Porosity and permeability

Formation of oil reservoir
porosity
classification of porosity
grain packing
permeability
factors affecting porosity and permeability.

1. RESERVOIR ROCK_ POROSITY & PERMEABILITY Submitted by : ABU IKHTIAR ALOM (PE-01/16) D.U.I.E.T.

2. FORMATION OF OIL RESERVOIR A  petroleum reservoir  or  oil and gas reservoir is a subsurface pool of hydrocarbons contained in porous or fractured rock formations. Crude oil is found in all oil reservoirs formed in the Earth's crust from the remains of once-living things. Evidence indicates that millions of years of heat and pressure changed the remains of  microscopic plant and animal into oil and natural gas.

3. The formation of an oil or gas reservoir also requires a sedimentary basin that passes through four steps: Deep burial under sand and mud. Pressure cooking. Hydrocarbon migration from the source to the reservoir rock. Trapping by impermeable rock. C ap rock  is any non permeable formation that may trap oil, gas or water, preventing it from migrating to the surface

4. POROSITY Porosity of a rock is a measure of its ability to hold a fluid. Mathematically, porosity is the open space in a rock divided by the total rock volume. Porosity is normally expressed as a percentage of the total rock which is taken up by pore space.  For example, a sandstone may have 8% porosity.  This means 92 percent is solid rock and 8 percent is open space containing oil, gas, or water.

5. Classification of porosity By their access capabilities to reservoir fluids . Absolute Porosity- It is defined as the ratio of the total pore space in the rock to that of the bulk volume. Effective Porosity- It is the ratio of interconnected pore space with respect to bulk volume.

6. GRAIN PACKING

7. PERMEABILITY Permeability is the property that measures the capacity and ability of the porous medium or reservoir to transmit fluids. It is a measure of the fluid conductivity of the particular material. It depends on the size, shape, tortuosity and number of the pore channels in the porous medium. It was first defined by Henry Darcy in 1856. Derivation of Darcy’s Law from Poiseuille’s Law : For fluid flowing through a circular channel V = ∆Pl²/32µL = ∆Pr²/8µL Q = V × A

8. If n numbers of channels present then Q = nV × A = nV × πr² = n × ∆Pr²/8µL × πr² = n∆Pr³π/8µL = nr²/8 × ∆P/µL × πr² = kA/µ × ∆P/L where, Q is the flow rate in cc/sec K is a permeability of a rock or any sample A is the cross sectional area ∆P is the pressure difference ( atm ) µ is the viscosity ( cP ) L is the length of the sample ( cm ) Units: The  SI  unit for permeability is m 2 . A practical unit for permeability is the  darcy  (d), or more commonly the  millidarcy  ( md ) 1 darcy = 9.86 × 10 −13 m²

9. Absolute and Effective Permeability : Absolute Permeability is the permeability or measurement of the ability to flow or transmit through a sample when only a single fluid or phase is present in the sample. Absolute permeability is constant for a particular medium and independent of the fluid type. Effective Permeability is the ability to flow through a sample  when other immiscible fluids are present in the rock sample. The relative saturations of the fluids as well as the nature of the reservoir affect the effective permeability.

10. FACTORS AFFECTING POROSITY CEMENTATION FACTOR SORTING OF PARTICLES DEPTH ORIENTATION PRESENCE OF REACTING FLUID

11. FACTORS AFFECTING PERMEABILITY ( i ) Properties of pore fluid (ii) Size and shape of particles (iii) Void ratio (iv) Structural arrangement (v) Degree of saturation (vi) Adsorbed water (viii) Stratification

12. Thank You