2. Ppo - Reservoir Performance - Part 1 - S92018

PETROLEUM PRODUCTION AND OPTIMISATION PDB 4313

RESERVOIR PERFORMANCE - PART 1

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PETROLEUM PRODUCTION AND OPTIMIZATION By

HAIZATUL HAFIZAH HUSSAIN [email protected] Office Ext. : 7373 Office : J3-02-25

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LEARNING OUTCOMES At the end of this lecture, students should be able to:

 Describe the interaction of the reservoir system and its effect on the overall production system.

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LECTURE CONTENTS  Well performance equations - Darcy’s Law  Productivity Index Concept

 Factors affecting productivity index and IPR

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INTRODUCTION What causes well to flow?

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INTRODUCTION What causes well to flow? Drawdown (𝑷𝑹 − 𝑷𝒘𝒇 )

OR Suck from the ROCK!!

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WELL PERFORMANCE EQUATIONS

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WELL PERFORMANCE EQUATIONS DARCY`S LAW

Where:

𝒌𝑨 𝒒=− ∆𝒑 𝝁𝑳

 q = flowrate, cm3  k = formation permeability, darcies  A = cross-sectional area, cm2  -∆𝑝 = pressure drop, atmospheres

This is effectively a friction pressure drop relationship with the addition of permeability to account for the flow resistance of the sand

 μ = fluid viscosity, centipoise  L = pipe length, cm

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WELL PERFORMANCE EQUATIONS DARCY`S LAW LINEAR FLOW – for constant area open to flow Table 1: Units for Darcy’s Law

𝑞=

𝐶𝑘𝐴 𝑝1 −𝑝2 𝜇𝐿

𝑞 = −0.001127

𝑘𝐴 ∆𝒑 𝜇𝐿

Variable Symbol Flow rate q Permeability k Area A Pressure drop -∆p Viscosity µ Length L

Units Darcy Field cc/sec bbl/day darcys md cm2 ft2 atm psi cp cp cm ft

Where C is a unit conversion factor. The value for C is 1.0 for Darcy Units and 1.127 x 10-3 for Field Units.

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WELL PERFORMANCE EQUATIONS DARCY`S LAW RADIAL FLOW  Calculate flow into a well where the fluid is converging radially into a relatively small hole.  Area open to flow not constant. Figure 1: Radial flow system (Beggs 2003)

The cross-sectional area open to flow at any radius is 𝐴 = 2𝜋𝑟ℎ 10

WELL PERFORMANCE EQUATIONS DARCY`S LAW OIL FLOW For steady state laminar flow condition

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WELL PERFORMANCE EQUATIONS DARCY`S LAW OIL FLOW For pseudo-steady state flow condition

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WELL PERFORMANCE EQUATIONS DARCY`S LAW GAS FLOW For stabilized flow, PSC

=

14.7 psia and TSC = 5200R

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PRODUCTIVITY INDEX CONCEPT

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PRODUCTIVITY INDEX CONCEPT  Productivity index (PI) is defined as flowrate divided by reservoir pressure drop (drawdown).

 In simple word, PI means how easily fluid flow through the rock.

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EXERCISE A well that is producing from a reservoir having average pressure of 3200 psig produced at a rate of 290 STB/day when bottomhole flowing pressure was 2450 psig. Calculate: 1.

The productivity index (PI)

2. The producing rate if Pwf is decreased to 2180 psig

3. The bottomhole pressure necessary to obtain an inflow of 350 STB/day 4. The inflow rate if Pwf is reduced to zero (AOF or Qomax) 16

PRODUCTIVITY INDEX CONCEPT

Figure 3: Semi-log plot of pressure vs. radius (Beggs 2003)

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PERMEABILITY ALTERATION AND TURBULENCE

Figure 4: Effects of altered permeability (Beggs 2003) 18

SKIN

Figure 5: Effects of skin factor (Beggs 2003) 19

FACTORS AFFECTING PRODUCTIVITY INDEX Permeability

Reservoir Thickness

𝑘ℎ 𝑃𝐼∞ 𝜇

Viscosity

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FACTORS AFFECTING IPR  A decrease in kro as gas saturation increases  An increase in oil viscosity as pressure decreases and gas is evolved

 Shrinkage of the oil as gas is evolved when pressure on the oil decreases  Formation damage or stimulation around the wellbore

 Depletion

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DRIVE MECHANISMS Dissolved gas drive

Gas cap drive

Water drive

Combination

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SUMMARY  Well performance equations - Darcy’s Law  Productivity Index Concept

 Factors affecting productivity index and IPR

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Have you achieved the learning outcomes today? Any thoughts? 24

THANK YOU

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