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
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
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 morecomplex planning and
execution are required in comparison with the past.
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.
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 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.
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!
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.
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
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 shoeSecond Approach
TD
PG
H
FG
IG)
(MW
MW)
(PG
TD
SF
10
MW)
(FG
H
C
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
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
shoeMAASP
10
H
PG
MW
e
al Pressur
Differenti
Fracture Gradient Pore Gradient D E P T H PRESSURE GRADIENT kg/cm2/10m m13
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)14
KT in Planning Phase
The requested kick tolerance volume limits have to satisfy the planned casing shoe depths.
15
KT in Planning Phase
0,00 0,01 0,02 0,03 0,04 0 2 4 6 8Kick 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
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
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
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
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
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
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
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.
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
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)
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.
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
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
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.29
It is important
monitoring the kick tolerance in real time
, by updating thecalculation 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.
30