DST and Well Testing

8/22/2019 DST and Well Testing

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Well Testing

Overview of the Equipment and Well Test Analysis

Copyright 2007, , All rights reserved

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Why Test Wells?

What kind of well do I have?

Is the well productive?

What are the flow

characteristics of this well?


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Information from Well Tests

Reservoir information

Extents and structure

Permeability and skin


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Samples for PVT analysis

Production estimation


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Equipment required for Well Tests

Downhole tools used to isolate and control the reservoir - a

temporary completion of the well

Surface equipment designed to control pressure, separate


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Gauges and meters used to record pressure, temperature

and rates

Efficient disposal of well effluents

(10,000 bbls/oil/day burnt equivalent to 67 Megawatt of

energy - medium size Nuclear Powerstation)


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Well Test Applications

Exploration

reservoir size, hydrocarbon volume, hydrocarbon type, productivity (is this zone economic?, how large is the reservoir?)

Reservoir Development


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pressure, permea y, connec v y, pro uc v y, orma on amage,drive mechanism

(what is the reservoir pressure?, how can we estimate reserves?, forecastfuture performance, optimize production)

Reservoir Management pressure, permeability, drainage, sweep efficiency, formation damage

(is the well damaged?, stimulation treatment efficiency, why is the well notperforming as expected?)


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Testing and reservoir development

Testing informs the state of the reservoir at the time of the

test.

In case of unexpected production, testing helps the


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,

and prodution optimization.

On mature reservoirs, testing information may steer to

strategical decisions and the revision of recoverable

reserves.


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Types of Well Tests

Single-well tests

Drawdown (producing a well at constantrate beginning at time zero and measuringthe resulting pressure response)

Buildup (shutting a well that has been

Multi-well tests

Interference tests (producing onewell at constant rate beginning at

time zero and measuring the

resulting pressure rresponse at one


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pressure response) Injection (Similar to a drawdown test.

Conducted by injecting fluid into a well atconstant rate beginning at time zero and

measuring the resulting pressureresponse)

Injection-falloff (Similar to a buildup test.Conducted by shutting in an injection welland measuring the resulting pressure

response)

or more o se we s

Pulse tests (alternately producing

and shutting in (pulsing) one well

beginning at time zero and

measuring the resulting pressure

response at one or more offset wells)


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What is a Well Test?

A test conducted by

Changing production rate at a well

Measuring resulting pressure response at the same well or


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IIII SSSS OOOOI : reservoir fluid withdrawalS : well and reservoir systems

O : change in reservoir pressure


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Introduction

Well Testing is a technique that examines a significant portion of the

reservoir underd namic conditions to determine its roduction


capabilities & reservoir properties.

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Well Test Analysis

Input Information

Production rate (Q) Well head pressure (Pwh)

Bottom hole pressure (P)

Gauge depth Datum depth

Formation thickness (h)


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r

Output Information

Productivity Index (PI)

Static gradient of fluid

Permeability and skin

Drainage radius

Sample of fluids

Efficient of stimulation

Dual permeability / porosity

phenomena


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Testing and reservoir development

Testing informs the state of the reservoir at the time of the

test.

In case of unexpected production, testing helps the


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,

and prodution optimization.

On mature reservoirs, testing information may steer to

strategical decisions and the revision of recoverable

reserves.


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Well Test Methods/Techniques

Surface Well Test (SWT)

Drill Stem Test (DST)

Pressure Survey (P/T

PLT

real-time

memory


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real-time

memory

MRCD/CH RFT

Permanent Sensors

Echometer


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Types of Well Tests

Single-well tests

Drawdown (producing a well at constantrate beginning at time zero and measuringthe resulting pressure response)

Buildup (shutting a well that has been

Multi-well tests

Interference tests (producing onewell at constant rate beginning at

time zero and measuring the

resulting pressure rresponse at one


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pressure response) Injection (Similar to a drawdown test.

