Oil and gas wells are required to be plugged when the production of these wells is no longer economical. Cement is the current standard method for plugging wells. However, this process has limitations because cement is expensive and prone to cracking and unsealing. This paper aims to review and investigate the use of a naturally occurring clay called bentonite to plug CSG wells in Queensland as well as oil and gas wells in general. Bentonite is cheaper and easier to handle and when hydrated it creates a more reliable plug because it is malleable and self-healing when disturbed.

We also experimentally and theoretically investigate the mechanisms for failure of bentonite plugs. The plug failure mechanisms can be determined by comparing the measured dislodgement pressure and the predictions of the theory developed in our group. Based on our preliminary results we found that the hydrated plugs can be made significantly stronger by restricting the expansion space. This allowed us to measure the internal swelling pressure at 8 MPa which corresponded to measurements reported in the literature at a reduced density of 1.6755 g/cm3.

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