Establishing relations between hydraulic parameters and geoelectrical properties for fractured rock aquifer in Dammam formation at Bahr Al-Najaf Basin

Dissertant

al-Shammarii, Ala Muhsin Atiyyah

Thesis advisor

al-Yasi, Amin Ibrahim Hassun Hamzah
al-Fayyd, Jasim Muhammad Thabit Ibrahim

Comitee Members

Ghazal, Sabah A. G.
al-Banna, Ahmad Shihab Ahmad
Ahmad, Muhannad M.
Khurshid, Salman Zayn al-Abidin
al-Shamma, Aysar Muhammad

University

University of Baghdad

Faculty

College of Science

Department

Geology Department

University Country

Iraq

Degree

Master

Degree Date

2012

English Abstract

he current study is regarded as an attempt to employ the results of Vertical Electrical Sounding (VES), conducted near wells and boreholes, with available pumping test information to construct the hydrogeophysical model for a fractured rock and karstified aquifer in Dammam L st.

Fn.

The study also aims to establish mathematical empirical relations by combining the geoelectrical and hydrogeological data for estimating theoretically its hydraulic parameters, in order to reduce the processes of pumping test, which are usually costly and time consuming.

The studied area comprises ( 765km² ) within Bahr Al- Najaf basin and lies between longitudes (44º 00ˉ – 44º 30ˉ) East, and latitudes (31º 40ˉ– 32º 05ˉ) North.

It was geoelectrically surveyed with twenty five (VES) stations using Schlumberger array and along three electric profiles.

Two of them run in the direction of strata strike and almost parallel to each other, while the third is in a perpendicular direction to those in two locations.

Maximum lengths between current electrodes (AB) and between potential electrodes (MN), in every measuring station reached (1000m) and (160m) respectively.

Nine of total stations were also benefitted from the use of (Cross-VES) survey along two perpendicular electric lines to identify subsurface variations of the anisotropy, as well as determining direction of groundwater flow in Dammam aquifer, which is hydrogeologically considered anisotropic medium by its directional preferential permeability.

2D imaging survey was carried at two stations, using Wenner array along two electric lines of (390m) length for each one, and in different directions.

These stations are located near other two (VES) stations in order to detect the cause of emission of (HR2RS) gas in Ezia region, which is determined by occurrence of fractured zone at depth (60m) approximately.

The upper confining layer of M.

Dammam aquifer is also found at a depth of (40m), that 2D imaging survey is able to obtain more detail information about the variations of the apparent resistivity of subsurface rocks.

(VES) Field curves were first manually interpreted with partial match-ing technique, using theoretically calculated master curves, in conjunction with the auxiliary curves of (Ebert) method.

While the initial earth models were secondly checked and improved through the inverse modeling of (IPI2Win) program, and the 2D imaging field measurements were interpreted by (RES2DINV) program.

The results of inverse modelings related to these two kinds of surveys were used to construct three geoelectrical sections of (VES) and two inverse modelings of 2D imaging along the selected electric profiles.

All geoelectrical sections were calibrated with lithologic sections of the vicinity wells and with available structural and hydrogeological information to match them with the true geology of the studied area.

The predicted subsurface structure as shown from the hydrogeophysical model includes occurrence of a confined aquifer with an uniform saturated thickness that reaches (160m), and belongs to M.

Dammam member.

It is characterized by extensive underground drainage system, as deduced from many self-flowing and artesian wells of high discharges.

The reason may be caused by presence of enlarged fractures caused by structural features as Abu Jir fault and the local block faulting.

These features are verified by the results of the qualitative and quantitative interpretations.

Correlation tests were carried out between hydraulic parameters [hydraulic conductivity(k) with transmissivity(T)] estimated by pumping test, and the geoelectrical properties [Dar-Zarrouk parameters].

In addition relations between the porosity (φ) and bulk resistivity(ρo), are obtained from the interpretation results.

Eleven graphical empirical relations were extracted to depict main aquifer characteristics and estimate mathematically its hydraulic parameters.

Relations between longitudinal conductance(S) with both (k) and(T)parameters are preferred because this aquifer is highly saturated, as verified from its water saturation of (0.9) value and its porosity ratio of (22%), calculated by applying Archie's equation.

Average value of (RMS%) is calculated as(6%) between the values of (k) and (T) estimated mathematically and those estimated by the pumping tests.

A map of groundwater flow directions is drawn relaying on values of anisotropic factors of nearby eight boreholes to show the trends of main fractures.

Main Subjects

Earth Sciences, Water and Environment

No. of Pages

160

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-609289