Hydrocarbons are organic compounds that contain carbons and hydrogens (such as oil and gas) which can be found in many countries around the world. However, there are several steps (preliminary works) that have to be done in order to explore and drill hydrocarbons (oil and gas). The preliminary work includes finding a prospective location as recommended by geophysicists and geologists (locating the oil field), land leasing agreement and approval from authorized body, rig personnel and infrastructure.

Finding a prospective location (locating the oil field)
There are 3 methods that geophysicists and geologists use to find (determine) the oil field on land (Onshore). The methods are involving on collecting seismic data and non – seismic data by using explosive, magnetometers, and gravimeters.
1. Seismic exploration
In seismic exploration, sound is used as a shock wave. The sound is transmitted into the ground by an explosive, such as dynamite (by drilling into the ground) or by a thumper truck (by slamming heavy plates into the ground) (Ghosh 2009). The shock waves (sound) travel beneath the surface of the Earth and are reflected back by the various rock layers, and these reflections travels at different speeds depending upon the type or density of rock layers through which they must pass (Freudenrich 2005). The reflections of the shock waves are detected by vibration detectors and the readings are then interpreted by seismologist for signs of oil and gas traps (Freudenrich 2005).


Thumper Truck, Oil and Natural Gas Project (The Energy Lab 2011)

2. Magnetometers

Another method to locate the oil field is by using magnetometers.
A magnetometer is used to measure the strength or direction of the magnetic field, produced either in the laboratory or existing in nature (Ghosh 2009). It can measure tiny Changes in the earth’s magnetic field caused by flowing oil (Freudenrich 2005). Magnetic properties vary based on the composition of the earth’s surface, so by using magnetometers, the strength of the earth’s magnetic field at a specific point on the earth’s surface can be determine (Ghosh 2009). Two types of magnetic instruments are used to measure the slight difference in magnetism in rocks, the field balance and the airborne magnetometer (Petty 2011). The field balance is used on the earth's surface to measure magnetism in specific locations and the airborne magnetometer is used to measure the magnitude of the earth's total magnetic field over a large area (petty 2011). Since there is a correlation between low magnetic readings and rocks that contains oil (mostly oil occurs in sedimentary rocks that are nonmagnetic), thus oil field can then be determined (Ghosh 2009).

Backpack G-859 Magnetometer (Geometrics 2011)

3. Gravimeters

Gravimeter is used to measure and record the differences in the earth’s gravitational field at various underground locations (Ghosh 2009). A gravimeter is specialized for measuring the constant downward acceleration of gravity, which varies by about 0.5% over the surface of the Earth and gravimeters are typically designed to be much more sensitive in order to measure very tiny fractional changes within the Earth's Gravity caused by nearby geologic structures or the shape of the Earth and by temporal tidal variations, which means that gravimeters are liable to extraneous vibrations including noise that tend to cause oscillatory accelerations (Ghosh 2009). The differences in gravitational field, represents the differences formations and rock types (Ghosh 2009). Since rocks that contain oil have different density of the ground, therefore by using gravimeters, geophysicists can measure tiny changes in Earth’s gravitational field that could indicate flowing oil (Freudenrich 2005, Ghosh 2009).


An early version of a full tensor gravimeter, (Bamford 2011)

Leasing agreement and approval from authorized body

After the oil field has been located, it must be surveyed to determine its boundaries, and environmental impact studies may be done (Freudenrich 2005). Agreements (permits) must be completed to make a good effort to reach surface access agreements with surface private surface owners (Snow 2007). Therefore leases agreements, titles, and right of way accesses for the land must be obtained and evaluated legally (Freudenrich 2005).

Rig personnel and infrastructure

The next step to start drilling is by selecting rig personnel and preparing infrastructure. Rig personnel are determined both from Oil Company and contractor. Personnel from Oil Company (Company man) are drilling supervisor and drilling engineering, and from contractor is drillers which includes roughnecks and crane operator (general labour) (Bourgoyne et al 1991). Once the rig personnel have been determined, the next step is preparing the land (infrastructure):

1) Accommodations for workers must be prepared ;

2) The land is cleared and access roads must be built;

3) Because water is used in drilling, there must be a source of water nearby. If there is no natural water, a water well must be drilled;

4) A reserve pit must be prepared, which is used to dispose of rock cuttings and drilling mud during the drilling process, and line it with plastic to protect the environment (Freudenrich 2005)