Determining optimal well locations from a 3d reservoir model

Abstract

There is disclosed herein a systematic, computationally-efficient, two-stage method for determining well locations in a 3D reservoir model while satisfying various constraints including: minimum interwell spacing, maximum well length, angular limits for deviated completions, and minimum distance from reservoir and fluid boundaries. In the first stage, the wells are placed assuming that the wells can only be vertical. In the second stage, these vertical wells are examined for optimized horizontal and deviated completions. This solution is expedient, yet systematic, and it provides a good first-pass set of well locations and configurations. The first stage solution formulates the well placement problem as a binary integer programming (BIP) problem which uses a “set-packing” approach that exploits the problem structure, strengthens the optimization formulation, and reduces the problem size. Commercial software packages are readily available for solving BIP problems. The second stage sequentially considers the selected vertical completions to determine well trajectories that connect maximum reservoir pay values while honoring configuration constraints including: completion spacing constraints, angular deviation constraints, and maximum length constraints. The parameter to be optimized in both stages is a tortuosity-adjusted reservoir “quality”. The quality is preferably a static measure based on a proxy value such as porosity, net pay, permeabilty, permeability-thickness, or pore volume. These property volumes are generated by standard techniques of seismic data analysis and interpretation, geology and petrophysical interpretation and mapping, and well testing from existing wells. An algorithm is disclosed for calculating the tortuosity-adjusted quality values.