Practical experience of re-estimating hydrocarbons of larger fields in West Siberia being repeated every 4-6 years indicates that geologic models of accumulations are constantly getting complicated. Information on fields is added as a result of new drilling and field geophysical surveys, as well as a result of reprocessing and integrated interpretation of old materials of seismic exploration and field geophysical research, earlier conducted in the field. New technologies of handling raw seismic data allow extraction of significantly more important geologic information which provides insight into facies environments where productive strata have been formed, including in particular the role of channel deposits in the formation of traps containing oil and gas accumulations. Application of new methods and techniques for interpreting G&G materials and geologic modeling allows satisfactory “tying” of well test results, which earlier looked contradictory. One of the key challenges of geomodeling is the determination of geological nature and location of seals confining the accumulations. Often, the existence of such seals was deemed rather evident and indirectly confirmed by well test data. Yet, it was not always possible to explain the character of sealing, or locate the accumulation boundary in plan view, based on the existing G&G information. Thus, a conditional line (zone) was assumed for a seal. With such approach there is a possibility of errors in estimating reserves and significant geologic risks while drilling appraisal and development wells.
The article, based on analysis of re-processing and integrated interpretation of all available G&G data, establishes the presence of abandoned paleochannels of meandering rivers mainly filled with clays, in productive layers of Beregovoye field. In plan view, they represent narrow tortuous bodies - seals controlling the accumulations. Sealing effect of paleochannels is expressed through significant difference in hydrocarbons – water contacts, and phase difference in the adjacent reservoirs. Lithologic seals picked with using modern depositional analogs and seismic attribute maps allowed a new geologic model of the field to be validated, confidence of hydrocarbons reserves estimate to be improved, subsurface risks of development drilling to be mitigated.
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