Copyright 2014, Society of Petroleum Engineers This paper was prepared for presentation at the SPE Saudi Arabia Section Annual Technical Symposium and Exhibition held in Al -Khobar, Saudi Arabia, 21-24 April 2014. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessar ily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.

Abstract In conventional cyclic steam stimulation (CSS), steam is periodically injected at high pressure to the reservoir. After the

steam injection period, the well is soaked for several days then it will be produced. Generally, for the first to the fifth cycle,

the steam can effectively transfer the heat to the reservoir. After that, the CSOR will rise up indicating that the process is

currently ineffective.

This paper aims to improve the CSS performance using modified well completion. The perforation is modified to become

two parts, one part is on the top side (as injection) and the other part is on the bottom side (as production). In this process,

after being injected, the steam will condense, resulting from heat loss, and it will move to lower part because of gravity

drainage. Simultaneously, crude oil was produced through the production perforation. The opening-closing of the injection-

production cycle is managed by interval control valve (ICV). To provide an overview of this phenomenon, a synthetic

reservoir model was built based on Pertama-kedua formation, located in Sumatra Indonesia. Sensitive variables are length of

the injection-production perforation and soaking time. Finally, the heat efficiency was evaluated during 8 years of project

life.

Simulation results show that dividing the perforation into injection and production intervals will reduce CSOR 30% and this

requires shorter soaking time compared to that of conventional processes. Furthermore, if the distance between injection and

production interval is longer the production will be better. However, this gap is limited by reservoir thickness.

Key word: CSS, heat efficiency, ICV, CSOR.

Introduction Total estimated reserve of heavy oil in the world is approximately 3,396 billion barrels of original oil in place, of which 30

billion barrels are included as prospective undiscovered reserve (F. Richard, 2007). To produce these resources, several

methods have been successfully applied such as cyclic steam stimulation (CSS), steam flooding, SAGD process, and non-

thermal recovery.

CSS is a well stimulation method involving the transfer of heat to reservoir by periodical injection of steam into the

production well. This method was first applied in the late 1950s to recover bitumen from the tar sands of Venezuela.

Following the successful field trial, CSS has been applied worldwide to recover heavy oil and bitumen. The process can get

a recovery factor of 3 – 10% of the remaining oil in place (Hong KC, 1994).

In other cases, the ultimate recovery factor could be greater than 20% as reported by Esso, or it could be much lower as is in

some of the projects in Cold Lake. In some cases such as those in Duri Indonesia, it can be switched to steam-flooding after

CSS period is over. However, it also might not be feasible as demonstrated in several cases in Cold Lake, Canada. (Faroug

Ali S.M, 1994).

Furthermore, in good quality reservoirs, CSS is just the initiation of a bigger process. After it is over, the best way is to

continue to steam flooding. In other cases, the complexity of geological structure makes the continuous steam flooding very

difficult due to shale barriers, sealing faults, and discontinued formation. Therefore, improving CSS method plays a very

important role to increasing recovery factor.

In CSS process, the initial oil production rate is usually high due to large reservoir pressure increase, high initial oil

saturation, and reduction of oil viscosity. The well can be produced for several months. After several cycles, the oil

saturation will gradually decrease in the surrounding area near the borehole. Hence, this area should not be the target of

heating but rather the area further away from the borehole due to the fact that, in this area, the heat is only transferred to the

rock not to the oil. This will affect the injection volume of steam. Consequently, the cumulative steam oil ratio (CSOR) will

SPE-172212-MS

Smart Completion Design for Managing Steam Injection in CSS Process

Suranto, W. Bae, Sejong University, AK Permadi, Bandung Institute of Technology, and Son T. Dang, Sejong University

SPE-172212-MS 2

increase. This indicates that the process is inefficient. To overcome this weakness, CSS using smart completion has been

proposed in this paper.

This research, novel method to improving CSS, is based on the modification of the perforation interval. It will consist of two

parts, the first part is at the top and the second part is at the bottom (commingle perforation). The packer is installed between

the injection and production parts. An interval control valve (ICV) is installed in the tubing as a connector between

perforations and the inside of the tubing. In the steam injection period, the injection part is opened by opening the ICV, but

the production part is closed. In the soaking period, both of the 2 parts are closed. Then, in the production period, the ICV in

the injection part is closed and production part is opened correspondingly. The next cycle is repeated similarly. At the end of

well production life, the performance of both types of CSS (conventional and smart completion) will be evaluated and

compared.

