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Abstract 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.
Sviridov, Mikhail (Baker Hughes) | Belyaeva, Olga (Salym Petroleum Development) | Podberezhnyy, Maxim (Salym Petroleum Development) | Zverev, Vladimir (Salym Petroleum Development) | Mosin, Anton (Baker Hughes) | Antonov, Yuriy (Baker Hughes)
Summary The West Salym is a Salym Petroleum Development oil field in the Khanty-Mansi region, 120 km southwest of Surgut, Russia. The West Salym oil field was discovered in 1987 and was brought on stream in 2004. The reservoirs vary from fluvial/deltaic to shallow marine deposits. Primary development of the central area of West Salym Field is complete, but the field edges remain undeveloped and potentially attractive. The edges of the field are presented by a mouth bar and characterized by significant structural formation changes, including unknown formation dips and local carbonate concretions and stripes. The sand thickness of the target layer is 15 m, with a minimum oil height of 1 m, which is caused by structural dips and nearby oil/water contact (OWC). These conditions make it difficult to drain the area with geometrically placed wells within the hydrocarbon-saturated layer using well correlation and 3D seismic-interpretation results. Another challenge is the low resistivity contrast between the shale, oil-bearing, and water-bearing layers. This poor contrast complicates the evaluation of reservoir properties and the ability to distinguish different fluid saturations. Two horizontal wells (500 m each) were drilled for the first time in West Salym Field to evaluate capabilities of modern reservoir-navigation technology using deep-azimuthal resistivity technology and advanced data-interpretation software. Drilling of both horizontal wells was improved with a standard wireline logging suite (gamma ray, spontaneous potential, resistivity, density, and neutron) and pressure-testing results available from pilot holes. Logging-while-drilling (LWD) deep-azimuthal resistivity technology has been used in field development, contributing to proactive reservoir navigation. This technology provides input for interpreting an extensive set of multicomponent, multispacing, and multifrequency measurements. These data are usually sufficient to resolve the formation properties in the vicinity of several meters from the wellbore and to adjust the direction of the well trajectory. However, because of time restrictions, very simple resistivity models and only a subset of the data are often used for real-time interpretation. Moreover, the structure of the data subset is often predefined to provide the maximum depth of investigation, neglecting the resolution quality of the formation parameters. In some fields, it can lead to increased uncertainties during reservoir navigation. The data-interpretation software mentioned in this paper has excellent performance and enables real-time processing of the full set of downhole measurements derived from multilayered formation models. This case highlights the first use of this software application in the Russian Federation. The software is dependent on the method of the most-probable parameter combination, and it maintains an optimal balance between the information recovered from the measured data and all available a priori knowledge about the formation structure. The ability to accurately involve a priori information enhances the capability to resolve layers with low resistivity contrasts. Moreover, the inversion software is user-guided, enabling precise monitoring of lateral and vertical changes in the geology. The data-inversion software ensured successful reservoir navigation in the challenging conditions of the West Salym Field. All steering decisions were made according to a consistent and reliable multilayered formation resistivity model that was constructed in real time during drilling. A good net/gross ratio was achieved of approximately 75% for one well and 50% for the other. Post-drilling analysis showed that geometric drilling without reservoir-navigation technology would lower the net/gross ratio to less than 40%.
Ronald, Andy (BP Exploration Ltd) | Rabinovich, Michael (BP Exploration Ltd) | Ward, Mary (BP Exploration Ltd) | Gordon, Miriam (BP Exploration Ltd) | Bacon, Robert (BP Exploration Ltd) | Tilsley-Baker, Richard (Baker Hughes, a GE company) | Wharton, Paul N. (Baker Hughes, a GE company) | Mosin, Anton (Baker Hughes, a GE company) | Martakov, Sergey (Baker Hughes, a GE company)
ABSTRACT The benefits of extra deep azimuthal reading logging-while-drilling (LWD) resistivity tools have been well documented previously in several papers which outlined the advantages of using these types of data to avoid the need for pilot holes and unplanned side-tracks. Typically, the focus of these tools is to land-out the well in a particular target sand and to then maximise net sand length in the well bore. This paper will demonstrate additional benefits that these types of measurements can offer which include; reducing seismic depth uncertainty whilst increasing the confidence of the reservoir boundaries; and providing more information on the depositional architecture of the reservoir to aid integrated subsurface description. Cost savings can also be realised using these measurements, not only by mitigating pilot holes and unplanned sidetracks, but by increasing the confidence of a geological model during drilling thereby allowing an increased drilling ROP and eliminating costly delays e.g. waiting on interpretation of biostratigraphic data to enable well planning updates to occur. Finally, this paper will look at the importance of ensuring pre-job modelling is accurate and representative of the types of formations to be drilled, provides alternative scenarios to the reference case model and how case sensitivities can be used to provide models that match the realised outcome, increasing confidence in the results and speeding up the geosteering decision making process. This work was performed in an offshore Tertiary deepwater turbidite formation, comprising a system of stacked, confined and unconfined sands with complex fill patterns and multiple incision surfaces. The well consisted of 4 individual target sands that dipped to the north and displayed an offset stacking pattern with two sands targeted at the crest and two additional sands down dip. As the downdip target sands were previously unpenetrated, seismic depth uncertainty was large resulting in an opportunity to run extra deep azimuthal resistivity measurements to ensure that the sands could be located and drilled to maximise net sand length in the reservoir section. High angle wells drilled in turbidite formations can be challenging to geosteer because of the unpredictability of the structure of the formations themselves and because the boundaries between net and non-net intervals are often not distinct due to anisotropic effects. The ability of extra deep directional LWD resistivity tools to remotely detect hydrocarbon bearing reservoir and image the formation boundary when approaching helps to reduce the geological risk. The data from these tools can be quickly and accurately applied to a model which leads to better and more timely decisions that can decrease rig time, reduce costs and increase the probability of drilling a successful well.
