Petrotechnical Services for GeomechanicsImproving operations integrity and enhancing production

In the past, operators turned to experts to solve geomechanics problems often only after encountering them.

Today, most operators consider geomechanics services to aggregate and analyze all available data to manage any challenges that may arise —from exploration and drilling operations to completions and production.

Anticipate drilling hazards earlierSubsurface wellbore-centric or field-wide mechanical earth models (MEMs) can help reduce the risk of drilling challenges. Our geomechanics engineers work with your team to anticipate and avoid costly drilling events. Schlumberger petrotechnical services for geomechanics provides

■ well-trajectory and mud-weight optimization ■ pore-pressure analysis ■ mud-shale interaction evaluation ■ salt-creep modeling ■ real-time drilling support.

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Mitigate production challengesGeomechanics studies help to improve production decisions, whether you are dealing with sand failure in weak formations or stimulating tight reservoirs. We help you to select the most effective completion to meet your production objectives with

■ life-of-well sanding analysis ■ reservoir-sand management ■ hydraulic-fracturing affect prediction ■ casing-integrity optimization ■ waste disposal and cuttings reinjection.

Optimize field managementOur petrotechnical services for geomechanics encompass all disciplines needed to implement a successful field-management plan. Our engineers collaborate with your team to support your field operations decisions with improved understanding of your reservoir's behavior during

■ compaction and subsidence operations ■ caprock-integrity studies ■ fractured-reservoir production ■ fault-seal analysis and reactivation ■ porosity and permeability changes.

Our petrotechnical expertsoffer advanced geomechanics knowledge and analysis of complex reservoirs in challenging environments. Mechanical earth models at basin, field, or well scale can help anticipate issues at any stage during the life cycle of your asset.

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Reduce nonproductive timeIn complex environments, especially in deepwater, HPHT, and subsalt reservoirs, rapid changes in pore pressure and fracture gradients can lead to lost circulation, wash-outs, stuck pipe, loss of tools and equipment, additional casing strings, and unplanned sidetracks. Anticipating and countering these geomechanics-related issues requires an MEM that can be updated and is constrained by actual well data and predrill pore pressure, stability, and fracture gradient profiles.

Our petrotechnical services monitor and update pore pressure and wellbore stability information 24/7 for drilling operations, and data is supported by geomechanics experts in the PTEC* PetroTechnical Engineering Center. We tailor these services to fit even the most geologically complex and hazardous environments.

Identify, understand, and minimize hazardsSchlumberger petrotechnical services for geomechanics combine your offset well information with our extensive global knowledge to build a predrill MEM and provide wellbore stability, pore pressure, and fracture gradient analyses for your drilling program. During drilling operations, Schlumberger wellsite engineers analyze all available LWD, MWD, mud, and gas data in real time to monitor current downhole conditions. Supported by geomechanics experts at operations support centers, we provide updated pore pressure and wellbore stability information that enables you to mitigate problems or quickly implement contingency measures.

Assess Drilling Events in Real TimeGeomechanics services reduce drilling-related downtime and risk

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Geomechanics services can enhance every stage of the reservoir life cycle, from predicting drilling risks in your first well to maximizing recovery from mature assets. Schlumberger geomechanics experts are dedicated to helping you plan and execute operations to reduce risk and boost ultimate recovery.

Monitor and Improve Reservoir Performance

Optimize well placement and drilling operationsWe provide strategic information for drilling engineers, including predictions of safe mud weight windows, identification of unstable formations and high-risk locations, and sub- seismic faults and fractures. Collaborating with your team, we can help guide and rapidly replan well trajectory.

Use formation stresses to your advantage for perforating design Optimal well completion requires identification and estimation of the radial extent of alteration in reservoir intervals. It is important to identify mechanically competent intervals as well as those showing radial alteration by using sonic data and borehole image logs. At the same time, the orientation of earth stresses influences perforation stability. Identifying and shooting per-forations at the best orientation can significantly improve production and ultimate field recovery.

