MANAGEMENT OF WATER TABLE RISE AT BURGAN OIL … Mohamed Senafy.pdfManagement of Water Table Rise at Burgan Oil Field, Kuwait Emirates Journal for Engineering Research, Vol. 16, No.2,

Emirates Journal for Engineering Research, 16 (2), 27-38 (2011) (Regular Paper)

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MANAGEMENT OF WATER TABLE RISE AT BURGAN OIL FIELD, KUWAIT

Mohamed Al Senafy

Water Resources Division – Kuwait Institute for Scientific Research P.O. Box 24885 – Safat 13109 - Kuwait

(Received April 2011 and Accepted November 2011) علىواسعة النطاق مكلفة وأضرار حيث تسببت ب ،مناطق العالم العديد منفي ارتفاع المياه ةهراظ تد أثرلق

إدارة حولدراسة أجريت هذه الظاهرة، فقد افرضهونظرا لآلثار السلبية المحتملة والتي قد ت. واألفراد الممتلكاتالمسح الطوبوغرافي لقياس ارتفاع مستوى وقد تم عمل. في حقل برقان 140ارتفاع مناسيب المياه حول المحطة

تم حفر وتسجيل آذلك ،داخل حقل برقان 2آم 25ين اإلحداثيات في مساحة تبلغ حوالي يوتع ،سطح األرض ،مترا 45-35آبار للمراقبة بأعماق تتراوح بين 4و ،مترا 40بعمق إنتاجية آبار 4وتصميم وترآيب وتطوير

استخدمت هذه اآلبار ألخذ عينات من التربة وألخذ وقد. مترا 120ين الدمام بعمق بئر للمراقبة في تكوإضافة إلى ،ساعة 48آما تم إجراء اختبارين للضخ واالستعادة مدة آل منهما . عينات من المياه الجوفية وتحديد مستوى المياه

من شبكات المياه العذبة جمعةالمالعينات وتم إرسال . آبار للمراقبة في آل اختبار 9وذلك باستخدام بئر للضخ و الجوفية عينة للمياه 14ومياه الصرف الصحي ومحطة اإلطفاء، وبحيرة الترفيه والمحجر المهجور إضافة إلى

إلجراء التحاليل الفيزيائية المناسبة مختبراتلل الموجودة خمسةحديثا واآلبار ال المحفورة تسعةمن اآلبار ال المجمعةومستويات المياه ،الضخ اتطوبوغرافي واختبارالمسح ال نتائج تقييم تمو .ية وتحاليل النظائروالكيميائية والبيولوج ت الدراسةوخلص. المياه الجوفيةلحرآة العناصر محددوفي نموذج ثالثي األبعاد استخدامها الجوفية ونوعيتها و

،ومع ذلك. المياه في منطقة الدراسةتسبب في ارتفاع منسوب ييمكن أن والذي لمياه لرئيسي مصدر عدم وجودإلى المياه الة عمق ضحوهي ب اسباألمن اجتماع عدديمكن أن يعزى ارتفاع المياه الجوفية في منطقة الدراسة إلى

وانخفاض منطقة األرض؛ تحت سطحتسرب المياه إلى أعلى من تكوين الدمام إلى و؛ )م 2أقل من (الجوفية مياه المياه األمطار و ربوتس ،التبخر الطبيعي واإلخالل بنظام؛ مرتفعةاطق تحيط بها منحيث الدراسة نسبيا

-BS-06, BS(ضخ آبار اإلنتاج األربعة أوصت الدراسة إلى وقد .الفائضة من حفرة التخلص من النفايات القريبة07, BS-08, and BS-09 (4.5مق إلى متوسط عجالون بالدقيقة من آل بئر لخفض مستوى المياه 40 بمعدل

مكن إعادة استخدام المياه التي سيتم ضخها ألغراض متعددة بعد معالجتها بالطرق مومن ال .140 -المحطةمتر تحت .المناسبة

