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Characteristics of oil based muds and influence on the environment

Jamrozik A., Protasova E., Gonet A., Bilstad T., Żurek R.

AGH Drilling, Oil, Gas

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2016

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Vol. 33, no. 4

681--691

EN

Oil based muds (OBM) are highly important in well drilling. Water based muds (WBM) and synthetic based muds are not providing sufficient qualities in fulfilling all of the functions of OBM. OBMs ensure more efficient drilling but also disadvantages such as higher initial cost, more stringent pollution controls and reduced effectiveness of some logging tools. Expenses for mud are reaching 10–15% of total well cost. However, high costs are still low compared to expenses for corrective measures in the case of using mud with poor properties, which could lead to drilling disruption as well as excessive time and cost. OBM and cuttings are saturated with toxic compounds and if discharging to sea poses ecological threats. Perhaps the most hazardous oil component for aquatic organisms are low-boiling aromatics, which consist of benzenes and naphthalenes both soluble in water. Additionally, the higher-boiling aromatic fractions are of high environmental interest due to their persistence in sediments, leading to enzyme induction, cellular dysfunctions, genetic alterations, and chronic effects on organisms. There is a difference in volume of generated waste between using water- and oil-based muds. WBM produces 7,000–13,000 bbl of waste per well. Depending on well depth and diameter 1,400–2,800 bbl are drill cuttings. OBM generates mush less waste as the mud is usually recycled and only drill cuttings with volumes of 2,000–8,000 bbl per well need treatment prior discharge. This paper discusses the hazardous effect of toxic compounds in OBM and evaluates the efficiency of different OBM treatment towards zero discharge.

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Categorization of the drilling waste as a criterion of selecting the methods of their detoxication, recovery and management

Gonet A., Fijał J., Jamrozik A., Stryczek S., Bilstad T.

AGH Drilling, Oil, Gas

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2016

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Vol. 33, no. 2

447--454

EN

Being aware of the problems affecting our environment, novel technological solutions have been dealt with to improve its quality. Mining is a sector generating substantial volume of waste and it also refers to drilling operations. On the basis of laboratory investigations and the analyses of legal regulations, three categories of drilling waste have been distinguished depending on the environmental impact of the waste and on the potential technologies of their treating and successful utilizing. The essentials of the solutions proposed have been presented and for each of the categories a processing flow chart has been prepared. At the ends of the processing lines, the flow charts specify the possibilities of utilization of the final products.

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Improved oil production by membranes

Nair R. R., Saltveit K. J., Protasova E., Bilstad T.

AGH Drilling, Oil, Gas

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2015

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Vol. 32, no. 1

221--232

EN

The objective of this presentation is to show connections of activities leading to improved oil recovery (IOR) when prospecting for oil and gas. Increased wettability of injected water into the reservoirs is caused by specific ions. Technical limitations for production of designer water from seawater by membrane separation are high-lighted. Desirable characteristics of designer water are low NaCl concentrations and high divalent ion concentrations for improving wettability of Crude Oil, Brine and Rock (CBR). Experimental setup incorporated nanofiltration (NF) membranes for ion separation. Retentate from NF contains the main constituents of Designer Water. A property of NF is to retain divalent ions. Performance of the membranes was evaluated in terms of flux and rejection under varying feed compositions, pressures and recovery rates. The research comprised a technical-economical study for salt separation. Results were evaluated in terms of desalination efficiencies and energy requirements. A sensitivity test, spiking Na2SO4 in the feed seawater, showed a decrease in retention of Cl with increasing SO42- concentrations. A reduced permeate flux resulted, however, with increasing Na2SO4 concentrations.

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Ervironmental friendly drilling fluid management offshore Norway

Bilstad T., Jensen B., Toft M.

AGH Drilling, Oil, Gas

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2014

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Vol. 31, no. 2

191--197

EN

Types and amount of fluids utilized when drilling a well determine to which extent the drilled cuttings are legally considered hazardous waste. The main categories of drilling fluids are oil based (OBM), water based (WBM) and synthetic based mud (SBM). The purpose of adding fluids to the drilling operations is to cool and lubricate the drill bit, to stabilize the well bore, to control subsurface pressure, to control formation pressure, to control well stability. to control corrosion, and to carry cuttings to the surface. Historically, cuttings from drilling sub-surface wells have been depositeddirectly from the platform to the seabed. However, environmental laws and regulations for the Norwegian offshore sector prohibit such practice when the oil on cutting exceeds 1 % by weight. Re-injection of cuttings as a slurry into subsurface formations is still practiced. Due to migration, leaks, re-entering of slurry onto the seabed, and collapsing formations this disposal method is on a decline. Transport of oily cuttings to shore for final treatment is the preferred Norwegian practice. However, cutting treatment on platforms is also continuousl yevaluated. For logistics and cost reasons, as well as health, safety and environmental (HSE) and working environment reasons, emphasis is put on offshore waste minimization, reuse and recycle.Ten onshore locations in Norway are currently receiving cuttings for further treatment and fluid recovery. The treated cuttings are for the most part disposed in landfills.

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Offshore drilled cuttings management

Bilstad T., Stenberg E. S., Jensen B., Larsen T., Toft M.

AGH Drilling, Oil, Gas

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2013

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Vol. 30, no. 1

47--50

EN

The search for offshore fossil fuels generates large volumes of drilled cuttings which under certain conditions are defined hazardous, negating disposal at sea. Much of the cuttings end up in onshore landfills. The types of fluids used in well drilling operations determine to which extent the cuttings are considered hazardous. The three main types of fluids are oil based mud (OBM), water based mud (WBM) and synthetic based mud (SBM). The purpose of adding fluids or mud in the drilling operations is to cool and lubricate the drill bit, to stabilize the well bore, to control subsurface pressure, formation pressure, well stability and corrosion, and to carry cuttings to the surface. OBM is based on either diesel or mineral oil. One advantage of OBM is enhanced drilling performance, especially in technical challenging environments. A drawback, however, is the toxicity of OBM, prohibiting discharge of cuttings to the marine environment. Drilled cuttings are rocks produced during drilling operations, becoming coated with drilling fluids. Historically, cuttings have been disposed to sea. However, recent environmental laws and regulations prohibit such practice. Re-injection of cuttings as a slurry into subsurface formations has also been discontinued due to leaks and re-entering of slurry into the bottom waters. Transport of cuttings to shore is therefore the choice. For logistics and cost reasons emphasis is put on offshore waste minimization and reuse/recycle. Total fluid management (TFM) leads to environmental impact reduction (EIR). Minimization of drilling fluids and reuse of fluids lead to cost reduction. Volume of cuttings is reduced through directional drilling and by drilling smaller diameter holes. Synthetic based drilling fluids (SBM) are replacing OBM. Drilling wastes are further separated into a fluid and a solid phase. The solids may be used for road and other construction purposes, whereas the OBM is burned for energy recovery. The purpose of the thermo-mechanical cuttings cleaner (TCC) is to convert hazardous oily cuttings into useful products. TCC facilities are only available onshore in Norway. However, offshore TCC units will in due time be introduced, negating the need for transport of cuttings to shore. Cuttings are allowed disposed to sea when no toxic fluids are attached. TCC separation is accomplished by generating temperatures of 240-300 degrees of Celsius sufficient for evaporation of oil and water from the mineral solids.