Understand production and stimulationComprehensively stimulating the right zones improves recovery. To help ensure the best result, our petrotechncial services team developed a reservoir-centric, geomechanical approach to stimulation design. The 4D geomechanics software and workflows used during completions, stimulation, and production enhance well perfor-mance and help you anticipate reservoir behavior.

Predict and manage sand failure to mitigate risk Predicting and controlling sand production are crucial components of choosing the right comple-tions program and optimizing ultimate production. Schlumberger experts analyze basic reservoir risks with a well-centric MEM. A field model helps manage the entire reservoir and avoid risky well location decisions, and a dynamic field model predicts the location and onset of sand produc-tion. A sand management advisor system captures this information and predicts sand failure at the perforation tunnel.

Predict and monitor reservoir behavior over timeChanges that affect the subsurface stress levels during the life of a field can cause severe field development and production challenges, such as compaction, subsidence, reservoir perme-ability changes, water breakthrough, and fault reactivation. Geomechanical changes caused by production, combined with complex geology, can influence completion stability and cause casing collapse and sanding across the field. The right information can prevent such problems from occurring or from affecting the field.

Schlumberger provides time-lapse predictions of reservoir behavior using the Petrel* E&P software platform and ECLIPSE * reservoir simulation software. The predictions integrate data from a variety of sources, including 3D surface seismic, well logging, core data, and well test data, and can be calibrated with monitoring data such as time-lapse seismic, microseismic, repeat well logging, subsidence measurements, and wellbore stability events.

Advanced technology and experienced specialists help you place, complete, stimulate, and monitor your wells

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With more than 500 annual projects from 50 offices around the world, Schlumberger petrotechnical services has the largest number of geomechanics experts and completed projects, including operations in unconventional reservoirs such as coalbed methane, gas hydrates, shale gas, shale oil, and tight gas.

The Schlumberger Portfolio of Petrotechnical Services for Geomechanics

DRIllIng geOMechAnIcs PRODUctIOn geOMechAnIcs ReseRvOIR geOMechAnIcs

STAnDArD—Geomechanics Field Operations Products

Real-time services (wellbore stability, DrillMAP* drilling planning and management tool, pore pressure monitor, fracture gradient), rapid well-centric MEM (wellbore stability and depth of damage)

Sand management advisor, calibrated hydraulic fracture prediction, casing integrity

InTErMEDIATE—Geomechanics Planning and Design Services

Salt-creep analysis, mud-shale interaction, wellbore stability (anisotropic) and planes of weakness, wellbore strengthening, pore pressure, fracture gradient, shallow hazards

Fractured reservoir production, caprock integrity, casing integrity numerical analysis software, creep and compaction integrity, gas hydrate hazards

Fault-seal analysis, 3D caprock, integrity, natural fracture, production analysis, reservoir compaction, subsidence (nucleus of strain)

ADVAnCED—Complex Geomechanics Studies

High-risk well planning, field development, drilling planning, uncertainty and probability modeling, applied workflow training

Waste disposal, cuttings reinjection, sand rate predictor, heavy oil production, uncertainty and probability modeling, caprock integrity (well by well), hydraulic-fracture permeability prediction, applied workflow training

Reservoir compaction and subsidence, field-performance modeling, injector performance planning, gas storage integrity, exploration geome-chanics, uncertainty and probability modeling, CO2 sequestration, applied workflow training

SErV

ICES

Reduced uncertaintyReduced NPT; fewer lost-in-hole operationsHazard avoidance and safer drilling operationsImproved well, platform, trajectory Better risk managementReduced exploration costEnhanced exploration operations

Optimized platform locationImproved well trajectory, placement and constructionIncreased ROP and drilling optimizationImproved stimulation designImproved facilities designReduced development cost

Prolonged field lifeMore accurate dynamic modelingLife-of-well integrityManagement and mitigation of solid productionProduction optimizationReduced operation cost

