Porosity and Permeability of Petroleum Reservoir Rocks || Petroleum Engineering

Porosity of Reservoir Rocks

Porosity is defined as Total pore volume divide by Total Rock Volume.For the clastic  rocks hydrocarbon accumulate in pore space.

1. For Clastic Rock Porosity occurs 
2. For Non Clastic rock Void space occurs.
3. For igneous rock  Fracture  Occurs

Two types of porosity, and these are -

1. Total Porosity or absolute porosity 
2. Effective Porosity

1. Total Porosity:- 

In total porosity or absolute porosity it includes the interconnected pore space as well as dead pore space.

                                                           Total Pore Space volume 

                     Total Porosity =                 Total Volume Rock

2. Effective Porosity 

Effective porosity is only interconnected porosity. 5-10 % lesser than total porosity.

Based on the origin of rocks -

• Primary Porosity/Original Porosity 
• Secondary Porosity/Induced Porosity

1. Primary Porosity/ Original Porosity:-

This pore space generate at the time of deposition of sediment. Primary porosity depends on ----

1.  Size OF Rock Grain
2.  Packing of Rock Grain 
3. Uniformity of Rock Grain 
4. Shape of Rock Grain 
5. Sorting of Rock Grain 

If rock Grain  is Spherically Packed , Porosity is very High.

47 % is higher or maximum porosity for elastic rock. Not Possible to get higher than 47 percent in clastic rocks.

Porosity of rhombohedralically  packing rock is only 25 percent.

Inter-granular porosity is 25 % is an example of primary porosity.

2. Secondary Porosity/ Induced Porosity:- 

This pore generate after the deposition of sediment due to tectonic and geological activity ( Earthquake , generation of fault). Example - 

• Fracture in the igneous rock.
• Fracture  in Carbonaceous rock.
• Fracture in the shale rock.
• Fracture in CBM reservoir. 

Permeability   

It is the fluid transmit ability of the rock. It basically Depends on -

1. Connectivity of pore spaces:-  Higher the connectivity, higher is the permeability.
2. How easily a fluid pass through the porous media.

Permeability are three types ---

• Absolute Permeability.
• Effective Permeability
• Relative Permeability 

1. Absolute Permeability

The porous media is saturated with single phase ( Only Crude oil, gas and water ). Then in which the fluid fluid can passed through porous media. Then it is called Absolute Permeability.

Absolute permeability is rock property.

2. Effective Permeability

If porous media is saturated with two phase, then how easily a fluid passed through porous media in present of other fluid then called effective permeability.

3. Relative Permeability

Effective Permeability

Absolute Permeability

Unit of Permeability 

Unit of permeability is darcy. (K)

For linear flow the negative sign is required.

Direction of Change in pressure and direction of length is different, For linear blow.

Notes:- Data is collected from various university notebook , purpose is to help everyone.

Article written by:-

Ritu Raj Medhi

Founder & president 

Chief Technical and Editorial Officers

Petroleumbuddy Websites and Initiatives

 

Basics of Reservoir Engineering

Reservoir Engineering 

Reservoir engineering is a subset or sub branch of petroleum engineering. Basically reservoir engineering is application of scientific principal and mathematics principle in reservoir. We used to study the flow of reservoir fluid to, from and through the reservoir and how we can be maximized the recovery of reservoir fluid by the best utilization of reservoir own energy and drive mechanism.

In short study the different fluid movement, source to reservoir and reservoir to surface.

Basic Tools of reservoir Engineering

As a reservoir engineering we have to knowledge of some basic tools , which we often uses as a Reservoir Engineering. This basic tools are -

• Sub Surface Geology 
• Applied Mathematics
• Basic principles of physics and chemistry which is used to study its behavior of crude oil, Natural Gas , Gas condensate etc.
• Reservoir Stimulation software.

Basic Function of Reservoir Engineering

• To analysis the property of reservoir.
• To increase the recovery, we have to study the drive mechanism.
• Estimation of Hydrocarbon in Reservoir.
• How Much Crude or natural gas can be produced ?
• How fast can be produced (Production Rate ) from the reservoir ?

