准噶尔盆地阜康断裂带上盘二叠系芦草沟组页岩油地质特征及勘探潜力

Geological characteristics and exploration potential of shale oil of Permian Lucaogou Formation in hanging wall of Fukang fault zone,Junggar Basin

利用露头、岩心薄片及地球化学分析资料,对准噶尔盆地阜康断裂带上盘二叠系芦草沟组的岩性、沉积古环境、烃源岩评价及分布特征进行了研究,并探讨了成藏模式。研究结果表明:(1)阜康断裂带芦草沟组发育砂岩、泥页岩、碳酸盐岩等多种岩性,以灰黑色、黑色油页岩为主,厚度为200~600 m,见碳酸盐岩与泥页岩互层,碳酸盐岩夹层中可见沥青、油迹。(2)研究区芦草沟组沉积时期为半深湖—深湖相,气候以干热为主,间歇性出现温湿气候,古水体为微咸水—咸水;博格达山北麓为沉积湖盆的中心,具有更好的沉积和保存条件。(3)研究区烃源岩有机质丰度高,野外露头岩心Ro值为0.74%~1.28%,钻井岩心TOC值为0.92%~4.48%,主要为Ⅰ和Ⅱ1型,成熟度较高,生烃潜量大,S1+S2多大于20 mg/g,为成熟优质烃源岩;博格达山北麓比西侧烃源岩发育规模更大,成熟度更高,氯仿沥青“A”含量多高于1 200×10-6。(4)研究区芦草沟组油藏受控于圈闭和断层,北部高陡带油藏多出露地表,遭受破坏,以稠油为主,中部鼻隆带构造稳定,发育8处圈闭;中部鼻隆带油藏表现出自生自储、多期充注的特征,区域内东南部为页岩油勘探的“甜点”区。

Based on outcrops,cores and geochemistry analytical data,the lithologies,sedimentary paleoenvironment,the evaluation and distribution characteristics of source rocks of Permian Lucaogou Formation in the hanging wall of Fukang fault zone in Junggar Basin were analyzed,and the hydrocarbon accumulation model was discussed.The results show that:(1)There were sandstone,shale and carbonate rocks developed in Lucaogou Formation in Fukang fault zone,and they were dominated by gray-black and black oil shale with thickness of 200-600 m.The carbonate rocks and shale were interbedded,and asphalt and oil traces can be seen in carbonate interbeds.(2)The Lucaogou Formation in the study area was deposited during the semi-deep lake to deep lake facies,the climate was mainly dry and hot,with intermittent warm and wet climate,and the ancient water body was brackish-saline water.The northern foot of Bogda Mountain was the center of the sedimentary lake basin,which has better deposition and preservation conditions.(3)It was a high mature and high-quality hydrocarbon source rock with abundance of organic matter in the study area,with outcrops Ro of 0.74%-1.28%and drilling core TOC of 0.92%-4.48%.They are mainly typeⅠandⅡ1 and have high hydrocarbon potential,with S1+S2 greater than 20 mg/g.The hydrocarbon source rocks at the northern foot of Bogda Mountain has a larger scale of development and higher maturity than that in the western side,and the chloroform asphalt“A”content is greater than 1200×10-6.(4)The reservoirs of Lucaogou Formation in the study area are controlled by traps and faults.The reservoirs in the northern high steep zone are mostly exposed on the surface,damaged,and dominated by thick oil.The central nasal ridge zone is tectonically stable,with eight traps developed.The reservoirs in the central nasal ridge zone are characterized by self-generation and multi-phase filling.The southeastern part can be designated as the sweet spot area for shale oil exploration.