The Water rise phenomenon has affected many areas in the world, resulting in a widespread and costly damage to property and people. In recognition of the potential negative impacts imposed by this phenomenon, a study on the management of water table rise around Booster Station 140 in Burgan Oil Field was conducted. A topographic survey to measure the ground surface elevation and the UTM coordinates in an area of about 25 km2 inside Burgan Oil Field was completed. A total of 4 production wells with 40-m depth, 4 monitoring wells with depths between 35 and 45 m, in addition to one Dammam Formation monitoring well with 120-m depth were drilled, logged, designed, constructed and developed. These wells were utilized for soil sampling, groundwater sampling and water level determination. Two pumping and recovery tests of 48-h duration, using one pumping well and nine observation wells in each test, were conducted. Water samples collected from freshwater, wastewater and fire station water networks, the recreation lake and the abandoned quarry along with 14 groundwater samples collected from the 9 newly drilled wells and the 5 existing wells were analyzed in the appropriate laboratories for physical, chemical, biological and isotopic analyses. Results of the topographic survey and pumping tests data, groundwater levels and quality were evaluated and utilized in a three-dimensional finite element groundwater flow model. No major source of water was that can cause the rise in water level was found. However, the rise of the groundwater in the vicinity of the study area can be attributed to the shallow depth to groundwater (less than 2 m); upward seepage from Dammam Formation water to the subsurface; location of the study area in a relatively low land surrounded by hilly areas; interruption of the natural evaporation system; and the infiltration of rainfall and water from the overflow of the nearby disposal pit. It was recommended to pump from the four production wells at a rate of 40 gpm per well to reduce the water table to an average depth of 4.5 m below BS-140. The pumped water can be re used for several purposes after proper treatment methods.

Mohamed Al Senafy

28 Emirates Journal for Engineering Research, Vol. 16, No.2, 2011

1. INTRODUCTION Rising groundwater has affected many urban areas in the Middle East from large cities to individual sites, resulting in a widespread and costly damage to property, and possible effects on public health. There is a wide range of problems associated with rising groundwater, depending upon the particular geotechnical and hydrological conditions, and the construction practices employed at site under consideration. Hamdan [1] listed some of the problems associated with groundwater rise as follows:

• Damages to structures • Damages to services and roads • Overloading of sewer systems • Salting and water logging of soil • Public health hazards

In arid coastal regions, environmental and geotechnical problems due to groundwater table rise may occur mainly as a result of precipitation of minerals like chlorides or sulphates from the groundwater rise. This precipitation arises from the upward movement of groundwater through the capillary fringe due to high levels of surface evaporation. In the past decades, high subsurface water level had been reported in some residential areas of Kuwait, and there has been a growing concern about its adverse impacts on the environment and on the integrity of foundations, underground structures, and buried utility services. The first comprehensive investigation of the problem was conducted between 1984 and 1987 at KISR (Hamdan[1]. The brackish groundwater is supplied to domestic consumers at a rate of 8 cents/m3 (Bushnak[2] for landscaping purposes in Kuwait. Excessive use of groundwater for landscaping and gardening in urban areas has resulted in the rise of groundwater levels by about 3 m, threatening the integrity of several buildings and roads (Al-Rashed et al.[3]. As a result, to combat the water rise problem a dewatering program was implemented in selected areas that resulted in the decline of groundwater levels by as much as 4 m (Senay[4] . Al-Sanad and Shaqour[5] discussed the causes and the geotechnical implications of the groundwater rise in Kuwait. They related the problem to the downward percolation from subsurface pipe networks and from the excess of irrigation together with the local geologic conditions. Al-Rashed and Sherif[6] presented a comprehensive study for urban drainage in two selected areas representing the two hydrogeological settings encountered in Kuwait City. In the first area, a vertical drainage scheme was applied successfully over an area of 1 km2. In the second area, a dual drainage scheme, composed of horizontal and vertical elements, was proposed. Horizontal elements were suggested in the areas where the deep groundwater

contained hazardous gases that would pose environmental problems. Few studies have related the rise of water table to reasons other than those previously mentioned. These include rainfall and seepage from deeper groundwater aquifers. For instance, Almedeij and Al-Ruwaih[7] investigated the periodic pattern of groundwater level fluctuations in six residential areas in Kuwait. The water level, rainfall and temperature data relationships revealed the effect of climate on the series of water level fluctuation. In Western Australia, Taniguchi et al.[8] estimated large groundwater seepage rate from deep fresh and saline groundwater to subsurface. Similarly, Mukhopadhayay et al.[9] concluded that the upward movement of water from deep layers has given rise to the present distribution of H2S in the aquifers underlying Kuwait City. Numerous studies throughout the world have documented the urban groundwater fluctuations caused by anthropogenic factors (Jacobs[10]; Khazaei et al.[11]; Foppen[12]; Lerner[13]). On the other hand, water rise problem in open areas similar to the study area was not often reported or thoroughly discussed. The rise in the shallow unconfined groundwater level at the Booster Station 140 (BS-140) in the Burgan oil field of the Kuwait Oil Company (KOC) is causing water logging of the underground facilities in the station. Currently, the depth to the water is less than 2 m from the ground surface within the perimeter of the booster station. The precipitation from the rising groundwater and the water itself may adversely affect the foundations, asements, and other utilities like electrical substations, pumping stations for sewage water, etc., in the Burgan oil field. Damages to these facilities will cause general inconvenience and may even affect human lives due to structural weaknesses. The possible occurrence of hydrogen sulfide (H2S) in the groundwater, as observed in many other residential areas of Kuwait, may further aggravate the problem. The observed problems may lead to the stoppage of the booster station operation, thereby, resulting in significant loss.

