OilField Geomechanics LLC * 24200 Southwest Freeway Suite 402#293 * Rosenberg, Texas 77471

Tel: (832)327.9566 * marisela@ofgeomech.com – www.ofgeomech.com

OFG’s Approach to Hydraulic Fracturing for Unconventionals

In order to develop nano/microdarcy permeability unconventional reservoirs, multistage hydraulic fracturing is often needed to make

economic wells. At OFG, we believe three main scenarios may be present in the unconventional plays: a) highly fractured rock mass

where HFs cannot be created (left, below); b) formations with cemented or nonexistent discontinuities where traditional HF design

applies (right); or c) formations with weakly cemented or open/partially open natural fractures where the stimulation objective is to

stimulate these weak planes (center). We start by understanding (via resource characterization) the particular scenario for hydraulic

fracturing design – because different design strategies are needed for each case.

The critical issues we consider are:

- Presence of the resource (TOC, maturity);

- Presence of natural fractures and/or weak planes (free

surfaces to be converted to flow area) and their connectivity and

hydro-mechanical properties;

- Fluid pressure and fluid type – high pressures favor the

stimulation of natural fractures, as the effective stresses are low and

less shear is needed for stimulation, and can pressure be increased

in offset wells during a stimulation;

- Influence of stresses and mechanical properties on HF

geometry and SRV – some conditions are more favorable than

others; and

- Influence of operational parameters and HF design on HF

geometry and SRV.

Each of these issues, other than the presence of the resource, are

controlled by the geomechanical behavior of the rock mass

(stresses/strains and failure) coupled with fluid flow and pressure changes. OFG uses models that incorporate the right physics for

coupled geomechanics and fluid flow, including the natural fractures, to represent rock mass failure, stress capture effects, changes

in the shape of HFs with multiple stages, changes in ISIP (stress shadows) and its effect on the natural fractures, microseismic

behavior, casing deformations, etc. The field data (microseismics, injection pressures, PLTs, tracers and ultimately production)

together with the models help us understand and quantify the effects of geomechanical, reservoir, geological and operational

parameters on stimulation efficiency (increased SRV) and optimization strategies.

Summary of Services and Workflow for HF in Unconventionals

Resource Characterization Support Geomechanical assessment (stress, pore pressure, and rock mechanical properties - 1D or 3D sector models).

Design of Data Acquisition Program

Geomechanical Evaluation of Microseismic Data Numerical geomechanical simulations of synthetic microseismicity

Hydraulic Fracture Stimulation Design and Optimization DFIT/FET/Mini-frac design and interpretation

Evaluation and optimization of operational parameters (rates, volumes, etc.)

Evaluation and optimization of stage spacing-stress shadows

Post-frac analyses

Simulation history-matching to field MS data and injection data

Multi-Stage/Multi-Well Completions Design and Optimization Stage spacing/Cluster evaluation and optimization

Evaluation and optimization of multi-well stimulation strategies (Simul-Frac, Zipper-Frac, etc)

Evaluation and optimization of well placement and orientation

Upscaling of Propped/Stimulated Volume for Flow Simulations- Production Forecasting and History Matching Single porosity, Directional permeability, Double porosity/double permeability models

OilField Geomechanics LLC * 24200 Southwest Freeway Suite 402#293 * Rosenberg, Texas 77471

Tel: (832)327.9566 * marisela@ofgeomech.com – www.ofgeomech.com

THESE SERVICES ARE INCLUDED IN AN INTEGRATED WORKFLOW FOR UNCONVENTIONAL RESOURCES

Hydraulic Fracturing for Unconventionals – Example Simulations

Plan view of a slice at the wellbore in a 3D HF model

showing pressure development and synthetic MS events

generated by the rock failure during a hydraulic fracture

simulation for two different DFNs. To the left is a

‘sparse’ fracture network and on the right is a ‘dense’

network of fractures. In the top figures, note the

difference in pressure invasion in the natural fractures

and the difference in hydraulic fracture length (the

horizontal fracture from left to right). The lower figures

represent the generation of synthetic microseismicity;

note the difference in microseismic patterns.

Aperture (width) distribution along the main HF plane – this is a vertical section of the sparse (left) and dense (right) DFN at the

injection point. The deformation of the blocks defined by the natural fractures produce a very complicated aperture pattern in the main

HF – this is not good news for proppant placement!

