Enhanced oil recovery

1. By
Ramanand
Roll- PE16M005
M. Tech. Petroleum
IIT MADRAS.

2. • Introduction and Objectives about water injection
• Integrated Waterflood management system
• Engineering calculation of CVC, IVC in Water injection
• performance Plots used for analysis
• Profile modification job
• Low salinity water flooding
• References
CONTENTS

3. Mechanism Primary Recovery Potential for Waterflooding
Fluid Expansion Drive 3 to 10 % Good
Gravity drainage Drive 5 to 30 % Moderate
Solution Gas Drive 10 to 15% Good
Gas Cap Expansion 20 to 40 % Poor
Water Drive 35 to 50 % Poor
Table 1 Potential for Waterflooding
Water injection is the most popular method of secondary recovery.
It is done in oil reservoirs for waterflooding (sweeping the oil to producers) and
for pressure support( filling the voidage left by produced fluids).
It maintains the reservoir and well flowing bottom hole pressure above the fluid’s
bubble point pressure.

4. Fig1: Water-flooding Reservoir Engineering Aspects

5. • One of the basic methods employed to judge the effectiveness of a
water injection plan is the calculation of IVC and CVC.
• IVC or Incremental Voidage Compensation gives the ratio of pressure
compensated by injected water to the pressure depleted by produced
oil according to the current status of the specific reservoir pay zone.
• IVC may exceed 100% in many cases in order to make up for late water
injection in many pay sands
• For all cases, the goal of oil producing company is to maintain 100%
IVC at least to restrict the fall in pressure and the lack of which might
lead to a loss in producing the ultimate reserves.

6. • CVC or Cumulative Voidage Compensation gives a ratio of the total water
injected since the date of inception to the voidage created by production of
all the wells in the payzone.
• This includes production in the form of oil, water and gas. The CVC value for a
particular payzone can never exceed 100%.
Example: An asset has following injection well and production well data in a
single month so find IVC.
Given: Bg=0.01 v/v Rs=90 v/v Qo =7845 m3 Qg =977804 m3
Bo=1.314 v/v Bw= 1 Wp = 214.103667 m3/day
Water Injected per day = 979 m3/day

7. Calculation of IVC
• Find oil produced per day in the given month (Qo) = Net oil produced in
month / 30
• Find gas produced per day in the given month (Qg) = Net gas produced in
month/30
• Find Rp, where Rp = Qg / Qo
• Find the gas reserves produced = (Rp – Rs) x Bg
• Where Bg is the Gas FVF, Rs is Gas Solubility
• Voidage = [Bo + ((Rp-Rs)xBg) ] Qo + Wp xBw
• Where Wp is the water produced.
IVC = (Water injected per day / Voidage produced) x 100

8. Qo,
m3/day
Qg, m3/day Rp=Qg/Qo Gas produced
(Rp-Rs)Bg
Voidage =
[Bo + ((Rp-
Rs) xBg)] Qo
+ WPx Bw
IVC = (Water
injected per
day /
Voidage
produced) x
100
7845/30 =
261.5
m3/day
977804/30 =
32593.466
m3/day
32593.466/
261.5 =
124.640405
(124.640405 –
90) x0.01
=0.3464041
[1.314 +
0.3464041]
x261.5 +
214.103667
x1
=648.3m3/d
ay
979/648.3 x
100 =151%
Thus the IVC is 151% for that month .

10. PERFORMANCE CURVES FOR WATER INJECTORS
Graph 1: cumulative oil, liquid rate, oil rate vs. Time
In case of Waterflooding we can see that oil production rate is drastically increasing from
starting of water injection, hence increased oil recovery.

11. Graph 2: water cut, GOR vs. Time
Water cut increases in nearby producing wells as Waterflooding get started.
While GOR remains constant this shows water breakthrough in nearby
producing wells. We need to monitor WC in producing wells regularly.

