FractureCSP (Common Scattering Point) – technology of processing and interpretation of the standard seismic data to identify zones of fracturing allocated from the total wave field scattered waves.
The essence of innovation
CSP technology allows to temporary diffractors cubes containing the image only scattering elements (CSP-diffractors) and time of Cuba reflectors without these scattering elements (CSP-reflectors). Cuba CSP-diffractors contain unique information about fractured-cavernous zones, which in conventional seismic data processing is completely lost amid a much more intense reflecting elements.
The team consists of highly qualified staff, experts in the oil and gas industry and mathematics from around the world.
Specialists of the company “Технологии обратных задач” repeatedly participated in international exhibitions and conferences.
- The accuracy of prediction of fracturing technology Fracture-CSP over 80%.
- Not required to conduct additional field work.
- The technology is based on a mathematically exact solution of the inverse scattering problem, this eliminates the influence of human factor on the result.
- 100% domestic development without any external dependencies.
The results achieved
- The technology is implemented in a software package CSP–PSTM 2D/3D.
- To date treated more than 15 000 linear km of seismic profiles 2D and 5,000 sq km of 3D seismic on 40 fields.
- The effectiveness of the technology proven in reservoirs from the fractured-cavernous-type reservoir for the oil and gas provinces of Russia and foreign countries.
- Clients – the world’s largest oil and gas company.
According to geologists, fractured reservoirs contain more than 25% of the world’s oil reserves. The market of 3D seismic work in the development of continental and offshore fields today are a multibillion – dollar industry (in the U.S. Only for research in the area of seismic operations spent about $ 1 billion per year).
Mapping of cavernous fractured reservoir based on the method FractureCS
1. A description of the method
A considerable part of world reserves and production of hydrocarbons is concentrated in the areas of distribution of productive reservoirs of fractured-cavernous type. The regions where the exploration and development of oil and gas are associated with a predominantly fractured-cavernous-type reservoir are the middle East, the North Caucasus, the Caspian basin, Siberia.
Deposits in reservoirs fractured-cavernous-type reservoir are difficult built. The effectiveness of traditional search methods such occurrences are much lower than deposits with traditional porous type reservoirs. The reason is that in reservoirs with fractured-cavernous reservoir, oil is distributed in a more complex law than in tanks with porous collector. Migration and accumulation of oil in such reservoirs is controlled by zones of fracturing. The geometry of reflecting horizons (reflectors), which is the main result of the traditional processing of seismic data CDP for the study of cavernous fractured reservoir is totally inadequate. Fracture zones do not form seismic reflections, and are sources of scattered (diffracted) waves. Scattered waves are 1-2 orders of magnitude less intense in amplitude than reflected, the study of cavernous fractured reservoirs, respectively, are very intense waves-interference.
In АО «Технологии обратных задач» is developed and the method of processing and interpretation of seismic data standard, called the method prestigiou migration pre-stack CSP(Common Scattering Point). The method allows to predict the reservoirs with fissured cavernous collector allocated from the total wave field scattered waves. It implements a strict solution of the inverse problem of the complete separation of the wave field reflected and scattered components. Mathematically correct division of the waves allows us to visualize the invisible with a standard seismic scattering elements.
The standard data processing of 3D seismic survey by the method of CSP is implemented in the form of a complete graph on a specialized computer cluster with 12 Teraflops performance and memory 8 terabytes.
The CSP method has a high resolution. In figure 1, upper part shows the model anticlinal folds used to calculate synthetic seismic data. The model consists of three layers. The average layer thickness of 50 m, contains a circular inclusion with a diameter of 40 m. Numerical calculations show that the amplitude scattered by inclusions of waves of smaller amplitudes of the reflected waves from 50 (left inclusion) to 250 (right inclusion) times. On time section obtained by the standard technology prestigiou temporary migration (middle part of the figure), there are only a reflecting boundary, and the scattering elements are completely invisible. However, refractors are very visible on the cut, obtained using CSP (the lower part of the figure).
FractureCSP method allows to solve the following tasks:
- Prediction of fracture zones, decompression and disintegration, which may contain hydrocarbon deposits.
- Geometrization of deposits of fissure-type reservoir for reserve estimation and valuation of hydrocarbon resources.
- Classification explosive breach into two classes – permeable fractures and faults-screens.
- Detection of faults with no vertical displacement, the selection of which sections of the reflected waves is questionable.
- Detection of inhomogeneities in the geological section, which are associated with zones of potential complications of drilling wells.
As examples of the results of processing and interpretation of 3D seismic prospecting by the method of CSP for the three fields of the West Siberian oil and gas province (OGP).
