Deep Panuke Project Description - Encana

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Table 2.11 Processing Location AlternativesAlternative Technical Suitability Cost Commercial RiskTechnically and ConceptEconomically Feasible DeliverabilitySafetyFull Offshore Best technical Lower cost than No specific concerns Yes Equivalent Deals with H 2 S at sourceProcessing solution (H 2 S and onshore processingthereby minimizing safetycondensate removalrisk related to pipelineat source to producetransport of gas to shorenatural gas)OnshoreProcessing(with minimaloffshoreprocessing fortransportation)OnshoreProcessing(Long subseatieback)Higher risk thanoffshore processingassociated withpipeline integrityTechnically notfeasibleHigher cost thanoffshore processingRisk to Projecteconomics shouldpipeline corrode and beout of service for anextended period of timeIncreased risk to projecteconomics due topipeline integrityconcernsYes Equivalent Transports H 2 S from offshoreto populated area (increasedsafety risks)Environmental ImpactDeals with H 2 S at source, therebyeliminating risks to the onshoreenvironment.Fewer sensitive environmental receptorsand greater acid buffering capacity in theoffshore marine environmentA greater number of sensitiveenvironmental receptors and thereforepotential impacts onshore with regard toH 2 S emissionsIncreased corrosion risk associated withtransmission of H 2 S in a 176 km pipelineincreases risk of gas releaseOffshore/Onshore(IntermediateCase)Duplication of somefacilities onshore andonshoreHighest – mustduplicate elements ofprocessing offshoreand onshoreNo specific concerns NoOffshore/Onshoreusing SOEPSubsea Tie-inTechnically feasible Yet to be determined Yet to be determined Yes Marginal increasedrisk when compared tofull offshoreSame as offshore processing Marginal increased advantage over fullprocessing by reduction of benthicdisturbance resulting from a shorterpipelineDeep Panuke Volume 4 (Environmental Assessment Report) • November 2006 2-68
Onshore Processing with Minimal Offshore FacilitiesOnshore processing with minimal offshore processing was based on minimally treating the gas such thatthe gas and the condensate could be transported, in a common pipeline, for processing onshore. Onshoreprocessing involves some processing offshore including dehydrating the gas and separating the waterfrom the condensate so that the pipeline may be operated free of water. The removal of water isnecessary for corrosion control and hydrate prevention. The offshore facilities for the onshoreprocessing alternative include separation, TEG dehydration, condensate treatment, produced waterhandling and a multiphase export pipeline for the combined gas and condensate streams. The associatedonshore facilities include a slugcatcher, separation, gas sweetening, sulphur recovery, TEG dehydration,gas compression, gas dewpointing, condensate treatment, and sour water handling. Onshore processingis more expensive than the offshore processing due to the duplication of facilities at both the offshoreand onshore locations including separation, TEG dehydration, condensate treatment, compression, andsour water handling. Due to economic reasons, the onshore processing case was rejected.Full Onshore Processing with Long Subsea Tie-BackAnother alternative for providing full onshore processing would be to use a “long subsea tie-back”. Thisalternative involves using only the reservoir pressure to push reservoir fluids to shore via a 176 kmcorrosion-resistant pipeline. An offshore subsea gathering system, with a subsea manifold, collects allthe fluids produced from the subsea wells and transports them to shore via a multiphase pipeline. Theonshore plant provides full processing of the reservoir fluids and contains all the process equipmentsimilar to the offshore processing alternative plus a slugcatcher, sulphur recovery plant and sour waterhandling equipment.Onshore processing creates additional safety and human health risk associated with handling sour gasonshore near populated areas. The probability of a large-scale accidental release of sour gas from aprocessing facility, albeit remote, is a serious concern. While the oil and gas industry has proven capableof handling sour gas in populated areas, EnCana submits that the most prudent approach is to minimizerisk by locating sour gas facilities away from populated areas.While proven and effective mitigation measures exist to address safety/occupational health andenvironmental concerns, EnCana’s preferred approach for this Project is to deal with the sour gas atsource to minimize overall risk. While population density in the onshore project area is low, therewould nevertheless be some added risk to the public with an onshore compared to offshore acid gashandling site. In general, there are many more environmental receptors onshore and acidic bufferingcapacity is far greater in the marine environment.Deep Panuke Volume 4 (Environmental Assessment Report) • November 2006 2-69
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2 PROJECT DESCRIPTIONThis section p
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Potential Radioactive Components: T
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2.2.2 Subsea Wells and FlowlinesThe
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2.2.3.1 M&NP OptionThe proposed pip
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The onshore portion of the pipeline
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2.3 Construction and Installation2.
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2.3.2 Export PipelineA proposed pip
Page 18 and 19: A dedicated subsea umbilical will b
Page 20 and 21: Table 2.2 Construction MethodsCateg
Page 22 and 23: These subsea structures may be fast
Page 24 and 25: For the new production and injectio
Page 26 and 27: Figure 2.8Typical Production Well S
Page 28 and 29: 2.3.8.1 Drilling Fluid ProgramWater
Page 30 and 31: Table 2.4 Hydrostatic Fluid Dischar
Page 32 and 33: Acid GasInjectionFeed GasCompressio
Page 34 and 35: Although the M&NP Option is the onl
Page 36 and 37: Spent TEG has no measurable H 2 S a
Page 38 and 39: Table 2.7 Water CompositionComponen
Page 40 and 41: 2.4.2 Utilities2.4.2.1 Electrical P
Page 42 and 43: will be designed considering emerge
Page 44 and 45: zones over the pipeline although th
Page 46 and 47: 2.7 Emissions and DischargesEnCana
Page 48 and 49: Table 2.8 Routine Project Emissions
Page 50 and 51: 2.7.1.1 Air PollutantsThe following
Page 52 and 53: esult in eye irritation, respirator
Page 54 and 55: Typically, a re-entry and completio
Page 56 and 57: 2.7.5.3 Deck DrainageDuring constru
Page 58 and 59: 2.9.2 Pipeline Leak PreventionThe p
Page 60 and 61: 2.9.5 Subsea Protection StructuresT
Page 62 and 63: • consider concept alternatives f
Page 64 and 65: Table 2.10Centre Substructure Type
Page 66 and 67: is much more weather-dependent than
Page 70 and 71: After carefully considering the con
Page 72 and 73: Flaring acid gas consists of direct
Page 74 and 75: Table 2.13Produced Water Disposal A
Page 76 and 77: Therefore, injection into an annula
Page 78 and 79: Use of a dedicated condensate pipel
Page 80 and 81: is taken offshore on a special lay
Page 82: Table 2.15Acid Gas Injection Locati
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Deep Panuke Project Description - Encana

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