GOAL

S

Conventional reservesUnconventional reservesShale gasCoalbed methaneHeavy oilPresalt exploration

Reservoir characterizationOverpressureNew drilling locationNew well designSidetracking

Development drillingHPHT drillingSalt drillingDrilling efficiency

Field-development planningDeepwater field developmentGeothermal developmentStimulation optimizationSolid productionFull-field reviewDynamic forward modeling

Field management and productionWaste disposalEnhanced oil recoveryFractured-reservoir managementUnderground storage

APPL

ICAT

IOn

S

comprehensive modelsOur service provides comprehensive well-centric and fieldwide MEMs to enhance predictions. In situations with high initial uncertainty, despite a possible lack of input or calibration data, initial models can be used to help you prepare for mitigation or contingency strategies before drilling.

Schlumberger next-generation MEMs use Petrel software for

■ radial grid building around the wellbore ■ simulating linear and nonlinear

elastoplastic rock behavior, both during and after drilling.

Once the model and workflow are developed, new data are used to update, refine, and calibrate the model in real time.

Integrated softwarePetrel reservoir geomechanics simulation provides accurate fieldwide stress and strain predictions and relates rock stresses to reservoir properties. The simulator can be coupled with ECLIPSE software to obtain porosity, permeability, and fracture conduc-tivity updates that improve reservoir production history matches.

seamless data interactionOur reservoir geomechanics simulation predicts and explains reservoir behavior with

■ finite-element numerical modeling with unstructured grids and multiple cell shapes that permits accurate modeling of complex geometries such as pinch outs

■ mechanical properties and complex variations in material properties to accommodate unlimited numbers of faults and fractures

■ models that accommodate specific stress-strain relationships, including specialized plasticity laws and chalk models

■ specific sector models that more accu-rately simulate wellbore stability and sanding during production and can reveal opportunities to improve casing design

■ parallel processing that can manage multimillion-cell models

■ complex schedules for production, injection, and stimulation jobs.

Collaborative Software ApplicationsThe Schlumberger team of experts enhances the traditional geomechanical approach with a number of integrated technologies.

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In-depth 3D velocity model (left) and pore pressure prediction (right) in equivalent mud weight using the seismic velocities for the 50-mi2 area.

Accurate pore pressure prediction in HPHT well reduces risk, saves rig time

One operator was drilling in the Gulf of Mexico, and its offset wells located near its exploration well experienced up to 10 days of nPT from stuck pipe, kicks, lost returns, and the need to sidetrack, and current rig rates approaching USD 100,000 per day could cause cost overruns from hundreds of thousands to millions of dollars.

There were three main drilling challenges. It was important to find the optimal depth for the 135⁄8-in casing; if it were set too shallow, it would be difficult to drill into the anticipated overpressured zone without experiencing losses and wellbore instability problems.

Optimizing the mud weight program and planned equivalent circulating density was important to minimize wellbore instability in the 97⁄8-in and 81⁄2-in hole sections, which had a narrow 1.0 lbm/gal safe mud weight window.

Finally, insufficient offset data were available to calibrate the predrill model in the 81⁄2-in hole section, where temperature exceeded 300 degF [149 degC] and pressure reached approximately 18,500 psi [128 MPa].

During the planning stage, the petrotechnical services for geomechanics team used high- quality 3D prestack time migration (PSTM) seismic velocity to determine the pore pressure and fracture gradient in a 50-mi2 area. A locally calibrated overburden stress field was derived from density logs, and a velocity to effective stress transform was established using a detailed analysis of the offset well data. The team then performed a dipping sand analysis to calculate pressures in three sands at the location of interest.

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The Schlumberger team of petrotechnical experts identified the root cause of drilling problems in the area and provided guidelines for the safe mud weight window using Schlumberger DrillMAP drilling planning and management tool.

Schlumberger then acquired real-time measure-ments for advanced drilling optimization. The acquisition of new data enabled the team to monitor the model on the rig in real time and the geomechanics engineers to make daily updates for an improved prediction ahead of the bit.

