This document discusses various methods for controlling water and gas coning in oil wells, including dual completions, chemical treatments, and downhole water sink (DWS) technology. DWS involves installing a second completion below the oil-water contact to drain and produce water, preventing it from coning into the main oil zone. It has been shown to effectively control coning through creating a hysteresis effect. While simple to implement, DWS may not be economical for low-producing wells. Overall, DWS appears to be one of the most effective methods for retarding unwanted water and gas influx compared to alternatives like producing below critical rates or using polymers that can damage the reservoir.

1. DEPARTMENT OF PETROLEUM ENGINEERING
INDIAN SCHOOL OF MINES, DHANBAD
WATER AND GAS CONING:
MODELLING AND SOLUTIONS
Prof. A.K. Pathak
Department of Petroleum Engineering
ISM Dhanbad
Shubham Saxena
2012JE1152
B.Tech. Petroleum Engineering
ISM Dhanbad

2. Water Coning and
Gas Coning
Encroachment of gas
from the gas cap and
water from the water
aquifer into the oil
producing zone.
The previously defined
GOC
WOC

3. Effects
•Reduction in oil production rate.
Water and gas have much higher mobility than oil
•Corrosion of production facilities
•Loss of gas cap drive
•Loss in water drive

4. •There is expense to lift, dispose or re-inject
produced waters, as well as the capital
investment in surface facility construction and
to address other environmental concerns.
•Unwanted production of water estimated to cost
the petroleum industry about $45 billion a year.

5. Payzone and water coning
with time

6. 1. Perforation Squeeze-off and Re-completion
High permeable layers in contact with the water zone are
often times responsible for the high water influx.
These could be isolated by cement squeeze operation below
operation below the perforated zone or cementing water
cementing water producing perforated zones.
In some cases, an entire perforation is completely squeezed
completely squeezed off and the well is re-completed higher
completed higher up the structure away from the oil-water-
the oil-water-contact (OWC).
Cement squeeze operation may not be feasible or effective if
or effective if adequate zonal isolation is not possible due to

7. These are injected into the formation, if
the production of unwanted water is
traceable to fracture paths.
Selective relative permeability modifier
that is capable of reducing relative
permeability to water without
affecting relative permeability to the oil
and/or gel treatment.
Typically cross linked polymers,
products like MaraSEAL and
OrganoSEAL-R systems can be easily
mixed and have a long working life.
2. Use of Chemicals, Polymers and Sealants

8. 3. Water Coning Control with Dual Completions in Vertical
Wells
In a dual completion string we
separately produce the oil and
water zones and
thus counter the cone
development
Two perforations – one in the oil
zone
& one in the water zone below
the original oil-water contact.
The top completion is placed as high as possible, within the top 20
percent of the oil zone and the second perforation placed at some depth
below the oil water contact.

9. DWS technology controls water coning by employing a
hydrodynamic mechanism of water drainage in-situ
below the well’s completion.
This localized drainage is generated by a second completion -
downhole water sink - installed at, above, or beneath the oil or
gas-water contact.
The two completions are hydraulically isolated inside the
well by a packer.
The bottom (water sink) completion employs submersible
pump.
The submersible pump drains the formation water from
around the well and prevents the water from breaking through
the oil column and getting into the oil-producing perforations.
4. Dual completion technology with Downhole Water Sink (DWS)

10. Types of DWS Completions
(i) A DWS well is dual - completed for oil
production and water drainage (water sink).
Water is produced from annulus and and oil is
produced from production tubing.
The two completions are hydraulically isolated
inside the well by a packer.
The bottom (water sink) completion employs
submersible pump and water-drainage
perforations.
(ii) A similar DWS well but with water produced
production tubing and oil from annulus.

11. (iii) DWS with both Oil and Water
produced from separate production
tubing
It is very costly.
Not possible for less diameter
or slim wells.
GLV can be equipped to lift
up both water and oil.

12. (iv) DWS configuration for gas wells including dual
completion with gravity gas/water separation
Water from the aquifer
underlying the oil zone which
has entered the wellbore is
allowed to fall down through a
smaller diameter liner with a
pump pumping the water into
another aquifer beneath it.

13. The two basic Variants.
Variant A:
DWS- water injection
Variant B: DWS-
water production

14. Downhole separator
• Downhole separator installation
reduces the production of excessive
water.
• The device is coupled with electric
submersible pumps that allow upto
50% of the water to be separated and
injected downhole to avoid lifting and
surface-separation costs.
• Separating water downhole reduces the
lifting costs of excess water. Typical
downhole separators are 50% efficient.
The excessive water is injected into
other formation.

15. Cusping in Horizontal Wells
Flux model in
horizontal wells
Formation of
water crest

16. Tail-Pipe Water Sink Completion

17. Bilateral Water Sink Technology

18. DEVELOPNMENTS
Mathematical models have been developed to predict the performance of oil
wells with water coning problems after water breakthrough. Muskat and Wyckoff
(1935) and Muskat, (1949) observed that coning is a rate-sensitive phenomenon,
which develops only after certain equilibrium conditions are unbalanced by
increasing the pressure differential beyond critical limits.
Wyckoff (1935) also determined the critical oil rate analytically solving Laplace
equation for single-phase flow and for a partially penetrating well.
Wheatly, also observed that the value of the well radius does not significantly
affect the critical rate of production. This is contrary to Schol’s (1972)
observation.
Guo and Lee (1993) demonstrated that the existence of the unstable water cone
depends on the vertical pressure gradient beneath the wellbore. “If the vertical
pressure gradient is higher than the hydrostatic pressure gradient of the water,
the unstable water cone can be observed and the associated critical oil rate
exists”

19. Water and Gas coning features
High pressure gradient/high fluid velocity (production rate)
stimulates water coning.
Completion at the topmost part of the oil zone (preferably the top
45 percent) away from the oil-water-contact delays the time to
water breakthrough.
Critical oil rates for water-free oil productions are typically
uneconomical for all practical purposes.
The gas produced in gas coning is not very economical as compared
to the oil.

20. After water breakthrough in the wellbore, water production
increases rapidly and significant resources and efforts have to be put
into water disposal and oil/water separation facilities.
The development of the water cone creates bypass oil problem and
consequently shortens the producing life of the well.
A corollary is that more money is spent on infill drilling to recover
bypassed oil reducing the economic gains of the field.

21. CONCLUSIONS
Out of the various method to control and retard water and gas influx DWS
seems to work best.
Producing below critical rate or halting production can be uneconomical
at times.
While Polymer injection damage the payzone. The control of water
coning/cresting with Downhole Water Sink (DWS) technology in both
vertical and horizontal wells has been analyzed in this study. The
application of the technology in controlling water coning creates a
hysteresis effect.
DWS may not be economical for low producing wells.

22. Reference
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CONTROL --- THEORETICAL
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Water Coning in Horizontal Wells: Prediction of Post-Breakthrough Performance

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24. Thank You