2. HYDROGEOLOGY OF KUWAIT The natural water resources of Kuwait are practically limited to groundwater resources. These resources are brackish in nature in the central and southwestern parts of the country. Groundwater becomes more saline toward the north and northeastern parts of the country following the general direction of the groundwater flow toward the Arabian Gulf. The unique geomorphology and lithology in the northern parts of Kuwait were responsible for the formation of fresh groundwater lenses that float over the main

Management of Water Table Rise at Burgan Oil Field, Kuwait

Emirates Journal for Engineering Research, Vol. 16, No.2, 2011 29

body of the saline groundwater. In Kuwait, extraction of groundwater is from two main aquifers, namely; the Kuwait Group aquifer, and the Dammam

Formation aquifer. The lithology of the two aquifers is presented in Table 1.

Table 1. Lithological Section of Aquifers in Kuwait (Source: Al-Senafy[14])

Age Group Formation Aquifer Lithology Recent

Kuwait Group

Recent - Surface deposits; beach sand, sand, gravel, silt, etc.

Pleistocene Dibdibah AQ-1 Coarse sand and gravel, calcretized at lower parts Miocene

Fars - Evaporites, fine sand and clay with fossiliferous limestone

Ghar AQ-2 Sand and gravel occasionally calcretized with clay intercalations, thicker towards the bottom

Eocene

Hasa Group

Dammam

AQ-3

Upper: chalky dolomicrite chertified at top Middle: laminated limestone and dolomicrite with lignetic seams Lower: numulitic limestone with shale at the bottom

Paleocene Rus - Anhydrite with dolomitic limestone Um Radhuma - Limestone, dolomite, anhydrite

3. STUDY AREA The study area is located in the eastern part of Burgan oil field located south of the Kuwait City (Fig.1). The Burgan oil field is the second most important oil field in the Middle East. It accounts for most of the current and historical oil production of Kuwait.

The study domain covers an area of 25 km2 within the Greater Burgan oil field with the BS-140 Booster Station located at the center. Two abandoned quarries which were previously used as landfills and are

having free water at the bottom at present are located within the study area. Geologically, the study area is above the Burgan structure, which is an anticlinal dome with numerous radial faults. There are as many as 30 of these faults, typically three to four kilometers in length. The compartmentalization of the main reservoir sands by the radial faults, combined with high production rates resulted in water incursion problems (Warsi[15]).

Figure 1. Location of the study area in Burgan oil field

Mohamed Al Senafy


Booster Station 140

Burgan oil field is the largest and the most important oil field in Kuwait. It contains hundreds of oil production wells. These wells are producing from deeper oil reservoirs at depths of about 1400 m. The upper geological formations up to about 1200 m including the two main groundwater aquifers, i.e. Kuwait Group and Dammam Formation are isolated in these wells by steel casing. The study area contains about 135 oil production wells. Five existing monitoring groundwater wells (BS01-BS05) were drilled by Kuwait Oil Company (KOC) in 2008, Fig.2. These wells are of 75-mm casing and screen diameter and of about 15-m depth. The screen interval is from 13 to 14.5 m.

4. METHODOLOGY 4.1 Topographic Survey

Prior to the drilling of the wells, the ground surface elevation and the UTM coordinates in an area of about 25 km2 inside Burgan oil field were determined. The state-of-the-art global positioning system (GPS) equipment of grid surveying was used for differential GPS observations for the 5000 x 5000

m grid with cell size of 100 m x 100 m. Two existing geodetic control points in the study area were used as a reference for the executed grid surveying. A high accuracy base station was established over the geodetic control point, and a GPS rover was installed in a four-wheel car to record the surveying data. The study area was divided into parallel lines around the BS-140, and the rover GPS was moving along these lines. Elevation measurements were recorded to an accuracy of +/- 10 mm, and the UTM coordinates were recorded at an accuracy of +/- 100 mm. The topographic survey data are shown in Fig. 3.

