Impact of Green House Gases (GHG) Emissions from Oil Production Facilities at Northern Kuwait Oilfields: Simulated Results

Air pollution and its effects on the ecosystem has been a source of concern for many environmental pollution organizations in the world. In particular climatologists who are not directly involved in petroleum industry sometimes express concerns about the environmental impacts of gaseous emissions from flaring at various despised points. For environmental and resource conservation reasons, flaring should always be minimized as much as practicable and be consistent with safety considerations. However, any level of flaring has a local environmental impact, as well as producing emissions which have the potential to contribute to the global warming. In this study the Industrial Source Complex (ISCST3) Dispersion Model is used to calculate the ground level concentrations of two selected primary pollutants (i.e. methane and non-methane hydrocarbons) emitted from flaring activities at oil production facilities at North Kuwait. Model validation is based on the comparison of the 50 highest daily measured values and their respective predicted concentrations of methane and non-methane hydrocarbons. At discrete receptors, it is noticed that the predicted values are in good agreement with the observed data (accuracy range of 60-90%) from the monitoring stations maintained by the Kuwait Environmental Public Authority (EPA). The predicted results are based on emission inventories. Therefore, accurate emission inventory strategy for Kuwait Oil Company (KOC) as means of monitoring and minimizing the impact of methane and non-methane hydrocarbons emissions is of prime importance.


INTRODUCTION
Kuwait is a major oil exporting country and its economy, growth and prosperity is heavily dependent on oil production. KOC is at the heart of the petroleum production in Kuwait. The oilfields involve various types of industrial operations and activities, such as drilling, production of crude oil, fuel combustion, and flaring of gases which all result in gas emission into atmosphere. In practice, all other sources of emissions are small compared with emissions from flaring. Consequently, a wide range of air pollutant emissions is generated on various sites on oil fields. Such emissions include carbon dioxide, nitrogen and sulfur oxide gases, methane and non-methane hydrocarbons and Suspended Particulates Matter (SPM).
A comprehensive emission inventories from Kuwait Oilfields has been published [1] , which provides a comprehensive account and estimates of all emissions of primary pollutants associated from flaring activities in the Kuwait Oilfields. This inventory records the annual emissions of air pollutants: NO X , SO 2 , CO, CO 2 , methane and non-methane hydrocarbons. The emissions are generated from various point sources and aggregated to obtain total pollutants load of ambient air in and around oil fields. The emissions of pollutants from the flaring associated with all types of operations in the oilfields, Gathering Centers (GC), booster stations (BS), tank areas and other oil production related emission activities.
In this work the data are used as the necessary input for the ISCST3 model. Obviously methane and non-methane hydrocarbons are not the only pollutants gasses, which result from flaring activities, but their high concentrations in ambient air is a matter of grave concern. Methane and non-methane hydrocarbons are GHG with a large impact factor. Therefore, ground level concentrations have been evaluated using the latest US EPA approved dispersion model (ISCST3).

EPA MONITORING STATIONS IN THE STATE OF KUWAIT
Kuwait EPA has established a number of fixed monitoring stations to collect air quality data in the urban areas. These stations continuously measure the concentration levels of pollutants such as SO 2 , NO 2 , CO, NO, CO 2 , H 2 S, O 3 , and TSP (total suspended particles) in the air. The hourly air pollutants concentrations are recorded continuously by fixed ambient air stations located over the State of Kuwait.
It is important to note that, in general, all of the monitoring stations are considered as urban stations distributed within the residential areas except for Um Al-Aish station, which is located in the northern part of the country far away from the residential areas. Figure 1, shows the area map and the locations of Kuwait-EPA air quality monitoring sites. These monitoring stations are equipped with the latest instruments and analyzer for above mention pollutants with meteorological sensors.
In order to assess the air quality in Kuwait, the recorded concentrations of pollutants are analyzed from the Kuwait-EPA air quality-monitoring network. Kuwait-EPA has specified the concentration of non-methane hydrocarbons for early morning 3 h 6:00-9:00 AM not exceeding 0.24 ppm. The major sources of methane and non-methane hydrocarbons are oil activities as oil production, transport, refineries, storage and utilizations (traffic).

