Geology and Hydrocarbon Accumulation of the Large Ultra-Deep Rewapu Oilfield in Tarim Basin, China

Abstract

Over the past five years, oil and gas exploration to marine facies carbonate rock in China took on a fast-growing tendency, and a lot of large-scale oil and gas fields were discovered in succession. Particularly in the north of Tarim Basin, the large-scale Rewapu oil field was recently discovered in the Ordovician carbonate rock layer system with buried depth of 7,000 meters, manifesting that a significant potential of exploration exists in Tarim Basin's deep layer and ultra deep layer of Tarim basin. The results indicate that reservoirs of Rewapu oilfield are low porosity and low permeability layers karst reservoirs, reservoir temperature is around at 160 ℃ with oil, and the crude oil comes from the upper Ordovician source rock of the Manjaer depression. The hydrocarbon accumulation time is in the Late Permian, and since the Triassic sedimentation, the reservoir is in the continuous process of burying. It belongs to the old oil and gas system. Due to low geothermal gradient and late quick deep burial, oil reservoir has yet to be cracked, so well-preserved old oil reservoir can be discovered at the depth of 7000 m. The Ordovician carbonate reservoir in Rewapu was a fracture-cavity oil reservoir, and the oil and gas distribution and enrichment are controlled not by the local structure, but by the distribution and the development degree of Ordovician carbonate reservoir. The reservoirs of Rewapu block are mainly distributed in the Ordovician Yijianfang formation and at the top Yingshan formation, and the reservoir development degree was controlled by the karstification, the degree of fracture development and the sedimentation facies, concentrating into belts in plane and not controlling by the depth vertically. The overlying strata are limestone of Tumuxiuke formation and marls and limestone of Sangtamu formation in the upper Ordovician. Rewapu oil reservoir features stratified oil and mainly contains normal oil with low viscosity and high wax. Research results show that Ordovician reservoirs in Rewapu block have relatively large depth of burial, but they are still favorable in quality and sit along the path for the oil and gas's northward migration. Therefore, this block has immense resources potential and boasts good exploration and development outlook. In this paper, we study Rewapu block oil reservoir's geological features and hydrocarbon accumulation mechanism, which is of important significance for directing the exploration to oil and gas at the deep layer and ultra deep layer of Tarim Basin.

Characteristics and formation mechanisms of silicified carbonate reservoirs in well SN4 of the Tarim Basin

“…The reservoirs of some high-yield gas wells are generally located near the transition zone between the dolomite and limestone of the Yingshan Formation (GL1, GC6, GC8, and GC9). Studies have suggested that the natural gas originated mainly from the Manjiaer sag (Zhu et al., 2015b) and entered the Yingshan reservoirs from bottom to top along faults. The period of natural gas accumulation was relatively late, mainly during the Yanshanian period (Wang et al., 2014a; Yun and Cao, 2014).…”

The geochemical characteristics of Tazhong crude oils from the Tarim Basin, northwestern China

“…The fact that large volumes of light crude oil have been extracted from the Tazhong (TZ) area within the Tarim Basin highlights the great potential for massive petroleum exploration from deep layers in this region (He et al, 2016;Wang et al, 2014). Zhu et al (2015) reported the newly discovered Rewapu oilfield in Tarim Basin, which was well preserved due to low geothermal stress and quick deep burial. Wang et al (2015) analyzed sulfur-containing compounds in Ha9 and ZS1C crude oils, identifying DBT (dibenzothiophene) series compounds in Ha9 crude oil and thiadiamondoids with 1-3 cages in ZS1C crude oil.…”

Studies on thermal maturity and hydrocarbon potential of lignites of Bikaner–Nagaur basin, Rajasthan

“…Hydrocarbon resource of a basin is related to source rock, depositional, and tectonic structures and thermal maturation of the organic matter (Yang et al, 2014;Zhu et al, 2015). Contributions have been made by Demaison (1980), Dembicki et al (1983), Mishra and Cook (1992), Peters (1986), Singh and Singh (1998), and Teichmuller and Durand (1983).…”

“…With progress in the coalification, not only the rank changes, but there is also change in the chemical composition and properties of the macerals. Hydrocarbon resource of a basin is related to source rock, depositional, and tectonic structures and thermal maturation of the organic matter (Yang et al., 2014; Zhu et al., 2015). Contributions have been made by Demaison (1980), Dembicki et al.…”