Defining Well Objective COPYRIGHTcloud1.activelearner.com/contentcloud/portals/...Wireline Logging...

Defining Well Objectives Core

Learning Objectives

By the end of this lesson, you will be able to:

Identify stakeholders in an effort to define well objectives

Explain how various well objectives contribute to understanding of the asset

Identify activities focused on achieving well objectives and how they may impact the well plan

Explain why well objectives change over the life of the asset

Identify commonly employed performance metrics for the drilling and completions disciplines

Defining Well Objectives Core═════════════════════════════════════════════════════════════════════════

© PetroSkills, LLC. All rights reserved._____________________________________________________________________________________________

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Goal-Plan-Execute Loop

Goal-Plan-Execute Loop

Requirements will include adherence to the company policy andregulatory framework that govern the project.

Expectations include various performance metrics such as:• Health, Safety, and Environmental (HSE) compliance

• Delivering the project per specified technical and financialparameters



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Why Drill a Well?

Geoscientists developprojects to drill wells,commonly termedprospects, based onanalysis of available data

Data from wells drilled inthe area may also be quitebeneficial

This information is used tojustify the cost of drilling aprospect well

Why Drill a Well?

Ultimately, a well isrequired to achieve twoobjectives:

• Gather informationestablishing whetherhydrocarbons actuallyexist as predicted

• If they do, determinewhether they can becost-effectivelyrecovered



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Why Drill a Well?

To confirm the presence ofhydrocarbons, theevaluation program isemployed while theprospect is being drilled

Once hydrocarbons areconfirmed, economicviability of the resource isassessed

Why Drill a Well?

When a viablehydrocarbon resource isdemonstrated to exist,data from both theevaluation and testingprograms is combined inthe development of thecompletion program thatwill be required for thelong-term productivity andmanagement of theresource



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Why Drill a Well?

In unsuccessful cases,further study may berequired before furtherprospects are sanctionedor the project may beterminated

Why Drill a Well?

To confirm the presence ofhydrocarbons, the evaluation program is employed while the prospect is being drilled

Once hydrocarbons are confirmed, economic viability of the resource is assessed

When a viable hydrocarbon resource is demonstrated to exist, data from both the evaluation and testing programs is combined inthe development of the completion program that will be required for thelong-term productivity and management of the resource

In unsuccessful cases, further study may be required before further prospects are sanctioned or the project may be terminated

Well Construction

Plan

Evaluation Program

Testing Program

Completion Program



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Changing Deliverables

Exploratory Phase

Gathering a large quantityand variety of information

The evaluation and testingprograms may consume alarge fraction of the wellconstruction budget

Several wells may befocused on ensuring a dataset that is representative ofthe entire asset

Development Phase

Evaluation and testing datacollection and analysis limitedto well-specific information

Investment must beoptimized, including thenumber, design andplacement of wells within thereservoir

Investments are chosen totarget improved recovery toextend the economic life ofthe asset



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MethodologyFormation Types & Characteristics

Formation Fluid Types & Properties

FormationPressure

Temperature

Mudlogging Yes Yes Qualitative Qualitative

Wireline Logging Yes Yes Yes Yes

LWD Logging Yes Yes Yes Yes

Coring Yes Some No No

Evaluation Program

Wireline logging offers a wider array of sensor and instrumenttypes with a higher density of sensor readings to deliver a moredetailed description of the formations

• Drilling must be halted and the drill string removed from the well to allow theuse of wireline as a sensor deployment methodology

• Requires time and introduces risk into the operation



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FormationPressure

Temperature





Evaluation Program

Collect samples of cuttings that are transported up the wellborefrom the bit and record surface sensor data

Cuttings from the formation provide valuable rock type,mineralogical, and stratigraphic information in the full geologicalcolumn including the overburden and the reservoir

Can also provide qualitative trend information on down holepressures and temperatures, but not quantitative measurements

See Mud Logging, Coring and Cased Hole Logging Operations Core for more details about mudlogging.

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FormationPressure

Temperature





Evaluation Program

Sensors deployed on LWD tools are integrated into the drill string• Real-time data is transmitted to the surface as the wellbore is being drilled

using telemetry systems

• The data quality does not match wireline systems but the timeliness of thedata adds value by allowing the drilling program to be adjusted

• If the risk of LWD tool loss is perceived to be high, the cost to the drillingoperation can be quite substantial

• LWD sensors are readily deployed into high-angle and horizontal wellbores



FormationPressure

Temperature





Evaluation Program

Wireline-conveyed sensors will not be able to reach the high-angle portions of the wellbore and are typically pipe-conveyed toreach wellbore segments, adding time and cost requirements

With both methodologies, collected data allows the determinationof formation types and characteristics, fluid types and properties,pressure and temperature



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FormationPressure

Temperature





Evaluation Program

With full rotary systems, the drill string must be removed from thewell when it is determined that a point of interest in the formationhas been reached

