In the Houston-Galveston Area, since 1975, there has been a successful effort to reduce our reliance on groundwater and increase our use of surface water due to the environmental impacts of groundwater over-pumping. The Harris-Galveston Coastal Subsidence District has required reduced groundwater use to slow or stop subsidence (sinking of ground level) in Harris and Galveston Counties.
However, there is another cause of subsidence in our area which causes the activation of surface faults (which can damage roads, houses, and buildings), loss of wetlands and flooding. That cause is the production of oil/gas which involves the removal of oil, natural gas, and produced water from deep underground reservoirs. For example, in the early 1910’s at the Goose Creek Field in Baytown 3 feet of subsidence occurred and turned a low-lying area into part of Galveston Bay.
Since the 1980’s, research has discovered that subsidence, due to oil/gas production, is greater than previously thought. Subsidence due to oil/gas production is of two types. One type is local and centered on the oil/gas field where the oil/gas/water is withdrawn. The second is regional in scope and generally covers several oil/gas fields that are connected underground. These interconnected fields are found in southern Harris County and northern Galveston County.
Studies since the early 1970’s have shown that oil/gas fields have been depressurized, a step which must occur before subsidence happens. A high density of oil/gas fields or a large single oi/gas field with enormous depressurization can produce regional subsidence. In some places, oil/gas production that has occurred since groundwater withdrawal ceased, is the principal cause of subsidence in the Harris-Galveston Area.
In the past, oil/gas production has not been considered a cause of significant subsidence in the Houston-Galveston Area. Now we know that measurable subsidence has occurred due to oil/gas production, although the subsidence is not as great as that caused by groundwater withdrawal. This is because oil/gas fields are small (reservoirs) in comparison to large groundwater aquifers. The small reservoir size limits the total subsidence that can occur from oil/gas pumping.
On Bolivar Peninsula, at the Caplen oil/gas field, a fault activated by oil/gas/water pumping caused about 1,500 acres of wetlands to become open water. This occurred sometime between the 1950s and 1989. Other places, where oil/gas subsidence has occurred are the Neches Valley – including Port Neches Field and Port Acres- Port Arthur Field, Clam Lake Field on Bolivar Peninsula, Saxet oil/gas field near Corpus Christi, and coastal Louisiana.
Local and regional subsidence caused by oil/gas production can result in flooding. It is unfortunate that the oil/gas industry has never been held accountable for the flooding, wetlands loss, and fault activation that it caused in the Houston-Galveston Area. Certainly, mitigation measures funded by the oil/gas industry could have made Houstonians and Galveston Bay healthier and safer. Perhaps in the future, we should press the oil/gas industry to pay its’ fair share of the damages that we have suffered in the Houston-Galveston Area due to the subsidence caused by its’ operations.
By Brandt Mannchen