STRUCTURE AND HYDROCARBON POTENTIAL OF THE TARIM BASIN (NW CHINA) FROM SATELLITE IMAGERY

The Tarim Basin, NW China, whose total area is 560,000 sq. kms, is one of the largest inland basins in the world, with sediments around 15,000 m thick. The Tarim Block is a small continental plate, which is being over-ridden at its western end from both the north and south, by the Eurasian and Indian continents, respectively. Abundant oil and gas accumulations are predicted to occur within the basin. Detailed analysis of Landsat imagery, integrated with published geological and geophysical data, has provided the basis for a re-examination of the structural geology of the area, and has enabled a new interpretation of the tectonic development of the northern part of the Tarim Basin to be made. The region discussed in this paper is the northern margin of the Tarim Basin, including the Kalpin Uplift (Kalpintag), North Tarim Depression and Kuruktag Uplift. Remarkable geological structures outcrop in these areas, and are clearly visible on satellite imagery. The NW and SW margins of the Tarim Basin are dominated by compression; while the NE and SE margins are dominated by left-lateral strike-slip movements. South of the Kalpintag, west-directed thrusting occurs in Palaeozoic platform sediments, which may have some production potential where they are buried beneath Neogene sediments. On the NW basin margin; where thrusting is predominant, crustal shortening is estimated to be around 50%. In the Kuqa Depression (the northern sector of the North Tarim Depression), Tertiary evaporites seal Mesozoic source rocks. The configuration above the décollement is discordant, and the spectacular Tertiary surface structures are not very prospective. The Kuruktag (at the NE corner of the Tarim Basin) is an area of compressional grabens which may contain both Mesozoic and Tertiary source rocks. These grabens are potential analogues of basins in southern California. Important structural features interpreted here include several major thrust complexes, and strike-slip fault systems. In addition to detecting fault traces, a number of important fold structures were mapped and analysed using the imagery, and the resulting maps represent an improvement on existing publications. Tectonic features, particularly folds and faults near the basin margin, may provide traps for hydrocarbon accumulations. As a result of this study, many potential hydrocarbon traps, which merit close attention by geophysical field-survey techniques such as seismic reflection, have been defined.