Res2dinv Lecture.pdf

Application of 2DRESINV Program for Interpretation of 2D Electrical Resistivity Data

Dr Asem Ahmed Hassan Dept. Of Petroleum Geology and Minerals College of Science, University of Diyala

RES2DINV: RES2DINV is a windows based program that automatically determines a 2D resistivity model (interpretation) for the subsurface for the data obtained from Electrical Resistivity Imaging ERI surveys.

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ERI Method is based on the traditional four-electrode resistivity method combined with automatic switching of a larger number of electrodes

Electrical Resistivity Method: Background Electrical resistivity is a physical property of a material that describes its ability to resist the flow of electricity. A DC or low frequency current is injected through current electrodes C1 & C2 and the resulted voltage difference is measured using voltage electrodes P1 & P2 from which soil resistivity is calculated.:

∂ ρ : Resistivity (Ohm.m) ∆V : Voltage difference (Volts)

I : Current (Amps) K: Geometric Factor (m) C1, C2 Current Electrodes P1, P2 Voltage Electrodes

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1D Electrical Resistivity Studies Resistivity meter, 12 Volt Battery, 2 current reels (750m each), 2 voltage reels (250m each) and four stainless steel electrodes System

∂ •VES (Vertical Electrical Sounding) •CST (Constant Separation Travers) or Horizontal Profiling

VES

CST

2D Electrical Resistivity Imaging ERI

∂ Advantageous: (1) Speed up data acquisition (2) Provide large data sets to construct 2D and 3D resistivity images (3) Offer the flexibility to choose a suitable electrode arrangement for a particular problem, which in turn reduces the effort and laborious electrode switching using manual systems

ERI Method: the main steps ERI is a technique of construction an image of the subsurface electrical properties. Subsurface resistivity distribution can be related to physical conditions of interest such as lithology, porosity and water content..etc.

∂ Calculating the resistivity distribution that is consistent with observed data

2D Model

3D Model

2D Data Collection

Wenner Array

C1, C2 Current Electrodes P1, P2 Voltage Electrodes

Data Level

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Data interpretation (RES2DINV program)
RES2DINV is a windows based program for interpretation the 2D resistivity data.
An example of the electrodes arrangement and measurement sequence that can be used for a 2-D electrical imaging survey is shown in the figure. This program is designed to invert large data sets up to 21000 data points collected with a system with a large number of electrodes up to 16000 electrodes.

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Data interpretation (RES2DINV program)
The 2-D model used by the inversion program, which consists of a number of rectangular blocks, is shown in the Figure.
The arrangement of the blocks is loosely tied to the distribution of the data points in the pseudosection.
The distribution and size of the blocks is automatically generated by the program using the distribution of the data points as a rough guide.

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RES2DINV: Inversion process
The purpose the inversion is to find a 2D model that will produce a model response that matches the measured apparent resistivity values. An initial model is created, and the program modifies it so as to reduce the difference between the calculated and measured apparent resistivity values

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RES2DINV: Inversion Program
This program can be used for Wenner, pole-pole, dipole-dipole, poledipole, Wenner-Schlumberger and dipole-dipole arrays. In addition to these common , the program even non-conventional arrays.
Besides normal surveys carried out with the electrodes on the ground surface, the program also supports underwater and cross-borehole surveys!

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Using the program:

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Data file:

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Data format:

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Editing the data:

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Data inversion:

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Display the results:

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Case Study (1): Determination of Groundwater Level at University Diyala Campus Site (4th Stage graduation research)

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Field work (Data Collection) Wenner Array

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Wenner- Schlumberger Array

Field Work (Data Collection)

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Data Preparation

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Data Interpretation (RES2DINV

Program)

Wenner Array

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Wenner- Schlumberger Array

Case Study (2):

Detection of Buried Pipes at Diyala University Campus Site Using 2D Electrical Resistivity Imaging Technique

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Study Area

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Study Area Geotechnical soil boring log (Al-Ebdaa, 2015)

A buried pipe in the study area

Field work (Data Collection)

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Data Interpretation (RES2DINV Program) Wenner

Wenner- Schlumberger

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Dipole-Dipole

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Thank You Thank You

Thank You