During the exploration and production of oil, huge amounts of drilling wastes are produced in the form of mud and cuttings. As per conservative estimates, around 0.37 kg of drilling wastes is generated for every barrel of oil produced. The American Petroleum Institute (API) has estimated that approximately 1.21 barrels of total drilling wastes are generated for every foot drilled.
The Middle East oil and gas industry has made a lot of effort in order to reduce the environmental impact of their activities; modern drilling methods such as horizontal drilling, navigating the drill bits three dimensionally through the earth, contacting and economically producing resources while minimizing surface disruption. Drilling wastes must be properly managed to prevent negative impact on human health as well as on the environment.
Drilling Waste Management
Drilling waste management technologies and practices can be grouped into three major categories: minimization, recycle/reuse, and disposal. The first step in managing drilling wastes is to separate the solid cuttings from the liquid drilling mud. Once solid and liquid drilling wastes have been separated, companies can use a variety of technologies and practices to manage the wastes. For some applications, drilling wastes are solidified or stabilized prior to their ultimate management practice.
Drilling wastes, such as cuttings, are indifferent and not of specified quality. The cuttings separated from the mud at the shale shakers may be coated with so much mud that they are unsuitable for the next reuse or disposal step or are difficult to handle or transport. Constituents of the cuttings or the mud coating them (e.g., oil, metals) may leach from the waste, making them unsuitable for land application or burial approaches.
Various materials can be added to cuttings to solidify and stabilize them. Still this can be an opportunity for cement plants to use uncontaminated cuttings as substitute raw material, even in a lower substitution. The use of such raw materials will be more environmental friendly then the common practice of oil companies to spread such cuttings on the land.
Several different approaches are used for injecting drilling wastes into underground formations for permanent disposal. Slurry injection technology, which involves grinding or processing solids into small particles, mixing them with water or some other liquid to make slurry, and injecting the slurry into an underground formation at pressures high enough to fracture the rock. As these muds could be used as fuel resource and substitute other fossil fuels, it is preferred to process the muds and use them.
Use of Drilling Wastes in Cement Industry
Thermal technologies use high temperatures to reclaim or destroy hydrocarbon-contaminated material. Thermal treatment is the most efficient treatment for destroying organics, and it also reduces the volume and mobility of inorganic such as metals and salts. Additional treatment may be necessary for metals and salts, depending on the final fate of the wastes. Waste streams high in hydrocarbons (typically 10 to 40%), like oil-based mud, are good candidates for thermal treatment technology.
The use of drilling wastes and muds is most preferable in cement kilns, as a cement kiln can be an attractive, less expensive alternative to a rotary kiln. In cement kilns, drilling wastes with oily components can be used in a fuel-blending program to substitute for fuel that would otherwise be needed to fire the kiln.
Cement kiln temperatures (1,400 to 1,500 degrees C) and residence times are sufficient to achieve thermal destruction of organics. Cement kilns may also have pollution control devices to minimize emissions. The ash resulting from waste combustion becomes incorporated into the cement matrix, providing aluminum, silica, clay, and other minerals typically added in the cement raw material feed stream.
Recent studies have shown that it is feasible to use such drilling waste as substitute fuel in a cement plant. The drilling mud can be processed by a centrifuge to separate remaining water, compressed by a screw into a solid pump and conveyed.
The cement industry can play a significant role in the sustainable development in the Arab countries, e.g. by reducing fossil fuel emissions with the use of refused derived fuels (RDF) made from municipal solid waste (MSW) or hazardous waste such as oil spilling.
The cement companies in the Middle East can contribute to sustainability also by improving their own internal practices such as improving energy efficiency and implementing recycling programs. Businesses can show commitments to sustainability through voluntary adopting the concepts of social and environmental responsibilities, implementing cleaner production practices, and accepting extended responsibilities for their products.