kickt1-Tolerance, well engineering .pdf

Well Engineering, Kick Tolerance

1. Well Engineering & Construction
KICK TOLERANCE
AL-KHALIDI SEHAM JALAL
MISKOLC UNIVERSITY
2013

2. CONTENTS
Introduction
Casing Seat Selection
Kick Tolerance Definition
KICK TOLERANCE ELEMENTS
Causes of Kick
VOLUME OF GAS INFLUX
Circulation Kick Tolerance
Gas Compressibility Factor
Well Kick Detection

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 performanceare
required in comparison with the past.
Therefore
Kick tolerance is a key element
when establishing a well design.
The number of sections will rely
on the engineered data from
the set of regulations governing the
safety (kick tolerance) for each section

4. Casing Seat Selection
The selection of casing setting depths is one of the most critical
in the well design process:
While the conservative selection of casing shoe depth could make
a well design uneconomical.
The unsuitable casing shoe depth could make a well undrillable.
Information is sourced from:
Seismic and geological background.
Drilling data from offset wells .

5. Casing Seat Selection
The pressure which the formation at the casing seat must
be able to withstand is the greater of:
the hydrostatic pressure of the mud used to drill the
next section.
the maximum pressure exerted at the casing seat when
circulating out gas influx from TD of the next hole
section.

6. Casing Seat Selection
The selection of the number of casing strings and their setting
depths generally is based on a consideration of the pore
pressure gradients and fracture gradients of the formations to
be penetrated :
The pore pressure and fracture pressure are expressed as an
equivalent density and are plotted vs. depth. A line representing
the planned-mud-density program also is plotted. The mud
densities are chosen to provide an acceptable trip margin above
the anticipated formation pore pressure to allow for reductions
in mud weight caused by upward pipe movement during
tripping operation.
A commonly used trip margin is 0.5 lbm/gal or one that will
provide 200-500 psi of excess bottom hole pressure over the
formation pore pressure

7. Casing Seat Selection

8. Casing Seat Selection
Point a: to prevent the formation fluid into the well and to
reach the desired depth.
Point b: to prevent the fracture of formation -->
intermediate casing need to run at this depth.
Point c: Fluid density is reduced until it reaches to margin
of the curve
Point d: casing shoe of the surface casing

9. Casing Seat Selection
During the casing seat design, MAASP and
Differential Pressure criteria are used to select
casing setting points.
M.A.A.S.P. =Maximum Allowable Annular Shut in Casing Pressure

10. 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.
Kick tolerance may also be defined the maximum allowable pore
pressure at next TD or maximum allowable mud weight which can be
tolerated without fracturing the previous casing shoe.
Kick tolerance can be understood as the capability of the wellbore to
withstand the state of pressure generated during well control operations
(well closure and subsequent gas kick circulation process) without
fracturing the weakest formation.

11. Kick Tolerance Definition
Kick tolerance is the maximum height of a gas column that the open
hole section can tolerate, without formation fracture occurring.
This height is then converted to a volume using the cross sectional area
and geometry of the wellbore and drill string to derive a limited 'Kick
Tolerance' in barrels or ppg equivalent.
Kick tolerance is the largest volume of influx that can be removed from
the well safely and is again based on the results of either a LOT .
When kick tolerance is calculated the result could be best described
as a measurement of well control risk when drilling the current hole
section.

12. Kick Tolerance Definition
Kick tolerance therefore depends on:
the maximum kick size.
maximum formation pressure at next
TD .
density of the invading fluid and the
circulating temperatures.
the maximum mud weight which can
be tolerated without fracturing the
weakest point in the open hole

13. Kick Tolerance Definition
It is very important to recognize a kick and
quick shut-in the well in order to limit Kick Volume
and to carry out a successful control.

15. Causes of Kick
1.Lack of knowledge and experience of personnel (Human error)–
Lacking of well-trained personnel can cause well control incident because they don’t have
any ideas what can cause well control problem. For example, personnel may accidentally
pump lighter fluid into wellbore and if the fluid is light enough, reservoir pressure can
overcome hydrostatic pressure.
2. Light density fluid in wellbore –
It results in decreasing hydrostatic pressure.
There are several reasons that can cause this issue such as
Light pills, sweep, spacer in hole
Accidental dilution of drilling fluid
Gas cut mud
3. Abnormal pressure–
If abnormally high pressure zones are over current mud weight in the well, eventually kick
will occur.

