Zonal Isolation in a U-shaped Well Using Ct&Tractor

8/9/2019 Zonal Isolation in a U-shaped Well Using Ct&Tractor

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Copyright 2004, Society of Petroleum Engineers Inc.

This paper was prepared for presentation at the SPE/ICoTA Coiled Tubing Conference andExhibition held in Houston, Texas, U.S.A., 23–24 March 2004.

This paper was selected for presentation by an SPE Program Committee following review ofinformation contained in a proposal submitted by the author(s). Contents of the paper, aspresented, have not been reviewed by the Society of Petroleum Engineers and are subject tocorrection by the author(s). The material, as presented, does not necessarily reflect anyposition of the Society of Petroleum Engineers, its officers, or members. Papers presented atSPE meetings are subject to publication review by Editorial Committees of the Society ofPetroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paperfor commercial purposes without the written consent of the Society of Petroleum Engineers isprohibited. 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 conspicuousacknowledgment 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 wassuccessfully installed in order to shut off a gas breakthrough inthe 130 degrees deviated reservoir section of a “U shape/Fish

hook” sub sea oil producer in the Njord field. Coiled tubingwith an internal electric line in combination with a tandemfluid 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 floatingdrilling and production unit. The well is an oil-producer in theTilje 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 thewell in order to reduce the gas to oil ratio (GOR). The chosenmethod was to install a purpose designed straddle packerassembly utilizing coiled tubing and tractor.

Job design

Based on computer simulations, it soon became clear thatit would not be possible to reach the desired depth using coiledtubing and conventional “extended reach” techniques alone.

Computer simulations using reduced friction coefficients

and/or altered fluid densities only improved results marginallyand indicated that the 2-in” (optimized taper) coiled tubing at best would go into a lockup 174 meters away from targetdepth. Computer simulations using 2-3/8-in” coiled tubingalso showed similar results with a little added penetration.

CoilCAT* software was used for modeling of tubing forces inthe well.

Based on these simulations a coiled tubing tractor (Fig 3)

was recommended to extend the conveyance reach to thetarget depth. The tractor supplier stated that 3000 lbs pullforce would be available from the fluid driven coiled tubingtractor. Computer simulations performed using 3000 lbs

(13kN) pull force on the straddle assembly in combinationwith the available coiled tubing push, indicated that bottom of

well could be reached. (Fig 4 presents plot of simulation resultwith and without tractor). This would be the first timeelectrical tools were used in combination with the fluiddriven tractor.

A new adapter sub was required to use tractor with e-lineintegrated for surface data readout. The adapter design was

based on an existing coiled tubing cable head design withadded functionality to allow higher flow rates directed down through the emergency disconnect section instead of thenormal 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 laterused when setting up the tools and tractor for the operation.

To be able to run the required tool string (Fig 5) for thestraddle packer assembly the tractor top connector andcompensator 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 notaccidentally lost in hole, the top adapter thread on the settingtool was changed to a CAL-B connection, which is larger andwill 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 was6.094-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,

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



2 SPE 89522

where the first run releases the lower packing unit. The secondrun releases the upper packing unit and the slips section. Thestraddle can then be retrieved.

Job execution

A gauge run with a “dummy straddle” was performed. Areal 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 wellfrom 4196 m to 4276 m.

When running the straddle packer assembly into the toesection of the well, lock-up was experienced at 4160 meters

MD at 113 degrees inclination. This was fully in accordancewith simulated lock-up depth. The tractor was activated by

pumping 140 liters per minute, successfully conveying thestraddle assembly down (or rather up) to 4312m MD at 130degrees inclination. The straddle packer assembly was then

pulled back to the setting interval (Fig 7). Predicted coiledtubing 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 ina well under live conditions, ending up with a 80 m straddle inthe well set across the planned interval (Table 1&2).

Presentation of Data and Results

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 GORwas reduced from 3000 to 1600 Sm

3/Sm

3 and the oil

production was boosted to 1500 Sm3/D. Investment wasreturned 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 inclinatedwell section.

The combination of coiled tubing, well tractor and mediumexpansion 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.

References

1. Haci M, and Hallundbaek J.: “New Coiled Tubing Well

Tractor® Extends Lateral Reach,” paper SPE 68887 presentedat 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. 4193.96 mRKB

Element Upper Straddle packer: 4195.26 mRKB

Element Lower Straddle packer: 4275.00 mRKB

Bottom of Straddle: 4277.28 mRKB

Total isolated zone: 79.74 m

Table 2 - Main dimensions of the straddle;

Description Max OD Min ID

Upper Straddle Packer 5.50 in 3.64 in

3-1/2-in Spacer Pipe 4.25 in 2.992 in

Lower Straddle Packer 5.50 in 2.75 in

Total weight of Coiled Tubing BHA: 2000 kg in air

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





4 SPE 89522

Fig 3 Well Tractor:

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

Coiled Tubing Weight Indicator Load

-15000,00

-10000,00

-5000,00

0,00

5000,00

10000,00

15000,00

20000,00

25000,00

30000,00

35000,00

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

W e i g h t I n d i c a t o r L o a d - l b

Weight Indicator Load POOH lbf

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



SPE 89522 5

Fig 5 Tool string: Fig 6 Straddle packer assembly:

2" CT w/ E-line

CT End connector

Cable Head

Flow Release Tool

Straight Bar

Tractor # 1

Tractor # 2

Casing Collar Locator

Setting Tool

Adapter kit

Upper Packer w/Slips

3-1/2" Spacer Pipe

Lower Packer wo/Slips

Perforated bottom sub

Magnet

Wire Brush

Magnet Sub

Brush

Perforated Bottom Sub

Lower Straddle Packer

Shear-Release kit

1-3/8" Inner String

3-1/2" Spacer Pipe

Upper Straddle Packer

Adapter kit

Hydrostatic Setting Tool



6 SPE 89522

Fig 7 Actual job parameters:

Fig 8 Actual coiled tubing weight parameters compared to simulated:

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Zonal Isolation in a U-shaped Well Using Ct&Tractor