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Yakimov, S.. (TNK-BP) | Mukhametshin, M.. (TNK-BP) | Sosenko, O.. (TNK-BP) | Sadykov, A.. (Schlumberger) | Levanyuk, O.. (Schlumberger) | Oparin, M.. (Schlumberger) | Gromakovsky, D.. (Schlumberger) | Mullen, K.. (Schlumberger) | Lungwitz, B.. (Schlumberger) | Fu, D.. (Schlumberger) | Mauth, K.. (Schlumberger)
Abstract Scale formation and accumulation is a major concern for Russian production companies. In Western Siberia, most wells produce fluids via Electric Submersible Pumps (ESP), and it is believed that up to 30% of the ESP failures result from scale damage. Despite that scaling is commonly first recognized at the ESPs, it can ultimately affect the whole production system. The most efficient treatment strategy to prevent scale induced damage in the tubular, including ESP, is scale inhibition. Traditionally, this involves an inhibitor squeeze treatment which is a localized inhibitor placement covering the near-wellbore area or the continuous injection of the inhibitor via a capillary tube. However, these techniques are designed to protect the production system. Squeeze treatments in hydraulically fractured formations are not always effective. Scale inhibitors together with compatible borate fracturing fluids can be used for a more effective scale inhibitor placement throughout the created hydraulic fracture to prevent scale formation from the reservoir level to the production system. This technique combines hydraulic fracturing and scale inhibition into one treatment resulting in operational simplicity. Since 2008, the combined fracturing/scale treatments have been successfully applied in the Krasnoleninskoe oil field in Western Siberia. This paper outlines the learning procedure and presents designs, testing and monitoring results from the campaign conducted at Krasnoleninskoe oil field (including Talinskaya and Em-Egovskaya sections).
Kayumov, Rifat (Schlumberger) | Klyubin, Artem (Schlumberger) | Yudin, Alexey (Schlumberger) | Enkababian, Philippe (Schlumberger) | Leskin, Fedor (TNK-BP) | Davidenko, Igor (TNK-BP) | Kaluder, Zdenko (TNK-BP)
Abstract In the last two decades, hydraulic fracturing has become a routine completion practice in most oilfields producing from the low- and medium-permeability Jurassic formations in western Siberia. To optimize hydraulic fracture conductivity, operators and service companies were progressively decreasing polymer loading in fracturing fluids, developing new polymer-free fluids, implementing foams as fracturing fluids, increasing proppant size and concentration, enhancing polymer breaker performance, increasing breaker concentration, and implementing the tip screenout technique. All these methods have some positive impact on proppant pack conductivity but lead to higher risk of premature screenout. The intrinsic limitations stem from the fact that conductivity is created by the proppant pack, which physically limits permeability. The new channel fracturing technique allows development of an open network of flow channels within the proppant pack; thus, the fracture conductivity is enabled by such channels rather than by flow through the pores between proppant grains in the proppant pack. The channel fracturing technique is capable of increasing fracture conductivity by up to two orders of magnitude. Talinskoe field, located near Nyagan, Russia, produces from a series of Jurassic sublayers at depths of 2270 to 2700 m. Several oil-saturated sandstone sublayers are separated by shale barriers, and their development is conducted separately. For some wells, production from bottom sublayers JK10 and JK11 became uneconomical due to injection water breakthrough or low liquid rates. Production in these wells was switched to upper layers JK2 through JK9 after perforation and stimulation operations. Five of these wells were stimulated with the channel fracturing technique. Six-month of post-frac production data were compared with production data from eight offset wells stimulated recently via conventional hydraulic fracturing. The wells stimulated with the channel fracturing technology showed an average productivity index about 51% higher. This production effect still remains positive. The absence of screenouts confirmed reliability in proppant placement observed in other projects worldwide. The successful implementation of the channel fracturing technique in brownfield development is described in detail with a theoretical and operational review, results from laboratory experiments, and analysis of the production results in comparison with conventional fracturing.
