Drill Cuttings Disposal Management

Drill cuttings disposal is a hot topic these years with global attention to environmental protection, especially in Oil & gas industry. Drill cuttings disposal into environment without any treatment is strictly forbidden. So before disposal, a series methods must be introduced to treat the cuttings and make it reach to disposal standard.

Drill cuttings are produced as the rock is broken by the drill bit advancing through the rock or soil; the cuttings are usually carried to the surface by drilling fluid circulating up from the drill bit by rotary, percussion, or auger methods. The drill cuttings are commonly examined to make a record (a well log) of the subsurface materials penetrated at various depths. In the oil industry, this is often called a mud log. One drilling method that does not produce drill cuttings is core drilling, which instead produces solid cylinders of rock or soil. In cable-tool drilling, the drill cuttings are periodically bailed out of the bottom of the hole. In auger drilling, cuttings are carried to the surface on the auger flights.

In the past, human has less attention to environment protection. The drill cuttings, after solid control system, usually directly disposal to a pit and then land-filled near drilling site. This method is commonly named Burial.

Burial is the most common onshore disposal technique used for disposing of drilling wastes (mud and cuttings). Generally, the solids are buried in the same pit (the reserve pit) used for collection and temporary storage of the waste mud and cuttings after the liquid is allowed to evaporate. Pit burial is a low-cost, low-tech method that does not require wastes to be transported away from the well site, and, therefore, is very attractive to many operators. In some oil field areas, large landfills are operated to dispose of oil field wastes from multiple wells.

However, land-filled usually results in anaerobic conditions, which limits any further degradation when compared with wastes that are land-farmed or land-spread, where aerobic conditions predominate. Burial may be the most misunderstood or misapplied disposal technique. Simply pushing the walls of the reserve pit over the drilled cuttings is generally not acceptable. Onsite pit burial may not be a good choice for wastes that contain high concentrations of oil, salt, biologically available metals, industrial chemicals, and other materials with harmful components that could migrate from the pit and contaminate usable water resources.

The objective of applying drilling wastes to the land is to allow the soil's naturally occurring microbial population to metabolize, transform, and assimilate waste constituents in place. Optimal land application techniques balance the additions of waste against a soil's capacity to assimilate the waste constituents without destroying soil integrity, creating subsurface soil contamination problems, or causing other adverse environmental impacts.

It may be necessary to follow steps to ensure the hydrocarbon and chloride content is lowered within the governing bodies standards before reusing or recycle the drill cuttings. Drill cutting can be recycled for use as a bulk particulate solid construction materials such as road base for site roads and pads. It can also be recycled for use as a major constituent of mixes for making substantially monolithic specialized civil engineering concrete structures of large size, such as roads and drilling pads.

While, before reusing or drilling cuttings disposal, the moisture content and the chemical composition on drill wastes should be determined. And it must be separated from liquid drilling fluid by oil-gas separator to remove harmful gas, shale shakers, decanter centrifuges, mud cleaners or cuttings dryer to separate the pieces of the cuttings from the drilling fluid.

This process allows the circulating fluid return to the drilling process for reuse, while cuttings are then studied by mud engineers and well loggers before proper disposal for further value realization. All the introduction, explanation, methods and equipment introduced here is wishing to realize both intention of drilling mud recycle to save cost and meet the environmental protection standard required by our government and our human civilization.

From: Gloria Yan, yuan.yan@adkosun.com, MP:(WhatsApp) +86 18602928622