The Discovery and Development of SZ 36-1 Oil Field in Liadodong Bay

ABSTRACT The Suizhong 36–1 oil field is a large heavy oil field, characterized by loose oil reservoir, strong heterogeneity, high viscosity and low oil/gas ratio. Thus, the development of this field is facing a technical challenge with great difficulties. In order to minimize the risk, the Bohai Oil Corp. of China National Offshore Oil Corp. (CNOOC) think it necessary to open up a pilot test area to start with. This paper focuses the determination of the pilot area, well completion, selection of artificial lifts and the design of engineering facilities, etc., by starting with the discussion on the basic geological characteristics of the field. The paper introduces the decisions taken by BOC for solving the problems in the development of this field and measures to improve the economics. PREFACE Being located in the Liaodong Bay in the eastern part of Bohai Gulf, the SZ 36–1 oil field is in the Liaodong Bay depression, which is geologically one part of the Bohai Gulf petroliferous province in Eastern China. The field is about 59KM from shore in its west, in an area with water depth of 32m, where the water is not frozen in winters, but floating ice does occur for a short period in a year (Figure 1 & 2). The Liaodong Bay is being explored and developed by BOC, mainly relying on China's own capital investment, technology and operation staff. In 1986, SZ 36–1–1 well was completed on the central crest of SZ 36–1 prospect, and oil flow was tested from Pre-Mesozoic top with 190,000 cubic meters of gas/day produced from the lower Tertiary Dongying formation. In 1987, SZ 36–1–2D well was completed on the south crest of the same prospect, resulting in productive oil discovery with a rate exceeding 100 tons from a sandstone reservoir in the lower part Dongying formation, which was followed by 4 appraisal wells at the top and on the flanks of this crest. Oil flows were tested from all four wells with varying productivities. New oil bearing traps were found on the down-thrown side to the west of the field and on the eastern slope by drilling in 1988. It has been proven that the oil field has an oil in place of 165 million cubic meters, probable reserve of 84 million cubic meters and possible reserve of 22 million cubic meters. Hence it can be classified as a giant field according to its reserve amplitude. Since the exploration is still continuing in the field, the size of the field would be further expanded in the hope of new oil accumulations to be found in the adjacent traps and in the deeper horizon. Sited in the middle portion of Liaoxi low relief uplift in Liaodong Bay - Lower Liaohe depression in the Bohai Gulf basin, the SZ 36–1 oil field runs NNE-SSW with a width of 70KM from the east to the west and a length of 180KM from the North to the South, and is composed of two uplift is fault bounded with Liaoxi sag in its west and is in a slope transit to Liaozhong sag in its east. (Figure 4).