High Temperature High Pressure Applications

Definition - High Temperature High Pressure (HTHP) reservoirs generally exhibit the following features:

• Reservoir depth greater than 15,000 feet

• Reservoir pressure greater than 15,000 psi

• Reservoir temperature from 325-500 °F

Definition - High Temperature High Pressure (HTHP) reservoirs generally exhibit the following features:

• Reservoir depth greater than 15,000 feet

• Reservoir pressure greater than 15,000 psi

• Reservoir temperature from 325-500 °F

HTHP Cementing Considerations• Cement Sheath Integrity

– What forces will cement sheath experience during life of well?

– Does application require resilience, compressibility, abrasion resistance, acid resistance, etc.?

– Do mechanical properties of slurry meet needs?

HTHP Cementing Considerations• Wellbore Temperature

– Accurate BHCT and BHST are critical

– Use temperature recorders when possible

– New API correlations included in OPTICEM and CEMLAB

HTHP Cementing Considerations• Slurry Density

– Slurry density at least 1 ppg heavier than mud

– Surface mixing viscosity often high– Pressurized drilling fluid scale used

due to air entrainment

HTHP Cementing Considerations• Retardation

– Know temperature limitations of additives– Sensitivity to small changes in

concentration not desired– No gellation humps– CAHT-1

HTHP Cementing Considerations• Strength Stability

– Above 230 °F , SSA-1 or SSA-2 must be added to prevent strength retrogression.

HTHP Cementing Considerations• Viscosity/Suspension

– Thermal thinning occurs as temperature increases– Slurry must have sufficient viscosity at BHCT to

suspend solids– In critical applications slurry should have no free water.– Adequate viscosity at BHCT may result in high surface

viscosity– Smaller particle size additives suspend easier but may

increase mixing viscosity (ex. SSA-1, MicroMax, HI-DENSE #4)

HTHP Cementing Considerations

• Filtration Control– Normal fluid loss guidelines apply– Know temperature limitations of

additives

HTHP Cementing Considerations

• Gas Migration– GasStop HT Gas Migration Control

Additive• Controls gel strength development

from 200-350 °F• Controls fluid loss up to 500 °F

Strength Stabilizing Additives• SSA-1 (Silica Flour)

– Fine silica– Prevents strength retrogression– 35% (or greater) when BHST’s > 230 °F– Better suspension

• SSA-2 (Oklahoma No. 1)– Coarse silica– Same application as SSA-1 – Heavy weight applications

• SSA-1 (Silica Flour)– Fine silica– Prevents strength retrogression– 35% (or greater) when BHST’s > 230 °F– Better suspension

• SSA-2 (Oklahoma No. 1)– Coarse silica– Same application as SSA-1 – Heavy weight applications

Slurry Integrity Additives

• Suspend HT– Does not affect mixing viscosity– Material is temperature activated (140 to 160 °F)– Functions

• Provides lower mixing viscosity• Counteracts thermal thinning • Provides solids suspension down-hole• Controls free water

– Should be dry blended with cement • Low pH environment causes premature gelation

– Application• 250 to 400 °F• Fresh water• Up to saturated salt

• Suspend HT– Does not affect mixing viscosity– Material is temperature activated (140 to 160 °F)– Functions

• Provides lower mixing viscosity• Counteracts thermal thinning • Provides solids suspension down-hole• Controls free water

– Should be dry blended with cement • Low pH environment causes premature gelation

– Application• 250 to 400 °F• Fresh water• Up to saturated salt

Slurry Integrity Additives

• Silicalite • Silicalite 97L

–Liquid Silicalite –50% active aqueous suspension

• Silicalite • Silicalite 97L

–Liquid Silicalite –50% active aqueous suspension

Slurry Integrity Additives

• GasCon 469– 15% active aqueous suspension– Imparts thixotropic properties

to slurry – 40 to 250 °F – GasCon 469 Winterized (when

stored < 40 °F)

• GasCon 469– 15% active aqueous suspension– Imparts thixotropic properties

to slurry – 40 to 250 °F – GasCon 469 Winterized (when

stored < 40 °F)

Slurry Integrity Additives

• Microblock– 50% active aqueous suspension– Imparts thixotropic properties

to slurry– Extender for light weight

cements– 60 to 400 °F

• Microblock– 50% active aqueous suspension– Imparts thixotropic properties

to slurry– Extender for light weight

cements– 60 to 400 °F

Slurry Integrity Additives• FWCA (WG-17)

– Free water control agent– Prevents solids segregation– Increases mixing viscosity– 80 to 200 °F (mild retarder)

• Bentonite• Attapulgite• ECONOLITE

• FWCA (WG-17)– Free water control agent– Prevents solids segregation– Increases mixing viscosity– 80 to 200 °F (mild retarder)

