drill stem testing
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DRILL STEM TESTING
DRILLING PRACTICES
DRILL STEM TESTING
A TEMPORARY WELL COMPLETION TO GATHER INFORMATION ON THE POTENTIAL PRODUCTIVITY OF A FORMATION.
WHAT IS A DRILL STEM TEST
WHO REVIEWS THE DST PROGRAM
OIM SENIOR TOOLPUSHER OPERATOR REP KEY SERVICE PERSONNEL
KEY AREA’S OF REVIEW
COMMUNICATION ROLES AND RESPONSIBILITIES EMERGENCY RESPONSE
EXPECTED TEST PARAMETERS
• Temperature
• Pressure
• Hazards
REQUIRED CHANGES TO PROGRAM
BASIC PRECAUTIONS
• PRIOR TO CONDUCTING ANY DST THE BOP’S AND GAS DETECTION SYSTEM WILL BE TESTED.
• DRILLPIPE OR TUBING CAN BE USED BUT MUST BE DESIGNED FOR ANTICIPATED CONDITIONS. ANY DOUBT ABOUT THE TEST STRINGS INTEGRITY WILL BE REFERED TO THE RIG MANAGER.
• DURING THE TEST THE ANNULUS PRESSURE WILL BE MONITORED TO ENSURE A LEAK DOES NOT DEVELOP IN THE TEST STRING.
• ALL DST WORK WILL USE A SURFACE TREE THAT ENABLES THE TEST STING TO BE CLOSED IN.
• WHEN WIRELINE IS TO BE USED DURING THE TEST A LUBRICATOR WILL BE INSTALLED ON SURFACE STACKS.
• WHEN A DST IS FINISHED, CONTENTS OF TEST STRING ARE REVERSE CIRCULATED OUT PRIOR TO RELEASE OF PACKER OR UNSTINGING FROM PERMANENT SET PACKER.
• SPECIAL ATTENTION SHOULD BE EMPHASISED FOR H2S DETECTION.
SPECIAL PRECAUTIONS FOR FLOATERS
• TEST STRING HUNG OFF IN BOP’S WITH A SUBSEA MASTER VALVE INSTALLED (E-Z TREE OR SUBSEA TEST TREE).
• ENSURE TIME IS KNOWN FOR UNLATCHING IN EVENT OF AN EMERGENCY.
• TEMPORARY ABANDONMENT THE BLIND RAMS WILL BE CLOSED ABOVE THE MASTER VALVE.
• ENSURE ENOUGH HIGH PRESSURE FLEXIBLE LINES ARE USED TO COMPENSATE FOR MAX HEAVE.
PRECAUTIONS WHILE TESTING
• FOR INITIAL TEST OF A ZONE, DST TOOLS MUST NOT BE OPENED AT NIGHT WITHOUT THE PERMISSION OF THE OPERATIONS MANAGER. THE REGION MANAGER MAY DECIDE THAT THIS DECISION WILL BE MADE AT REGIONAL LEVEL.
• WHEN TEST WELLS CONTAINING H2S NO GAS SHOULD BE RELEASED INTO THE ATMOSPHERE
UNLESS IT IS BURNED ON THE SPOT.
• ALWAYS OPEN UP A WELL SLOWLY, USING THE UPPER MASTER VALVE.
• AN EMERGENCY SURFACE SHUT-DOWN SYSTEM (ESD) SHOULD BE INCORPERATED INTO ANY WELL TEST HOOK UP.
• ALWAYS PRESSURE TEST THE INSTALLED EQUIPMENT, PRIOR TO OPENING UP THE WELL.
• SPACING OF UNITS INVOLVED IN WELL TEST HOOK-UP SHOULD BE AS PER RECOMMENDED SAFETY STANDARDS.
• WIND DIRECTION OR NO WIND NEEDS TO BE CONSIDERED.
• MINIMISE RISKS WITH IGINTION SOURCES BY GROUNDING UNITS, NO NAKED FLAMES ETC.
