SPE Abstract. Introduction

SPE 89522 Zonal Isolation in a U-shaped Well using Coiled Tubing and Well Tractor® T Saelensminde, SPE/Hydro O&E, H. F. Schjott/Hydro O&E, H.M. Koldal...
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SPE 89522 Zonal Isolation in a U-shaped Well using Coiled Tubing and Well Tractor® T Saelensminde, SPE/Hydro O&E, H. F. Schjott/Hydro O&E, H.M. Koldal/Schlumberger, T.Skeie/Welltec, T.O. Meberg, SPE/PI Intervention

Copyright 2004, Society of Petroleum Engineers Inc. This paper was prepared for presentation at the SPE/ICoTA Coiled Tubing Conference and Exhibition held in Houston, Texas, U.S.A., 23–24 March 2004. 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 An 80m long retrievable “one-run” straddle assembly was successfully installed in order to shut off a gas breakthrough in the 130 degrees deviated reservoir section of a “U shape/Fish hook” sub sea oil producer in the Njord field. Coiled tubing with an internal electric line in combination with a tandem fluid driven tractor was used to convey the straddle assembly. Introduction Njord is a sub sea completed oil field operated by Hydro, located offshore northwest Norway. Njord “A” is a floating drilling and production unit. The well is an oil-producer in the Tilje formation, completed with a 7-in” production tubing and a 7-in” perforated liner (Fig 1&2). The objective was to isolate selected intervals in the reservoir section at 130 degrees inclination in the “toe” of the well in order to reduce the gas to oil ratio (GOR). The chosen method was to install a purpose designed straddle packer assembly utilizing coiled tubing and tractor.

Job design Based on computer simulations, it soon became clear that it would not be possible to reach the desired depth using coiled tubing and conventional “extended reach” techniques alone. Computer simulations using reduced friction coefficients and/or altered fluid densities only improved results marginally and indicated that the 2-in” (optimized taper) coiled tubing at best would go into a lockup 174 meters away from target depth. Computer simulations using 2-3/8-in” coiled tubing also showed similar results with a little added penetration.

CoilCAT* software was used for modeling of tubing forces in the well. Based on these simulations a coiled tubing tractor (Fig 3) was recommended to extend the conveyance reach to the target depth. The tractor supplier stated that 3000 lbs pull force would be available from the fluid driven coiled tubing tractor. Computer simulations performed using 3000 lbs (13kN) pull force on the straddle assembly in combination with the available coiled tubing push, indicated that bottom of well could be reached. (Fig 4 presents plot of simulation result with and without tractor). This would be the first time electrical tools were used in combination with the fluid driven tractor. A new adapter sub was required to use tractor with e-line integrated for surface data readout. The adapter design was based on an existing coiled tubing cable head design with added functionality to allow higher flow rates directed down through the emergency disconnect section instead of the normal circulation path into the coiled tubing annulus. A test of the new cable head adapter with tractor was performed onshore to verify the flow-through characteristics, disconnect functionality, tractor performance and electrical integrity. The measured parameters from the test were later used when setting up the tools and tractor for the operation. To be able to run the required tool string (Fig 5) for the straddle packer assembly the tractor top connector and compensator were re -designed. Special attention was given to the connection between the setting tool and the casing collar locator. On standard tools, this is a relatively weak connection, mainly meant for tools to be run on wireline. In order to ensure that tools were not accidentally lost in hole, the top adapter thread on the setting tool was changed to a CAL-B connection, which is larger and will give more resistance to bending forces that would occur during the run in and setting operations. A tandem tractor configuration was required to achieve required pull force based on the available flow rate. The packers at each end of the straddle packer assembly (Fig 6) were custom-made to special outer diameter of 5.5-in” in order to pass a 5.75-in AOF nipple and several doglegs in the well. The internal diameter of the packer setting area was 6.094-in. It was identified that the bottom hole assembly could become heavy and therefore difficult to get to the target depth. Based on simulations, a 3-1/2-in” 9.2pounds per foot spacer pipe was selected. The straddle packer assembly was selected to be fully retrievable. Retrieval of the straddle is achieved in two runs,

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where the first run releases the lower packing unit. The second run releases the upper packing unit and the slips section. The straddle can then be retrieved. References Job execution A gauge run with a “dummy straddle” was performed. A real time surface readout production log was then run to determine the exact interval of the gas breakthrough. Evaluation of the log concluded that 66% of the gas was produced from the perforations in the “toe” section of the well from 4196 m to 4276 m. When running the straddle packer assembly into the toe section of the well, lock-up was experienced at 4160 meters MD at 113 degrees inclination. This was fully in accordance with simulated lock-up depth. The tractor was activated by pumping 140 liters per minute, successfully conveying the straddle assembly down (or rather up) to 4312m MD at 130 degrees inclination. The straddle packer assembly was then pulled back to the setting interval (Fig 7). Predicted coiled tubing forces versus experienced parameters are explained in attached plot (Fig 8). An electrically operated hydrostatic setting tool was used to set the straddle packer assembly, being the first time this particular combination of tools has been successfully placed in a well under live conditions, ending up with a 80 m straddle in the well set across the planned interval (Table 1&2).

