Erosion thickness recovery and its significance to hydrocarbon accumulation in northwestern Qaidam Basin

Abstract

The area from the northwestern Qaidam Basin to Yiliping is large and the exploration degree of proved petroleum reserves is low. It is of great significance for future petroleum resource assessment to recover the thickness of eroded formation. In this paper, several methods including stratigraphic trend extension, interval transit time, vitrinite reflectivity and Easy%Ro optimization were used to calculate the formation erosion thickness during the late tectonic movement in the study area, and its significance for hydrocarbon accumulation was quantitatively discussed. The Quaternary and Pliocene Shizigou Formation (N23) in the study area were generally eroded, with a maximum erosion thickness of about 1 000 m on the top of some local structures. The Upper Youshashan Formation (N22) was eroded on the top of some structures such as Youquanzi, and the Lower Youshashan Formation (N21) was eroded only at the periphery of the basin. The Yingxiongling structural belt, the top of each structure and the Altun foreland are the areas experienced the most serious erosion, generally more than 500 m of thickness. The erosion thickness in the depression and the eastern part of the study area is relatively smaller, usually less than 500 m, and the tectonic activities here are relatively stable. The distribution of petroleum reservoirs and hydrocarbon shows are closely related to the erosion thickness of sedimentary strata. The erosion thickness with appropriate strength (300-1 500 m) is conducive to the formation of oil and gas reservoirs, while an erosion thickness over 1 500 m is easy to cause damage to oil and gas reservoirs.

Keywords

• strata erosion thickness
• stratigraphic restoration
• late tectonic movement
• hydrocarbon accumulation
• yiliping area
• northwestern qaidam basin