well completion planning

7/28/2019 well completion planning

1/13

WELL COMPLETION PLANNING

ContentsContents Page Page

Introduction .................................................. 1Completion Planning Process ...................... 1

Reservoir Parameters .................................. 5Produced Fluid Characteristics .................... 6

Wellbore Construction.................................. 7Completion Assembly and Installation ......... 8Initiating Production ..................................... 9

Stimulation ................................................... 10

Well Service and Maintenance ....................11

Logistic, Location and Environment ............. 12Client Stock, Convention or Preference ....... 12

Regulatory Requirements ............................ 12Revenue and Cost ....................................... 13

Economic .....................................................13Company Objectives .................................... 13

CONFIDENTIALITY

This manual section is a confidential document which must not be copied in whole or in part ordiscussed with anyone outside the Schlumberger organisation.

Although many wells (and fields) may be similar, the

success of each completion system should be closelybased on the individual requirements of each well. There-fore, generic design or installation procedures should be

carefully reviewed and amended as required.

The flow chart shown in Fig. 1 (principal phases summa-

rized in Fig. 3) reflects the general sequence in whichcompletion design and installation factors are typicallystudied. The "hook point" is provided as a reference pointto which specific procedures, detailed later in this manual,

will connect.

The economic impact of designing and installing non-optimized completions can be significant. Consequently

the importance of completing a thorough design andengineering process must be stressed. Delaying the com-mencement of the wells payout period is one example of

how non-optimized completion design, or performance,can effect the achievement of objectives. However, while

reducing installation cost and expediting start-up areimportant objectives, further reaching objectives, such as

long-term profitability must not be ignored (Fig. 2). As isillustrated, a more complex and costly completion mayprovide a greater return over a longer period. In addition,

the consequences of inappropriate design can have asignificant effect, e.g., requiring premature installation of

velocity string or artificial lift.

Introduction

Planning a completion, from concept through to installa-

tion, is a complex process comprising several distinctphases. Many factors must be considered, although in

most cases, a high proportion can be quickly resolved ordisregarded. Regardless of the complexity of the comple-

tion design, the basic requirements of any completionmust be kept in mind throughout this process, i.e., acompletion system must provide a means of oil or gas

production (or injection) which is safe, efficient and eco-nomic.

Ultimately, it is the predicted technical efficiency of a

completion system, viewed alongside the company objec-tives which will determine the configuration and compo-nents to be used.

Completion Planning Process

This section outlines the principal factors which should be

considered when planning an oil or gas well completion.

In addition to the technical influences on completiondesign and selection, economic and nontechnical issues

are also detailed. The relevance of these issues, incommon with technical details, is dependent on the cir-

cumstances pertaining to the specific well, completion orfield being studied.


2/13

CONFIDENTIALITY


Component

Installation

Onsite

Preparation

Pre-installation Well Service Work Perform required treatments Drift run (minimum/essential)Surface/Production Equipment Preparation and checking

Budgetary Analyses Actual vs. plannedSafety and Environmental Factors

Precaution and contingency planning

Completion

Evaluation

Monitor Production Parameters Actual vs. ForecastEvaluate Production Response Actual vs. Forecast

Final Budgetary Analyses Actual vs. Forecast

Establish the objectives

and design basis

Essential Basics Safe Efficient EconomicLogistic and Location Surface and field facilities Location and wellsite constraints

Corporate Policy Medium and long-term objectives Contractual requirements/obligations

Determine the optimum

well performance

Reservoir Parameters Boundaries Structure Production mechanism Dimensions Rock Properties Rock compositionReservoir Fluid Characteristics Physical properties Chemical propertiesModelling and analyses NODAL analyses Perforation analyses Others

Budgetary Considerations Investment incentives Revenue(s) TaxationLegislative and Regulatory Safety and environmental factorsProduction Constraints Downstream capacity Flexibility of production Production profile Recoverability

Establish conceptualcompletion designs

Wellbore Construction Drilling phase considerations Evaluation phase considerations Pre-completion stimulationWorkover Philosophy Routine well service requirements Workover activitiesMaterial Selection Forces on completion components Wellbore environment constraintsReview Alternative Completions Compile list of alternatives/options Confirm preferred completion type

Budgetary Analyses Review outline completion costs

Starting

"philosophy

statement"

Finishing"philosophy

statement"

Cleanliness standards Completion components Completion fluidsDimensional checks Components String* Space-outEquipment handling Complex components Thread make-upProceedures Assembly installation Pressure testing Space-out)

Budgetary Analyses Actual vs. plannedSafety and Environmental Factors

Precaution and contingency planningRig time and well downtime Efficient completion

Fig. 1a. Phases of well completion planning and installation.

