Chapter 1 Introduction(1)

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SKPP 3513 – PRODUCTION ENGINEERING

Chapter 1: Introduction Mohd Fauzi Hamid N01A-18 07-5535616 [email protected]

SKPP 3513: PRODUCTION ENGINEERING

Course Learning Outcomes Apply the appropriate procedures to ensure optimal initial production. Analyze the process of delivering the reservoir fluid to the surface. Design and select the gas lift system and separator sizing. Able to use and organize up-to-date resources to analyze complex petroleum engineering problems, and demonstrate a good communication skill through report writing or presentation.

CHAPTER 1: INTRODUCTION

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References (1) Boyun Guo, Lyons, W. C. and Ali Ghalambor (2007). Petroleum Production Engineering: A Computer-Assisted Approach. Elsevier. (2) Nind, T.E.W. (1981). Principles of Oil Well Production. 2nd ed. London: McGraw-Hill. (3) Brown, K.E., (1967). Technology of Artificial Lift Methods. Vol.1, 2 & 3. Tulsa: PennWell Publishing. (4) Golan, M. and C.H. Whitson (1991). Well Performance. New Jersey: Prentice Hall. (5) Bradley, H.B. (1987). Petroleum Engineering Handbook. Richardson, Texas: SPE .

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Assessment

• • • • • •

Test 1 Test 2 Assignment Quiz 1 Quiz 2 Final Exam

CHAPTER 1: INTRODUCTION

= = = = = =

12.5 % 12.5 % 10.0 % 7.5 % 7.5% 50.0%

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Contents

 What is Petroleum Production Engineer?  What is Petroleum Production Engineering?  Fluid Inflow  Formation Pressure  Separator Pressure

 NODAL Analysis

CHAPTER 1: INTRODUCTION

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Petroleum Production Engineer  Main function of petroleum production engineer:  To evaluate and predict the performance of the well.  To predict the requirement of artificial lift. If required, when?  Producing oil well involving:  the reservoir  the well itself  the surface facilities  The successful production engineer need to have sound knowledge of reservoir engineering, and will be fully conversant with advances in oil well and surface equipment technology. CHAPTER 1: INTRODUCTION

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Petroleum Production Engineer (ctd)  The production engineer is ever cognizant of the necessity to produce the maximum amount of oil and gas from the reservoir.

 This work requires knowledge of the physical properties of the reservoir and its entrapped fluids.

 For this reason, then, the production engineer will tests the wells and takes samples of both reservoir rock and fluids in order to determine the effect of production upon the oil reservoir.

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 There are two questions need to be answered:  What is the well current production?  What is the well production if the production situation has change?  The questions can be answered by carried out the production test after the well has been completed. The regular study and analysis of the well test is useful for:  Monitoring the well performance  Monitoring the reservoir performance  The first test after the well has been completed can be used to identify:  Type of reservoir fluid or hydrocarbon exist  Production flow rate. CHAPTER 1: INTRODUCTION

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 Therefore need system to analyze performance of system composed multiple interacting component analysis or nodal analysis.

CHAPTER 1: INTRODUCTION

system

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Petroleum Production Engineering  What is Petroleum Production Engineering?  A subject that study the technique or method of producing petroleum fluid from reservoir to surface, i.e. to surface facilities (separator, treater and storage tank)  Main concept: The flow rate that can produce maximum petroleum output with specific production system: qoptimum.  Production System Schematic. Figure 1 shows a petroleum production system of a well, which can be divided into three stages and it behavior can be evaluated by three performance indicators, which are:

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 Fluid flow from reservoir to the well bore.  Flow through porous media: Darcy Law (across the reservoir)  Performance evaluation - IPR

 Fluid flow from the well bore to surface.  Flow through vertical pipe/annulus (across tubing & any restrictions)  Well performance evaluation – VLP/TP

 Fluid flow from wellhead to separator and other surface facilities.  Flow through horizontal pipe/flow line  Across the surface choke  Performance evaluation – CP CHAPTER 1: INTRODUCTION

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Schematic Petroleum Production System CHAPTER 1: INTRODUCTION

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CHAPTER 1: INTRODUCTION

A sketch of a petroleum production system (13)

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Pressure Losses @ Production System  Can be grouped into 3 main components:  Total pressure loss in the reservoir & completion  Total pressure losses in the tubing  Total pressure losses at the surface.

