Pressure Conditioned Modeling: Application of Time-Lapse Shut-in Pressure Data to Map Connected Reservoir Regions for Conditioning of 3-D Geomodel Property Distributions
Authors: Kayode Babatope O. , Al-Saleh Mohammed A. , Lyngra Stig , Alghareeb Zeid M. 
Published: October 2018

Abstract
In the traditional sequential workflow approach, the geomodeler builds static models based solely on log and core data interpretations, sometimes supplemented with geological understanding, without any dynamic data considerations. In the consequent step in the traditional workflow, the simulation engineer modifies the static model, as required, to achieve a match to the dynamic data, sometimes ending up with a modified geomodel that is significantly different from the original static geomodel. In the modern integrated reservoir modeling practice, the established workflows have become a cyclical process where learnings from the history match are taken back to refine the geomodel. For example, if a well does not produce its historical rate during history match, the permeability-thickness product (KH) around the well is caliberated to well-testing KH using pressure transient derivative matching and the discrepancy is taken back to the geomodel to be resolved. With the intent to reduce history match cycle time, different approaches have been developed to use underlying data input, e.g., seismic impedance, object-based geological features, pressure transient derivative signature or pressure stream lines, to constrain the geomodel 3-D property population to more realistic outcomes based on the geological understanding and available dynamic data. This publication proposes a new such approach: Pressure Conditioned Modeling (PCM). The PCM concept is based on grouping wells with similar time-lapse static reservoir pressure trends into the same Connected Reservoir Region (CRR).
PCM is based on the assumption that similarity of time-lapse shut-in reservoir pressure trends between wells in a reservoir is an indication that the producers are draining from same connected reservoir region (same CRR), and no large scale geomodel permeability barrier is allowed to exist between these wells. Time-lapse shut-in pressure data of all wells in the reservoir are grouped on the basis of similar trends. A CRR map is created to reflect the spatial distribution of the hydraulically connected wells. The geomodeler then uses this CRR map as input in the 3-D permeability variogram definition. The core permeability data existing within each CRR is distributed only inside the subject CRR in such a way that no undesirable intra-CRR permeability barrier occurs.
The PCM methodology imposes a connectivity range on 3-D permeability distribution thereby ensuring that the connected areas within a globally heterogeneous reservoir are properly designated. A synthetic model example discussed in this paper resulted in a better pre-modification history match of wells and hence would require less time for history matching. More realistic field development predictions would also be achieved due to the improved connectivity between injectors and producers within each CRR in a fashion consistent with the observed field data.
For reservoirs with different multiple distinct multi-well pressure trends in the existing production history, the PCM concept should be used as it will produce a higher quality initial geomodel and significantly reduce the time required to obtain a history matched model without the need for significant modifications.