History of Oil

         Crude Oil: Key Historical Events

          Fundamentals of Oil
               Finding Oil & Gas
               Securing Leases
               Drilling For Oil & Gas
               Evaluating/Well Logging/Coring
               Completing the Well
               Artificial Lifts/Injection Wells
               Oil Production/Secondary Recovery
               Waterflooding in the Illinois Basin
               Operation/Sale of Oil

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Completing the Well

After the operating company carefully considers all the data obtained from the various tests it has ordered to be run on the formation or formations of interest, a decision is made on whether to set production casing and complete the well or plug and abandon it. If the decision is to abandon it, the hole is considered to be dry, that is, not capable of producing oil or gas in commercial quantities. In other words, some oil or gas may be present but not in amounts great enough to justify the expense of completing the well. Therefore, several cement plugs will be set in the well to seal it off more or less permanently. However, sometimes wells that were plugged and abandoned as dry at one time in the past may be reopened and produced if the price of oil or gas has become more favorable. The cost of plugging and abandoning a well may only be a few thousand dollars. Contrast that cost with the price of setting a production string of casing - $50,000 or more. Therefore, the operator’s decision is not always easy.

Setting Production Casing
If the operating company decides to set casing, casing will be brought to the well and for one final time, the casing and cementing crew run and cement a string of casing. Usually, the production casing is set and cemented through the pay zone; that is, the hole is drilled to a depth beyond the producing formation, and the casing is set to a point near the bottom of the hole. As a result, the casing and cement actually seal off the producing zone-but only temporarily. After the production string is cemented, the drilling contractor has almost finished his job except for a few final touches

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