Drill Stem Testing.1

DRILLING PRACTICES DRILL STEM TESTING

DRILL STEM TESTING WHAT IS A DRILL STEM TEST A TEMPORARY WELL COMPLETION TO GATHER INFORMATION ON THE POTENTIAL PRODUCTIVITY OF A FORMATION.

WHO REVIEWS THE DST PROGRAM OIM

SENIOR TOOLPUSHER

OPERATOR REP

KEY SERVICE PERSONNEL

KEY AREA’S OF REVIEW COMMUNICATION

ROLES AND RESPONSIBILITIES

EXPECTED TEST PARAMETERS • Temperature • Pressure • Hazards

EMERGENCY RESPONSE

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 vs RISK HIGH

RISK

LOW

+ KNOWLEDGE

PRE-DRILLING PHASE 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)

DRILLING A WELL Data Source

Possible Analysis

Mud Log Hydrocarbon Shows Core Samples MWD Logs

Lithology Geological Profile Depositional Environment Qualitative Hydrocarbons Pressure Regime (Qualitative) Formation Characteristics at the wellbore Fluid Contacts Near-wellbore petrophysical parameters

Degree Of Development Uncertainty = High

OPEN HOLE LOGGING Data Source

Possible Analysis

Well Logs VSP RFT Samples

Near-well formation characteristics Hydrocarbon Contacts Lithology Qualitative HC mobility Qualitative presence of hydrocarbons (HC) Confirm Seismic velocity profile Firm-up structure mapping Quantitative Pressure regime Qualitative HC PVT analysis

Degree Of Development Uncertainty = High

LIMITED INFLUX TESTING

Data Source

Possible Analysis

Transient Pressure Response Samples

Near-well formation characteristics Near-Well Productivity Index Additional qualitative PVT analysis

Degree Of Development Uncertainty = High

CONVENTIONAL WELL TESTING Data Source

Possible Analysis

Transient pressure response Pseudo Steady State Response Bulk HC Samples

Bulk reservoir properties Near-well boundaries Ideal Productivity Index Extended HC PVT Analysis Trace Element analysis (qualitative) Processing characteristics of the HC Formation Integrity (sanding tendency under high drawdown)

Degree Of Development Uncertainty = Medium

EXTENDED WELL TESTING Data Source

Possible Analysis

Steady State Pressure Response Surface Process Monitoring Chemistry

Establish Reservoir extent Pressure support mechanisms Wellsite Development Strategy Optimise Process Facility design Measure Completion Performance Calibrate design programs, etc. Stabilised trace element analysis

Degree Of Development Uncertainty = Medium / Low

TIMING 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.

TESTING OPERATION 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

DRILL STEM TEST TOOLS • 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

DST TOOLS DRILL COLLARS

SLIP JOINT, FULLY OPEN DOWNHOLE SHUT IN VALVE SLIP JOINT, 1/2 OPEN

MEMORY GAUGES

SAFETY JOINT / JAR

SLIP JOINT, CLOSED RA SUB DRILL COLLARS

PACKER

PERFORATING GUNS

SECONDARY REVERSE VALVE

DRILL COLLARS PRIMARY REVERSE VALVE

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

SUBSEA SYSTEMS • 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 TEST TREE & VALVE ASSEMBLY

LATCH ASSEMBLY

VALVE ASSEMBLY

SLICK JOINT

FLUTED HANGER TEST TREE

SURFACE TREE

COMPONENTS OF THE LANDING STRING CONTROL CONSOLE

SWIVEL

RETAINER VALVE CLOSED

HYDRAULIC HOSE REEL LANDING STRING

LUBRICATOR VALVE

SUBSEA TEST TREE UNLATCHED

HOSE PROTECTOR

RETAINER VALVE

RAMS CLOSED

SUBSEA TEST TREE LATCH ASSEMBLY

SUBSEA TEST TREE VALVES CLOSED

SUBSEA TEST TREE

SLICK JOINT

SPACER SUB FLUTED HANGER

LATCHED

UNLATCHED

WELL TEST EQUIPMENT • 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

GENERAL LAYOUT OF WELL TEST EQUIPMENT

Courtesy of Expro Group

CHOKE MANIFOLD • 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

ADJUSTABLE CHOKE TIP

DIRECTION OF FLOW

Adjustable choke

Fixed choke

HEATER

• 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

STEAM INLET

STEAM OUTLET

SAFETY VALVE

WELL FLUID INLET

CHOKE BYPASS

WELL FLUID OUTLET DRAIN

SEPARATOR

• Function – Separation of produced oil, water & gas

– Rate measurement of produced fluid – Provision of sampling points for re-combination samples

HORIZONTAL SEPARATOR

Horizontal Separators Primarily used for high liquid content wells

Courtesy of Expro Group

Vertical Separators Primarily used for high gas content wells

Courtesy of Expro Group

OIL BURNER

Courtesy of Expro Group

PREPARATION 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

TOOLS & SUB-SEA EQUIPMENT PREP

• Outline procedure ROTARY TABLE (RKB)

– – – – – – –

Layout tools Function and pressure test Drift tools Strap lengths of tools Strap lengths of tubulars Drift tubulars Prepare running “tally”

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