9.6 Interfield Pipeline Installation and Commissioning and Operation

Transcription

1 9.6 Interfield Pipeline Installation and Commissioning and Operation As described in the Project Description (Chapter 5.7), Phase 3 will tie-in to the existing Azeri Project marine export pipeline infrastructure to export its oil and gas to the onshore terminal at Sangachal. This will require the installation of three infield pipelines from the offshore facilities and connection to the existing pipelines via pre-installed wye pieces as described in Table 9.17 below. Table 9.17 Phase 3 Infield Export Pipelines Infield line To Length (km) 30 oil line Phase 2 30 oil pipeline oil line Phase 1 30 oil pipeline gas line Phase 1 28 gas pipeline 2.0 The results of the impact assessments of the installation, commissioning and operational activities associated with these Phase 3 infield pipelines are described below Environmental Impacts The results of the environmental impact assessment are summarised in Table Pipeline installation and commissioning will be conducted over a relatively short period of time. It is anticipated that installation, tie-in and commissioning activities will not exceed 50 days, 20 days and 30 days respectively for all three infield pipelines. Furthermore, once installed, the pipelines will cover only a small area of the seabed. As such the residual environmental impacts associated with these activities are ranked low and are not predicted to be significant ACG Phase 3 ESIA Chapter 9 9/55

2 Table 9.18 Summary of Environmental Impact Assessment for Interfield Pipeline Installation Commissioning and Operation ID Activity Environmental Aspects Environmental Mitigation Cumulative Contribution Environmental Impact Significance Justification / Comments Residual Environmental Issues to be Addressed E Infield Pipeline Installation, Commissioning and Operation E1. Installation and commissioning pipelay vessel and vessel support Atmospheric emissions, noise, wastes, liquid discharges. Bilge water, sewage water standards and control; All wastes shipped to shore; Waste management planning and implementation; L As B1. As B1 Refer to Section Lay barge anchoring procedure plan. E2. Installation and tie-in of pipelines, flowlines and umbilicals Physical seabed disturbance, physical presence. As E1; Structural frames installed to protect wyes for tie-in. L As B1 Narrow pipeline corridor used. Concern over the disturbance of the benthic habitat raised during consultation. Benthic sensitivity Refer to Section E3. Rectification of freespans and crossing existing lines Physical seabed disturbance, physical presence. As E2; Crossing supports installed to protect existing lines. L As E2 As E2. E4. Testing and commissioning (hydrotesting) Liquid wastes. Interfield oil lines hydrotest waters transferred to terminal for treatment and disposal; Gas line hydrotest water to be discharged offshore careful selection of chemical additives using Chemical Selection Management system; L Discharge from gas line only and relatively low volume offshore, will disperse rapidly. Regulator concern over discharges to the Caspian. Assurance of chemical selection management Refer to Section The use of chemical additives to hydrotesting water will be challenged in line with the Project HSE Standards; E5. Pigging of pipelines Solid wastes, liquid wastes Pigging required for oil lines only. Pigging wastes sent to shore for incorporation into process or treatment/disposal as per the Waste Management Plan; Material selection and chemical use for the water injection flowlines removes the requirement for routine pigging. Use of wax inhibitor to prohibit wax build up L Low residual impacts but cumulative waste generation issue across AzBU activities. Issue of waste management raised during consultation. Waste treatment & disposal Refer to Section and Section ACG Phase 3 ESIA Chapter 9 9/56