Figure 2: Pressure Drops in Production Process

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Pressure Losses During Production CHAPTER 1: INTRODUCTION

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Total Pressure Drop  Sum of:  Loss in reservoir (porous media): DP1 = Pr - Pwfs  Loss @ completion (perforation, liner, etc): DP2 = Pwfs - Pwf  Loss in tubing: DP3 = Pwf - Pwh  Loss in flowline, choke, etc: DP4 = Pwh - Psep  Total pressure loss:  DPT = Pr – Psep = DP1 + DP2 + DP3 + DP4

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Pressure Across Production System

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CHAPTER 1: INTRODUCTION

A sketch of a typical flowing oil well (18)

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CHAPTER 1: INTRODUCTION

A sketch of a wellhead (19)

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Fluid Inflow  Fluid inflow is the flow of liquid from formation to the bottom hole.  The flow of liquids are affected by 4 main factors:  Reservoir fluid properties (physical & chemical properties). P, T, composition, etc.  Physical & Geometrical properties of reservoir rocks. P, T, composition, structure, over burden, cementing, compaction, etc.  Pressure differential (DP = Pf – Pw)  Well geometry, spacing, production area @ Pf

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 It is essential for an engineer to understand the basic theory of fluid flow through porous media especially the relationship between steady-state, pseudosteady-state and unsteady-state flow.  An equation that express the fluid flow through porous media – Darcy equation.  For horizontal single phase and incompressible flow:

v

q k dp  A  dl

………... (1-1)

where: q/A = rate of flow per unit cross-sectional area across a rock surface of area A CHAPTER 1: INTRODUCTION

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-dP/dl = rate of pressure drop in the overall direction of flow  = viscosity of the fluid

 Steady-state Flow  There is no substance accumulated in the flow system, or the mass flow rate into the reservoir equal to the mass flow rate out from the reservoir. (flow condition do not change with time) (pressure at any point in the reservoir remain constant over time).  Usually found in:  strong water drive reservoir  large gas cap drive reservoir  secondary recovery CHAPTER 1: INTRODUCTION

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 For linear flow: q

0.001127kA( Ps  Pwf )

 Bo L

………... (1-2)

 For single phase radial flow, homogenous formation, and incompressible fluid:

q

0.007082kh ( Ps  Pwf ) ………... (1-3) re  Bo ln( ) rw

where: q = flow rate, STB/d

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q = flow rate, STB/day 0.007082kh ( Ps  Pwf ) q  k = permeability, md r  Bo ln( e ) h = thickness, ft rw  = fluid viscosity, cp rw = well radius, ft re = drainage radius, ft Bo = formation volume factor, bbl/STB Ps = static pressure, psi Pwf = flowing bottom-hole pressure (flowing BHP), psi

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 Unsteady-state Flow  The flow rate and/or pressure change with time.  Pseudosteady-state Flow  A special case of unsteady-state flow or steady state from boundary-dominated reservoir.  When the pressure at any point in the reservoir declines at the same constant rate over time.

q

CHAPTER 1: INTRODUCTION

0.007082kh ( Ps  Pwf ) r 1  Bo (ln e  ) rw 2

………. (1-4)

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 Pseudosteady-state Reservoir  No fluid flow occurs across the outer boundary. So the production of fluids must be compensated for by the expansion of residual fluids in the reservoir. In such a situation, production will cause a reduction in pressure throughout the reservoir unit. Reservoirs in this situation are described as pseudosteady-state or semi steady-state.

 In terms of average drainage area pressure (Pavg or Pr): q

CHAPTER 1: INTRODUCTION

0.007082kh ( Pr  Pwf ) ………. (1-5) re 3  Bo (ln  ) rw 4

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Formation Pressure 

The average pressure within the drainage boundary is often called the average reservoir pressure.



This pressure controls the flow through a production system and is assumed to remain constant over a fixed time interval during depletion.



When this pressure changes, the well's performance changes and thus the well needs to be re-evaluated.



The average reservoir pressure changes because of normal reservoir depletion or artificial pressure maintenance with water, gas, or other chemical injection.

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Separator Pressure 

The separator pressure at the surface is designed to optimize production and to retain lighter hydrocarbon components in the liquid phase.



This pressure is maintained by using mechanical devices, for example, pressure regulators.



As the well produces or injects, there is a continuous pressure gradient from the reservoir to the separator.



It is common to use wellhead pressure for the separator pressure in production system analysis calculations assuming that the separator is at the wellhead or very close to it.

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NODAL Analysis 

Also known as system analysis and very robust and flexible method of analysis.



