Air Emissions, Noise and Light Emissions. During development and production operations the project activities will emit varying amounts of airborne emissions, including carbon monoxide (CO), oxides of nitrogen (NOx), oxides of sulfur (SOx), volatile organic compounds (VOCs), and particulate matter. Fugitive emissions of natural gas, which mainly consists of methane (CH4), will be generated from various equipment and components, including seals, valves, flanges, gas turbines, and storage tanks. During development and construction, emissions will be produced offshore and onshore by equipment and vessels from combustion engines, and dust will be generated onshore from earth movement activities and traffic.  

During production, offshore air emission sources will be related to the FPSO, mainly operation of gas turbines for power generation and gas compression. The project has adopted a “zero flaring” design philosophy, and flares will only be used for limited periods during commissioning phase and in emergency cases during operations. During well production tests lasting for approximately 4.5 days per each well, gas from the tested wells will be flared. Dilution and dispersion of air pollutant emissions from the drillship and the FPSO are expected to be rapid and the potential effects on ambient air quality to be limited to a short distance from the emission sources. No detectable effects on ambient air quality onshore are expected considering the relatively limited amount of air pollutants emitted and the distance from shore.  

The project will ensure that offshore facilities and support vessels will comply with the requirements of MARPOL Annex VI and relevant WBG guidelines for thermal power plants and small combustion sources, as applicable.

Gas entering the ORF will be measured, compressed and delivered into the existing national network. The gas will not be stored in the ORF.  Air emission sources will be related to the ORF operation, mainly gas turbines, diesel power generation units and gas compression. A discontinuous air emission source will be a cold vent, which will only be used during commissioning, start-up, shut down and emergency conditions for pipeline and plant depressurization. There are no major industrial activities in the project area of influence and thus no other significant sources of air pollutant emissions. Baseline ambient air quality measurements showed concentrations of nitrogen dioxide, total suspended particles and VOCs within the applicable Ghana EPA national standards, with relatively high levels of sulfur dioxide and PM10, potentially associated with fish smoking process or waste burning in Sanzule and Eikwe communities and road construction works. Air emission dispersion modeling, based on available design information with conservative assumptions, did not identify any potential significant impacts on human receptors and vegetation due to emissions of air pollutants generated by both onshore and offshore operations. The ORF contribution in terms of NO2 daily concentrations modeled at the villages of Sanzule and Eikwe accounts for maximum 37% of background concentrations. Results of the model are well below the national standards for SO2, NO2 and CO. The model showed that FPSO emissions will be rapidly dispersed in an offshore environment, not affecting closest human receptors located on the coast. The modeling will be refined during ORF and FPSO final design to inform the identification and development of a package of air emission reduction measures to ensure compliance with WBG emission guidelines and mitigate the residual impacts on sensitive receptors. A pre-construction survey will be carried out in order to collect more detailed baseline data at the sensitive receptors located near the onshore facilities. An air emission and ambient air quality monitoring program will be implemented.   

The drillship, the FPSO and vessel operations will generate noise into the marine environment. Trenching activities will also generate noise levels from shore up to 2 km from the coastline; then the pipeline will be laid on the seabed.

The low-frequency noise levels from offshore drilling and production activities are relatively weak in intensity and are expected to rapidly decay within a 1 km radius of the source.  These levels are considered not to be enough to cause hearing loss, discomfort, or injury, but they can be detected and produce some behavioral responses (e.g., avoidance) in marine mammals, particularly baleen whales, and in fish. Sea turtles are less sensitive to changes in marine noise levels from marine activities.  Marine mammals do often congregate around offshore platforms and become accustomed to predictable noise, as in the case of ships following a shipping route and stationary sources. However, sensitive species will maintain an avoidance behavior in case noise levels are above damage thresholds, which is expected to occur in 1-3 km radius from noise source. Although overall the impact on marine mammals and sea turtles was assessed as being of minor significance, Eni Ghana will develop and enforce a policy and relevant procedures to ensure that operations of drillship, support vessels and helicopters minimize disturbance to marine mammals and turtles. 

