Janchik R Lost Circulation Solutions for Lime Stones and Induced Fractures

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Lost Circulation Solutions for

Limestones and Induced Fractures

(or any rock type)

Alex Wienzek Product Line Manager

Richard Jachnik Technical Sales Manager

History

• Lost circulation of Drilling Fluids have been experienced

ever since Drilling Fluids were introduced-especially when

drilling porous/fractured and vuggy formations.

• Many types of Lost Circulation Material (LCM) have been

proposed, tried (with little science) and many are still in

use.

• Many technical papers have been written on the subject

and if those concerned with minimising formation damage

through bridging are also considered the list is extensive

indeed

• So what is new regarding both our understanding and

ability to seal natural fractures/vugs in limestones or

induced fractures in various rock types?

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Examples of Fractured Chalks

1 f

t

Tectonic Healed Stylolite-assoc. Discontinuous

f

f

f f

f

f

f

f

Quantification of Losses

• Seepage Loss (<4m3/hr)

• Partial Loss (4 -80 m3/hr)

• Severe Loss (>80 m3 /hr)

• These numbers vary according to author and rounding up from bbl to

m3 ! (In mud man parlance loosing >60 m3 per hour is ~2 pits per

hour! – sufficient!). In 8 ½” hole pumping at 2 m3 per min means

returns at 50% or less.

• Seepage loss is normally loss to porous formations or small

discontinuous fractures – which may be natural or induced

• This type of loss can be cured either with small doses of effective

LCM (possibly using the application of bridging theory with

particulates)


SPE 18022

This seminal paper by Sandia Natl

Labs contains some very useful

information.

Converting to mm - if we look at the

width of the fracture opening (b) at

0.12 in (3.05mm) we see that even

if the particle size diameter is 2mm

the fracture will never plug.

(Multiple particle bridges do not

form with the same material or can

sustain the applied pressure)

For half the fracture width the same

size particle can plug – at only 5

ppb (14.3 kg/m3)

They also showed that when the

particle size was shifted to a larger

size distribution they achieved

better bridging (next slide)


Jamming

• When flakes were mixed with the particulate (rubber) Sandia

achieved even greater effectiveness – this is due to the

morphology of flakes and the ability to randomly orient and jam.

• The use of LC Lube (more elongated morphology than ground

marble) at concentrations of 57 kg/m3 in OBM allowed Brent

sands to be drilled significantly overbalance with pressures

between 3000 and 5400 psi.

• The material has been used successfully at concentrations as

low as 2.85 kg/m3, more often at 15-20 kg/m3 with 100 kg/hr

additions while drilling 8 ½” holes.

• The resiliency of the synthetic graphite is much higher than

solid particulates – this provides an increase in Frac pressure

(wellbore strengthening) and can be used injunction with

marble to lower cost


LC Lube – synthetic graphite

Issues – Larger is better than finer!

• D50 of LC Lube is around 320 microns or 48 mesh

• Initial drilling requires 84/52 mesh screens

• 145/120 mesh can be used once the mud is warm

and fully sheared

• Some losses at the shakers are inevitable

• Finer product is less effective at plugging induced

fractures in Brent sands

25 x25 x

Particle Size Distribution

Mesh Size Micron % Retained

40 425 µm 27

50 300 µm 22

60 250 µm 12

80 180 µm 19

Seepage loss materials

• These by their very nature

of smaller particle size will

not plug large fractures but

can be effective for

seepage loss into porous

formations or into short

drilling/ECD induced

fractures

• So at what fracture width

will they fail?

Fine Mica

Chek-Loss (cellulose

fibre)

Max-Bridge Slot Failure

• Max-Bridge is a

combination formulation of

Soltex or Sulphatrol, Max-

Shield (latex polymer ~1

micron), LC Lube and LC

lube fine designed for

Saudi drilling

• Tested on 200 micron slots

it functioned, but failed on

300 micron (next slide)

Particle Size Distribution

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700

Micron

Perc

en

tag

e

LC Lube Fine

LC Lube

Aquadrill Mud + Max-Bridge + LCM

• Note the addition of various LCM used for seepage loss

and the results!

Increasing the pressure to 900 psi and at 150 F doubled the spurt result for test 4

and 8.

RDIF Mud + Sized marbles

• Note that the addition of extra calcarb particulates failed to

bridge effectively 100 micron slots

TFL= Total Fluid Loss

No Surprise!

• Multiple particle bridges will not form when none of the

particulates has at least a D90 >than the fracture width!


0

10

20

30

40

50

60

70

80

90

100

1 10 100 1000

Cu

mu

lati

ve

%

Diameter (microns)

PSD of Fordacal Grades - 2005 data from supplier

Fordacal 10

Fordacal 30

Fordacal 45

Fordacal 300

Fordacal 200

Fordacal 100

Fordacal 60

Fordacal 25

Fordacal 36

Fordacal 16 max

Fordacal 16 max

but flakes are another story!

