Abstract
Upstream environmental policies require the use of best available and economically sound technology to continually reduce discharge of mud and cuttings waste resulting from drilling operations. Downhole disposal of mud and cuttings waste through hydraulic fracturing, Drill Cuttings Re-injection(DCRI), is often the preferred waste management option because it can achieve true zero discharge without being limited by the drilling location and it is also economically favorable.
Iran's petroleum industry produces large amount of drilling wastes annually. The giant oilfields, the wide drilling operations without any plan to treat or to dispose of wastes, cause so dangerous environmental problems that damage the agriculture and animal husbandry in these fields.
This paper tries to investigate the possibility of drill cuttings re-injection (DCRI) in Ahwaz oilfield. The volume of drilling waste is calculated for a typical well. Disposal formation selection is the next important and sensitive step. By using a hydraulic fracturing simulator, the lateral and vertical extent of the fractures can be estimated and modeled to ensure they do not cut across overlying sealing beds, intersect with other well bores, natural fractures, faults, drinking water aquifers.
A data gathering for subsurface geology and logging analysis and also the position of potable water sources and recoverable hydrocarbons throughout the field are shown that the Mishan formation is more appropriate for DCRI. The depth of almost 5000 ft of Mishan assures that created fractures are developed below enough underneath surface and far from hydrocarbon reservoir in 10000 ft depth. Numerous scenarios were considered in the feasibility studies to ensure that fractures do not breakthrough to surface during cuttings re-injection in the absence of stress or permeability barriers of upper formations. Even under the most severe conditions, it was found that the generated cuttings slurry could be safely injected.