KUWAIT METEOROLOGICAL DATA ANALYSIS
Kuwait has an area of about 17,818 km 2 . At its most distant points, is about 200 km north to south and 170 km east to west. Kuwait is shaped roughly like a triangle, surrounded by land on its northern, western and southern sides and sea on its eastern side, with 195 kilometers of coastlines. The bulk of the Kuwaiti populations live in the coastal area of Kuwait. Smaller populations inhabit the nearby city of Al-Jahrah. Kuwait's land is mostly flat and arid with little or no ground water.
Kuwait has a typical desert climate, hot and dry most of the time. Rainfall varies from seventy five to 150 millimeters a year across the country, however, rainfall ranging from twenty-five millimeters a year to as much as 325 millimeters have also been recorded.
In summer, average daily temperatures range from 42°C to 46°C, the highest recorded temperature has been 51.5°C. The summers are relentlessly long, punctuated mainly by dramatic dust storms in June and July when northwesterly winds cover the cities in sand. In late summer, there is slight increase in humidity that ditches the temperature by a few degrees. Winters (November through February) are cool with some precipitation and average temperatures around 13°C (56°F) with extremes from -2°C to 27°C. The spring season (March) is warm and pleasant with occasional thunderstorms. Surface coastal water temperatures range from 15°C (59°F) in February to 35°C (95°F) in August. The winter months are often pleasant, featuring some of the region's coolest weather, with daytime temperatures hovering around 18°C (64°F) and nights being genuinely chilly. Sandstorms occur throughout the year but are particularly common in spring.
The meteorological conditions govern the dispersion of the pollutions. Therefore, the real existing meteorological conditions were recorded and used in ISCST3 model.
To work out the computation using the ISCST3 model a pre-processing program based on the U.S. EPA. PCRAMMET is utilized to convert meteorological data into right format to facilitate the computation of ground level concentration of the respective pollutants.
One year hourly record of the surface and upper air meteorological data for year 2006 obtained from the Kuwait International Airport (KIA) weather station and are used in the present study for simulation of the dispersion of methane and non-methane hydrocarbons emitted from flaring in North Kuwait Oilfields.  The most important meteorological factors that strongly affect continuously the behavior of the pollutants trends during a day are the mixing height and depth of the mixing layer. The estimation of mixing heights from upper air meteorological data is a critical parameter for understanding the formation, dispersion and transfer of ozone and precursors during pollution episodes [2] [3] [4] . The upper air meteorological data are obtained from routine measurements at the KIA weather station for the year 2006. These data were used to calculate the mixing heights Fig. 2. and to investigate the effects of upper air meteorological data in the diurnal behaviors of ozone and its precursors. The morning and afternoon mixing height estimates are determined based on the method described by Holzworth [5] and Hanna [6] .
The prevailing wind in Kuwait is along the north westerly quadrant most of the year. Figure 3a  These mean monthly meteorological data were computed from the hourly records during each day of 2006. The annual mean wind speed in 2006 is low being only 4.04 m/s, while MMWS reaches its highest in June (5.23 m sec 1 ) and in July (6.07 m/s), and its lowest in January (3.18 m sec 1 ). The annual mean temperature was 27°C where the lowest MMAT recorded during the year was 11.6°C in December and the highest MMAT was 40°C in July.
This variation of temperature and wind speeds has serious consequences on dispersion the level of air

MATHEMATICAL MODEL
Industrial Source Complex (ISCST3) dispersion model modified by the US EPA [3] [4] in 1999 is used in the present study. The ISCST3 algorithm is based on a Gaussian plume dispersion model (i.e. it solves the steady-state Gaussian plume equation) and calculates short-term pollutant concentrations from multiple point sources at a specified receptor grid on a level or gently sloping terrain. The ISCST3 model includes a wide range of options for modeling air quality impacts of pollution sources, making it a popular choice for the modeling community in a variety of applications.
The ISCST3 model implementation requires three main inputs data as follows; Source Information: The source parameters required for the ISCST3 numerical model are pollutant emission rate g sec 1 , location coordinates (UTM), source height (m), exit inner diameter (m), exit gas speed (m/s), and exit gas temperature (°C). The required information on all the location coordinates, the respective emission rates and stacks characteristic (height, diameters), flue gas velocity and temperature at the discharge have been obtain from all flaring activities from NK oil field [1] .
Receptor Information: The ISCST3 model have considerable flexibility in the specification of receptor locations, has the capability of specifying multiple receptor networks in a single run, and may also mix Cartesian grid receptor networks and polar grid receptor networks in the same run.
Two different kinds of Cartesian coordinate receptors were used as an input to the ISCST3 model, these are; • The course mesh covers approximately 40 km by 40 km with 441 receptors superimposed with two finer meshes of 26km by 18km and 21km by 14km to facilitate accurate interpolated results. The grid base elements are a square with side length of 1 kmx1km. Figure 5 describes the grid for the area under study.
• Discrete Receptors points corresponding to the location of the major population centers and the existing monitoring stations in the State of Kuwait. This means that concentrations in each point in the grid, which is 1km apart, are estimated in addition to the discrete point of the population centers and existing monitoring stations. The matrix of concentrations is plotted as a contour map for the selected meteorological data file.
These receptors are selected based on actual sites in UTM location coordinate of Kuwait map as shown in Fig. 5.

