risk management best practices for oil & gas operations using

Risk Management Best Practices for Oil & Gas Operations Using

Hydraulic Fracturing

Robert W. Puls, Ph.D. Director, Oklahoma Water Survey

University of Oklahoma

Protection versus Restoration

Restoration of contaminated ground water is at best difficult and in many cases, impossible

Depends on scale of impact, extent and type of contamination

Cleanups generally take years and are often unsuccessful

An ounce of protection is worth a ton of cure

OR

lets not mess it up to begin with

Potential Risk Pathways

Mismanagement of wastewaters on surface Pit leaks, spills, recycling operations, transport, disposal

Inadequate well construction Poor cement job, insufficient casing, inadequate casing

Migration of frac fluids to abandoned wells

Migration of frac fluids to nearby USDWs

What About Methane?

Occurs naturally in both thermogenic and biogenic forms

Lighter than air, explosive (5-15% in air), not regulated in water

Increased removal efficiency from water with increased temperature and decreased pressure This happens when recovering sample from deep in subsurface

Potentially mobilized via production well drilling (vibrations, pressure pulses)

Increased turbidity often coincides with presence of methane in water

Analysis for methane in water typically underestimates concentration due to sampling artifacts

What About Methane?

Failure of the cement or casing surrounding the wellbore poses a risk to water supplies. If the annulus is improperly sealed, methane, other gases, fracturing fluids, can access drinking water aquifers.

e.g. Bainbridge, OH; Dimock, PA

Methane Treatment

Conventional treatment at point of use

Venting works if concentrations low Chlorination (bacteria from oxidation) Filtration (increased turbidity, Fe, Mn oxidation) Non-trivial Can be xpensive High maintenance

Alternatives ?? DON’T ADD ANY MORE TO THE GROUND WATER

Analysis of Reports of ‘Suspected Water Resource Impairments’

from Hydraulic Fracturing

40 sites/locations 10 different states in U.S. 28 sites in shale formations (5 different plays) 8 in tight sands; 4 in coal bed methane

Summary of findings for 40 sites of “reported suspected incidents”

0

5

10

15

20

Number of Incidents

The most significant risks to water resources are surface wastewater management, wastewater disposal

and well construction

Risk Management Practices to Protect Water Resources

Site Selection and Pad and Well Construction

Production Well Completion

(Hydraulic Fracturing)

Wastewater Management and Well Closure

Conductorcasing

Surfacecasing

Productioncasing

Cement

Productiontubing

Cement

Cement

Bold lines are pipes

Surface

Aquifer

Hydrocarbon-bearing formation

1,000

2,000

3,000

4,000

5,000

6,000

7,000feet

Wellhead

Risk Management Practices: Site Selection, Pad and Well Construction

Engage and communicate with local authorities and the public in advance (town hall meetings)

Site characterization to determine existing abandoned wells, natural fractures, faults, location of base of drinking water aquifer, existing shallow natural gas zones

Use closed loop systems if at all possible; if not, properly line pits and segregate and test drilling muds


Select pad locations away from surface water bodies and source water protection areas (set back distances)

Use physical containment on site to protect against runoff, spills, blowouts etc. Silt fences, berms, liners under the pad, swales to collect and direct runoff

Identify source water locations Evaluate competing uses of source water, time of withdrawals, alternative water sources (marginal waters)


Sample water wells (springs) in immediate area to

determine baseline water quality

Use tanks as opposed to pits where possible for storage of wastewaters (flowback, produced water)

Have monitoring systems and methods in place prior to well construction and equipment mobilization

Verify well integrity (CBL, VDL, pressure tests)

Potential Monitoring Parameters for Baseline Sampling Program

Sampling Private Wells

Clarify/determine objectives of sampling Communicate with well owner, water usage patterns, volumes, recent

usage (24hrs) before sampling Collect data on water supply system volume (well bore, pressure tank,

pipes, water softener etc.) and evaluate local/regional water quality variability

Purging Do not overpurge and evacuate well Remove at least 1 water supply system volume, but use pH, temp, and

specific conductance to look for stabilization to begin sampling

Risk Management Practices: Production Well Completion (Hydraulic

Fracturing)

Continuously monitor on site equipment, all water transmission lines, piping

Limit fresh water usage (recycle, alternative sources) Disclose chemicals to the public Use ‘green frac’ fluids FracFocus

Track chemical usage

Chemical Usage

The number of chemicals used is decreasing

The toxicity of the chemicals used is decreasing Drivers: environmental concerns, costs, better

understanding of chemical effectiveness and performance

Fracturing Fluid Composition Example From FracFocus 2011

Component Ingredient Purpose Percent Composition by mass

Water Fresh water Deliver proppant 87.4

Recycled Water Produced water Deliver proppant 3.2

Proppant Sand Keep fractures open 8.8

Acid HCl Dissolve minerals, initiate cracks

0.5

Friction reducer Polyacrilimide, petroleum distillate

Minimize friction between pipe and fluid

0.1

Iron control Citic acid Prevent precipitation of metal oxides

0.01

Corrosion inhibitor Ethylene glycol, dimethyl formamide, decanol, isopropanol, octanol, 2-butoxyethanol

Prevent pipe corrosion 0.002

Biocide Quaternary ammonium, ethanol, glutaaldehyde

Eliminate bacteria 0.006

Scale inhibitor Methanol Prevent scale deposits in pipe

0.001


Fracturing)

Continuous monitoring of down hole, annulus, wellhead pressures

Real-time monitoring of treatment progression Use tanks for ‘clean water’, chemicals, flowback

Pavilion, WY

Pits (33) as source of contamination

Hydraulic fracturing in/near a drinking water aquifer probably not a good idea

Surface casing must extend below sources of drinking water

Pavilion Draft Report, EPA, Dec 8, 2011


Fracturing)

Do not frac in or immediately adjacent to a USDW

Have contingency plans for ‘accidents’ Blowouts happen (recent ones in PA, ND, WVA)

Risk Management Practices: Wastewater Management & Well Closure

Recycle flowback to the extent possible On-site treatment - evaluate Dispose of any residuals in approved manner Minimize release of natural gas and condensate


Maintain secondary containment around all tanks

and wellhead Minimize air emissions from compressors,

dehydrators, tanks, well valves Routine monitoring of site Well head pressures


Shut-in well during non-producing periods Plug well at closure with materials optimized for local

hydrogeology – cements, bentonite – and verify plugging

Site reclamation back to native vegetation and natural contours

Communication, public engagement

Research Needs Continued development of recycling and alternative water sources

to minimize water usage

Cement formulations for increased pressures, longer life

Better understanding of microbiology of deep subsurface and produced waters

Continued development of ‘green chemicals’ for hydraulic fracturing

Better sampling method for methane in water

Study on health effects of long term exposure to methane (ethane, propane) in drinking water – do we have enough information?

risk management best practices for oil & gas operations using

Documents