2. Characteristics of drilling solid waste
2.1. Production characteristics of drilling solid waste
Drilling solid waste was produced in construction period of gas well, and included waste mud, rock cuttings, weighting materials, and so on. Waste mud of the drilling field was nearly between 800~1200 m3 per well, rock cuttings were about 1000 m3 per well. In period of drilling, weighting materials may be used when necessary. If emergency probability was 1% and waste yield was 500 m3 per well, weighting materials was 5 m3 per well. Apparently, waste mud and rock cuttings were the main drilling solid waste.
2.2. Physicochemical characteristics of drilling solid waste
Since compound of waste mud and rock cuttings was the main drilling solid waste, the massive landfill received drilling solid waste of the central field was investigated. And the solidified waste was sampled by the common planar method. The solidified waste was loose and of dark grey color. Experimental study showed that density of the solidified waste was1.75 g/cm3, moisture was 24.0%; and its component, heavy metal content, radioactive element content were respectively presented in Table 1~ Table 3.
Table 1. Component of the solidified drilling solid waste from a gas field Items Cl- SO42- Na Fe Ca Mg Si Al CO32- petroleum other
Content (%) 0.1 5.6 1.0 9.0 12.4 6.8 15.8 22.8 10.2 0.4 15.9
As showed in Table 1, main components of the solidified waste mud and rock cuttings were inorganic and organic matters with element of Al, Si, Ca, Fe, individually reached 22.8%, 15.8%, 12.4%, and 9.0% of the sample weight, totally to 60%.
Table 2. Heavy metal content of the solidified drilling solid waste from a gas field
Items Cd Hg Pb Cr As Zn Ni Cu B
Values(mg/kg) 0.3 0.27 43 36 3.2 234 70 40 1.2 Limit (pH≥6.5) 20 15 1000 1000 75 1000 200 500 150
Limit (pH