The main noise emission sources at the ORF during production operations will be the gas turbines of the power generation unit, the diesel power generators and the compressor station. Discontinuous noise emission sources will be the cold vent, the heliport, and equipment and vehicles used for maintenance and inspection activities. Relatively high noise levels for a rural environment were monitored at Sanzule and Eikwe, without significant variations between day time and night time. Average baseline noise level at Sanzule and Eikwe exceeded the EPA permissible day-time noise level of 55 dB(A) and night time level of 48 dB(A) for residential area, possibly due to natural sources (sea waves breaking at the beach) and community activities. Noise propagation modeling, based on available design information with conservative assumptions, showed that the project contribution meets Ghana EPA noise limits and WBG guidelines both during day time and night time and complies with the WBG 3 dB(A) incremental criterion in the residential areas.  The modeling will be refined during ORF final design to inform the identification and development of a package of noise attenuation measures able to mitigate the residual impacts on the community receptors. A pre-construction survey will be carried out in order to collect more detailed baseline data at the sensitive receptors located near the onshore facilities. An ambient noise monitoring program will be implemented, and seasonal constrains for construction activities in relation to the local fauna sensitivity (e.g., avoiding reproduction period of turtles, and with respect to bird species of the Amansuri Wetland) will be considered and implemented. 

Eni Ghana will ensure routine inspection and maintenance of engines, generators, and other equipment, and use of low-sulfur diesel fuel will be defined as part of the project’s environmental monitoring program.

Light emissions from project facilities, vessels and FPSO may be visible at night at considerable distances, depending on weather and sea conditions. While no impacts are expected to turtle nesting or foraging area from the artificial light associated with drilling and production operations offshore due to the their distance more than 40 km from the coast, seabirds may be attracted by the lights during nights, especially during poor weather, i.e. overcast nights. Although it is expected that disturbance will be localized, only affecting a small number of birds offshore, and temporary, the project will implement measures to control and reduce overall light intensity to the extent practicable, without adversely affecting maritime or operational safety.

Greenhouse Gas Emissions and Resource Efficiency.  All associated gas (with the exception of the gas used for the FPSO gas turbines and each other end user on the FPSO after fuel gas conditioning) will be separated, dehydrated, compressed and re-injected into the formation. The FPSO will have the capacity to handle and re-inject 100% of associated gas volumes - 150 millions of standard cubic feet per day (MMscfd) - to the field through three gas injection wells.  Inert gas will be used for blanketing process equipment and purging the flare stack. 

The principal sources of GHG from the project will include the following: (i) main power generation systems on the drillship, FPSO and ORF; (ii) engine emissions from project installation/construction vessels and supply/support vessels; and (iii) gas flaring and venting during commissioning, maintenance and emergency situations.

The annual GHG emission during production operations is estimated at approximately 400,000 tons CO2 equivalent per year. As required for projects with GHG emissions greater than 25,000 tons CO2 equivalent per year, Eni Ghana will implement a quantification program for GHG emissions, according to an internationally recognized emissions estimation methodology, for both development phase (including drilling, completion, installation of subsea facilities, FPSO and ORF, and pre-commissioning/commissioning) and production operations, and will establish annual review programs to identify areas of improvement and GHG emission reduction. Eni Ghana has committed to implement a Zero-Permanent Flaring policy, and will implement measures for minimization of venting and flaring (consistent with the Global Gas Flaring and Venting Reduction Voluntary Standard) and minimization of fugitive emissions.

Energy efficiency principles will be built into the design to minimize power requirements during production operations. All three gas turbine units installed on the FPSO will be equipped with a Waste Heat Recovery Unit for recovery of exhaust heat. Eni Ghana will define energy saving projects to be included in the Strategic Plan developed at the corporate level. 

Fresh water consumption will be limited during both construction and operations. Groundwater wells needed for water supply will be installed at sufficient depths to access the deep freshwater aquifer. A Water Risk Assessment study is under preparation and will quantify effects of groundwater abstraction and ensure that there will not be measurable impacts on community water resources. 