Abstract Hydraulic fracturing is one of the major techniques in modern well stimulation practices. The purpose of the current contribution is to gain novel insights on utilization of cold water for fracturing services in Western Siberia aiming to reduce non-productive time and price while maintaining excellent quality of service delivery. The study covers the hydration of non-modified guar gum and borate crosslinking in cold water conditions, the associated risks and plausible benefits are also considered. Among all fracturing services, conventional borate crosslinked guar gum fluids remain the most widely utilized due to their economical profitability, availability, ease of viscosifying and handling. The reduced temperature of water affects the guar swelling and hydration during linear gel preparation and influences the crosslinking reaction rate for delayed borate systems. One of the obvious drawbacks of the guar-based fracturing fluids is the necessity for a water heat-up process, especially during winter period. Within the scope of present study we are discussing the opportunities and perspectives of non-modified guar fluids for cold water fracturing applications. This original research details the comprehensive laboratory evaluation and thorough theoretical study, which presents a variety of fracturing fluids available to hydrate and crosslink in water temperatures starting from 5 degrees Celsius. It was revealed that the hydration of guar polymer (loading 3.6 kg/m3) in water varies between 82-88% at 5 degrees Celsius. The optimized borate-crosslinked fluids provide viscosity greater than 400 cP at 96 degrees Celsius. The versatility of proposed fracturing fluids was proven by exceptional viscosity recovery to 400 cP in less than one minute after high shear regime in the range of 10-50 degrees Celsius, simulating the fluid behavior in near-wellbore area at ambient temperature. The scope of work included the development of cold water implementation criteria and evaluation of possible associated risks, e.g. the additional cooling effect upon contact with proppant. The results presented in the current work pave the way for implementation of conventional borate-crosslinked guar gum fluids for cold water fracturing. Without significant price increase the proposed approach allows to decrease 30% of non-productive time and reduce heating expenses. The approach is significantly beneficial in areas exposed to cold winter conditions like Russia, Alaska or Canada.
Loginov, Arkadii (Schlumberger) | Pavlova, Svetlana (Schlumberger) | Olennikova, Olesya (Schlumberger) | Fedorov, Andrey (Schlumberger) | Lomovskaya, Irina (Schlumberger) | Yudina, Kira (Schlumberger) | Danilevich, Elena (Schlumberger) | Shalagina, Anastasia (Schlumberger) | Radaev, Vladimir (Schlumberger)
Abstract Guar-based crosslinked fluids remained the prevalent choice of frac fluid for a long period of time, since massive hydraulic fracturing was started in Russia. Traditional frac fluid contains 2535 ppt of crosslinked guar, which results in very high fluid viscosity (min 400 cp at 100 sec-1 as rule of thumb) and low retained permeability of proppant pack - around 35%. With recent move towards complex geology reservoirs in Russia, where wide propped frac is no longer an optimum solution, the need in review of current fracturing approaches emerged. In several last years local operators started to gradually move away from h igh-viscosity fluids via its partial replacement with cleaner guar-based low viscous linear gel. However, even in this case retained fracture conductivities are typically not higher than 60-70%, especially in cases when hybrid fluid systems are used - linear fluid combined with crosslinked gel. Goal to reach improved fracture conductivity opens a field for new discoveries. This study objective is to evaluate the applicability of novel clean frac fluid for conventional reservoirs in Russia. Current study is focused on development of laboratory testing procedures and testing results analysis of novel synthetic polymer-based fracturing fluid in terms of its applicability on conventional reservoirs - tight sandstones. Viscous slickwater has already been widely used on shale reservoirs in North America, however was never applied for conditions of sandstones fracturing: in mili Darcy environment, in combination with ceramic proppant, pumping via tubing, utilizing pump rates less than 10 m3/min (60 bbl/min). Fluid rheology studies, leak-off behavior, regained conductivity of the proppant pack, regained permeability of the formation, dynamic proppant transport tests and dynamic fluid viscosity evaluation are described in the paper. Elastic properties of viscous slickwater (H.Zhao, S.Danican, H.Torres, Y.Christianti, M.Nikolaev, S.Makarychev-Mikhailov, A.Bonnell, Schlumberger, 2018) provide improved dynamic proppant transport and static proppant settling, in comparison with low viscous fluid - linear guar-based gel, i.e. better horizontal and vertical proppant distribution inside the fracture. Ceramic proppant pack conductivity even with high loadings of High Viscosity Friction Reducer without breakers showed superior results - Regained conductivity reached 100%. Coreflow experiments using conventional (1-10 mD) sandstone cores demonstrated 100% regained phase permeability to hydrocarbon, proving that fluid is non-damaging to formation. As a result of numerous laboratory studies performed, Viscous slickwater was qualified as alternative fracturing fluid to conventionally used guar-based gel and has been approved for field testing campaign on conventional tight sandstones in Russia. Field trials of novel frac fluid - Viscous slickwater demonstrated positive results both in terms of pumpability and well productivity on tight sandstones 0.5-3.0 mD This fluid has been recommended for further roll out to wider range of conventional oilfields.
The new channel-fracturing technique is capable of increasing fracture conductivity by up to two orders of magnitude. The channel-fracturing technique allows development of an open network of flow channels within the proppant pack, enabling fracture conductivity by such channels rather than by flow through the pores between proppant grains in the proppant pack. The successful implementation of the channel-fracturing technique in brownfield development is described in detail with the case study of the Talinskoe field in Russia. The Talinskoe section (for simplicity, referred to herein as the Talinskoe field) is part of the medium-sized, mature Krasnoleninskoe field, located near Nyagan, Russia. Exploration of this section began in 1982.