Some Results and Ideas of the Probable Present-Day Deep Oil Inflow Analyses

Ravil Ibatullin¹, Rais Khisamov², and Ivan Glumov^3
1TatNIPIneft, Bugulma, Russia
²TATNEFT, Almetyevsk, Russia
³TatNIPIneft, Bugulma, Russia

In Tatarstan, one of the Russian oil-bearing regions, sedimentary deposits are underlain by the Archean and Proterozoic crystalline basement at a depth of 1,900-2,000 m subsea. Productive intervals in the Romashkinskoye oil field are found throughout the sedimentary section, from 750 m to 1,900 m. Analysis of geologic and production data from a number of producing areas, as well as compositional and physico-chemical analyses of the Devonian crude samples showed a number of anomalous results.
Statistically significant groups of wells with anomalous production performance have been identified, the following parameters taken as a reference: - unenforced transition from steady decline to steady increase of oil production rates; - cumulative oil production per one well passed the 500,000 tons mark, vs. the average 100,000 tons; - steady water-oil ratio lower than the average.
A definite relationship between the depth of water-oil contact and distance to the boundary of the Devonian deposits controlled by the ancient Altunino-Shunakskian fault has been established.
Statistically significant difference in oil properties between the anomalous and base well groups has been found, for example, it has been shown that oils from the anomalous well group in the Minnibaevskaya area of the Romashkinskoye field are characterized by less gravity and viscosity.
Proceeding from the detailed analysis of oil properties, geologic and production data, we may conclude that today we may be witnessing local deep inflow of newly generated hydrocarbons from the crystalline basement into the Romashkinskoye field. This process is very slow and can't be precisely localized but its presence can be used for explanation of the origin of the geological and fluidal parameters' distribution of oil field deposits.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece