Methods of Oil & Gas Exploration

There are three main methods of oil exploration.

1. Geological Technologies. Through observing and studying the strata and rocks exposed on the ground, it analyzes and synthesizes the geological data to understand whether there are conditions for oil and gas generation and storage in an area. Finally, it puts forward the evaluation of oil and gas in this area and points out the favorable areas. Sometimes oil and gas reservoirs may be found directly in areas with exposed rocks.

2. Geophysical Technology. In areas where the surface is covered by loose sediments or deserts, there are no rocks on the surface and sea surface in the sea covered by seawater, so the geological method is greatly limited. At this time, geophysical methods should be applied. It is a petroleum exploration method based on the principles of Geology and physics and using new technologies in the fields of electronics and information theory. Various physical instruments are used to observe various physical phenomena on the earth's crust, so as to infer and understand the characteristics of underground geological structure and look for possible oil storage structures. The main geophysical methods used in modern petroleum exploration include gravity exploration, magnetic exploration, electrical exploration and seismic exploration.

3. Drilling Method. Whether the geological structure found by geophysical method stores oil and gas needs to be determined by drilling.

Geophysical Technology

The oil field is buried deep underground, hundreds of meters shallow and several kilometers deep. Geophysical exploration is the most effective exploration method. It is an exploration method to find out the distribution form of underground rocks and oil and gas accumulation by studying some physical properties of strata (rocks).

Geophysical exploration is based on the existence of different rocks under the ground. These rocks have different physical properties, resulting in different physical fields. We measure them on the surface with various precision instruments, and then analyze and study these fields and explain them, so as to understand the geological characteristics such as underground structure and lithology. There are different methods according to different physical properties.

1. Gravity exploration method: Based on the density difference of rock, it is a method to measure the gravity change caused by it on the ground.

2. Magnetic exploration: A method of measuring the change of magnetic field caused by different magnetism of rocks on the ground.

3. Electrical exploration: A method of measuring the change of electric field caused by rock conductivity, magnetic conductivity and dielectric properties on the ground.

4. Seismic exploration: Solve geological structure problems through the study of rock elastic properties. Through the propagation of seismic waves generated by artificial excitation in the earth's crust, physical phenomena such as reflection and refraction can be generated when encountering interfaces with different elastic properties. The reflected and refracted seismic waves are received and recorded on the ground by seismograph. After analysis and research, the buried depth and other elements of interfaces of different underground rock strata are calculated to understand the structural form of the stratum.

Geophysical Logging Method

Geophysical logging is the application of the principles of physics to solve geological problems. It uses special instruments and equipment into the well to measure some characteristics of the formation. Its purpose is to use logging technology to find underground oil and gas resources and solve specific problems in the process of oil and gas field exploration and development, such as lithology, sedimentary facies, sedimentary environment, geological structure of stratum, distribution law of oil, gas and water, water flooded condition and state of oil and gas reservoir, reservoir performance evaluation, oil and gas reservoir description and so on. Logging is a continuous measurement of the formation through which the well passes. Each logging data is an objective reflection of some characteristics of the formation. For example, resistivity logging data is a reflection of the electrical characteristics of the formation, acoustic logging data is a reflection of the acoustic characteristics of the formation, and radioactive logging is a reflection of the nuclear physical characteristics of the formation.

Seismic Exploration Method

Seismic exploration is to use the elastic wave excited by artificial methods to locate mineral resources (including oil and gas, ore, water, geothermal resources, etc.), determine the archaeological location and obtain engineering geological information. The data obtained from seismic exploration can be used in combination with other geophysical data, drilling data and geological data, and the information about structure and rock type distribution can be obtained according to the corresponding physical and geological concepts.

The production work of seismic exploration can be basically divided into three links:

The first stage is field work. In areas with oil and gas potential preliminarily determined by geological work and other geophysical exploration work, survey lines are arranged, seismic waves are artificially excited, and the propagation of seismic waves is recorded by field seismograph to obtain a tape recording the ground vibration.

The second stage is indoor data processing. Convert the seismic information recorded in the field into a form convenient for geological interpretation, that is, convert the data on the tape into a corrected seismic record section similar to the display of geological structure. The more important purpose of data processing is to eliminate or suppress the noise in seismic records, improve or strengthen the reflection information, and improve the resolution of reflection signals.

The third stage is the interpretation of seismic data. Based on the theory of seismic wave propagation and the principle of petroleum geology, combined with geological, drilling and other geophysical data, this paper makes an in-depth analysis and research on the seismic profile, determines the shape and spatial position of the geological structure, speculates the lithology, thickness and interlayer contact relationship of the formation, determines the stratigraphic trap and the possibility of oil and gas, and directly provides the well location for drilling.

Seismic exploration methods are widely used in the general survey and exploration of oil, natural gas and coal fields. At the same time, the seismic exploration method can solve the detection of plant site, dam foundation and bridge site, the detection of phreatic water level and aquifer, and the tracing of fault fracture zone in hydrogeology and engineering geology. Among various geophysical methods for oil and gas exploration, seismic exploration has become the most effective method.