Flowchart Key

Technical requirementsconsiderations and issues

Non-technical andcommercial issues


3/13

Procure components

and services

Issue Bid Request or Enquiry Technical specifications Scope of workBid Evaluation Design proposal Hardware selection Technical support

Associated services Innovative packaging (?)Recommendation Technical merit Integrated servicesVendors Meeting Confirm specifications/selection Review/revise the scope of workQuality Assurance/Control Inspection and verification Controls and checks

Issue Bid Request or Enquiry Contractual non-technical contentBid Evaluation (Commercial)

Price/cost Incentives/penalties Innovative packagingRecommendation AdministrativeVendors Meeting Establish contacts/form work group Issue formal orderQuality Assurance/Control Non-technical controls and checks

Planning of associated

service activities

Existing Completion Tubulars Partial or complete removal Preparation for concentric completionSelect Treatments Determined by specific conditionsPrepare Procedures Determined by application/conditions

Budgetary Analyses Return on Investment

Offsite

Preparation

Quality Assurance & Control Component Inspection Conformance to specified standardsPrepare Installation Procedure(s) Assembly Installation Testing Contingency PlansOffsite Assembly Check and test key components

Confirm Project Timing Lead times Operational windows

Quality Assurance & Control Delivery time compliance Quality documentation package/file

Review strategy for

well and field life

Production Strategy (Well/Field) Well performance Field performance Completion requirements

Local (Management) or Field Policy Medium- to long-term objectives Contractual requirementsImplications of Multiple Well Project Effect on cost Operational conflict Production conflict

Develop detailed

completion design

Specific Procedures

Velocity string

Gas lift installation

ESP installation

Completion Configuration Wellbore tubulars Wellbore and perforations Near wellbore matrix Hydraulic fracturingProduction Initiation Inducing flow Clean-up programCompletion Fluids Required density Chemical composition Additives Compatibility DisposalWell Service and Workover Completion function(s) Light service units (wireline & CT) Heavy service (snubbing and w/o rig)Surface Support Facilities Utilities Downstream facilitiesModelling and Analyses NODAL analyses OthersPerforating SPAN* analyses Charge and gun selection

Client Convention and Preference Existing stock Contractual obligations Corporate or local policies Familiarity and acceptanceDetailed Budget Capital cost Installation cost Operating cost Maintenance cost (routine) Major servicing cost (periodic)Establish Project Time Scale Component availability Lead time(s) Operational windows Simultaneous operations (offshore)

HOO

KPO

INTFOR S

PECIFICPROCEDU

RES


4/13

CONFIDENTIALITY


ESTABLISH THE OBJECTIVES

AND DESIGN BASIS

DETERMINE THE OPTIMUM

WELL PERFORMANCE

ESTABLISH CONCEPTUALCOMPLETION DESIGNS

REVIEW STRATEGY FOR LIFEOF THE WELL AND FIELD

DEVELOP DETAILEDCOMPLETION DESIGN

PROCUREMENT OF

COMPONENTS AND SERVICES

PLANNING OF ASSOCIATED

WELL SERVICE ACTIVITIES

OFFSITE PREPARATION

ONSITE PREPARATION

INSTALLATION

EVALUATION

Fig. 2. Consequences of a non-optimized completion system.

Fig. 3. Principal phases of well completion.

