History-Matching Using Refinement of Internal Reservoir Architecture on Reduced Order Dynamic Models
Authors: Kayode B. O. , Ganis S. 
Published: February 2025

History-matching (HM) is the process of updating the property field, frequently permeability, of a static model until its dynamic response (for example pressure) matches with observed data. Traditionally, HM focuses on improving well matches using localized permeability updates around individual wells. In this study, we developed a history-matching strategy that focuses on refinement of internal reservoir architecture of reservoir regions, resulting in faster HM and better predictive models.

A reservoir's Internal Reservoir Architecture (IRA) is defined in this work as the signature of its permeability-depth plot. A reduced order model is defined in this work as one partitioned into regions based on historical pressure cluster differentiation. Reservoir regions were created by the simulator through an automatic clustering of the global set of historical pressure data using an innovative pattern recognition algorithm to allocate a pressure region number to every well. The simulator then populates the wells’ region array using a Python Voronoi algorithm which allocates a region number to every grid-block based on the nearest well's region. The resulting 2D region array was then extended into a 3D array by duplicating each 2D array element across its column of blocks. The resulting 3D array was automatically included in the simulation run and used for region-based IRA refinement. Within each region, a comparison and calibration of the magnitude and signature of core and model permeability versus depth was conducted. In a previous work, several geological realizations were created using the same core data set but varying the variogram length, by refining those models’ reservoir regions, each model was rapidly history-matched.

Because the similarity of historical pressures on wells within a region is related to the permeability magnitude and IRA of that region, a focus on refinement of IRA resulted in immediate history-match improvement of the region's pressure cluster match. Since all the wells within each region have historical pressures that are similar in magnitude and trend, the improved match of a region's pressure cluster resulted in improved match on individual wells. This reduces the history-matching problem of several hundreds of wells using near-well permeability updates, to history-matching of few, in this case 6, regional IRA. In addition, this is a history-matching technique that does not require a long-time simulation run, a single time-step run is what is required to conduct an IRA refinement, after which a long-term run is conducted to verify the history-match improvements. It is also observed that after IRA refinement on the various geological realizations, the permeability logs of the non-cored wells became more representative while the permeability logs of the cored wells were relatively undisturbed by this history matching process.

Majority of pressure HM techniques rely on misfit coefficient that are aggregated from individual well match statistics. These techniques seek to improve the individual well statistics with strategies that are focused on permeability updates around individual wells. The present study improved well statistics through regional IRA refinements, enabling simultaneous improvement of multiple wells’ pressure match. The development of a methodology for internal reservoir architecture refinement of geological models is a key novelty of this work.