1 SPE 113563

Copyright 2008, Society of Petroleum Engineers Inc. This paper was prepared for presentation at the 2008 SPE Indian Oil & Gas Technical Conference and Exhibition scheduled 4-6 March 2008 in Mumbai, India This paper was selected for presentation by an SPE Program Committee following review of information contained in a proposal submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to a proposal of not more than 300 words; illustrations may not be copied. The proposal must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435.

Abstract This paper presents the reservoir considerations, implementation and results of a new completion technology with the aim to improve ultimate recovery. The non-uniform production profile across the horizontal hole especially in the highly heterogeneous and fractured reservoirs can result in premature water production and lower ultimate recovery. PLT surveys were carried out in some horizontal wells which indicated non-uniform production profile across the horizontal holes. Therefore the need for production system as part of the completion was raised to control water production and to improve ultimate recovery. This completion technique will the low and high permeability intervals to contribute to flow was found to be the optimum option for this highly heterogeneous and fractured reservoir. Horizontal hole segmentation using ICD (Inflow Control Device) completion was found to be the optimum option to be tested as pilot in a new and an existing wells. The new well was expected to penetrate highly fractured area and the existing well is also located in highly fractured area. The ICD Equalizer system was installed in both wells to evaluate the technique. The surface testing results of the re-completed well indicated a drop in the well water cut from 7% to traces. PLT survey was carried out in both wells and indicated uniform production profile across the horizontal section. Therefore the reliability of the technique was proved and these jobs were considered as the first application in United Arab Emirates. With field scale implementation, the reservoir simulation and economic analysis revealed an improved oil recovery of 1% and higher NPV.

Introduction This paper presents the reservoir considerations, implementation and results of the new completion technology to improve ultimate recovery of an oil field in the United Arab Emirates. Horizontal well technology has become an established method of drilling conventional wells due to their improved recovery efficiency, reservoir drainage and delayed undesirable fluids (water & gas). However non-uniform production profile across the horizontal hole especially in the highly heterogeneous and fractured reservoirs can result in premature water production. This may cause bypassed oil, lower ultimate recovery and therefore decrease in profitability. The main characteristic of this reservoir is the presence of a complex fracture network within the highly heterogeneous matrix system. Both matrix and fracture systems play an important role in the production mechanism of the reservoir. Additionally, the reservoir is characterized by the presence of Sucrosic Dolomite rock (mainly in the South part of the middle reservoir unit) that significantly enhances matrix permeability further. Matrix permeability ranges from 0.01 mD to 12 Darcy with the average in excess of 100 mD. The fractures are described as fracture corridor system (or fracture swarms) that show two major trends, namely N40E and N70E. Fracture swarms/sub-seismic faults are structural features extending laterally over several hundreds meters and sometimes over several kilometers (Figure 1). With water movement towards well-bore, sweep efficiency is affected and recoverable oil is impacted. This progress in well water cut and consequently fields water production increase will cause loss of production and reserves. The shortening of well life cycle is directly linked to the wells water production and its source. In this field, once the well water cut reaches 50%, the constrained well production rate of 2,000 stb/d will no longer be maintained and the well has to be workedover or new wells to be drilled to be able to sustain the field production capacity. Therefore the need for a production system as part of completion strategy was raised with the aim to improve production efficiency.

SPE 113563

New Completion Technology As A Catalyst to Improve Oil Recovery Salem El-Abd, SPE, Abdel Hameed Amiri, SPE, Ashraf Keshka, SPE, Salem Al-Bakr, SPE, Saif Al Arfi, SPE (ADCO), Magdi El-Asmar, SPE (Baker Oil Tools)

2 SPE 113563

Business Case A multidisciplinary team was formed to investigate possible techno-economical solution to the described problem of non-uniform production profile and water progress across the horizontal sections. The following elements comprise the business case and findings: Reservoir Consideration & Business Need The formation, which is the pay zone in this Field, is a complex fractured carbonate reservoir exhibiting considerable lateral and vertical lithological changes and consequently variations of reservoir characteristics. Both matrix and fracture systems play an important role in the production mechanism of the reservoir. The reservoir is subdivided into three reservoir units namely Unit Unit1, Unit2 and Unit3 (Figure 2). At the early stage of the development of the field, the significance of fractures in this reservoir was not recognized. However, the latest fracture study which was carried out by integrating all available data FMS/ FMI, Cores, Seismic and production data revealed that this reservoir is moderately to highly fractured reservoir. The fracture network is composed of fracture-swarm zones. The width of such zones ranges between 50 to 100m. The fracture swarms are oriented in two main directions: N40E and N70E. No diffuse fracturing can be characterized. This means that this reservoir is weekly fractured between the fracture-swarms zones. PLT surveys were carried out in some horizontal wells and all of them indicated non-uniform production profile across the horizontal holes. The following are the results of the horizontal PLT surveys in some wells:- A PLT survey was carried out in Well A to determine

