Services
 
Well Drilling

Residential
Irrigation
Industrial & Commercial
Test & Production Construction drilling

WELL REPAIR AND DEEPENING
Well maintenance Services
Rehabilitation Services

WATER SYSTEM INSTALLATION
Well reconstruction
Extraction
Dewatering Holes
Exploration

Geophysical Studies
ERS Surveys
Borehole logging

Pump tests
Step tests
Hold test

Tube well drilling:
Drilling water wells to provide water supplies is one of Geo-Studies Specialism. Geo-Studies has the expertise and technical capability to drill water wells to depths of up to 1000 feet and can complete the well in diameters ranging from 8 inches to 24 inches. Our client list is large and varied, with Geo-Studies providing water wells for industries , farm wells , irrigation purposes, and a huge range of commercial water-supply.

Geo-Studies offer a one-stop water well solution to their clients from survey to drilling to final installation and commissioning. Our vast experience in water well installations and our enviable customer service reputation has established Geo-Studies as one of the leading water well provider companies in the Pakistan, and our technical panel is headed by some of the hydrogeology circles in Pakistan.

Test Drilling:
In order to achieve a quality water supply well, sometimes it is necessary to perform a test hole to verify the integrity of the geological formation, water quality and quantity. A test hole once performed can supply us with the engineering data needed for the design and construction of a water supply well. Test hole drilling can be used for all aspects of verifying.

NON-CORE DRILLING SYSTEMS

Drilling - Reverse Circulation Drill System
This Technique involves in insertion of the drilling fluid (generally Water) though the penetrating borehole depth under hydrostatic pressure and the subsoil samples are withdrawn through its suction from the cutting depths. This method is generally, feasible in the soft and friable type of soil like loose sand and clay.The sampling is generally non coring and the procedure has been developed to increase the speed of drilling. The sampling provides accurate to semi accurate with respect to increase in drilling depth beyond 300 meters.
The above Technique involves in insertion of the drilling fluid (generally Water) though the penetrating borehole depth under

Rotary Drill System
The above Technique involves the entering of the drilling fluid, (generally high optimum gel) through the drilling rods to the cutting spots and the cutting is lifted alongwith the high optimum gels rising from the cutting depth to the ground surface. This drilling may be core / non core types depending upon the requirement. This method has been developed to increase the drilling speed and to drill boreholes to upto 600m depths and also provides accurate sampling procedures to evaluate proper geological and subsurface structural sequences.

Percussion Drill System
Oil For the construction of Tubewells upto 600 meters depth this is an easy, fast and accurate method of drilling. Generally the soft samples of the top soil to 100 meter and then moderately hard to hard soil samples upto 500 meters the samples withdrawn are safe and reliable.

WELL-LOGGING

The term applied to a variety of techniques of measurement of physical properties (by lowering suitable instruments) in a borehole to provide information about the geological strata traversed, or the directional attitude of the borehole itself. Logs may be run to give continuous and detailed information through-out the full depth of a borehole, or they may be restricted to selected zones of particular interest for potential production of oil, gas, or water. In zones of poor core recovery, well-logging has great advantages in providing information of use in solving problems of correlation between adjacent wells, because of the completeness of the well log record. Techniques employed include:

SPONTANEOUS LOG our SELF-POTENTIAL (S.P.) Log. The measurement of variations in potential due to the natural currents which flow in the circuit formed by less permeable strata such as shale, the drilling fluid in the borehole, and more permeable strata such as sandstone.

RESISTIVITY LOG. The measurement of the resistivity of strata by means of electric currents applied via a multi-electrode sende. The correlated interpretation of S.P. and resistivity logs can provide information about the porosity and permeability of strata, and about the nature of the pore fluid.

GAMMA RAY LOG. The measurement of the natural gamma ray activity of the strata by means of a Geiger counter or, preferably, a scintillometer.

NEUTRON LOG. The measurement of induced gamma ray activity due to the capture of neutrons emitted from a suitable source. Gamma ray and neutron logs provide information about the nature of the strata penetrated and give a measure of the hydrogen-bearing fluid content.

