Drilling a Well

The start of drilling operations is called "spudding in" or when the well is "spudded". The drill string consists of a drill bit, drill collars, drill pipe, and kelly. Drilling mud, is circulated through the kelly and the drill string by means of pipes and flexible hose connecting the mud pump. The mud pump draws fluid from mud pits located nearby. The drilling mud passes through the kelly, drill pipe, drill collars, and drill bit. It is returned to the surface by means of the well bore and the conductor pipe where it is directed to a device called a shale shaker. The shale shaker separates the drill cuttings and solids from the drilling mud, which is returned to the mud tanks to be circulated again.

In early wells, cable tool drilling was slow and laborious, but was revolutionized by the introduction of the rotary drill bit by Howard Hughes Sr. (father of the more famous Howard Hughes). The rotary drill bit consists of three revolving cones containing teeth or hardened inserts which cut into the rock as the bit is revolved. As the drill string is rotated in the well bore, the drill bit cuts into the rock. The drilling mud lubricates and cools the drill bit and drill string and carries the drill cuttings to the surface.

As the well is drilled, the drilling rate is monitored continuously at the surface by a geolograph. The rate varies according to the relative hardness of the rock and the wear on the drill bit but is generally of the order of five minutes a foot. The depth drilled is also recorded, sometimes from ground level, but usually from the kelly bushing (KB). The kelly bushing is located on the rig floor and connects the rotary table to the kelly which turns the drillstring.

When a well is spudded in, a large-diameter drill bit is used to drill the surface hole which is then lined with steel casing to protect aquifers which may contain fresh water. The surface hole may be several hundred or several thousand feet deep. After the surface casing has been cemented, drilling operations are resumed. The well-site geologist usually does not arrive until drilling approaches formations at depths that are prospective for oil. In Small County, the toolpusher contacts the geologist when the well has penetrated the Coronado Anhydrite (Permian) to come to the rig and commence geological description and formation evaluation.