GIS - AN Effective Support or Oil-Spill Response

GIS - AN Effective Support or Oil-Spill Response

Shripad Biniwale
L.K. Kshirsagar
P.B. Jadhav
Department Of Petroleum Engineering,
Maharashtra Institute Of Technology.
Ex Sevicemen colony, Paud Road
Pune 411038, Maharashtra, India.
E-Mail : shripadon@yahoo.com

Abstract:
This paper envisages about a model which we have developed for an offshore field along east coast of India. After pre/post-monsoon surveys, available data like physical and chemical parameters are processed using Geomedia Professional. When oil is discharged by making buffer zones, it is possible to predict the extent of spread, evaporation rate at specific time interval and it’s spreading towards the coast. Amount of oil evaporated and dispersed here is calculated using mathematical models. Maps are created using MF Works for visualizing and analyzing different zones, of resultant wind/current direction and to identify resultant speed of oil slick. Linear relation of dispersion rate with wind speed is shown in different zones. Following, above procedure we got remarkable results. Assuming 1000m3 of oil-spill; on first day for radial spread, area affected is 42741467.4m2. Amount evaporated is 12.63m3. Remaining 987.37m3 is used to create buffer zone for second day. Thus the spill would reach the shore on fifth day affecting 5.203km of shoreline area. This methodology in general may be useful to predict oil-spill movement of any coastal region. Thus due to faster response, data updating and quick analysis; GIS serves as an excellent decision supporting technique for contingency planning, risk assessment and remedial operations in case of an eventuality.

Introducion:
This universe is on the threshold – Whether to survive or diminish on account of pollution and imbalances which are created by people living on this earth. There is threat to ecology on account of all pollutions various factors used by human beings. For all of the benefits oil has brought to modern society, risk is inherent in taking it from the Earth - in drilling wells, storing fuel for future use and transporting it from place to place. Protecting the environment while producing, transporting, refining and marketing fuel is a challenge the petroleum industry must meet every day.

We have an obligation to protect nature from accidental oil spills from our operations that can damage an ecosystem. The petroleum industry is working closely with government agencies, universities and research centers to reduce the frequency and impact of oil spills.

Oil spills can cause serious threats in marine environments as well as result in significant environmental damages in highly sensitive areas. Severity of impact of an oil spill depends on variety of factors, including characteristics of oil itself. Even large spills of refined petroleum products such as gasoline evaporate quickly and cause only short-term environmental effects. On the other hand heavy crude’s and water in oil mixtures may cause widespread and long lasting physical contamination of shorelines. But, the overall effects of this oil spills can be reduced through proper pre-spill planning.

The Problem:
Oil spills can have a serious economic impact on coastal activities and on those who exploit the resources of the sea. In most cases such damage is temporary and is caused primarily by the physical properties of oil creating nuisance and hazardous conditions. The impact on marine life is compounded by toxicity and tainting effects resulting from the chemical composition of oil, as well as by the diversity and variability of biological systems and their sensitivity to oil pollution. From the point of view of ecology coastal zones are very important. The coastal wet lands provide a critical link between the terrestrial and aquatic ecosystems and therefore become vital for marine ecosystem. It is estimated that more than 70 % of all commercially valuable fishes rely on the estuarine areas during at least a part of their lives. The vital role of coastal zones in ecosystems and its vulnerability to destruction makes its protection a necessity. Thus in case of an eventuality, oil spill can prove to be hazardous for marine life in this area and can adversely affect the nearby environment.

Conventional processes for an oil spill monitoring are tedious, inexact and time consuming. For petroleum industry Oil-spill is a big threat. A large amount of money is spent just for an oil spill cleanup. So focusing on this subject, we have developed a model for an offshore field along east coast of India due to its fragile environment and unpredictable climatic conditions. This may be the potential zone for an oil spill.

Due to the development of an off-shore and on-shore terminals, the possibilities of the various sensitive zones of human interest getting affected are not negligible. The map, in our coastal study area shows thick mangrove swamps. Reserved forest is also located to the north-east of Sursaniyanam onshore terminal. Within a distance of 10 Km. from Sursaniyanam towards west, north and south number of fish ponds and paddy fields can be located. There are major industries, archeological sites, ancient temples and places of tourist’s interest within 25 Km. of Sursaniyanam.

The Solution:
Solution to this problem is offered by a geographic information system (GIS) through providing analysis and visualization capabilities for a specific field location, a potential zone for oil spill. G.I.S is a geographic information system, a computer system designed to organize analyze and present the information with reference to geographical locations.

GIS is useful in responding to oil spills due to its ability to integrate large amount of marine, coastal and oil production / transportation data. The key to making use of the GIS is collecting and maintaining critical data, such as wind speed, wind direction, ocean current direction, density, and pH, so that it is available in case of a spill. Once spill has occurred; these pre-existing data-bases are queried, and the vector maps are analyzed to see what the major concerns are. It can also identify the sections of coastlines most sensitive to oil spills.

