Zero Waste Discharge Practices followed during Oil Well Drilling Operation at Columbia, Latin America : A case study

Transcription

1 Zero Waste Discharge Practices followed during Oil Well Drilling Operation at Columbia, Latin America : A case study N. N. Ray, Dr. Naveen Raj. Mrs. Vineeta Sattawan Sectoral HSE, Western Onshore Sector, ONGC, Vadodara ray_nikhil@yahoo.co.in Oil well drilling activity includes handling of a number of chemicals, movement of heavy equipment, running of machineries, burning of fossil fuel, consumption water etc and generation of wastes in the form of drill cuttings and spent drilling fluid. Oil and gas exploration and production (E&P) activities are responsible for serious accidents around the world, which in some cases were irreversible for the environment. The risks from these activities have been providing changes in legislation, which has become more rigorous and specific in this sector, especially in waste management. In view of the sustainable development and stringent environmental regulations, it becomes very important that footprints of operations are not left behind to ensure minimum damage to environment. All these conditions pose a challenge for the operational personnel to maintain high standards of environment management which can only be met by following zero waste discharge practices and its effective implementation on field This case study discusses the practices adopted for the zero waste discharge which was used for the first time in ONGC Videsh Limited at Colombia during the drilling of the well Kamal#1 at Columbia, Latin America. The sources of solid wastes generated during drilling activity include drill cuttings separated from shale shaker, rejected drilling mud with sand and silt separated in dasander and desilter and the spent drilling fluid which can no longer be reused. Drill cuttings consist of sedimentary rocks, which are relatively inert. Small amount of mud coated on the drill cuttings also form part of this solid waste. The quantities and characteristics of drill cuttings depend on the nature of formation (sedimentary rock) and depth of the well. The zero waste discharge technique helped in complete assimilation of drill cuttings generated during drilling operation with the native soil without creating any adverse impact on the environment. The technique for treatment of drill cuttings was well appreciated by the ANH-Regulatory authority of Columbia The drilling fluid popularly known as drilling mud used for drilling the well consists of clay and a number of additive chemicals used for treatment of drilling fluid. The drilling fluid waste generated during drilling operation was collected in designated catch tank and with the help of specially designed centrifuge, the clay and associated water was separated. Some part of the clay was reused for making the drill fluid and the rest was transported to drill cutting treatment pits The water separated from drilling fluid was treated with chemicals in the separate waste water treatment tanks located at site. The waste water was treated with appropriate chemicals for disposal as per Colombian regulatory requirements These waste management practices not only prevented the discharge of wastes in the first place but the wastes generated were also treated and disposed of in eco-friendly manner without causing any harm to the environment.

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3 a) Treatment of drill cuttings In the present case study, onsite Mix-Bury-Cover (MBR) method is employed to dispose off drilling cuttings. Stage 1. The drill cuttings generated during the drilling operation are collected in a drill cutting tank (catcher tanks) Stage 2. Drill cuttings are periodically transported to specially designed drill cutting pits at drill site. Stage 3. The drill cuttings in the drill cutting pits are treated with appropriate chemicals to make it compatible with the properties of native soil. The chemical other properties like sodium Absorption Ratio, Electrical Conductivity, Heavy Metal & Hydrocarbons & toxicity of the treated cutting were monitored regularly Stage 4. When the properties of the drill cutting are found compatible with the native soil, the cuttings were mixed with the native soil at drill site. At this stage, the chemical analysis report of the drill cuttings is sent to the

