A Multistage Stimulation Operation to Unlock the Gas Potential of the Turonian Siltstone Formation in Western Siberia (Russian)

Major gas fields in West Siberia have been depleted by 50-80%, and field operators are actively searching for ways to reverse declining production and access new gas deposits previously ignored given their complexity. One such hard-to-recover deposit is the Turonian play. With total gas reserves reaching approximately 3 trillion cubic meters, Turonian gas is encountered in nearly the entire Northern part of West Siberia.Developing the Turonian deposits presents the following challenges:• Poor reservoir properties and low well productivity; • Significant reservoir heterogeneity and facial variability along the section and area-wise, which complicates well placement operations for an optimal gas extraction; • Low formation temperature and abnormally high pressure, which may require well operations in a near-hydrated regime; • High clay content, which leads to formation damage when water-based fluids are being used in reservoir drill-in operations.Drilling of Turonian horizontal wells is complicated by a narrow safe mud weight window, geology uncertainties, and high sensitivity of borehole stability to well trajectory.Analysis of Turonian well construction experience has identified technological solutions in two main areas:1. Provide high-quality hole in all sections of horizontal well, including lateral sections, with length more than 800 m (to run safely casing to planned depths with followed multi stage hydraulic fracturing in horizontal section). 2. Minimize formation damage, thereby preserving potential well productivity in a formation with a high clay content in wide range of temperature and pressure conditions.Core samples from the Turonian formations were tested to determine mechanical, elastic, and other rock properties. From these results different mud types were evaluated for formation damage and impact on the mechanical and elastic rock properties.1. Geomechanics is a vital part for productive drilling; 2. Optimal selection of dril-in and fracturing fluid played a critical part in achieving the project objectives; 3. Integrated approach to drilling system design and close cooperation between all team participants are the key success factors in delivering technically complex projects; 4. The combination of fit for purpose technologies into an effective drilling system can provide cost effective solutions for field development with region specific challenges and traditional technology limiters.

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Stimulation Fluid Advancements Improve Gas Production from Low Temperature Turonian Siltstone

Olennikova

Loginov

Yudin

et al. 2020

SPE Annual Technical Conference and Exhibition

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The Turonian siltstone found throughout the Siberian region in Russia is laminated, heterogeneous, and shaly; has permeability of 0.1 to 3.0 md; and contains hundreds of trillions cubic feet of natural gas. Hydraulic fracturing is necessary to achieve commercial production rates. Important developments have been made in optimizing a water-free fracturing fluid that can be used in similar cold and highly water-sensitive reservoirs worldwide. The study encompassed laboratory testing methodology, testing results, and field trial campaign analysis of the advanced water-free fracturing fluid. Non-Newtonian fluid rheological behavior, proppant transport ability, and fluid break under dynamic and static conditions at 60°F (15°C) were investigated and compared to conventional crosslinked water-based fracturing fluids. The field trials used a fluid recipe that enabled successful execution of very aggressive fracturing designs using large-size proppant placed at concentrations of up to 12 lbm/gal added (1400 kg/m3) in multistage fracturing treatments along a horizontal wellbore. This approach was used to improve fracture conductivity and fracture cleanup while minimizing fluid costs. The most significant advancements have been made in the breaker package design for the fluid mixed in diesel fuel. Improved breaking can accelerate the flowback period and create a high-retained-conductivity proppant pack, allowing large volumes of gas to flow with minimal restriction. Additional study of proppant transport revealed the presence of elastic properties that are not common for water-based guar-borate gels. This property enabled increased proppant concentration and aggressive hydraulic fracturing designs that were successfully employed in a field trial campaign comprising three horizontal wells completed with a total of 10 fracturing operations. Multistage fracturing completions consisted of shifting sleeves for the fracturing stages and separate ports with screens for the production stage to control formation and proppant flowback. This completion enabled selective fracture cleanout, which is vital in the low-temperature geological conditions. The developed stimulation approach resulted in progressive gas production increases after stimulation. Fluid development results indicate the new diesel-based fracturing fluid delivers an improved stimulation approach for low-temperature siltstones containing a high content of sensitive clays. It is the only project we have seen in the literature with a successful diesel-based fracturing fluid application in extremely low-temperature geology. Although developed for Russian fields, the work is equally applicable to any water-sensitive, shaly, low-temperature reservoir globally.

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A Multistage Stimulation Operation to Unlock the Gas Potential of the Turonian Siltstone Formation in Western Siberia (Russian)

Cited by 8 publications

References 1 publication

Development of Optimization Algorithms for Horizontal Gas Wells Development Process After MSHF

Development of Optimization Algorithms for Horizontal Gas Wells Development Process After MSHF

Engineered Drilling System Approach Unlocks Gas Potential of Shallow, Low-Permeability Development in Yamal Region

Stimulation Fluid Advancements Improve Gas Production from Low Temperature Turonian Siltstone

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