Using the results from the predrill model and the application of real-time monitoring and updating, the 135⁄8-in casing depth was successfully extended from 11,200 ft to 11,821 ft [3,414 m to 3,603 m], enabling the operator to eliminate the 105⁄8-in × 12¼-in expandable liner in the lower part of the well. The mud weight and casing programs were optimized to avoid well control and wellbore instability issues, enabling successful drilling to a total depth of 20,500 ft [6,248 m] with no nPT.

The real-time sonic measurement and geome-chanics monitoring and updating enabled the operator to make informed decisions during the drilling operation and prevent minor problems from becoming catastrophic. As a result, the next well was drilled on schedule.

Effective stress, psi

Seis

mic

vel

ocity

, ft/s

10,000

9,500

9,000

8,500

8,000

7,500

7,000

6,500

6,000

5,500

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0 500 1000 1,500 2,000 2,500 3,000 3,500

Loading

Unloading

Velocity-effective stress relationship in the area showing type 1 (loading) and type 2 (unloading) pressure regimes.

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Wellbore stability modeling services support successful appraisal of new oil

An operator in the norwegian sector of the north Sea needed to establish parameters for a three-year drilling program. It had drilled its first three appraisal wells to delineate the find, determine oil and reservoir properties, fluid contacts, and sand connectivity, and estimate recoverable reserves. The sands were interbedded with silt and coal layers and overlain by weak shales in this formation, which could present significant drilling and completion hazards in horizontal sections as a result of variations in rock strength.

The client selected Schlumberger to provide openhole logging, LWD, and directional drilling services and to perform a detailed wellbore stability study.

Geomechanics petrotechnical experts built a predrill mechanical earth model (MEM) of the reservoir using a proprietary Petrel E&P software platform plug-in based on all relevant geological, petrophysical, drilling, and geomechanical data from offset wells in the field. Projecting rock properties onto a proposed well trajectory, they identified potential zones of drilling risk while creating the wellbore stability model. The well path, drilling design, and operational parameters were optimized to ensure safer operations.

Upon openhole logging of the first vertical well, Schlumberger provided inputs to refine the MEM, updating the predrill wellbore stability model and making mud weight recommenda-tions for the two planned horizontal sidetracks to avoid the main drilling hazards in the weak overburden shales.

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Drilling mud weight of 1.45 relative density

reaming mud weight of 1.30 relative density

Drilling Reaming

Maximum caliperMinimum caliper

Dept

h, m

2,4002,400

2,4252,425

Changes in borehole shape with variations in equivalent circulating density based on LWD EcoScope* multifunction logging-while-drilling service images, available in real time.

While drilling both boreholes, Schlumberger acquired time-lapse EcoScope LWD data to provide hole shape analysis through these weak shales. real-time indications of hole enlargement during wiper trips enabled decisions to be made regarding drilling practices and increasing mud weight for suc-cessfully pulling out of hole without collapse. Schlumberger experts then updated the wellbore stability model with measurements from the LWD density caliper data to confirm predictions from the geomechanical model about the stress regime.

The first sidetrack established reservoir proper-ties and sand connectivity in the western part of the structure; the second sidetrack did the same for the eastern sector. All three wells proved reservoir potential and provided the data necessary to estimate reserves.

Both appraisal wells were drilled successfully. Based on high-resolution LWD data used to refine the reservoir geomechanical model and the availability of solid wellbore stability predictions, geomechanics petrotechnical experts calibrated a number of critical reservoir properties and parameters required for the client to begin planning future field develop-ment drilling and completion operations.

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Dept

h, m

Wellbore stability model showing breakout orientation (left) and the stress distribution around the borehole (right) using the 3D wellbore stability viewer in the Petrel plug-in.

Wellbore stability model through the weak overburden shale, calibrated using LWD measurements from the EcoScope service.

Mud-Weight Relative Density = 1.45

Mud weight while drilling does not intersect the breakout limit.

