I am the Welcome to Fall with Julian Engineering. Oil and gas is not found in large carvings, deep down in the underground as some people think. They sit in the microscopic paws of the rock. This paws look similar to the holes here in this model. If we now drill a borehole into such a porous formation, the borehole is of course already filled with drilling mud, and this mud gets in direct contact with the flutes in the paws of the rock. If the pressure in the borehole is greater than the pressure of the flutes in the paws, some of the drilling mud will flow into the formation. Special particles in the drilling mud however quickly form a tight filter kick on the walls so that the losses are stopped. The big advantage of this overbalance drilling is that with over pressure in the borehole, the oil or gas can flow from the formation into the borehole and to the surface where it can cause an explosion. However, the downside of overbalance drilling is that the pressure of the drilling mud hinders the coatings on the bottom of the borehole to be removed, resulting in a slower penetration rate. Besides this, the filter kick can also cause a problem as the particles clog the microscopic pores in the rock, thereby hindering the later production of oil and gas from the well. Therefore, the question arises, is it possible to drill with under pressure in the borehole? This is what we call underbalance drilling. When drilling under balanced, water, oil and gas are constantly flowing from the formation into the borehole. So in this case, no filter kick can be formed. The borehole was staked open and the pores are not clogged. We can also drill faster because the flutes information leave the coatings on the bottom of the borehole so they can be effectively removed and flushed away easily as you can see in the picture behind me. These are all advantages of underbalance drilling and it appears to be very attractive, but under balance drilling is in a way dangerous. Due to the influx from the formation, the borehole constantly overflows at the surface, like this glass of beer behind me. We see that the borehole is alive. We can of course close the blow-up preventer to stop the overflow, but then the borehole buttes of pressure, and that is also a problem because it is quite difficult to assess and work in a light borehole, for example, tripping in and out the drill strength. Of course, drillers have developed a special drilling method that can be applied in such tricky situations. If you want to know more about them, come to our lecture, Drift Drilling Engineering 2 here in Fryback. We look forward to see you. Look up!