In situ is a latin phrase that simply means "in position", and in different contexts the term can refer to different processes. In an energy context the phrase usually means a form of mining where the rocks are kept in place, and the mineral resource is extracted. The term also comes up in police work and medical work. In the energy context, the term "in situ" often refers to:
Figure 1. A SAGD setup to extract bitumen from an oil sand deposit.
Figure 2. Open pit uranium mine in Namibia.