Systems and methods are provided for determining a cure state of cement in a wellbore. A drill device can be used to drill cement in a wellbore. Contact between the drill device and the cement can cause friction or heat, which can produce a gas. A gas detector can be positioned near a wellbore for detecting an amount of gas and a type of gas produced by contact between the drill device and the cement in the wellbore. The cure state of cement in the wellbore can be determined based on the amount of gas and the type of gas detected.