Effects of Permian Volcanic-Magmatic Activity on the Paleozoic Oil and Gas Generating and Storing Conditions in the Tarim Basin: A case study of Tazhong-47 well area

Key words: 
• Tarim /
• Permian /
• volcanic-magmatic activity /
• Paleozoic /
• organic matter /
• reservoir improvement /
• hydrocarbon accumulation /

Abstract: Paleozoic clastic sedimentary strata of  the Tarim Basin are important oil and gas exploration zones. Permian volcanic rocks are widely distributed in  the  Tarim Basin, and the abundant, long-term and multistage volcanicmagmatic activities can inevitably and strongly influence the underlying strata and oil and gas generating and storing conditions. However,  this influence law is not clear. Based on 3-D seismic interpretation of Tazhong 47 well area, Gas Chromatography-Mass Spectrometry analysis of Silurian-Carboniferous oil sands, as well as detailed observation and thin section porosity evaluation of sandstone casting thin sections of three crucial wells in Tazhong 47 well area, this paper investigated the influence law of volcanic-magmatic activities on Paleozoic oil and gas generating and storing conditions from organic matter, reservoir and accumulation aspects. The results show that a large volcanic edifice was drilled by Well Tazhong 47. Permian volcanic-magmatic activities enhanced the maturity of organic matter in underlying sedimentary strata, boosted the dissolution of the calcareous cements in the reservoir by acidic fluid and promoted pore formation and the development of high quality reservoir. The improvement of reservoir properties can be notable with intenser volcanic activities influences and influence scope of reservoir improvement is within about 6km from the volcanic edifice. From volcanic edifice to outside, good reservoir, poor reservoir and reservoir of background are laterally distributed respectively. Reservoir evolution and integrated accumulation has some correspondence and correlation of Permian volcanic-magmatic activities, which can directly contribute to hydrocarbon migration and oil and gas reservoir forming and can be favorable for hydrocarbon accumulation.