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Master in Petroleum Engineering 2007-2008

Kick Tolerance

Definition, calculation and analysis of results

for the application in well design, drilling and well control operations. Choke and Kill friction losses influence in Deep Water Wells.

San Donato Milanese – October the 23rd-24th 2008

Author

Gabriele Zaccaria

Division Exploration & Production Dept. WEDE/PERF Company Tutors Giuseppe Lanzi Luca Carazza University Tutor Francesca Verga

(2)

Master in Petroleum Engineering 2007-2008

 Introduction

 Scope of the work

 Kick Tolerance Definition  Kick Tolerance Calculation

 Kick Tolerance in Planning Phase  Kick Tolerance in Drilling Phase  Kick Tolerance Parameters

 Deep Water Environment

 Innovative Drilling Technologies  Conclusions

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3

Introduction

The importance of kick tolerance in well operations has recently increased due to its implications in well design, in drilling and well control.

These implications are still

more evident in

wells

currently drilled by oil

industry

, for which more

complex planning and

execution are required in comparison with the past.

(4)

4

Scope of the work

To study a simple method for the application of kick tolerance concept in an effective way both in well design and drilling phase.

The proposed method allows to know, to evaluate and to analyze the kick

tolerance problem in order to make the drilling execution safer and more

economical by reducing the probability to have an incident.

This document purpose is to improve knowledge about Kick Tolerance

and represents a technical basis for the discussion on revision of STAP/PERF standard/procedure.

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5

Kick Tolerance Definition

Kick Tolerance is defined as the maximum kick volume that can be taken into the wellbore and circulated out without fracturing the formation at weak point (shoe), given a difference between pore

pressure and mud weight in use.

It is very important to recognise a

kick and quick shut-in the well in

order to limit Kick Volume and to carry out a successful control.

(6)

6 KICK TOLERANCE CALCULATOR (Beta Version)

CLOSE

CALCULATE

DP OD (in) 5

Shoe Depth (m) 3200

Hole Size (in) 8.5

DC OD (in) 6.75

TD (m) 5000

Shoe Fracture Gradient (sg) 2.15 Safety Factor (kgf/cm2) 15.0

Mud Weight (sg) 1.90

DC length (m) 200

Pore Gradient at TD (sg) 2.00 Gas Gradient (sg) 0.3

MAASP (kgf/cm2) 75 KICK TOLERANCE VOLUME (bbl) 60

Kick Tolerance Calculation

The maximum kick volume which can be circulated to surface without fracturing

is function of:

 well phase geometrical configuration;

 drill string dimension;

 formation, fracture, mud & influx gradients.

A spreadsheet has been implemented in

order to obtain the kick tolerance volume.

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7

Kick Tolerance Calculation

The amount of influx volume that entering in well depends on:

underbalance between mud weight and pore pressure

reservoir porosity and permeability

influx type

sensibility and reliability of detection equipment

reaction time of well control crew

type well shut in procedure

time of BOP closure

The same kick tolerance between two wells may not mean that they share the same level of risk because it is important to consider how quickly an influx will grow!

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8

It has been assumed:

 vertical well

 single monophase gas bubble

 two drill string diameters (BHA & DP)  one open hole size

 constant ECD profile

It has been neglected:

 gas velocity and its real distribution in the annulus  P & T influence on mud weight and influx gradient  gas composition, dispersion and solubility

Driller’s method has been used for the calculation.

These assumptions assures a conservative (safer) kick tolerance.

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9

Kick Tolerance Formula

Two mirror approaches have been performed in order to obtain a

correlation linking kick tolerance volume to the corresponding pore gradient or kick intensity.

(KI = PG – MW)

The correlation is biunique:

 by fixing bottom hole volume it is possible to obtain the

corresponding increase of pore gradient.

 by fixing pore gradient it is possible to calculate the

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10

First Approach

TD V C V C H FG IG) (MW MW TD SF 10 MW) (FG H H FG PG i_BH DP HS i_BH DP HS shoe shoe shoe

Second Approach

TD

PG

H

FG

IG)

(MW

MW)

(PG

TD

SF

10

MW)

(FG

H

C

(11)

11

Kick Tolerance Plot

This correlation is very incisive, especially in its graphical form.

TD = 4000 m Hshoe= 3000 m HS = 12” ¼ DP OD = 5” BHA OD = 8” BHAlength= 190 m DPlength = 810 m MW = 1.6 kg/l IG = 0.3 kg/l FG = 1,75 kg/l TD MAASP MW PG 10

Zero Kick Tolerance Volume “zero influx” 0,00 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

Kick Tolerance Volume (bbl)

K ic k I n te n s it y ( k g /l )

Kick Tolerance Plot

0

KI MW

PG

Max Kick Tolerance Volume Zero underbalance → swab case

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12

KT in Planning Phase

During the casing seat design, MAASP and Differential Pressure criteria

are used to select casing setting points.

