Extending Life for Offshore Wells by Fixing the Integrity High Annulus-B Pressure and Creating Zonal Isolation Using a Novel Remediation Technique

Ansari, Arsalan; Ringrose, David; Libdi, Ziad; Larsen, Arne G.

doi:10.2118/180555-ms

Cited by 4 publications

References 5 publications

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Improving the Understanding, Application and Reliability of the Perforate, Wash and Cement Technique through the Use of Cement Bond Logs, Tool Enhancements and Barrier Verification via Annular Pressure Monitoring

Lucas

Stokkeland

Jackson

et al. 2018

SPE Annual Technical Conference and Exhibition

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The Perforate, Wash and Cement technique has been widely applied to remediation of annular cement in recent years. Since 2012, extensive experience in the different technologies currently available on the market has been obtained across ten fields in the Danish and UK sectors of the North Sea and the data obtained has been used to attempt to better understand the effective operational window for the technique, and also further enhance reliability and tool robustness. The run data obtained from several wells has been calibrated against cement bond logging (CBL) responses so that the degree of annular bonding as inferred from the logs may be expressed in terms of the degree to which hydraulic communication or circulation is permitted via perforations and along the annulus. This in turn helps clearer decision criteria to be defined prior to execution that aids in the selection of the most appropriate method for remediating the cement, since Perforate, Wash and Cement may not be the most suitable technique in every case. Given the criticality of cement remediation to the long-term success of zonal isolation, it is important to demonstrate that effective hydraulic communication with the annulus has been established during the washing phase to ensure that the zonal isolation medium (cement) can be effectively placed and the hydraulic seal re-established, resulting in successful remediation. Post-execution verification of the effectiveness of remediation is typically performed via Cement Bond Logging. However, this may not always be a definitive verification step since Cement Bond Logging interpretation does have its limitations (both physical and interpretative), and hence annuli have occasionally been known to develop Sustained Casing Pressure even shortly after positive log interpretations following well-executed cementations. This paper therefore further demonstrates how Sustained Casing Pressure monitoring can be used as a further criterion to verify the integrity of the remediated annulus and hence conclusively demonstrate whether the washing and later cementing of the annulus has been effectively performed. This in turn is used as definitive confirmation that zonal isolation has been performed within the operating limits of the tool and hence qualify Perforate, Wash and Cement as a robust and viable remedial method.

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Improving the Understanding, Application and Reliability of the Perforate, Wash and Cement Technique through the Use of Cement Bond Logs, Tool Enhancements and Barrier Verification via Annular Pressure Monitoring

Lucas

Stokkeland

Jackson

et al. 2018

SPE Annual Technical Conference and Exhibition

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Simplifying Well Abandonments Using Shale as a Barrier

Oort

Juenger

Aldin³

et al. 2020

IADC/SPE International Drilling Conference and Exhibition

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Well abandonment is one of the biggest challenges in the oil and gas industry, both in terms of cost and effort as well as the technical hurdles associated with wellbore isolation for an indefinite term. A mechanism that may be exploited to simplify well abandonments is using natural shale formations for the creation of annular barriers. Currently, uncemented annuli often require casing milling and pulling before abandonment plugs can be set, which necessitates the use of a drilling rig. This is an expensive, time- and labor-intensive process, particularly offshore. However, shale creep may naturally form a barrier behind uncemented casing sections. With a qualified annular shale barrier in place, the well may only require the setting of abandonment plugs within the existing casing string(s), a task that can often be done rigless and with significantly less effort. The work described in this paper presents the results of a rock mechanical investigation into the creep behavior of North Sea shales and their ability to form effective annular barriers. Field core from the Lark-Horda shale was used to conduct dedicated, customized experiments that simulated the behavior of shale confined under downhole effective stress, pressure and temperature conditions to fill in an annular space behind a simulated casing string. Full scale tri-axial rock mechanics equipment was used for testing cylindrical shale samples obtained from well-preserved field core in a set-up that mimicked an uncemented casing section of a well. The deformation behavior of the shale was monitored for days to weeks, and the formation of the annular barrier was characterized using dedicated strain measurements and pressure pulse decay probing of the annular space. The large-scale lab results clearly show that the Lark-Horda shales will form competent low permeability annular barriers when left uncemented, as confirmed using pressure-pulse decay measurements. They also show that experimental conditions influence the rate of barrier formation: higher effective stress, higher temperature and beneficial manipulation of the annular fluid chemistry all have a significant effect. This then opens up the possibility of activating shale formations that do not naturally create barriers by themselves into forming them, e.g. by exposing them to low annular pressure, elevated temperature, different annular fluid chemistry, or a combination. The results are in very good agreement with field observations reported earlier by several North Sea operators.

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Simplifying Well Abandonments Using Shale as a Barrier

Oort

Juenger

Aldin³

et al. 2022

SPE Drilling &Amp; Completion

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Summary Well abandonment is one of the biggest challenges in the oil and gas industry, both in terms of cost and effort as well as the technical hurdles associated with wellbore sealing for an indefinite term. A mechanism that may be exploited to simplify well abandonments is using natural shale or salt formations for the creation of annular barriers. Currently, uncemented annuli often require casing cutting and pulling or milling before abandonment plugs can be set, which necessitates the use of a drilling rig. This is an expensive, time- and labor-intensive process, particularly offshore. However, shale or salt creep may naturally form a barrier behind uncemented casing sections. With a qualified annular shale barrier in place, the well may only require the setting of abandonment plugs within the existing casing string(s), a task that can often be done rigless and with significantly less effort. The work described in this paper presents the results of a rock mechanical investigation into the creep behavior of North Sea shales and their ability to form effective annular barriers. Field core from the Lark shale, a member of the Hordaland Group, was used to conduct dedicated, customized experiments that simulated the behavior of shale confined under downhole effective stress, pressure, and temperature conditions to fill in an annular space behind a simulated casing string. Full-scale triaxial rock mechanics equipment was used for testing cylindrical shale samples obtained from a well-preserved field core in a setup that mimicked an uncemented casing section of a well. The deformation behavior of the shale was monitored for days to weeks, and the formation of the annular barrier was characterized using dedicated strain measurements and pressure pulse decay probing of the annular space. The large-scale laboratory results clearly show that the Lark shale will form competent low permeability annular barriers when left uncemented, as confirmed using pressure-pulse decay measurements. They also show that experimental conditions influence the rate of barrier formation; higher effective stress, higher temperature, and beneficial manipulation of the annular fluid chemistry all have a significant effect. This then opens up the possibility of activating shale formations that do not naturally create barriers by themselves into forming them (e.g., by exposing them to low annular pressure, elevated temperature, different annular fluid chemistry, or a combination of these). The results are in very good agreement with field observations reported earlier by several North Sea operators.

show abstract

Extending Life for Offshore Wells by Fixing the Integrity High Annulus-B Pressure and Creating Zonal Isolation Using a Novel Remediation Technique

Cited by 4 publications

References 5 publications

Improving the Understanding, Application and Reliability of the Perforate, Wash and Cement Technique through the Use of Cement Bond Logs, Tool Enhancements and Barrier Verification via Annular Pressure Monitoring

Improving the Understanding, Application and Reliability of the Perforate, Wash and Cement Technique through the Use of Cement Bond Logs, Tool Enhancements and Barrier Verification via Annular Pressure Monitoring

Simplifying Well Abandonments Using Shale as a Barrier

Simplifying Well Abandonments Using Shale as a Barrier

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