3 Vessel emissions and discharges Up to 10 vessels will be present at the installation location during the installation and commissioning programme including the pipelay barge, anchor handling vessels, pipe haul barges and other attendant vessels. This will result in additional emissions to the atmosphere from vessel engines and exhausts and discharges to the sea of treated sewage waters and bilge waters. With respect to effluent discharges all of these vessels will be subject to the same operational controls as described in Section above in that effluents will be treated to the required project standards prior to discharge. Where vessels do not have effluent treatment facilities the effluents will be containerised then transferred to shore for disposal. The volumes of sewage waters that will be generated are shown in Table It is assumed that each person will produce 0.22 m 3 grey water and 0.1 m 3 black water per day. Table 9.19 Estimated Volume of Sewage During Interfield Pipeline Installation and Commissioning (m 3 ) Activity Vessels Number Of Vessels POB Duration (Days) Grey Water (m 3 ) Black Water (m 3 ) Lay-barge ,310 1,050 Anchor handling vessel Pipeline installation Pipe-haul barges & tugs Diving Support vessel Survey vessel Pipeline tie-in Lay-barge Diving Support vessel Pipeline commissioning Tugs TOTALS 5,513 2,506 Total emissions to the atmosphere that will be released from all vessel activity for the pipeline installation and commissioning programme, based on predicted diesel consumption rates and the duration of the activities are shown in Table Table 9.20 Estimated Emissions to the Atmosphere during Interfield Pipeline Installation and Commissioning (tonnes) Activity Duration (Days) Emission species CO 2 CH 4 CO NO x SO x 1 PM NMVOC Pipeline installation 50 9, Pipeline tie-in 20 2, Pipeline commissioning 30 2, TOTALS 14, PM Particulate Matter NMVOC Non-Methane Volatile Organic Compounds 1 Based on an H 2 S content in diesel of 0.8% (marine diesel) Other vessel solid and liquid wastes will be transported to shore for disposal in accordance with the AzBU waste management plan, excluding food waste, which will be macerated and discharged overboard. Overall the total volumes of vessel emissions and discharges during pipeline installation and commissioning activities are relatively small and will occur over a short time period. Once released in the open offshore environment they will be rapidly dispersed and diluted to ACG Phase 3 ESIA Chapter 9 9/57

4 ambient levels. Environmental impacts associated with discharges to sea during offshore vessel activities are therefore considered to be insignificant Benthic Disturbance As with the installation of the offshore platforms and other subsea facilities (Section 9.3.1), the installation of the pipelines will also result in some disturbance to the seabed during installation and the presence of the pipelines will result in a permanent loss of seabed habitat. The pipe-laying operation is continuous with the lay-barge moving progressively forward as sections of pipe are welded, inspected, coated on board the lay-barge and then deployed to the seabed. The barge is held in position by up to eight anchors which also provide the mechanism by which the lay-barge moves forward along the pipeline installation route. As pipe-laying proceeds, the anchors are periodically moved by two anchor handling tugs (with one more on standby). The interval at which this occurs varies but is typically between every 500 m to 600 m of pipeline length laid. The lateral anchor spread of the pipe-lay barge is typically between 600 m to 700 m either side of the pipeline. Anchoring during pipeline installation will disturb the seabed and potentially create anchor mounds in the seabed sediments. Anchor, wire and chain drag disturbance to the seabed will be reduced by adherence to an Anchoring Management Plan that will be prepared for the installation programme. The plan will minimise the total number of anchor drops and lifts. Further, during installation the anchors will be positioned using positioning survey equipment so that correct position is achieved at first drop thereby avoiding unnecessary drops and lifts. The plan will also address the risks of damage to an existing and operating pipeline cables during lay-barge anchor handling activities. Prior to pipeline installation a pre-lay survey will be conducted using side scan sonar and ROV to assist with the planning of the installation activities, as well as to confirm seabed data including sediment type, bathymetry and topography. The survey will also ensure that the target lay area is free of any obstacles, will map all identified subsea hazards and will confirm the position and status of all existing seabed pipelines and other subsea cables. The pipeline routes will be selected to optimise line spacing and to minimise lay-barge anchor pattern interference and risk of damage to existing lines. The Phase 3 pipelines will need to cross existing pipelines on route to the connection point on the main Phase 1 / Phase 2 export pipelines. Concrete or steel crossing structures will be placed along the flanks of the existing pipelines so that sufficient spacing between the individual lines is provided. An acoustic transponder array will be installed at each crossing to provide positioning control during protection mattress and pipeline installation activities. As described in Section 9.3.1, no areas of seabed sensitivity have been identified in the Phase 3 offshore location. Furthermore, the infield pipelines will not be buried which will reduce seabed disturbance and once installed will only cover a relatively small area of the seabed. These measures, along with the careful operational management designed to minimise disturbance during the installation programme, indicates that only low residual environmental impacts to the seabed will result from these infield pipelines. The surfaces of the unburied pipelines will provide a new hard substrate for colonisation by organisms in areas where they previously would be unlikely to occur. This implies that a slight structural change in the marine faunal assemblage will result in the offshore environment through which the infield pipelines pass. The relatively short length of these pipelines would mean however, that the total new hard surface that is available for colonisation is not large and therefore, this change in faunal assemblage would not be significant Hydrotesting Once in place, each pipeline will be flooded with seawater drawn from the open sea in order to test for damage and to ensure the pipeline s integrity. This pressure testing with water is ACG Phase 3 ESIA Chapter 9 9/58

