Completion

After drilling and casing the well, it must be “completed”. Completion is the process in which the well in enabled to produce oil or gas.

In a cased-hole completion, holes (called perforations) are made in the casing that covers the reservoir section to provide a path for the oil to flow from the surrounding rock into the well bore. In open hole completion, often “sand-screens” or a “gravel pack” is installed in the last drilled, uncased reservoir section. These tools are to maintain structural integity of the wellbore in the absense of casing, while still allowing flow from the reservior into the wellbore.

After a flow path is made, acids or other fluids are often pumped into the well to fracture, clean, or otherwise prepare and stimulate the reservoir rock to opimally produce hydrocarbons into the wellbore. Finally, the area above the reservoir section of the well is paked off inside the casing, and connected to the surface via a smaller diameter pipe called tubing. This arrangement provides a redundant barrier to leaks of hydrocarbons as well as allowing damaged sections to be replaced. Also, the smaller diameter of the tubing produces hydrocarbons at an increased speed.

In most wells, the natural pressure of the subsurface reservoir is high enough to push the oil or gas all the way to surface. However, this is not always the case, especially in depleted fields where the pressures have been lowered by other producing wells. Installing a smaller diameter tubing may be enough to help the production, but other types of aritficial lift can also be used. Common solutions are downhole pumps, gas lift, or surface pumpjacks - the "nodding donkey" pumps dotting the countryside in old oil fields in Texas and Oklahoma.

Дата добавления: 2015-07-21