Production optimization

Production Optimization
January 21, 2016
Win Nyunt Aung
Production Engineer
Operation and Maintenance Team 1
Petroleum Operations Division

Categories:
 What is Optimization?
 Well Performance and System Analysis
 Production System
 Reservoir Fluid
How do we get hydrocarbons to surface?
Tubing Performance (Vertical Lift)
Tubing Size Selection
 System Analysis (Using Nodal Analysis)

 Understand the components of Inflow Performance
 Understand the components of vertical lift Performance
 Understand combination of Inflow & vertical lift
performance
Objectives

Production Optimization
 Production Optimization means… Balance between Production rate /
Deliverability and demand
 Production Optimization includes a good understanding about Production
Systems and Reservoir Fluid

Well Performance & Production System

Reservoir Fluid
 Phase Behavior
 Dry gas / Wet Gas, Condensate, Oil, Water
 Fluid Properties
 Gas Properties
 Liquid Properties
 Laboratory Measurements
 Composition
 Constant Volume Depletion

Phase Behavior
 The reservoir fluid can be classified into basically three types
i.e., single phase, two phases, or a combination.
 Such information is used to determine the type of IPR equation
to be used.
 From a technical point of
view, the various types of
reservoirs can be
defined by the location
of the initial reservoir
temperature and pressure
as commonly shown on
pressure-temperature …
(PT) phase diagrams.

Segments
 Rock Properties & Reservoir character
 Reservoir Fluid qualities
 Reservoir flow paths
 The effect of pressure drop and back pressure on fluid flow in the Reservoir
 Fluid behavior in approach / entry to the wellbore
 Lift type and Optimization of flow from bottom hole through the tubing
 Operations effect on the flow rate…
 Choke setting
 Restrictions
 Separator operations
 Pipeline
 Start up/ shut down operations, stabilizing

System AnalysisSystem Analysis
 Well deliverability is
determined by a well’s inflow
performance.
 The Inflow Performance
Relationship (IPR) is defined as
the functional relationship
between the production rate
and the bottom hole flowing
pressure.
 Productivity Index (PI or J)
expresses the ability of a
reservoir to deliver fluids to the
wellbore.
 Productivity Ratio (PR) is the
ratio of actual productivity
index to the ideal productivity
index where skin, s=0.
Reservoir Deliverability System

Inflow Performance & Productivity Index
 A commonly used measure of the ability of the well to produce
…is Productivity Index
 Defined by the symbol “J”, it is ratio of the total fluid flow rate to
the pressure drawdown….
 Drawdown (∆P) = (Pr- Pwf)
In generally,
 PI = J = Q/ ∆P
 PI = Productivity Index
 Q = Flow rate,
 ∆P = Pressure drawdown,
 Pr = Average drainage pressure (static),
 Pwf = bottom hole flowing pressure,
System Analysis

In Flow Performance Relationship - IPR Curves
 The Inflow Performance Relationship (IPR) for a well is the
relationship between the flow rate of the well q and the flowing
pressure of the well Pwf.
 In single phase flow this is a straight line but when gas is moving in
the reservoir, at a pressure below the bubble point, this in not a linear
relationship.

Tubing Performance (Outflow Performance)

 Picture yourself at the bottom of the flowing well ……
Now this time …… Look up into the tubing ……
 What would prevent flow from the well?
 What would make this well produce more?

