Detection of Petroleum

There is no instrument for direct detection of oil underground. The first step in petroleum exploration, is to find most probable location for a test well, after mapping the sub-surface formations, using various methods of Geological and Geophysical exploration techniques.

Once a test well penetrates various formations underground, it is necessary to have available group of methods and tools that are capable of locating and evaluating the commercial significance of sedimentary rocks. The use and interpretation of these methods are called Formation Evaluation.

Formation Evaluation is carried out when the well is in progress. As and when the drilling is in progress, the cutting samples, core samples and fluids extracted from the core is studied. When part of the well is completed wireline logs are recorded to evaluate the different formations encountered in the drilled section.

In 1927 the first electrical logging tool was recorded in northern France. Photographic film recorder was introduced in 1936. By then, combination of the electrical log consisted of SP curve were recorded simultaneously.

Dipmeter which was introduced in 1930 with anisotropy dipmeter tool was improved in 1943 with three arm SP sensors. This was replaced by 3micro resistivity arms in 1950. Dip direction and magnitude are recorded by processing the data through a software system. The Gamma Ray (GR) log, a neutron log represented.