Upload
shagun-devshali
View
508
Download
93
Embed Size (px)
DESCRIPTION
It deals with all the well permanences and methods in detail.
Citation preview
Well Performance
Introduction
What is Well Performance?
It is the ability of a well to produce desired fluids
Factors Responsible for Well Performance?
The overall health of a well depends on:• Geological Aspects
• Drilling Aspects
• Cementing
• Log interpretation
• Mechanical aspects of casing & tubing
• Drive mechanism
Factors Responsible for Well Performance……..
• Geological Aspects– Dip
– Faults
– Oil-water contact
– Gas-oil contact
– Porosity, permeability, fluid saturation, pay thickness, pressure etc.
Factors Responsible for Well Performance……..
• Drilling Aspects– Mud loss
– Stuck string
– High and / or low pressure formations
– Drilling fluid – weight, composition etc
Factors Responsible for Well Performance……..
• Cementing– Composition
– Bonding properties
– Success of cementation job
– Cement rise behind casing
Factors Responsible for Well Performance……..
• Log interpretation– HC bearing formations
– Estimation of thickness
– Preciseness of perforation
– Porosity and water saturation determination
Factors Responsible for Well Performance……..
• Mechanical aspects of casing & tubing– Collapse (important in tectonic zones)
– Corrosion– Leakage (fluid produced)
– Damage (repeated milling etc.)
– Stuck up (Fishing etc.)
Factors Responsible for Well Performance……..
• Drive mechanisms– Solution gas drive
– Water drive
– Gas cap expansion drive
– Compaction drive
– Combination drive
Factors Responsible for Well Performance……..
• Reservoir properties– Porosity– Fluid saturation – Permeability
• Absolute• Relative
– Mobility & mobility ratio– Solution gas oil ratio
Methods of Well Performance
IOGPT
Productivity Index
• Productivity index is the ratio of flow rate to draw down. It is indicative of well’s production potential. Denoted by ‘J’
Where Q = total quantity of fluid,Pr = reservoir pressurePwf = Flowing BHPk = permeability, md
srrB
kh
PP
QJ
weoowfr
o
75.0/ln
08.7
)( h = res thickness
re, rw = drainage, well radius, ft
μo = viscosity, cp
Bo = oil FVF
Well’s Potential Indicator
• kh = 0-100 md-ft not a very good well
• kh = 100-1000 md-ft good well
• kh = 1000-5000 md-ft excellent well
Pwf = PrPwf = Pr
PwfPwf
Pwf = 0Pwf = 0
QQ QmaxQmax
Inflow Performance It is basically a straight line or curve drawn
in the two dimensional plane, where X axis is q ( Flow Rate ) and Y axis is Pwf ( Flowing Bottomhole Pressure ).
q
PI = J = -dq / dPPI = J = -dq / dP
Pwf
Inflow PerformanceIPR-When Pr > Bubble Point Pressure :
Combination Constant PI and Vogel Behaviour Case.RATE.
PRESS .
0000
PPwfwf
PPbb
qqqqmaxmax
VOGELBEHAVIOR
CONSTANT J
PPrr
Inflow PerformanceChange Of PI With Cumm. Recovery ( % of Oil In Place ) With Time :
Computer Calculated Inflow Performance Relationships For A Solution Gas Drive Reservoir
PRODUCING RATE , m3/d
BOTTOM-HOLE PRESSURE Kg/cm2
Np/N = 0.1%
2 %
4 %
6 %
8 %
10 %
12 %
14 %
CUMM. REC.,% OF ORIGINAL OIL IN PLACE
27
Pwf
Ql
IPR
Tubing Intake Curves
Operating PointOperating Point
QQLL max max
Pr
28
Tubing Intake Curves
Operating PointsOperating PointsPwf
QlApparent gain
IPR
QQLL max max
Pr
29
Ql
present IPR
Additional gain from stim.
Tubing Intake Curves
Operating PointOperating Point
QQLL max max
Pr
Pwf
PI & IPR
• PI attempts to represent the inflow performance relation of a well as a straight line
• IPR usually declines at greater draw downs. It represents PI tests at several production rates in order to provide a better representation of the true inflow performance relation of the well
Inflow PerformanceVOGEL’S WORK ON IPR :
2
max
8.02.01
r
wf
r
wf
P
P
P
P
q
q
SkinThe skin represents a pressure drop which most commonly arises due to formation damage around the wellbore, caused by drilling mud or cementing or other factors.
ORDimensionless factor
expressing the reduction in the formation permeability compared to the original permeability
Pwf
Pe
Pressure drop due to radial inflow
Pressure drop due to skin
33
Measurement of Skin
Δps = pressure drop across skinB = formation volume factorμ = viscosity, cps = skin factork = permeability, mdh = height, ftq = flow rate, STB/D
rw
rs
re
KKs
h
w
s
s R
R
K
Ks ln1
skh
qBps
2.141
Skin : Effect on Production
- 0 +
Skin effect
Pro
duct
ion
Flow Efficiency(Wellbore Damage Indicators)
Is defined as the ratio of the well’s actual productivity index to its productivity index if there were no skin
Damage Ratio: Inverse of Flow Efficiency
Damage factor = 1- FE =
wfr
swfr
ideal
actual
PP
pPP
J
JFE
swfr
wfr
actual
ideal
pPP
PP
J
J
FE
1
wfr
s
ideal
actual
PP
p
J
J
1
IPR modified by Standing
Well Performance Test Methods
• Periodic Production Tests
• Productivity or Deliverability Tests
• Transient Pressure Tests
Well Performance Test Methods….
Productivity or Deliverability Tests• Productivity Index• Inflow Performance• Flow after Flow• Isochronal
Well Performance Test Methods….
Transient Pressure tests• Pressure buildup• Pressure draw down• Multiple rate• Injection buildup or fall-off• Multiple well interference• Drill stem tests
41
Well Performance
Test Methods…..
Example data forConstant –Rate Pressure Buildup Well
Test
Nodal Analysis or Systems Analysis Approach
• To view the total producing system as a group of components
• Each component of a well system contributes towards the performance of a well.
• To get an improved performance each component is to be analyzed.
• The analysis is done by combining the pressure versus rate behavior of the well components.
43
Nodal Analysis………….
Pressure drops at various components
44
Nodal Analysis……….• Location
of nodes in a well system
Nodal Analysis…………..Each node has one inflow and one outflow
• Flow rate through the component can be determined once the system meets these requirements
Flow into the node equals flow out of the nodeOnly one pressure exists at a node
Nodal Analysis…………..Inflow to the node:
Out flow from the node:
Where Pr = static reservoir pressure
ΔP = pressure drop
Psep = seperator pressure
Pnode = node pressure
nodePcomponentsupstreamP )(Pr
nodesep PcomponentsdownstreamPP )(
Nodal Analysis…………..
Nodal Analysis…………..
Nodal Analysis…………..
Nodal Analysis…………..
51
Reference Material
• Production Operations Vol 1 & 2 by Thomas O Allen and Alan P Roberts
• Fundamentals of Reservoir Engineering by L P Dake• Technology of Artificial Lift Methods by Kernit E Brown• Advances in Well Test Analysis by R C Earlougher• Development in Petroleum Science (Hydrocarbon Exploration
& Production) by Frank Jahn, Mark Cook & Mark Graham• Hydrocarbon Reservoir & Well Performance by T E W Nind• Principles of Oil Well Production by T E W Nind• Fundamentals of Reservoir Engineering by Brian F Towler