Environmental hazards of urban oilfield operations

Environmental hazards of urban oilfield operations Endres et al by Bernard Endres, George V. Chilingarian, and T.F. Yen, in Journal of Petroleum Science and Engineering. 6 (1991) 95-106 Elsevier Science Publishers B.V., Amsterdam
One of the gravest dangers posed by urban oil-well drilling and production is the potential for explosive methane gas to migrate to the surface from several thousand feet underground. Unless the present-day practices are changed, under-ground migration of methane from oil and gas reservoirs will continue to pose a significant explosion threat. If the operators would systematically follow some basic preventative-management procedures, they could drill and produce safely, without prohibitive cost and in a manner that is environmentally sound. Today, unfortunately, many oil fields in urban settings are managed by catastrophe rather than preventative management. This paper discusses appropriate standards for the monitoring of surface gas seepage, and the related problems created by land subsidence due to the fluid withdrawal, as well as procedures necessary to insure the mechanical integrity of well casing and cement, necessary to protect against unwanted gas seepage. Migration of gas along faults if also discussed in this paper. … Unfortunately, these studies failed to address the increased hazards of gas migration resulting from water injection. Typically, the water injection significantly increases pressures in the reservoir causing gas to migrate to the surface along paths of least resistance. The latter can include faults, fractures, abandoned wells, and producing or idle wells lacking mechanical integrity. Thus, water injection is hazardous in a producing oilfield that also contains improperly abandoned oil wells. The basic problem of subsidence is caused by the fact that oil production causes stresses to build up in the subsurface geologic strata, increasing the prospect of formation of new fissures and faults and movement along pre-existing fault planes. This will allow gas migration of gas to the surface, substantially increasing the risk of explosion in surface structures located in the vicinity of an oilfield. … Likewise, injection of fluids into the ground for oil recovery or waste water disposal can trigger faulting. For example, on December 14, 1963, water burst through the foundation of the earth dam of the Baldwin Hills Reservoir, a hilltop water-storage facility located in metropolitan Los Angeles. The contents of the reservoir, some 250 million gallons of water, emptied withing hours onto the communities below the dam, damaging or destroying 277 homes…. It is important to mention here, that subsidence (due to the fluid withdrawal) area is twice (or more) as large as the area of the producing field. … Although most states have a regulatory agency established to oversee the oil and gas production activities within the state, including certain safety aspects, none of these agencies have developed a systematic or comprehensive program for dealing with the hazards associated with gas seepage, and land subsidence. Accidents which did occur in the past shows this to be true. … in October of 1980, a serious gas leak developed in a storage field located in Mont Belview, Texas, a suburb of the greater Houston area. The gas seepage was detected when an explosion ripped through the kitchen of a house upon starting a dishwasher. More than 50 families were evacuated from their homes as a result of the gas leak.

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