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 work describes the implemented techniques which help optimize reservoir engineering for tight oil deposits with the usage of multi-stage hydraulic fracturing by up-to-date methods of fracturing values’ evaluation. The work also identifies reasons of high water cut of well production after the multi-stage hydraulic fracturing at the V. Vinogradov field. The work also describes principles of preparing and implementing the optimum design of the multi-stage hydraulic fracturing under the conditions of unconstrained growth of the vertical component of the hydraulic fracture without any restraining barriers. After the set of operations, the quality of hydraulic fracture control increased and the well production water cut reduced.

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.

The paper presents the study of the water-gas stimulation process with alternate injection as applied to the core samples from the Vostochno-Perevalnoye oil field located in West Siberia. The test data analysis showed an increase of oil displacement efficiency due to gas displacement of oil and the dependance of relative permeabilities not only from the saturation history (hysteresis) but also from the number of water-gas stimulation cycles. The authors noted the hysteresis of relative permeabilities to be a significant factor requiring consideration when conducting experimental studies of relative permeabilities and computer modeling of the water-gas stimulation process.

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.