4.2 Construction of Groundwater Wells

A truck-mounted fully hydraulic drilling rig was used for drilling 9 groundwater wells. (Figs. 2 and 4). Drilling was carried out by the straight mud circulation rotary method. Bentonite mud mixed with freshwater was used as a drilling fluid. The final design of the installed monitoring and pumping wells is presented in Table 2.

Figure 2. Location of wells BS01-BS10 and BS14



Figure 3. Two-meter interval topographic map of the study area (m msl).

Figure 4. Location of wells BS11, BS12 and BS-13.

Booster Station 140

Mohamed Al Senafy


Table 2. Design of the Installed Pumping and Monitoring Wells in Study Area

Well No. Total Depth (m)

Casing-Screen Diameter (mm)

Screen Interval (m)

BS-06 43 200 16 - 40 BS-07 40 200 14 -37 BS-08 41 200 14 - 38 BS-09 40 200 14 - 37 BS-10 35 100 06 - 32 BS-11 42 100 12 - 39 BS-12 39 100 06 - 38 BS-13 45 100 15 - 42 BS-14 120 150 93 - 116

4.3 Soil Sampling

A total of about 400 drill cutting samples of 500 g were collected during drilling at 1-m interval in the 9 drilled wells. The samples were megascopically tested on site to design the well and further description was made in laboratory to construct the conceptual lithological model of the study area. Grain size analyses of selected drill cutting samples were carried out to help in their textural classification. Microscopic and X-ray diffraction analyses of some of the samples were done to get some idea about their mineralogy.

4.4 Water Sampling

Following the completion of the well development and measurement and recording of the water level, an electric submersible pump was used for purging the screened interval of the 9 new pumping and monitoring wells and the 5 existing monitoring wells to enable the collection of representative groundwater samples. Groundwater samples were collected according to the United States Environmental Protection Agency sampling guidelines (USEPA, [16]). In addition to the sampling of the 14 groundwater wells in the study area, water samples were also collected from the freshwater and wastewater networks, fire station, recreation lake and the abandoned quarry to provide essential contextual information.

4.5 Pumping Tests

Two pumping and recovery tests were performed. Necessary equipment with a throttling device, variable speed and continuous power source to discharge a variable rate ranging from 140 - 250 gal/ min of water from a maximum depth of 40 m below the ground were installed. Each of the two pumping tests was run for 48 h and was followed immediately by recovery test for a specified duration. A 25-mm PVC pipe was installed inside the pumping well permanently for water level measurement to a depth of 2 m above the pump intake. Groundwater samples were collected and the pumping rate was measured during the test regularly. In the first test, well No. BS-06 was considered as the pumping well and was pumped at a rate of 175 gal/min for 48 h. Eight wells, namely; BS-01, BS-02, BS-03, BS-07, BS-8, BS-09, BS-10 and BS-14 were used as observation wells during the pumping and the recovery tests. In the second test, Well No. BS-07 was used as a pumping well with a pumping rate of 140 gal/min for 48 h. Nine wells, namely; BS-01, BS-02, BS-03, BS-04, BS-05, BS-06, BS-8, and BS-09 were used as observations wells during the pumping and the recovery tests. The summary of the pumping tests data is shown in Tables 3 and 4.

Table 3. Summary of the First Pumping Test Data

Test No. Well No. Initial Depth to water (m) Final Depth to water (m)

Pumping well : BS-06 Pumping Rate= 175 g/m Duration : 48 hrs

BS-01 1.86 4.88 BS-02 3.09 3.28 BS-03 1.82 4.78 BS-06 2.99 15.9 BS-07 3.43 6.62 BS-08 2.63 5.20 BS-09 3.66 5.78 BS-10 2.30 7.44 BS-14 4.62 4.62



Table 4. Summary of the Second Pumping Test Data

Test No. Well No. Initial Depth to water (m) Final Depth to water (m)

Pumping well : BS-07 Pumping Rate= 140 g/m Duration : 48 hrs

BS-01 1.91 3.59 BS-02 3.01 3.18 BS-03 1.86 4.18 BS-04 3.75 4.08 BS-05 3.79 5.72 BS-06 2.98 5.81 BS-07 3.48 21.92 BS-08 2.66 4.81 BS-09 3.70 6.10

4.6 Analyses of Soil and Water Samples

The water samples collected from the drilled and the existing wells and the other existing facilities were analyzed for a total of 24 physical, chemical, and biological parameters including the major cations and anions, hydrogen ion activity (Ph), EC, DO, B, NO3, PO4, NH3, H2S, Fe, TDS, BOD, COD, TOC, TPH, coliform bacteria and isotopic components. Oxygen-18 and deuterium were measured using an off-axis integrated cavity output spectroscopy water isotope analyzer (Los Gatos model 908-0008). For quality control and quality assurance (QA/QC) purposes, duplicate groundwater samples were collected and analyzed to ensure the accuracy and dependability of the analysis results.

