Guest Lecture PPT

Geo

Reservoir Modeling

The process of creating a numerical representation of a subsurface reservoir to understand how fluids such as oil, gas, or water move through the rock.

Why Reservoir Modeling

It allows us to see underground, understand the physics of the reservoir, and make engineering decisions to maximize recovery, or storage and minimize risk.

Routine Core Analysis (RCAL)

Includes basic measurements performed on core samples

Special Core Analysis (SCAL)

Includes more detailed and advanced lab tests that capture the dynamic and rock-fluid parameters in the reservoir

Whole Cores

Flow tests, Enhanced Oil Recovery, rock mechanics, and directional permeability

Standard Plugs

2-3” long and 1.5” in diameter

Porosity

What fraction of the total rock volume is made up of pore spaces where fluids like water, oil, gas, or supercritical CO2 can be stored.

Engineering “Matrix”

1. Framework

2. Matrix

3. Cement

4. Pores

Measurement of Porosity

• Core samples (measure of two) for limited wells

• Wireline (wells) logs: usually available for each drilled wells

Helium Porosimeter

• a precise instrument using the principle of gas expansion (Boyle's Law) and helium's small atomic size to accurately measure the pore and grain volumes, porosity, and density of porous materials like rocks, powders, and core samples

• Measures Grain or Matrix volume

• Uses helium because it behaved ideally

Boyle’s Law

The relationship between pressure and volume of gas when the temperature and amount of gas remain constant

Absolute Permeability

Permeability to a single phase

Effective Permeability

Permeability to one phase when more than one phase are present

Relative Permeability

The ratio of effective permeability to a base permeability (absolute permeability)

Who discovered that permeability measurements made with air were always greater than the permeability obtained with liquid?

Klinkenberg (1941)

Kilkenberg gas exhibited ____ at the sand grain surface

Slippage

When pressure increases, the calculated permeability _____

decreases

Interfacial Tension

The force that acts along the boundary between two immiscible fluids because the molecules in each fluid prefer to stay with their own kind

Immiscible fluids

Do not mix

Mixable fluids

Do mix

Wettability

The tendency of one fluid to spread on or adhere to a solid surface in presence of other immiscible fluids. It refers to interaction between fluids and solid phases

Wetting phase fluid

preferentially wets the solid rock surface

Attractive forces between rock and fluid draw the wetting phase into

small pores

Wetting phase fluid often

has low mobility

Attractive forces

Limit reduction in wetting phase

Many hydrocarbon reservoirs are either

totally or partially wet

Water is wetting phase

Theta < 90

Nonwetting phase

does not preferentially wet the solid rock surface

Repulsive forces between rock and fluid cause non-wetting phase to

occupy largest pores

Non wetting phase fluid is often the _________ especially at large non wetting phase saturations

Most mobile fluid

Water is non-wetting phase

Theta > 90

Capillary Pressure

The pressure difference between two immiscible fluids caused by the curvature of their interface inside the pore space

Capillary Pressure Measurments

1. Mercury injection capillary pressure

2. Porous plate method

3. Centrifuge Method

Lithofacies

A “rock type unit” define by its observable features such as grain size, texture, composition, color, and sedimentary structures that tell us how and where it was formed.

MICP Test

• Measures the pore-throat size distribution and capillary pressure behavior of a rock by injecting mercury into a dry, vacuumed sample under increasing pressure

• Not a good representation for capillary forces because mercury has different fluid properties that make the readings unrealistically high

• Is a useful measurement of b distribution