Hydrocarbon enrichment characteristics and difference analysis in the TZ1–TZ4 well block of the Tarim Basin

Abstract

The reservoirs in the TZ1–TZ4 well block of the Tarim Basin are complex, and the hydrocarbon enrichment shows differences. The three Carboniferous oil layers are characterized by “oil in the upper and lower layers and gas in the middle” in profile and “oil in the west and gas in the east” in plane view. In order to discuss the complex reservoir accumulation mechanisms, based on the petroleum geology and reservoir distribution, we studied the generation history of source rocks, the fault evolution and sealing, the accumulation periods and gas washing, and reconstructed the accumulation process of the TZ1–TZ4 well block. It is concluded that the hydrocarbon enrichment differences of oil layers CIII, CII and CI were caused by multiple sources and multi-period hydrocarbon charging and adjustment. The CII was closely related to CIII, but CI was formed by reservoir adjustment during the Yanshan period and was not affected by gas washing after it was formed. During the Himalayan period, different degrees of gas washing in the east and west led to hydrocarbon enrichment differences on the plane. The Carboniferous accumulation process of two-stage charging and one-stage adjustment is summarized: oil charging during the late Hercynian period is the first accumulation period of CIII and CII; oil reservoirs were adjusted into CI in the Yanshan period; finally gas washing in the Himalayan period is the second accumulation period of CIII and CII, but CI was not affected by gas washing. This complex accumulation process leads to the hydrocarbon enrichment differences in the TZ1–TZ4 well block.