تحديد الخزان الجوفي وتقييم معاملاته الهيدروليكية من القياسات السطحية للمقاومة النوعية في حوض شهرزور شمال العراق == Aquifer delineation and evaluation of hydraulic parameters from surfacial resistivity measurements in Sharazoor basin ? North East Iraq
Author name:
عبد الله كريم امين
Supervisor name:
جاسم محمد ثابت | بختار قادر عزيز
General topic:
Geology
Specific topic:
Geophysics
Degree:
Doctorate
University:
University of Baghdad
Language:
English
University location:
Baghdad
First pages:
30T354 - p.pdf
Abstract:
The studied area is located at (8Km) south east of Sulaimaniya city - North East Iraq. It is represented by Sharazoor plain. The studied area was surveyed by (281) Vertical Electrical Sounding (VES) points distributed along six profiles running parallel to the strike direction of strata and covered an area of (200 km2).Apparent resistivity curves are plotted and interpreted using of both partial matching with auxiliary curves by Ebert method and the advance (IPI2 - win) software program through the application of forward calculation and inverse modeling.The quantitative interpretation results are used to construct six geoelectrical sections along profiles, and then converted to geological sections after correlating with the geological wells information distributed throughout the studied area. The results of interpretation show that the unconfined aquifer consisted of gravel, sand with clay of recent alluvial deposits with the upper part of middle Tanjero Fn.consisting alternating layers of sand, limestone, marly limestone overlying marly layer, which acts as an impermeable layer. This is clearly observed from well lithological sections shown in fence diagram passing throughout the studied area.Porosity values of the aquifer in all the distributed wells of the studied area are calculated through the applying of both Archie formula and a technique of density formula. The porosity values of both formulas are drawn with the resistivity values of the aquifer in the wells. The relationship of the density formula is given a positive linear relationship with a relative coefficient (R=98.29) for recent deposit aquifer with the presence of clay content, through which it decreases from north west beginning part toward the south east end part of the studied area. This will be clearly observed from increasing of the porosity. Furthermore there is no any condition for its application. Where as for Archie formula relationship shows also a linear positive relationship with lower relative coefficient (R=87.55). Therefore density formula can be considered as an applicable technique for calculating porosity of the recent deposits with clay. Further more the extracted relation may considered as slandered ration for direct calculation of porosity values from aquifer resistivity values in the studied area and surrounding areas having the same sequences.The estimated values of the hydraulic parameters especially transmissivity (T) using both the manual method by Cooper Jacob and the computer software by (AQTESOLVE) program. The results of both methods are shown in Table (5 - 3).Comparing values of (T) by both methods, the computer program gives higher values, which is probably due to the correction of the manual values by taking into account both outer diameter (rw) and casing diameter (rc) of the single well aquifer test. The hydraulic conductivity (K) is calculated by dividing transmissivity by the saturated thickness of the aquifer. Aquifer transmissivity values are range between (22.81 m2/day) from the beginning to (44.21 m2/day) at the central basin of the studied area. And hydraulic conductivity (K) values range between (0.68 m/day) at the NW - part to (1.6 m/day) at the SE - part of the studied area. Both results values of (T) and (K) are located within the standard range values of unconsolidated recent deposits, which are clearly shown increasing values from the beginning part toward the central part at the end of the studied area. Such increasing can be related to diminishing of the clay content as well as increasing of sand and gravel in the aquifer toward the central basin located at the south eastern - part of the studied area. The results of the hydraulic parameters are tied with the resultant geoelectrical parameters, on the bases of the relations given by (Frohlic, 1994). According to these relations, Frohlic has suggested two models for the aquifer. In the first model, he suggested a variable thickness with constant resistivity and hydraulic conductivity, while in second model, he suggested a constant thickness with variable resistivity and hydraulic conductivity. The extracted relations of the present study are not conformable to any of the Frohlics linear models. But by comparing with modern models suggested by Singh (2005), they show best fit with the positive hyperbolic relationship, because all the three parameters are variable throughout the studied area. The interpretation of such relationship is related to decreasing for the aquifer clay content and thus increasing the resistivity values from NW - part toward the SE - part of the studied area. Consequently the ground water movement takes the same direction. It can be possible to evaluate hydraulic parameters from geoelectrical parameters. Transmissivity (T) and hydraulic conductivity (K) can be estimated from resistivity (ñ) or transverse resistivity (ñTr) relations or any other extracted relations in this study can be applied.Geologic sections and extracted relations between geoelectrical and hydraulic parameters can be shown that Sharazoor basin includes of unconfined aquifer. The aquifer consists of recent alluvial as (gravel, sand with clay content) and repeated thin sequence of part of middle Tanjero Fn. (sandstone, limestone and marly limestone) overlying impermeable layer of marl. The thickness values of the aquifer range between less than (20m) and resistivity values (32Ù.m) at NW - part consisting of recent and thin layers of upper part of middle Tanjero Fn., where as it increases to more than (80m) and resistivity value (72Ù.m) with increasing recent deposit and decreasing or disappearing limestone and marly limestone toward the central basin.Further more it is also concluded that the resistivity values for recent alluvial deposit range between (20Ù.m) to less than (60Ù.m), and for middle Tanjero Fn.range between more than (60Ù.m) to around (90Ù.m), where as for lower Tanjero Fn. from more than (90Ù.m) to more than (150Ù.m).
