Study Of Technologies Of Hydrodynamics And Physical And Chemical Methods For Enhanced Oil Recovery

Works are carried out in several areas:

  • fundamental and applied studies in the area of creating efficient and environmentally-friendly technologies based on chemical reagents for enhanced oil recovery and production stimulation;
  • development and implementation of hydrodynamics methods for enhanced oil recovery (unsteady-state flooding) in combination with targeted well treatment;
  • creation, study, and implementation of physical and chemical methods for enhanced oil recovery and production stimulation;
  • experimental research, development, and implementation of gas and gas-water methods of formation stimulation, including those using highly dispersed gas-water systems;
  • development and implementation of gel-forming, visco-elastic, residue-forming composite systems used in water isolation processes, oil-producing well killing, and technologies for redistribution of injected water flows;
  • development and adaptation of existing technologies for enhanced oil recovery and production stimulation, designer's in-process control over implementation thereof;
  • development of instructions, corporate standards, and guidelines for implementation of advanced recovery methods and production stimulation;
  • monitoring and analysis of the efficiency of works concerning enhanced oil recovery and production stimulation;
  • justification of the most efficient technologies for specific geological and physical conditions.

The most promising stimulation methods during development of fields at the final development stage or approaching it is unsteady-state flooding (USF) in combination with targeted well treatment (integrated technology), and well processing based on system technology principles.

To solve the set problems, guidelines for classification of development targets for USF application have been developed. This approach is distinguished by the fact that the prospective targets are selected based on analysis of existing geological and physical parameters characterizing any of the development targets, such as sandiness, zone-by-zone and layer-by-layer heterogeneity, compartmentalization, and level of reserve depletion. Development targets have been classified for the conditions of Slavneft-Megionneftegaz OJSC fields in order to assess the prospects of USF application. The classification includes 22 development targets located at 15 fields. Furthermore, 125 fields (296 development targets) of LUKOIL PJSC located in various regions of the Russian Federation have been classified. Following the classification results, prospective targets for industrial experiment works have been identified.

Technologies have been developed aimed at redistribution of drainage water flows in the formation in order to increase formation coverage by flooding both in terms of the formation width and area, as well as limitation of the volume of associated water incoming into producing wells through highly-permeable interlayers, based on heat-resistant inverted emulsions and gel- and residue-forming compounds.

A range of acid compounds and compositions have been developed based on inorganic and organic acids for treating terrigenous and carbonate collectors in various formation conditions that are stable systems resistant to formation temperature and possessing demulsification properties, low oil interfacial tension, and allow increasing collector permeability 2-3 times on the average without destroying the rock matrix. The technologies have been implemented at fields of West Siberia, Tatarstan, and the Komi Republic etc. Production gain constituted from 500 to 1200 tons of oil per 1 producing well treatment with increase of daily flow rate by 4-20 t for the duration of 8 months and more. Treatment of injection wells increased injectivity 2-4 times.

Following laboratory experiments, formulas have been developed for killing fluids that allow preserving the formation collecting properties in case of well repair. The formulas are based on salt solutions of surface-active agents with the density of 1.01 to 1.48 g/cm3 or inverted emulsions with a wide range of density - from 0.950 to 1.400 g/cm3 characterized by high heat-resistance for application in killing processes at West Siberia fields.

ASP (alkali-surface-active agent-polymer) and SP (surface-active agent-polymer) technologies have been developed for the purpose of enhanced oil recovery that allows increasing formation coverage and reducing collector hydrophobic behavior. Laboratory experiments concerning extra displacement of residual oil showed that injection of 0.3 Vpor of the composition allowed recovering 24% of residual oil, and the displacement efficiency increased by 12%.

Experimental studies of oil displacement from producing reservoirs by physical and chemical advanced recovery method employ a unit for investigating oil-displacement and filtration properties of chemical compositions under conditions close to the reservoir ones. Experiments are conducted both on producing reservoir made-up models and core samples using isoviscous models of oil, formation water or its model. Rock pressure is modeled when working with core samples. The unit is automated and can be controlled via a personal computer. It can also record main experiment parameters: mobility, displacement efficiency, residual oil content etc.

Unit for studying oil-displacement and filtration properties
of chemical reagents under conditions close to the reservoir ones

Experimental studies of gas and water-gas stimulation of formation are being conducted.

Experimental studies of water-gas stimulation technologies employ an upgraded filtration unit enabling high-precision control over three-phase filtration processes and performance of experiments at temperature up to 300С and pressure up to 35 MPa. A unit for recombination of oils of specific development targets has been created. Experiments use both producing reservoir made-up models and core samples taken from the reservoirs of the fields under study.

Laboratory filtration bench:
1 – reservoir model; 2 – pressure differential gage; 3 – ISCO pump;
4 – temperature-controlled chamber; 5 – back pressure unit;
6 – hand press; 7 – reference pressure gage; 8 – glass sampler;
9 – gas burette; 10 – cutoff valve; 11 – switch valve

Laboratory studies of oil displacement processes by means of gas and water-gas stimulation employ hydrocarbon gases, nitrogen, carbon dioxide, or mixtures thereof. These methods can be used both for pre-flooded reservoirs and fields at the initial development stage. It is possible to inject water and gas as alternating fringes of certain size or ultrafine water-gas mixture with gas bubble size comparable to the size of pore channels.

Principal efficiency of WGS methods has been proven in comparison with flooding, as well as the advantage of their application for low-permeable collectors in comparison with high-permeable ones. It has been experimentally proven that displacement efficiency can increase by 10% and more during additional oil displacement in a flooded reservoir using WGS methods.