1. Haci M, and Hallundbaek J.: “New Coiled Tubing Well Tractor® Extends Lateral Reach,” paper SPE 68887 presented at the SPE/ICoTA Coiled Tubing Roundtable held in Houston, Texas, 7– 8 March 2001.

Tables Table 1- Depths of the installed straddle; Top of Straddle @ 130 deg. Dev. Element Upper Straddle packer: Element Lower Straddle packer: Bottom of Straddle:

4193.96 4195.26 4275.00 4277.28

mRKB mRKB mRKB mRKB

Total isolated zone: 79.74 m

Table 2 - Main dimensions of the straddle; Description Upper Straddle Packer 3-1/2-in Spacer Pipe Lower Straddle Packer

Max OD 5.50 in 4.25 in 5.50 in

Min ID 3.64 in 2.992 in 2.75 in

Presentation of Data and Results Total weight of Coiled Tubing BHA: 2000 kg in air Prior to this intervention, the oil production varied between 0 and 800 Sm3 /D with the well periodically shut in due to gas processing limitations. The result of the intervention was encouraging: The GOR was reduced from 3000 to 1600 Sm3 /Sm3 and the oil production was boosted to 1500 Sm3 /D. Investment was returned within in 35 days by the increased oil production.

Conclusions It is proven that we can plan and prepare for a “one run” placement of an 80m straddle in a 130 degrees inclinated well section. The combination of coiled tubing, well tractor and medium expansion packer technologies was the key element to this success where oil production was restored. Acknowledgments The authors would like to thank Hydro Oil & Energy and the license partners: Mobil Development Norway AS, OER Oil AS, Petoro AS, Paladin Resources Norge AS, Ruhrgas Norge AS and Gaz de France Norge AS for permission to publish this paper. We would also like to thank all personnel and suppliers involved in making this project a success.

"An asterisk (*) in this publication denotes a mark of Schlumberger."

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Figures Fig 1 Well sketch:

Fig 2 Section of reservoir:

Ile Ror Tilje 3 Tilje 2 Tilje 1

Viking/Not

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Fig 3 Well Tractor:

Fig 4 Simulation results (overlay tractor/no tractor):

Coiled Tubing Weight Indicator Load

35000,00 30000,00

Weight Indicator Load - lbf

25000,00 20000,00 15000,00 10000,00 5000,00 Weight Indicator Load POOH lbf 0,00

Weight Indicator Load RIH (tractor) lbf Weight Indicator Load RIH (no tractor) lbf

-5000,00 -10000,00 -15000,00 0,00

500,00 1000,00 1500,00 2000,00 2500,00 3000,00 3500,00 4000,00 4500,00 5000,00 Measured Depth of Tool String - m

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Fig 5 Tool string:

Fig 6 Straddle packer assembly:

2" CT w/ E-line CT End connector Cable Head Flow Release Tool

Hydrostatic Setting Tool

Straight Bar

Adapter kit Tractor # 1

Tractor # 2

Casing Collar Locator

Upper Straddle Packer

Setting Tool

Adapter kit

3-1/2" Spacer Pipe

Upper Packer w/Slips

1-3/8" Inner String

3-1/2" Spacer Pipe

Lower Straddle Packer

Lower Packer wo/Slips Perforated bottom sub

Shear-Release kit Perforated Bottom Sub

Wire Brush

Brush Magnet

Magnet Sub

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Fig 7 Actual job parameters: Norsk Hydro Run 10 09.09.2003

Acq Panel Plot - Post Job 300 Stop CT due to lock- up

Continue run CT in hole

Stop tractor and CT

Set straddle

4450

Pull CT out of hole

Pull up to setting depth

Activate tractor

4350 250

Circ Pres

20050

CT Weight

150

CT depth - m

4150 4050 3950 3850

10050

3750

100 3650 3550 50 09:30:09

10:07:39

10:45:09

11:22:39

50 12:00:09

Time - hh:mm:ss

Fig 8 Actual coiled tubing weight parameters compared to simulated:

40000

Run 10 09.09.2003

Tubing Forces

Averaged Weight - lbf

30000

20000

10000

0

Averaged weight during run -10000

Simulated pickup Simulated slackoff

-20000 -1000

0

1000

2000

Corrected Depth - m

3000

4000

5000

Corr Depth - m

200

4250

CT Weight - lbf

Pressure - bars

30050