Wastewater Treatment and Disposal. Wastewater streams associated with development and production operation activities will include hydrotest water, produced water, cooling water, gray water and sewage, bilge water, deck drainage, ballast water, cooling water. Hydrostatic testing of offshore equipment and lines will involve pressure testing with filtered seawater to verify equipment and pipeline integrity. Only environmentally friendly inhibitors will be used and their discharge concentrations will be in line with local and international standards. A Hydrotest Water Disposal Plan will be prepared that considers points of discharge, rate of discharge, chemical use and dispersion, environmental risk, and monitoring. 

The drillship, the pipe-laying vessel and other support vessels will adhere to MARPOL regulations and will be equipped with wastewater treatment units for the treatment of civil wastewater.  At the ORF construction site, all wastewater produced will be treated as waste, properly stored and disposed off-site at a licensed facility.  

During offshore production operations, all wastewater streams will be discharged to the sea after treatment on the FPSO, except produced water which will be reinjected into a suitable geologic formation through reinjection wells. Domestic wastewater will be treated in a purification system before being discharged to the sea in accordance with MARPOL regulations. Non-contact cooling water (approximately 1700 m3/h) will be discharged to the sea with a maximum discharge temperature of 31 °C and controlled biocide/antifouling concentrations. As sea surface temperatures in offshore Ghana typically vary between 27 - 29°C, the impact of cooling waters discharged will generate a limited increase of temperature of the seawater that will only be noticeable in the immediate vicinity of the discharge point. Oily waters (bilge water) will be collected and treated in a separator, sent to a collection tank and then discharged to the sea. Recovered oil will be filtered and collected in a tank for onshore disposal. Drainage systems will be provided to handle effluents produced from the FPSO topside facilities, including (i) a non-hazardous open drain system, collecting drainage from deck areas; (ii) a hazardous open drain system, designed to collect drainage from open areas within hazardous areas of the process where oil spills are possible; and (iii) a closed drain system, collecting drainage from equipment. The closed drain drum will have sufficient capacity to accommodate the largest single liquid inventory. 

A produced water treatment system will be installed on the FPSO to remove oil and solids from produced water and to comply with reinjection requirements and, in case of injection system unavailability, with overboard discharge regulations and WBG guidelines (oil and grease not to exceed 42 mg/L daily maximum or 29 mg/L monthly average). The treatment system will consist of a degasser, a cooler, two stage oil/water separation in two slop tanks connected in series, and a hydrocyclone system to further de-oiling. The treatment system will be sized to process 45,000 bpd of produced water and ensure an oil content of 20 ppm in treated water. The project will involve the total reinjection of produced water; however, it will be possible to monitor eventual overboard discharge of produced water through a sampling point which will be installed on the FPSO.

In order to reduce the risk of introduction of alien species due to ballast water discharge, the project will adhere to IMO Guidelines for the Control and Management of Ship’s Ballast Waste and Sediments (Ballast Water Management Convention). No ballast activities will take place in the near shore area and over the continental shelf. Tanker vetting procedures will be required to ensure that all shuttle tankers have segregated ballast water tanks to limit the risk of oil-contaminated discharges. Vetting procedures will also include requirements for ballast water exchange. 

The wastewater effluents from the ORF operation will be mainly civil water and storm water, as in the ORF process only the gas stream will be present and thus no liquids will be generated and no chemicals will be added into the gas stream. Storm water collected from potentially contaminated areas will be disposed of offsite at licensed treatment plants.

Waste and Hazardous Materials Management. The project will generate both non-hazardous wastes and hazardous wastes. Eni Ghana has in place a Waste Management Plan as part of the HSE IMS, which will inform the development of a project Waste Management Plan. The plan will cover the collection, storage, treatment, transport, disposal, discharge, reporting and data management of all the waste to be generated during offshore and onshore operations, including drilling, infrastructure and facilities construction, operations and maintenance. The plan will include site-specific procedures detailing how waste is to be managed, treated and disposed of, identifying the waste types and streams and defining waste handling contractors and final disposal sites. Proper segregation of waste will facilitate the reuse and recycling of suitable waste streams. The plan will define waste tracking procedures to allow waste consignments to be tracked from source of generation to end point. All waste producers (operator and contractors) will maintain a waste register and prepare an inspection and reporting plan.

