Oil-source Fine Correlation And Transportation System Research Of Composite Reservoirs Around Halahatang Depression

Around Halahatang depression was a typical"composite hydrocarbon accumulation play". Precise oil correlation was the foundation for identifying source of oil and gas, charging times and migration directions, and was an important aspect of composite reservoirs study. It could also identify hydrocarbon migration system effectively, and provide direct evidence for oil-gas distribution and controlling factors analysis.The type classification of crude oil based on physical properties, geochemical behavior and carbon isotope analysis etc., had an important significance for better understanding of the distribution of different types of crude oil and various source rocks. Crude oil in this region could be classified into marine oil and terrestrial oil. Marine oil had high density and high content of dibenzothiophene, low content of rearranged terpane and sterane series and light isotope value compared with the terrestrial oil. The terrestrial oil included two different types of oil, lacustrine oil and coal oil. While marine oil were also derived from two different source rocks, Cambrian-Lower Ordovician ones and Middle-Upper Ordovician ones.The mixed marine oil distributed widely in study area, and were studied for qualitative research to meet the precise needs. According to mixed oil matching experiment, which with different Cambrian oil ratio, this paper established dependence between mixing ratio and biomarker parameter, to calculate quantitatively Cambrian oil proportion in mixed oil, and then studied the distribution and formation mechanism. The proportion of the Cambrian oil in the mixed oil increased gradually from west to east and shallow to deep in the study area, the mixed oil with high Cambrian-Lower Ordovician proportion was mainly concentrated in eastern Sangtamu fault belt and around Lundong fault of Lunnan area.According to nature of marine oil, this paper studied the geochemical processes and hydrocarbon accumulation, took the acidic features of marine oil in Lunnan area as an example. In horizontal, acid value was "west high and east low". According to oil physical properties, geochemical characters and accumulation processes, the formation and changes of acid value of crude oil was related to two main geochemical processes. Biodegradation made acid value of crude oil increased, and gas cutting changed the distribution of acid value of crude oil in Lungudong area. Based on biomarkers analysis, the acidiferous oil was mixing origin in this area, which was consistent with analysis results of hydrocarbon accumulation.The nature of oil and gas were mainly affected by two main geochemical process and the accumulation and adjustment processes of"three sources and three periods", this paper took the study of oil and gas accumulation in Silurian as an example. "Three sources" refered to oil and gas came from two sets of marine source rocks of Cambrian and Middle-Upper Ordovician and a set of terrestrial source rock of Triassic in Kuqa depression. "Three periods" refered to three accumulation-adjustment-reconstruction periods of late Caledonian, late Hercynian and late Himalayan. This three periods of hydrocarbon injection and tectonic movement determined the complexity and diversity of oil and gas.