NEW SHALE WELL STIMULATION SYSTEM

DR. WILLIAM MAURER

Maurer Engineering Inc

Austin, TX

January 1, 2016

Use FULL SCREEN or SLIDE SHOW for better viewing

SHALE WELL WITH MULTIPLE FRACS

Problems with Shale Fracs & Refracs

•10 to 15 percent of fracs are non productive

• Near-wellbore damage initially reduces flow rates reduced 20 to 30 percent

• Wells Decline 50% first year and 70% after second year

• Refracing stimulates less than 50% of fracs in many wells

• Refracing is expensive and not reliable

Natural Fractures in Shale

Lateral Heterogeneity (macro scale)?

• If natural fissures are a significant component of fluid

flow in the formation… How are they distributed?

Can we avoid damaging them?

Single PlaneHC expulsion fissures

lacking well-developed

conjugate set (Leigh

Price, Bakken)

Conjugatelike we envision in CBM (face

and butt cleats) or Barnett

Shale

SwarmsSPE82212

James LimeVINCENT 2010A

Oil is Produced Through Voids in the Shale Not Natural Fractures

• At 10,000 feet depth, the vertical rock stress = 10,000 psi and the horizontal stress = 4000 psi

• These high rock stresses close all natural fractures in shale

• The natural fractures cannot be propped open because of their small width and proppant embedment

• Oil is therefore produced through voids which remain open under high stresses

10,000 PSI

4,000 PSI

PSI

NATURAL FRACTURES VOID SPACE

Void Spaces in Shale

Eagle Ford

Pearsall Shale, S. TX (Loucks, 2010)

Eagle Ford, Ingrain IncAlbany, Ingrain Inc

Haynesville, Loucks, 2010

Haynesville, E.TX (Ingrain) From Loucks, et al, GCAGS, April 2010

Eagle Ford, Ingrain Inc

Oil flow is through pore

void spaces in shale

EAGLE FORD SHALE

(WALLS AND SINCLAIR, 2011)

1000m nD = 1 mD

EAGLE FORD SHALE POROSITY IS UP TO 12 PERCENT AND

PERMEABILITY IS UP TO 100 mD

Eagle Ford Shale Outcrop

Eagle Ford fracs are typically 50 to 200 feet high

This shows layering that provides horizontal permeability to carry oil and gas to fracs

High cliff indicates Eagle Ford strong shale

Factors Causing Near-Wellbore Damage

FRAC PLUGGING IS NOT MAJOR PROBLEM WITH VERTICAL WELLS

Laminar flow

• Long Inflow area into fraced vertical wells reduces frac plugging

iInflow

50 FT

1000 ft

Vertical

Well

FLOW CONVERGES TO WELLBORE IN SHALE FRACS

0.5 Ft

Turbulent Flow

(p = kV^2)

Laminar Flow

(p = kV)

As oil approaches the horizontal, the flow converges from 50 to 0.5 feet, increasing oil

velocity 100 fold.

This increases turbulent pressure drop by a factor of 100 x 100 = 10,000 fold

This is a major cause of the constriction zone at the wellbore

iInflow

HORIZONTAL

WELL

50 FT

1000 ft

PLUGGING IN MAIN PART OF FRAC NOT A PROBLEM

0.5 Ft

Turbulent Flow

Laminar Flow

• Plugs in the tall part of frac have little effect because oil or gas flow

around them with minimum pressure drop

iInflow

Horizontal

Well

50 FT

1000 ft

PLUGS

FRAC PLUGGING IS A MAJOR PROBLEM NEAR HORIZONTAL WELL

10 ft

Diameter

Turbulent Flow

Laminar Flow

Only 0.425 cu ft of crushed proppant fines will fill and plug a 10 ft diameter damaged zone

around the horizontal well.

