Techniques and Technology in the Evaluation of Unconventional Shale Gas Resources
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Techniques and Technology in the Evaluation of Unconventional
Shale Gas Resources
Robert S. KuchinskiWeatherford Oil Tool Middle East
3rd India Unconventional Gas Forum (IUGF) - 2013
Mumbai, IndiaJanuary 18, 2013
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• I would like to express my gratitude to the following organizations for making this presentation possible:– The organizers of the 3rd India Unconventional Gas
Forum (IUGF) - 2013 – Weatherford India
Acknowledgements
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• Not all shale reservoirs are alike• Must understand core area of shale play• Completion costs consume 50 to 60% of well
costs…and rising• Continuous learning thru data acquisition at
every phase of well life is essential to maximize recovery from these reservoirs
Key Learning’s from North America
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Unconventional: Satisfaction Survey
TOTAL SAMPLE
BARNETT SHALE
MID-CONTINENT
GULF COAST
ROCKIES
WILLISTON/ BAKKEN
MARCELLUS/ UTICA SHALE
PERMIAN BASIN
EAGLE FORD SHALE
HAYNESVILLE + FAYETTEVILLE
CANADA
INTERNATIONAL
0% 10% 20% 30% 40% 50%
24%
47%
35%
33%
32%
30%
25%
22%
21%
21%
19%
19%
Source: Welling & Company
SHARE OF FRAC JOBS NOT MEETING PERFORMANCE EXPECTATIONS
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Root Cause to Challenges in Unconventional Exploitation
FAILURE TO UNDERSTAND SUBSURFACE
POOR FRAC DESIGN
DOWNHOLE EQUIPMENT/ TOOLS
INEXPERIENCED CREWS / HUMAN ERROR
SURFACE EQUIPMENT
GEL NOT BROKEN UP
0% 20% 40% 60% 80%
73%
18%
14%
13%
12%
1%
ROOT CAUSE OF FRAC JOBS NOT MEETING PERFORMANCE EXPECTATIONS
Source: Welling & Company
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Shale Fabric Analysis
Ultra-Thin Sections
2D Nano-Scale ImagingElemental Fabric Mapping
“Shale Reservoirs have large variation”
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Evaluation of Unconventional Resources
Gus Archie 1907-1978
Increasing Gamma Ray
Increasing Intragranular Porosity
Intergranular Porosity and disassociation between rock and fluid
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Evaluation of Unconventional ResourcesClean Gas Sandstone Minimal Clay Higher Energy Depositional
Environment Coarse grained -Well Sorted Favorable Porosity and
Permeability Diagenesis can limit K Log evaluation based on the
disassociation between fluid and rock
Unconventional Clastic Gas Variable Clay Content Log evaluation not useful for fluid
determination Rocks required to complete
analysis Rocks and fluid associated
Shaley Gas Sandstone Finer grain size and
presence of clay reduce K Clay content disrupts Sw
Calculation Sw equations modified to
cope with clay Logs required for
mechanical properties Hydraulic fracturing
becomes be necessary Diagenesis can limit K and
mineralogy
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• Critical to Understand the Resource Quality and to be able to grade it.– What is extent of the Core Area?
• The Arial sweet spot• Highest concentration of gas• Most productive• Lowest cost to develop• Most valuable
– What other areas are productive?• Gas concentration and Productivity vs. Core Area?
– What is the extent of the fringe area?• What is Gas concentration and Productivity?
The Core Area
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2011 Shale AFE Breakdown
10,500’ TVD14,100’ MD
3,600’ Lateral 12 Stages
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10,500’ TVD15,500’ MD
5,000’ Lateral 16 Stages
2012 Shale AFE Breakdown
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Resource Play Formation Evaluation
Uranium content TOC
Elemental analysis Brittleness evaluation
Detailed gas composition Delineates top and bottom of reservoir
DTS and DTC Geomechanical Attributes
Borehole image Natural fracture network
Rock Properties Organic richness and Gas in place
Hydraulic Frac extent Productivity index
Extensive core in labs and cutting evaluation in labs at wellsite while drilling
Key Parameters
Key downhole logging measurements
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• TOC Measures the present day organic richness of a rock• Empirical relationship to Uranium content• Maturation parameters are indicative of the maximum paleo-
temperature that a source rock has reached• The standard for maturity reporting is Vitrinite Reflectance (% Ro)
Quality TOC (wt%)Poor <0.5Fair 0.5 to 1Good 1 to 2Very good 2 to 4Excellent >4
Vitrinite Reflectance (Ro)
Immature <0.6%Oil Window 0.6-1.1%Wet Gas Window 1.1-1.4%Dry Gas Window 1.4-~3.2%Gas Destruction >~3.2%
Shale As a Reservoir Rock
Ro > 1.5%: This level avoids unfavorable relative permeability effects caused by oil blocking small pore throats and permeability
TOC > 2.0%: This level allows for the generation of abundant gas
GRI Devonian Study: Uranium vs. Kerogen (TOC)
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Characteristics of Shale Units in Different Basins
Cambay K G Cauvery AssamArakan
Vindhyan Gondwana
TOC %1.5-4.0 1.2-
23.00.31-4.76 2.5-6.2 0.60-6.04 4.00->10
Vro%0.53-0.85 0.35-
1.300.34-1.15 0.57-1.94 No data 0.40-1.20
Thickness in Meters 400-
>1500500-1800
200-1100 800-1200 75-320 150-900
K erogenType II & I I I I I & I I I I I & I I I I I & I I I I I I I I I
Prognosticated Resource Potential (Tcf)
217 280 80 55 Not known
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The Shale’s of India
Source Oil & Maritine Journal by Dr. V.K. Rao
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• In addition to Knowledge of TOC and RO….favorable Reservoir Properties must be present:– Porosity > 3%– High reservoir pressure
• Pack in more gas• Keep fractures open
– Favorable In Situ Stress• Influences the permeability and the response to
hydraulic fracturing• Understanding the mineralogy is essential to understand
brittleness
Shale As a Reservoir Rock
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Identification of Ductile Zones from Mineralogy
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Initiation of a frac proved unsuccessful in this zone with >50% claysClays
1 sample per 20’
MINERALOGYQuartzCarbonatesClaysOthers
TPH / TOC (0-10)S1S2TOC
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Events located by horizontal and vertical arrays.
Treatment Well 8-12
Treatment and Observation Well 1-12
Treatment Well 16-1
Microseismic
…….to Improve Frac Program Design
Understanding Fracture Growth…..
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• Second most important item next to establishing core area
• Need relentless pursuit of efficiencies and cost reductions
• Shale plays will require thousands of wells drilled over decades
• Must first establish the most efficient manufacturing design
• Early attention to best practices, appropriate to the specific shale play and emphasis on continuous learning are key
• Development of effective multidisciplinary teams
Continuous Learning
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Summary• Variability of shale is a fundamental controlling
factor on weather a shale deposit will produce economic quantities of natural gas.
• Variations within a shale deposit will determine the core area of a shale play and thus the value assigned to different locations within a shale play.
• Following a process of “Good Science” allows for “Good Engineering” throughout the various stages of a shale project.
• Continuous learning and refinement is a must in order to maintain economic viability.
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Questions
???