent and adequate laboratory tests that confirm the problem of the high viscosity of the oil, as well as the formulation of the required additives and their concentration, together with of a good and correct operational execution guaranteed the success of the overall treatment.