Belyaeva, Olga (Salym Petroleum Development N.V.) | Podberezhnyy, Maxim (Salym Petroleum Development N.V.) | Zverev, Vladimir (Salym Petroleum Development N.V.) | Sviridov, Mikhail (Baker Hughes) | Mosin, Anton (Baker Hughes) | Antonov, Yuriy (Baker Hughes)
Abstract West Salym is a Salym Petroleum Development oil field located in Khanty-Mansi Autonomous Okrug, 120 kilometres south-west of Surgut. The West Salym oil field was discovered in 1987 and was brought on stream in 2004. The reservoirs vary from fluvial/deltaic to shallow marine deposits. The primary development of the central area of the West Salym field is completed. The edge of the field remains undeveloped and potentially attractive. The edges of the field are presented by a mouth bar and characterized by significant structural formation changes, including unknown formation dips and the presence of local carbonate concretions and stripes. The sand thickness of the target layer is 15 m with a minimum oil height of 1m, caused by structural dip and OWC closeness. In these conditions it is difficult to drain the area with geometrically placed wells within the hydrocarbon-saturated layer based on well correlation and 3D seismic interpretation results. Another challenge is the low resistivity contrast between shale, oil- and water-bearing layers, which complicates reservoir properties evaluation and distinguishability of different fluid saturations. To evaluate capabilities of modern reservoir navigation technology, two horizontal wells (500 m each) were drilled for the first time in the West Salym field, using deep-azimuthal resistivity technology and advanced data interpretation software. Drilling both horizontal wells was improved by pilot holes (well A and D) with standard GR-Resistivity-Density-Neutron logging suite and pressure testing‥ Logging-while-drilling, deep-azimuthal resistivity technology has been used in the field development, contributing to proactive reservoir navigation. This technology provides input for the interpretation of an extensive set of multi-component, multi-spacing and multi-frequency measurements. This data are usually sufficient to resolve the formation properties in the vicinity of several meters from the wellbore and to adjust the direction of the well trajectory. However, due to time restrictions, very simple resistivity models and only the subset of data are often used for real-time interpretation. Moreover, the structure of the data subset is often predefined to provide the maximum depth of investigation, neglecting the quality of formation parameter resolution. In some particular fields it can lead to increased uncertainties during reservoir navigation. The data interpretation software mentioned in this paper has an excellent performance and enables the real-time processing of the full set of downhole measurements based on multi-layered formation models. This case highlights the first use of this software application in the Russian Federation. The software is based on the method of the most-probable parameter combination and keeps the optimal balance between the information recovered from the measured data and all available a priori knowledge about the structure. The ability to accurately involve a priori information enhances software capabilities of resolving layers with low-resistivity contrasts. Moreover, inversion software is user-controlled to carefully monitor lateral and vertical changes in the geology. The advantages of data inversion software ensured successful reservoir navigation in the challenging conditions of the West Salym field. All steering decisions were made according to the consistent and reliable multi-layered formation resistivity model that was constructed in real time during the drilling. A good net-to-gross ratio was achieved: almost 75% for one well and 50% for the other. Expected oil rates are 300 and 150 m/day. Post-drilling analysis showed that in the case of geometrical drilling without the application of reservoir navigation technology the net-to-gross ratio would not exceed 40%.