The conventional drill string is removed from the well and aspecialized core barrel and core bit are attached to the bottom;these tools are run back into the well



FormationPressure

Temperature





Evaluation Program

As the wellbore is deepened, a 3” to 4” diameter sample offormation, perhaps 30-300 feet [10-100 meters] long, is capturedinside the core barrel

Sidewall coring activities are performed after the well has beendrilled and tools are usually wireline-deployed

Multiple small rock samples can be obtained by either percussionsamplers or rotary sidewall samplers



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Hollow percussion samplers are explosively fired into theformation at high velocity and then retrieved on retention cablesas the tool is pulled uphole on wireline

Rotary sidewall systems are also deployed on wireline

Sidewall coring operations are typically less costly than full rotarycoring operations but the smaller rock sample size allows morelimited analysis than the larger rotary-drilled cores



FormationPressure

Temperature





Evaluation Program

See Core Analysis Core Knowledge for information about coring system types.

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Testing Program

Productivity can be assessed with a testing program

In most cases, casing will be run and cemented across the targetinterval to ensure a stable wellbore environment for the test

A specialized string of testing tools will be run into the well,usually including perforating guns, various flow control valves,sensor packages, a testing packer and a running string of tubingor drill pipe

With guns at the correct depth, the packer is set to isolate theannulus to the surface

Fluids of differing density may be circulated above the packer toprovide tubing pressure less than reservoir pressure, commonlycalled an ‘underbalanced’ condition

Testing Program

The perforating guns are fired, exposing the reservoir to thelower pressure in the wellbore, and the formation fluids flow intothe wellbore and up the tubing

Produced fluid flows through a surface choke manifold and thena separator to remove gas from liquid

Gas is flared as it is produced while oil may be stored or flared

Samples of produced fluid are captured on a regular basis

Upon test completion, the tool string is recovered from the well

The reservoir pressure response to flow and shut-in periodsgives a good indication of the size of the reservoir and thepotential recoverable reserves



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Testing Program

In the success case, it provides guidance to drilling andcompletion disciplines toward planning for future wells as well asthe facilities disciplines in designing production systems tohandle the expected pressures, flow rates, and fluid types

In some cases, testing may not be required• The future of the asset may be decided based on data obtained

from logging

• This would especially be the case in the development phase of anasset

• Sufficient information has already been learned in previous wells ofvery similar character and the risk and expense of a testingprogram may comfortably be omitted from the well plan



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Completion Program

Data collection and analysis from the Evaluation and TestingPrograms provides detailed information for the Completiondesign effort

This will involve decisions related to the style of the completionand down hole and surface flow and pressure control systems

The initial Completion design will likely be modified to provideoptimum production conditions and enhanced reliability

Completions are designed to meet well requirements related toflowing gas and liquid rates, pressure, contaminants that may bepresent, the stability of the producing formation, and otherfactors

Completion Program

The reservoir section can be left open hole, gravel-packed withscreens, or cased and cemented

The reservoir may be productive in an unstimulated state or itmay require a stimulation treatment to produce economic rates

The reservoir may flow naturally to surface or it may require anartificial lift system at some point in its life

The design of the completion and the well drilled to house thecompletion must consider these factors and be prepared to cost-effectively adjust as reservoir conditions change over time

The completion phase of well operations involve major changesto down hole tools and tubulars, surface equipment and fluidsystems from the drilling phase



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Completion Program

The time and cost to transition the rig from drilling mode tocompletion mode can be substantial and should be consideredwhen planning these job sequences

In situations where the rig is capable of managing these changesquickly and efficiently and the transition cost is therefore lowcompared to the well cost, it may be decided to complete eachwell as they are drilled

While this involves more transition cost, it has the advantage ofallowing earlier production from the asset; also, rigs that arecapable of quick and efficient transitions are normally moreexpensive than less capable rigs

Completion Program

Drill-Complete-Drill-Complete Mode

Batch Drill-Batch Complete Mode



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Well Planning

Well Planning

Construct a wellbore to:• Gather Required Data

• Accommodate the Completion

• Enable Alternate Future Wellbore Utilization

• Maintain Wellbore Integrity Over the Life of the Well

Mitigate HSE issues

Accurately Predict Time and Cost



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Performance Metrics

Key Performance Indicators (KPIs)• HSE

• Time

• Cost

• ∆Time vs. Authorization for Expenditure (AFE)

• ∆Cost vs. AFE

• Technical – e.g., hit targets, casing size at reservoir

• Non-Productive Time (NPT)

Learning

Learning Objectives

You are now able to:

Identify stakeholders in an effort to define well objectives

Explain how various well objectives contribute to understanding of the asset

Identify activities focused on achieving well objectives and how they may impact the well plan

Explain why well objectives change over the life of the asset

Identify commonly employed performance metrics for the drilling and completions disciplines



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