Conducted by injecting fluid into a well atconstant rate beginning at time zero andmeasuring the resulting pressureresponse)

Injection-falloff (Similar to a buildup test.Conducted by shutting in an injection welland measuring the resulting pressure

response)

or more o se we s

Pulse tests (alternately producing

and shutting in (pulsing) one well

beginning at time zero and

measuring the resulting pressure

response at one or more offset wells)


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Reserves Definition

Reserves

Estimated quantity of oil and natural gas related substances

anticipated to be recovered from known accumulations, from a

given date forward, by known technology under specific


reasonable outlook for the future

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Reserves: Definition

Proved Reserves

These are the remaining reserves that can be estimated with

a high degree of certainty, which for purpose of reserves

classification means that there is generally 80% or greater


.

The reserves may be divided into proved developed and

proved undeveloped to identify the status of development

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Proved Reserves

The reserves are considered proved based on the following

criteria

Production and formation tests

Well Logs/ Core analysis


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Probable Reserves

These are the remaining reserves that are less certain to berecovered than proved reserves, which for purpose of

reserves classification means that there is generally 40-80%


.

Both the estimated quantity and the risk weighted portion

reflecting the respective probability should be reported.

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Possible Reserves

These are the remaining reserves that are less certain to be

recovered than probable reserves, which for purpose of

reserves classification means that there is generally 10-40%


.

Both the estimated quantity and the risk weighted portion

reflecting the respective probability should be reported.

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What Is A Well Test?

A tool for reservoir evaluation and characterization

Investigates a much larger volume of the reservoir than cores

or logs

Provides estimate of permeability under in-situ conditions

-


Provides estimates of distances to boundaries

Provides estimates of well deliverability

Allows capture of sample for PVT analysis

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Well Test Objectives

Exploration

Estimate Distances to Reservoir Boundaries

Estimate Reservoir Pore Volume Estimate Initial Reservoir Pressure

Estimate Well Deliverability


Appraisal Measurements of the oil production rate

Estimate Skin Factor

Collection of the fluid samples Evaluation of the formation characteristics

Influence of boundary conditions

Determination of the initial reservoir pressure 20


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Well Test Objectives

Development Estimate Skin Factor

Measurement of the average reservoir pressure within the drainagearea of the well

Estimate the formation properties


Production Estimate Skin Factor Diagnose Productivity Problems

Estimate Permeability to Aid in Fracture Treatment Design

Evaluate Stimulation Treatment Effectiveness

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Types of Well Test

Single well tests

Oil WellDrawdown test- Produce a

well at constant rate and


measure the pressureresponse.

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Types of Well Test

Buildup test Shut in a well

that has been producing andmeasure the pressure

response.


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Types of Well Test

Injection test Inject fluid

into a well at constant rateand measure the pressure

response.


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Types of Well Test

Single well tests

Gas WellIsochronal Test A series ofdrawdown and buildup

pwf1 pwf2wf3

pwf1 pwf2wf3


sequences a erendrawdown flow rates, with eachdrawdown of the same durationand each buildup reachingstabilization at the samepressure as at the start of thetest..

Q1 Q2 Q3 Q4

t t tt

pwf4

Q1 Q2 Q3 Q4

t t tt

pwf4

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Types of Well Test

Modified Isochronal

TestA series of drawdown

and buildup sequences

Pwf2

Pwf1

Pwf

3Pwf


a eren raw own

flow rates, with each

drawdown and buildup

of the same duration.

Q

1Q

2

Q3 Q

4

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Types of Well Test

Flow After Flow test A

series of drawdown


,

more, followed by a build up.

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Types of Well Test

Multi-well tests

Interference test Produce one well at constant rate andmeasure the pressure response at one or more offset wells.


