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Determination of Unit T1-2 (Turonian) flow characteristics in Yuzhno-Russky oil and gas condensate field is a priority area in the development process monitoring. This paper is focused on the informative value of downhole logging surveys conducted for assessment of the reservoir and wellbore flow geometry in the well after hydraulic fracturing. A more detailed consideration of this matter has become possible due to the extensive use of integrated logging suite data during estimation of input parameters for interpretation of pressure transient analysis results. The difficulty of this task was due to the fact that the extent of the vertical fracture in the Turonian formation was several times larger than the perforation zone and, as a result, estimation of the actual net pay based on the conventional logging suite data was hardly practicable. Besides that, due to poor perforation quality the geometry of fracture flow from the reservoir was affected. In view of this, Spectral Noise Logging technique was applied to estimate the reservoir effective thickness contributing to the flow through the fracture created as a result of the hydraulic fracturing job. The integrated logging suite supplemented with SNL-HD tool was run at several differential pressures. As a result of SNL-HD and HPT surveys and subsequent flow modelling, valuable information on fracture flow rates was successfully obtained.

The Turonian siltstone is widely spread through the Siberian region in northern Russia. It is a laminated, heterogeneous and high-shale content formation with low permeability (1-3 mD) and low reservoir temperature (15 degC), with more than 300 trillion m3 of natural gas in place. Hydraulic fracturing is a necessity for economic and sustained development of the field in the described geological conditions. High montmorillonite contentand extremely low temperatures make the Turonian reservoir a true challenge for frac experts. A pilot stage of project development has been executed with horizontal drilling and multistage fracturing. A well has been constructed with 168-mm casing and 114-mm liner, with the liner separated into discrete segments with hydraulic packers. Each zone is equipped with filters integrated with the inflow control devices (ICD)plus frac portsenabling multistage frac jobs and subsequent controlled, solids-free production.Frac ports and ICDs are shifted using coiled tubing (CT) equipped with a downhole hydraulic key. Significant innovations were implemented for the frac fluid design in terms of a noveldiesel-based fluid breaker package.Additionallab investigation of proppant transport capacity has revealed some elastic properties of diesel-based fluid, that are not typical for crosslinked guar-borate water-based fluids. This provided the opportunity to significantly increase proppant concentration and frac design aggressiveness for the successful completion of a trial campaign.With the optimized fluid, the engineering team has achieved outstanding results in frac design, when large-sized proppant has been pumped at concentrations up to 1400 kg/m3 during multistage frac operations in horizontal wells.The combination of technologies led to rapid well cleanup with a quick transition to stable gas flow to sales. New achievements in well completion techniques andwater-free frac fluid optimization can be implemented when dealing with similar low-temperature reservoirs with high content of water-sensitive clays.

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