PeteMN - 3/27/2009 10:17 Don't know how true or not, but those opposed to drilling were concerned about the contamination due to the slurry that was pumped down to the drill point for lubrication. I think that is a concern of those opposed to the fracturing method, too. Don't know how valid a claim it is, just compare it to machine shop cutting fluids, the only solution some want there is to use no lube at all. The additional primary purposes of drilling mud is to: 1. Carry the formation cuttings out of the hole. 2. Keep the hole from caving in from the absence of the removed formation cuttings. 3. Keep the well from blowing out from release of oil and gas down in the hole. As for the fresh water zone contamination, when drilling is first started, they are drilling with a much larger drill bit than what they finish the well. They are drilling a larger hole for the surface pipe. Surface pipe is supposed to seal off the fresh water zone from any contamination by the drilling fluid used for the deeper drilling. It is cemented in by oilfieldd service companies like Halliburton. The surface pipe is also used for the installion of the blow out preventer. The suction pits and circulating pits are generally what will cause the contamination problem if any contamination does occur. In my area, generally the surface was drilled with 11 inch drill bit, 8 5/8 inch pipe is the surface pipe and a 7 7/8 inch drill bit is used to finish the well. | 
Oilfield Drilling Questions
