Advances in Cement-Plug Procedures

Heathman, James

doi:10.2118/36351-jpt

Cited by 20 publications

(4 citation statements)

References 2 publications

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“…Fig. 7.10 Schematic of stratified axial exchange flow; a cement plug placed on a drilling fluid with lower density than cement, b buoyancy force is compromising the plug stability and creates three distinct zones [16] There are some recommendations to minimize the contamination introduced by buoyancy and to achieve a stable plug, including reducing the density differences between cement and drilling fluid (viscous pill), increasing the yield stress or gel strength of the drilling fluid below the intended cement plug, placing a reactive gelled pill between cement and drilling fluid, and avoiding thixotropic cement slurries for balanced plugs [38,44,45]. If the induced agitation passes the YP of slurry, the buoyancy and gravity forces will be activated and the contamination effect will be intensified at the interface between the slurry and the drilling fluid and subsequently, the plug stability.…”

Section: Mud Displacement During Cementingmentioning

confidence: 99%

“…It is believed that during balanced-plug placement when a thixotropic slurry is used, the slurry tends to stay in the end of the tailpipe when the intended cement plug is placed. Pulling the tailpipe out of the static thixotropic slurry creates a drag force on the drilling fluid below the cement, and leads to intrusion of the drilling fluid into the slurry, therefore the slurry is contaminated [45]. However, use of a thixotropic cement slurry, which develops gel strength rapidly, improves the plug stability while cement sets [44].…”

Section: Mud Displacement During Cementingmentioning

confidence: 99%

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Fundamentals of Plug Placement

Khalifeh¹,

Saasen²

2020

Ocean Engineering &Amp; Oceanography

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The best practice of permanent plug and abandonment requires a cross sectional barrier, which is known as rock-to-rock barrier. The barrier is placed at the right depth where formation is capable to hold the maximum anticipated pressure. To fulfill the requirement, two general situations could be encountered: openhole plug placement or cased hole plug placement. Openhole Plug PlacementTo place a permanent cement plug in an openhole, the fluid in the well needs to be replaced with cement. As the compositions and properties of drilling (or milling) fluids and cement slurries vary widely, severe contamination can occur at the interface of drilling fluid and cement slurries due to incompatibility. Therefore, fluid removal during cement plug placement is a crucial task. Fluid RemovalFluid removal has been an interest for cement engineers for many years. To achieve the objectives, drilling fluid and pre-flushes must be fully removed from the openhole interval and be exchanged fully with cement or any plugging material. The fluid removal process is a function of borehole quality, circulation and displacement efficiency, fluid conditioning and properties of drilling fluids, spacers and washes [1][2][3][4][5][6]. Fluid removal process can be carried out in two main different ways: hydraulically or mechanically. In the hydraulic process, spacer fluids with specific viscous behavior are pumped ahead of cement slurry to displace drilling or milling fluid. The contamination effect of these spacer fluids on cement is less compared to drilling or milling fluids.

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Section: Mud Displacement During Cementingmentioning

confidence: 99%

Section: Mud Displacement During Cementingmentioning

confidence: 99%

Fundamentals of Plug Placement

Khalifeh¹,

Saasen²

2020

Ocean Engineering &Amp; Oceanography

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“…The mentioned equation suffers from some errors because during the level-off process not only the cement slurry level drops, but also a mud level drop would occur due to the positioning of part of the mud from inside the drill pipe to the casing below the packer (with a larger bore than the drill pipe). Other investigators have described cement plugging techniques (but not the level-off method) in detail in numerous papers, e.g., Smith (1990) and Griffin (1990). The details of the level-off method are not only explained in this work, but also its more accurate version is developed and presented.…”

Section: Introductionmentioning

confidence: 99%

‘Level-off’ cement plugging method to cure lost circulation verified with case studies

Ashena

Ghalambor

Elmgerbi

et al. 2021

J Petrol Explor Prod Technol

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Controlling lost circulation during drilling operations in a reservoir prone to fluid losses is typically remedied by cement squeezing or plug setting as the last resort. The aim being to minimize or stop drilling fluid losses and to regain full returns at surface, and to maintain wellbore integrity. Different placement methods of cement plugs have been discussed in detail in the literature, except for the ‘level-off’ method, which can be effective for curing complete loss circulation cases. Following modeling and calculations of this cement plug placement method, its design and execution procedures are discussed, together with two successful field cases in highly fractured carbonate reservoirs in the Middle East. Using drill pipe and a Retrievable-Test-Treat-Squeeze (RTTS) packer, set with some spacing from the loss zone, the method entails that the cement slurry is allowed to drop by gravity in order to cure lost circulation. As the column of fluid, mud and slurry in the well exceeds formation pore pressure, i.e., overbalanced conditions, a volume of acid-soluble cement slurry is allowed to slowly drop and freely penetrate the formation, i.e., through its fractures or caverns. During the penetration of this viscous slurry into the loss zone, the cement slurry can set and the fracture or fissure openings are plugged. Presented are detailed design calculations for the level-off placement technique, determination of required cement slurry and displacement volumes, and recommended displacement and RTTS packer setting depths. The expected depth of the top of cement plug is estimated. The design parameters are compared with field cases and explanations are given for possible discrepancies. Success of the operation is discussed in terms of final mud loss after cement plugging and Non-Productive Time mitigation. Detailed field procedures and execution are also presented. The level-off job is already practiced by the industry, but it is not published in the literature, in some cases they have different methods with causing some errors. To the best of authors’ knowledge, this is the first detailed description and stepwise calculation of the level-off cement placement technique in the literature.

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“…The reasons for the low success ratio have been investigated by several authors 3,4,8 and best practice guidelines have been suggested to deal with many of the operational problems. Some of the problems encountered can be related to the circumstances in which the plugs are set, which are often adverse in that the plug must be set quickly in response to an unplanned event, and other problems are a consequence of the fluid properties.…”

Section: Introductionmentioning

confidence: 99%

Cement Plugs: Stability and Failure by Buoyancy-Driven Mechanism

Crawshaw

Frigaard

1999

SPE Offshore Europe Oil and Gas Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSetting cement plugs off bottom is a well recognised problem in the industry. Different causes of failure have been identified over the years and many have been addressed by improving practices used in the field. A remaining problem is the instability of the lower interface between the cement and the fluid below, driven by the greater density of the cement. That is, once a cement plug has been injected into the wellbore it must resist the tendency to fall through the less dense drilling fluid below until the cement has set. The fluid properties which ensure stability have never been satisfactorily established and it is this gap which is addressed by the current work.Theoretical and experiment results are presented in this paper which allow the estimation of the yield stresses required of the fluids to stabilise a cement plug under any conditions of hole size, inclination and density difference between the cement and the fluid underneath. The experimental work shows that the model is somewhat conservative and this is discussed in terms of the assumptions made in each case.

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Advances in Cement-Plug Procedures

Cited by 20 publications

References 2 publications

Fundamentals of Plug Placement

Fundamentals of Plug Placement

‘Level-off’ cement plugging method to cure lost circulation verified with case studies

Cement Plugs: Stability and Failure by Buoyancy-Driven Mechanism

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