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Summary The Sarmatian 3 Videle field is among the largest heavy-oil reservoirs currently known in the world. The oil viscosity under reservoir conditions ranges from 30 to 120 cp [30 to 120 mPa s]. There are three producing horizons: Sarmatian 3a and 3b, partially overlying Sarmatian 3c. producing horizons: Sarmatian 3a and 3b, partially overlying Sarmatian 3c. The field was discovered in 1959. During 1964 to 1976, a water-injection project was gradually expanded to the whole reservoir area. The average oil recovery at the present time is about 13%, and the producing wells are approaching the economic limit-the producing oil/water producing wells are approaching the economic limit-the producing oil/water ratio is higher than 25. For this reason, it was decided to study the feasibility of producing the field by in-situ combustion to recover additional tertiary oil. To obtain the necessary data, three field combustion pilots located upstructure in various areas of the reservoir are being operated. The performance of the three tests is presented and discussed. The favorable performance of the three tests is presented and discussed. The favorable results obtained so far justify the full-scale application of the in-situ combustion process. A linedrive scheme has been selected so that a more or less continuous combustion front will move downdip. To supply the necessary air for a combustion front of more than 11.2 miles [18 km] in length, a giant compression capacity of about 247.2 × 10 6 scf/D [7 × 10 6 std m3/d] will he required.
Introduction On the basis of the successful combustion operations conducted fieldwide at suplacu de Barcau, as well as the favorable results obtained by the in-situ combustion experiment in the Balaria field, a study has been undertaken to determine the feasibility of the in-situ combustion process in the Videle field. The Sarmatian 3 Videle and Balaria fields are located near each other and have similar rock and fluid characteristics. Their reservoir drive mechanisms, however, are different; while Balaria produces under natural water drive, the water drive in the Videle field is so weak that a water-injection project had to be applied. An in-situ combustion test was started in 1975 in the Balaria Sarmatian reservoir. After 4 years, the favorable results obtained led to the decision to expand the combustion test to a full-scale project. This paper presents the results obtained in the in-situ combustion tests performed in the Videle field as a tool for increasing oil recovery in a relatively heavy-oil reservoir produced by peripheral and internal water injection. The basic ideas of expanding the in-situ combustion process to full-scale operations are discussed. process to full-scale operations are discussed. Geology and Reservoir Properties
The Videle field is located in the southern part of Rumania, about 72.4 miles [117 km] west-southwest of Bucharest. The Videle structure is a monocline 11.2 miles [18 km] long with about a 2.5-mile [4-km] lateral extent. A typical well log is shown in Fig. 1. The Sarmatian 3 Videle field consists of three producing horizons, Sarmatian 3a ( ), Sarmatian 3b ( ), and Sarmatian 3c ( ). Oil is being produced unsegregated from the first two (upper) intervals, 3a and b. The Sa and the Sa are either massive facies or are separated by discontinuous impermeable stringers, forming the pay zone Sa. The Sa is separated from S by an impermeable sequence of clayey layers, ranging from 20 to 46 ft [6 to 14 m] in thickness and extending over the whole surface of Sa. The productive zones range from 2,132 to 2,789 ft [650 to 850 m] and consist of slightly consolidated medium-to-fine-grained sand in Sa and loose, fine-to-very-fine-grained sand in Sa. Sa and Sa are not present in all field areas. Because the Sarmatian Sea overlapped the Cretaceous relief eroded earlier, the aforementioned horizons gradually disappear eastward. The intercommunicating blocks of the Sa, the limits of the Sa and of the Sa, and the location of the Videle reservoir relative to the Balaria reservoir are shown in Fig. 2. A schematic section of the West Videle field is shown in Fig. 3. In East Videle, the Sa strata rest directly on Cretaceous formations. A gradual increase in oil viscosity from west to east is evident in Sa the net pay thickness and the permeability are decreasing in the same direction. The rock is oil-wet both in Videle and in Balaria. The main properties of the strongly undersaturated heavy oil of the Sa Videle and of properties of the strongly undersaturated heavy oil of the Sa Videle and of the Sa Balaria are given in Table 1.
SPEFE
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