Modeling of coupled reservoir and multifractured horizontal well flow dynamics

A fully implicit numerical model coupling reservoir and multifractured horizontal well flow dynamics has been developed to investigate the flow behavior and predict the productivity of such systems. The simulator solves simultaneously for pressure distribution within the reservoir and horizontal well domains, while taking into account the friction losses along the wellbore for laminar and turbulent flow conditions. Fractures with distinct properties are placed perpendicular to the wellbore axis and can intersect the well at arbitrary locations. The model is unconditionally stable and can be used to analyze the early transient period as well pseudo- and steady-state conditions. The use of multifractured horizontal wells has been gaining popularity in tight reservoir systems; however, the existing design protocols do not consider wellbore hydraulics that can have a governing role in the performance of the system. The appropriate design of a multifractured well has a definite impact on its performance. The numerical model presented in this paper can be utilized as a design tool towards the optimization of the number, position and penetration lengths of the fractures connected to a horizontal well. The calculated influx and pressure distributions along the wellbore show that solutions can deviate dramatically from the actual behavior if infinite conductivity idealization is used to represent flow dynamics in the horizontal well, and this discrepancy becomes more pronounced with an increase in reservoir permeability. Parametric studies are conducted to evaluate the influence of the number of the fractures in the flow behavior and productivity of the system. The observations and analyses presented in this paper will provide the much needed guidance to engineers who face the daunting task of designing a cost-effective optimum fracturing scheme in horizontal wells completed in formations with different flow characteristics.