Drilling, DST, completion

logging and stimulation

Optimized

productionNon-optimized

production

Time (Life of the well)

Expenditure/Revenue

+$

-$

EnhancedRecovery

Stimulation

Thru-tubing

W/O

Profile

Modification

P & A


5/13

CONFIDENTIALITY


Reservoir Boundaries

Structural trapsStaratographic traps

UnconformitiesPermeability contrasts

Reservoir Structure

Continuity

Permeability barriersIsotropy

RESERVOIR PARAMETERS

Production Mechanism

Water drive

Solution gasGas cap

CombinationInjectionArtificial

Physical Parameters

SizeShape

HeightPressure

Temperature

Rock Properties

PorosityPermeability

Pore size distribution

Fluid saturationGrain size and shape

Wettability

Rock Composition

CompositionConsolidationContaminationClay content

Moveable finesCementaceous material

Scale forming materials

Fig. 4. Reservoir parameters.

Reservoir Parameters

The type of data outlined in this category are obtained byformation and reservoir evaluation programs such as

coring, testing and logging. Typically, such data will beintegrated by reservoir engineers to compose a reservoir

model.

The reservoir structure, continuity and production drive

mechanism are fundamental to the production process ofany well. Frequently, assumptions are made of these

factors which later prove to be significant constraints onthe performance of the completion system selected.


6/13

CONFIDENTIALITY


Physical Properties

Oil densityGas gravity

ViscosityPour point

Gas-oil ratio

Water-oil ratio

Chemical Properties

Composition

Wax contentAsphaltenes

Corrosive agentsToxic components

Scale

PRODUCED FLUID CHARACTERISTICS

Fig. 5. Produced fluid characteristics.

Physical characteristics of the reservoir are generally

more easily measured or assessed. Pressure and tem-perature are the two parameters most frequently used in

describing reservoir and downhole conditions. The effectsof temperature and pressure on many other factors can besignificant. For example, corrosion rates, selection of

elastomer or seal materials and the properties of pro-duced fluids are all effected by changing temperature and

pressure.

When investigating the reservoir rock characteristics, the

principal concern is assessing formation behavior andreaction. This includes behavior and reaction to the drill-

ing, production or stimulation treatments which may berequired to fully exploit the potential of the reservoir.

The formation structure and stability should be closely

investigated to determine any requirement for stimulationor sand control treatment as part of the completion pro-cess.

The reservoir characteristics effecting completion con-

figuration or component selection are best summarizedby reviewing the reservoir structure, continuity, drive

mechanism and physical characteristics. These shouldbe reviewed alongside the physical and chemical proper-ties of the formation (Fig. 4).

Produced Fluid Characteristics

Two conditions, relating to the chemical properties of the

produced fluid most effect the physical qualities of comple-

tion components and materials. These are chemical depo-

sition (scale, asphaltenes etc.) and chemical corrosion(weight loss and material degradation). Both conditions

still account for significant losses in production and deg-radation of equipment in many fields.

The ability of the reservoir fluid to flow through the comple-tion tubulars and equipment, including the wellhead and

surface production facilities, must be assessed. For ex-ample, as the temperature and pressure of the fluid

changes, the viscosity may rise or wax may be deposited.

Both conditions may place unacceptable back-pressure,thereby dramatically reducing the efficiency of the comple-

tion system.

While the downhole conditions contributing to these fac-tors may occur over the lifetime of the well, consideration

must be made at the time the completion components arebeing selected. Cost effective completion designs gener-ally utilize the minimum acceptable components of an

appropriate material. In many cases, reservoir anddownhole conditions will change during the period of

production. The resulting possibility of rendering thecompletion design or material unsuitable should be con-

sidered during the selection process.

The production fluid characteristics effecting completion

configuration or component selection are best summa-rized by reviewing the physical and chemical properties of

the fluid (Fig. 5).


7/13

CONFIDENTIALITY


Wellbore Construction

Wellbore construction factors can be categorized in the

following phases.

Drilling The processes required to efficiently drill to,and through the reservoir.

Coring and testing The acquisition of wellbore survey

and reservoir test data used to identify completiondesign constraints.

Pre-completion stimulation or treatment Final prepa-ration of the wellbore through the zone of interest for the

completion installation phase.

