Core Analysis Helps Model Bazhenov Formation Deposits

The “Shale Revolution” turned Russian oil producers’ attention to Bazhenov suite resources, estimated by various industry sources to range from 2 to 22 billion tons. However, in order to better understand the prospects of developing Bazhenov formations, Russian oil companies need a more detailed examination of oil occurrence in these reservoirs. The key differences between Russia’s Bazhenov and the U.S. Bakken formations are the thickness of reservoir layers and their position within the strata, Varvara Nemova, head of research group on shale formations productivity at the All-Russian Research Geological Oil Institute (VNIGNI), said in her speech at the November 2012 meeting of the SPE’s Moscow Section. At the time, research suggested that the relevant U.S. production technology could be used in Russia, but it had to be adapted to work with dissociated reservoirs, scattered across the section of the Bazhenov formation. 

VNIGNI continues the research on productivity of shale formations by studying core samples. “We’ve achieved a breakthrough in our studies linking interpretation of seismic data with the core research,” Nemova told OGE after delivering a presentation at the March 11 SPE meeting in Moscow. “This year, we have worked on several projects that entailed sizeable interpretation of seismic data and the testing of a huge number of interconnections. On the basis of dependencies identified in cores, we produced quality models that have already been confirmed by drilling,” added Nemova, commenting on the new results of research.

VNIGNI’s research experience suggests that extrapolation of knowledge about reservoir modeling of the most studied fields in West Siberia cannot be used for qualitative modeling of Bazhenov formations. Here, core studies provide invaluable assistance in creating high-quality models of these deposits. Core study can provide a detailed insight into lithological variability of the layers, reservoir structure and the difference between a container rock and deposit layer at a specific field.

According to Nemova, over a long period of time the abnormally high reservoir pressure in Bazhenov formation thwarted the scientists’ plans to study the selected core due to its very poor condition. As a result, the research was marked by a great deal of uncertainty. In recent years the situation has changed – a number of production companies started to eye up the Bazhenov formation. “It is important that new wells are drilled for downhole logging that targets selection of flushing intervals, for sampling fine isolated core, for complex laboratory tests on this core, for study of various interpretation methods of data and seismic,” says Nemova. 

She noted that an average field slated for development of the Bazhenov formation usually features two to three wells drilled in the past five years, in addition to plenty of old exploration wells. The new wells are equipped with front-end well logging tools and produce core samples from almost the entire range of the Bazhenov suite. “Our task is to use the data from these wells to study the Bazhenov deposits, and then attempt to interpret the less representative data on the old wells,” explains the scientist.