The paper presents a study of field development optimization of the large tight oil field in West Siberia. The field is at an early development stage and is characterized by low permeability (less than 1 mD). It is developed by horizontal wells with multistage hydraulic fracturing. Analysis of available information about the field revealed the potential to improve field development efficiency. Field development analysis and optimization were carried out based on the experience of development of similar Canadian reservoirs. Two large fields were selected as analogues: Bakken ViewField and Pembina Cardium. The data on these fields is publicly available. These fields are developed during a long period of time enabling operating companies to learn from experience and use new knowledge and data to optimize completions systems and development strategies as a whole. Therefore it is possible to not only analyze the current field development stage, but also trace the evolution of approaches and assess, what benefits can be obtained from making various changes to the applied technologies and field development strategy. The positive experience of development of the Canadian fields formed the basis for the field development optimization options. A set of suggested project decisions will enable improvement in field development efficiency and, in case of confirming by pilot projects, can be recommended for full-field implementation in the considered field and in the analogue fields.

The objective of this study was to identify efficiencies and prospects for future implementation of an advanced fracturing system for horizontal wells in which fracturing operations are combined with coiled tubing (CT) operations and are run together with CT inside the well. This results in decreased operation time for multistage fracturing (MSF) jobs. Nowadays, in Western Siberia extensively used following workflow at wells: preoperational work (which include casing drifting, bottom-hole cleaning with sludge trap, coiled tubing slack off for opening a frac-port, pulling the coil out of the hole and following fracturing operation). The method of pumping fracturing operations through the annulus of a CT had been given especially for elimination of extra operationsat wells during jobs at Vinogradova field. The method implemented with a modern completion system that includes special four-way union and protector for coiled tubing and coiled tubing 50.8 mm. The paper contains the analysis of executed MSF jobs with coil tubing inside the well and special equipment which were used in order to implement all the operations during fracturing. The innovative approach to cooperative work between the hydraulic fracturing and CT fleets enabled to reduce the operational timeline by 40% at the first well. As this technology comes into greater use in Russia and abroad, there will need to be sophisticated study and correct implementation. For future success, it will be necessary to perform an in-depth analysis to achieve further reduction in the operating timeline reduction and to eliminate complications in the process.

Identification and quantification of in-situ stress barriers is a crucial part of every hydraulic fracturing design and treatment programme. The absence of stress barriers may lead to significant vertical growth of the fracture, creating a channel between the oil-bearing intervals and potential undesirable water-bearing formations. This paper presents a case study where the in-situ stress profile in a tight oilfield in West Siberia was re-calibrated. The original stress profile, which was based on core analysis, gamma ray and acoustic data, indicated the stress contrast was enough to contain the fracture within the producing layer. Unexpectedly, high water cut between 60 to 70 % was reported in the horizontal wells, where multi-stage hydraulic fracturing was performed and the source of water production was uncertain. Consequently, straddle packer microfrac testing was conducted in one well to create a more detailed and better-constrained stress profile in the target oil-bearing formation as well as in the bounding shale above and below. The data obtained indicated very little stress contrast between the production layer and the surrounding shale layers. The revised stress model differed significantly from what was typically used in West Siberia. The updated hydraulic fracture model showed that excess height growth into the surrounding shale barriers was likely, and breakthrough into the water-bearing layer located 50 to 70 meters above could explain the high observed water cuts in the treated wells. Assuming a uniform stress profile along the lateral, the hydraulic fracture design was then optimized to decrease the risk of breakthrough into the water zone. The optimized treatments involved low-viscosity fracturing fluid and also a reduced amount of proppant per stage used in the treatment. The optimized hydraulic fracture treatment was performed in several horizontal wells, which saw a reduction in the initial water cut to below 10%, and also experienced an increase in oil production. This demonstrates the importance of having reliable stress measurements for hydraulic fracturing design.

In this paper, the effect of local changes in the stress-strain state of rocks is analyzed, and an appropriate approach is proposed for modeling the geometry of hydraulic fractures on horizontal wells under conditions of a dense drilling network, including Zipper Frac technology. The main source of factual information on the development of cracks are the pressure curves obtained during injection tests, mini-fracs and main frac jobs, including fracs on offset wells and microseismic monitoring of fracturing. At Vinogradov field as the optimal selected row production system. The analysis of the accumulated experience made it possible to identify promising areas for increasing the efficiency of the production system, including reduction in the distance between rows, a change in well azimuths relative to the principal stresses, and the extension of horizontal sections of the wells. In this paper, we analyze the results of multi stage HF in conjunction with modeling the geometry of cracks in various software products, taking into account and without taking into account the local change in the stress-strain state of the rocks near hydraulic fractures. The simulation results are cross-validated with actual information on the various wells of the development object under consideration. Modeling and analysis of the geometry of cracks in neighboring wells, oriented both longitudinally and transversely with respect to the direction of maximum horizontal stress, is carried out. Including the mutual influence of stages of Zipper Frac technology is analyzed. Taking into account the effect of local stress redistribution made it possible to achieve a high degree of correspondence between the results of modeling available actual information from the target wells and the environment wells (pressure responses, microseismic results and production figures). Without taking this effect into account, it was not possible to achieve such a degree of compliance. The conclusion is made that the effect of local stress redistribution both during fracturing at adjacent ports of a single horizontal well and fracturing of adjacent horizontal wells has significant influence on geometry and, in particular, to the fracture height, which is critical in the geological conditions of the considered object. An approach to modeling and planning of the multi stage frac on horizontal wells in conditions of complex reservoirs similar to the object under consideration was developed. In particular, new approaches to the optimization of the sequence of Zipper Frac stages are proposed and recommendations are made for carrying out fracturing in the conditions of both longitudinal and transverse drilling mesh in relation to the direction of the maximum horizontal stress.

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