5. RESULTS 5.1 Topographic Characteristics

The study area is a gently undulating desert plain that covers an area of 25 km2 with the BS-140 Booster Station situated at the center. The topography of the study area is characterized by small hills of gentle slope separated by wide depressions. The ground surface elevation varies from the lowest height of 49 m at the northwest to a maximum height of 89 m at the northeast. The Booster Station 140 campus is located in a lowland with an elevation of about 57m

in average and surrounded by relatively high hills of about 65 m height. The main depressions in the study area usually get filled with water when heavy rain occurs, forming large ponds.

The landscape of the study area is disturbed by huge excavations and characterized by a weak surface soil. The study area contains premises of oil industry installations which are mostly covered with small trees dispersed over the area. The study area is crossed at its middle by the main Burgan road, and has many dirt roads. A large number of pipelines extend across the area in addition to quite a few scattered oil pits. A recreation lake and two abandoned quarries having free water at the bottom at present are located within the study area.

5.2 Conceptual Model for Local Lithostratigraphy

Zonation of the sediment sequence in the study area was carried out on the basis of megascopic descriptions of the drill cuttings, supported by grain size, geophysical logging and x-ray diffraction analyses. The lithostratigraphic sequence in the drilled wells in the study area is divided into two main units, the clastic deposits of the Kuwait Group, and the underlying carbonates belonging to the Dammam Formation. The conceptual model for local lithostratigraphy is presented in Table 5.

Table 5. Local Lithostratigraphic Sequence in the Study Area

Depth (m) Group Formation Lithology

00 – 14

Kuwait Group Undifferentiated

Calcretized Silty Sand14 – 22 Gravely Sand (Partially Calcretized) 22 – 25 Calcretized Silty Sand 25 – 35 Gravely Sand (Partially Calcretized) 35 – 40 Calcretized Silty Sand 40 – 49 Gravely Sand (Partially Calcretized) 49 – 51 Green Mud 51 – 53 Gravely Sand (Partially Calcretized) 53 – 65 Green Mud 65 – 91

Hasa Group Upper Dammam Formation

Chertified Dolomitic Limestone (karst zone) 91 – 107 Chalky Dolomitic Limestone 107 – 120 Dolomitic Limestone

Mohamed Al Senafy


5.3 Groundwater Flow

In attempting to distinguish the indigenous groundwater quality from the impacts of any extraneous influences, the groundwater flow direction is probably the most important hydrological information to be known.

Flow direction was determined for the study area according to the piezometric groundwater levels in relation to the mean sea level. The leveling survey results with the measured water depth at the 14 monitoring wells were used to prepare the water level contour maps (Fig. 5). The flow direction for the study area followed the same regional trend of northeast flow direction toward the sea.

Figure5. Groundwater levels above mean sea level at the BS-140 study area.

5.4 Rainfall and Water Level

The monitoring of water levels in the observation wells available within the study area also indicated the recharge of the near surface aquifer from infiltrating rainwater after heavy rainfall events, especially in the areas where topographic depressions are present.

In fact, BS-140 is located on the eastern part of one such depression within the study area and the hydrographs of some of the wells in the neighborhood of the booster station indicated a rise of 15 – 25 cm for the water table in the study area after 20 mm of rainfall.

5.5 Groundwater Quality

Statistical Description of Groundwater Chemistry

Tables 6 and 7 present the results of the chemical analyses of the collected groundwater samples from the study area. The main characteristic of the groundwater of the study area is its relatively high contents of the major cations and anions (more

specifically, sulfate, calcium, chloride, sodium, and magnesium), and as a result, its high TDS content.

The TDS, which are considered as a collective indicator of the aforementioned parameters, ranged widely from about 4800 to 16000 mg/l with an average concentration of about 12000 mg/l.

