The channel fracturing technique changes the concept of proppant fracture conductivity generation by enabling hydrocarbons to flow through open channels instead of through the proppant pack. The new technique is based on four main components: proppant pulsing at surface with fracturing equipment and software, a customized perforation strategy, a fibrous material to deliver stable channels, and a set of models to optimize channel geometry. The Taylakovskoe oil field is located in western Siberia—430 km away from the nearest settlements. The Jurassic reservoir in Taylakovskoe field is a sandstone formation with significant net pay (average 25 m) and middle-range permeability (3 to 20 mD). Bottomhole temperatures range between 85°C and 90°C. Fracturing gradient is typically 14 kPa/m. The majority of the wells are stimulated immediately after drilling. Sufficient fracture conductivity and effective fracture length are essential for adequate well performance. The optimization of hydraulic fracturing treatments conducted in recent years was based on improved fluid chemistry and pumping "aggressive" fracture designs; this yielded high-quality results. The new channel fracturing stimulation technique, which allows significant increases in fracture conductivity, became the next technological progression. With channels inside the fracture, fluid and polymer residue flow back faster than with a conventional proppant pack, improving cleanup and increasing effective fracture half-length. One of the most important advantages of the new technology is a very low risk of screenout events. The fibers make fluid more stable, while the presence of clean pulses around proppant structures promotes bridging-free flow. Reduced risk of premature treatment termination is even more important in remote operations such as in the Taylakovskoe field because of the higher costs of nonproductive time and deferred oil production. Candidate selection criteria were developed specifically for local conditions. Ten channel fracturing treatments performed in Taylakovskoe wells have already showed significant increases in incremental oil production—average 44% beyond expected production as shown by well performance analyses. We describe the performance evaluation of wells completed with this technology and future plans for applying channel fracturing methods in the Taylakovskoe field.
Hydraulic fracturing has probably become the most attractive solution to enhance production in the oil fields of Russia and western Siberia in particular. Besides optimizing the fracturing design with the ultimate goal of increased production, it is equally important that optimized fracturing treatments be pumped successfully in the field. Only a high success rate with a limited number of screenouts can help guarantee that production optimization will be achieved. It is also important to reduce downtime, for operators to have earlier production, and for service providers to optimize equipment utilization. In western Siberia, harsh conditions exist all year round. The winters are long with temperatures way below freezing for several months in a row. The summers are short, but can be quite warm. Logistics are difficult due to these weather conditions and because roads are rarely in good shape and worksites may be located very far away from equipment bases. To achieve success under these conditions, a lot of emphasis must be placed on quality control (QC) and quality assurance (QA). QC/QA must address many issues on the equipment side due to the harsh environment, but just as important is materials, in particular materials required for preparing the frac fluid and to a smaller extent the proppant used to hold the fractures open. The frac fluid itself creates the biggest QC/QA challenge. Of special importance is the mixing water because the sources for mixing water vary and the quality of the water changes seasonally. Stringent QC/QA procedures must be in place, including fluid testing under actual reservoir conditions to check the performance of the frac fluid downhole. This paper describes processes that have been developed and implemented in western Siberia. It includes equipment checks and maintenance as well as QC/QA procedures for frac fluids and their components and proppants. Specific issues related to the special location will be discussed and solutions presented regarding how a successful frac treatment can be provided every time. Introduction Propped hydraulic-fracturing design has evolved significantly over the past decade, in particular for Siberia and for Russia in general. Although today small treatments (5-15 metric tons [MT]) are still being performed, mainly to bypass near-wellbore damage, many companies have adopted a proper frac design and overall production optimization approach. This means that treatments are designed to optimize production based on the specific well and reservoir parameters for each field. Treatments sizes of 200-300 MT are common, and the average proppant volume pumped per treatment is around 80-100 MT in areas where operating companies have taken on this engineered approach. Currently, treatment design is one issue, while job execution is another. Without proper execution, the production increase predicted by simulation models based on the designed fracture geometry will not be obtained. It is therefore critical that all parts of a fracturing treatment execution be controlled in a way that the designed frac geometry (and with it, conductivity and production) will be delivered. This paper discusses propped hydraulic-fracturing treatments and it is assumed that wells have been prepared as required with proper casing, cementation of the casing, perforations, and wellhead installations to allow pumping the designed treatment. It is also assumed that all post-frac treatment cleanout and workover procedures are performed so that no damage to the already created fractures will occur. The particular subjects of this paper are equipment, fluids, and proppant. Each plays an important part in eliminating "execution" from the equation for delivering the best fracturing treatment. Only then are engineering teams able to focus their attention on other design and reservoir related issues. Although other issues are important to overall success and worthy of full attention, they will not be discussed in this paper, including perforating,1 cleanout, workover, pump selection, or other peripheral subjects. The main task of both operating and service companies is to deliver the optimum well performance. Several fracturing treatments result in early termination of the treatment due to what is generally described as screenout. Screenout is a process that needs to be looked at carefully.
Western Siberia's Jurassic and Achimov formations are well known for low permeability, high heterogeneity, and lamination in which the majority of the wells require stimulation. However, production declines call for restimulation operations to improve field economics. Common challenges for both fracturing and refracturing treatments include achieving considerable effective half-length and increasing fracture conductivity while reducing screenout rates, which average 10%. To solve both problems, the channel fracturing technique was implemented.The channel fracturing technique changes the concept of proppant fracture conductivity generation by enabling hydrocarbons to flow through open channels instead of the proppant pack. The new technique is based on four main components: proppant pulsing at surface with fracturing equipment and software, a special perforation strategy, fibrous material to deliver stable channels, and a set of models to optimize channels geometry.The use of the channel fracturing technique enabled economical production from 10 restimulated wells. Also, a reduction in screen outs was seen during refracturing treatments, which was an important advantage of the new method over the conventional stimulation technique based on homogeneous proppant placement.Bottomhole pressure gauges were used consistently throughout the campaign to study friction pressure and net pressure behavior during channel fracturing jobs. Overall, zero screen outs occurred throughout the campaign and well productivity was 15% to 30% higher when restimulated with channel fracturing.
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