Flower Pollination Algorithm for the Inversion of Schlumberger Sounding Curve

Inversion of schlumberger sounding curve is non-linear, and multi-minimum. All linear inversion strategies can produce local optimum, and depend on the initial model. Meanwhile, the non-linear bionic method for inversion problems does not require an initial model, simple, flexible, derivation-free mechanism and can avoid local optimum. One of the new algorithm of the non-linear bionic method for geophysical inversion problem is the Flower Pollination Algorithm (FPA). The FPA is used for the inversion of schlumberger sounding curve. This algorithm was stimulated by the pollination process for blooming plants. The applicability of the present algorithm was tested on synthetic models A-type and KH-type curve. Numerical tests in MATLAB R2013a for the synthetic data and the observed data show that FPA can find the global minimum. For further study, inverted results using the FPA are contrasted with the damped least-square (DLSQR) inversion program, Particle Swarm Optimization (PSO), and Grey Wolf Optimizer (GWO). The outcomes of the comparison reveal that FPA performs better than the DLSQR inversion program, PSO, and GWO.

Interpretasi Struktur Bawah Permukaan Untuk Mengetahui Keberadaan Sumber Mata Air Di Daerah Jaboi Sabang Dengan Menggunakan Data Geolistrik Konfigurasi Schlumberger

Survei geolistrik telah dilakukan di daerah Jaboi Sabang untuk mendapatkan<br />resistivitas struktur permukaan dengan menggunakan metode Schlumberger sounding<br />geolistrik. 4 (empat) elektroda diinjeksikan ke dalam tanah di mana resistivitas diukur<br />menggunakan Nainura NRD 2.2 resistivity meter. Data yang didapatkan dianalisisa dengan<br />software IXID v2. Hasil menunjukkan bahwa akuifer yang ditemukan dari model ini cukup<br />baik untuk eksplorasi mendapatkan air bersih pada kedalaman 1,5-6,4 meteran. Nilai<br />resistivitas pada lapisan ini berkisar 35,4 - 41,4 ohm meter yang sesuai dengan resistivitas<br />air.

MATLAB code for data-driven initial model of 1D Schlumberger sounding curve

A MATLAB code automatically performs partial curve matching of 1D apparent resistivity data recorded with the Schlumberger electrode array configuration. The two-layer master and auxiliary curves are used to systematically match through the branches of data extracting the corresponding model properties. Partial curve matching is a classical interpretation procedure of the sounding curve, which has been done manually. Results from the manual and automatic procedures are compared. The matched geoelectric models from the automatic process are retrieved more quickly, and these results are consistent because the process is digitalized and are not dependent on human numerical accuracy judgment. Magnitudes of random noise affect the final matched model parameters, yet these values are sufficient to be initial models for subsequent nonlinear inversion. It is hoped that for an inversion workflow, the code can be included to automatically find an initial resistivity model.

Combining Resistivity and Aeromagnetic Geophysical Surveys for Groundwater Exploration in the Maghnia Plain of Algeria

The Maghnia plain in western Algeria is filled by Plio-Quaternary and Miocene sediments that rest unconformably on a basement of Jurassic rocks. Electrical sounding (VES), magnetic data, well information, and hydrogeological data have been used to explore for groundwater potential in the Maghnia plain. The interpretation of Schlumberger sounding data was first calibrated with the lithology of available nearby wells. Four geoelectrical layers were identified within the study area. They are a thin near surface topsoil layer with variable resistivities, a moderate resistive aquifer (15–30 ohm-m), a resistive aquifer (40–70 ohm-m), and a conductive clay layer (1–10 ohm-m). Near Sidi Mbarek, the geoelectric section is reduced to three layers: a topsoil layer, a conductive layer corresponding to the Miocene marls, and a deep resistive layer that correlates with the Oxfordian sandstones. The interpretation of VES data and the enhancement techniques of magnetic data enabled the identification of a number of unmapped faults that occur near recharge zones close to adjacent mountains. This study enabled us to study the extension of the known Plio-Quaternary aquifer of the Maghnia plain and to explore the possible existence of a second deep groundwater aquifer in Oxfordian sandstones.

Electrode arrays for measuring groundwater flow direction and velocity

The movement of 2000 liters of salt water after injection into groundwater within gravels a few meters below the ground surface at three injection sites was traced by six different resistivity monitoring arrays; the resistivity rectangle, Schlumberger sounding, Wenner sounding, Wenner fixed‐spacing, mise‐à‐la‐asse and downhole electrode array. Five of the arrays indicated groundwater flow direction and seepage velocity. As evidence indicates, similar geological and hydrogeological conditions exist at the injection sites. Therefore, comparisons between the sensitivity of the five arrays can be made and are as follows: resistivity rectangle—maximum decrease of 60 percent in derived potential differences; Schlumberger sounding— maximum decrease of 28 percent in measured apparent resistivity; Wenner sounding—maximum decrease of 20 percent in measured apparent resistivity, Wenner fixedspacing—maximum decrease of 22 percent in apparent resistivity; downhole electrode—maximum decrease of 38 percent in measured resistance. Measured potentials and derived values of potential gradient measured by the mise‐à‐la‐masse array indicated groundwater flow direction but not seepage velocity. Estimates of seepage velocity given by the resistivity arrays for the three salt water injection sites are between 260 ± 40 m/day and 700 ±100 m/day. These estimates are in broad agreement with values of seepage velocity derived from the point‐dilution technique, from previous salt water injection experiments, and from groundwater conductivity measurements using downhole probes.