Role of Petroleum Production Subsidence on Submergence of Texas Coastal Lands: Case of the Rose City Field

Join Zoom Meeting
Join this presentation In-Person: BEG Building 130, VR Room 1.116C Or Via Zoom

Meeting ID: 932 0137 7630
Passcode: 013011

Presenter

Dr. John M. (Jack) Sharp, Jr.
Carlton Professor of Geology Emeritus
Department of Earth and Planetary Sciences
The University of Texas at Austin

Description

When Texas coastal lands become submerged below mean high water, they become property of the state, unless the submergence is caused by subsidence due to extraction of water and/or petroleum.  This is complicated by a Texas legal theory that the this should be the sole cause. Subsidence caused by pumping groundwater in the general Houston-Galveston area is well documented. The role of petroleum production is less recognized, but its effects are well documented along the northeast Texas coast (the general Beaumont region). Relative sea-level (RSL) rise, which is the combination of eustatic sea level (ESL) rise plus subsidence and tectonic movements (either up or down), is the cause of submergence. Minor causes of submergence include natural rates of subsidence, coastal retreat, growth faults, soil compaction, and collapse of subsurface cavities. Rates of ESL in the Gulf of Mexico  have been increasing in the past 125 years, but in the Beaumont region, petroleum production is the dominant process.  Analysis of survey data and bottom hole pressures show that the Rose City Field subsided by over 5 feet in less than 40 years and depressurization has extended beyond the mapped oil field area. Other processes are insignificant.  While it cannot be proven that petroleum production is the soil cause of subsidence at the Rose City Field, it is the only reason that lands over the field are now submerged and the land owner retained possession. Similar subsidence rates are documented for the Port Neches, Spindletop, and Port Acres/Port Arthur fields. Nevertheless, better data are required on subsidence over other oil fields, areal extents of depressurization, compressibility coefficients for the sedimentary column,  how shale properties change with depth and location, secondary (time-dependent) consolidation, and soil compaction.