10

)

(

FG

MW

H

shoe

MAASP

10

H

PG

MW

e

al Pressur

Differenti

Fracture Gradient Pore Gradient D E P T H PRESSURE GRADIENT kg/cm2/10m m

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13

KT in Planning Phase

Kick Tolerance limits are fixed basing on diameter of the drilled open hole.

Hole Size Kick Tolerance Volume

(inch) (bbl)

≥ 12.25 > 50

8.5 – 12.25 > 35

≤ 8.5 > 25

These values help the drilling engineer to verify the casing shoe depth.

The maximum pit gain used in the calculation is critical and must be selected as appropriate given existing field operating practices, rig equipment, and the skills of the rig personnel.

The lower value (25 bbl) is usually composed by :

The minimum noticeable pit gain (15 bbl)

The estimated pit gain that will occur to when the well is finally shut in (10 bbl)

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14

KT in Planning Phase

The requested kick tolerance volume limits have to satisfy the planned casing shoe depths.

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15

KT in Planning Phase

0,00 0,01 0,02 0,03 0,04 0 2 4 6 8

Kick Tolerance Volume (bbl)

K ic k I n te n s it y ( k g /l ) Hshoe= 3200 m DC 6 ¾” MW = 2.10 kg/l DP 5” 8 ½” Hole Size PG = 2.05 kg/l TD = 5000 m FG = 2.15 kg/l 9 5/8” CSG 200 m

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16

KT in Planning Phase

Mud Weight Kick Intensity SIDPP PG* PG*-PG ΔBHP

kg/l kg/l kg/cm2 kg/l kg/l kg/cm2 1.90 0.100 40.0 2.000 0.150 60.0 1.95 0.056 22.4 2.006 0.156 62.4 2.00 0.012 4.80 2.012 0.162 64.8 DC 6 ¾” DP 5” 8 ½” Hole Size PG = 1.85 kg/l TD = 4000 m Hshoe= 3200 m FG = 2.15 kg/l 200 m 0,00 0,05 0,10 0,15 0,20 0,25 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

Kick Tolerance Volume (bbl)

K ic k I n te n s ity (k g /l ) MW=1.90 k g/l MW=1.95 k g/l MW=2.00 k g/l MW=2.05 k g/l MW=2.10 k g/l 1,90 1,95 2,00 2,05 2,10 2,15 2,20 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Kick Tolerance Volume (bbl)

P o re G ra d ie n t (k g /l ) MW=1.90 k g/l MW=1.95 k g/l MW=2.00 k g/l MW=2.05 k g/l MW=2.10 k g/l

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17

KT in Drilling Phase

Following the example of many drilling’s contractors procedures, if kick tolerance

assume a value lower than the following limits, it is necessary to inform a

competent authority that will decide how to carry on the operations.

Well Type Development Exploration

& Appraisal Development

Exploration & Appraisal > 50 bbls 25 - 50 bbls < 25 bbls Bottom Supported Floater

Division Manager Approval or Business Unit Director of Operations

Performance Approval

OIM and Rig Manager Performance Informed

Operations Managers Performance Informed

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18

Kick Identification Chart

0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 90 100 110 Pit Gain (bbl) (SICP -S IDPP ) (kg/c m 2 ) Gas Kick Oil Kick Water Kick MAASP Gas Kick Water Kick Oil Kick

Kick Identification Chart

During the drilling phase it is possible to identify the influx type

In case of HPHT wells, gas could be in a liquid state until it reaches the

bubble point, therefore the gas detection is more difficult.

i H SIDPP SICP MW IG ( ) 10

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19

KT in Drilling Phase

Knowing pit gain and SIDPP, the same diagram used in the planning phase,

allows to estimate if or kick volume can be circulated out or bullheaded back

immediately into formation avoiding potential underground blowout phenomena.