The components of the dissolved solids have the statistics as follows: sulfate concentrations ranged between 2200 and 5000 mg/l with an average concentration of 3307 mg/l; calcium ranged between 540 and 1140 mg/l with an average value of 747mg/l; chloride ranged between 790 and 5800 mg/l with a mean value of 3944 mg/l; sodium ranged between 750 and 3400 mg/l with a mean value of 2500 mg/l; and magnesium ranged between 73 and 432 mg/l with a mean value of 285. The maximum concentration for nitrate was 295 mg/l while the minimum concentration was 30.4 mg/l. The mean value for nitrate was 187.7 mg/l.

The bicarbonate concentration in the study area ranged between 70 and 315 with an average value of



70 mg/l, while carbonates were not detected. The boron concentration in the analyzed samples ranged between 2.5 and 14.9 with an average value of 6.6 mg/l. No phosphate, ammonia and hydrogen sulfide were detected in the Kuwait Group wells. Phosphate, ammonia and hydrogen sulfide concentrations of5.8 mg/l, 5.3mg/l and 18.4 mg/l, respectively, were found in the water of well BS-14 which was completed in the upper part of the Dammam Formation.

The relatively high concentration of total organic carbon (TOC) and Total coliform bacteria (TCB) that was found in the water sampled from the existing old wells (BS-01 to BS-05) could be attributed to the stagnancy of the water as a result of sampling by bailing which was the only method to collect samples from these wells. Moreover, the lower salinity of the groundwater in these wells is most probably, due to the mixing of rain water.

The salinity of the groundwater from the Dammam Formation well (BS-14) was 13041 mg/l matching the salinity of Kuwaiti Group aquifer. The water quality of Kuwait Group and the Dammam Formation was found to be of similar species except for Dammam which was found to have higher concentrations in calcium, magnesium, and chloride and lower concentrations in nitrate and sulfate. Moreover, the Piper and the Durov interpretation methods showed that the pumped groundwater type in both Kuwait Group and Dammam Formation aquifers in the study area was NaCl, while the bailed water from the Kuwait Group was of NaSO4 type, confirming the upward seepage of the Dammam water.

Groundwater Quality and Rainfall

Another round of groundwater sampling was carried out during April toward the end of the rainy season. Groundwater samples were collected using bailers to delineate the chemistry of the upper portion of the aquifer in order to verify the recharge of rainfall to groundwater recharge. At the same time, samples were also collected by pumping to get representative groundwater samples from the aquifer. The salinity of the samples collected by bailing and pumping were compared to assess the effect of rain on the groundwater quality.

Bailed groundwater samples showed lower salinity than those of the pumped samples. The difference in the salinity of the groundwater samples by bailing and pumping from the same well showed that there was a recharge from rainfall, especially in the areas of topographic depressions which in turn contributed to the rise in water level in these areas. The total salinity of the uppermost aquifer was reduced by 30% due to the rainfall recharge which in turn contributed to the water table rise.

5.6 Quality of Other Sources of Water

The free groundwater moving in the abandoned quarry was found to be highly saline, which can be attributed to the high rate of evaporation. The free flowing groundwater in the recreation lake is also saline, but with less salinity than the water in the quarry due to addition of fresh and brackish water to maintain a certain level in lake.

Table 6. Results of Chemical Analysis of Groundwater from 5 Existing Wells.

Parameters Well NumberBS-01 BS-02 BS-03 BS-04 BS-05

pH 7.66 7.07 8.22 7.90 8.10 EC (µs/cm) 10310 14540 5930 16080 20500TDS (mg/l) 7653 10734 4824 11989 16068Alkalinity (mg/l) 150 315 70 115 85Bicarbonate (mg/l) 150 315 70 115 85Carbonate (mg/l) <0.1 <0.1 <0.1 <0.1 <0.1Hardness (mg/l) 3100 4100 1900 3400 3000Calcium (mg/l) 920 1072 540 800 560Magnesium (mg/l) 195 347 73 342 391Sodium (mg/l) 1330 2000 750 2600 3400Potassium (mg/l) 80 74 56 106 120Chloride (mg/l) 2360 3960 790 3990 4350Nitrate (mg/L) 88.4 30.4 80.1 264 294.8Ammonia (mg/l) <0.1 <0.1 <0.1 <0.1 <0.1Boron (mg/l) 2.5 4.4 2.7 7.6 14.9Iron (mg/L) 0.011 0.149 0.005 0.002 0.002Phosphate (mg/l) <0.1 <0.1 <0.1 <0.1 <0.1Sulfide (mg/l) <0.1 <0.1 <0.1 <0.1 <0.1Sulphate (mg/l) 2500 2900 2300 3600 5000COD (mg/l) 45 98 63 34 13TOC (mg/l) 5.978 27.213 6.655 3.735 1.839TPH (mg/l) 0.761 1.568 0.921 0.356 0.245BOD (mg/l) <1.0 <1.0 <1.0 <1.0 <1.0Coliform MPN/100 47.3 <1.0 <1.0 68.4 55.5

Mohamed Al Senafy


Table 7. Results of Chemical Analysis of Groundwater from Newly Drilled Wells.

