NEW OIL IN OLD PLACES: THE VALUE OF MATURE-FIELD REDEVELOPMENT

摘要

Large reserves remain and are economically recoverable in many mature oil fields. This study documents the successful search for such overlooked reserves in old fields. Small multidisciplinary teams studied several basins in North America and a few large fields in South America, searching for large volumes of low-risk reserves in poorly performing fields. The fields studied included those producing by primary recovery, with or without secondary recovery potential, as well as fields undergoing waterflooding. In the United States, more than 350 mature oil fields were evaluated for potential purchase from 1981 to 1997. The majority of the fields were in the Permian Basin of west Texas-New Mexico and in a coastal portion of the Gulf of Mexico Basin. In addition, some large fields were studied so property owners could be advised on rejuvenating or increasing production. Finding large volumes of low-risk, presently nonproducing reserves within fields involves several steps. First, the teams search in reservoir systems that appear more massive and homogeneous than they really are. Second, the geoscience and engineering data are scanned to estimate original oil in place, percent recovery, and bypassed reserves. Third, the teams make an economic analysis, including improvement costs. Fields that are candidates for purchase have discovered low- to moderate-risk reserves amounting to at least 5% of the cumulative reserves already produced. New reserves are discovered or exploited by applying one or more of the following: (1) improved drilling and completion technology; (2) identification of bypassed pay, especially very low resistivity pay; (3) new 2-D and 3-D seismic surveys; and (4) sequence-strati-graphic concepts. Additional reserves are found in both land-derived clastic and carbonate reservoirs in mature fields. Forty-six mature fields were purchased in the Permian Basin of Texas-New Mexico and in the Gulf of Mexico Basin. In the fields purchased, 625 million barrels of oil equivalent (BOE) of proved and probable reservoirs were added at a cost of US $2.69/BOE. The average after-tax rate of return of the 46 fields is 21%. Based on these results, "exploring for new oil in old places" is an economically viable strategy for adding hydrocarbons to the world's reserves base.