Oilfield Innovations have a number of thru-tubing logging methods for Plug and Abandonment (P&A). Both methods eliminate the need to pull the tubing to bond log the in-situ casing cementation. One thru-tubing logging method compacts the tubing as shown to the right and another spikes the tubing to the casing as shown below. As shown below, another method spikes the tubing to the casing to centralise the tubing and transmit/receive logging signals.
Conventional through-tubing logging is not possible because sonic or acoustic signals cannot be predicted or interpreted accurately when the tubing is loose within the casing. Oilfield Innovations have patented the method of spiking the tubing to the casing to centralise it and connect it to the casing so that sonic and acoustic logging signals can be transmitted and received through the spikes to confirm cementation behind the casing and, optionally, confirm cement bonding after placing the cement abandonment plug.
Conventional acoustic sonde compression and shear wave types used in cement bond logging require direct access to cemented casing and cannot log thru-tubing. Oilfield Innovations' patented method spikes the tubing to the casing so that acoustic waves can be transmitted to and received from the casing to determine cement bonding and does not required removal of the tubing, which makes it a perfect rig-less solution.
Cement bond logging can comprise connecting an array of receivers that measure an acoustic pulse as it passes along the well bore. Transmitting a wave-train of acoustic pulses through casing, as shown above, can measure cement bond quality. For example, using an array of geophones used in VSP logging can assess in-situ cementation.
An array of spikes connecting the tubing to the casing can be with an array of transmitters and receivers that can send and receive wave trains to simulation the movement and averaging of conventional cement bond logging signals.
The array of transmitters and receivers can measure the bond of in-situ cement, but also can be left in place to measure the bond of the placed cement abandonment plug.
Accordingly, should the well ever leak due to circumstances beyond control, it is possible to provide evidence that a proper cement plug was placed during well abandonment.
Pulling the tubing during P&A is expensive and may not be necessary.
As described above and shown to the right, the tubing can be spiked to the casing to secure the tubing and provide predictable vibration so that logging signals may be passed through the spikes to the casing to determine in-situ cement bonding.
Initial P&A plugs isolating the reservoir are normally placed by rigless means. Once the reservoir is isolated the tubing can be punched to provide circulation and cleaning of the annulus.
An array of spiking tools, transmitters and receivers can then be used to secure the tubing to the casing and centralise it for later cementation.
Crossing wave-trains of logging signals can be transmitted and received in both an upward and downward direction to assess the bonding of in-situ casing cement.
After confirming cement bonding, the abandonment cement plug can be circulated into the well and allowed to set. Cement wiper plugs and pressure can be used to place the top of cement in the desired location, whereby a connection to the logging array is possible with, for example, a wet connection.
After setting, the P&A plug cement bond can be assessed by further cross-directional wave train logging signals.
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