Oil and Gas Vertical, No.10 2012
Artur Tissen, Sales and Marketing Director, GEOTECH Holding, Cand. Sc. (Eng.).
Rapid technical progress requires ever more fuel resources. By the way, small and relatively small shallow fields gradually deplete, and the exploration of new oil and gas deposits is significantly more challenging in terms of depth, surface conditions, and geological structure. Seismic exploration has an important role to play in the resolution of these complicating issues.
Seismic exploration is conducted in a phased way during exploration and development of oil- and gas fields.
Regional comprehensive exploration is conducted at the first stage to study the structure of the Earth’s crust and identify prospective zones for the exploration of oil and gas. These operations in Russia almost came to a standstill in the beginning of Perestroika and were re-started approximately 7-8 years ago. Such services are commissioned by the government. Geological and geophysical research institutes play a significant role in their scientific justification (SNIIGIMS, VNIGNI, VNIIGeofizika, etc.), while practical implementation is executed by different exploration companies (gravimetric, magnetic, geochemistry, seismic, resistivity, and airborne surveys). GEOTECH Holding is one of the largest contractors with the Federal Agency Rosnedra, especially in Western and Eastern Siberia. Conducting seismic exploration at this stage is characterized by the remoteness of the sites and large surveyed areas (several hundred kilometers). For this reason, the structure of seismic crews and operational costs significantly differ from similar operations at other stages.
The results of the surveys significantly impact the initial cost of the lots subsequently offered at auctions for the right to use them for geological exploration and the production of hydrocarbons.
2D prospecting seismic surveys are conducted at the second stage. E&A drilling recommendations are provided based on the results of these surveys. Usually, such surveys are conducted on allocated fields under contract with field operators. The density of seismic surveys per 1 sq.km of license area significantly increases at this stage. Often, large oil companies (TNK-BP, NOVATEK) combine the second stage with the third one and conduct detailed 3D seismic surveys at once. On the other hand, some small investment companies – subsoil users---due to the fact that they are highly dependent on current oil prices postpone the fulfillment of license agreements for years. GEOTECH Holding, with its highly trained geologists and geophysicists and large seismic database practically in all regions of Russia, provide support to small subsoil users in the preparation of a geological and exploration program for the study of the structure of the license area. Usually, such services are provided for free to demonstrate the capabilities of the company and establish further successful cooperation.
A detailed 3D seismic exploration is conducted at the third stage. The results of these surveys are used to detail the contours of fields and plan development, and reserves estimations are finalized. Underestimating the need for a sufficiently detailed seismic exploration at this stage can result in serious economic mistakes in field development planning. Recently, oil companies have been better at realizing the need for high-resolution seismic surveys for field development planning. This has manifested itself in the following:
- Creation of divisions (research and information centers) inside oil and gas companies that include seismic exploration staff who act as direct and highly skilled managers of seismic surveys;
- Significant increase in the resolution of seismic projects; and
- Tightened requirements for compliance with procedure and quality requirements.
Figure1 provides examples of growth in the number of active channels of seismic stations in recent years. As seen on the figure, the amount of information obtained from the registration of one physical observation in Russia has almost doubled in the last 4 years.
Given the fact that seismic exploration costs currently make up a small share of the cost of each barrel of oil produced, the additional seismic exploration costs fully justify themselves. Customers at the third stage are companies that develop fields, i.e., well-known oil and gas companies such as Gazprom, Surgutneftegaz, GazpromNeft, Rosneft and others.
Additional high-resolution seismic surveys can be conducted at the fourth stage for the evaluation of hard-to-access reserves. The pilot 3D seismic project of TNK-BP in Northern Vietnam can be used as example.
This is what Andrey Lazeev had to say: “Before the end of this (2012) year, a pilot 3D seismic project will be conducted on an area of 130 sq.km for an appraisal of the reserves. TNK-BP applies a cutting-edge data processing technology – seismic inversion. This allows us to create a detailed picture of the formation structure, clearly define the quality of the reservoir, and to identify even small hydrocarbon deposits.
If the Severnoye Varyogan experience is successful, the reserves evaluation technology can be rolled out across the entire company within the framework of the TNK-BP West Siberia Gas Cap Program. 3D seismic survey experience helps us detail the structure of the geological targets of the field. We plan to drill a hole down to the weathering crust - deposits are estimated at a depth of over 3,000 meters. We will take the core and conduct a detailed study of the structural tectonic model. Implementation of such a project will allow to open a gas era in the history of the Severo-Varyogan field and will provide new empetus for its development." IA Mangazeya, 13.02.12.
It is necessary to note that these field surveys are conducted by OJSC Integra-Geofizika, which is one of the largest subsidiaries of GEOTECH Holding.
4D seismic is conducted at the fifth stage to control field development. Unfortunately, such services are not widely used in Russia. This can be explained by the geological structure of the majority of Russian fields and rather non-definitive understanding of expected results. At the same time, these operations have demonstrated a high level of efficiency in the characterization of fracturing and OGC surveillance at oil- and gas fields.
As shown above, seismic surveys during exploration, appraisal, and development of oil- and gas fields is highly relevant today. Saving on exploration can result in a wrong evaluation of the structure of the deposit, the development of a non-optimum development scheme, resulting in significant economic losses. It is very important to conduct a high-quality exploration at all stages, because it can significantly reduce subsequent field development costs.
Costs can also be contained through the application of a comprehensive approach even if all exploration activities are conducted by the same company. In such a case, it is possible to ensure a coordinated and efficient operating mode, which can allow the customer to enjoy significant savings on exploration. GEOTECH Holding can offer efficient services at any of the above stages, meeting any of a customer's requirements.