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The Tyumen formation is the main hydrocarbon-saturated layer of the Krasnoleninskoe oil and gas condensate field located in Western Siberia. This formation is characterized by significantly changing structural dips and represented as thin, interbedded shale and sandstone layers. Such a formation structure complicates the real-time evaluation of formation properties, well correlation and proper well placement. This paper presents the results of horizontal well drilling at the Krasnoleninskoe field using advanced resistivity logging technology.
Advanced resistivity logging technology is used in field operations for various applications. This technology includes logging-while-drilling (LWD), a deep-azimuthal resistivity tool, and sophisticated data interpretation software. The tool performs multi-component, multi-spacing and multi-frequency measurements downhole. The measurement set can be configured individually for each particular geology and application type to ensure effective operations. Next, these measurements are transmitted to the surface, where high-performance multi-parametric inversion recovers formation parameters of interest in real-time. The inversion software enables the processing of any combination of tool measurements and is based on a 1D layer-cake model with an arbitrary number of layers to operate with complex multi-layer formations.
Besides the complex laminated structure of the Tyumen formation, an additional challenge is the low resistivity contrast between the shale and sandstone interlayers. This factor is typical for many West-Siberian fields; it complicates the resolution of interlayers and degrades the evaluation accuracy of their parameters.
To overcome these challenges, a set of deep-azimuthal resistivity tool measurements, suitable to resolve thinly laminated formations, was identified and transmitted uphole while drilling. Real-time inversion was performed in a user-controlled mode to ensure the careful tracking of geology changes. These results enabled operational geologists to monitor the formation properties during the drilling.
Data inversion software ensured the accurate evaluation of formation properties and structural dips estimation in complex conditions of the Krasnoleninskoe field. Structural dips recovered by inversion significantly differed from values observed at offset wells, i.e., 5 to 12 degrees, instead of 0 to 2 degrees. A perfect match between the measured and synthetic resistivity data confirmed high confidence of inversion results. Moreover, there was a strong correlation between the structural dip angles estimated from resistivity data and derived from LWD natural gamma-ray (GR) image. Many of shale and sandstone layers observed in the GR curves were resolved by resistivity inversion.
The depth of the remote layer detection was estimated during the job; it enabled geoscientists to delineate the reservoir volume that contributed to the tool measurements.
This case study describes the first application of advanced resistivity logging technology in a complex laminated formation of the Krasnoleninskoe field. This technology enables the resolution of thin interlayers, evaluation of their properties and estimation of structural dips in real time. These parameters are important for proper well placement and accurate petrophysical interpretation. The presented technology is able to increase the efficiency of oil recovery in the complex laminated formations of the Russian West-Siberian fields.
For the past several years, cores and image logs have been utilized extensively by petroleum geologists to solve many exploration and development related challenges. However, maximum utilization of these data has not been achieved due to lack of availability of advanced computation techniques and methodology. Because of the limited utilization, the need for these very important logging data may be questioned, particularly in this highly cost-sensitive period of oil industry. In this study, different advanced techniques have been systematically demonstrated to display the maximum utilization of this logging data for oil exploration and development activity.
Much critical information, such as rock texture, thin laminations, formation dip, and reservoir heterogeneity, cannot be clearly understood using conventional log data because of very low resolution. INPEX geologists decided to conduct a detailed analysis on existing core samples and image log data to identify and understand heterogeneous reservoir properties that will be critical information for future field development.
At the beginning of the workflow, raw data from the field were carefully processed though accurate depth matching and applying the most accurate processing parameters. After initial processing of field data, different advanced techniques were applied to achieve the maximum amount of high-resolution information from these data utilizing Techlog*wellbore software platform:
To achieve the most information from core photography data, core slab photographs were converted to digital array data through the latest technique of core array creation. First, core photographs(whole core four-direction photograph and slab photograph) were loaded into the Techlog platform, and core photos were converted to red, green, blue, and grayscale 2D arrays.
*Mark of Schlumberger