准噶尔盆地中部1区块三工河组基准面旋回划分

Division of base level cycle of Sangonghe Formation in block 1,central Junggar Basin

准噶尔盆地中部1区块(准中1区块)侏罗系三工河组是陆相地层油气勘探的热点层位。在三工河组沉积时期,准中1区块沉积了一套较为稳定的浅水三角洲—滨湖相地层。准噶尔盆地在早侏罗世处于张性构造环境,盆地具有盆大、水浅和坡缓等沉积特征,在盆地腹部的地震剖面中较难进行高分辨率层序地层对比。通过对自然伽马测井曲线进行小波变换和合成预测误差滤波分析,实现高分辨率层序地层划分。在单井中识别出小波变换最佳尺度因子(a),分别对应短期旋回、中期旋回和长期旋回,尺度因子的能量越大,自然伽马测井曲线值变化越剧烈,判定为水进面或者水退面。基于合成预测误差滤波分析技术,三工河组中识别出负拐点和正拐点,负拐点指示层序界面,也有可能是最大水泛面;正拐点指示初始水泛面。依据合成预测误差滤波曲线的负趋势和正趋势,判别沉积地层的旋回性。准中1区块三工河组基准面分析,证实了小波变换和合成预测误差滤波分析在沉积环境稳定的陆相地层研究中具有较好的适用效果和应用前景。根据基准面旋回的变化分析沉积过程,指出三工河组二段是主要砂体发育层位,是重点的勘探方向。

The Sangonghe Formation(Junzhong block 1) in central Junggar Basin is an important exploration area for oil and gas in continental strata. During the sedimentary period of Sangonghe Formation, Junzhong 1block deposited a set of relatively stable shallow water delta-lakeside facies strata. The Junggar Basin was in a tensional tectonic environment during the Jurassic sedimentary period. The basin has the sedimentary characteristics of large basin, shallow water and slow slope, so it is difficult to determine the high resolution sequence stratigraphic ratio in the seismic profile of the basin abdomen. The method of wavelet transform and synthetic prediction error filtering analysis of GR logging curve, is used by high resolution sequence stratigraphy division.The optimal scale factor(a) of wavelet transform was identified in a single well, corresponding to short-term cycle, medium-term cycle and long-term cycle respectively. The larger the energy of scale factor was, the more drastic the change of GR logging curve value was, and it was determined as water inflow surface or water retreat surface. Based on synthetic predictive error filtering, negative inflection point and positive inflection point are identified in the Sangonghe Formation. The negative inflection point indicates the initial water flooding surface, and the positive inflection point indicates the maximum water flooding surface. According to the negative trend and positive trend of synthetic prediction error filter curve, the cyclicity of sedimentary strata can be distinguished. The base level analysis of Sangonghe Formation in Junzhong 1 block confirms that wavelet transform and synthetic prediction error filtering analysis have good application effect and application prospect in continental strata research. Based on the analysis of sedimentary process of base level cycle, it is pointed out that the second member of Sangonghe Formation is the main sandbody development horizon and is the key exploration direction.