塔里木盆地二叠纪火山—岩浆活动对古生界生储条件的影响——以塔中47井区为例

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

塔里木盆地古生界地层是油气勘探的重要层段,勘探开发实践证明,古生界地层中的生储盖组合及油气体系受到了二叠纪大量、长期、多阶段火山—岩浆活动的强烈影响,然而,其影响规律尚不清楚。研究选取塔中47井区的三口重点油气探井,对志留系—石炭系油砂样品进行气相色谱—质谱分析,并完成了砂岩的成岩作用及储集空间研究,结合井区三维地震解释,从有机质、储层、成藏等方面研究了二叠纪火山—岩浆活动对古生界生储条件的影响。结果表明,塔中47井所钻遇的大型火山机构,其火山—岩浆活动可以提高下伏地层中有机质的成熟度,增强储层中酸性流体对钙质胶结物的溶蚀作用,促进次生孔隙形成进而发育优质储层。靠近火山机构的油气储层受改造作用更强烈,其储集性能更好,以火山机构为中心,横向上依次分布储层显著改善区域、储层破坏区域和储层基本未受影响区域,储层改善作用的影响范围大约为6 km。储层演化与油气综合成藏与二叠纪火山—岩浆活动有一定的对应性和关联性,火山—岩浆活动直接促进了油气运移和油气藏的形成。

Paleozoic elastic 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 voleanic-mag- matie aetivities can inevitably and strongly influence the underlying strata and oil and gas generating and storing condi- tions. However, this influence law is not clear. Based on 3-D seismic interpretation of Tazhong 47 well area, Gas Chromatography-Mass Speetrometry analysis of Silurian-Carboniferous oil sands, as well as detailed observation and thin section porosity evaluation of sandstone easting thin sections of three crucial wells in Tazhong 47 well area, this paper investigated the influence law of volcanic-magmatic activities on Paleozoie 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 voleanie-magmatic activities enhanced the maturity of organic matter in underly- ing 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 later- ally 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 reser- voir forming and can be favorable for hydrocarbon accumulation.