Meteorological Information:
The meteorological data required are anemometer height (m) wind speed (m/s), wind direction (degree) clockwise from the north, air temperature, total and opaque cloud cover (%), stability class at the hour of measurement (dimensionless) and mixing height (m). The anemometer height about 10 m, wind speed, wind direction, air temperature and cloud cover have been obtained from direct measurements from KIA.
The hourly stability class mixing height is estimated using PCRAMMET that is a meteorological pre-processor for preparing National Weather Service (NWS) data for use in the ISCST3 US-EPA. The routine measurements of the surface and upper air is used to run the PCRAMMET to generate an hourly ASCII input meteorological file containing the meteorological information parameters needed for the running of the ISCST3 model. The stability class was defined on the basis of Pasquill categories, which are mainly a function of the hour of measurement, wind speed and sky cover (i.e., the amount of clouds). Based on temperature profile measurements, the mixing height was estimated by the model.

STUDY AREA
The study area covers North Kuwait oil producing zones. Figure 6, shows the Kuwait map with the location of the NK oil producing area.
The ground level concentrations of methane and non-methane hydrocarbons were calculated in and around NK Oilfields consist of Ratqa, Raudatin and Sabiriyah that had 3 GCs and one BS.

RESULTS AND DISCUSSIONS
ISCST3 model was used to simulate the ground level concentrations of methane and non-methane hydrocarbons emitted from NK compute flaring activities in KOC at all points covered by the receptors information. ISCST3 model was then executed by summing the steady state concentration contributions from each source at each receptor point in the study area. The calculations were done based on the model input parameters as described in the previous sections. The simulated results of the emission scenarios using the ISCST3 are on an hourly mean predicted ground level concentrations of methane and non-methane hydrocarbons.
The hourly, daily and annual average maximum ground level concentrations of methane and nonmethane hydrocarbons were predicted and output results were compared with Kuwait Ambient Air Quality Standards (KAAQS) at all of the grid point receptors under the study area (443 receptors) as shown in Fig. 5. Allowable levels of pollutants specified by KAAQS are shown in Table 2. The computed ground level concentrations were compared with KAAQS to determine ambient air quality.
Effect of meteorological conditions: In general, clear sky, high temperature and airborne dust is the feature of the summer season whereas mid to relatively cold with light rain is feature of the winter season. These two contrasting weather conditions would have opposite effects on the dispersion of the pollutants and the concentrations levels through the processes of transport and reaction in the atmosphere. In winter season, the presence of the cloud cover results in the reduction of the solar energy, ambient temperature and wind speed, these conditions decrease the photochemical reactions for the formation of ozone and increase the incidence of the surface based inversion that results in lower mixing height. Thus, these meteorological conditions during winter season would tend to increase the concentrations of the primary pollutants.
The modeling results for the first five highest hourly ground level concentrations of methane are resulted in winter. The top high hourly ground level concentration of methane is 32.     The background concentration of methane in the ambient air prior to computation input data were considered negligible (Zero).
The results presented in Tables 3a-c and Fig. 8a-8c reveals that predicted ground level concentrations of methane.ss As shown in Table 3a the predicted maximum hourly average ground level concentration of methane in the study areas is 7.95 ppm at 19:00 Hr on 16th January 2006 at the receptor located nearly 11 km bearing 104°N, confirming the strong influence of prevailing north west wind in cold January hours evening. Most of the highest values predicted were in winter and early morning hours.
The predicted maximum daily average ground level concentration of methane in the study areas in Table 3b is 0.66 ppm on 4th January 2006. This value is 12 times less than the maximum hourly average ground level concentration value. Inspection of Fig. 8b, this receptor is located nearly 11.8 km bearing 105°N. It is not surprising that the highest annual maximum concentration of methane also at the same spot as the maximum hourly and daily. The       Table 4a and Fig. 9a, the predicted maximum hourly average ground level concentration of non-methane hydrocarbons in the study area is 38 ppm at 19:00 Hr on 16th January 2006 at the receptor located nearly 11 km bearing 104°N, confirming similar source strength with identical meteorological conditions.
The predicted maximum daily average ground level concentration of non-methane hydrocarbons in the study area given in Table 4b is 3.14 ppm on 4th January 2006. This value is 11 times less than the maximum hourly average ground level concentration value. For the same location, Table 4c and Fig. 9c show that the highest annual maximum concentration of non-methane hydrocarbons equal 298.7 ppb, which is 11 times less than the maximum daily average ground level concentration value.
Kuwait-EPA has specified the concentration of non-methane hydrocarbons for early morning 3 Hours 6:00 -9:00 AM not exceeding 0.24 ppm. The computed 3 hours average data reveal that the predicted ground level concentration of non-methane hydrocarbons for the specified time 6:00 -9:00 AM has exceeded 190 times of the KAAQS ambient air quality standard.
The above results reflect the increase in flaring in January 2006, due to regular shut down of Condensate Recovery Unit (CRU's) in NK Oilfields and the prevailing wind direction in Kuwait. Considering Table's 3a-c, 4a-c and Fig. 8a-c, 9a-c together, it can be concluded the weather pattern in Kuwait in January 2006, especially the mean prevailing wind direction, significantly contributed to high concentrations of methane and non-methane hydrocarbons at ground level in residential areas located nearly 11 km bearing 104°N.

