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Cele mai bune practici în fracturarea hidraulicăDr. Will Fleckenstein, PE

Profesor adjunct BPŞcoala de mine din Colorado

13 martie 2012

D E P A R T A M E N T U L D E I N G I N E R I E P E T R O L I E R Ă

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Shale Development (with “fracking”)Western Interstate Energy Board Webinar

Dr. Will Fleckenstein, PEBP Adjunct Professor

Colorado School of Mines

September 11, 2012

P E T R O L E U M E N G I N E E R I N G D E P A R T M E N T

Important Shale Development Topics

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1. Drilling• Modern horizontal drilling began in 1990, with the widespread acceptance of MWD

(Measurement While Drilling) to steer the wellbore horizontally. • This allowed the experimentation in the Barnett Shale by George Mitchell, resulting

in horizontal laterals, coupled with multi-stage fracturing, to develop shales

2. Casing• The curvature of wellbore meant that the casing had to curve also, resulting in

connections designed to withstand the torque and drag of a horizontal well• The casing many times has to be rotated to bottom, driving the acceptance of top

drives on rigs, and special tools to facilitate this rotation

3. Cementing and Isolation• Special tools and cements were developed to cement these wellbores, including

expandable liner hangers and inflatable packers.• “Swellable” packers were developed to isolate fracturing treatments.

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2009

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The shale plays are widespread

Occur anywhere conventional production

exists

In the United States, it is a mad exploration rushWhere is the next Shale discovery???

How do you drill and complete these shales?

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Tremendous Amount of Experience Drilling and Completing Horizontal Wells in the United States

Breakout Information This Week +/- Last Week +/- Year Ago

Oil 1419 11 1408 355 1064 Gas 473 -13 486 --422 895

Miscellaneous 2 -2 4 -7 9

Directional 219 -1 220 -19 238 Horizontal 1149 -10 1159 13 1136

Vertical 526 7 519 -68 594

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Currently 1149 rigs are drilling horizontal wells in USA

More than twice as many rigs drilling horizontally than vertically

The experimentation on how to drill shale wells has been done in the US

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1000% Increase in horizontal rigs

Vertical vs. Horizontal Drilling

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1-4000 mdeep

300-3000 mlong

3-10 deg/30 mcurvature

Fracturestimulation

HorizontalWell

VerticalWell

Vertical vs. Horizontal Drilling

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Each horizontal replacesMany vertical wells

How do we drill a horizontal well?

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Change direction by rotating bit with a downhole motor, or a rotary steerable system – deflect the bit

Controlled curvature

Controlled direction

No drill string rotation

Geosteer with respect to rock

Mud motor

Bit

How do we drill a horizontal well?

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Drill straight by rotating the drill string, so that the bit is never pointed in a single direction

Maintain direction of the bit

Rotary steerable or mud motor system

Drill string rotation may or may not be necessary

Mud motorBit

Directional well possibilities

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Production Zone

S-Shaped Well Slant Well

Horizontal Well

Re-entry

Short Radius

Key to drilling multiple wellson a single location

Horizontal Drilling Project by Dr. Fleckenstein

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Six complicated wells drilled from a single surface location in California

Colorado wellsite

Well Construction and Surface Disruption

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Drilling rigs are very large and result in 150 direct and indirect jobs per rig.

The drilling rig needs good roads, bridges etc. to move. The best rig move is to not move very far, but to drill multiple wells from 1 location.

Proper well siting allows multiple wells to be drilled from the same location.

The drilling rig “walks”from well to the next, minimizing time, costs and allowing the least surface disruption

Surface Casing

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1. The hole is drilled for the first string of casing.2. The casing is then cemented in the wellbore

to the surface.Surface Casing Purpose1. Protect Surface water2. Anchor BOPE3. Support casing strings4. Well Control

Cementing Process

How do we cement a horizontal well?

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Shallow Aquifer Protection in General

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To protect surface water

1000’s of meters of rock formations between

producing shale and surface waters

Cemented surface casing

Cemented production casing

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What Should be Done Prior to Horizontal Drilling?

1. Establish a baseline of potential contaminants in aquifers

– Natural gas– Natural dissolved solids– Identification of pre-existing pollution

2. Identify barriers to hydraulic frac growth in the reservoir

3. Construct a reservoir model, including mechanical properties of rocks, identification of natural fractures, amount and type of hydrocarbons

4. Water sources and disposal5. Logistics

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Why do Baseline Testing?

Explosive Methane Gas Found in Some N.Y. Wells Stephanie Pappas, LiveScience Senior Writer Date: 04 September 2012 Time: 12:44 PM ET

About 9 percent of New York state water wells contain enough dissolved methane to require monitoring and other safety measures, according to a new study.