12. “Profile Modification job” of injector well #039
BRIEF HISTORY
A well #39 was completed Early as a development well. Initially the interval
1585-1592 m in pay zone was perforated. It was converted to water injector later .
Injection was stopped as water break through observed in well#29A. Injection
was suspended till few year. Injection restarted in a in a controlled manner. The
well was taken for injection profiling job later. Profile modification was completed
With Good result.

13. • LOG OBSERVATION
LOGGS RECORDED:
•GR, casing collar locator log
Temperature, Pressure and FLOW logs
where recorded.
•From the temperature log it is
observed that interval 1585-1591m is
taking the injection fluid. The bottom
interval 1591-1592 is not taking any
fluid

14. PROFILE MODIFICATION JOB
• In order to control the flow, Profile modification Job using polymer
Alcoflood 995Water Control Polymers _ BASF SE n.pdf with cross linkers
Hexamine is recommended.
• Source: Investigating the Effect of Several Parameters on the Gelation
Behavior of Partially Hydrolyzed Polyacrylamide–Hexamine–Hydroquinone
Gels - Industrial & Engineering Chemistry Research (ACS Publications).pdf .
• The purpose of using Polymers with cross linkers is to provide resistance to
the flow of injection fluid into the formation, which in turn will control the
flow rate.
• Job was carried out in three stages. At the Pre-flush stage, pumping of 1%
brine solution was done along with the cross linkers as per the suggested
proportion. In the Main Job, a total of 130 m3 of polymer gel solution was
injected. Then the After-flush involved the injection of the injection water.
Well was kept closed for a week and after that injection was started

15. COMPARING PROFILE MODIFICATION JOB
Well no Qo,m3/d GOR W/C Qo,m3/d GOR W/C
40 4.61 14.05 30.09 5.20 19.47 29.51
Before Profile modification job After Profile modification job
• The result of this got quickly reflected to the prompt decline of water cut of the offset
producers namely well#040, where W/C got reduced from 91% to 26% respectively. The
average life of this job is around 10-12 months.

16. Low salinity water flooding “Smart Water” for
Enhanced Oil Recovery
• Low salinity water flooding an environmentally friendly EOR method
• It Opens the route for alkaline flooding and alkaline/surfactant flooding as it
impose wettability alteration
• Low Salinity fluid (Salinity: 1000-2000 ppm)
• There are other advantages to injection of low salinity brine, such as reduction
in scaling and corrosion of the equipment used in the field (Collins, 2011). This
method can also reduce the potential for reservoir souring. All of these factors
contribute in a positive manner to project economics.

17. • Wettability modification towards more water-wet condition, generally
accepted
• Wettability can be altered by change in surface chemistry and adsorption
phenomena
• Adsorption of dication such as : Ca2+, Mg2+, can alter the initial wettability
towards water wetness so this observation is important for LSW flooding.
• wettability mechanism

18. • water injection is a key element in modern oil field operation. An
Unsuccessful water injection scheme resulting in imitated reservoir pressure
support, poor sweep efficiency and excessive water production.
• Practical Approach including geologist, geophysicist, reservoir engineer,
chemist, production and drilling engineers is needed for laboratory
investigations, designing, implementation and monitoring of a waterflooding
process.
• Profile Modification ofthe considered Field of the Asset successfully controls
the high water cut in nearby producing wells
• Smart Water/ low saline waterflooding for wettability alteration to enhance
oil recovery is Future aspect of EOR.

19. • AbdusSattar&Ganesh.C.Thakur, integrated petroleum reservoir management, pennwell
books, pennwell publishing Company, Tulsa, Oklahoma
• ONGC ANNUAL Report of Ahmedabad Asset .
• Water Control Polymers http://www.oilfieldsolutions.
basf.com/ev/internet/oilfieldsolution en_GB/applications/stimulation/watercontrol
• Gupta, R., Smith, G., Hu, L., et al. 2011. Enhanced Waterflood for Carbonate