Effect of Hydrocarbon Production and Depressurization on Subsidence and Fault Reactivation

dc.creatorWang, Fred P.
dc.creatorNance, Hardie Seay, 1948-
dc.description.abstractSubsurface fluid withdrawal is one of the most common causes of land subsidence. Subsurface fluids include water, oil, gas, and steam. Examples of subsidence induced by groundwater withdrawal significantly outnumber those induced by hydrocarbon production. Several severe subsidence cases induced by hydrocarbon production were documented including Goose Creek field (Pratt and Johnson, 1926), Wilmington field in Long Beach, California, Lost Hill and Belridge fields in California, Bolivar coast in Venezuela (Nunez and Escojido, 1976), and Ekofisk field in the North Sea (Sulak, 1991). Ekofisk field is the most recent and costly example. Ekofisk field was discovered in 1969, and production from the 700- to 1,000-ft-thick geopressured high-porosity chalk reservoir (top at 9,600 ft subsea) began in the 1970s. By 1984, the seabed under the Ekofisk complex had subsided about 10 ft. To stabilize platforms and facilities, an unprecedented billion-dollar project was initiated in 1987 to elevate the four platforms an additional 20 ft and to construct protective barriers around the hydrocarbon storage tank. In addition, gas and water have been injected to increase reservoir pressure and arrest active subsidence. Nevertheless, the local seabed has subsided continuously to 26 ft in 2001. In coastal southeast Texas, land subsidence has been severe in the Houston/Galveston area. However, despite enormous oil and gas production from Frio and Miocene formations, most land subsidence and surface faults in the area have been attributed more to regional shallow groundwater withdrawal than to hydrocarbon production (Kreitler, 1976; Verbeek and Clanton, 1981; Holzer and Bluntzer, 1984; Gabrysch and Coplin, 1987). Holzer and Bluntzer (1984) showed that hydrocarbon production has caused an additional 0.1 to 0.2 m of local subsidence near some oil and gas fields. To better quantify the impact of hydrocarbon production on subsidence and fault reactivation, we need to eliminate the effects of groundwater withdrawals by selecting fields having insignificant groundwater withdrawals relative to hydrocarbon production. Two field areas in the coastal southeast Texas-Port Neches in Orange County and Caplen in Galveston County-satisfy this prerequisite. Both areas contain active surface faults and wetlands that have been inundated by marine waters (White and Morton, 1997). Most Port Neches and Caplen hydrocarbon production occurred between 1940 and 1970.
dc.description.departmentBureau of Economic Geology
dc.relation.ispartofContract Reports
dc.subjectHydrocarbon production
dc.subjectfault reactivation
dc.subjectreservoir geomechanics
dc.titleEffect of Hydrocarbon Production and Depressurization on Subsidence and Fault Reactivation

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