5 known as hydrotesting. The water will be treated with chemicals, which are added in order to avoid any internal corrosion of the pipe whilst the seawater is in the line. The Phase 3 30" oil export lines will be laid, flooded and tested during early 2006 and they will be dewatered by first oil in early 2008, equating to a period of two years where the lines will contain dosed water. The water will be sent to Sangachal in the Azeri 30" oil export lines. The Phase3 28" gas export line will be dewatered and dried offshore, prior to gas export. The dosed hydrotest water will also stay in the line for two years as above. The Phase 3 water injection flowlines will be laid and hydrotested during 2007 and dewatered in early 2008 soon after first oil. The water will be injected downhole into the water injection wells. The time water would be present in these flowlines is from 2 to 18 months. The chemicals to be used are the same as were used in Phase 1 and are included in Table 9.20 below, together with their dose rates. Table 9.21 Pipeline Hydrotest Water Chemicals Chemical Dose rate ppm Function Composition OCNS Category 1 D TROSKILL 88 Biocide THPS (tetrakishydroxymethylphosphonium sulphate) and 100 quaternary ammonium TROS TC Oxygen Scavenger Ammonium bisulphite E TROS SEADYE 100 Tracer Dye Fluorescein E 1 Offshore Chemical Notification Scheme. OCNS Category E is the lowest rating. Category E chemicals are of low toxicity, readily biodegradable and non-bioaccumulative. The components of the hydrotest water have the following characteristics: Oxygen scavenger: reacts with the oxygen in the water to form sulphates. The chemical can only react with oxygen once and once the reaction is complete, the residues are harmless. The main ingredient, ammonium bisulphite has a very low toxicity and is considered to pose no risk to the environment. Tracer dye: fluorescein dye that is poorly degradable but that is highly water-soluble and does not bioaccumulate. Although it is moderately persistent, it does not present any long-term environmental hazard. Biocide: readily biodegradable product that is also not bioaccumulative. Test results have shown that THPS completely hydrolyses in seven days at ph 9. Seawater typically has a ph of 8.1. The active ingredient in the biocide, THPS, will degrade in the pipeline prior to discharge, hence discharge concentrations will be significantly lower than the dosage concentration. This is supported by evidence published by Baker Petrolite (January 2000), which indicated that only 12% of the original concentration of THPS remained in the pipeline after 80 days. The oxygen scavenger and biocide chemicals hydrolyse and degrade almost entirely within in the pipeline, with a proportion being adsorbed on the pipeline surfaces. Used hydrotest water contains very little active oxygen scavenger and biocide. On completion of hydrotesting the pipelines will be tied into the connector wyes and platform and subsequently dewatered. The oil pipelines will be dewatered by launching a pig from the platform driven by the Phase 3 produced oil. The water will be pushed along the pipeline and on into the Phase 1 and 2 pipelines via the connector wyes, where it will continue on to the onshore terminal, and routed with the produced water for disposal. The infield gas pipeline will also be dewatered by launching a pig from the platform. The pig will be driven by produced gas and a glycol slug will follow the pig in front of the flowing gas. Unlike the oil pipeline, hydrotest water from the gas pipeline will be discharged to sea via a 4 valve at the connector wye on the 28 gas export pipeline. The gas will continue to flow into the Phase 1 and 2 gas pipelines and onto the onshore terminal. The total volume of hydrotest water to be discharged will be approximately 1000 m ACG Phase 3 ESIA Chapter 9 9/59

