Gravitation in Thermal EOR - How Disadvantage Can Be Used to Improve Efficiency of Thermal EOR

Abstract

It is a matter of general experien ce that gravitational effects arising during injection of air or steam most oFten affect adversely the efficiency of thermal EER methods . Advantages of these methods are generally used wipere possibility exists of eng i neering a horizontal displacement .The present paper centres on certain technologica) approaches to the use of gravitational effects for improved efficiency of thermal EOR methods .One of the technologies -a cyclic injection of steam into high-viscosity oil reservoir witti bottom water -was applied in 1974 in Yuzhno-Karskiy area of Zybza -Gluboky Yar oil field (trap III), the Krasnodar Territory (Figure 1) . Miocene reservoir of (he area is defined as a water-supported monocline (Figure 2) . Miocene deposits are represented by accumulation of breccia, detritus and terrigenous rocks . Reservoir capacity is made up by voids between the rock debris witti up to 30% of the capacity being characterised by extremely high permeability (up to 640 Darcy) .The main geological and physical parameters of the reservoir are as follows : Within 18 years of reservoir deve l opment witti depletion drive (since 1 956) produced are about 600 Mt of oil, oil recovery reached 21%. Water cut reached 77%due to water encroac h ment mainly through the reservoir bottom . As a result, the reservoir had transformed in a floating one .Starting Erom the second hal f of year 1 974, the reservoir is under development by steam stimu la t ion . I n view of a vide water-oil zone existed and abnormally high per meability of t h e reservoir it was decided to inject steam intermittently info a lowered par t of the reservoir to displace oil Erom a porous reservoir of water-oil zone to t he zone of production and t o form heat slugs at the oil-water surface of upper reservoir areas.]t was conceived that due to a h igh rate of the injected steam coming to the water-oil surface a heat slug had to be formed in the upper reservoir areas, heat energy of the stug being consumed for oil heating and oi l viscosi ty breaking.P enetration of heat slug info oi l zone an d f l ow of h eated oi l to p r oducing Wells veere p rovided by bottom-water drive . The proces is presente d schematically in

Enhanced Oil Recovery: Methods and Applications Review

“…Also, Marmul Field documented a polymer flooding in Oman; twenty years later, a large-scale study is in progress. Several EOR chemical processes other than polymer flooding, such as ASP flooding, have been studied and examined in Daqing for more than 15 years [8]. Gudong, Karamay, Liahoe, and Shengli fields are other examples of Chinese ASP projects documented in the literature.…”