REASONS TO DO A DRILL STEM TEST
WE NEED TO KNOW :
• IF THERE IS A RESERVOIR
• WHAT DOES IT CONTAIN
• AT WHAT RATE WILL IT PRODUCE
• FOR HOW LONG
• WHAT FACILITIES WILL BE REQUIRED AND WHEN
• WHAT HAZARDS ARE THERE
KNOWLEDGE+
RISK
LOW
HIGH
KNOWLEDGE vs RISK
Data Source Possible Analysis
Seismic Identify possible Accumulations
Regional Information Qualitative Accumulation size and shape using assumed
Velocity Profile
Hydrocarbon Prospectivity (Seismic oddities / regional information)
Degree Of Development Uncertainty = Very High
PRE-DRILLING PHASE
Data Source Possible Analysis
Mud Log Lithology Hydrocarbon Shows Geological ProfileCore Samples Depositional EnvironmentMWD Logs Qualitative Hydrocarbons
Pressure Regime (Qualitative) Formation Characteristics at the wellboreFluid ContactsNear-wellbore petrophysical parameters
Degree Of Development Uncertainty = High
DRILLING A WELL
Data Source Possible Analysis
Well Logs Near-well formation characteristics VSP Hydrocarbon ContactsRFT Samples Lithology
Qualitative HC mobility Qualitative presence of hydrocarbons (HC)
Confirm Seismic velocity profileFirm-up structure mappingQuantitative Pressure regimeQualitative HC PVT analysis
Degree Of Development Uncertainty = High
OPEN HOLE LOGGING
Data Source Possible Analysis
Transient Pressure Response Near-well formation characteristics
Samples Near-Well Productivity Index
Additional qualitative PVT analysis
Degree Of Development Uncertainty = High
LIMITED INFLUX TESTING
Data Source Possible Analysis
Transient pressure response Bulk reservoir propertiesPseudo Steady State Response Near-well boundaries Bulk HC Samples Ideal Productivity Index
Extended HC PVT AnalysisTrace Element analysis (qualitative)Processing characteristics of the HCFormation Integrity (sanding
tendency under high drawdown)
Degree Of Development Uncertainty = Medium
CONVENTIONAL WELL TESTING
Data Source Possible Analysis
Steady State Pressure Response Establish Reservoir extent Surface Process Monitoring Pressure support mechanisms Wellsite Chemistry Development Strategy
Optimise Process Facility designMeasure Completion PerformanceCalibrate design programs, etc.Stabilised trace element analysis
Degree Of Development Uncertainty = Medium / Low
EXTENDED WELL TESTING
Test programs
Planning and preparation• For conventional wells, 2 - 3 months from expected TD• For unconventional operations ( HPHT, EWT etc.), 6 - 12 months
Testing operations start once the the well has its final casing/liner string in place and final logs have been run.
TIMING
Drilling vs Testing
– During conventional drilling, the mud weight is adjusted such that the hydrostatic pressure of the fluid counteracts the reservoir pressure
• Overbalanced situation, zero hydrocarbon flow to surface.
– During conventional testing, the fluid positioned above the reservoir creates a hydrostatic pressure which is less than the reservoir pressure.
• Underbalanced situation, reservoir fluids can now flow to surface
TESTING OPERATION
• Function of DST tools
– Isolation of producing interval from mud hydrostatic
– Test “Cushion” - lighter fluid than mud hydrostatic fluid column
– Down hole shut-in valve to minimise wellbore storage
– Reverse valves to “kill” the well at the end of the test
– Slip joints to compensate for tubing length changes due to
temperature & pressure changes
DRILL STEM TEST TOOLS
PERFORATING GUNS
PACKER
SAFETY JOINT / JAR
MEMORY GAUGES
DOWNHOLE SHUT IN VALVE
DRILL COLLARS
PRIMARY REVERSE VALVE
DRILL COLLARS
DRILL COLLARS
SECONDARY REVERSE VALVE
SLIP JOINT, CLOSED
SLIP JOINT, FULLY OPEN
SLIP JOINT, 1/2 OPEN
RA SUB
DST TOOLS
• Operating methods
– Tools are operated by
• String manipulation / rotation• Applied pressure to the annulus• Annular pressure• Tubing pressure
– Below packer and inside tubing - hydrocarbons– Above packer in casing tubing annulus - kill weight fluid
+ any applied pressure
DST TOOLS
• Function of Sub Sea Landing String
– On a semi-sub or drill ship the test string requires additional components for safety & operational reasons.
• Sub Sea Test Tree, Retainer Valve– Provides the ability to isolate the tubing in the stack and
disconnect without killing the well.
• Lubricator Valve– Provides the ability to run extended length tool strings
without long sections of lubricator riser at surface.
