SEGMENTED BOND TOOL - A NEW GENERATION CEMENTBOND LOGGING DEVICE

J.H. TYNDALL

this article begins on the next page FFPETROLEUM SOCIETY OF CIM/SOCIETY OF PETROLEUM ENGINEERS PAPER NO. CIM/SPE 90-115 THIS IS A PREPRINT - SUBJECT TO CORRECTION SEGMENTED BOND TOOL - A NEW GENERATION CEMENT BOND LOGGING DEVICE BY J.H. Tyndall Atlas Wireline Services PUBLICATION RIGHTS RESERVED THIS PAPER IS TO BE PRESENTED AT THE INTERNATIONAL TECHNICAL MEETING JOINTLY HOSTED BY THE PETROLEUM SOCIETY OF CIM AND THE SOCIETY OF PETROLEUM ENGINEERS IN CALGARY, JUNE 10 TO 13,1990. DISCUSSION OF THIS PAPER IS INVITED. SUCH DISCUSSION MAY BE PRESENTED AT THE MEETING AND WILL BECONSIDERED FOR PUBUCATION IN CIM AND SPE JOURNALS IF FILED IN WRITING WITH THE TECHNICAL PROGRAM CHAIRMAN PRIOR TO THE CONCLUSION OF THE MEETING. ABSTRACT A new cement integrity tool has been developed, the Seg- mented Bond Tool (SBT), which affords a complete cement bond analysis in onc@ logging pass. An array of transmitter- receivers, mounted on six pads, are utilized to extract quantita- tive measurements of the cement bond in six 60 degrees seg- ments around the borehole. In addition, by effectively mounting the transmitters and receivers in contact with the casing wall throughthe use of pads, many of the problems common to the standard mandrel-type tools are effectively eliminated. Expefi- mental laboratory tests indicate that angular resolution of the tool is 60 degrees as expected and that channels as small as 15 degrees can be detect-.ed. From conception ()f this new generation CBL to final product, several rigid parameters were demanded. Briefly these are: 1. Ease of interpretation. 2. Eliminate ambiguity of conventional bond logs by quantita- tively depicting tlie bond condition around thecasing (i.e. channelling). References and illustrations at end of paper. 115-1 3. Complete data acquisition in one logging pass in all casing sizes4-1/2" to 13-5/8"in bothvertical anddeviatedwellbores. 4. Be unaffected by gasified wellbore fluids, fast formation and slight tool decentralization. The purpose of this paper is to detem-iine the success of the SBT in fulfilling these goals. Presented here are four Canadian examples from widely varied areas having casing strings ce- mented withvarious slurries. INTRODUCTION As discussed in Lester's Paper (CWLS 1989) and as summa- fized below, the evolution of cement bond logging has resulted in four distinct tool types: 1. Standard Tool - Utilizes a single transmitter and dual receivers usually mounted at 3 and 5 foot intervals, with the amplitude measured at the 3 foot interval. Attenuation is calculated from this amplitude. The VDL is derived from the 5 foot spacing (Pardue et al 1962). The data collected is effected by tool centralization, wellbore fluidcondition, transducer variations, fast formations, and calibration problems.

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PETROLEUM SOCIETY OF CIM/SOCIETY OF PETROLEUM ENGINEERS PAPER NO_ CIMISPE 90-115

THIS IS A PREPRINT - SUBJECT TO CORRECTION

SEGMENTED BOND TOOL -A NEW GENERATION CEMENT BOND

LOGGING DEVICE

BY J.H. Tyndall

Alias W1rolino Services

PUBLICATION RIGHTS RESERVED THIS PAPER IS TO BE PRESENTED AT THE INTERNATIONAL TECHNICAL MEETING JOINTLY HOSTED BY THE

PETROLEUM SOCIETY OF CIM AND THE SOCIETY OF PETROLEUM ENGINEERS IN CALGARY, JUNE 10 TO 13, 1990. DISCUSSION OF THIS PAPER IS INVITED. SUCH DISCUSSION MAY BE PRESENTED AT THE MEETING AND WILL BE CONSIDERED FOR PUBUCATION IN CIM AND SPE JOURNALS IF FILED IN WRITING WITH THE TECHNICAL PROGRAM CHAIRMAN PRIOR TO THE CONCLUSION OF THE MEETING.

ABSTRACT

A new cemem integrity [001 has been developed. the Seg­memed Bond Tool (SBT), which affords a complete cement bond analysis in one logging pass. An array of [l"ansmirrer­receivers, mounted on six pads, are utilized to exrraCl quantita­tive measurt:ments of the Cement bond in six 60 degrees seg­ments around the borehole. In addition, by effectively mounting the transmiuers and receivers in contact with the casing wall through the use of pads, many of the problems common lO the standard mandrel-type tools are effectively eliminated. Experi­mental laboratory teSts indicate that angular resolution of the tool is 60 degrees as expected and that channels as small as 15 degrees can be detected.

From conception oflhis new generation CBL to final product, several rigLd parameters were demanded. Briefly these are;

1. Ease of interpretadon.

2. Eliminate ambiguity of convemional bond logs by quamita­tively depicting the bond condition around the casing (i.e. channelling).

References and illusrrations at end of paper.

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3. Complete data acquisition in one logging pass in all casing sizes4-IJ2" to 13-5/8" in both vertical and deviated well bores.

4. Be unaffected by gasified wellbore fluids, fast formation and slight tool decenrralizarion.

The purpose of this paper is to determine the success of Lhe SBT m fulfilling these goals. Presented here are four Canadian examples from widely varied areas having casing strings ce­mented wi rh various s lumes.

