Conductor and Surface Pipes at Start of Spud26 Sep 2023 13:12
Found this on DrillingFormulas.com
Good description of the initial processes.
On land, a majority of wells begin with digging a cellar, which can be from 3 to 15 feet in depth. The primary purpose of a cellar is to align the Christmas tree at relative ground-level. Having the Christmas tree at relative ground level allows for easier access to the valves, chokes and other equipment. The first string of pipe to be used in a well is called the conductor pipe or drive pipe. To being, a large diameter hole is drilled to a specified depth, generally relatively shallow, such as 1 or 200 feet. The pipe is driven into the ground to a specified depth or to the point of refusal. In most cases, an adaptor flange or a drilling flange is welded to the conductor pipe as a means to connect a diverter system or blowout preventer system.
Upon completion of the surface hole, the surface pipe is run to a specified depth to isolate any freshwater, saltwater, oil or gas zones within that depth range. The surface pipe is run and cemented in place back to the surface. A cement plug is left in the surface pipe, so that a diverter system or a BOP system may be disconnected or nippled down safely.
After the diverter or BOP system has been nippled down, the surface pipe is drained. Then the adapter flange or drilling flange is cut off. The final cut-off height is determined by adding the height of each piece of wellhead equipment, plus the stand-off distance between each piece of equipment and the rig gasket height. Then the depth of the slip on socket in the bottom of the casing head housing. If a base plate is used, its height must also be considered. The sum of these heights is then deducted from the cellar depth to determine the final cut-off height, for both the conductor pipe and surface casing.
When the final cut on the conductor and surface pipe is completed, the casing head housing is prepared for installation. The casing head housing is welded in place on the surface casing. The pieces welded on the inside diameter and the outside diameter, then tested to assure there are no leak paths in the wells. This test checks the wells, but does not test the integrity of the casing head housing. The base plate which is slightly larger than the conductor pipe, may be tack welded to the conductor pipe, if desired. The base plate serves as a means to transfer weight from the casing head housing back onto the conductor pipe. When the casing head housing has been successfully welded and tested, the BOP system is installed or nippled up and preparations are made to drill out for the intermediate string of casing. To test the BOP system, the test plug is made up from the drilling string and lowered through the BOP system, until properly located in the casing head bowl. Pressure is applied from above the plug and the BOP system is tested.
The Intermediate and Production Drilling and Casings follow on after the completion of the Conductor and Surface processes
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