Burn baskets will be used only for non-hazardous canteen and cabin waste on the drilling rig, the FPSO, the pipe laying barges and the support vessels, in compliance with MARPOL Annex V.  During FPSO operations, small quantities of hazardous waste will be produced mainly due to equipment maintenance and operation. Food waste will be shredded and dumped at sea through a sieve with an aperture of 25 mm as specified by MARPOL regulations.

At each project facility (drillship, FPSO, ORF) dedicated waste storage areas will be equipped with waste containers, clearly labelled, adequately contained and secured. Different waste types will be segregated in order to prevent accidental spillages, fires, soil contamination, loss of integrity and possibility of contact with people and animals. Containers for offshore waste will be in compliance with ISO 1496 or EN 1279.

Only waste management companies approved by Ghanaian authorities and Ghana EPA will be used for transportation, recycling and disposal of wastes generated by the project. Adequate licensed incineration and landfill facilities have been identified in Takoradi. Eni Ghana will undertake periodic audits of third-party waste facilities and sites to verify that wastes are being managed in line with company’s standards and methods, as defined in the relevant contractual agreement.

A Hazardous Materials Management Plan will be implemented to address handling and storage of hazardous material that are used or stored aboard project vessels or facilities, ensuring compliance with Ghana laws and regulations and consistency with WBG guidelines. Hazardous substances will be stored within sealed containers in areas bunded to prevent and contain accidental spills. At the ORF, fuels and other hazardous chemicals will be stored according to industry best practice including containments that can accommodate 150% of the total storage volume and are covered to prevent rainfall entering the containment basin. PCBs, leaded paints, chromium-based cooling water treatment, mercury-filled meters, asbestos-containing material and ozone-depleting substances will be prohibited. Hazardous material training will be provided to project personnel.

Drilling Fluids and Cuttings Management. The total volume of cuttings to be generated from each well is expected to amount to approximately 800 m3. Approximately 400 m3 of cuttings drilled with Water Base Muds (WBM) will be generated from the top two surface riserless intervals of each well. Discharge of WBM and associated cuttings will take place very near the sea bottom and material will settle fairly rapidly, reducing contact with the water column. Once settled the leaching of potential low levels of hydrocarbons and metals, if any, into the water column will be slow.  

The bottom sections of the wells will be drilled with Synthetic Based Muds (SBM), which will be recovered and treated onboard to reduce residual Non-Aqueous Drilling Fluids (NADF) retention on dry cuttings to a maximum of 2% of weight content. Used SBM will be treated in a solids treatment system (vibrating screens, a desilter, desander, and centrifuges), which separate the mud from the drill cuttings. Recovered mud will be reconditioned in dedicated tanks and pumped back into the well. Cuttings will be treated in cutting dryers and then will be discharged from the drillship. Approximately, 400 m3 of drill cuttings and an associated 8 m3 of residual NADF on cuttings will be discharged to sea from the bottom sections of each well (assuming 2% retention). Eni Ghana has specific company guidelines for the management of the cuttings, and will optimize the operational performance of solids treatment equipment on-board drillship to ensure oil on dry cuttings measurements achievable is maximum 2%. Ghana EPA regulation permits the discharge into the sea of drill cuttings contaminated by synthetic/pseudo oil based mud system with a residual oil on cuttings content less than 3% of dry matter if discharged beyond 500 m water depth (“Ghana EPA Guidelines for Environmental Assessment and Management in the Offshore Oil and Gas Development” article 12 and section 7). However, the EPA, in the permit issued in relation to the OCTP Block Development project, stated the requirement of ensuring that NADF cuttings discharged to sea must have an oil concentration lower than 2% by weight on dry cuttings. Above the 2% there is a surcharge regime up to 10% oil on cuttings. Above 10% oil on cuttings offshore discharge is prohibited.

