地化录井技术在莱州湾凹陷油质类型判别中的应用

Application of geochemical logging technology in discrimination of oily type in Laizhou Bay sag

不同油质的油藏录井特征差异较大,评价方法也有较大差异。莱州湾凹陷混源成藏特征明显,加之次生作用程度的不同,导致油质类型多样。通过对莱州湾凹陷12口已试油井的现场地化资料进行分析,总结出适用于该地区油质类型的定性和定量识别方法,其中前者为热解气相色谱形态法,后者为(S0+S1)/S2、∑C21-/∑C22+及主峰碳数3参数交会图板法,即通过建立相应的油质类型判别标准进行判别。应用实践证明,该方法能快速准确地判断油质类型,莱州湾凹陷随层位由浅至深,油质逐渐由重变轻,具体表现为明化镇组和馆陶组上部多为浅层生物降解重质油,馆陶组下部至沙二段多为中质油,沙三段以下地层则多为中质-轻质油。

Mud logging characteristics of oil reservoirs with different oiliness are quite different,and so are the evaluation methods.The mixed source characteristics of reservoir forming in Laizhou Bay sag are obvious,and the difference in the degree of secondary effects leads to the variety of oily types.Based on the analysis of on-site geochemical data from 12 wells that were tested in Laizhou Bay sag,the qualitative and quantitative identification methods suitable for oily types in the area were summarized,among which the former is the pyrolysis gas chromatography and the latter is 3-parameter intersection chart method of(S_0+S_1)/S_2,∑C21-/∑C22+and the main peak carbon number,that is,the discrimination can be carried through the establishment of the appropriateoily type discriminant criteria.Application practice has proved that the method can quickly and accurately determine the oily type.Laizhou Bay sag varies from shallow to deep with gradual changes in oiliness from heavy to light weight.The concrete manifestation is that the upper parts of Minghuazhen formation and Guantao formation are mostly the heavy oil of shallow biological degradation,the lower part of Guantao formation to the second member of Shahejie formation is mostly medium oil,and the formation below the third member of Shahejie formation is mostly medium-light weight oil.