This explains why 10 to 30 percent of shale frac stages are non-producing

iInflow

DAMAGED

ZONE

50 FT

1000 ft

Only 3.18 Gallons of Crushed Proppant Fines Will Plug Large Fracs

DAMAGE ZONE DIAMETER = 10 FT

FINES VOLUME REQUIRED TO FILL VOID SPACE WITHIN 10 FEET OF HWELL =

PI *5^2 *0.26*(.25/12) = 0.425 CU FT VOID SPACE = 3.18 GALLONS

THIS SMALL VOLUME IS WHY FRAC PLUGGING IS A MAJOR PROBLEM NEAR THE WELLBORE

FRAC THICKNESS = 0.25 INCH

PROPPANT VOID VOLUME = 26 PERCENT

NEAR-WELLBORE CONSTRICTION ZONE

Multiple Small Fracs Initiate Parallel to Wellbore

Daneshy, 2011

SPE 140134

THIS IS CAUSED BY FRAC PRESSURE CHANGING THE STRESS STATE IN THE ROCK

Casing

σmax

σmax

Perfsσmin

σmin

Frac Propagation from Wellbore (Daneshy, 2011)

Fracture

THE FRACS ROTATE UNTIL THEY ARE PERPENDICULAR TO THE HORIZONTAL WELL

Frac Rotation Near Wellbore

(Maurer)

Minimum

Stress

LARGE FRACHorizontal

Well

Microfractures

Rotate 90 degrees

In 5 to 10 feet

Form Constriction Zone

Perforations

The small fracs rotate 90 degrees as they propagate from the wellbore and coalesce into one large

frac a few feet from the well

This creates a constriction zone near the wellbore that reduces flow rates 20 to 30 percent initially

and then continues to plug more as the well is produced

Near-Wellbore Damage Zone After Fracing

(Maurer)

(30% Flow Rate Reduction)

5 to10 Foot Radius Damaged Zone

Flow Restrictions

High Flow Velocities

Perforations

Fracture Initiation

High Pressure Drops

Fracture Plugging

OIL OR GAS Flow

FRAC

Horizontal well

New Shale Well Condition When First Put onto Production

(30% flow reduction due to near wellbore damage)

CONSTRICTION ZONE

30%

OIL OR GAS Flow

FRAC

Horizontal well

NATURAL FRACTURES

System Needed to Eliminate near Wellbore Damage

Well Condition After Two Years

(70 % flow reduction – Uneconomical)

CONSTRICTION ZONE

(Gets Worse With Time)

70%

OIL OR GAS Flow

FRAC

Horizontal well

NATURAL FRACTURES

PROPPANT & FORMATION FINES

DECLINE DUE TO CONSTRICTION CONTINUING TO PLUG AS WELL IS PRODUCED

The Right Approach Can Counter The Effects of Near-Wellbore Damage(Jeremy Viscomi, The American Oil and Gas Reporter, November, 2015)

“Just about every well, at one time or another, is going to suffer the effects of wellbore

damage. Near-wellbore damage generally is defined as any restriction to flow capacity.

These restrictions often are caused by a reduction in near-wellbore permeability, most

often from perforating debris or mud filtrate caused by the drilling process.

Not surprisingly, this damage can dramatically impact a well’s overall production.

How an operator or service company chooses to address this issue can dictate over-all

performance over the life of the well.”

George King Comments on Near-wellbore damage (Jeremy Viscomi, The American Oil and Gas Reporter, November, 2015)

“The effect of the damage, the type of damage, severity of plugging, the depth, and the

ability to prevent, remove, or even bypass the damage are all key factors in an operator’s

strategy to address near-wellbore damage.

King asserts that shallow damage is the most common and that it takes a significant

amount of damage to reduce production drastically.

He says the problem is that generally, the highest permeability zones are the easiest to

damage and also are the ones that will cause the greatest reduction in production.

How one approaches cleanup can be a most useful tool in addressing the issue of near-

wellbore damage.”

