Basic Oil Well Drilling Knowledge

Oil Drilling 

An oil well is any bore drilled through the Earth's subsurface layers and it is designed to find and gain hydrocarbons. The well is being drilled by complex dangerous methods called (drilling process) ,these methods will be discussed later. The well that is designed to produce mainly or only gas may be termed a gas well .each well has a criterion called well life which is divided into segments are:

1. Well Planning: Well planning is perhaps the most demanding aspect of drilling engineering. It requires the integration of engineering principles, corporate or personal philosophies, and experience factors. Although well planning methods and practices may vary within the drilling industry, the end result should be a safely drilled, minimum-cost hole that satisfies the reservoir engineer’s requirements for oil and (or) gas production. 
2. Drilling: complicated methods used to create cemented(cased) oil or gas well use heavy duty tools and at the same time very developed In terms of technological advance , these methods developed during time. The drilling process is very expensive and dangerous (discussed later). 
3. Completion: Completion is the process in which the well is enabled to produce oil or gas, Contains: - cased-hole completion, small holes called perforations are made in the portion of the casing which passed through the production zone, to provide a path for the oil to flow from the surrounding rock into the production tubing. -open hole completion, often 'sand screens' or a 'gravel pack' is installed in the last drilled, uncased reservoir section. These maintain structural integrity of the wellbore in the absence of casing, while still allowing flow from the reservoir into the wellbore. 
4. Production: The production stage is the most important stage of a well's life, when the oil and gas are produced. By this time, the oil rigs and workover rigs used to drill and complete the well have moved off the wellbore, and the top is usually outfitted with a collection of valves called a Christmas tree or production tree. These valves regulate pressures, control flows, and allow access to the wellbore in case further completion work is needed. From the outlet valve of the Oil Well Drilling Mahmood Jassim Page 6 production tree, the flow can be connected to a distribution network of pipelines and tanks to supply the product to refineries, natural gas compressor stations, or oil export terminals. 
5. Abandonment: A well is said to reach an "economic limit" when its most efficient production rate does not cover the operating expenses, including taxes The economic limit for oil and gas wells can be expressed using special formulas. At the economic limit there often is still a significant amount of unrecoverable oil left in the reservoir. It might be tempting to defer physical abandonment for an extended period of time, hoping that the oil price will go up or that new supplemental recovery techniques will be perfected. In these cases, temporary plugs will be placed downhole and locks attached to the wellhead to prevent tampering. There are thousands of "abandoned" wells throughout North America, waiting to see what the market will do before "permanent" abandonment. Often, lease provisions and governmental regulations usually require quick abandonment; liability and tax concerns also may favor abandonment. In theory an abandoned well can be reentered and restored to production (or converted to injection service for supplemental recovery or for downhole hydrocarbons storage), but reentry often proves to be difficult mechanically and not cost effective.