Smart Completion The first smart completion was installed in August 1997 in the North Sea, Norway (Changhong, G, 2007). The principle of

smart well completion is to optimize the operation of the well by closing and opening of the perforations and, hence, to

maximize its production. Several equipment can be installed in a typical ICV such as pressure gauge and temperature sensor

to know the wellbore condition. These equipment allows operator to optimize the operation of the valves. For example, when

the pressures between the 2 perforation intervals are different, undesirable crossflow can occur. To prevent that problem, the

bottom valve should be closed from the surface via hydraulic or electronic line. In addition, temperature sensor provides

real-time monitor of temperature at the installed location.

When the valve is closed, it only isolates the path between the perforation or annulus and the inside of the tubing. It still

allows fluid to go through that area inside of the tubing, thus the production of fluid can be continuous. Figure 2 shows the

smart completion assembly and its two parts.

Figure 1 Smart well completion configuration (S. D. Mohaghegh, 2007)

Description of Reservoir Model The thermal reservoir simulator, STARS Version 2011, by Computer Modeling Group, was applied to construct reservoir

models and to investigate the performance of conventional and smart CSS processes. The reservoir model, which

representing a generic in Pertama-kedua Formation in Sumatra-Indonesia, is selected for this research and is described in

Table 1. The model consists of one vertical well in the center of a radial reservoir.

Perforation

Perforation

SPE-172212-MS 3

TABLE 1 PERTAMA/KEDUA RESERVOIR PROPERTIES (Gael, B.T. 1995)

Reservoir Properties

Value

Average depth, ft

500

Initial reservoir temperature, oF 100

Initial reservoir pressure, psi 100

Average net thickness, ft 120

Average porosity, % 0.34

Average permeability, mD 1500

kv/kh 0.5

Rock compressibility, 1/psi 5.7e-6

Average Oil density, oAPI 20

Oil viscosity at reservoir condition, cp 330

Oil viscosity at 432 oF , cp 8.2

Oil formation Volume factor at reservoir condition, RB/STB 1.02

Solution gas-oil ratio, SCF/STB 14

Residual oil saturation to water,% 0.25

Residual oil saturation to steam, % 0.1

Irreducible water saturation, % 0.40

Three phases relative permeability model Stone’s 2

Reservoir, underburden /overburden Volumetric heat capacity, BTU/ft3-

oF 33.2

Reservoir, underburden/overburden thermal conductivity, BTU/ft-day-oF 27.4

There are no gas cap and bottom water drive. The geomechanics processes are also ignored in this model. Due to limited

data, the porosity, permeability, oil saturation, and the other parameters are assumed to be homogeneous in the whole

reservoir. Oil column thickness is constant for all layers. The ratio of horizontal permeability and vertical permeability is 0.5.

The number of grid is 22 x 4 x 40 (i, θ, k), the grid size near wellbore is 3 ft and gradually increases toward the reservoir

boundary to reach a value of 90 ft, while the vertical grid size is kept constant at 3 ft. The injection steam quality is equal to

0.8 and the steam temperature is 432 oF. Figure 3 shows the idealization of the model. Conventional and smart completion

CSS processes are simulated using this reservoir model. In those processes, the steam injection pressure at the sand face is

constant (350 psi) and the maximum injection rate is 2000 stb/day. During the production period, the minimum bottom hole

pressure (BHP) is set to be 70 psi which is reasonable for pump operation.

Figure 2 Idealization of the 3D model

SPE-172212-MS 4

Result and Discussion

Comparison conventional and smart perforation CSS process

In the conventional CSS (left-hand side of Figure 3), the perforation interval is the same for both of the injection and

production periods. In this research, the steam is injected for 21 days, the well is then soaked for 5 days and is produced for 4

months after that. The durations of steam injection, soaking, and production periods are the same for both conventional and

smart completion CSS. The top of the perforation interval is 30 ft apart from the top reservoir to reduce heat loss to the

overburden. The perforation interval in Smart CSS is divided into two parts, one part is at the top and the other is at the

bottom as shown in the right-hand side of Figure 3. In the base case, the length of both of the 2 parts are approximately 30 ft

and the distance separating them is 30 ft. In the smart completion, when the valve (ICV) in one part is closed that part of the

perforation is correspondingly closed or isolated. In the conventional CSS, the length of perforation is 90 ft starting from the

bottom of the reservoir.