New Drain Hole Stimulation System(Goal is to Bypass Near-Wellbore Damage Zones)

Drain Holes Bypass Wellbore Damage Zones and Drill Across Fracs

FRAC

DRAIN HOLE

3 TO 4-3/4 INCH

HORIZONTAL WELL

DAMAGE ZONE

OIL

COMPLETED OPEN HOLE

Drain holes provide large flow paths to horizontal well

Drill Long Drainholes to Intersect more Natural Fractures

DRAIN HOLE

3 TO 5 INCH

HORIZONTAL WELL

DAMAGED ZONE

Open hole or slotted drain holes intersect natural fractures and voids in shale

Angled Drainholes to Individually Stimulate Fracs

(Vertical Plane)

FRACS

DRAIN HOLES

HORIZONTAL WELL

DAMAGED ZONES

VERTICAL WELL

OIL

ANGLED DRAINHOLES USEFUL WITH NON-PRODUCTIVE FRACS

OIL

Angled Drainhole Drilled Across Frac Clusters

(Vertical Plane)

FRACS

DRAIN HOLES

(3 to 4-3/4 inch)

HORIZONTAL WELL

DAMAGED ZONES

VERTICAL WELL

OIL

ANGLED DRAIN HOLES TO STIMULATE FRAC CLUSTERS

OIL

Sidetrack Multiple Branches Across Fracs

DRAIN HOLE

3 TO 4-3/4 INCH

HORIZONTAL WELL

DAMAGED ZONE

Improve frac drainage and intersect more natural fractures

Horizontal Drainhole to Stimulate All Fracs in Well

(Vertical Plane)

FRACS

DRAIN HOLE

(3 to 4-3/4 inch)

HORIZONTAL WELL

DAMAGED ZONES

VERTICAL WELL

OIL

OIL

Horizontal Drainholes Drilled From Horizontal Well

(Vertical Plane)

FRACS

DRAIN HOLES

HORIZONTAL WELL

DAMAGED ZONES

VERTICAL WELL

OIL

OIL

OIL

DRILL HORIZONTAL DRAIN HOLES FROM HORIZONTAL WELLS

Drainholes in Vertical plane

FRACS

DRAIN HOLES

HORIZONTAL WELL DAMAGED ZONES

VERTICAL WELL

OIL

OIL

OIL

OIL

DRAIN HOLE DESIGNS FOR DIFFERENT PURPOSES

OIL

Drainholes Drilled in Horizontal Plane

FRACS

DRAIN HOLES

HORIZONTAL WELL

DAMAGED ZONES

VERTICAL

WELL

OIL

DRAINHOLES CAN BE LONGER IN HORIZONTAL PLANE

OIL

DRAINHOLE INDEPENDENT OF FRACED WELL (HEEL TO TOE)

DRAINHOLE INDEPENDENT OF FRACED WELL (TOE TO HEEL)

IMPROVED FLOW WITHIN SHALE DUE TO DRAINHOLES

FRACS

DRAIN HOLE

(3 to 4-3/4 inch)

HORIZONTAL WELL

DAMAGED ZONES

VERTICAL WELL

OIL

OIL

Improved oil flow in shale with drain holes may allow longer frac spacing

Drain Holes Can Be Selectively Fraced if Necessary

ORIGINAL

FRAC

STRADDLE

PACKERSDRAIN HOLE

STIMULATE

EXISTING

FRAC

CREATE

NEW

FRAC

FRAC STRING

NATURAL

FRACTURES

REFRACING OFTEN STIMULATES LESS THAN 50 PERCENT OF FRACS

Remove Drain Holes By Filling Them With Cement

FRACS

DRAIN HOLE FILLED

WITH CEMENT

HORIZONTAL WELL

DAMAGED ZONES

VERTICAL WELL

THIS DOES NOT AFFECT FLOW THROUGH FRACS TO THE HWELL

Application Team

Concept and Patents

Well planning and Drilling Engineers

Instrumentation and

Candidate Well selection

Drain Hole Completions

•Mike Vincent states that the worst thing you can do is cement casing in shale wells

•The drain holes will therefore be completed open hole or with slotted liners

•This will allow oil and gas inflow along their entire lengths

•It will also improve flow within the reservoir so oil or gas can easily flow to adjacent fracs

•This may allow increasing frac spacing 2 to 3 fold and decrease fracing costs significantly

OIL FLOW IN SHALE

• The pressure to push oil though the shale into the frac comes from an expanding gas cap or water

drive.

