NMR Application for Development Optimizing in Shaly Reservoirs

By

Pavel Syngaevsky¹, Sergey F Khafizov²

(1) Numar (A Halliburton Company), Houston, TX (2) TNK (Tyumen Oil Company), Moscow, Russia

 Samotlor Field - one of the biggest oil fields in the World, was discovered in 1965 and put on production in 1969. Despite the big amount of core recovered during exploration and early development stages many questions related to petrophysical characterization and geological models still go unanswered. Particularly this is the case with the reservoirs of ÀÂ1(1-3) group which are characterized by a high level of heterogeneity, that is recognized at two scales. All that turns the pay zones with sedimentary structures described as "Ruabchek" into extremely complex target for interpretation. In 2000-2001 an interpretation of new cores, magnetic-resonance imaging logs and re-interpretation of NMR formation fluid measurements were performed. The main goal was to identify and characterize production potential of pay zones formed under various depositional sequences of tidal plains and deltas, and optimize wells completion in shaly formations.

The possibility of successful measurements of the following parameters: current and residual oil saturation, total and affective porosity, permeability and shaliness was proven based on processing of multi-frequency NMR data. Combined interpretation of MRIL materials, core data and modern depositional environments description allows us to identify and quantitatively characterize the following facies: lagoon tidal flats, tidal sands, low and high tidal plains, coastal bays, point bars and various channels. For the first time in West Siberia Basin TNK applied MRIL-C/tp for 78-degree borehole. Data obtained during one pass gave a sufficient amount of petrophysical information about structure and reservoir properties of several targets.