Causes: Excessive spillage of drilling mud from the wellbore during large-diameter drilling. Insufficient drainage or poor cellar design, leading to accumulation of cuttings and mud. High pump rates and mud volume during spudding or top-hole drilling, especially in unconsolidated formations. Lack of proper flow control or redirection around the wellhead.
Consequences: Restricted access to wellhead equipment. Difficulties in running and cementing casing. Delays during well control operations or BOP installation. Safety hazards for rig crew due to slippery, unstable footing.
Mitigation Measures: Proper cellar design: Ensure cellar is deep and wide enough with drainage slopes. Install mud pits or sumps near the cellar for proper disposal. Use diverter systems or flow lines to guide mud and cuttings away from the cellar. Employ frequent cellar cleaning during top-hole drilling, either manually or with vacuum trucks. If drilling in rainy or water-prone areas, consider cellar waterproofing or dewatering pumps.
Operational Best Practices: Conduct pre-spud inspection to ensure cellar and drainage are ready. Assign crew for cellar monitoring and cleaning during drilling. Use gravel or steel grating on the cellar floor to improve footing and drainage. Reduce unnecessary mud discharge around the cellar.