• Oil flow rate is proportional to the shale permeability and the pressure drop between the fluid

in the shale and in the frac (drawdown pressure)

•.As fracs plug, the pressure in the frac away from the damaged decreases rapidly, causing the rapid

decline in shale wells (50% first year, and 70% the second year)

•Drain holes should never plug (due to their large flow area) so they should completely eliminate the

rapid decline due to frac plugging

•

Major Computer Simulation Problems

Vincent SPE 119143

SOPHISTICATED 3D MODELS OFTEN PRESUME• PLANAR FRACS

• HYDRAULIC CONTINUITY

IMAGE SOURCE SPE 110093

Problems with Frac Models (Vincent, 2010)

Frac models are incorrectly based on planar fracs with uniform conductivity

Frac models incorrectly assume pressure drops in fracs are proportional to

velocity (Laminar flow)

Fluid flow in frac is proportional to velocity squared near wellbore due to high

velocities and turbulent flow

This results in frac models greatly underestimating frac pressure drops near

wellbores

History matching frac curves provide little or no useful information

SPE 119143

PRODUCTION HISTORY MATCHING IS NOT UNIQUE

THE ABOVE PRODUCTION HISTORY CURVES FOR A SHALE WELL WERE IDENTICALLY MATCHED

WITH 50,100 AND 500 FOOT FRACS BY ADJUSTING THE OTHER CONSTANTS

“ACHIEVING A VISUALLY ACCEPTABLE HISTORY MATCH DOES NOT MEAN THAT WE HAVE

UNIQUELY DETERMINED ANYTHING ABOUT THE RESERVOIR OR FRACTURE”, VINCENT, 2010

MAJOR REFRACING PROBLEM

Refracs Stimulate only 50% of Fracs (Kashikar and Jbeil)

June 2015 World Oil

On these two wells using diverters to isolate stages, less than 50% of the stages closest

to the “heel” were stimulated.

“This is a common occurrence where operators must rely on diverters to isolate perf

clusters”

SPINNER FLOW RATE SURVEYS

SPINNER FLOW METER SURVEYS

Spinner flow meter surveys should be used in

new and refraced wells

They give accurate measurements of the flow

from each frac

They provide the information needed for

operators to optimize fracing and refracing

operations

They helped MicroSeismic show that less than 50

percent of fracs are stimulated in many shale

wells

BP Recommends Using Trace Materials To

“Reveal Where the Proppant is placed”

Drain Holes Utilize only Conventional Drilling Equipment

CONVENTIONAL DRILL RIG

COILED TUBING DRILLING (Optional)

Conventional Bent Housing Motor

DRILLS A CURVED HOLE WHEN MOTOR HOUSING NOT ROTATING

AND A STRAIGHT HOLE WHEN MOTOR HOUSING ROTATING

Conventional Rotary SteeringTool

Utilizes intermittent side pads to control direction while motor housing is rotating

Used primarily in long horizontal wells where high borehole friction limits well length

Conventional MWD/LWD Tool

Conventional Side Tracking Tools

SAGD Parallel Drilling System (Optional)

HALLIBURTON.COM

Allows accurate control of spacing between wells

Using Stacked Rigs and Conventional Equipment will Allow Rapid

Implementation of Drain Holes

Eliminating Refracing Will Get Rid of the Following Problems

HIGH PRESSURE PUMPS

ELIMINATE REFACING AND HIGH COST AND LOGISTIC PROBLEMS

HIGH COSTS AND LOGISTICS PROBLEMS

Four Million Pounds of Frac Sand

Four Million Gallons of Water and Waste Water Disposal Problems

SAFETY PROBLEMS

Federal and State Fracing Regulations

Demonstrators

HIGH REFRACING COSTS

$$$$$$“PUMP AND PRAY”