the oil and water production profiles of the horizontal open hole section, to define the produced water entry points and to measure the base sigma log for saturation monitoring. The well is located in a highly fractured area as presented in Figure 3. The results of the survey (Figure 4) indicated non-uniform production profile across the horizontal section and most of the oil and water producing intervals are in line with the fracture study. The water cut reaches some 50% in this well and it was planned to be horizontalized into another direction but after the completion was retrieved, the casing corrosion log indicated that the casing is severely corroded. Therefore the well was plugged and abandoned and a replacement well was drilled.

A PLT survey was carried out in Well B, to determine

the oil and water production profiles of the horizontal open hole section, to define the produced water entry points and to measure the base sigma log for saturation monitoring. The results of the survey (Figure 5) indicated that a short interval of some 40 ft is contributing 70% of the total oil production and some 80% of the water production. The high oil and water

production rates from this short interval, the sharp increase in temperature and the increase in Gamma ray are due to the presence of large fracture as supported by the fracture study (Figure 6).

A PLT survey was carried out in Well C, to determine

the production profile across the horizontal hole and to measure the base sigma log for saturation monitoring. Although this well is located in an area which considered homogeneous, the PLT results (Figure 7) indicated that the first half of the horizontal section is contributing all production and the second half of the hole is contributing nothing.

Based on the above PLT results, the need for a completion technique to achieve uniform production profiles across the horizontal holes was raised with the aim to improve the reservoir sweep efficiency, achieve longer production plateau of the wells by controlling the rate of water cut development and consequently increasing the overall field ultimate recovery. Technical Options & Alternatives Water shutoff techniques such as mechanical and chemical were investigated and it was found that both techniques were considered to be inefficient in the highly fractured reservoirs. The technique of controlling the flow and establishing uniform production profile across the horizontal hole will allow the low and high permeability (fractures) intervals to contribute to flow. Using ICD (Inflow Control Device) was found to be the optimum option to be tested as a pilot in a new well (Well D). Based on the latest fracture study, this new well is expected to be drilled in a highly fractured area especially the second half of the horizontal section (Figure 8). Market survey & Technique Evaluation Through market survey different vendors were invited to introduce their technologies and it was found that three technologies have similar functionality and can provide in theory the required effect on well-bore uniform production profile. The technique of controlling the flow and establish uniform production profile across the horizontal hole which allow the low and high permeability (fractures) intervals to contribute to flow was found to be the optimum option for this highly fractured reservoir. The following were considered in the technique evaluation: Features, Benefits & Applications Technical Specifications & Testing Risk Assessment & Mitigation Case Histories, Success Ratio & Experience Sharing

Techno - Economic Assessment Reservoir simulation runs (using the existing Eclipse model) were carried out to evaluate the benefits of installing the Equalizer system in the new well (Well D) which was planned to be drilled in November 2006. The results indicated an incremental oil of 1.4 MMstb over the well life can be achieved by running the Equalizer system compared with barefoot completion. Moreover, to evaluate the impact of

3 SPE 113563

installing the Equalizer system on field scale implementation, it was assumed that the Equalizer system will be installed in 70% of the planned future wells which are expected to penetrate fractures. The results indicated an incremental oil recovery of some 36 MMstb, which represent 1% of the original oil in-place, can be achieved by running the Equalizer system compared with barefoot completion. Moreover, NetTool simulation runs were carried out to determine the required number of ICDs to achieve uniform production profile. In order to justify the expenditure associated with the Equalizer (ICD), a detailed economic analysis was carried out based on the planned well production forecasts using ADCOs economic guidelines. The case with Equalizer was compared to the barefoot completion case on a single well model and the economics calculations indicated the following incremental economics indicators:- NPV @ 8 % Discount Rate : 1.9 Million $ UTC @ 8 % Discount Rate : 4.4 $/bbl PIR @ 8 % Discount Rate : 4 Incremental Oil : 1.4 MMstb For field wide implementation, it was assumed that the ICD will be installed in 70% of the planned future wells as issued in the Full Field Development Plan. The economics calculations indicated the following incremental economics indicators:- NPV @ 8 % Discount Rate : 43.9 Million $ UTC @ 8 % Discount Rate : 2.9 $/bbl PIR @ 8 % Discount Rate : 6.7 Incremental Oil : 36.3 MMstb Operational feasibility The operational procedures were discussed within a multidisciplinary team and it was decided to run an image log in well D prior to the ICD completion to assist in defining the required number and locations of ICDs & MPas packers for the purpose of achieving uniform production profile and controlling water progress. Based on the reservoir model permeability profile, the original design was to run 10 ICDs and 9 MPas packers with possibility to reduce it as deemed necessary. Moreover, testing procedures and the involved risks along with its mitigations were also discussed to ensure proper implementation and safety precautions are met in accordance to industry standards. Technique Implementation & Evaluation Horizontal hole segmentation using ICD (Inflow Control Device) completion was found to be the optimum option to be tested as pilot in a new and an existing wells. The new well was expected to penetrate highly fractured area and the existing well is also located in highly fractured area. The implementation and evaluation of the ICD completion are discussed below:

In February 2007, well D was drilled and completed as a Unit 2 single lateral horizontal oil producer with 2,000 horizontal hole. Inflow Control Devices (ICD) with Mpas packers were installed (11 ICDs and 11 MPas Packers) in the horizontal section with the aim to achieve uniform production profile along the horizontal section and reduce water production. The well was completed with 3 single completion string equipped with ESP and Y-tool. The final down hole completion string is presented in Figure 9. The well was tied-in to the production station and started production in March 2007. The initial testing results indicated that the well produced some 2,100 stb/d of dry oil. A PLT survey was carried out to confirm the reliability of the technique in achieving uniform production profile across the horizontal hole. The PLT interpretation indicated uniform production profile across the horizontal section (Figure 10).

In April 2007, the ESP failed in well B due to short circuit

in the downhole string after 9 years since commissioning. In May 2007, the well was worked over to replace the ESP. NetTool simulation runs (Figure 11) were carried out to determine the optimum number of ICDs and MPas packers to be installed. Based on these runs, 11 ICDs and 5 MPas Packers were recommended to be installed to achieve better production profile compared with the open hole completion. During the workover the opportunity was taken and a new completion string using Inflow Control Device (ICD) in the horizontal section was installed to achieve better production profile along the horizontal section and reduce water production. The final down hole completion string is presented in Figure 12. The well was tied-in and produced some 2,500 stb/d with traces of water cut compared to some 7% water cut before workover. A PLT survey was carried out with 2 different production rates (2,000 and 3,000 stb/d) to evaluate the impact of the ICD on the well performance in case of high production rates. The PLT interpretation (Figure 13) indicated uniform production profile across the horizontal hole with ICD completion compared with the one with barefoot completion which was carried out in 2002. Moreover, the comparison between the production profiles at different production rates showed minor change of the well performance in the presence of ICD completion. The PLT results are inline with the NetTool simulation results.

The results from the two ICD completions were positive, as the PLT results indicated better inflow profile compared to the existing openhole completions. Both wells (Well B & D) have been considered as an economic success and will recover the targeted oil reserves. The installations of the ICD completions were successfully implemented in both wells as a result of proper well planning and wellbore cleaning. Field-Scale Implementation The Full Field Development plan is driven by optimizing ultimate recovery while maintaining / developing sustainable production capacity throughout longer production plateau

4 SPE 113563

length. A comprehensive techno-economical field development plan covering the optimum development scheme considered the application of ICD as part of enhancing production efficiency. Different development options were studied along with the impact of ICD on sweep efficiency and in-fill drilling program. The main conclusion from this work was that the application of ICD helps improving the field economics by optimizing ultimate recovery and can assist in optimizing the future development drilling & workover program. Conclusions & Recommendations 1. The reliability of the ICD completion to achieve uniform

production profile across the horizontal section was proved, as both wells showed uniform and better inflow profile compared to the existing open hole conventional completions.

2. These jobs were the first application of this technique in United Arab Emirates (UAE).

3. The simulation results are inline with the PLT results. 4. The installations of the ICD completions were

successfully implemented in both wells as a result of proper well planning and wellbore cleaning.

5. The ICD technique proved effective in minimizing well water cut as indicated by the PLT (Well B). The latest well test results showed traces of water production (almost one year since the installation of the ICD completion).

6. It is recommended to install the ICD completion in some 70% of the future wells (35 wells). This will improve the field ultimate recovery by 1% (36 MMstb).

