There are usually 3-4 large tanks to collect the water used to frack the formation, and usually two tanks for oil (one main one, one back-up) for new wells even if they’re primarily gas. The water comes in fast up front so you need lots of tanks to hold the large volumes. Then they’ll usually remove some as they’re no longer needed.
In this part of the world usually seismic is used to see how the reservoir is moving and changing below the surface so the well is able to follow the reservoir as they steer while drilling. Older vertical wells are usually used to look see what the qualities of the reservoir are by logging properties of the rock up the well-bore (“well logs”), like if it’s gas or oil, how much water is in there with it, and how good the reservoir rock is (how porous, etc.).
Looks like where this well is the reservoir is quickly transitioning from oil to gas within a 5 mile span (in the same reservoir; for this reservoir, west = gas, east = oil). I’m sure they had an idea what it could be, but didn’t know exactly where the boundaries were.