Mud weight during wiper trips intersectsbreakout limit, thus hole enlargement is predicted and validated with density calipers.

Lithology Calibrated mud– weight window

based on wellbore stability forecast and time–lapsed

caliper data

Predicted borehole

failure

Breakout

Mud Loss

Breakdown

KickTensile Failure

LithologyMud-Weight Relative Density = 1.30

1 g/cm3 2

1 g/cm3 2Gamma Ray0 gAPI 150

Low

Low

High

High

2,400 2208.92

2,425

Shallow Knockout

Wide Breakout

With an aggressive drilling campaign, an operator faced the tough task of improving drilling efficiency and practices to extend the life of a mature field in a challenging north Sea environment. As field production declined, economic viability demanded a performance change. Instability events resulting from a combination of natural formation instabili-ties and drilling para-meters and practices needed to be addressed by identifying problems quickly and defining appropriate drilling and operational contingencies before hazards arose. Appropriate remedial actions needed to be based on what was occurring downhole to avoid incorrect diagnoses and solutions that could lead to further damage.

The operator's drilling program in the north Sea, in which more than 300 boreholes had been drilled, involved infill targets from donor wells sidetracked near the base of the 95⁄8-in casing or step-out targets with sidetracks higher up existing wells. As the field matured, the safe mud window was becoming progressively narrower, making drilling more difficult.

In addition, the likelihood of losses increases in maturing fields as reservoir pressures decline. To reach targets farther from the platform, higher mud weights are needed to prevent collapse of the overburden shales, and hole cleaning becomes more difficult. Mud weight selection becomes a compromise of threading the needle between hole collapse and losses. Of the 94 boreholes drilled by this operator over a 5-year period, 45% were lost as a result of drilling or completion problems, and a BHA was lost in 40% of these failures.

The operator selected the Schlumberger petrotechnical services for geomechanics group to lead a collaborative team to identify, predict, and prevent costly wellbore failures through an innovative combination of operations monitor-ing, geomechanics behavior analysis, and risk management, including the integration of seismic, well logs, and core measurements.

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Variation in the nature and fabric of shales across the North Sea field.

Fractured Competent Layered Layered shale interspersed with weak layers—some parts fail,

others remain intact

Geomechanics collaboration improves drilling operations, reduces cost, and optimizes production decisions

Schlumberger provided a multiwell sonic workflow using new technology that integrated virtual seismic profile, the Sonic Scanner* acoustic scanning platform, and core tests to describe anisotropy parameters in the overburden. The workflow allowed for marked improvement in fieldwide seismic calibration and geomechanical models.

To quantify anisotropic behavior, the team used the Sonic Scanner platform, borehole seismic and core-log integration, and TerraTek* rock mechanics and core analysis services for field-wide calibration of sonic and seismic data.

This workflow enabled the capture and classifica-tion of historic drilling events—key processes in determining causes of wellbore failure—to be performed systematically and efficiently in the fieldwide multiwell environment. This method helped to diagnose more than 120 wellbores for instability causes. The anisotropy results success-fully refined wellbore stability predictions and seismic interpretations, prompting the client to conduct similar anisotropy investigations for other overburden shales.

As a result of the knowledge gained during this collaborative project, nPT costs for one year were reduced by more than 60%, and further, no BHAs were lost after implementation of the team solutions. The closer collaboration between disciplinary experts and the field-proven practices were rapidly incorporated into future well planning and drilling operations, and will continue to help mitigate risks and reduce costs.

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Distribution of problem wells versus borehole deviation, similar to rock strength variation with bedding plane angle.

Forties Miocene/Oligocene/Eocene Hole Sections

Enhanced geomechanics workflows improve horizontal well campaigns

Several years ago, an operator initiated a series of horizontal drilling campaigns in a South American rainforest.

