Publications

Experience has shown that rock compaction will take place when an oil and/or gas reservoir is brought on production. This reservoir compaction can induce subsidence at the surface. Significant reservoir compaction may damage casing and tubing and, when the field is located offshore, seabed subsidence could harm surface facilities and endanger peoples lives. Examples of subsidence problems include Galveston Field in Houston-USA, Wilmington Field in Long Beach-USA, Bachaquero Field in Venezuela, Ekofisk Field in the North Sea, Caviaga Field in Italy, Lacq Field in France, and Groningen Field in the Netherlands.Significant subsidence can occur when some or all of the following conditions are fulfilled: (1) a significant reduction in reservoir pressure takes place during the production period, (2) production is from a large vertical interval, (3) production comes from a weakly cemented rock, and (4) the reservoir occurs at a shallow depth. Development plans should undoubtedly consider the level of compaction and subsidence to be reached by the field during the course of production. This review should include casing design and offshore platform design to reduce the risk of costly and potentially deadly accidents.Various analytical or numerical methods have been introduced by some authors (e.g., Geerstma, 1973, Bouteca et al., 1996, and Hansen et al., 1995) and combined with experiments to directly or indirectly calculate compaction and subsidence. This paper applies a method recently introduced by Morita, et al. (1973) to determine the sensitivity of reservoir parameters (such as depth, radius, and thickness) and rock properties in affecting compaction and subsidence during the depletion period. A spreadsheet calculation program was developed to facilitate estimation of compaction and subsidence estimation for any field, based on known or assumed values for reservoir parameters. Some illustrative examples illustrate the magnitude of compaction that can occur in oil, gas, and geothermal fields.