16. Causes of Kick Tolerance
4. Severe lost circulation –
Due to lost circulation in formation, ifthe well could not be kept fully filled all
the time, hydrostatic pressure will be decreased.
Lost circulation usually caused when the hydrostatic pressure of drilling fluid
exceeds formation pressure. There are several factors that can cause lost
circulation such as
Mud properties –mud weight is too heavy and too viscous.
High Equivalent Circulating Density
High surge pressure due to tripping in hole so fast
Drilling into weak formation strength zone

17. Causes of Kick Tolerance
5. Unable to keep the hole full all the time while drilling and
tripping
If hole is not full with drilling fluid, overall hydrostatic
pressure will decrease.
6. Swabbing causes reducing wellbore hydrostatic pressure.
Swabbing is the condition that happens when anything in a hole such as
drill string, logging tool, completion sting, etc is pulled and it brings
out decreasing hydrostatic pressure. Anyway, swabbing can be
recognized while pulling out of hole by closely monitoring hole fill in
trip sheet.

19. Kick Types
Gas Kicks
Rapid expansion as gas circulated through choke
Mud gas separators and flare lines used
Gas migration problems
Higher SICP than others
Gas Kicks, cont.
Barite settling in OB mud
Solubility of gas masks kick indicators
Flammability of gas
Slugging of gas at choke

20. Kick Types
Oil Kicks
Flammable but not as explosive as gas
Density greater than gas-lower SICP
Very little expansion as kick reaches
surface
But, there is almost always some gas
present

21. Kick Types
Water kicks
not flammable
very little expansion
lower SICP than gas or oil
But, there is still usually some gas present.

22. Kick Types
Prediction kick types
Density of gas =1-2 ppg
Density of oil = 6-8 ppg
Density of salt water =8.6-9.0
ppg

23. Equation for the determination of the density
of kick:
Kick Types

24. KICK TOLERANCE ELEMENTS
The following elements determine the magnitude
of kick tolerance:
Pore pressure from next TD
Mud weight to be used
Fracture Gradient at current casing shoe
Type of well exploration or development
Design influx volume that can be safely
circulated out

25. When to Calculate Kick Tolerance
After a leak-off test
Prior to drilling ahead,
If the mud weight is changed
When drilling into areas of overpressure
rapid pore pressure increase,
increasing mud weight to compensate,
kick tolerance is limited by formation
strength at the previous casing shoe.
KICK TOLERANCE ELEMENTS

26. Circulation Kick Tolerance
when the top of the gas bubble reaches the shoe, the pressure at the
casing shoe is given by:
where
Pf = formation pressure at next TD, psi
Pg = pressure in gas bubble = H x G
H = height of gas bubble at casing shoe, ft
G = gradient of gas = 0.05 to 0.15 psi/ft
TD = next hole total depth, ft
CSD = casing setting depth, ft
pm = maximum mud weight for next hole section, ppg

27. Circulation Kick Tolerance
Maximum tolerable length (H) of gas influx in the
annulus at any position between bottom hole and the
casing
where
FG = fracture gradient at the casing shoe in ppg
Pf = pore pressure in psi

28. Circulation Kick Tolerance
The kick tolerance values may be increased when:
1. drilling extremely high porous and permeable zones
(1-3 Darcie's)
2. using low technology kick detection equipment or
using old rigs
3. several transition zones are expected in same open
hole section are encountered
4. drilling from a semi-submersible rig

29. VOLUME OF GAS INFLUX
Flow rate into the wellbore:
Q = flow rate, bbl/min
k = permeability, millidarcy
Δp = pressure differential, psi
L= length of section open to wellbore, ft
μ = viscosity of intruding gas, centipoises
Re = radius of drainage, ft
Rw = radius of wellbore, ft

30. VOLUME OF GAS INFLUX
The amount of influx volume that entering in well
depends on:
underbalanced 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

31. VOLUME OF GAS INFLUX
In case of a kick occurrence the type of the influx
that enters the wellbore is required to be
determined.
The influx gradient can be evaluated using the
given ranges

32. VOLUME OF GAS INFLUX
A gas kick causes higher annular pressures than a
liquid kick.
A gas kick has lower density than a liquid kick.
A gas kick must be allowed to expand as it is pumped
to surface.
The objective for the well control is to always having
a constant bottom hole pressure. This is only possible
through having higher surface annular pressure that
can be maintained through the adjustable choke

33. BEHAVIOR OF GAS KICKS
Percolation of gas through
liquid in vertical open
hole.
Source: SPE 130693“Snubbing Units Used Effectively in Well-
Control-Recovery Efforts” by S.R. Wehrenberg, SPE, Boots &
Coots, et al