The research tested more than 200 wells used for drinking water across the state for the explosive gas, which is naturally occurring but can be dangerous if ignited. In 2 percent of wells, methane levels were so high that the gas needed to be vented off to avoid potential detonation.

"The research is important because it raises the awareness of the natural quality of people's drinking water," study leader William Kappel, a hydrologist with the U.S. Geological Survey (USGS), said in a statement. "Well owners should work with local health departments to understand the quality of their drinking water to know if methane or other chemicals are present."

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Stimulating a Horizontal Shale Well

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1-4000 mdeep

300-3000 mlong

Fracturestimulation

HorizontalWell

VerticalWell

Fracturing animation

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3 Key Elements of Horizontal Fracturing

1. Water fracs2. Microseismic Mapping3. Mechanical Isolation

Water Frac Fluids

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What is a Shale?

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“milliDarcy”~0.1 to 10,000 mD

“microDarcy”~0.001 to 0.1 mD

“nanoDarcy”~0.000,010 to 0.001 mD

Now we are trying to producethis shale that is ~1000 times

less permeable than tight sands.

And a million times lesspermeable than conventional

Sands.

Courtesy, Mike Vincent, consultant

What about Vertical Heterogeneity?

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ShalesSilty ShalesMudstonesSilt StonesSandy laminations

What a mess!!But they all may produce!!!

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Determination of Fracture Barriers

Most induced fractures are vertical and are driven toward lower horizontal stress.

For instance a fracture growing in A4 will have a difficult time breaking across

the shale above, which is higher stress (in red), and instead will move to the lower stress and stay in zone.

To predict where the fracture goes, you must predict what the stresses are, and for this, you need to know what the rock properties are

The rock properties, such as Poisson’s ratio and Young’s Modulus, must be determined from cores or logs.

higher stress.

lower stress.

Natural Fracture Networks Are a Key

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Microseismic Improves Diagnostics

• Maps the fracture growth• Identifies azimuth• Measures frack distance

from aquifer• Requires observation well

Microseismic

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Microseismic Barnett Shale Horizontal

Side View Plane View

Barnett Microseismic Fracture Heights vs. Deepest Aquifer

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SPE 145949

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Green Completions

Green completions take place during the clean-up stage of the completion, after a well has been “fracked.”

The clean-up involves removing the water necessary to frack the well. During this flow back, natural gas is produced with the water.

What makes the well completion “green,” or environmentally friendly, is that the gas is separated from the water and placed in a pipeline instead of being released to the atmosphere.

Green completions have been Devon’s standard practice in the Barnett Shale since 2004.

Devon has reduced methane emissions by more than 25 billion cubic feet in the Barnett Shale area of north Texas during 2,000 green completions.

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Green Completions

First, a sand separator (shown at right in this photo) filters out any sand, sending it through a 2-inch pipe into the disposal tank. That filtering leaves a mixture of natural gas and water.

The second piece of equipment (in the left side of this photo) separates the water, which then reunites with the sand in the disposal tank.

The gas, meanwhile, is diverted into a separate pipe and eventually is sent by pipeline to a processing plant.

The key to the green completion is that a pipeline must be available for immediate usage.

Shales May Have Gas, Wet Gas, or Oil

Eagleford Trend, South Texas (Source – EOG)

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Marcellus Case History

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Marcellus Microseismic Fracture Heights vs. Deepest Aquifer

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SPE 145949

Impact of 100 Rigs on Marcellus Gas Production

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3 BCFPD – 3 years(500,000 BOPDEquivalent)

Natural Gas Cheap Compared to Oil, Driven by Shale Gas Production

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Crude oilprices

Natural Gasequivalent

prices

The shale plays are widely separated, with different geologic properties, but they have one uniform effect:

They are driving down natural gas prices in the US

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Effectiveness of Groundwater Protection

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Over the past 60 years, more than one million U.S. wells have been safely produced in the U.S. using hydraulic fracturing.

“After review of DEP's complaint database and interviews with regional staff that investigate groundwater contamination related to oil and gas activities, no groundwater pollution or disruption of underground sources of drinking water has been attributed to hydraulic fracturing of deep gas formations.” -

Joseph J. Lee, Jr Pennsylvania Department of Environmental Protection, June 2009

“Though hydraulic fracturing has been used for over 50 years in Texas, our records do not indicate a single documented contamination case associated with hydraulic fracturing.”

Victor G. Carrillo, Chairman Railroad Commission of Texas, May 2009

To the knowledge of the Colorado Oil and Gas Conservation Commission staff, there has been no verified instance of harm to groundwater caused by hydraulic fracturing in Colorado.

David Neslin, Director, Colorado Oil and Gas Conservation Commission, June 2009