This paper envisages about a model, which we have developed for an offshore field along east coast of India. After pre/post-monsoon surveys, available data like physical and chemical parameters are processed using Geomedia Professional for analysis in this fragile environment, to predict the extent and location of a spread. This capability enables us to prepare for oil spills and respond more quickly, thereby minimizing the damage to the environment.

Although spill can never be predicted to happen, a help can come from GIS in planning for the clean up and predicting the oil movement. Also it can decrease the frequency and speed up the clean up process enough that it a worth while tool for the environment. Faster response times, updating of data and quick analysis and action are the features of GIS, which serves it as an excellent decision supporting technique for contingency planning, risk assessment and remedial operations in case of an eventuality. Thus GIS saves valuable time that can be used to save nature and human life.

The Methodology:

1. Area Of Study :

Location:
The Ravva oil field is located between the latitudes 16014’ N, 16026’ N and longitudes 82007’ E, 82011’ E. that is off east coast of India. It is located in shallow waters (depths ranging from 5 to 15 meters) at about 5 km. from shore off Amalapuram and the aerial extent of the prospect is about 100 sq. Km. The continental shelf off the off shore facilities location is narrow, broadens to the south and narrows to the north. The general orientation of the coast is south-west/ northeast.

Climatic Conditions:
The climate in the area is tropical. Wind and wave patterns are governed by the annually recurring monsoons and transition periods between them, dividing the year into four seasons. The two transition periods, April – May and October – November are characterized by occurrence of cyclonic storms, the latter period being more active. The south west monsoon (June – September) is characterized by strong and persistent wind and rough seas. North east monsoon (December – March) is the fair weather season with light, variable wind and generally calm seas.

Geo-coded Vector Map :( Showing Local Environment)

Information Gathering:

Collection of data for this field, after pre-monsoon and post-monsoon surveys, e.g. wind direction, current direction, wind speed, current speed, pH, Hydrocarbon, temperature, biological parameters such as BOD, DO, physical parameters like phosphates, sulphates, conductivity, turbidity and chemical parameters like salinity, alkalinity, chlorides.These are processed using Geomedia Professional.
Identification of sensitive areas like mangrove swamps, reserved forest, fish ponds, paddy fields, terrestrial and aquatic ecosystems.
Knowledge of Shoreline types, biological community types and their distribution, characteristics and processes.
Locations and characteristics of other sensitive recourses (e.g. harbors/marinas and facilities including seawater intakes. Fisheries, archeological sites etc.)
Properties of petroleum products that may be spilled;
Probable spill behavior under local conditions (e.g. wind, current, tides and sea state)

2. Oil Spill Processes :
When oil is discharged into water, it is subjected to several processes like. The most important of which in the first few days-weeks of the spill are –

Spreading
Evaporation
Dispersion
Emulsification
Sinking.

Others which have greater time scale were not considered. Like –

Photo-oxidation
Biodegradation
Sedimentation

1) Spreading :-
The spreading of an oil slick is one of the most important processes in early stage of the oil slick transformation, because of the influence of the surface area of oil slick on weathering processes such as evaporation and dissolution. In the first phase gravity and inertia forces dominate the spreading processes with gravity being the accelerating force and inertia the retarding force. As time progresses, the oil slick become thin and the inertia forces become relatively unimportant. In the second phase gravity forces dominate the spreading with viscous force being the retarding one. As the oil slick gets thinner interfacial tension becomes important. A third phase is reach in which interfacial tension and viscous forces dominate the spreading. Due to non consideration of the influence of wind and associated turbulence, the prediction of oil spreading using Fay's formula is

2) Evaporation :-
Evaporation accounts for the largest lost in oil volume during the early stages of the slick transformation. It is a function of wind speed 10m above the water surface, spill area, surface temperature and initial vapor pressure of oil among other parameters. The formulation used to calculate the rate of oil evaporated is given by equation –

3) Dispersion :-
Dispersion is generally assumed to result from wind generated breaking of waves dispersing oil in the water column. The following equation can be used to calculate the rate of natural dispersion of oil in the water column.

By making some buffer zones it is possible to predict the extent of spread at specific time interval and also the spreading of spill towards the coast. This enables calculation of the shoreline area affected. Mathematical models help to calculate the amount of oil evaporated and dispersed at specific time interval.