Parameters Well NumberBS BS BS BS BS- BS BS BS BS

pH 7.6 7.8 7.9 7.7 8.1 7.8 7.7 7.8 7.1EC (µs/cm) 18 18 18 18 179 14 15 17 18TDS (mg/l) 13 13 13 13 131 10 11 12 13 Alkalinity (mg/l) 12 11 11 10 107 85 10 11 15Bicarbonate (mg/l) 12 11 11 10 107 85 10 11 15Carbonate (mg/l) < < < < < < < < < Hardness (mg/l) 31 29 28 29 290 27 26 25 46Calcium (mg/l) 72 73 72 72 680 64 64 56 11Magnesium (mg/l) 33 27 25 26 293 26 24 26 43Sodium (mg/l) 31 29 31 31 284 23 24 27 23Potassium (mg/l) 64 76 72 82 82 68 60 84 88 Chloride (mg/l) 49 45 44 48 440 32 37 38 58Nitrate (mg/l) 18 25 24 26 233 21 19 19 70.Ammonia (mg/l) < < < < < < < < 5.3 Boron (mg/l) 6.5 8.2 6.9 11. 3.9 4.2 5 12 2.7Iron (mg/l) < < < 0.0 0.0 < < < 0.1Phosphate (mg/l) < < < < < < < < 5.8 Sulfide (mg/l) < < < < < < < < 18.Sulphate (mg/l) 35 35 36 35 350 35 32 35 22COD (mg/l) 0.0 12. 13. 13. 0.0 14 20. 21. 13.TOC (mg/l) 0.7 0.7 0.5 0.6 0.7 1.0 0.8 1.2 0.5TPH (mg/l) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.1BOD (mg/l) < < < < < < < < < Coliform MPN/100 < < < < < < < < <

The samples from the fire service water network was found to be of brackish type. Water samples from freshwater network and wastewater network were found to be fresh with TDS less than 500 mg/l. None of these water sources is possibly affecting (recharging) the groundwater in the study area as the quality of none of these water sources matched that of the local groundwater. This is also supported by the isotope composition of groundwater that markedly differs from the stable isotopic fingerprints of these source waters. It was therefore, concluded that there is no recharge from these sources to the groundwater within the study area.

5.7 Isotopic Analysis

The environmental isotopes (oxygen-18 (18O) and deuterium (2H) ) were utilized in the current study to characterize the groundwater system in the neighborhood of the Booster Station-140, to determine its age and to estimate the time and sources of recharge water to the system. The results of the analyses, carried out at the International Atomic Energy Agency (IAEA) laboratory are presented in Table 8. Table 9 presents the analyses of stable isotopes 18O and 2H carried out in the hydrology laboratory in KISR.

Table 9. Results of Stables Isotope Analysis at Hydrology Laboratory in KISR

Sample No. Deuterium (‰) Oxygen-18 (‰)

BS-01 -11.63 -1.33 BS-02 -7.16 -0.17 BS-03 1.96 0.20 BS-04 -5.69 0.29 BS-05 4.24 2.56 BS-06 -13.00 -0.42 BS-07 -9.81 0.04 BS-08 -10.96 0.02 BS-09 -9.86 0.11 BS-10 -7.98 0.37 BS-11 -9.02 -0.17 BS-12 -13.61 -0.69 BS-13 -8.53 -0.08 BS-14 -20.63 -1.49 FS1 -6.85 1.76 WW1 -12.93 -4.29 QU1 13.83 4.39 FR1 -10.62 -1.49 RL1 25.98 6.84

1 FS – Fire Service Network; WW – Wastewater Network; QU – Abandoned Quarry; FR – Freshwater Network; RL – Recreational Lake



Combining the implications from 14C and tritium results, it can be concluded that the sampled groundwater at the study area had experienced limited recharge from recent rainfall events. The isotope data also demonstrated clear difference in the ages of the water from the Dammam Formation from that in the Kuwait Group, the former being older. Furthermore, the depleted oxygen 18 and deuterium contents in the water of the Dammam Formation compared to that in the Kuwait Group differentiated clearly the two.

