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.