INTRODUCTION

As discussed in l.ester's Paper(CWLS 1989) and as summa­rized below, rhe evolution of cement bond logging has resulted in four distinct toollypes:

I. Standard Tool

- Utilizes a single rransminer and dual receivers usually moun Led at 3 and 5 foot imervals, with the amplirude measured at the 3 foot interval. Anenuarion is calculaled from this amplitude. The VDL is derived from rhe 5 foot spacing (Pardue el aI 1962). The data collected is effected by [001 cenrralizadon, well bore fluid condiDon, [l"ansducer variations, fasr formations, and calibration problems.

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2. Compensated Tool

Dual transmitters and tWO or Lhree receivers are utilized [Q

··compensate" for !.he inherent problems associared. with the standard bond Lool (Gollwitzer and Masson, 1982). Transducer van3uons are reduced by compensation and fast formation effects are curbed by closer transmitter/receiver spacmg. Cen· traliz.alion, however is critical and the log data is sIgnificantly deteriorated in gasified wellbore fluids.

3. Pulse Echo Tool

- Pulse echo lools employ an array of eight transducers in which reflection cha.ractensric~ are generated aL eight "points" around the casing wall (Froelich et al 1981). This was the first tool design which could detect channelling in [he casing [0

cement area. Advanced tools are able to provide a more complele cement analysLs, however two logging passes were required Tool response is subjeclLo wellbore nuids and center­ing problems simllano the SHllldard tool.

4. Pad Mounted Transmitter-Receiver Tool

. By mounung lhe transminers and receivers on pads which then ride along the casing wall in the logging position, many of the factors which effecLlhe earlier lools can be eliminaled. The Segmemed. Bond Tool (SBT) utilizes transducers mounted on six pad secuons as well as an improved 5 ft. VOL secLion. The pad seclion provides auenuation measuremems around the cas­ing in 60 degree segments averaged over 3 ft of vertical depth to accurately define channelling.

SBT CONFIGURATION

A complete SaT insrrument scing includes a gamma ray and/ or neuc-on, continuous collar locator, eiecu-ontC cartridge, pad and VDL sections. Cenrralization is ensured by Slip-on, in-line, or motorized roller cem.raJizers. Tool specific3nons are shown in Figure I.

The elecrronic cartridge previously mentioned coma ins a downhole computer which conITols [he SBT. An automattC gain conITol ensures thaI the measured amplitudes are neithercJipped nor In the noise. The digiLal telemetry system maim.ains consls· lent data by elirrunating any wi.reline effects.

A pair of acceleromeIers are used to determine Ihe low side of the welJbore. The orientation is correcl to +/- 5 degrees with a well deviation 10 excess of I degree.

TRANSDUCER CONFlQURATION

Each pad section mcludes a receiver and twin steered beam acoustic rransrruuers. Six separate allenuation measurements are made in a spiral fashion around the casing. Each measu~­mem uLilizes IWO cr.msmilter sets and twO receivers IO produce a fully compensaled signal over adynamic range of25 db/fl. The

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operarional sequence for the entire system is as follows

1. Transmitter T1 fires and ampJiIudes aL receivers R1 and R3 are recorded. as A 12 and A 13, respectively.

2. Transminer T4 fires and amplirudes at receivers R3 and R2 are recorded as A43 and A42, respectively.

3. Auenuation is lhen calculated as:

Anenuation = 10 log«A12*A43)/(AI3*A42))

ThlS is called "Subcycle #1"

4. The above process continues for a IOtal of six subcycles in the pad section.

5. Subsequently, the VOL measurement tS made as subcycle 7.

The twin Sleered beam rransmiuers refer to the twO a-ansmll­leTS seLS in each pad and VOL section. These twO transmLtters arc:: arranged. to control lhe directional characteristics thus enhancing the signal srrength in lhe desired direction. For example, thLs system Ylelds a VOL with enhanced formarion aITlvals whLle concurrenlly dampening lhe casing response. The net result is an easier 10 interpret VOL particularly in low velocity formations.

SOT PRESENTATION

To allow ease of interpretation, the SST log formal is sepa· rated into primary and secondary presentations. The primary log is similaTIO a standard BAL (c:ompens,ned) presemalion consi~l· ingofan amplitude, amplified amplirude, average and minimum allenuil.tion curves, and VOL in Tracks 2 and 3. The average attenuaLion is the average of the six subcydes while lne mim· mum (an adduion [0 the sIandard presentation) is the lowest attenuation value. Separation belween the average and mini­mum attenuation curves is shaded and indicates channelling. Track 1 includes CeL, gamma ray and/or neutron curves. The primary presentation is exaclly as seen On the (:ompuler CRT while logging. Figure 2 is the primary presentation header section.

The secondary presentation is derived in playback mode and consists of a cement map or variable anenuation log and the anenuation of the six subcycles plotted individually. The cemenL map is scaled in five incremenLs from white (0 fully blue LO graphically illustrate the bonding condition around the annular cavily in a continuoLls fashion. While represents a Bond Rating of 0 10 20% while fully blue is a 80 to 100% bond [1lting condition. The lhree ratings between are scaled in 20% incre· ments. The anenuarion values assigned are adjusted LO conronn with the compressive strength of the cement present. Separ:ue plOlS are made for each rype of cement pumped. FIgure 3 i~ a header section for lhe secondary presemation.

The Tool Azimuth Curve is ploned over the SLX !-Iubcycle!-l. In this manner, [he bond conditiOn (ie: channeling) LS referenced to lhe low side of the well bore and not a specific pOLnt on the tool.