Facing shallow gas always has been challenging in exploration and development drilling operation around the world. Shallow gases refer to near surface gas containments which are not expected to be right under bit. Near surface formations always are unconsolidated and do not need any special well control considerations but presence of a pressurized gas layer will change everything and will put anything on danger especially when gas reaches to the surface and just needs a little spark to turn everything to the ash after a huge explosion.
On the other hand, using heavy weighted drilling fluids for controlling formation pressure may not work in the entire open hole and result in medium to severe mud losses. Most often, severe losses are following by flow of formation fluid to the annulus, which is called kick, or in advanced, blowout. Blowouts may just take a few seconds to strew the mud column away. They results from salt water or shallow gases. Sometimes, because of losing wellbore wall support exerted by mud column due to complete loss, it tends to tighten and will stick the drillstring.
Occurrence of each phenomenon will result in losing dollars because of either time spent for curing them or leaving instruments in the hole. These irrecoverable events could be prevented with conducting an integrated geomechanical study before drilling and being aware about shallow gas signs while drilling in conjunction with an appropriate well control procedure will help to mitigate shallow gas consequences. In this paper, after investigation of probable cause of kick and blowout, a case study from Middle East reviewed.