Formation damage was minimized by drilling the lateral leg as quickly as possible. A large part of the problems encountered while drilling horizontal wells were related to an inadequate amount of circulation to keep the hole clean. Because of this, tool sticking was common. After production began, periodic workovers were required to clean out fines from the bottom of the hole. This was usually done with nitrogen.
Fractures are sensitive to drawdown.
Horizontal wells cannot be stimulated by sand proppant. Fractures in the shales are held open entirely by the fluid. Microfractures essentially act as the storage system and supply the larger regional fractures with oil. Significant drawdown on the well can cause the microfractures to close adjacent to the wellbore, sealing off the source of oil. This type of damage may be caused by drill stem testing.