It is an obvious requirement that the drilling program mustbe designed and completed within the scope and limitsdetermined by the completion design criteria.

Most obvious are the dimensional requirements deter-

mined by the selected completion tubulars and compo-nents. For example, if a multiple string completion is to be

selected, an adequate size of production casing (andconsequently hole size) must be installed. Similarly, thewellbore deviation or profile can have a significant impact.

Drilling and associated operations, e.g., cementing, per-formed in the pay zone must be completed with extra

vigilance. It is becoming increasingly accepted that the

prevention of formation damage is easier, and much morecost effective, than the cure. Fluids used to drill, cement or

service the pay zone should be closely scrutinized andselected to minimize the likelihood of formation damage.

Similarly, the acquisition of accurate data relating to the

pay zone is important. The basis of several major deci-sions concerning the technical feasibility and economicviability of possible completion systems will rest on the

data obtained at this time.

A pre-completion stimulation treatment is frequently con-ducted. This is often part of the evaluation process in a

test-treat-test program in which the response of the reser-voir formation to a stimulation treatment can be assessed.

The wellbore characteristics affecting completion con-figuration or component selection are best summarized

by reviewing the drilling, evaluation and pre-completionactivities (Fig. 6).

Fig. 6. Wellbore construction

Drilling

Hole size

DepthDeviation

Well path

Formation damage

Pre-completion

Casing schedules

Primary cementingPre-completion stimulation

WELLBORE CONSTRUCTION

Evaluation

LoggingCoring

TestingFluid sampling


8/13

CONFIDENTIALITY


Completion Assembly and Installation

This stages marks the beginning of what is commonly

perceived as the completion program. It is the intent ofthis manual to enlighten readers as to the true and

necessary extent of the completion program. As hasbeen demonstrated, considerable preparation, evalua-

tion and design work has been completed before thecompletion tubulars and components are selected.

With all design data gathered and verified, the completioncomponent selection, assembly and installation process

commences. This phase carries obvious importance sincethe overall efficiency of the completion system depends

on proper selection and installation of components.

A visionary approach is necessary since the influence ofall factors must be considered at this stage, i.e., factorsresulting from previous operations or events, plus an

allowance, or contingency, for factors which are likely orliable to effect the completion system performance in the

future.

The correct assembly and installation of components inthe wellbore is as critical as the selection process by whichthey are chosen.

This is typically a time at which many people and re-sources are brought together to perform the operation.

Consequently, the demands brought by high, and mount-

ing daily charges imposes a sense of urgency whichrequires the operation be completed without delay.

To ensure the operation proceeds as planned, it is essen-

tial that detailed procedures are prepared for each stageof the completion assembly and installation. The com-

plexity and detail of the procedure is largely dependent onthe complexity of the completion.

In general, completion components are broadly catego-rized as follows.

Primary completion components

Ancillary completion components

Primary completion components are considered essen-tial for the completion to function safely as designed. Such

components include the wellhead, tubing string, safetyvalves and packers. In special applications, e.g., artificial

lift, the components necessary to enable the completionsystem to function as designed will normally be consid-ered primary components.

Fig. 7. Completion assembly and installation.

Primary Components

Wellhead

Xmas treeTubing

Packer

Safety valve

Ancillary Components

Circulating devices

NipplesFlow couplings

Injection mandrels

Tubing seal assembly

COMPLETION ASSEMBLY AND INSTALLATION

Completion Fluids

Completion fluidPacker fluid

Perforating fluidKick-off fluid


9/13

CONFIDENTIALITY


Ancillary completion components enable a higher level ofcontrol or flexibility for the completion system. For ex-

ample, the installation of nipples and flow control devices

can allow improved control.

Several types of device, with varying degrees of impor-tance, can be installed to permit greater flexibility of the

completion. While this is generally viewed as beneficial, acomplex completion will often be more vulnerable to

problems or failure, e.g., due to leakage.

The desire for flexibility in a completion system stems from

the changing conditions over the lifetime of a well, field orreservoir. For example, as the reservoir pressure de-

pletes, gas injection via a side-pocket mandrel may benecessary to maintain optimized production levels.