Quantification of the stimulated area (left- 3 times more in the dense DFN) and leakoff as a function of injection time (2 times in the

dense DFN) for different initial apertures of the natural fractures. On the right the influence of flow rate (injection time) on the

stimulated area and leakoff in the fractures – a 30 % increase was seen when flow rate was decreased. We can explore with you several

injection schemes that could improve your stimulation efficiencies and economics.

Stress shadows occurring from three equal-volume stages

pumped from two parallel horizontal wellbores in a zipper

frac configuration. Left: Shmin increase distribution at the

end of the third frac stage. Right: horizontal shear stress

distribution from the tips of the three HF stages. Note how

complicated and non-symmetrical the stress patterns are.

The complicated stress influence over the behavior of

natural fractures needs to be accounted for in order to

design optimum stage and well distances as well as

correctly interpret microseismic results.

2.9

:1

1.8

:1

Sparse

Dense(+30%)

Sparse

Dense(+20%)

Decrease Q

Inj. Pt. Inj. Pt. HF Trace HF Trace

HF Trace

HF Trace

OilField Geomechanics LLC * 24200 Southwest Freeway Suite 402#293 * Rosenberg, Texas 77471

Tel: (832)327.9566 * marisela@ofgeomech.com – www.ofgeomech.com

OFG’s Integrated Approach to Unconventional Evaluations

OilField Geomechanics can integrate with your team to provide geomechanical characterization and the

geomechanics support for hydraulic fracturing optimization

Static Model (TOC, Petroph: Poro,

perm, reservgeometry,

structures, seismic attrib, elast. seismic

inversion)

Geological Model (Natural fracs, weak

planes, intensity, open/closed,

mineralization)

Geomech. Model(Stresses, Pore Press,

Mech. Properties matrix and fractures)

DFN Realizations – Stat. Model –

(seismic, logs, cores, outcrops) Upscalingof Hyd. properties

RESERVOIR CHARACT.

‘Sweet’ Spots,Well Location,

Landing Location

STIMULATIONModeling,

CompletionDesign and

Optimization

Shale Play & DFN Scenarios

(construct HF models)

HF Modeling & Hist. Match (pressure, MS and prelim flow area

from product.)

HF Geometry and Improved SRV (HF +

Nat. fractures)

Multiwell HF -Zipper Fracs

(designs to max. flow area)

Flow Area Optimization

(parametric analysis: rate, fluid, proppant)

Stress Shadows (opt. stage spacing,

near-wellbore effects)

Most Likely Reservoir

Parameters + # stages, well length

Production History Matching (post-frac,

few days, months, years). Use improved

SRV

Model of Well/Multi-well/

Reserv. (single/ double poro-perm)

Optimum Well Spacing & Landing

LocationForecast Scenarios

Exploitation Plan (NPV, etc.)

FLOW SIMULATIONProduction

Optimization

Reserv. Eng.

Coupling @ specific

times

Upscaling of Propped Flow Area

(HF & Stimul. Nat Fracs) to Double

Poro/Perm Model

Pressure Saturations Flow Area

OilField Geomechanics LLC * 24200 Southwest Freeway Suite 402#293 * Rosenberg, Texas 77471

Tel: (832)327.9566 * marisela@ofgeomech.com – www.ofgeomech.com

Selected Publications (see www.ofgeomech for a more complete list) Nagel, N.B., Sheibani, F., Lee, BT., Agharazi, A., Zhang, F., 2014, “Fully-Coupled Numerical Evaluations of Mulitwell Completion

Schemes: The Critical Role of In-Situ Pressure Changes and Well Configuration”, SPE Paper 168581 presented at the SPE Hydraulic

Fracturing Technology Conference, The Woodlands, Texas, USA, 4-6 February.

Agharazi, A., Lee, BT., Nagel, N.B., Zhang, F., and Sanchez-Nagel, M., 2013 “Tip-Effect Microseismicity – Numerically Evaluating

the Geomechanical Causes for Focal Mechanisms and Microseismicity Magnitude at the Tip of a Propagating Hydraulic Fracture”,

SPE Paper 167129 presented at the SPE Unconventional Resources Conference-Canada, Calgary, Alberta, 5-7 November.

Zhang, F., Nagel, N.B., Sanchez-Nagel, M., Lee, BT., Agharazi, A., 2013, “The Critical Role of In-Situ Pressure on Natural Fracture

Shear and Hydraulic Fracturing-Induced Microseismicity Generation”, SPE Paper 167130 presented at the SPE Unconventional

Resources Conference-Canada, Calgary, Alberta, 5-7 November.