4 regulatory authorities of Columbia and the mixing is done only after the inspection by the concerned authority. This technique helped in complete assimilation of drill cuttings generated during drilling operation with the native soil without creating any adverse impact on the environment. The technique for treatment of drill cuttings was well appreciated by the ANH-Regulatory authority of Columbia. b) Treatment of drill fluid (drilling mud): The drilling fluid popularly known as drilling mud used for drilling the well consists of clay and a number of additive chemicals used for treatment of drilling fluid. The drilling fluid waste generated during drilling operation was collected in designated catch tank and with the help of specially designed centrifuge, the clay and associated water was separated. Some part of the clay was reused for making the drill fluid and the rest was transported to drill cutting treatment pits The water separated from drilling fluid was treated with chemicals in the separate waste water treatment tanks located at site. The waste water was treated with appropriate chemicals for disposal as per Colombian regulatory requirements. The treated water chemical properties were monitored regularly at site and after the treated water was found to meet the prescribed disposal requirements some part of the water was reused for drilling operation and the rest was used for regulated land spraying as per the consent requirement issued by Colombian authorities. The technique used for treatment of drilling fluid was inspected by the Colombian regulatory authorities and was well appreciated. c) Other Wastes a) Day to day waste Apart from operational wastes, other wastes such as organic waste from canteen, papers, plastic from office, were collected in separate waste bins having different colour for easy ident ification kept in front of office bunk house, canteen, residential bunk house and derrick floor. All operational personnel were required mandatorily follow the guidelines for use of these bins for appropriate waste. These bins are periodically inspected by HSE officer. The bins are emptied periodically and collected waste was stored in a bunk house having locking arrangement for further disposal to authorized vendor. The bunk house was provided dyke for collection of any spillage.

5 b) Medical Waste The rig had first aid center with the facility of 24hrs doctor and medics. The medical waste like used cotton, syringe, expiry medicine were kept in a container in locked condition. c) Metal & Other Waste The rig had facility to collect all metal waste like cut piece of steel rod, plate, casing protector etc were collected in designated area. Similarly, wooden pieces, condemned accessories were collected. These wastes were disposed periodically and record was maintained. WASTES GENERATED DURING DRILLING OPERATION Drilling activities include the Drill site construction and rigging up, operation of the rig, a drilling mud system, and drill string to make hole.. The drilling rig is used to handle the drill pipe and bit and to set casing to complete the well. Rig operation and maintenance uses numerous systems and various types of machinery. Wastes generated include: Debris, lubricating oil,contaminated soil from heavy equipment (e.g., bulldozers), contaminated rainwater etc. Solid waste generated during drilling activity Two major sources of solid wastes are generated during drilling activity 1. Drill cuttings, separated from shale shaker 2. Rejected drilling mud with sand and silt separated in dasander and desilter Drill cuttings consist of sedimentary rocks, which are relatively inert. Small amount of mud coated on the drill cuttings also form part of this solid waste. The quantities and characteristics of drill

6 cuttings depend on the nature of formation( sedimentary rock) and depth of the well.the volume of drilling waste usually ranges from 1000 to 5000 cubic meter for each well depending on the depth of the well. These drill cuttings are coated with driiling mud, oil and chemical. Quantity of of rejected fine sand and silt vary from 250 kg per day to as high as 1.5 ton/ day depending on the depth of the formation. The sand and silt generated at these units is mixed with mud particles. These solids contain mainly bentonite, barite and small portions or organics alongwith heavy metals. Drilling fluid ( mud ) is used to maintain hydrostatic pressure for well control, carry drill cuttings to the surface, and cool and lubricate the drill bit. Drilling fluids may be fresh water-based, salt water-based, oil-based, or synthetic-based depending upon the conditions encountered. Reserve pits receive drill cuttings and solids, used drilling fluids, rigwash, and surface runoff from the drilling location.wastes generated: Drill cuttings and solids, used drilling fluids, rigwash. Disposal of used/ spent drilling fluid For the onshore operation, the spent drilling fluid is normally transported to drilling fluid recycling plants. The recycled mud is used for further drilling operation. At the drilling fluid recycling plant with the help of solid control equipment undesired solids are removed and after proper dilution with water and chemical treatment, drilling fluid is made suitable for further use. However, the drilling fluid, which cannot be further used, is disposed of on designated landfill sites approved by regulatory authorities. Zero waste discharge management at Drilling rig at Columbia: OVL management has been committed for the protection of environment by adopting best available technology. In persuasion of achieving excellence in environment management, during the drilling of the well Kamal#1 at Columbia, Zero waste discharge management system was used for the first time in OVL. By using this technology, all the drilling wastes generated during the drilling operation were collected, treated and disposed of in eco-friendly manner