SUBSEA SYSTEMS
TEST TREE
FLUTED HANGER
SLICK JOINT
VALVE ASSEMBLY
LATCH ASSEMBLY
SUBSEA TEST TREE & VALVE ASSEMBLY
COMPONENTS OF THE LANDING STRING
LATCHED UNLATCHED
SURFACE TREE
SWIVEL
LANDING STRING
SLICK JOINT
FLUTED HANGER
SPACER SUB
SUBSEA TEST TREE
SUBSEA TEST TREE LATCH ASSEMBLY
RETAINER VALVE
HOSE PROTECTOR
LUBRICATOR VALVE
HYDRAULIC HOSE REEL
CONTROL CONSOLE
RETAINER VALVE CLOSED
SUBSEA TEST TREE UNLATCHED
RAMS CLOSED
SUBSEA TEST TREE VALVES
CLOSED
• Function of Well Test Equipment
– Management of pressure reduction from well to disposal system
– Heating if required of produced fluids
– Removal of any produced solids
– Separation of produced Oil, Water & Gas
– Disposal of produced fluid
– Data acquisition, flow rates, pressures & fluid samples
WELL TEST EQUIPMENT
GENERAL LAYOUT OF WELL TEST EQUIPMENT
Courtesy of Expro Group
• Function
– Primary pressure drop , flow control– Consists of an “adjustable” and a “fixed”
choke – Size of choke is usually given in 64ths of
an inch, equivalent bore– Adjustables used for clean-up period– Fixed used once pressure has stabilised
DIRECTION OF FLOW
ADJUSTABLE CHOKE TIP
CHOKE MANIFOLD
Adjustable choke
Fixed choke
• Function
– To increase the temperature of the produced fluid downstream of the choke manifold
• Improved separation efficiency
– To provide a choke in a heated environment• Avoidance of hydrate formation
HEATER
HEATER
WELL FLUID INLET
WELL FLUID OUTLET
STEAM INLET
BYPASS
STEAM OUTLET
SAFETY VALVE
DRAIN
CHOKE
• Function
– Separation of produced oil, water & gas
– Rate measurement of produced fluid
– Provision of sampling points for re-combination samples
SEPARATOR
HORIZONTAL SEPARATOR
Horizontal Separators
Primarily used for high liquid content wellsCourtesy of Expro Group
Vertical Separators
Primarily used for high gas content wells Courtesy of Expro Group
OIL BURNER
Courtesy of Expro Group
Outline procedure
• Run scrapers across packer setting depth• Condition drilling mud or displace to brine • Run junk basket• BOP test• Space out run for sub-sea tree
Courtesy of Expro Group
PREPARATION
TOOLS & SUB-SEA EQUIPMENT PREP
• Outline procedure
– Layout tools– Function and pressure test– Drift tools– Strap lengths of tools– Strap lengths of tubulars– Drift tubulars– Prepare running “tally”
ROTARY TABLE (RKB)
LAND-OFF POINT IN WELLHEAD
RESERVOIR FEATURE OR RA TAG
RA SUB IN TEST STRING
DISTANCE FROM RA SUB TO TOPSHOT
SURFACE WELL TEST EQUIPMENT PREP
• Outline procedure
– Position equipment on rig deck
– Connect equipment using service pipe work
– Prepare instrument control and data acquisition equipment
– Pressure & function test equipment
– Function test safety system
– Prepare sampling equipment
RUNNING PROCEDURES
• Typical Procedures on a Semi-sub
– Pick up and run TCP guns and DST tools• Check strap length between top shot and RA tag• Pressure test BHA
– Run tubing• Pressure test tubing
– Perform space out / correlation– Pull back to sub-sea hang off point– Run subsea equipment– Pick up and make up flowhead
RUNNING PROCEDURES
• Typical procedures on a semi-sub
– Set packer
– Correlation run to confirm packer setting depth
– Pressure test landing string tools and surface tree & choke
– Function open tester valve and prepare to perforate well
TEST PROGRAM
• Test program determined by test objectives
• Typical test program– Perforate - minimal flow– Down hole shut in to determine initial reservoir pressure– Clean-up flow– Initial build up– Single rate or multi rate flow period(s)– Main shut-in
TESTING PROGRAM
• Typical test program
– Sampling flow period
– Well kill
– Pull test string
– Validate gauge data
– Abandon well
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