Kick Tolerance 0 20 40 60 80 100 120 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 Kick Volume (bbl) S ID P P ( k g /c m 2 ) UNDERGROUND BLOWOUT WITHIN KICK TOLERANCE FRACTURING LINE KICK CIRCULATION WITH DRILLER’S OR WAIT AND WEIGHT

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20

Kick Tolerance Parameters

p frac shoe i BH i P P V V_ _ DP HS shoe DP HS i shoe i C IG MW MW PG TD SF MW FG H C H V ) ( ) ( ) 10 ) ( ( max _ _ Increase FG: - Formation Strengtheners - Cement Squeeze - Repeat LOT - Improve IG estimation knowing SICP and SIDPP - Knowledge of reservoir characteristics

- Increase MW

- Use ECD Minimize SF by reducing

choke operator error thank to drill crew training

Improve FG estimation

Use W&W method to limit casing pressure and to reduce the force generated by pore pressure

Early kick detection and hard well shut-in to minimize influx volume

Reduce open hole total depth by adding a casing

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21

Deep Water Environment

The continuous research of new

hydrocarbons reservoir into increasing

water depths means new challenges due

to the environment in which to work and to the equipment used for deep water.

Off line Dual Activity

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22

Choke and Kill lines effect

In deepwater, Choke and Kill line friction is an important factor, particularly

when the threshold between mud density and fracture gradient is really narrow.

Pressure losses in these lines are relatively high even at low circulation rates because of the considerable length and small diameter.

They reduce the MAASP and in

some instances the margin to circulate out the kick becomes is very low.

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23

Choke and Kill lines effect

Weight PV YP Mud SCR Range

(sg) (cP) (lbf/100sqft) (bbl/min)

Original Mud: 1,5 30 20 Minimum: 1

Kill Weight Mud: 2,0 30 20 Maximum: 5

CHOKE LINE DIMENSION:

Length ID

(m) (inch)

Section 1: 2000 3

Section 2: 0 0

Choke Line Pressure Loss:

Mud SCR Pressure Loss (psi) (bbl/min)

Original

Mud Kill Mud

1 222 222 2 250 250 3 304 378 4 503 625 5 744 923 ANNULUS DIMENSION:

Length Casing ID String OD (m) (inch) (inch)

3200 9,625 5

4000 8,500 5

Annulus Pressure Loss:

Mud SCR Pressure Loss (psi) (bbl/min)

Original

Mud Kill Mud

1 617 617 2 633 633 3 648 648 4 664 664 5 679 679 TD = 4000 m Hshoe = 3000 m HS = 12” ¼ DP OD = 5” BHA OD = 8” BHAlength= 190 m DPlength = 810 m MW = 1.5 kg/l PG = 1.55 kg/cm2/10m IG = 0.3 kg/l FG = 1.75 kg/cm2/10m

On-shore (without choke effect)

MAASP = 75 kg/cm2

Kick Tolerance Volume = 155 bbl

Off-shore (including choke effect)

MAASP = 40 kg/cm2

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24

Innovative drilling technologies

In challenging Deep HPHT wells, where kick tolerance is very narrow or doesn’t exist at all, it is necessary to use innovative technologies in order to be able to drill on.

Managed Pressure Drilling (MPD)

 ENI Near Balance Drilling (ENBD)

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25

Managed Pressure Drilling

(MPD)

MPD technology is the use of a closed, pressurizable mud returns system that provides

the ability to drill ahead and make jointed-pipe connections while maintaining the appropriate

annular pressure profile.

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26

ENI Near Balance Drilling

(ENBD)

ENBD allows “walking the line” between pore pressure and fracture gradient,

through precise and safe control of the annular pressure profile, during drilling.

ENBD integrates the advantages both of Continuous Circulation and Managed Pressure Drilling. Application of a continuous circulation device

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27

Conclusions

Kick Tolerance is an important concept that can be applied

both in drilling

operations and in casing program design.

Application of kick tolerance concept

is especially helpful in wells

currently drilled by oil industry

, for which more complex planning and execution are required.

Considering Kick Tolerance

made drilling execution safer and more

(28)

28

Conclusions

A correlation linking kick tolerance volume to the corresponding

kick intensity has been drawn.

During the planning phase

, a diagram can be used in order to verify if planned casing setting depth and mud weight are suitable to assure the minimum kick tolerance requirements.

During the drilling phase

,

knowing pit gain and SIDPP, the same diagram allows to estimate if or kick volume can be circulated out or bullheaded back immediately into formation avoiding potential underground blowout phenomena.

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29

It is important

monitoring the kick tolerance in real time

, by updating the

calculation every time there is a variation of the parameters which influence its value.

An analysis has also been carried out

on the parameters that influence kick tolerance. Based on it, some indications have been suggested in order to optimize the parameters.

In deepwater,

Choke and Kill line friction is an important factor

,

particularly when the threshold between mud density and casing shoe fracture gradient is really narrow.

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30

Acknowledgements

I would thank

Eni E&P Division Management

for

permission to present this work and related results

and

WEDE/PERF

colleagues for the technical support

References

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