测井—地化结合法探讨南堡凹陷潜山源控藏作用

Controlling of Hydrocarbons Expulsion of Source Rock on Buried Hill Hydrocarbon Reservoir in Nanpu Depression by Acoustic Logging Methodology

渤海湾盆地南堡凹陷潜山已发现数口工业油气流井,深部潜山油气资源丰富,但该区潜山勘探一直存在有利区预测困难的难题。潜山上覆烃源岩的排烃分析可提供潜山油气勘探的重要依据,传统的排烃研究需大量钻井取样与样品分析测试数据,尝试利用声波时差与地球化学结合途径,研究烃源岩的排烃作用并预测有利潜山含油气区。通过对典型井的声波测井与地球化学研究,建立了南堡凹陷声波测井—地球化学指示排烃综合模型,应用该模型对南堡油田33口探井进行了排烃研究。结果表明,南堡油田2号、3号构造带潜山上覆烃源岩下排烃厚度最大、南堡1号构造带局部下排烃,4号与5号构造带潜山上覆烃源岩下排烃作用不太明显。以上排烃分析与目前潜山发现油气的分布相吻合,反映烃源岩对潜山油气有很强的控制作用。南堡凹陷潜山源控藏作用受控于烃源岩与潜山的接触关系、烃源灶位置、烃源岩成熟度、烃源岩中火山岩隔层与断层的发育等多种因素。综合排烃识别结果、源控藏分析等,预测潜山勘探有利区为南堡2-3号构造带,其次为南堡1号构造带。声波测井在排烃中的应用对于潜山油气勘探具有重要意义。

Industrial petroleum was discovered from Palaeozoic deep horizons in the Nanpu Depression, Bohai Bay Basin, which suggests significant deep petroleum potential in the area. One of the issues in exploration is forecasting favorable place for prospecting in the area. Hydrocarbons expulsion downward from the source rocks immediately overlapped buried hill should be useful in this aspect. Acoustic logging combined with geochemical approaches was utilized in this study to identify hydrocarbons expulsion and evaluate hydrocarbon potential. Af- ter a detailed correlative acoustic logging and geochemical study, a combined hydrocarbons expulsion model of the source rocks in the Nanpu Depression was established, which was used to investigate hydrocarbons expulsion of the source rocks from 33 wells in the Nanpu Depression. The results suggest that the average depths of the source rocks with the hydrocarbons expelled downward into the burial hill in the No. 2 and 3 Tectonic Belts are about 248 m and 358 m, respectively, and only 35 m for the No. 1 Tectonic Belt. No obvious hydrocarbons ex-pulsion into burial hill was observed in the No. 4 and 5 Tectonic Belts in the depression. This result coincides with the hydrocarbons discovered up to now in the burial hills. We suggest that these factors including contact style between the source rock and the burial hill, the position of the hydrocarbon kitchen, the thermal maturity of the source rocks, the volcanic rock acting as barrier bed and faults developed, have a controlling of the amounts and characteristics of the hydrocarbons expelled by the source rocks and charged into the burial hill in the Nanpu Depression. A comprehensive study of hydrocarbons expulsion, migration and accumulation indicate that the No. 2 and 3 Tectonic Belts and next the No. 1 Tectonic Belt are prospective areas with burial hill hydro- carbons reservoir developed. This study also indicated that acoustic logging could be an important tool identif- ying hydrocarbons expulsion and would be useful in petroleum exploration.