Data Interpretation

satellite imagery – изображение спутниковых данных

photo mosaics – фотосхема

dimensional – мерный, имеющий столько-то измерений, пространственный

seismic imaging – сейсморазведочное построение

logging –каротаж, геофизические исследования в скважине

core sample- колонка породы, образец керна

There is a saying in the petroleum industry that "oil is found in the minds of men." Even with the most sophisticated scientific techniques, finding hidden petroleum deposits involves a large measure of creative interpretation. Until a hole is drilled, the existence of oil or gas is theoretical; "dry" holes are common even in established production areas. Once the resource is found, its value also depends on the "minds of men": exploration and production are expensive endeavours, worthwhile only when society needs the oil or gas badly enough to pay for it.

There are many sources of data and information for the geologist and geophysicist to use in the exploration for hydrocarbons. However, this raw data alone would be useless without careful and methodical interpretation. Much like putting together a puzzle, the geophysicist uses all of the sources of data available to create a model of the structure of the layers of rock under the ground. Exploration requires the analysis of a lot of different types of data such as satellite imagery, digital aerial photo mosaics, seismic surveys, surface geology studies, subsurface and cross section interpretations and images, well locations, and existing infrastructure information. Some techniques, including seismic exploration, lend themselves well to the construction of a hand or computer generated visual interpretation of underground formation.

One of the greatest innovations in the history of petroleum exploration is the use of computers to compile and assemble geologic data into a coherent 'map' of the underground. Use of this computer technology is referred to as 'CAEX', which is short for 'computer assisted exploration'. With the proliferation of the microprocessor, it has become relatively easy to use computers to assemble seismic data that is collected from the field. This allows for the processing of much larger amounts of data, increasing the reliability and informational content of the seismic model. There are three main types of computer assisted exploration models: 2-dimensional or 2-D (creates an image that includes length and width), 3-D (creates an image that includes length, width, and depth), and most recently, 4-D (produces a 4D seismic history of the formation with time as the fourth dimension). Although this technology is very useful, it is also very costly. 3-D seismic imaging can cost anywhere up to $1 million per 50 square mile area. The generation of 3-D images requires data to be collected from several thousand locations, as opposed to 2-D imaging, which only requires several hundred data points. In addition to broadly locating petroleum reservoirs, 3-D seismic imaging allows for the more accurate placement of wells to be drilled. This increases the productivity of successful wells, allowing for more petroleum and natural gas to be extracted from the ground. In fact, 3-D seismic can increase the recovery rates of productive wells to 40-50 percent, as opposed to 25-30 percent with traditional 2-D exploration techniques. The use of 4-D imaging can result in recover rates of 65 to 70 percent.

These imaging techniques, while relying mainly on seismic data acquired in the field, are becoming more and more sophisticated. Computer technology has advanced so far that it is now possible to incorporate the data obtained from different types of tests, such as logging, production information, and gravimetric testing which can all be combined to create a 'visualization' of the underground formation. Thus geologists and geophysicists are able to combine all of their sources of data to compile one clear, complete image of subsurface geology.

Other sources of data, such as that obtained from core samples or logging, are taken into account by the geologist when determining the subsurface geological structures. It must be noted, however, that despite the amazing evolution of technology and exploration techniques, the only way of being sure that a petroleum or natural gas reservoir exists is to drill an exploratory well. Geologists and geophysicists can make their best guesses as to the location of reservoirs, but these are not infallible.

Ex.1 Are the following statements TRUE or FALSE?

1. Many various sources of information and data are used in petroleum exploration.

2. Their detailed interpretation is necessary only in rare instances.

3. Data interpretation is performed by geologists.

4. Data interpretation makes possible to create a model of underground formation.

5. Data interpretation is usually done only on the basis of analyses of seismic surveys’ data.

6. 'CAEX' stands for 'computer assisted explanation'.

7. There are four types of 'CAEX' models.

8. 4-D seismic imagining provides the most reliable data interpretation.

9. All sources of data can be combined when creating a 'visualization' of the underground formation.

10. The only method which proves that a petroleum or natural gas reservoir exists is logging test.

Ex.2 Can you comment on the saying "oil is found in the minds of men"?

Ex.3 Compare different types of computer assisted exploration models.

Ex.4 List all methods of oil exploration mentioned in the text.