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An Overview of the Hydraulic Fracking (HF) Process and Related Properties

Khalid Farrag, Ph.D., P.E. Gas Technology Institute Khalid.farrag@gastechnology.org

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Presentation Overview

1. Overview of the HF Process, 2. Terminologies Associated with HF, 3. Reservoir Properties Associated with HF, 4. Hydraulic Fracture Fluid Properties, 5. Produced Water from HF Production, 6. Gas Emission from HF Production, 7. Seismic Effect of HF Water Storage.

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1) Overview of the HF Process

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1) Overview of the HF Process

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2) Terminologies Associated with HF

For HF water management, related terminology is in: API Guidance document HF2, Water Management Associated with Hydraulic Fracking, June 2010.

Related ASTM water management is in: ASTM D1129 Standard Terminology Relating to Water (Committee D19 on Water).

Need: Correlate HF industry terminology with current ASTM terminologies.

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2.1 aquifer A subsurface formation that is sufficiently permeable to conduct groundwater and to yield economically significant quantities of water to wells and springs. 2.2 basin A closed geologic structure in which the beds dip toward a central location; the youngest rocks are at the center of a basin and are partly or completely ringed by progressively older rocks. 2.3 casing Steel piping positioned in a wellbore and cemented in place to prevent the soil or rock from caving in. It also serves to isolate fluids, such as water, gas, and oil, from the surrounding geologic formations. 2.4 coal bed methane/coal bed natural gas CBM/CBNG A clean-burning natural gas found deep inside and around coal seams. The gas has an affinity to coal and is held in place by pressure from groundwater. CBNG is produced by drilling a wellbore into the coal seam(s), pumping out large volumes of groundwater to reduce the hydrostatic pressure, allowing the gas to dissociate from the coal and flow to the surface. 2.5 completion The activities and methods to prepare a well for production and following drilling. Includes installation of equipment for production from a gas well. 2.6 disposal well A well which injects produced water into an underground formation for disposal. 2.7 directional drilling The technique of drilling at an angle from a surface location to reach a target formation not located directly underneath the well pad.

* From: Water Management Associated with Hydraulic Fracturing, API HF2, June 2010.

2) Terminologies Associated with HF

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Natural Fracture geometry (simple, complex) Rock Hardness, Young's Modulus, Stress Anisotropy, Poisson's ratio, Mineralogy (Quartz, Clay, Calcite, ...), Total organic Carbon (TOC).

Rock mapping tools: Micro-seismic Fracture Mapping, Borehole Imaging Logs, Sonic Scanner Logs, Production histories, Mud Logs.

3) Reservoir Properties Associated with HF

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4) Hydraulic Fracture Fluid Properties

Creates the fracture and suspends the proppant Commonly water based fluid (with linear gel)

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Fluid Components : Gelling agents, Cross linkers, Gel stabilizers, Buffers (control the pH), Breakers (degrade gel fluid to near base fluid viscosity), Surfactants (disperse additives, reduce surface tension), Biocides, Clay control additives (minimizes permeability impairment), Scale inhibitors, other. Proppant Properties: Viscosity (controls fracture width), Density (controls hydrostatic gradient), pH, Friction (controls surface pressure and injection rate).

4) Hydraulic Fracture Fluid Properties

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Fracture Fluid Quality Control Source Water Analysis: pH, iron (<10 PPM), Carbonate

(< 300 PPM), Bacteria (none), Proppants Specifications: API RP56, API RP60, ISO

13503-2 Sand properties: Grain Size distribution, Sphericity,

roundness.

4) Hydraulic Fracture Fluid Properties

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5) Produced Water from HF Production

Source: Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources, EPA/600/R-11/122, November 2011.

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Produced water is water that is brought to the surface along with oil or gas during HF production.

Typically 2-5 million gallons of water are used to fracture one horizontal well in a shale formation.

Not all fracturing fluids injected during HF are recovered. About 10-50 % is collected as a flow back.

Test methods use EPA SW-846: Test Methods for Evaluating Solid Waste, Physical/Chemical Methods, APHA and AWWA Standard Methods (SM), and EPA Methods for Chemical Analysis of Water and Wastes (MCAWW).

5) Produced Water from HF Production

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5) Produced Water from HF Production

* From: Sampling and Analysis of Water Streams Associated with the Development of Marcellus Shale Gas, Gas Technology Institute, 2009

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6) Gas Emission from HF Production

Source: EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990 – 2009, April, 2011.

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6) Gas Emission from HF Production

Well-installation activities (drilling, fracking, etc.) are more short-term and don’t factor in chronic risk analysis.

HF activities can be a source of methane, nitrogen oxide (NOx), carbon monoxide (CO) and hazardous air pollutant (HAP) emissions.

Air quality tests at HF sites focuses on Methane (CH4) and to a smaller extent: Carbonyl, Ozone, Nitrogen Dioxide (Nox), CO, particulates matter (PM), Hydrogen sulfide (H2S), and VOC’s.

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7) Seismic effect of HF Water Disposal

[*] Induced Seismicity Potential in Energy Technologies, Committee on Induced Seismicity Potential in Energy Technologies, the National Academy of Science, 2012.

Felt Induced Seismic Events Related to Energy Technology in the U.S. [*]