Thermal EOR (Steam Assisted Gravity Drainage)

· High Recovery Factor:

· up to 60%

· Quick process (high thermal diffusivity)

· Proven technology:

· several pilots since 1980's in Alberta and elsewhere

· Mature enough for medium scale field tests

Gas: miscible/immiscible (Nitrogen flooding)

· Produced from air by cryogenic separation

· Available from 95-99%

· Inert and non corrosive

· No need of corrosion inhibitor

Gas: miscible/immiscible (CO2 injection)

Microbial EOR

Microbes react with a carbon source, such as oil and produce surfactant, slimes (polymers), biomass and gases such as CH4, CO2, N2 and H2 as well as solvents and certain organic acids.

Conclusion

EOR production is increasing but slowly

n Despite a context of high oil price & increasing demand

n Today evolution technologies

n Steam is decreasing for very viscous crude

n Environmental impact of high water consumption

n Price of gas, high CO2 emissions for others

n CO2 is highly increasing

n Additional revenues for CCS

n Answer to global warming concern

n Chemical injection, mainly polymer flood

n Allow to enhance waterflood, widely used technology

n As a wide potential

n Not no expensive technology

 

Introduction to Reservoir Engineering

Roles of the Reservoir Engineer

• Contributing with geologists and petrophysicists in estimation of oil-in-place
• Determining fraction of oil-in -place that can be recovered.
• Attach a time scale to the recovery.
• Day-to-day operational reservoir engineering throughout the project lifetime.

 

Activities of Reservoir Engineering

• Reserve Estimation
• Development Planning
• Production Operations Optimization

 

Reserve Estimation

• The reserves are the main assets of an oil company.
• Quantifying reserves and recovery factor is an ongoing role of the reservoir engineer.
• Basic data not always straightforward.
• Reserves can be affected by the development process

 

Optimal Development Planning

• Large upfront investment
• Requires detailed understanding of the reservoir characteristics
• Various development options to be considered

Reserves

• Recoverable hydrocarbons
• OIP x recovery factor

Reserves are those quantities, which are anticipated to be commercially recovered from known accumulations from a given date forward.

There are two types reserves developed and undeveloped. Developed- proved reserves 90% probability that quantity will be produced or exceeded. Undeveloped is divided into two: probable (50%) and possible (10%).

Volume in-place calculations

Economic limit - will vary according to project type and size.

 

Improving Recovery

Three phases of recovery

• Primary recovery
• recovery obtained through natural energy of the reservoir
• Secondary Recovery
• energy is supplemented by injection of fluids, gas or water. To maintain or partially maintain pressure.
• Two types of oil left.

1. High saturation in unswept par - bypassed oil

2. Lower saturation in swept part - residual oil saturation

• Enhanced oil recovery, EOR.

The target for by-passed and residual oil.

Hydrodynamic Pressure

• Arises as a result of fluid movement.
• This is the fluid potential pressure gradient which is caused by fluid flow
• Under certain conditions fluid pressures are not normal.

· Overpressured reservoirs.

· Hydrostatic pressure greater than normal pressure

· Underpressured reservoirs

 

Hydrostatic pressure below normal pressure

· Nature and magnitude of pressures and the position of fluid contacts important to the reservoir engineer.

· Data for fluid contacts from:

- Pressure surveys

- Equilibrium pressures from well tests

- Fluid flow from minimum and maximum depth

- Fluid densities from samples

- Saturation data from logs

- Capillary pressure from cores

- Fluid saturation from cores.

Reservoir Temperature

• Earth temperature increases from surface to centre
• Heatflow outwards generates a geothermal gradient.
• Conforms to local and regional gradients as influenced by lithology, and more massive phenomena.
• Obtained from wellbore temperature surveys.
• Reservoir geothermal gradients around 1.6^oF/100ft (0.029K/m).
• Because of large thermal capacity and surface area of porous reservoir, flow processes in a reservoir occur at constant temperature.
• Local conditions, eg around the well can be influenced by transient cooling or heating effects of injected fluids.

Formation Pressures

Another interesting information was represented by Munsyzbayeva Dinara. The topic of the lecture is Formation Pressure.

Hydrostatic Pressure

The pressure at a given depth in a static liquid is a result the weight of the liquid acting on a unit area at that depth plus any pressure acting on the surface of the liquid

Pore Pressure

Abnormal Pressure

A “normally” pressured formation has a pore pressure equal to the hydrostatic pressure of the pore water. High pressures are called geopressures, overpressures and low pressures are called underpressures.