30 ft

90 ft

Reservoir

Packer

Inj. & Prod.Perforation

30 ft

30 ft

30 ft

30 ft

Inj. Perforation

ICV-P

ICV-I

Packer

Packer

Prod. Perforation

Reservoir

Figure 3 Conventional CSS perforation (left) and smart CSS perforation (right)

Injector 1Producer 1

0 100 200

0 100 200500

510

520

530

540

550

560

570

580

590

600

610

620

630

640

650

660

490

500

510

520

530

540

550

560

570

580

590

600

610

620

630

640

650

0.00 25.00 50.00 feet

0.00 10.00 20.00 meters

File: Duri_BC.irfUser: HPDate: 3/4/2014

Scale: 1:366.753153 Z/X: 1.00:1Axis Units: ft

100

133

166

200

233

266

299

332

366

399

432

Smart completion designTemperature (F) 2021-09-16 J layer: 1

Injector 1

Producer 1

0 100 200

0 100 200500

510

520

530

540

550

560

570

580

590

600

610

620

630

640

650

660

490

500

510

520

530

540

550

560

570

580

590

600

610

620

630

640

650

0.00 25.00 50.00 feet

0.00 10.00 20.00 meters

File: Duri__Mod.irfUser: HPDate: 3/4/2014

Scale: 1:366.753153 Z/X: 1.00:1Axis Units: ft

100

133

167

200

233

266

299

332

366

399

432

Smart completion designTemperature (F) 2021-09-16 J layer: 1

Figure 4 The temperature distribution at the end of the project life during the steam injection period

(Left: conventional CSS, right: smart completion CSS)

Figure 4 shows the temperature distribution in the reservoir for both conventional and smart completion cases. In

conventional CSS, steam was injected into the reservoir. The area around of the wellbore is soaked, then the well can be

produced. In this process, only steam in the front can contact the oil while the steam behind that front might not contribute

to the effectiveness of the process. Thus, its effectiveness will decrease as characterized by an increase in CSOR showed in

SPE-172212-MS 5

Figure 5. As previously mentioned, steam is injected and then is produced via the same perforation interval, thus it will be

difficult to penetrate further into the reservoir due to the fact that a large volume of condensate will form near the wellbore.

This requires a bigger volume of steam that leads to a larger CSOR.

While, the configuration of smart completion is quite different to conventional CSS. During the beginning of injection

period, steam will grow out around the injection perforation. After that, it will go up due to its low density. In the soaking

period, the steam will be condensed to become liquid. This fluid goes down because of gravity force and it will sweep the

crude oil. Because of the injection and production parts are separated, most volume of the steam can contact with crude oil

due to different ways of coming out from the wellbore. Therefore, the heat will has longer time in the reservoir. As a

consequence, the heat will be significantly adsorbed to the reservoir and the effectiveness of steam will be increased. In

addition, the injected fluid is not immediately drained from the reservoir it will add a significant pressure maintenance

benefits. As can be seen in Figure 5, the CSOR in smart completion is approximately 30% lower than that of conventional

CSS indicating that the smart completion is more effective compared to conventional approach.

Figure 5 Cumulative steam oil ratio vs. time in conventional and smart CSS processes

Figure 6 Cumulative steam injection vs. time in conventional and smart CSS processes

SPE-172212-MS 6

Even though the operation condition such as injection pressure and steam quality was the same, the drainage radius of

conventional CSS and smart perforation are approximately 100 ft and 200 ft (until the boundary of the model) respectively.

Due to the effect of constant pressure injection, the steam injection rate will be difference between conventional and smart

CSS. Figure 6 shows the cumulative steam injection in conventional and smart completion CSS. In the conventional CSS,

after one cycle the steam will follow the similar path to penetrate to the reservoir. In this process, the energy needed will be

slightly the same to the first cycle so that the cumulative steam injection curve will have a straight line characteristic. On the

other hand, the cumulative steam injection of the smart CSS will rapidly increase after 3 years as a result of different paths of

steam injection and oil production. In this process, steam will continue to penetrate further to the reservoir after production

period and it will not follow the same pattern like in conventional CSS. Because of that, the oil cumulative production will

be higher compared with the conventional CSS. Figure 7 shows the cumulative oil production vs. time and as can be seen,

the smart completion’s cumulative oil production can be 3.5 times higher than conventional CSS’s.

Figure 7 Cumulative oil production vs. time for both conventional and smart CSS processes

Effect of Interval Perforation

Interval perforation is very important in the design. If the injection perforation interval is wide, the steam will be easy to

penetrate to the reservoir; however, as a consequence, the distance between injection - production parts will be small. Hence,

the CSOR will increase because the steam is easy to move directly to the production perforation. Besides that, if the injection

interval is narrow, the steam will stay longer in the reservoir. That leads to CSOR decrease, but the steam injection rate will

also decrease. In addition, the cumulative oil production will not be satisfactory. Figure 8 to Figure 10 show a sensitivity

study of different lengths of injection and production intervals. As can be seen, the most effective length of injection and

production intervals are 15 ft and 15 ft, respectively. At this configuration, the CSOR will be the lowest.

