Downhole monitoring

CaTS™ is available as a completion conveyed solution for use in those applications where it is not possible to deploy a conventional cabled permanent monitoring system (PDG) at the required location in the wellbore. An example application area is that of big bore high rate gas wells where the completion design may employ a large bore production liner that extends for several thousand feet above the producing sandface. Use of a large bore production liner prevents the placement of a traditional PDG close to the producing sand face.

This means that a cabled monitoring system must be located several thousand feet away from the flowing sandface, which due to the gravity head difference and frictional pressure drop, introduces significant uncertainty into the accuracy of the measurement and how it relates to the actual sand face flowing pressure.

A large bore CaTS mandrel, suitable for deployment in 9 5/8" casing/liner, has been developed. When conveyed as part of a lower completion assembly, this can be positioned in close proximity to the producing sand face and then transmits the data through the casing or production liner to a pickup point located higher up in the well and somewhere above the production packer. The signal is then relayed to the seabed via a CaTS downhole signal pick-up and conventional 1/4" encapsulated cable located in the annulus.

At the seabed the signal is collected and processed in an IWIS compatible CaTS subsea receiver, which is interfaced with the subsea electronics module of the tree provider to provide real-time data direct to the client's network.

Where high rate gas wells are being produced on drawdown constraint, having an accurate measurement of the sand face flowing pressure enables the operator to optimise the well production. Pressure transient analysis using data collected from close to the reservoir is more representative than data collected several thousand feet higher in the wellbore resulting in the operator gaining a better understanding of the reservoir.