34. BEHAVIOR OF GAS KICKS
Source: SPE 130693“Snubbing Units Used Effectively in Well-Control-Recovery
Efforts” by S.R. Wehrenberg, SPE, Boots & Coots, et al

35. BEHAVIOR OF GAS KICKS
Gas/liqiuddistribution after 1 second of
simulation in relation
To Wellbore inclination.

36. Temperature Effect.
The change in temperature along the wellbore will affect the
density and the rheology of the mud, having a direct effect on
the hydrostatic gradient and the frictional pressure losses
during circulation. Currently, it is assumed that the
temperature in the open hole section is constant; thus, no
correction to the volume calculation is applied.
The effects of temperature on influx volume are described by
Charles law, which states that the volume of the gas is directly
proportional to the absolute temperature. Contrary to the
afterflow effect, the temperature correction results in a higher
kick tolerance. Therefore, the conventional constant-
temperature assumption results in a conservative solution.

37. Z-Factor Correction.
The compressibility factor, also know as z factor, takes account for
real gas behavior according to the particular gas composition of
the influx. A common assumption is to utilize z=1, as if the influx
behaved according to the ideal gas law.
The approach used to estimate this factor is not straightforward and
requires several different methods for the numerical calculation,
this makes it a hard task to perform without computer power.
The pseudo critical properties are calculated using Katz’s
correlations, and the factor requires Newton-Raphsoniterative
method combined with Dranchuk-Abou-Kassem or
HallYarborough correlations (best fit for single phase) or the
Beggs-Brill correlation when multiphase is considered.

38. Well Kick Detection
Well Kick Detection List Look The Indicators to Prevent Blowout
Positive Indicators of a Kick
1.Increase in Pit Volume
2.Increase in Flow Rate
Secondary Indicators of a Kick
1.Decrease in Circulating Pressure
2.Gradual Increase in Drilling Rate
3.Drilling Breaks
4.Increase in Gas Cutting
5.Increase in Water Cutting or Chloride

39. Well Kick Detection
Indicators of Abnormal Pressure
1.Decrease in Shale Density
2.Change in Cuttings Size and Shape
3.Increasing Fill on Bottom After a Trip
4.Increase in Flow Line Temperature
5.Increase in Rotary Torque
6.Increasing Tight Hole on Connections

40. Innovative drilling technologies
In challenging Deep HPHT wells, where
kick tolerance is very narrow , it is
necessary to use innovative
technologies in order to be able to
drill on.
Managed Pressure Drilling (MPD)
ENI Near Balance Drilling (ENBD)
They allow to manage the bottom
hole pressure properly.

41. 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.

42. ENI Near Balance Drilling
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 may give great benefit, especially in combination with annular
back-pressure

44. Shut in Procedures For Well Control Operation
Shut in procedures are specific procedures for closing a well in case of well
control situation and personnel on the rig should get proper training and
be familiar with these procedures.
Themain reason to have the specific shut in procedure is to minimize kick
volume entering into a wellbore when well control situation occurs.
Basically, the faster to recognize kick and shut in a well, it is the better to
manage a well control situation. The amount of wellbore influx that enters
the wellbore are minimized when personnel respond quickly to shut the
well in. It is the fact that a small amount of kick entering into the wellbore
will result in lower initial shut-in casing pressure and lower casing pressure
while circulating. What's more, the lower pressure at surface will reduce
the chance of breaking down hole formation, generally called underground
blowout.

45. Types of Shut-In
In the drilling industry, there are 2 types of shut in which are Hard Shut-
in and Soft Shut-in.
Hard shut in:It means that while drilling, choke line valves are in a
closed position. When you have the well control, you just shut in a
blow out preventor. The choke valves will be opened when we kill
the well. The hard shut-in is the fastest method to shut in the well;
therefore, it will minimize volume of kick allowed into the wellbore.
Soft Shut In:It means that while drilling, the choke line valves are in an
opened position. When the well control situation is occurred, you
shut in the blow out preventor and then close choke valves to shut
in the well. The soft shut in procedure allows fluid to lowthrough
the surface choke line before the well will be completely shut in. This
is the bad part of the soft shut in procedure because it doesn't
minimize size of the wellbore influx.

47. 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 economical by reducing
the probability to have an incident.

48. THANK YOU
AL-KHALIDI SEHAM JALAL
MISKOLC UNIVERSITY
2013