A significant fluid sales and service industry has evolvedaround the provision of completion fluids. Completion

fluids often require special mixing and handling proce-dures, since (i) the level quality control exercised on

density and cleanliness is high, and (ii) completion fluidsare often formulated with dangerous brines and inhibitors.

The ultimate selection of completion components andfluids should generally be made to provide a balance

between flexibility and simplicity.

The completion component selection factors are bestsummarized by reviewing the primary and ancillary com-

ponents, and installation procedures (Fig. 7).

Initiating Production

The three stages associated with this phase of the comple-

tion process include (Fig. 8 and 9).

Kick-off

Clean up

Stimulation

The process of initiating flow and establishing communi-

cation between the reservoir and the wellbore is obviouslyclosely associated with perforating operations. If the well

is to be perforated overbalanced, then the flow initiationand clean up program may be dealt with in separate

procedures. However, if the well is perforated in anunderbalanced condition, the flow initiation and clean upprocedures must commence immediately upon perfora-

tion.

The benefits of underbalanced perforating are well docu-mented and the procedure is now conducted on a routine

basis. While the reservoir/wellbore pressure differentialmay be sufficient to provide an underbalance at time ofperforation, the reservoir pressure may be insufficient to

cause the well to flow after the pressure has equalized.

Adequate reservoir pressure must exist to displace thefluids from within the production tubing if the well is to flow

unaided. Should the reservoir pressure be insufficient toachieve this, measures must be taken to lighten the fluid

Clean-up Program

Initial flowrate andrate of increase

Evaluation program

Testtreattest

PRODUCTION INITIATION

Inducing Flow

Gas liftNitrogen kick-off

Light-fluid circulationUsing completion components

or coiled tubing

Fig. 8. Production initiation.


10/13

CONFIDENTIALITY


Near Wellbore and Reservoir Matrix

Matrix acidizing

Hydraulic fracturingNon-acid treatments

STIMULATION

Wellbore and Perforations

Wellbore clean-upPerforating acid

Perforation wash

Fig. 9. Stimulation

column - typically by gas lifting or circulating less dense

fluid. The preparations for these eventualities are part ofthe completion design process.

The flowrates and pressures used to exercise controlduring the clean up period are intended to maximize the

return of drilling or completion fluids and debris. Thiscontrolled backflush of perforating debris or filtrate also

enables surface production facilities to reach stable con-ditions gradually.

In some completion designs, an initial stimulation treat-ment may be conducted at this stage. An acid wash or

soak placed over the perforations has proved effective in

some conditions. However, as underbalanced perforatingbecomes more popular, the need and opportunity for thistype of treatment has diminished.

Stimulation

There are four general categories of stimulation treatmentwhich may be considered necessary during the process of

completing a well.

Wellbore cleanup

Perforation washing or opening

Matrix treatment of the near wellbore area

Hydraulic fracturing

Wellbore clean up will not normally be required with newcompletions. However, in wells which are to be reperforated

or in which a new pay zone is to be opened, a well bore

clean up treatment may be appropriate. There are a range

of perforation treatments which may be associated withnew or recompletion operations.

Perforating acids and treatment fluids are designed to be

placed across the interval to be perforated before the gunsare fired. Used in overbalanced perforating applications,

the perforating acid or fluid reduces the damage resultingfrom the perforating operation. Perforation washing is anattempt to ensure that as many perforations as possible

are contributing to the flow from the reservoir. Rockcompaction, mud and cement filtrate and perforation

debris have been identified as types of damage which willlimit the flow capacity of a perforation, and therefore

completion efficiency.

If the objective of the treatment is to remove damage in or

around the perforation, simply soaking acid across theinterval is unlikely to be adequate. The treatment fluid

must penetrate and flow through the perforation to beeffective. In which case all the precautions associated

with a matrix treatment must be exercised to avoid caus-ing further damage by inappropriate fluid selection.

Matrix treatment of the near wellbore area may be de-signed to remove or by-pass the damage. Hydraulic

fracturing treatments provide a high conductivity channel

through any damaged area and extending into the reser-voir.