CONCLUSION
Methane and non-methane hydrocarbons are not the only green house gasses which result from flaring activities. The flaring of excess gas is the largest single source of atmospheric emissions arising from KOC operations. However, flaring produces carbon dioxide , oxides of sulphur and nitrogen (NOx) and other chemical species that are produced due to incomplete combustion, such as carbon monoxide, aldehydes, ketones and other organic compounds known as VOCs (Volatile Organic Compounds). However the methane and non-methane hydrocarbons gases provide typical samples which are focus of this work and their emissions from flaring activities in NK oilfields are used as an input for the ISCST3 model to investigate of the impact on the air quality and GHG levels. The statistical comparison between the 50 highest daily measured and predicted concentrations at Kuwait existing air quality monitoring site showed a good agreement validating the model results.
The simulated results from the latest dispersion model in and around the NK Oilfields for the year 2006, by implementing all the major sources, from oil production facilities indicate the following; • Predicted methane ground level concentrations have exceeded 2ppm level over about 40% of the total study area (40kmx40km). • The highest average ground level concentration of methane hourly, daily and annually were in the months of January and September due to high emission rates resulted malfunctioning of condensate recovery unit. The prevailing meteorological conditions in the month of January have resulted into the top highest ground concentrations due to low temperatures and low inversion layer and calm wind conditions. • The emission rate in September is the same as that of January but meteorological conditions influence resulted into only 11 hourly values from the top 50 values and 8 daily values. • There is a need for an accurate emission inventory for KOC to minimize the impact of methane and non-methane hydrocarbons released from flaring activities over the urban area of Kuwait. • For non-methane hydrocarbons, NMHC ground level concentrations, the emission rates are calculated in the similar way as for methane but the daily variation of methane composition in flared gas has contributed in different emissions.
• The predicted NMHC ground level concentration have violated Kuwait EPA standards over 190 times in year 2006 while in general all most all the air quality monitoring stations indicated high violation of this pollutant due to additional sources, oil storage, petroleum refining, petrochemical industries, oil transport and power generation and road traffic etc. • Predicted NMHC ground level concentrations have exceeded 0.25 ppm level over about 90% of the total study area (40kmx40km), the selection of 0.24 ppm is due to Kuwait EPA standard in early morning 3 hours 6:00 AM to 9:00 AM. • The highest mean ground level concentration of NMHC hourly, daily and annually were in the months of January and September due to high emission rates as explained in preceding section. The prevailing meteorological conditions in the month of January have resulted into the top highest ground concentrations due to low temperatures and low inversion layer and calm wind conditions. The emission rate in September is similar to January and has identical influence as methane 11 hourly high values in September out of total 50 and 8 daily values from top 50 values.
Overall it seems that the levels of pollutants in winter period are higher than summer. This is because the winters in Kuwait portray a low temperature, low inversion layers, lesser wind movements, which relegate the dispersion of pollutants as compared to summers, which have high temperature, high inversion layers, and high wind movements strongly influencing the dispersion of pollutants. The work is in progress to include other pollutants such as NO X , SO 2 , CO and CO 2 with detailed accurate emission inventory to minimize the impact of NO X , SO 2 , CO, CO 2, methane and nonmethane hydrocarbons emissions from flaring activities emissions.