6 The discharged hydrotest water will contain residues of oxygen scavenger and biocide, and tracer die. Upon discharge the chemicals will disperse, not persisting in the environment in any potential harmful form. The chemicals to be used for dosing the hydrotest water were carefully selected using a Chemical Selection Management System to ensure that the chemicals selected on the basis of lowest toxicity, using the OCNS. The chemical components were also subjected to Caspian specific toxicity tests, as follows: The hydrolysis, adsorption or degradation of the individual chemicals were tested over 24 hours; The hydrolysis, adsorption or degradation of mixtures of the selected chemicals in seawater, at the actual doses to be used, were tested over 24 hours. The results of the tests are presented below in Tables Table 9.22 Hydrotest Water Single Chemical Tests (EC/LC 50, mg.l -1 ) Type Name Zooplankton Phytoplankton Standard WAF 11 Standard WAF 1 Dye TROS Seadye Fluoroscein >5,600 1, ,007.3 Oxygen scavenger TROS Oxygen Scavenger > Biocide TROSKIL 88 Biocide THPS Approx Table 9.23 Hydrotest Package, Zooplankton Toxicity Tests (LC 50, mg.l -1 ) Name Dose 2 Standard WAF LC50 (%) 3 Equivalent LC50 (%) Equivalent TROS Oxygen Scavenger TROSKIL 88 Biocide THPS TROS Seadye Table 9.24 Hydrotest Package, Phytoplankton Toxicity Tests (EC 50, mg.l -1 ) Name Dose 2 Standard WAF EC50 (%) Equivalent EC50 (%) Equivalent TROS Oxygen Scavenger TROSKIL 88 Biocide THPS TROS Seadye WAF refers to test preparations where the chemical or mixture was added to the sea water and allowed to equilibrate for 24 hours before the commencement of the toxicity tests. 2 Dose refers to the manufacturer s recommended concentration in the hydrotest package. The tests were carried out on a series of percentage dilutions of this package. The equivalent concentration of biocide is estimated from the dose and the 50% effects concentration. 3 Toxicity value as a concentration of the entire fluid in seawater expressed as a percentage. The single chemical test results show very low toxicity to both zooplankton and phytoplankton from the tracer dye and the oxygen scavenger. Phytoplankton were more sensitive than the zooplankton to the biocide: phytoplankton gave results with EC 50 values ranging between 1 and 2.1 mg.l -1 and zooplankton LC 50 values of approximately 13 mg.l -1. The tests on the whole hydrotest package (chemicals in seawater at the specified dosage) also indicated that the phytoplankton were the more sensitive: tests on standard and WAF preparations, under fresh and aged conditions, produced very consistent results, with the EC 50 values for all four variants in the range of about 3.4% to 4.8%; that is, the percentage concentration of the whole package in seawater. The above evidence confirms that no significant impact on the receiving environment will result from the discharge of the hydrotest water package tracer dye or oxygen scavenger. While phytoplankton show a higher sensitivity to the biocide, they live in the upper thermal layers of the sea whereas the hydrotest water will be released in deep water, thus avoiding contact with phytoplantkon. These factors along with the low biocide dosage rates in the hydrotest waters and the relatively small volume to be discharged from only one of the infield lines indicates that any residual impacts associated with this discharge would be low ACG Phase 3 ESIA Chapter 9 9/60

7 Pigging Wastes During operation, the Phase 3 oil pipelines will be pigged on a regular basis to remove waxes (and sands) accumulating on the internal surfaces. Pigging will be based on experience from the Chirag platform. Each line will be pigged every 3 days. That equates to 122 times per year for each pipeline. It is calculated that the ACG lines will produce 1 te of wax and sand each, or around 250 te per year. Pigging will be from offshore to onshore via the export lines and the wax, sand and any other materials received at the terminal will be handled in accordance with the AzBU Waste Management Strategy and Azeri Project Waste Management Plan. The AzBU waste management programme is further discussed in Section ACG Phase 3 ESIA Chapter 9 9/61

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