Consist of:  Selecting a point or node within the production system  Derive & developed equation : relationship between flowrate (q) & pressure drop for a node and a well production system (upstream and downstream). • Flow into the node (inflow) = flow out of the node

• •

(outflow) Only one pressure can exist at the node Fixed reservoir pressure – Pr (starting point) & separator pressure – Psep (end point)

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SKPP 3513: PRODUCTION ENGINEERING

NODAL Analysis (ctd) 

General objectives: 



To combine various production system components @ individual well to estimate production rates and optimize the production system components

Specific objectives:  To determine q @ producing well will naturally produced  To determine under what flow conditions well will load or die  To select most economical time for artificial lift installation and to assist in optimum lift method selection

 To optimize system to produce the objective q most economically

 To check each well system component to determine whether it is restricting q unnecessarily

 To permit quick recognition to increase q CHAPTER 1: INTRODUCTION

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NODAL Analysis (ctd) 

A node is any point in the production system (Fig. 4) between the drainage boundary and the separator, where the pressure can be calculated as a function of the flow rate.



The two extreme nodes in the complex production system are the reservoir drainage boundary (8) and the separator (1).



The pressures at these nodes are called the average reservoir pressure (Pr) and the separator pressure (Psep).

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Fig. 4: Location of various nodes CHAPTER 1: INTRODUCTION

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NODAL Analysis (ctd) 

The other two important nodes are the bottom hole (6), where the bottom hole flowing pressure (Pwf) is measured by a down hole gauge, and the wellhead (3) where the wellhead pressure (Pwh) is measured by a gauge attached to the X-mas tree or the flow arm.



If the pressures are measured or calculated at each node, then the pressure loss between the nodes can be calculated as a function of the flow rate.



Nodes (2, 4, and 5 in Fig. 4) where a pressure drop occurs across the node due to the presence of a choke, restrictions (safety valves), and other piping components are called the functional nodes.

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SKPP 3513: PRODUCTION ENGINEERING

NODAL Analysis (ctd) 

For each component in the production system, for example the porous medium, completion tubulars and chokes, the flow rate (q) is functionally related to the pressure differential (∆p) across the component.

q = f(∆p) 

Nodal analysis in petroleum engineering is the system analysis for determination of fluid production rate and pressure at a specified node.



The analysis require the construction of performance curve (pressure-rate relation) of upstream equipment (inflow performance curve), and performance curve of downstream equipment (outflow performance curve).

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NODAL Analysis (ctd) 

The intersection of the two performance curves defines the operating point, that is, the operating rate and pressure, at the specified node.



Nodal analysis is usually conducted using the bottom-hole or wellhead as the solution node.



Bottom-hole: the inflow performance curve is IPR and outflow performance curve is TPR.



Wellhead: the inflow performance curve is WPR and outflow performance curve is CPR.

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SKPP 3513: PRODUCTION ENGINEERING

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General Analysis 

Production system must be analyzed as a unit or system.



The nodal analysis allows the production system to be divided at point/node of interest for evaluation At node/point  inflow section (upstream) & outflow section (downstream) Within the section: express relationship of P vs q When: q @ inflow = q @ outflow, and P @ inflow = P @ outflow,  continuity condition satisfied,  what is P & q @ system? P @ inflow : Pr - DPu = Pn P @ outflow : Psep + DPd = Pn Plot node P vs q (inflow and outflow curve), intersection between inflow & outflow provide required continuity.







  

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



If node at wellhead:  Inflow to node: Pr - DPres - DPtubing = Pwh  Outflow from node: Psep + DPflowline = Pwh  Continuity: inflow = outflow If node at wellbore (Pwf):  Inflow to node: Pr - DPres = Pwf  Outflow from node: Psep + DPflowline + DPtubing = Pwf

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Darcy Eqn for Radial Flow kA  dP    dR   k 2 h  dP  Q R    dR  dR 2 kh  dP R Q Q

Pe

Pwf h re

rw

where:

rw

pwf

e

e

k = permeability (darcy)

dR 2 kh  R     Q dP r p

h = reservoir thickness (cm)

ln

Q = flowrate

(cm3/sec)

 = fluid viscosity (cp) P = pressure (atm) r

rw 2 kh  Pwf  Pe re Q

Q

= radius (cm)

CHAPTER 1: INTRODUCTION





2 kh Pe  Pwf

 ln  re rw 





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Darcy Eqn for Radial Flow (ctd) Pe

Pwf

In field unit: h re

rw

Q



7.082kh Pe  Pwf

 ln  re rw 



where: Q = flowrate (bbl/day) k = permeability (darcy) h = reservoir thickness (ft)

 = fluid viscosity (cp)

1 bbl

=

159,000 cc

P = pressure (psi)

1 ft

=

30.48 cm

r

1 atm =

= radius (ft)

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