PETROPHYSICAL PROPERTIES OF

RESERVOIR ROCKS

INSTITUTE OF MANAGEMENT SCIENCES

UNIVERSITY OF LUCKNOW

Presented by……. Juhi Siddiqui MBA Sem. III

CONTENTS

1. Petrophysics2. Porosity3. Permeability 4. Capillarity5. Saturation 6. Conclusions

PETROPHYSICS

Petrophysics (petro is Latin for "rock" and physics is the study of nature) is the study of the physical and chemical properties that describe the occurrence and behavior of rocks, soils and fluids.

Petrophysics mainly studies reservoirs of resources, including ore deposits and oil or natural gas reservoirs.

The productivity of wells in a hydrocarbon-bearing (oil/gas) reservoir depends on petrophysical properties.

Hydrocarbon bearing reservoir rock consists of two components: a. Rock matrix b. Interconnected pore network

The main petrophysical properties of reservoir rocks are:

Porosity Permeability Saturation Capillarity

POROSITY The porosity determines the storage capacity for

hydrocarbons.

It can be defined in various ways:- The porosity of rock is the ratio of its total pore spaces

to its total volumes i.e., for given sample.

Porosity = Total volumes –Bulk volume. Porosity of a material is defined as that fraction of the

bulk volume of the material that is not occupied by the solid framework of the material.

In oil reservoirs, the porosity represents the percentage of the total space that is available for occupancy by either liquids or gases.

Porosity determines the storage capacity of the sand and is generally expressed on a percentage basis or as a fraction or as a decimal.

Porosity = Volume of total pore space× 100 Volume of rock sample

TYPE OF POROSITY

ON THE BASIS OF ORIGIN

PRIMARY POROSITY

SECONDARY

POROSITY

ON THE BASIS OF PORE PATTERN

ABSOLUTE POROSITY

EFFECTIVE POROSITY

Figure showing

Differenttypes of porosity

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PERMEABILITYIt is mainly known as the efficiency of the porous

medium and is defined as the property that permits the passage of a fluid through the interconnected pores of a rock without damage or displacement of the rock particles.

It is measured in darcies.

Darcy's law. The velocity of homogeneous fluid flow through a porous media is directly proportional to the pressure gradient and inversely proportional to the viscosity of the flowing fluid.

K= µQL /∆PAWhere—

K =permeability in Darcy

Q =vol. rate of flow in cc/sec.

µ =viscosity of gas in centipoise

L =length of the core in cm.

A =cross-sectional area of the core

∆P =pressure difference

Types of Permeability

Effective Permeability

The ability of the rock to conduct a fluid in the presence of another fluid, immiscible with the first, is called its effective permeability to that fluid.

Relative Permeability

Relative permeability is the ratio of effective permeability of a particular fluid at a particular saturation to absolute permeability of that fluid at total saturation.

CAPILLARY PRESSURE

When two fluids occupy the pore space in a porous medium the interfacial boundary between the two fluids is curved.

The degree of the curvature is dependent on the size of the rock pores and the proportion of the fluids present.

There is difference in pressure between the fluids across this interface; it is usually termed the capillary pressure.

Capillarity determines how much of the available hydrocarbons can be produced.

The capillary properties of a porous medium are determined by:

(a) The geometrical configuration of the interstitial space in the matrix.

(b) The physical and chemical nature of the interstitial surfaces.

(c) The physical and chemical properties of the fluid phases in contact with the interstitial surfaces.

FLUID SATURATION

Fluid saturation is the measure of the gross void space in a reservoir rock that is occupied by a fluid.

In place determination of reservoir fluid saturation consist in analyzing reservoir core samples for water and oil, the saturation in gas being obtained by differences since the sum of the saturations in the three fluids is equal to unity.

CONCLUSIONS Accuracy of petroleum reserve estimation lies mainly

in proper analysis of petrophysical behavior of reservoir.

Extensive work on petrophysical modeling of reservoir results in exponentially increased recovery factor.

The ratio of the permeability of the rock to the oil to its permeability to gas or water determines the efficiency of the recovery mechanism, and this ratio continually changes.

Thank

You….