PetroChina Pipeline R&D Center has developed an environmental impact assessment model called the 3F Model for oil and gas pipelines. The name is an abbreviation for Flood-Flow-Forecast (3F). The Flow sub-model, as a part of 3F Model, is used to identify the oil leak paths and evaluate their impact on rivers or seas. The Flow sub-model is based on DEM, and some factors, such as soil absorption and evaporation, are also considered.
This article discusses work with the Flow sub-model that found the potential oil leak path spilling into the Gulf of Bohai Sea and identified the pipeline segments which are environmentally sensitive to the gulf. Finally, we put forward some emergency measures and suggest the oil fence location.
The Oil Loading Pipeline is located in the suburbs of Qinhuangdao City and ends on Qinhuangdao Wharf, near the Gulf of Bohai Sea. The pipeline route is nearly north-south in orientation. The total length about 17.3 km and the design pressure is 6.4 MPa, while the operating pressure is about 1 MPa. Figure 1 shows the pipeline geography. The red line represents the pipeline.
The topographic change is large, and the elevation range is from 1.2m to 58m along the pipeline. There are three valve stations along the pipeline: Qinhuangdao valve station, booster valve station and the control valve station.
The pipeline is near the Gulf of Bohai Sea, so the environmental sensitivity of the pipeline to the gulf is always focused by Qinhuangdao Pipeline Company. In this paper, we use 3F Model, developed by PetroChina R&D Center, to evaluate the environmental impact of the Oil Loading Pipeline in Qinhuangdao Wharf on the Gulf of Bohai Sea.
Environmental Impact Assessment
According to the topography of the region, we chose four simulation leak points which are located at marker K002+80m, marker K002-JM-11, marker K003-JM-11 and marker K004-BZ-05. Figure 2 shows the spatial location of the simulation leak points.
Figure 2: The spatial location of the simulation leak points.
To begin simulating the oil leak, we set the simulation scene. Table 1 indicates the parameters of the oil spill simulation scenario.
Table 1: The parameters of the oil spill simulation scenario.
According to equations, the total leak volumes of the four simulation leak points are calculated. There are respectively: 2,172 m3, 2,171 m3, 2,182 m3, and 2,188 m3. The equation, from PIRAMIDTM Technical Reference Manual, C-FER Technologies, June 2005, is:
Using the Flow sub-model, we simulated the oil leak. Figure 3 indicates a flowchart of Environmental Impact Assessment of the leak in the Oil Loading Pipeline on the Gulf of Bohai Sea.
Figure 3: A flowchart of Environmental Impact Assessment.
From the simulation results, if the pipeline at simulation leak location 3# is the failure site, the oil will spill into nearby ditch and then into the Xinkai River. The Xinkai River is connected with the Bohai Sea. In Figure 4, the red line represents the pipeline, the deep yellow cells indicate the simulation leak area at each simulation leak location and the yellow line represents the potential spill path into the Gulf of Bohai Sea.
Figure 4: The simulation results based on PetroChina Pipeline R&D Center 3F Model.
The potential leak path consists of three phases. Firstly, oil will reach a creek due to nearby topography. Second, oil will spill along the creek. Third, oil will flow into Xinkai River and finally the Gulf of Bohai Sea.
Spill Contingency Planning
The spill time into the gulf consists of three components: the time T1 of reaching the creek ; the time T2 of spilling along the creek; and the time T3 of spilling along Xinkai River and into the gulf. It is obvious that the total time of spilling into the gulf is the sum of T1, T2 and T3. Through field surveys, the flow rate of the creek is determined to be about 0.2 m/s, and the flow rate of Xinkai River is about 3 m/s. The creek length is 2,945 m and the length of Xinkai River is 4,500 m. In the simulation scenario, the time of reaching the creek is assumed to be 30 minutes. So, in the simulation scenario, the total time of the spill reaching the gulf is about five hours.
According to the potential leak path and the time of spilling into the gulf, we suggest deploying oil fence at the intersection of the creek and Xinkai River. Figure 5 shows the proposed oil fence location.
Figure 5: The proposed oil fence location.
According to the 3F Model, we have found the potential oil leak path spilling into the Gulf of Bohai Sea and identified the pipeline segments which are environmentally sensitive to the gulf. Based on the assessment results, we have drawn some conclusions as follows:
(1) Based on the overall assessment results, the environmental sensitivity of the Oil Loading Pipeline to the Gulf of Bohai Sea is low-level.
(2) According to the simulation results of the 3F Model, pollution of the Gulf of Bohai Sea is more likely if the pipeline leaks at 3# location. And we identified the potential oil spill path into the gulf.
(3) In the past, pipeline operators often paid more attention to locations where the pipeline crossed a river. And some pipeline segments, with potential for influencing the river or sea, have been ignored. By using this analysis, we found the potential threatening pipeline segments located between K003-JM-11 and K004.
(4) Arrange inspection as soon as possible and repair the defects located between K003-JM-11 and K004 in time to avoid leaks.
(5) It is recommended that planners in the future consider the potential leak paths in the contingency plans of the pipeline company and identify the oil fence locations.
Shaohui Jia is an engineer at the PetroChina Pipeline R&D Center with a master’s degree in petroleum engineering and GIS. His research includes work on GIS databases, HCA applications and risk assessments. He also has four years of experience in the oil and gas pipeline industry. He is studying for a doctoral degree at China University of Geosciences, Beijing. Ph: 86-316-2175140, e-mail: email@example.com.
Anon., The Rio Declaration on Environment and Development (1992), The United Nations Conference on Environment and Development, 1992.
PIRAMIDTM Technical Reference Manual, C-FER Technologies, June 2005.