Frac Expert Comments about Drain Holes

Factors Supporting Drain Hole Drilling

1 Reduced frac conductivity identified as major problem

3 Less than 50 percent of fracs are often stimulated by refracing

4 Near wellbore damage causes 50 to 70 percent decline rates

5 5 to10 percent of proppants are crushed in fracs and plug fracs

6 Refracing is very unreliable (“Pump and Pray)”

INDUSTRY FRACING EXPERT COMMENTS

“Many refracing successes are due to increasing frac

conductivity, not stimulating additional natural fractures”

Mike Vincent 2010

Mike Vincent Quotes

“Uneconomic refracs have been performed in almost every reserve type”

“There are myriad conditions that can cause refrac failures, each with its own best resolution”

“Pump and Pray”

Johnson, Kari: “Special Report: “Horizontal Well Operations”, July 2015 The American oil & Gas

Reporter

“Most of the refracs today are done without mechanical isolation, opening all

stages and perforation clusters to fluid flow and pressure simultaneously”

“Diverters are often not effective in isolating frac stages”

“Less than 50 percent of fracs are stimulated during many refracs”

Kashikar and Jbeil, MicroSeismic, Inc

World Oil, June 2015

SCHLUMBERGER EAGLE FORD REFRACING CONSORTIUM

Schlumberger and five Eagle Ford operators formed a refracing consortium in 2014

that set three refracing goals:

1. Increase Stimulated Reservoir Volume

2. Improve the Conductivity of Existing Frac

3. Re-energize a Parent Well before Completing an Infill Well Nearby

Cook, A and Clark, B: “Sequenced Refracing Technology Improves Economics in Unconventional

Plays”, JPT September, 2015

POTENTIAL BENEFITS OF DRAIN HOLE STIMULATION

• Bypass near-wellbore damaged zones and provide large flow paths

• Eliminate costly and troublesome refracing

• Stimulate all fracs at once

• Reduce stimulation costs 50 to 60 percent

• increase flow rates 30 to 70 percent

• Eliminate rapid decline

• Eliminate need to refrac every 2 to 3 years

Sanchez Offset Wells Problem(Kari Johnson, October, 2015)

• “While drilling new offset wells in the Eagle Ford, frac water is produced from all of

the surrounding offset wells for 30 to 60 days and they go back to producing oil and

gas at the previous rates with no loss in reserves”

• Maurer - This shows that there is high permeability within most commercial shale

fields

High Speed Drain Hole Jet Drilling System

(Future)

82

High Pressure Bit

HP

Flo

w

ConventionalCoiled Tubing

High Pressure Motor

Developed High Pressure Jet Drilling System (Maurer Engineering)

10,000 PSI

83

High-Pressure Coil (Med

Tubing Motor

10,000 PSI PDM MOTOR (MEI)

84

10,000 psi

HIGH PRESSURE JET BIT (MEI)

854-3/4 INCH JET DRILLED HOLE – LEUDERS LIMESTONE (MEI)

86

150

300

1600

0

200

400

600

800

1000

1200

1400

1600

1800

Rotary Conventional High Pressure

Dri

llin

g R

ate

High Pressure Jet Drilling Rates(ft/hr) (MEI)

LEUDERS LIMESTONE

THE END wcmaurer@aol.com

512-263-4614

EXTRA SLIDES

OIL FLOW IN SHALE

• Energy and pressure are required to push oil through the pores in the shale

• This energy comes from an expanding gas cap or water drive

• Most shale oil wells are water drive where the pressure in the formation equals that exerted by a column of water to the surface

• Therefore some water is typically water is produced with the oil

• Oil flow (Darcy Flow) is proportional to:

a. The drawdown pressure between the formation and the frac

b. The permeability of the formation

•. The drawdown pressure is decreased by the pressure drop in the frac so frac plugging is very detrimental to oil production

• Most of the rapid decline in shale wells is due to frac plugging near the wellbore decreasing drawdown pressures and flow rates by

50% to 70%

• The drain holes bypass these constriction zones and therefore increase production rates more than refracing

•

•