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Well and Reservoir Parameters

rivative,

psi

Near Wellbore Damage

Wellbore Storage

Permeability Boundary Type


Elapsed time, hrs

Early-time

region

Middle-

timeregion

Late-time

regionPressure

change,

de

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Flow-Regimes and Reservoir Features

Near wellboreNear wellboreNear wellboreNear wellbore

(early time)(early time)(early time)(early time)

Reservoir behaviorReservoir behaviorReservoir behaviorReservoir behavior

(middle time)(middle time)(middle time)(middle time)

BoundariesBoundariesBoundariesBoundaries

(late time)(late time)(late time)(late time)

Wellbore storage (PSS) Homogeneous (rad) Single fault (hemi-rad)

-conductivity fracture

(lin)Double porosity Leaky fault (2 rad)


Low cond fracture (bi-lin) Double permeability (2 rad) Constant pressure

Limited entry (sph) Composite (2 rad) Channel (lin)

Horizontal well (sph or lin) Layered reservoir Wedge (pseudo-rad)

Skin Closed reservoir (PSS)

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Why are Flow-Regimes Useful?

Flow regimes, when recognized, can help the interpreter recognize

what the reservoir looks like, i.e. what is the model

Depending on their succession and time of occurrence, it is possible tobuild a reservoir model with 3 distinct components:

Near-wellbore model


Formation behavior Boundaries

The key: flow-regimes show simple mathematical relationship between

pressure and time

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Near Wellbore Damage (Skin)

Mud filtrateinvasionMud filtrateinvasion

p < pb p > pbp < pb p > pb

1500

2000

re,psi 1500

2000

re,psi


Skin due to Invasion Skin due to Production

h

hp

Skin due to Flow Regime Skin due to Partial Penetration

500

1000

1 10 100 1000 10000

Distance from center of wellbore, ft

Press

ps

500

1000

1 10 100 1000 10000

Distance from center of wellbore, ft

Press

ps

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Reservoir Parameters

1000

1100

1200

1300

ssure,psi

Initial Pressure

Permeability

(from slope)


600

700

800

900

110100100010000100000100000010000000

Adjusted Horner Time Ratio

Adjusted

Pre

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Boundaries


Parallel Faults, Channels

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P d ti it


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Productivity

Oil

Inflow Performance Relationship (IPR)

Gas

Absolute Open Flow Potential (AOFP)


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D i Phil h


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Design Philosophy

Test design optimization

Test objectives Reservoir parameters (basis

of design)

Productivity analysis

Range of expected ratesand drawdown values

PIPESIM* 2007


es es gn cr er a an

limitations

Test sequence and duration

(pressure transient

simulation)

ECLIPSE* 100software

WELLTEST* 200

software

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Basic Data


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Basic Data

Fluid data

Average reservoir pressure

Average reservoir temperature

Bubble point/dew point pressure

Gas composition or specific gravity with co2 and h2s contents

Gas properties compresibilty,viscosity,formation volume factor and z factor


Water properties compresibilty,viscosity,formation volume factor and water

salinity Oil properties compresibilty,viscosity,formation volume factor

CGR,GOR or solution gas liquid ratio

Total compressibility

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T ti H d


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Testing Hardware

DST

Tools Gauges


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Equipment

Gauges


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DST Equipment


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DST Equipment

Isolate the target zone.

Perforate. Control well flow.

Conve fluid to surface.


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Acquire downhole data

Spot stimulation fluids

Well kill

Avoid swabbing

DST packers


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Isolate the target zoneDST packers

Packers

Production Permanent, run separate

HPHT


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Floating seal assy

Cost

Test

Retrievable, run on DST string

Set by string manipulation + weight

Needs slip joints for string

expansion

Slip Joint


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Slip-Joint

Allow for string contraction and

expansion during testing Internally balanced


2-4 normally run on a DST

Drill collars run below for adding

weight on the Packer

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TCP Guns


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TCP Guns

Tubing-Conveyed Perforating (TCP)