Field No. 1
Oil deposits are concentrated in carbonate basement rocks of Devonian age and are confined to its upper part the reservoir of fractured-cavernous. Deposits of massive and structural plan are not controlled. Capacitive-filtration properties of the reservoir change sharply in the area and on the incision. Maximum oil inflows are obtained from the organogenic limestones. The predicted thickness of the reservoir varies from 0 to 100 meters.
The processing of seismic material was prepared Cuba of Cuba of reflectors and refractors (Fig. 2)
In Cuba refractors red color represents productive wells and dry white. As can be seen, and Cuba, and on the section (Fig. 3) productive wells are located in the range of elevated values of amplitude diffractors created reservoirs with fractured-cavernous-type reservoir.
For the interval of occurrence of productive rocks of the Paleozoic a map of diffractors. The zones of high amplitude diffractors are interpreted as reservoirs of fractured-cavernous-type reservoir (Fig. 4).
Analysis of the map shows that the productive wells are located in the range of elevated values of amplitude diffractors (in the areas of distribution manifold) and dry wells in areas with low values in areas of lack of manifold.
Field No. 2
Oil deposits are concentrated in carbonate basement rocks of Devonian age and are confined to its upper part. In the roof of the basement in the most elevated areas of a weathering crust. In the weathering crust of the reservoir fractured-porous. In unaltered rocks reservoir of fractured-cavernous. The thickness of the reservoir varies from 0 to 200 metres. Deposits structural and lithological. In the left part of figure 3 shows the combined of Cuba CSP reflectors and refractors. In the right part of the map prediction of reservoir distribution.
Field No. 3
Oil deposits are concentrated in the Bazhenov formation, composed of bituminous clays with carbonate and siliceous layers. Oil resources in the Bazhenov formation (West Siberia) are estimated by different researchers from 600 million to 30 billion tons At the present time there are more than 70 fields with commercial reserves of oil in the Bazhenov formation, but their discoveries are rather random. In one of these fields was used CSP technology.
A Deposit in the Central part of Western Siberia was discovered in 1965, when the sediments of the Bazhenov formation had been received gushing flow of oil at a rate of more than 600 m3/day. In this field, was first proven the productivity of fractured-cavernous reservoirs of the Bazhenov formation.
Today at the field, drilled over 200 wells, however, the results of the interpretation of the reflected waves, 3D seismic and well survey did not allow us to identify patterns of reservoir distribution nor square, nor and cut.
Figure 4 shows the map of the amplitudes of the refractors for the Bazhenov horizon of the studied field. The high values of the diffractors are formed in open fluid-filled cracks that have low acoustic impedance relative to the host rocks. As no water from the wells of Western Siberia, the Bazhenov formation is not received inflows of formation water, all areas of high values diffractors identifitseerida as oil deposits. Low values of refractors characterize the zone of absence of cracks. The boundary values of the refractors for the Bazhenov reservoir that separates the manifold from not manifold, determined by the results of tests of wells within the study area. Figure 5 shows the time sections of the diffractors (left) and reflectors (right).
From figure 4 it is seen that productive wells in most cases (60%) are located within anomalies with high values of diffractors (interpreted as zones of open fractures), but individual wells are located outside of them. For further interpretation, were used the fault-block model of the reservoir, which was built on the results of the joint interpretation as the cube of refractors and reflector.
Within deposits the faults cut through not only the deposits of the Bazhenov formation, but the overlying and the underlying rocks-screens. In the case of destruction of the upper screen, the oil migrates into the Sandstone of the lower Cretaceous. If destroyed the bottom screen and oil reservoir has abnormally high reservoir pressure (which is characteristic of the Bazhenov formation), the oil migrates into the underlying sandstones of the middle Jurassic. At the same time, increased the scattering properties are preserved, however, in these cases high values of diffractors possess both overlying and underlying rocks. Based on these considerations k-means using the cards refractors in the Bazhenov formation at the upstream and downstream horizons and map structural plan was a cluster analysis is performed. The result is presented in figure 6. According to the results of cluster analysis of the whole investigated territory is divided into ten classes, which are combined into three zones. The first area is related to land highly promising, second – and third-promising – unpromising. Percentages are of productive wells in promising areas on this map was 80%, significantly increasing the reliability of the forecast. Based on the maps identified prospective areas for drilling new wells (Fig.6).
Mapping of cavernous fractured reservoir based on the method of CSP to radically change approaches to the assessment of reserves and resources as on the already developed areas and on razvedenii.
The CSP method has been tested for synthetic and field materials and showed high effectiveness of fracture and fracture-cavernous reservoirs in carbonate, clay and igneous rocks.
Technology processed more than 15 thousand linear kilometers of seismic profiles 2D and about 6,000 sq km area-surveys of 50 3D fields.
Geography of works:
- West Siberian NGP
- East Siberian NGP
- Volgo-Ural NGP
- The Timan-Pechora NGP
- Caspian NGP
- Barents sea