Oil wells are drilled through layers of rock to access the reservoir below. These artificially introduced holes must be stabilised with a wall structure composed of so-called casings. This prevents the borehole from collapsing and isolates it from any unwanted fluid or gas exchange with the environment. Peruse this great educational article on casings for more detailed information or watch the video below.
Why are we interested in casings?
Optical fibres can be integrated into the casing structure as a life-of-well monitoring system. Installed fibres are located right behind the production casing that seals off the inside of the borehole.
Why are optical fibres needed in an oil well?
Optical fibres enable distributed sensing along the length of the well to monitor its integrity. Their capability and wealth of generated data is far superior to conventional logging tools that can only monitor the first casing-to-cement bond. Distributed sensing can indicate environmental events, such as pressure drop or temperature fluctuation, in the vicinity of a well and the surrounding cement and formation interface, even across several casing strings.
By integrating fibres into the casing, distributed sensing gathers data not only to monitor oil and gas production in the active well, but already much earlier in the well’s life cycle to surveil cementing and other preparatory processes. When the life of a well comes to an end, fibre-optic sensing can yield crucial information that permits operators to abandon the well safely, securely and economically.