Approach to Understanding the Stimulated Reservoir Volume in Unconventional Oil Reservoirs

Abstract

Abstract At the early stage of unconventional oil field exploitation under circumstances by lack of geomechanical reservoir model the way to estimate drainage volume of fractured horizontal well is considered. In order to create connected reservoir volume and to improve reservoir sweep efficiency though the initiating drainage channels in unconventional reservoirs multiple hydraulic fracturing is used. It improves the recovery of oil from previously impermeable vast pore volume. In this case the target of stimulation is not a planar fracture with definite length and height but the supreme rock failure directed to development induced fracturing network and therefore hydraulic techniques distinguishes from standard one. Generally this complex network is achieved by specific hydraulic fluids injection at elevated rates. As a result artificial fractured rock volume is created in the reservoir and provides the draining of a great previously unavailable hydrocarbon reserves which sustaining high production rates and acceptable cummulative oil production per well. The concept of stimulated reservoir volume is used for the purpose of characterizing the rock volume subjected to stimulation. In the result of this treatment the complex hydraulically communicated fracture network is generated around the horizontal well. It defined by extensive improved filtration properties due to permeability of induced fractures. Initial stock tank oil in place is governed by rock capacities and saturation of mobile hydrocarbons. Effects associated with fractures are the key ones for production intensification since they define the distribution of fluid's flow paths in the reservoir. The possibility of their accounting in the simulation modelling is an important challenge since it directly defines the history matching quality and therefore the forecast of long-term production. During the application of the concept of stimulated reservoir (SRV) penetrating with multi-fractured horizontal well the necessity in stimulated reservoir volume characterization is arised. This characterization concerned with the base properties which exert the impact on well productivity index and on the oil recovery factor. Then as a result, the use of mathematical modeling to solve the inverse problem to clarify the structure and properties of unconventional formation by reproducing the history of development authors state three basic geological and technological parameters which define the well production performance of unconventional reservoir with SRV – the volume of stimulated zone, shape-factor and effective permeability of fractured zone. At the early stage of exploitation the unconventional reservoir, which characterized by the availability of production history and the drawback of geomechanical data, the approach is presented which provides an opportunity to create the fluid-flow reservoir model ensures with higher degree of accuracy and more reliable long-term production forecast.