3. Oil Spill Trajectory :

Resultant Velocity:
A simple linear oil spill trajectory model was customized into the GIS environment. The velocity and direction of winds and currents are the parameters. An oil slick always be under influence of both parameters, hence the present drift prediction is based on these combined effects. The evaluation of the direction and magnitude of the resultant force of wind and current acting on an oil slick utilized information on the direction, and velocity (Vw) of the average monthly wind as well as the direction, and velocity (Vc) of the prevailing currents

Resultant Direction:
The oil spill will move in the direction which is the resultant of wind direction and current direction. This resultant direction can be found out by vector method as below –

An oil slick is always under the influence of velocity and direction of winds and currents; such maps are created using MF Works. Here particular zones are visualized and analyzed with respect to resultant direction and velocity values. This is useful for oil slick transportation prediction.

Different maps are created for current direction, wind direction and resultant direction in which oil will move. Also maps for ocean current speed, wind speed has been created and from that map of resultant speed is prepared. Finally by merging these two resultant maps we can create a final map of resultant direction and speed in MF Works.

Figure 2

In above map by visualizing and analyzing different zones, we can predict resultant direction and resultant speed with which oil slick can move in the specific zone. Here in last column first value indicate resultant speed and second one resultant direction of oil slick.

Figure 3

As shown above the rate of dispersion can be calculated and its linear relation with wind speed can be analyzed by visualizing different zones. By merging of maps of dispersion rate and wind speed this map had been prepared.

RESULTS
Following above mentioned methodology we got the remarkable results. Assuming 1000m3 of oil get spills, we analyze its effects over our study area and its nearby environment. We track the trajectory (path) of surface floating oil (or other substances) assuming it as a radial spread. By making some buffer zones it is possible to predict the extent of spread at specific time interval (per day) and also the spreading of spill towards the coast. Then we calculate the rate of spreading per day. For the first day for radial spread area affected is 42741467.4 m2. From evaporation equation amount evaporated is 12.63 m3. Remaining 987.37 m3 is used to create buffer zone for second day. Thus following this sequence the spill would reach the shore on fifth day as per our model. Using this geo-coded map when spill reaches the shore, total area of the affected shoreline is calculated and found to be 5.203 kilometers. The methodology used above in general may be useful to predict oil spill movement of any coastal region. Diverse kinds of analysis and predictions are possible bye using Geomedia Grid by visualizing vectors and raster images simulataneously.

<>Conclusion
The magic of GIS is visualization; which enable us to gain knowledge and understanding from data and information. This facility can assist in better characteristics of reservoir and better reservoir monitoring and management. GISbased system uses the latest spatial information technology to store data required for oil spill risk assess, response, planning, training and risk management.

Once a spill has occurred, the data bases are queried, and maps are analyzed to see what the major concerns are. With seeing maps and data over lays like this, the clean up team can quickly come up with a strategy to clean up the oil. Due to the faster response times directly related to the use of a GIS, lives, fauna and flora are all being saved. One of the main highlights of using a GIS is that it can be accessed from anywhere. This allows for the analysis of the information pertaining to the spill on site where it is needed the most. Therefore, the purpose of the GIS in this case is to gather all the stored information about an area for quick analysis and action. This is a big help that by using a GIS, we can predict the movement of an oil spill which would make the clean up job that much more easy.

Although a spill can never be predicted to happen, help can come from the GIS system in planning for the clean up and predicting how the oil will move. The use of a GIS has made a huge impact on the oil industry. The GIS helps train people and keeps them ready for a spill. People are more prepared to deal with the situation if a spill does occur. There are little chances that a large spill will occur in many such areas along with our study area, so using GIS we can suggest some precautions being taken to avoid major damage in such probable potential zones. It is better to be safe than sorry. GIS, like oil products, has become an integral part of human life. Without it, oil movement would be unpredictable and much much slower. Thus GIS serves as an excellent decision supporting technique for contingency planning, risk assessment and remedial operations in case of an eventuality. Finally it’s the GIS which save valuable time that can be used to save the nature and human life. There is a humble attempt, may be like a drop in the ocean to save this mother earth from deleterious effects of oil spills.

Bibliographical Reference

G. Fabbri & Chung C. F., 1993, “Representation of Geosciences Information for Data Integration”
Berry J. K., 1987b, “Journal of Environmental Management, Vol. 11”
Bonham-Carter and Wright D. F. & G. F., 1996, “UHMS Favorability Mapping with GIS Based Integration Models”
Bonham-Carter, G.F. 1994, “Modeling with GIS”
Jeffrey M. Yarus, Timothy C. Coburn, “GIS in Petroleum Exploration & Development”
Journals of Remote Sensing and GIS.

Acknowlegements
The authors of this paper are grateful to Prof. Dr. V. D. Karad, Director Maharashtra Institute Of Technology, Pune for providing facilities for the work. They thank Dr. O. S. Chauhan, Group Leader-Environmental Issues, National Institute Of Oceanography, Panaji, Dr. Ajay Singh from ROLTA INDIA for their valuable technical guidance and AICTE, India for financial assistance.