George King: Things to Do Before You Frac that Old Well
Things To Do Before You Frac
That Old Well
George E. King, P.E.
Presented at the Sipes/API Continuing Education Seminar, “Old Field
Revitalization”, Houston Texas, August 25, 2015.
Era of Construction – Technology in Practice
Pollution potential & risk are functions of
technology & maintenance in practice over time.
1905 vs. 2015
9 hp., 25 mph and every
practical safety device
known to man in 1905.
640 hp., 200 mph and every practical
safety device known to man in 2015.
Well Integrity Course
Old well behavior doesn’t necessarily describe new well behavior.
Today’s Engineered Fracs and Your “Old” Well
1. What’s in your well integrity? – Have a “no surprise” policy.
2. Fracture Initiation Points – Don’t waste money on what won’t flow.
3. Fracture Design – pressure, rate, proppant and CHEMICALS!
4. Flowback – what’s in it for you?
Well Integrity – The Obvious and The Hidden
• Your well was once strong – is it still?
• How good was your cement job? – TOC, displacement, centralization..
• Have channels developed behind pipe?
• Sections of cement can sometimes be destroyed by multi-fracturing.
• Has corrosion weakened your pipe and cement?
• Wear points in the casing?
• What can you expect your well to do during a frac?
Is it related to a barrier
failure or a well
Is it prevented by
another step such as
What should happen
in a design to prevent
Erosion & Corrosion – at the coupling
• Gap at coupling
upset in the
that serves as a
• The disturbance
lasts for 8 to
be in top
• Many different types of threads – can
rely on mechanical seal(s) or thread
dope, depending on the pipe thread
• Many older connections, such as API and
buttress threads were selected for
availability or strength, but are difficult to
seal gas tight. These threads can be
subject to small leaks if the pipe dope
• Patented threads, with much better
elastomer and metal-to-metal seals, are
available for situations requiring seals.
8Well Integrity Course10/6/2015
Severe pressure cycling may crack cement
Small time Interval, and pressure swing
10/6/2015 Well Integrity Course 9
1,000 psi pressure swing
Both examples had sleeve type confining of 15,000 psi
Caution – this
test is not
found in a well
Is this a problem?
Older well cements may
require investigation and
The Best “Tool” for Evaluating Cement Quality is the Pump Chart
1 Filling surface equipment w/ fresh water
2 Pressure test – two leaks in surface connection & a successful test
3 Pump spacer to separate mud from cement
4 Constant density spacer and early batch mixed cement
5 Shut down to drop bottom plug & switch to on-the-fly cement
6 Pumping cement – within density guidelines, but barely.
7 Cement free-fall – heavier cement pushes mud faster than pump in.
8 Cement density variance – was a special tail-in slurry used?
9 Shut-down to flush surface lines and drop the solid top plug.
10 Bottom plug lands, diaphragm ruptures & cement into annulus.
11 Free-fall make up – more flow in than out - pressures equalizing
12 Cement lift pressure too low – check return volumes and timing.
13 Top plug “bumps” (lands in the shoe track) – placement complete.
14 Hold back pressure on casing if float valve fails. (not in this case).
Open Annulus and Open Shoe.
Still a viable completion?
Well Type Influence – Change in Well USE from original Design or Use
is identified as a higher risk.
Barrier type, number & construction method vary w/ well type.
Well age is important, but secondary to:
1. Era of construction – what technologies were used?
2. Care with which a well is constructed.
3. Culture of maintenance.
Fracturing - Initiation Points & Ten Things I’ve Learned:
1. All parts of the formation are not created equal.
2. All parts of the formation are not filled/charged equally.
3. There are preferential flow paths through the formation – some help – some hurt.
4. Some flow paths connect with water, some don’t.
5. Some of best hints on flow will come from drilling, logs, offsets & a lot of study.
6. Unconventional formations different from conventional formations.
7. What produces at surface may not describe what’s in the formation.
8. Insitu stresses, mineralogy & post-depositional changes shape recovery potential.
9. There are reasons that oil declines faster than gas – some can be fixed.
10. New technologies can sometimes help if you understand what needs to be fixed.
Look for the Gas Shows
•Ratio of gasses
•Other logs (CNL, Density) to help
•Density for Brittleness
•Resistivity for water saturation and
•ROP (rate of penetration)
•Is it a hot shale or a natural fracture?
The objective is to align the
perf clusters with natural
• This isn’t the fracture job of the 50’s, 60’s, 70’s, 80’s or 90’s and it has
changed a lot since 2008.
• The formation directs the frac – you just pump it, However….
• How you pump the frac makes a difference in how well it works.
• Surface Injection Rate Application can keep you in zone.
• Frac growth related to rate, pressure and proppant – different for each well
• What goes in the fracture treatment has changed:
• Surface and fluid modification.
• Chemicals with EOR-style character.
• Volume of proppant makes a difference.
• Frac gradient is usually 0.65 psi/ft to 0.85+ psi/ft.
usually spikes and
drops back at the frac
Acid, ball sealers, XGL,
and other operations
may be necessary to
more to frac
This job was slowly
ramped up to develop
natural fractures and
Flowback – don’t ignore it anymore…..
• Proppant flowback control.
• Potential for destroying the frac-to-wellbore connection.
• May shut-in reduce frac water return – does it help or hurt?
• Formation sensitive – may not have much effect in some places
• Can reduce disposal volumes in some cases.
• Possibly can improve recovery.
• What can it tell you?
• Complex or planar fracturing.
• Where your frac water has been.
• What your frac water is reacting with.
• Look at your well stock closely.
• For what specific reasons would a refrac be beneficial?
• Skipped pay.
• Poor initial frac.
• Declining production with stable pressure.
• Repaired well with residual damage.
• Can the refrac be done economically?
• Is Well Integrity acceptable?
• What can you learn from a refrac that would make a refrac more economical?