Baker-Squeez

This is a recent product introduction

based on a fibrous pill formulation

for loss circulation problems. (See

SPE papers 139817 & 149120).

It is a formulated one sack additive

that can be weighted to 18 ppg

(2.16 sg) and seals both porous

sands, gravels and fractures

The fracture limitation?

From our testing ~1300-1400

micron as it failed at 1500 micron in

WBM and at 1000 micron in OBM

though bridged 800 micron

Useful for overburden drilling.

Convenient and avoids issues of

how much LCM to add, which LCM

to add and in what combination.

Also simplifies rig inventory.

Comparative testing on 1500 micron slots


• Only Formulations C & D bridged but with high fluid loss.

Note E failed with more Nut Plug (the surmise is greater

sphericity in the mix).

So while formulations C & D would have sealed smaller fractures as well as

Baker-Squeez , the formulations are more complex to engineer and liable to

failure.

Solu-Squeez


This material was designed where a degree of solubility in 15% HCl was

desired (>90%) and seals up to ~700 micron slots – although this could be

extended with Soluflake

What can bridge above 3000 micron? 10 mm?

We can successfully bridge in the

laboratory apertures up to 8 mm

wide with Soluflake and calcarb

blends. Holes appear slightly easier

to bridge than these apertures.

The concentration of additives is

now such coupled with the large

size of the coarse materials that

these slurries cannot be pumped

through tools or small nozzles and

are best displaced/squeezed open

ended.

The point is approached where

either losses are lived with, or a

lower fluid density is used such as

air drilling if this is possible.

Alternative techniques such as

pressured mud cap drilling or

variants can also be used in some

circumstances.


Sufficient material to Jam

• While not optimised for coarse material

dose Table 4 data shows that even a

high concentration of flaked and

particulate materials can fail to bridge.

• This and other data goes someway to

explain the cases where LCM pills have

failed. They just do not have sufficient

coarse flaky or fibrous material to enable

multiple bridges to form.

• Bridges will form on 8 mm apertures with

150 ppb material blend (428 kg/m3)

• Largest particulate size can be < than

actual aperture width provided there are

enough other large flakes/smaller

particulates to help bridge


Solu-Flake D

This is a recent addition to our

flaked Calcium carbonate line. The

difference to Soluflake is the slightly

lower acid solubility >80% vs~95%

and a slightly harder more brittle

flake.

It was introduced due to the large

demand for Soluflake in Saudi and

supply line issues.

Picture of experimental Extra Coarse Soluflake

Intellibore

• Drilling Fluids have recently introduced a methodology

that allows detailed design of drilling fluids for wellbore

strengthening in areas of weak fracture pressure or low

operating margins between mud weight and fracture

initiation pressure. It is aimed at expensive offshore wells

where the cost of the analysis and the time savings for

successful implementation warrant it’s use.

• The methodology requires a variety of geomechanical

inputs (15) into the Borewise model.


Geomechanics Model Input IntelliBore™ - Wellbore Strengthening


Formation Properties

• Young’s modulus

• Poisson’s ratio

• Biot’s constant

• Tensile strength

• UCS

• Internal friction angle

• Linear thermal coefficient

Formation Stresses

• Pore pressure

• Overburden

• Sh min

• SHmax

• Smax azimuth

Fracture Parameters

• Height

• Length

• Toughness

Geomechanics analysis requires fifteen input parameters

Borewise Model – example output IntelliBore™ - Wellbore Strengthening


Functions / Capabilities

• Temperature effects on Formation Breakdown Pressure

• Formation properties data base

• Single point / batch analysis

• Range options – sensitivity analysis

– Inclination

– Azimuth

– Young’s modulus

– Pore pressure

IntelliBore Integrated Solution Process IntelliBore™ - Wellbore Strengthening


Well Data

• Customer

• E-Log

• Pore Pressure

• Offset wells

• Mud System

BoreWise - Geomechanics Model

• Fracture Characterization: Depth & Width

• Single Point Analysis - Fracture Pressures

• Inclination / Azimuth changes

• Drilling Window Analysis

BridgeWise – Bridging

• PSD Optimization

• Drill-In Fluid Design

• Wellbore Strengthening

• Fracture Closure Pressure

Dynamic Temperature Modeling

• Circulating Temperature Profile

• Tripping Schedule

• ECD Spike

Advantage® Engineering

• Hydraulics

• Hole Cleaning

• ECD/ESD

• Bit Optimization

• Swab / Surge

Laboratory

• Formulation

• Optimization

• Return Perm

GeoWise

Drilling Fluid Formulation

Happiness is a plugged fracture!

Questions?


Janchik R Lost Circulation Solutions for Lime Stones and Induced Fractures

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