Advantages: large guns fired underbalanced withwell-control equipment in place


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long intervals efficiently perforated variety of firing systems

ability to drop guns allowing futurethrough tubing operations

Well Control Flow


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Well Control Flow

Test and Control Valves

Ball Tester valve - multi use Combined Test and Circulating

valves


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u ng es er va ve

Flapper or ball type- One shot

Safety Valves

Flapper or ball type - one shot

Circulating valves

Sliding sleeve

One shot and multi cycle+

-

+

-

+

-

Data Capture


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Data Capture

Datalatch

Allow real time monitoring WL running tool inside Tubing

DGA gauge carrier


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Memory gagues

LINC

Power latch system

Bottomhole Sample carrier


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Bottomhole Sample carrier

Sampling carrier to be run

in the DST string Samplers activated by


Up to 10 samplers in eachcarrier

PVT samples under

reservoir conditions

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Surface Well Test Equipment


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Surface Well Test Equipment

Control pressure and

flow

Separate the well

effluent


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Meter and record

rates, pressures and

temperatures.

Provide sampling

ports.

Storage or disposal of

well effluents.

Control Pressure and Flow


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Flowhead

controls pressure and flow allows movement of the test

string


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supports the weight of the teststring

allows tools to be introduced

into the well



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Choke Manifold

contols wellhead pressure controls flow rate

critical flow


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sand and water production

Control Pressure and Flow, Separator


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Control Pressure and Flow, Separator

Steam Exchanger

equipped with choke raises the temperature of the

well effluent


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prevents hydrate formation reduces fluid viscosity

breaks down emulsions before

the well effluent enters theseparator

requires separate boiler

Test Separator


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est Sepa ato

CAPACITIES AND RETENTION

TIME LEVEL CONTROL

OIL METERING


GAS METERING SAFETY FEATURE

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Separator features


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p


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Separator Measurements


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p


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VX t


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Detector

Venturi

VX meter


Flow

Composition

Meter

T

P

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Surge tank


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g

Calibration tank

Used to calibrate flow meters inSeparator

Allows all gas to be bleed off


Can be used to collectinterfaces

Used for low flow rates

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Recorder


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Surface Testing

Acquisition Network

sensors and meters

used to acquire:


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pressure

temperature

flowrates

oil

water

gas

Disposal


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Burners and Booms

efficiently dispose of the oilproduced at the surface

during an offshore well test


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reduces storage and

pollution problems

to limit the heat radiation on

rigs, the burners are

attached to booms to keepthem at a safe distance from

the rig

SUBSURFACE SAFETY TOOLS


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SUBSURFACE SAFETY TOOLS

Fixed rigs Floaters rigs


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SAFETY SYSTEMS

COMPULSORY

ON ALL FLOATERS

:


SENTREESENTREESENTREESENTREE

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Subsea BOP stack


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Subsea O stac

Subsea test tree

Safety valve, ball andFlapper

Fail safe closed


Shear ram can be closed Retainer valve can be run

above to trap string

contence

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SenTREE 3 - Basic Tool Features


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SenTREE 3 Basic Tool Features

Reduced length and modularity (compared with

old generation: EZ-Tree)

Can unlatch under full tension

Unlatch at an angle up to 6 deg

1.5-in. coil tubing cutting capability


Chemical injection pointHydraulically or Mechanically UNLATCH

Connections: 3 ID & 5 ACME BOX x BOX

Other version: SenTree 7 (ID= 7)

15 Kpsi WP

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RETAINER VALVE


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Fail safe closed

Works (close/open) in conjunction

with the Sentree Prevents pollution

Cuts wireline fail safe


u s co u ng w pressure ass s

closure Integrated Bleed Off Valve (BOV), for

between Retainer and Sentree.

Chemical injection point

Connections: 3 ID & 5 ACME5 ACME5 ACME5 ACME

BOX x BOXBOX x BOXBOX x BOXBOX x BOX

15 Kpsi WP

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DST and Well Testing

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