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Confirmability of geophysical data by drilling and well production testing in the territory of Tatneft’s activities

UDK: 550.8:553.98(470.41)
DOI: 10.24887/0028-2448-2018-7-12-14
Key words: confirmability, seismic survey, efficiency, oil, geological exploration activities, discrepancy, well logging, success rate
Authors: R.S. Khisamov (TATNEFT PJSC, RF, Almetyevsk), V.G. Bazarevskaya (TatNIPIneft, RF, Bugulma), А.P. Bachkov (TATNEFT PJSC, RF, Almetyevsk), А.G. Ziyatdinov (TatNIPIneft, RF, Bugulma), G.А. Lykov (TatNIPIneft, RF, Bugulma)

Under conditions of high degree of exploration maturity and extensive development of hydrocarbon resources in the Republic of Tatarstan there is an urgent need for application and combination of enabling technologies for geological prospecting and exploration, such as areal and downhole geophysical methods. Geophysical survey, in addition to drilling, is the primary data acquisition tool at all phases and stages of geological exploration, which provides insight into the geological structure and evaluates potential of hydrocarbon discoveries across exploration areas. Success of geological exploration activities depends primarily on the quality and accuracy of geophysical data interpretations. Despite obvious advantages of individual geophysical methods, it is impractical to rely on one technology. To make a well-argued decision on further exploration activities a competent geologist should analyze all available geological and geophysical data (conventional core studies, SCAL, well logging, seismic survey, other geophysical survey methods, well tests and so on). Two- and three-dimensional CDP seismic surveys have become firmly established as the main geophysical method used to locate wildcat and exploratory wells. Almost the entire territory of the Republic of Tatarstan is covered by 2D and 3D CDP seismic activities. Efficiency of seismic surveys is evaluated based on exploration drilling results. These are degree to which reflector elevations below sea level obtained fr om seismic data can be confirmed by deep hole drilling data and closeness of agreement with data obtained from wells that yielded oil during production testing. In 2003-2017, discrepancy between 2D CDP seismic results and drilling data was estimated at ±8.9 m for Reflector V, ±8.4 m for Reflector U and ±11.2 m for Reflector D. Out of 46 wells drilled based on 2D CDP seismic data, 37 wells confirmed presence of oil (oil prospecting efficiency exceeded 80%). With 3D CDP seismic method resolution of as high as 5 meters, average data discrepancy for Reflector V made ±3.2 m, for Reflector U ±5.0 m and ±9.4 m for Reflector D. Out of 29 wells drilled based on 3D CDP seismic survey data, 25 wells confirmed presence of oil (oil prospecting efficiency is 93 % without account of two wells at the stage of production testing). In view of high degree of exploration maturity and noticeable depletion of active oil reserves, the majority of geological prospecting efforts over the past years have been focused on unconventional reserves. Tatneft has been awarded a license block wh ere the Company has established a scientific (Domanic) polygon aimed at creation of technologies for prospecting and development of Domanic deposits. Two license blocks have been awarded to create polygons aimed at development and pilot testing of technologies for heavy oil prospecting and production from shallow (10 m) terrigenous reservoirs and Permian carbonate rocks.

Under conditions of high degree of exploration maturity and extensive development of hydrocarbon resources in the Republic of Tatarstan there is an urgent need for application and combination of enabling technologies for geological prospecting and exploration, such as areal and downhole geophysical methods. Geophysical survey, in addition to drilling, is the primary data acquisition tool at all phases and stages of geological exploration, which provides insight into the geological structure and evaluates potential of hydrocarbon discoveries across exploration areas. Success of geological exploration activities depends primarily on the quality and accuracy of geophysical data interpretations. Despite obvious advantages of individual geophysical methods, it is impractical to rely on one technology. To make a well-argued decision on further exploration activities a competent geologist should analyze all available geological and geophysical data (conventional core studies, SCAL, well logging, seismic survey, other geophysical survey methods, well tests and so on). Two- and three-dimensional CDP seismic surveys have become firmly established as the main geophysical method used to locate wildcat and exploratory wells. Almost the entire territory of the Republic of Tatarstan is covered by 2D and 3D CDP seismic activities. Efficiency of seismic surveys is evaluated based on exploration drilling results. These are degree to which reflector elevations below sea level obtained fr om seismic data can be confirmed by deep hole drilling data and closeness of agreement with data obtained from wells that yielded oil during production testing. In 2003-2017, discrepancy between 2D CDP seismic results and drilling data was estimated at ±8.9 m for Reflector V, ±8.4 m for Reflector U and ±11.2 m for Reflector D. Out of 46 wells drilled based on 2D CDP seismic data, 37 wells confirmed presence of oil (oil prospecting efficiency exceeded 80%). With 3D CDP seismic method resolution of as high as 5 meters, average data discrepancy for Reflector V made ±3.2 m, for Reflector U ±5.0 m and ±9.4 m for Reflector D. Out of 29 wells drilled based on 3D CDP seismic survey data, 25 wells confirmed presence of oil (oil prospecting efficiency is 93 % without account of two wells at the stage of production testing). In view of high degree of exploration maturity and noticeable depletion of active oil reserves, the majority of geological prospecting efforts over the past years have been focused on unconventional reserves. Tatneft has been awarded a license block wh ere the Company has established a scientific (Domanic) polygon aimed at creation of technologies for prospecting and development of Domanic deposits. Two license blocks have been awarded to create polygons aimed at development and pilot testing of technologies for heavy oil prospecting and production from shallow (10 m) terrigenous reservoirs and Permian carbonate rocks.



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