This paper describes the integrated approach to decision making on the optimized horizontal well completion with multistage fracturing (MSF) based on petrophysical, geomechanical and numerical modeling. This approach is pertinent in case of insufficient target exploration including absence of a full scale geo&hydromodel (FSGHM). The basic work process of the proposed approach is based on consistent efforts of a petrophysicist, geomechanical engineer, fracturing engineer and reservoir engineer and thus includes petrophysical and geomechanical modeling, fracturing design, numerical modeling and final planned well flow rate evaluation. The role of geomechanics in the production chain is to determine zones with the lowest and the highest fracture gradients to control fracture location and analyze fracture geometry. The basic objective of the proposed approach is to develop a set of recommendations to select: Optimized frac sleeve spacing to increase production during a certain period of well production;Optimized proppant injection volume in general and for each fracture;Recommended horizontal well paths for efficient multistage fracturing completion and reduction of the most probable risks;Frac sleeve placement with provision for the horizontal well path through the section (vertically) to optimize fracture initiation points and maximize reservoir coverage. Besides, according to the base history, costs of new target development using available production technologies can be estimated based on the completed work package. An additional objective of this approach is identification of interdependent parameters for further facilitation of downhole surveys and laboratory studies and excluding of non-informative methods. This paper gives an example of the developed method application for a prospecting and appraisal well at one of the West Siberian fields with a target characterized by extremely low permeability and uncertainty.

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This paper discusses an approach to the static Young's modulus calibration on the basis of fracturing statistics from one of the West Siberian fields. The relevance of this work is due to the fact that there are many fields in the region where multi-stage fracturing is en masse carried out in horizontal wells, but laboratory tests of mechanical and strength properties are lacking. The procedure is based on reiterated matching of estimated fracture closure time to the actual values obtained during interpretation of data-frac test (or calibration or minifrac test) results in the course of the sequential search over the pairs of Young's modulus and leakage factor values. Then simulation of main fracturing is carried out, and simulation result is compared to the actual results of the works (whether fracture was successful or finished with emergency shutdown of pumps). From the entire set of experiments, the multiplier that satisfies all accidents and describes successful operations is chosen. Calibration of mechanical properties and stress model was successfully carried out in this field using the field data of more than hundred fracturing operations, which is evidenced by the similar values obtained in fracturing simulation and half-lengths of hydraulic fractures matched with field development data in one of the hydrodynamic model implementations. This work is a continuation of research [1, 2] and includes comparison of field development parameters in both calibration methods, which led to the final decision on the repeated laboratory studies, because none of the calibration methods used allowed creating a single universal model of mechanical properties. One of the models more reliably describes the situation of fracture development within the rock mass, the other relates to fracture development along the fault. In addition, the geomechanical model analysis also revealed that in most cases where fracture intersects the fault it would develop along it.

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This work is devoted to the development of methods for determining the stimulated reservoir volume (SRV) taking into account the contribution of natural fractures hydrodynamically not connected with technogenic one with the example of Western Siberia reservoir. At present, more and more fields with a complex geological structure, including low-permeability reservoirs, require effective technologies for exploitation, which in turn has led to the massive applying of horizontal wellbores and technologies of multistage fracturing. Modeling of multistage fracturing is a complex process that requires an understanding of the mechanical behavior of the formation, cracks and faults. The cracks formed during the hydraulic fracturing change the stress field around it, this effect is called the shadow stress effect. Natural fracturing can have a significant effect on production rates, in particular, on the hydrodynamic connection of the reservoir and the migration path of fluids. If stress shadow effect of the technogenic fracturing is taken into account, then can be additionally taken into account the reactivated natural fractures with induced stresses as well. In the process of the work, mechanisms of formation of natural fracturing were determined on the basis of seismic attributes and reconstruction of paleostresses, a natural fracture network model was constructed using geomechanical information. The results obtained during the construction of a NFN play one of the key roles for the modeling of the multistage fracturing in fractured reservoirs allows to take into account information on the intensity and direction of development of natural fracturing in addition to mechanical properties: elastic and strength characteristics of rocks. In this paper, we demonstrate the results of a numerical evaluation of multistage fracturing influence in the change of the stress field. The stress field, modified during the stimulation, was used to assess the critical stress fractures, which allows increasing the stimulated reservoir volume due to reactivated natural fractures. Such cracks do not need to be fixed, since they are formed by sliding along the plane of failure with small changes in the stress field and give an additional contribution to the total area induced fractures. The demonstrated technique allows to maximize the area of induced fractures and increase the stimulated reservoir volume by taking into account the critically-stressed one.