Analysis of secondary migration of hydrocarbons in the Ordovician carbonate reservoirs in the Tazhong uplift, Tarim Basin, China

Abstract

The process and mechanisms of secondary hydrocarbon migration in the Tazhong uplift, Tarim Basin, were investigated based on the analysis of the regional structure and by integrating geologic, hydrodynamic, and geochemical parameters. Parameters successfully analyzed included the fluid potential, fluid properties, production outputs, and diamantane index. The results indicated that hydrocarbons migrated into the Tazhong uplift from the northern part of the Manjiaer depression through a series of injection points (IPs) during four orogenies, that is, the early Caledonian (510 Ma), the late Caledonian (439 Ma), the late Hercynian-Indosinian (290 Ma), and the Yanshanian-Himalayan (208 Ma). A total of six IPs were identified at the intersections of the northeast-trending faults and the northwest-trending flower strike faults. The hydrocarbons migrated from the IPs into traps along regional trends from northwest to southeast and from northeast to southwest. The hydrocarbon migration process and patterns determined the distribution of hydrocarbon properties and production rates in the Tazhong uplift. With increasing distance from the IPs, daily hydrocarbon production decreases, and the hydrocarbons become progressively heavier and display lower gas:oil ratios.

Geochemistry of alkylbenzenes in the Paleozoic oils from the Tarim Basin, NW China

“…Oil and gas accumulations occur in the Cambrian-Ordovician carbonates and in the overlying sandstones. Multiple charges and various secondary alterations including biodegradation, evaporative fractionation, thermal cracking and thermochemical sulfate reduction may have altered these accumulations (Xiao et al, 2000;Zhang et al, 2000Zhang et al, , 2011Zhang et al, , 2014Li et al, 2010;Zhu et al, 2012;Pang et al, 2013).…”

Origins and accumulation processes of the Ordovician gas condensate in the Tazhong area, Tarim Basin, northwest China

“…These results suggest that oils derived from the Є 1+2 source rocks primarily accumulated along the No. 1 Fault Belt during the early filling stage, where intersections of northeast direct strike‐slip faults and the No.1 Fault are the hydrocarbon injection points ( Pang et al, ). On the contrary, rare Є 1+2 ‐derived oils accumulated in zones away from the No.…”

Secondary migration of hydrocarbons in the Zhujiang Formation in the Huixi half-graben, Pearl River Mouth Basin, South China Sea

“…The fluid potential field in a basin is mostly determined by the morphology of carrier beds, and any identification of migration directions using the fluid potential gradient requires the delineation of compartmental troughs in the potential fields within the area of interest (Liu et al 2002;Pang et al 2013). As the geographical divides or ridges separate regions of differing drainage, the compartmental troughs separate different hydrocarbon accumulation units.…”

“…The processes of hydrocarbon generation, migration, accumulation, degradation, and dispersion can all change oil properties (Pang et al 2013;Chen et al 2014). Because most of the hydrocarbons in the reservoirs were injected on one side, along the principal direction of migration, it can be inferred that crude oil composition changes with the gradient (Hwang et al 1994;Lin and Zhang 1996).…”

“…However, it is also a challenge for petroleum research because of the lack of direct geological evidence and the extreme conditions required for experimental physical simulation of hydrocarbon migration (Pang et al 2013;Chen et al 2014). Although the mechanism of secondary hydrocarbon migration has been studied, the preferred pathway and main controlling factors are still unclear.…”