Trap magmatism is a typical feature of the ancient platforms. In the central parts of the Siberian platform magmatic formations make up 3% out of sedimentary cover. Basically, magmatic formations are represented by sills, less often – by dikes. On the area of the Srednebotuobinskoye field intrusions occur in the deposits of the Yuregin, Nizhnetolbachan, Verkhnetolbachan, and Olekminsk formations. The intrusions thickness changes from 95 up to 112 m. By the melt of the sedimentary rocks the fracture zones are generated. The intensive mud losses are often caused by such zones existence. The intrusive formations not only have a significant impact on the generation and accumulation of hydrocarbons, but also cause certain risks at various stages of the field exploration, including seismic data processing and interpretation, drilling and field development. To reduce the risks of the influence of intrusions on the field development, it is recommended to implement an integrated approach to their study, based on the analysis of all available geological and geophysical information on the area of interests. The spatial location and the shape of the intrusions have correlation with anomaly values of the gravity and magnetic fields. More detailed identification of trap intrusions in terms of stratigraphy is based on seismic and well data. The interpretation of the intrusions top and bottom allows to achieve more correct structure surfaces in the target zones. The results of the near-field transient electromagnetic sounding the results allow to determine the resistivity in the intervals of traps. Using wells drilling data we ranked the zones in terms of the degree of mud loss. The minimum resistivity values areas are more permeable and, as a result, have a greater risk of lost circulation. Based on the drilling results the conceptual geologic model is generated, which explains main reasons of the mud loss. Taking into account this model the ideas for risk minimization during drilling are suggested. Using an integrated data set of seismic, electromagnetics and drilling a qualitative predictive risk map during field development is built.
References
1. Sysoev A.P., Prikladnye zadachi kompensatsii neodnorodnosti verkhney chasti razreza pri obrabotke i interpretatsii seysmicheskikh dannykh (Applied problems of compensation of heterogeneity of the upper part of the section during processing and interpretation of seismic data), Novosibirsk: Publ. of IPGG SB RAS, 2011, р. 88.
2. Geologiya nefti i gaza Sibirskoy platformy (Oil and Gas Geology of the Siberian Platform): edited by Kontorovich A.E., Surkov V.S., Trofimuk A.A., Moscow: Nedra Publ., 1981, 552 p.
