松辽盆地下白垩统营城组火山岩喷发旋回特征

松辽盆地兴城地区下白垩统营城组一段火山岩可划分为下部、中部和上部3个喷发旋回。营城组一段98%的工业气流都富集在上部旋回,该旋回便成为火山岩勘探开发的重点,而快速准确地确定上部旋回、明确各旋回的井—震标志则成为首要任务。基于关键井钻井资料及其地震反射特征的对比分析,建立了火山岩喷发旋回的井—震标志:①下部旋回的岩性以酸性岩为主,含中基性岩,喷溢相占90%;部分井段伽马值小于90API;地震特征为席状—盾状—锥状、中—强振幅、中高频、连续性好。②中部旋回的岩性以酸性岩为主,发育少量的中性岩,喷溢相占79.5%;伽马值多为90～160API;地震特征为丘状—透镜状—穹隆状—板状、中弱振幅、中低频、连续性中—好。③上部旋回的岩性为酸性岩,喷溢相占47.1%、爆发相比例大幅度提高;伽玛值多为130～260API;地震特征为丘状—楔状—席状、中弱振幅、中低频、连续好—差。上述火山岩喷发旋回的井—震标志也为快速找准邻区火山岩勘探目的层提供了依据。

Characteristics of volcanic eruption cycles of the Yingcheng Formation in the Songliao Basin

The volcanic rocks in the first member of the Yingcheng Formation in Xingcheng area, Songliao Basin, can be divided into three eruption cycles, including lower, middle and upper cycles. In the first member of the Yingcheng Formation, 98% of the industrial gas flow is obtained in the upper cycle. Therefore, the upper cycle is the primary target of volcanic reservoir exploration and development, and the primary task is to define the well seismic correlation marks of each cycle. ①The lower cycle is dominated by acidic rocks and contains some intermediate and basic rocks. Effusive facies occupies 90%. The GR value of some intervals is less than 90API. The seismic reflections are in sheet shield cone shape and feature in medium high amplitude, medium high frequency and good continuity. ②The middle cycle is dominated by acidic rocks and contain minor intermediate rocks. Effusive facies occupies 79.5%. The GR values are mostly in the range of 90 160API. The seismic reflections are in mound, lenticular, dome or slab shapes and feature in medium low amplitude, medium low frequency and fair good continuity. ③The upper cycle is completely acidic rocks. Effusive facies occupies 47.1%, while the percentage of eruptive facies increases remarkably. Most of the GR values are in the range of 130 260API. The seismic reflections are in mound, wedge or sheet shapes,  featured by medium low amplitude, medium low frequency, good poor continuity. The well seismic correlation marks of the volcanic eruptive cycles also provide bases for rapidly identifying exploration targets of volcanic rocks in the adjacent blocks.