236 - Analysis of the Gulf Coast Aquifer System Compaction Based on Extensometer Records at Baytown and Pasadena, Texas, USA

A total of 14 extensometers were installed in Houston Galveston Region, Texas USA at 12 locations to record compaction. The earliest of the extensometers record compaction since 1973. Records from 3 of the extensometers installed at Baytown (Shallow and Deep) and Pasadena exhibit anomalous subsidence from 2009 to 2017. The maximum compaction occurred between 2009 and 2014 with Baytown Shallow recording 164 mm, Baytown Deep 72 mm, and Pasadena 135 mm. The anomalous subsidence is found to exhibit features not related to primary consolidation subsidence (PCS) and secondary consolidation subsidence (SCS) of the Gulf Coast Aquifer System. Groundwater level records at the extensometer locations indicate that the anomalous subsidence is not related to groundwater exploitation and creep of the Gulf Coast Aquifer system in this region. Analysis of compaction data for the three sites indicates that the subsidence is partially elastic. Salt dome growth/evolution resulting in activation/reactivation of subsurface and surface faults is proposed as the mechanism responsible for the anomalous subsidence. The anomalous subsidence is analyzed in terms of depressurization of reservoir rocks resulting in the movement of surface and subsurface faults.