ERSC 4P10 Lecture Notes - Lecture 5: Drill String, Drilling Fluid, Sedimentary Structures
22 Jan 2016
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Document Summary
Drilling core requires a hollow drill shaft. Drill cuts a cylindrical core that remains in the shaft. Diamond drilling requires that the entire drill string be removed to retrieve the core. Wireline coring uses a bit and shaft that allows the core to be pulled to the surface through the drill-string. Core: continuous cylindrical samples, 1 to 4 inches in diameter, used to determine grain size, lithology, primary sedimentary structures, porosity and permeability, very expensive to produce. The drill bit can vary from the vertical direction to drill angled or even horizontal holes. Unlike conventional drilling, the entire drill string doesn"t turn, only the bit turns; drilling mud provides hydraulic power to the bit. Allows more extensive contact between the hole and the pay zone. Allows production from beneath areas that are not accessible by vertical drilling. More extensive contact in fractured payzones (each fracture is a permeable pathway).