These levels are above the WBG guideline of 1% on oil content on cuttings disposed to sea. Exceptions to the WBG guideline are acceptable where a project’s environmental assessment provide a full and detailed justification of the proposed alternative for ocean disposal. As part of the drill cuttings study, modeling was undertaken to quantify the transport, dispersion, and bottom deposition of discharge drill cuttings. Low toxicity and rapid dispersion of drilling discharges due to significant water depth and strong currents will cause limited or no measurable impact to the biological environment. The results of the model showed that the effects of the water column would be temporary with maximum suspended solids up to 2.5 mg/l within 300 m of the release location. Dispersion will allow a return to background levels in a relatively short time. Dispersion also will minimize benthic impacts. Sea bed depositions of cuttings will be limited and the thickness of drill cuttings on the seafloor will not exceed the threshold value of 50 mm, reaching a maximum value of 35 mm at the top of the deposited mound near the release location. According to the model, most of the area affected would result in a layer of cuttings of less than 1 mm thickness. NADF adhered to the cuttings would settle primarily within a region with an area on the seafloor of approximately 1.2 km2, with total hydrocarbon concentrations expected to reach a maximum of 40.8 g/m2 within 50 m from the discharge point. Impacts on benthic communities of soft bottom areas will only be measurable within a few hundred meters of each drill site, and re-colonization of these areas should happen within a few years.

The following mitigation measures will be adopted to further minimize the impact of drill cuttings and fluid discharge on the marine environment:

(i) use of additives in the WBM that will be inert and eco-friendly, preferably included in the PLONOR list (Pose little or No Risk to the environment) (OSPAR, 2013). WBM and associated cuttings discharged will accomplish the toxicity requirements set by the EPA;
(ii) the rate of WBM and cuttings discharge to the sea will be monitored;
(iii) use of the lowest feasible chemical contents in the SBM, prioritizing chemicals included in the PLONOR list and those with lowest hazard according to the CHARM methodology developed by OSPAR;
(iv) treated dry cuttings for sections drilled with SBM will be discharged via a caisson at least 50  m below water surface. In any case, a good dispersion of the solids on the seabed will be demonstrated;
(v) the content of mercury and cadmium in the bentonite used will be monitored to ensure lowest levels possible and within the limits defined by Ghana EPA and consistent with WBG guidelines.

Oil Spill Prevention and Response. As discussed in the previous sections, the project facilities will be designed with a range of inherent measures aimed at minimizing the risk of potential oil and chemical spills. Spill prevention measures include: (i) process safety management and training of personnel; (ii) asset integrity assurance, through routine operator inspections, maintenance inspections and internal and external audits; (iii) process isolation, including emergency shut-down system as an integral part of an Integrated Combined Safety System, providing full alarm and fault status indication as well as valve isolation; (iv) incorporation of industry lessons; and (v) emergency preparedness in place.  

Eni Ghana’s “Development Drilling & Production Operations Oil Spill Contingency Plan – OCTP Block” (OSCP), which considers potential spill scenarios for both development drilling and production phases, is structured consistent with the International Petroleum Industry Environmental Conservation Association (IPIECA) guidance and conforms with relevant WBG guidelines. The OSCP is based on a three tiered response approach, categorizing potential oil spills in terms of their potential severity and the capabilities that need to be in place to respond. Oil spill risk assessment and quantitative modeling, based on the potential surface and subsurface oil spill release scenarios, have been conducted. Both deterministic and stochastic oil spill modelling were done using SINTEF’s Oil Spill Contingency And Response (OSCAR) software, and covering a wide range of events, such as combinations of different release points, spill duration, oil characteristics, and total volume released. For each event the most probable (i.e. highest frequency) and the most severe (i.e. largest volume released) scenarios have been simulated as worst cases. An assessment of potential oil-spill related impacts to offshore and coastal environmental resources, including turtle nesting beaches, has been conducted. Eni Ghana will finalize the OSCP before development drilling, and measures will include an environmental lead as part of the response team and clear mechanism of escalation of response effort based on coastal and biodiversity sensitivity.  

Eni S.p.A is a participant member of Oil Spill Response Limited (OSRL), an industry-owned cooperative which exists to respond effectively to oil spills worldwide, and has therefore immediate access to OSRL’s Tier 2 and Tier 3 spill response technical advice, resources and expertise 365 days a year on a 24 hour basis, including West And Central Africa (WACAF) aerial surveillance and dispersant application services. Eni Ghana will also establish mutual aid agreements with other operators in Ghana.