In contrast, it will be different in the scenario of wide perforation intervals. If both of the injection and production intervals

are 45 ft, not only the steam will easily penetrate to the reservoir, but also the condensed water is very easy to move to

production intervals. Consequently, the pressure is rapidly dropped while the CSOR is increased. At the end of the

production period, the steam injection will increase because the crude oil has been swept far away from the borehole. The

area between oil saturated zone and the borehole will be filled by the steam makes it easy for it to move to the reservoir.

Technically, the optimum interval is the one that leads to a low CSOR and a favorable production. In this research, the base

case result is better than those of other scenarios. Economic is very important criteria to make decision but it is not included

in this research.

SPE-172212-MS 7

Figure 8 Cumulative oil production vs. time with different lengths of perforation

Figure 9 Effect of perforation length to cumulative steam oil ratio

Figure 10 Effect of perforation length to cumulative steam injection

SPE-172212-MS 8

Effect of soaking time The soaking time is very important because the latent heat must be transferred to the reservoir during this period. As

described above, the steam injection pressure and temperature are 350 psi and 432 oF, respectively. In order to get a good

heat transfer process, the temperature of production fluid should be maintained as low as possible. In this model, because the

minimum BHP is 100 psi, the temperature of production fluid must be less than 295 oF so that the latent heat can be

transferred.

Figure 11 to Figure 13 show the performances of smart completion CSS with various soaking times. The soaking time,

ranges between 1 to 5 days, has small effect on CSS performance. This indicates that the effectiveness of steam is almost the

same regardless of the soaking time. This also indicates that the temperature of production fluid is almost the same. As can

been seen in the Figure 11, the soaking time of 1 day results in slightly higher performance compared with different soaking

times of 4, 3, and 2 days. However, the steam injection volume is higher due to shorter soaking time. As a result, the

cumulative oil production will be slightly higher compared with the other scenarios. The operating condition should be

considered to choose which soaking time will become reasonable.

In the smart CSS, the soaking time has a small effect on the CSS performance because the injection fluid lasts longer in the

reservoir. Therefore, it will has enough time to transfer energy to the reservoir even though the soaking time is only 1day.

Figure 11 Cumulative steam oil ratio vs. time with different soaking times

Figure 12 Effect of soaking time to cumulative oil production

SPE-172212-MS 9

Figure 13 Effect of soaking time to cumulative steam injection

Conclusion Based on the above analysis, the smart completion CSS will be more favorable compared with conventional CSS. Simulation

results indicated that the effectiveness of steam and cumulative oil production will increase 30% and 3.5 times, respectively,

compared to that of conventional CSS. The selected injection and production perforation intervals are of the same length

with a big interval separating them is favorable. The soaking time does not significantly affect the smart completion CSS

performance.

Acknowledgements The authors would like to thank Hyun Dai energy & Resources CO.Ltd and Department of Energy and Mineral Resources

Engineering , Sejong University for support this research.

Nomenclature CSS = Cyclic Steam Stimulation

ICV = Interval Control Valve

CSOR = Cumulative Steam Oil Ratio

BHP = Bottom hole pressure

Reference:

Changhong G, T. Rajeswaran, N. Edson, 2007, A Literature Review on Smart-well Technology, SPE Production and

Operation Symposium Held in Oklahoma, SPE : 106011. http://dx.doi.org/10.2118/106011-MS

Computer Modelling Groups (CMG) Ltd. 2011, Stars Users Manual, Version 2011.20. Calgary, Alberta, Canada.

Faroug Ali S.M,”CSS-Canada’s Super Strategy for Oil Sands”, the Journal of Canadian Petroleum Technology, 1994.

http://dx.doi.org/10.2118/94-09-01

Gael, B.T, Gross, S.J, and McNaboe, G.J, 1995, Development Planing and Reservoir management in the Duri Steam Flood,

SPE 29668. http://dx.doi.org/10.2118/29668-MS

Hong KC., Steam Flood Reservoir Management: thermal enhanced oil recovery, Peen Well Publishing Company, 1994.

Mohaghegh S. D., 2007, Smart Completions, Smart Wells and Now Smart Fields; Challenges & Potential Solutions, West

Virginia University & Intelligent Solutions, Inc, SPE Distinguished Lecturer Series, SPE-120504-DL

Richard F. Meyer, Emil D. Attanasi, and Philip A. Freeman, 2007, Heavy Oil and Natural Bitumen Resources in Geological

Basins of the World, http://pubs.usgs.gov/of/2007/1084/OF2007-1084v1.pdf (downloaded, 12 January 2014).