Natural Gas Exploration in Kuqa Foreland Thrust Belt

Abstract

Abstract The Kuqa foreland thrust belt, which has superior petroleum geological conditions and lines of structural belts, is an important target for natural gas exploration in Tarim basin. But owing to the bad surface conditions, the complex deformation of the underground structures and the poor quality of seismic data here, it is difficult to define the trap and evaluate the reservoir. Since the discovery of the Kela 2 gas field and the Dina 2 gas field, there was no further progress at one time. Recently, a serie of technique research aimed at the targeting Cretaceous subsalt rocks strata in Kuqa foreland thrust belt has been carried out: The application of wide line and large geophone array seismic acquisition technique in complex mountainous areas can effectively improve the quality of seismic data; With 3D anisotropy seismic pre-stack migration technique, the seismic imaging and migration homing problem of the complex over-thrust and the irregular object is effectively resolved; The modeling technology of the compressive salt-related structures effectively guides the high and steep complicated structure interpretation; The technique of recognizing and forecasting of the thick conglomerate layer in shallow strata can be applied to build the seismic velocity field and confirm the traps. The great progress in exploration technology has enriched the geological understanding and brought about three major changes in exploration: In Kelasu structure zone, the exploration target turns to deep strata from the shallow ones; In eastern Kuqa depression, it goes to tight sand gas exploration while in the western part it switches to the lithologic hydrocarbon reservoir exploration. In this way, the subsalt layer hydrocarbon exploration has made a great breakthrough, companied with a new gas exploration upsurge. In five years, Dabei-3, Keshen-2, Keshen-5, Bozi-1, Keshen-8 and many other gas reservoirs have been found. 800 billion cubic meters of natural gas has been confirmed and about 30 important traps have been reserved. The total natural gas reserves amount has exceeded 2 trillion.