5.8 Modeling

Utilizing geologic input from the field investigations and the available hydrogeologic data, a three-dimensional, finite element groundwater flow model that simulates the ground-water flow system in the area surrounding and within BS-140 was developed and calibrated. The model was then used to predict the dewatering requirements for managing the water table rise around BS-140 and the potential drawdown in the water table induced by this dewatering. The two pumping tests done during the study provided a data for the calibration and verification of the model. The calibration of the BS-140 model to the available data was considered quite reasonable.

6. DISCUSSIONS The monitoring of water level in the observation wells available within the study area has indicated the recharge of the near surface aquifer from infiltrating rainwater after heavy rain falls, especially in the areas where topographic depressions are present. A rise of 15 – 25 cm for the water table in the study area was observed after a 20 mm of rainfall. Water level measurements made at well BS-02 were not consistent with those from other wells screened in the same interval due to the overflow of the nearby wastewater discharge pit. The lowering of evapotranspiration from the water table because of the construction of the BS-140 facilities in low land is an indirect cause of the local rise in the water table.

Water quality of the uppermost zone of the Kuwait Group aquifer in the study area is of Na2SO4 type. Samples collected from this water by bailing, showed lower salinity than those of the pumped samples from the same wells, indicating a recharge from rainfall, especially in the areas of topographic depressions. The pumped water quality of both Kuwait Group and the Dammam Formation aquifers in the study area is very similar and of NaCl type suggesting upward seepage of the Dammam water,

Isotopic analyses of groundwater samples provided support to the aforementioned conclusions. The results of 14C and tritium analyses have indicated that the sampled groundwater at the study area had experienced limited recharge from recent rainfall events. The isotopic data also demonstrated clear difference between the ages of the water from the

Dammam Formation and that from the Kuwait Group, the former being older. Furthermore, the depleted oxygen 18 and deuterium contents in the water of the Dammam Formation compared to that in the Kuwait Group differentiated clearly the two.

The leakage of water from the fire service water network, the fresh water network and the brackish network was thought to be a potential source of water responsible for the rise in water table. The isotopic fingerprints and the quality of the water samples collected from these networks were, however, markedly different from those of the groundwater, indicating no recharge from these sources.

The groundwater in the abandoned quarry was found to be highly saline, which could be attributed to the high rate of evaporation. The free flowing groundwater in the recreation lake was also found to be saline.

7. CONCLUSIONS No major source of water was found to cause the rise in water level in the study area. However, the rise of the groundwater in the vicinity of the study area can be attributed to a combination of the reasons as follows:

− The relatively shallow depth of water table in the booster station area under natural conditions.

− The continuous upward seepage of groundwater from the Dammam Formation aquifer. The rate of seepage from the Dammam Formation to Kuwait Group is possibly accelerating with time due to the gradual deterioration of the cement isolation between the casing and the formation with time in hundreds of oil wells located within the study area.

− The relatively low land of the study area which is surrounded by hilly areas leading to ponding of water after rainfalls and its infiltration to the groundwater table. This has been demonstrated by the rise in water levels in the monitoring wells in the vicinity of the booster station subsequent to rainfalls during the execution of the study.

− The interruption of the natural evaporation due to the construction of the booster station.

− The infiltration of contaminated water from the nearby waste disposal pit.

The calibrated and validate model was subsequently used to predict the dewatering requirements for managing the water table rise around BS-140 and the potential drawdown in the water table induced by this dewatering. The four production wells (BS-06, BS-07, BS-08, and BS-09) should be pumped at a rate of 150 l/min (approx 40 gpm) per well to lower the water table down to an average depth of 4.5 m under BS-140. The pumped water can be utilized for several purposes depending on the level of treatment. The

Mohamed Al Senafy


pumping should continue until the free water bodies in the vicinity of BS-140 are completely dried up, at which point, the pumps can be turned off to stay in standby mode until the next rainfall or accidental large water spill causes the water table to rise.

ACKNOLEDGMWNT The author would like to express his gratitude to the Kuwait Oil Company (KOC) for funding the project and the team members of Research & Technology Group of KOC for assisting in the execution of the project. The constant support and encouragement of Kuwait Institute for Scientific Research (KISR) management is acknowledged. The author would also like to express his thanks to the contributors to the study for their help and review of this paper. testing machine.

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