Primary function of Reservoir Engineering   

• Original Oil
• Production (Reserves)
• Production Rate
• Which Secondary or tertiary recovery recovery method are suitable for the reservoir and when should be applied ?
• Which formation are suitable for underground gas storage ?
• To Forecast/Estimation Future behavior of the Reservoir under various drive mechanism ?
• To study the behavior of reservoir and study the economic condition before implement any operation ? 
• You have to some knowledge regarding EOR and IOR

Important thing as a reservoir engineering.  

• You have to be expert in reservoir drive mechanism ( We discuss all drive mechanism in our article briefly)
• You have to learn at least two reservoir simulation software.
• You have to be expert in reservoir calculation process such as Material Balance equation.
• Basic knowledge of Physics , chemistry and Petroleum Geology.
• Expert in Petroleum Industry.

 We will discuss more about reservoir engineering in future articles.

Notes:- I write this article with my knowledge, some information is taken from different university notes book. This article is helpful for our industry person and student.

Element and Characteristics found Petroleum Reservoir

Petroleum Reservoir

We found some common characteristics and element in petroleum reservoirs. A petroleum reservoir must be satisfied these character to become reservoir. In this articles we will discuss these character and elements. 

Elements and character that found in petroleum reservoir are -

1. First we have to search for the sedimentary basin.
2. Trap
3. Reservoir Rock 
4. Cap Rock 
5. Source Rock.

We will discuss each petroleum reservoir elements briefly one by one.  So lets discuss these elements.

1. Sedimentary Basin

Sedimentary basin are generally generation of sediment or deposited place. These are the geologically deposited are of earth where unmetamorphous sediment are deposited where thickness of the sediment highest in center and decrease in edges. 

        Worldwide around 670 sedimentary basin are available.

2. Trap

Favorable structure in sedimentary basin for the accumulation of hydro-carbon  and water. these where hydro carbon is accumulated  called reservoir, where H-C is accumulated called reservoir, where water is accumulated called aquifer.

• Structural Trap
• Strati graphic Trap
• Combination Trap

a. Structural Trap

These type of trap are formed by after the deposition or formation of rock due to tectonic activity.

b. Stratigraphy Trap

Formed at the time of deposition of rock or formed after deposition by erosion of rock. Example of this trap are undulation  and unconfornity.

c. Combination Trap

Combination of both structural and stratigraphy types of trap.

Main function of this are includes 1. Trap the crude fluid (resist the fluid to flow)

3. Reservoir Rock

Reservoir must be highly porous and high permeability. It must have highly porous and permeability to become reservoir rocks and we extract petroleum from reservoir rocks. Petroleum Accumulation at very high pressure and temperature condition. Example - Sand Stone and Lime Stone.

It is made up of basically sedimentary rock, Clay rock, and some time igneous rock.

4. Cap Rock

Cap Rock hold petroleum and resist petroleum from mitigation. It is nothing but the top seal of the trap. It resist the upper movement of  hydro carbon.

It is made up of basically sedimentary rock, clay rock, and some time igneous rock.

5. Source Rock

Hydrocarbon generate by source rock. It is a type of organic rock which have enough capacity to generate hydrocarbon.

Shale, Lime stones are an example of source rock. Shale are the common source rock found in all over the world. From source rock petroleum moves to the reservoir trap after generation because of pressure and temperature.

Shale Source Rock 

Gas generate source rock and store is itself. Porosity and permeability low. In case of shale gas petroleum not store in pores of rock and accumulated at the surface of source rock by adsorption method. Shale acts like a imphrous rock, cap rock also.

In case of CBM and unconventional reservoir this shale acts like a source rock as well as reservoir.

Notes:- This Data of this articles is collected from different university notes and different e&p companies websites. Our main purpose is only benefit of students.

Article Written &  Composed by:-

Ritu Raj Medhi

Founder & President

Chief Technical & Editorial Officers

Petroleumbuddy Initiative and Websites