 The outflow system takes energy from the inflow system and
use that energy to get the total fluid rate to surface
 For the outflow system, the higher the pressure at the bottom
of the well, the more fluid can be pushed from the well
( In order to overcome friction)

 Another convenient view of the Outflow is on a Depth Vs. Pressure
graph (These are pressure in the tubing)

Factor Affecting Vertical Lift
 Flowing Tubing Pressure
 Length of Tubing (Depth)
 Friction factors
 Tubing Diameter (ID)
 Fluid Composition (Liquid / Gas)

Inflow Performance Relationship (IPR) & Tubing Performance Curves
System Analysis (Combination of Inflow Vs. Outflow)

 IPR & TPR curves can be combined to find the
Stabilized Flow Rate (Point of Natural Flow)
 Tubing shoe reaches the perforation depth****
 Wellbore flowing pressure and tubing intake pressure
are considered at the same depth
 At a specific rate when these two pressures are
equal, the flow system is in equilibrium and
flow is Stable

 Flowing bottom hole pressure (Pwf) = Tubing intake pressure(Pwf e)
… the stable flow rate***

Production Rate & Tubing Sizing

Production Rate & Wellhead Pressures

Production Optimization using Nodal Analysis

Production Optimization Using Nodal Analysis
Well deliverability is determined by the combination of well inflow
performance and wellbore flow performance.
This work focuses on prediction of achievable fluid production rates from
reservoirs with specified production string characteristics.
The technique of analysis is called ‘‘Nodal analysis’’.
 Its application to well producing systems was first proposed by Gilbert
(1954).

Applications
Typical Applications include:
 Estimation of flow rates
 Selection of Tubing size
 Selection of Flowline size
 Selection of Wellhead pressure & surface choke
 Artificial Lift Design
 Estimation of the effects of reservoir pressure depletion
 Identification of flow restrictions

Optimization Procedure
 Identify the components in the system
 Select one component to be optimized
 Select the node location that will best emphasize the effect of change
 Develop expression for inflow and outflow
 Calculate pressure drop versus rate for all components
 Determine the effect of changing the characteristics of the selecting
component
 Repeat the procedure for each component
 Optimize the production system

Start Select Model
Options
Set up and Match
PVT Model
Input System
Equipment & IPR
Yes
Match IPR &
VLP
Calculate System
Sensitivities
Performance
Acceptable?
Review
Design
Finish

Production
Optimization
Production
Optimization
Nodal Analysis
 To simulate the fluid flow in the system, it is
necessary to ‘‘break’’ the system into discrete
nodes that separate system elements (equipment
sections). Fluid properties at the elements are
evaluated locally.
 Nodal analysis is performed on the principle of
pressure continuity, that is, there is only one
unique pressure value at a given node regardless
of whether the pressure is evaluated from the
performance of upstream equipment or
downstream equipment.
 The performance curve (pressure–rate
relation) of upstream equipment is called ‘‘inflow
performance curve’’;
the performance curve of downstream equipment
is called ‘‘outflow performance curve.’’
 The intersection of the two performance curves
defines the operating point, that is, operating flow
rate and pressure, at the specified node.

Production
Optimization
IPR & VLP Plot
Before Optimization
97 MMscf/day

Production
Optimization
Effect of tubing size
79 MMscf/day
91 MMscf/day
104 MMscf/day

Production
Optimization
Effect of Wellhead pressure
76
MMscf/day
94
MMscf/day
101
MMscf/day

Production
Optimization
Effect of water cut
97 MMscf/day
80 MMscf/day

Production
Optimization
Skin Effect
114 MMscf/day
84 MMscf/day

Production
Optimization
After optimization
Specifications:
Tubing size: 6.18 inch
Wellhead pressure: 2000 psi
Assumptions:
Water Cut: 5%
Skin Factor: +1

Results
 During the production, chosen well with tubing Size of 3.95" and 4.78" causes
restriction because of tubing. But the production rate increases at the production with
tubing Size of 6.18".
 According to production potential of the well and reservoir and Capacity of surface
equipment Wellhead Pressure 2000 psi for the well is appropriate.
 If the creation restriction in bottom hole completion or Formation damage, inflow
performance can be Improve using the Work Over Such as Hydraulic Fracturing or
Acidizing.
 According to formation stability (type and structure of reservoir rock), completion by
the method of open hole is appropriate and there’s no need to mechanical integrity in
the junction.

Commonly Accepted Correlations

Computer Programs for System Analysis

Production optimization

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