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Martinov, M E (TNK-Nyagan) | Kozlov, A V (TNK-Nyagan) | Leskin, F Y (TNK-Nyagan) | Filimonov, A Y (Schlumberger) | Ezersky, D M (Schlumberger) | Egorov, S S (Schlumberger) | Blinov, V A (Schlumberger) | Weinheber, P.. (Schlumberger)
Abstract The Vikulovskaya formation of Western Siberia is characterized by thinly-bedded, sand-shale layers. The vertical thickness of these layers ranges from a few millimeters to a few centimeters. This layered feature presents well known challenges for petrophysical analysis from standard logging suite data. These layers are typically beyond the vertical resolution of the standard tools so net-to-gross cannot be derived directly. The shale layers suppress the resistivity readings in the oil strata and the resulting low resistivity contrast makes it difficult to determine the oil-water contact. Finally, the ability to resolve the individual sand layers makes it impossible to accurately determine their water saturation. In this paper we discuss how these challenges were surmounted when performing a petrophysical evaluation of a dataset acquired in a recently drilled well in the Krasnoleninskoe field. This dataset consisted of full bore core and traditional ‘triple combo’ data. Additionally, we had NMR data, high resolution micro-imager data and formation tester pressure and fluid analysis data. By combining the measurements from the traditional tools with the resolution of the micro-imager data we were able estimate the desired petrophysical properties of the thinly-bedded layers individually. By using tools with different physics we were able to realize an independent quality control of the interpretation: stationary NMR measurements were used as porosity and irreducible water saturation reference, and formation tester data of direct inflow composition were used as a reference for fluid saturations. As a final check on our method we performed a digital integration of core and micro-imager data to validate our findings. The resultant workflow is concisely explained such that it can be easily applied to similar evaluation environments.
Platunov, A.. (OJSC Rosneft Oil Company) | Martynov, M.. (OJSC Rosneft Oil Company) | Nikolaev, M.. (OJSC Rosneft Oil Company) | Leskin, F.. (OJSC Rosneft Oil Company) | Davidenko, I.. (OJSC Rosneft Oil Company)
Abstract This paper is based on study of formations in Bazhenov and Tyumenskoe horizons of Em-Yoga field Krasnoleninsky arch West Siberia with the aim of defining the geomechanical concepts of studied area. Hydrocarbon production from Bazhenov and Tyumenskoe formations in West Siberia is actually established through number of pilot wells with production testing. Economic profitability of producing wells depends on the efficiency of hydraulic fracturing in cases where the technology is predefined by reservoir development project. This article describes the principles and prerequisites of hydraulic fracturing mechanics under geomechanical conditions of the studied rocks. Tyumenskoe and Bazhenov formations are dated to Upper and Middle Jurassic geological time. Geological depositional environment and posterior transformations in time have created specific conditions for rock geomechanics. Rock mechanics in studied formations practically predetermines the concept of how rock is fractured. This work presumes basis for typification and description of fractures occurred naturally and created as a result of hydraulic fracturing and how those interfere with each other. This work is stand on the accumulated results of the ongoing study and actual data from producing wells in Em-Yoga field Krasnoleninsky arch West Siberia. The Jurassic rocks studied in this article are stratigraphically divided into formations of Tyumenskoe, Abalak and Bazhenov horizons. Enacted stratigraphic cross-sectional classification describes the formations of Tyumenskoe horizon as porous rock, Abalak horizon as cavernous-porous naturally fractured and Bazhenov as naturally fractured and micro-porous types of rock.
Abstract Slugs-fracs is one of new-to-field approaches which changed the conditions of wells for fracturing increasing the number of candidates in Kamennoe field Western Siberia. Placing fracturing jobs by slugs of proppant pumped in linear gel successfully implemented in stimulating pay zones in near water intervals with small stress contrast between zones and barriers. A few technical specifics had been used to contribute the success of this methodology such as earlier pumping with near matrix rate to allow more fluid filtration ahead of the main proppant stages before fracture is fully formed. Proppant setting according to Stokes law and dune effects theory were evaluated and considered for design strategy. The slugs-fracs allowed pumping regardless of the wellbore deviation and height of perforated intervals. Post-fracturing results from 120 wells were used for analysis. Significant decrease in initial water cut and sustainable oil production were reported. First slugs-fracs were introduced in the beginning of 2010 and in following 2 years more than 200 hundreds jobs have been pumped across the field. This allowed to drill spots of the field that were previously suspended as result of ineffective fracturing treatments mostly due to high risk of fracture breaking down the water zones.