Both matrix and hydraulic fracturing treatments require adetailed design process which is documented in therelevant Stimulation Manual.


11/13

CONFIDENTIALITY


Well Service and Maintenance Requirements

The term well servicing is used (and misused) to de-scribe a wide range of activities including :

Routine monitoring

Wellhead and flowline servicing

Minor workovers (thru-tubing)

Major workovers (tubing pulled)

Emergency response and containment

Well service or maintenance preferences and require-

ments must be considered during the completion designprocess. With more complex completion systems, the

availability and response of service and support systemsmust also be considered (Fig.10).

Wellbore geometry and completion dimensions deter-

mine the limitations of conventional slickline, wireline,coiled tubing or snubbing services in any application.

WELL SERVICE AND WORKOVER

Fig. 10. Well service and workover.

Completion System Function

Well testing androutine monitoring

Emergency kill and containment

Heavy Workover Units

Drilling rig

Workover rigCombined CT and

snubbing unit

Light Service Units

Slickline

Electric wireline

Coiled tubingSnubbing


12/13

CONFIDENTIALITY


Location

Access to well

Weather/climatic conditionsEnvironmental constraints

Proximity of neighboring interests

LOGISTIC AND LOCATION CRITERIA

Surface Facilities

Separator capacityExport capability

Operational flexibilityDisposal facility

Logistic, Location and Environmental Constraints

Restraints imposed by logistic or location driven criteriaoften compromise the basic cost effective requirement

of a completion system. Special safety and contingencyprecautions or facilities are associated with certain loca-tions, e.g., offshore and subsea.

A summary of the logistic, location and environmental

constraints affecting completion design and configurationinclude well location, environmental conditions, weather

conditions and adjacent land use (Fig 11).

Client Stock, Convention or Preference

The completion configuration and design must ultimately

meet all requirements of the client. In many cases, theserequirements may not be directly related to the reservoir,

well or location (technical factors). An awareness of thesefactors, and their interaction with other completion designfactors can help save time and effort in an expensive

design process.

The following factors are common criteria which must be

considered.

Existing material stocks or contractual obligation

Compatibility with existing downhole or wellhead compo-nents

Fig. 11 Logistic and location criteria

Client familiarity and acceptance

Reliability and consequences of failure

Regulatory Requirements

There are several regulatory and safety requirements

applicable to well completion operations. These mustgenerally be fully satisfied during both the design and

execution phases of the completion process.

Provision for well-pressure and fluid barriers

Safety and operational standards

Specifications, guidelines and recommendations

Disposal requirements

Emergency and contingency provisions


13/13

CONFIDENTIALITY

This manual section is a confidential document which must not be copied in whole or in part or

Revenue and Costs

When completing an economic viability study, or compari-

son, the costs associated with each of the followingcategories should normally be investigated.

Production revenue

Capital cost (including completion component and instal-

lation cost)

Operating cost (including utilities and routine mainte-nance or servicing cost, also workover, replacement or

removal cost.

The specific conditions, determined by the completion

being studied, can be applied to enable a complete andrepresentative cost analysis. In most cases, the order of

importance is as shown, with the revenue stream beingmost critical.

Installation costs are significant if special completionrequirements impact the overall drilling or completion

time. The actual cost of completion components is oftenrelatively insignificant when viewed alongside the value of

incremental production from improved potential or in-creased uptime.

Economic

The economic factors shown below are beyond the scopeof technical preparation for well completion design. How-

ever, they undoubtedly influence the industry. Conse-quently a rudimentary understanding of the factors, and

their interaction with factors previously discussed is ben-eficial.

Market forces (including seasonal fluctuations and swingproduction)

Taxation (including tax liability or breaks)

Investment availability

Company Objectives

A measure of success can only be effectively made if there

are clearly stated objectives. Such objectives may bemacroscopic, but nonetheless will influence the specificobjectives as applied to an individual well or completion.

In addition, the wider company objectives may allowclarification of other selection factors, e.g., where two ormore options offer similar or equal benefit, and no clear

selection can be made on a technical basis.

Desired payback period

Cash flow

Recoverable reserves

well completion planning

Documents