Gas Migration ControlEngineering SuiteRisk evaluation and tailored solutions

The Schlumberger Gas MigrationControl Engineering Suite is the effec-tive and reliable answer for cementingwells with potential gas migrationproblems. The process incorporatestwo major steps.

� Evaluating gas migration risks, usingthe innovative GasMigrationAdvisor*software

� Recommending tailored solutions basedon gas migration risk severity andbottomhole circulating temperature

The Gas Migration Control EngineeringSuite includes the GasMigrationAdvisorsoftware application, a complete port-folio of gas migration additives, and

the implementation of good cementingpractices, starting with proper mudremoval engineered with WELLCLEAN II*software.

GasMigrationAdvisor GasMigrationAdvisor software isdesigned to evaluate gas migrationseverity based on well geometry, fluidplacement, and reservoir properties.It computes a composite risk basedon three parameters.

� The pressure decay limit (PDL),which is associated with the loss ofhydrostatic pressure until reachingequivalent reservoir pore pressureduring cement setting

� The mud removal risk, which isassociated with the degree ofcement coverage and the possibilityof leaving mud on the walls of thewellbore above as well as below thegas zone(s)

� The formation productivity risk,which is associated with the abilityof the formation to deliver a criticalvolume of gas during setting time

Assessing mud removal is a criticalelement in controlling gas migrationissues. Mud left either on the forma-tion wall or as a channel will serveafter cement setting as a path for gasmigration. Poor mud removal cannotbe cured with cement gas migrationadditives.

Risk evaluationand tailored solutions >>

The Gas Migration Control Engineering Suite offers cost-effective solutions for specific needs.

Pressure

Time

Initial pressure

Reservoir pressure

After this point,gas can invade

Cement set

Critical HydrationPeriod

Using all available well data,GasMigrationAdvisor software com-putes a composite gas migration riskseverity for each gas zone and for theentire well. It also provides recom-mendations on how to lower the riskof gas migration.

GasMigrationAdvisor software furtherperforms a sensitivity analysis of therisk of gas migration to possible varia-tions from the design case (e.g., changesin mud property, openhole caliper, etc.).Such sensitivity analysis allows opti-mizing a solution that will be robustboth to poorly known parameters andto changes that can occur betweenthe time the job is designed and thetime it is performed.

Solutions portfolioDifferent bottomhole temperaturesand gas migration risk levels require different solutions. TheGasMigrationAdvisor software recom-mends solutions adapted to each risklevel and temperature range. TheSlurryDesigner* computer-aidedblended design computes the mini-mum concentration of the gas migra-tion solution based on solid volumefraction and bottomhole circulatingtemperature. These solutions havebeen fully tested, qualified as gas-tightsystems in the laboratory for theoperating severity and temperatureenvelope. They have also been field-tested in different parts of the world.These preliminary tests mean the

slurry need not be checked for gas-tightness in a particular application.The portfolio comprises the GASBLOK*gas migration control cement additivesfamily (D500, D600G, D700), the ISOBLOK*isolation additives group, and the latestgeneration of fluid loss additives(D168/D167 and D193).

These solutions are compatiblewith CemCRETE* cement technology,FlexSTONE* flexible cement technology,and AccuSET* smart cement hydrationcontrol technology, as well as standardSchlumberger cement additives. Noslurry property is compromised bythe use of these tailored solutions.

The GasMigrationAdvisor

software recommends

solutions adapted to each

risk level and temperature

range.

Schlumberger offers the software, tools, and best practices you need.

Gas Migration Control Engineering Suite

GasMigrationAdvisor

Gas migration severity

WELLCLEAN II

Solution

Solutions portfolio

D700 GASBLOK HT

D600G GASBLOK

ISOBLOK

D168/D167

D193

D500 GASBLOK LT

SlurryDesignerComputer-aided blend design

Cement Hydration Analyzer (CHA)

experience and innovation >>

Technical approach, unsurpassed delivery

Schlumberger is the industry leader in gas migration control.

For more than 2 decades, we have solved our clients' gas migration

issues, providing cost-effective solutions. The new Schlumberger

Gas Migration Control Engineering Suite offers customized

solutions to fit every well's needs.

Gas Migration Control Engineering SuiteRisk evaluation and tailored solutions

www.slb.com/gasmigrationcontrol06-CE-048 January 2007*Mark of SchlumbergerCopyright © 2007 Schlumberger. All rights reserved.Produced by Schlumberger Marketing Communications