Nomenclature

ICD = Inflow Control Device PLT = Production Logging Tool NPV = Net Present Value

UTC = Unit Technical Cost PIR = Profit Investment Ratio ESP = Electrical Submersible Pump STB = Stock Tank Barrel

Acknowledgement We wish to thank ADNOC for giving the permission to publish the result of this field case. Also, we are grateful for continuous support provided by ADCO Management during the course of the study, from building the business case to implementation.

References Jody R. Augustine An Investigation of Economic Benefit on Inflow Control Devices on Horizontal Well Completions Using a Reservoir-Wellbore Coupled Model SPE 78293 (October 2002).

N 4 0 E

N 7 0 E

Figure 1 Fracture Maps Shown the Two Main Directions (N40E and N70E)

Figure 2 Reservoir Units

Figure 3 Well A Location on the fracture map

UPP

ERRes

ervo

irL

O W

E R

Res

ervo

ir

MEMBERS RESERVOIRUNIT

Unit1

Unit2

Unit3

Reservoir Units

UPP

ERRes

ervo

irL

O W

E R

Res

ervo

ir

MEMBERS RESERVOIRUNIT

Unit1

Unit2

Unit3

Reservoir Units

5 SPE 113563

Figure 4 Well A PLT Results

Figure 5 Well B Location on the fracture map.

Figure 6 Well B PLT Results

Figure 7 Well C PLT Results.

Sy-50 Proposed Surface, Landing Point and Bottom Hole Locations with Respect to Fractures at Simsima R2

Figure 8 Planned Location of Well D

Figure 9 Well D Down hole Completion

Sy-24 P

LT/Fla

gship (

Produc

tion Pro

file)

Sy-24 P

LT/Fla

gship (

Produc

tion Pro

file)

Well D

6 SPE 113563

Figure 10 Well D PLT Results

Figure 11 Well B NetTool Simulation Results

Figure 12 Well B Down Hole Completion

Figure 13 Well B PLT Results Before and after ICD installation

Zonal Cumulative

Well D PLT Results, 2007

Unit 2 1 32

E q u a l i z e r N u m b e r D e p t h

C a l c u l a t e d o i l F l o w R a t e b b l / d

1 6 3 6 7 1 4 2

2 6 1 2 8 1 2 2

3 5 8 0 5 1 7 6

4 5 6 0 6 1 7 0

5 6 4 7 6 2 1 5

6 5 3 8 9 1 7 0

7 5 2 6 9 1 3 8

8 5 1 0 7 1 4 5

9 4 9 4 3 1 4 0

1 0 4 7 7 7 2 5 0

1 1 4 5 8 0 3 3 0

S y - 5 0 P L T ( P o l a r i s ) R e s u l t s , 2 0 0 7

Well B

21%

20%

21%

12%

13%

2%

2%

1%

3%

3%

3%

18%

20%

20%

13%

13%

2%

2%

2%

3%

3%

4%

Rate1, ICD, 2007 Rate2, ICD, 2007

Bare Foot, 2002

5 % O

,0 %

W8%

O ,7 %

W

15% O

,5%

W70 %

O ,80 %

W

3 % O

,8 % W

Well B PLT Results

21%

20%

21%

12%

13%

2%

2%

1%

3%

3%

3%

18%

20%

20%

13%

13%

2%

2%

2%

3%

3%

4%

Rate1, ICD, 2007 Rate2, ICD, 2007

Bare Foot, 2002

5 % O

,0 %

W8%

O ,7 %

W

15% O

,5%

W70 %

O ,80 %

W

3 % O

,8 % W21%

20%

21%

12%

13%

2%

2%

1%

3%

3%

3%

18%

20%

20%

13%

13%

2%

2%

2%

3%

3%

4%

Rate1, ICD, 2007 Rate2, ICD, 2007

Bare Foot, 2002

5 % O

,0 %

W8%

O ,7 %

W

15% O

,5%

W70 %

O ,80 %

W

3 % O

,8 % W21%

20%

21%

12%

13%

2%

2%

1%

3%

3%

3%

21%

20%

21%

12%

13%

2%

2%

1%

3%

3%

3%

18%

20%

20%

13%

13%

2%

2%

2%

3%

3%

4%

18%

20%

20%

13%

13%

2%

2%

2%

3%

3%

4%

Rate1, ICD, 2007 Rate2, ICD, 2007

Bare Foot, 2002

5 % O

,0 %

W8%

O ,7 %

W

15% O

,5%

W70 %

O ,80 %

W

3 % O

,8 % W

Well B PLT Results

7 SPE 113563

21%