• Bentonite• Attapulgite• ECONOLITE

Flow Through Unset Cement

• Mechanism

• Characteristics

• Solutions

• Mechanism

• Characteristics

• Solutions

Hydrostatic Pressure Loss

CementFluid

CementGels

CementHardens

CementSets

Formation Gas Pressure

OverbalancePressure

Time

Hyd

rost

atic

Pre

ssu

re

Gas ChannelFormation

• Cement slurry placed

• Slurry behaves as a fluid

• Transmits full hydrostatic pressure

• Cement slurry placed

• Slurry behaves as a fluid

• Transmits full hydrostatic pressure

Permeable Zone

Gas Zone

Gas ChannelFormation

• Static gel strength devel-opment begins

• Fluid loss to formations

• Volume reduction causes pres-sure loss

• Static gel strength devel-opment begins

• Fluid loss to formations

• Volume reduction causes pres-sure loss

FiltrateLoss

Gas ChannelFormation

• Overbalance Pressure is lost

• Fluid loss continues in lower pressure zone

• Gas enters wellbore and percolates up annulus

• Overbalance Pressure is lost

• Fluid loss continues in lower pressure zone

• Gas enters wellbore and percolates up annulus

FluidLoss

GasEntry

Gas ChannelFormation

• Percolation leads to gas channel formation

• Permanent channel left after cement sets

• Percolation leads to gas channel formation

• Permanent channel left after cement sets

GasChannel

Gas Migration Through Unset Cement

• Laboratory testing was conducted with SGS effects and fluid loss simulation

• Channels were found in set samples of cement slurries in which gas migration occurred

• Laboratory testing was conducted with SGS effects and fluid loss simulation

• Channels were found in set samples of cement slurries in which gas migration occurred

Overbalance Pressure Is Lost Due To The

Combined Effects Of:1. Static Gel Strength2. Volume Loss

1. Static Gel Strength2. Volume Loss

Potential Pressure Loss Due to Static Gel Strength

P = (SGS / 300) x (L / D)P = (SGS / 300) x (L / D)

Static Gel Strength is the Internally Developed

Rigidity Within the Matrix Which Resists Forces

Placed Upon It

Actual Pressure Loss Is Not Caused By Static Gel Strength Alone. It Must Be Accompanied

By Volume Loss

Potential Pressure Loss Due to Volume Loss

P =P = V / CF V / CF

Volume Loss Due to Pressure Loss• Small volume loss from

a pressurized hydraulic system will cause a very large pressure loss

• Since cement slurry is incompressible (“dirt” and “water”), a small volume loss will cause a large pressure loss

• Small volume loss from a pressurized hydraulic system will cause a very large pressure loss

• Since cement slurry is incompressible (“dirt” and “water”), a small volume loss will cause a large pressure loss

∆P(SGS)

0 psi

1000 psi

∆P(SGS)

0 psi

1000 psi

Actual Pressure LossActual Pressure Loss

Actual Pressure Loss

0 psi

0 psi

Actual Pressure Loss

0 psi

0 psi

P(VL)

1000 psi

0 psi

Maximum SGS for Gas Flow

0

100

200

300

400

500

0 20 40 60 80

Time (minutes)

Sta

tic

Gel

Str

eng

th (

lbs/

100

ft2)

No Gas flow

Gas Flow

Flow Potential Factor

FPF = MPR / OBP

MPR = (500 / 300) x (L / D)

FPF = MPR / OBP

MPR = (500 / 300) x (L / D)

GAS FLOW POTENTIALGAS FLOW POTENTIAL

< 0 0 – 1 1 – 4 5 – 7 8 – 15 > 15

Blowout Negligible RedesignFlow Condition 1

“Minor”

Flow Condition 2

“Moderate”

Flow Condition 3

“Severe”

• Fluid Loss Control• Modified Job Design• Fluid Loss Control• Modified Job Design

1 2 3 4

Flow Condition 1Minor

Minor GFP Solutions

Limits Volume Reduction

Lowers GFP by use ofbackpressure, shortenedcement column, and otherparameters

Limits Volume Reduction

Lowers GFP by use ofbackpressure, shortenedcement column, and otherparameters

Fluid Loss Control:

Modified Job Design:

Fluid Loss Control:

Modified Job Design:

• GasStop• GasStop HT• Thixotropic Cements

• GasStop• GasStop HT• Thixotropic Cements

Flow Condition 2Moderate

5 6 7

Moderate GFP Solutions

Delayed Gel Strength

(in a static environment):

Thixotropic Cements:

Delayed Gel Strength

(in a static environment):

Thixotropic Cements:

Delays Gel Strength withRapid Transition Time

Rapid Gel Strengthminimizes time for gasto percolate in annulus

Thixotropic CementThixotropic Cement

0

100

200

300

400

500

600

0 20 40 60 80

Tim e (m in)

Sta

tic

Gel

Str

eng

th

Normal Cement

Thixotropic Cement

0

100

200

300

400

500

600

0 0.5 1 1.5 2 2.5 3 3.5 4

Time (Hours)

Sta

tic G

el S

tren

gth

Delayed Gel Strengthand Fluid Loss

Delayed Gel Strengthand Fluid Loss

Normal Cement

Fluid Loss Rate

Gas Stop

• Super CBL• Foam Cement• Super CBL• Foam Cement

Flow Condition 3“Severe”

8 9 10 11 12 13 14 15

Cement w/ insitu gas generatorsCement w/ insitu gas generatorsCement

FluidCement

GelsCementHardens

CementSets

Formation Gas Pressure

OverbalancePressure

Time

Hyd

rost

atic

Pre

ssu

re

Halliburton Gas Flow Solutions

Minor GFPMinor GFPModerate GFPModerate GFP

Severe GFPSevere GFP

Thermalock

• Non-Portland cement that can be used in high CO2 concentrations, corrosive, geothermal and thermal environments.

• Blend of high alumina cement, flyash, and a phosphate containing compound.

• Can be used at BHST’s up to 700 degs. F and retarded to BHCT’s of 240 degs. F.

• Non-Portland cement that can be used in high CO2 concentrations, corrosive, geothermal and thermal environments.

• Blend of high alumina cement, flyash, and a phosphate containing compound.

• Can be used at BHST’s up to 700 degs. F and retarded to BHCT’s of 240 degs. F.