Nagel, N.B., Zhang, F., Sanchez-Nagel, M., Lee, BT., Agharazi A., 2013, “Stress Shadow Evaluations for Completion Design in

Unconventional Plays”, SPE Paper 167128 presented at the SPE Unconventional Resources Conference-Canada, Calgary, Alberta, 5-7

November.

Nagel, N.B., F. Zhang, M. Sanchez-Nagel and B. Lee, 2013, “Evaluation of Stress Changes Due to Multi-Stage Hydraulic Fracturing

– Consideration of Field Results”, presented at Rock Mechanics for Resources, Energy and Environment, Eurock13, the ISRM

International Symposium, Wroclaw, Poland, 21-26 September.

Rios, A.M., G. Gutierrez, N.B. Nagel, F. Zhang, M. Sanchez-Nagel and B. Lee, 2013, “Stress Shadow Evaluations for Chicontepec –

Evaluating New Completion Options”, Paper ARMA 13-200 presented at 47th US Rock Mechanics/Geomechanics Symposium, San

Francisco, CA, USA, 23-26 June.

Zhang, F., N.B. Nagel, B. Lee and M. Sanchez-Nagel, 2013, “The Influence of Fracture Network Connectivity on Hydraulic

Fracture Effectiveness and Microseismcity Generation”, Paper ARMA 13-199 presented at 47th US Rock Mechanics/Geomechanics

Symposium, San Francisco, CA, USA, 23-26 June.

Nagel, N.B., F. Zhang, M. Sanchez-Nagel, X. Garcia, and B. Lee, 2013, “Quantitative Evaluation of Completion Techniques on

Influencing Shale Fracture Complexity”, presented at ISRM International Conference for Effective and Sustainable Hydraulic

Fracturing, Brisbane, Australia, 20-22 May.

Savitski, A. A., M. Lin, A. Riahi, B. Damjanac and N.B. Nagel, 2013, “Explicit Modeling of Hydraulic Fracture Propagation in

Fractured Shales”, in International Petroleum Technology Conference, Beijing, China.

Nagel, N. and M. Sanchez-Nagel, 2011, “Stress Shadowing and Microseismic Events: A Numerical Evaluation”, Paper SPE 147363

presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, USA, 30 October-2 November.

Gil, I., N.B. Nagel, M. Sanchez-Nagel, and B. Damjanac, 2011, “The Effect of Operational Parameters on Hydraulic Fracture

Propagation in Naturally Fractured Reservoirs – Getting Control of the Fracture Optimization Process”, Paper ARMA 11-391

presented at ARMA 45th U.S. Rock Mechanics/Geomechanics Symposium, San Francisco, California, USA.

Omdal, E., M. V., T. G. Kristiansen N. B. Nagel, R. I. Korsnes and A. Hiorth, 2010, “Deformation Behavior of Chalk Studied Close

to In Situ Reservoir Conditions”, Rock Mech. Rock Eng., 43, pp557-580.

Nagel, N. B., and F. Meng, 2009, “Wellbore Strengthening: The Effect of the Permeable Case”, Paper AADE-09-NTCE presented

at Unlocking the Potential: Sustaining Drilling Performance, American Association of Drilling Engineers (AADE) National Technical

Conference & Exhibition, New Orleans, Louisiana, USA.

Guo, G., and N. B. Nagel, 2009, “Cuttings Reinjection Case Histories”, paper presented at Unlocking the Potential: Sustaining Drilling

Performance, American Association of Drilling Engineers (AADE) 2009 National Technical Conference & Exhibition, New Orleans,

Louisiana, USA.

Nagel, N. B., and F. Meng, 2007, “What Does the Rock Mechanics Say: A Numerical Investigation of Wellbore Strengthening”,

Paper AADE-07-NTCE-65 presented at the American Association of Drilling Engineers (AADE) National Technical Conference &

Exhibition, Houston, USA.

Nagel, N. B., 2006, “On the Importance of Cuttings Reinjection”, Schlumberger Oilfield Rev., 18(4), 1 (Winter 2006).

Doomhof, D., T. G. Kristiansen, N. B. Nagel, P. D. Patillo and C. Sayers, 2006, “Compaction and Subsidence”, Schlumberger Oilfield

Rev., 18(3), pp50-68 (Autumn 2006).