TEMPERATURE LOG. The variation of temperature in a bore-hole due to differential rates of heat exchange between drilling fluid and formations can yield information about the nature of the strata. A temperature log can also locate the source of gas flow, zones of lost circulation of drilling fluid, and the position of cement set between casing and the borehole wall.

PHOTOELECTRIC LOG. Changes in the opacity of drilling fluid, determined by photo-electric means, can locate the source of influx of formation water into a borehole.

ELECTRICAL RESISTIVITY METHOD

During resistivity survey a direct current is introduced into the ground through two current electrodes A and B inserted in the ground surface. The potential electrodes M and N are inserted in the ground between the outer current electrodes A and B where the potential difference is measured across these two potential electrodes. By measuring the current (I) between the two current electrodes A and B and the N, resistivity of the corresponding subsurface medium enclosed between the current electrodes is obtained.

Normally, the medium is inhomogeneous or anisotropic therefore, the resistivity is known as apparent resistivity and is computed by the following formula:


Equation (1) is the general equation for calculating apparent resistivity in electrical resistivity prospecting.

The apparent soil resistivity obtained in this case represents an average value of the soils within the sphere of influence of the test set up.

FIELD PROCEDURE

Signal averaging resistivity-measuring equipment (SAS-4000) is used for measuring current and potential values in the filed. `in the case of the Schlumberger array the electrodes are placed in a straight line symmetrically about the center point. The two outer electrodes A and B are used for the current, and the resulting potential difference is measured across the two inner electrodes M and N. The array is characterized by the distance of the current and potential electrodes from the center, which are referred to AB/2 and MN/2 respectively. MN/2 is always kept sufficiently small relative to AB/2. The average potential gradient measured between M and N is a close approximation to the potential gradient at the center of the array.

The ground is energized through the outer A and B electrodes under high D.C. voltage and constant current is made to flow through the ground with the help of “Power Pack” provided with the measuring equipment. The constant selected current I (In milli amperes) passing through the two current electrodes and resulting potential difference V (in milli/micro volts) between the two potential electrodes is processed by the equipment and the resistance is displayed for the corresponding reading.

The distance between the two potential electrodes is smaller than the distance between both potential electrode and its adjacent current electrode. Measurements are taken and noted before re-positioning the electrodes. The mid point of the electrodes is fixed at the sounding location, while the length of the configuration is gradually increased accordingly in order to measure the resistivity at given depth level. At each location, in one sounding, apparent resistivity values are obtained at different specific depths.

METHOD OF EVALUATION

The resistivity filed curves are obtained by plotting the apparent resistivity values against depths on a bi-log graph paper. After smoothing the plotted curves all the field data is registered to computer. The interpretation of sounding is done with the help of computer and direct interpretation software. The resistivity sounding data collected from the area is interpreted by computer-aided techniques using INTERPEX USA software, RESIXP. The layer models are calculated by an interactive procedure. During each iteration, the model parameters are adjusted and the deviation of the corresponding curve from the measured curve is checked. The deviation is defined by the RMSE (root mean square error), which is displayed after each iteration. At the end of calculations, the model, which results in the smallest error, is plotted showing layer’s true resistivity and corresponding thickness.

In practice, interpretation of resistivity sounding is invariably subjected to the principle of equivalence i.e. any resistivity sounding can be matched with several slightly deviating model curves, representing different sub-surface resistivity stratification depending upon ground water behavior of the area. The interpreter of the data is therefore, confronted with hundreds of options for a single field curve to make his selection of the most consistent model of the sub-surface conditions.

The interpreted or so called true resistivity values of the sub-surface layers and the calculated formation factor of the area have been used to estimate electrical conductivity of the ground water for the interpreted layers. The interpreted sub-surface hydrogeological conditions are shown in the form of vertical columns at respective sounding points in depicting sub-surface hydrogeological conditions.

INTERPRETATION OF V.E.S. DATA

The measured resistivities when subjected to interpretation process have yielded sub-surface electrical layers. These interpreted electrical layers need a correlation with the sub-surface geological conditions. This transformation of interpreted layers into lithologic units is essential based on the geological information obtained from test holes, tube wells, and other data of previous investigations conducted in the project area. The interpreted sub-surface conditions at each sounding location are derived in terms of resistivity.