Imagine you are playing with a straw and a cup. You put the straw into the cup, but the straw is bigger than the hole in the cup. So you need a small cap to put on top of the cup so that the straw fits snugly through it. This cap is similar to a casing head in an oil well.
An oil well has a big hole in the ground that goes deep into the earth. Through this hole, we drill a smaller hole called a wellbore to reach the oil reservoir deep below. Since the wellbore is smaller than the hole drilled in the ground, we need something to cover the gap between the two. This is where the casing head comes in.
The casing head is like a cap that covers the gap between the wellbore and the hole drilled in the ground. It is made of strong materials like steel and has a hole in the middle where the wellbore passes through. The casing head also has different fittings to help with drilling, producing, and controlling the oil and gas that come out of the well.
In summary, a casing head is like a cap that covers the gap between the wellbore and the hole drilled in the ground. It helps to control the production of oil and gas from an oil well.