Wells drilled over previous decades had encountered considerable geomechanical and drilling problems. Costly sidetracks were common. The average historical nPT per well was 2.2 days. Geomechanical incidents— including stuck pipe, wellbore instability, and tight holes—accounted for a full 97% of nPT in deviated and vertical wells and 69% of nPT in previous horizontal wells. Only five horizontals wells had been drilled before—all with aggressive dogleg severities, using conventional downhole motors that required sliding almost 100% of the time. Cuttings removal had been inefficient, lowering rOP. Stationary components had created friction, further reducing rOP and causing mechanical and differential sticking of the drillstring and packoffs.

Due to changes in reservoir conditions, advance-ments in technology, and new environmental constraints, the operator decided to implement a fresh approach.

Schlumberger petrotechnical services joined forces with the operator to create a geomechanic team. Working closely with the client, consultants delivered a comprehensive multidisciplinary evaluation. This unique geomechanics and drilling optimization workflow had four main phases: data audit, predrill earth modeling, modeling while drilling, and end-of-well review.

For the data audit, the team compiled, integrated, and analyzed all available data in geology, geophysics, geomechanics, reservoir engineering, and drilling engineering. As part of predrill planning, they performed a geomechanics study, building a 1D MEM, which provided a reliable wellbore stability forecast. They analyzed horizontal stress magnitude and orientation, performed trajectory sensitivity analysis, and evaluated potential drilling hazards. Finally, they created a plot using the DrillMAP drilling planning and management tool to summarize risks and guide preventive measures while drilling. During drilling, Schlumberger petrotechnical experts compared data from the rig with the predrill forecast to detect deviations and unexpected borehole conditions. After drilling, geomechanics engineers met with the client to document key performance indicators, identify lessons learned, and optimize plans for subsequent wells.

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In addition to the multidisciplinary evaluation and support, Schlumberger also recommended replacing traditional downhole motors with a modern rotary steerable system (rSS). Over a 3-year period, the operator drilled seven successful horizontal wells in the basin.

The first two wells had no wellbore instability issues, no stuck pipe, and only moderate tight hole events, which were easily managed at the rig site. In another field, historical nPT that resulted from geomechanics-related drilling events dropped from approximately 70% to 15%, or from an average of more than 2 days to less than a day.

Use of the rSS improved drilling performance, required fewer BHAs per well, increased total well length 200–300 meters per well, and increased rOP despite the longer wellbores. Ultimately, the operator hit its drilling targets 5 to 9 days ahead of schedule, saving rig time, bringing production online sooner, and accelerating return on investment.

As a result, costs were dramatically reduced. Previously, drilling events, fishing, lost in hole events, and sidetracking had cost an estimated USD 2.38 million (sidetracking alone cost USD 2.2 million) per well. With the new approach, the client not only eliminated about USD 2.36 million of those costs, but saved an additional USD 420,000 per well by hitting targets ahead of schedule. net savings: approximately USD 2.78 million per well.

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Integrated multidisciplinary approach. This approach enabled the operator to hit targets in 9 fewer days than anticipated.

Actual drilling performance

Planned time versus depth (former technical limit)

Geomechanics-related drilling events and NPT in one field plummeted from about 70% in previous wells —an average of 2.2 days per well— to 15% in the new campaign, or an average of 0.75 days per well.

Previous drilling campaigns(15 directional, 5 horizontal)

new drilling campaign(2 horizontal)

Tight hole/overpull

20%

Low rOP/bit

7%

Other24%Lost circulation 0%

Unstable zones 0%

Stuck pipe49%

Gumbo, 10.5 hr

4%

Lost circulation, 38 hr

15%

Other, 198 hr81%

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Petrotechnical Services for Geomechanics

*Mark of SchlumbergerOther company, product, and service names are the properties of their respective owners.Copyright © 2012 Schlumberger. All rights reserved. 12-DC-0058

At every stage of the reservoir life cycle, our global network of geomechanics experts provides critical services to help you improve operations integrity and make better-informed decisions for the life of your field, from exploration and development to production.