Application of gray theory in oil and drilling cost estimation;

In order to reduce drilling cost and economical and efficiently exploit peripheral virgin reserves in the Daqing Oilfield, test researches on surface-casing drilling technology are started, including the general proposal and techniques of casing drilling, casing string structures and accessories, downhole tools and special cementing tools.

Because of the deep buried depth and small reservoirs of Anpeng oilfield, and in addition to the downhole troubles such as stuck pipe in the slim hole and lost circulations caused by improper use of polymer drilling fluid, the drilling cost was very high and thus iimited the development of the oilfield.