基于高分辨率层序地层学的大庆长垣南部浅层气分布特征研究

SHALLOW GAS DISTRIBUTION CHARACTER OF THE HEIDIMIAO RESERVOIR IN THE SOUTHERN DAQING PLACANTICLINE BASED ON HIGH-RESOLUTION SEQUENCESTRATIGRAPHY

松辽盆地大庆长垣南部黑帝庙油层具有良好的浅层气开发潜力。应用高分辨率层序地层学原理,通过对各级基准面旋回结构、叠加样式的沉积动力学分析,利用1164口测井曲线和6口井岩芯资料,把松辽盆地大庆长垣南部黑帝庙油层划分为1个长期基准面旋回、4个中期基准面旋回、25个短期基准面旋回,提出了研究区北部为后期构造抬升而缺失的层序地层新格架。短期基准面旋回内储层沉积特征及单砂体展布规律研究表明:黑帝庙油层为松辽盆地北部物源控制的湖盆逐渐萎缩背景下形成的河控缓坡三角洲前缘亚相沉积体系,微相类型以水下分流河道、河口坝和远砂坝为主。依据区域性湖侵成因的9套暗色泥岩盖层把黑帝庙油层垂向上划分为9套储盖组合;生储盖组合特征及动态资料综合分析表明浅层气主要分布于长期旋回下降早期的中期旋回下降晚期或上升早期储层砂体中;单砂体展布规律与气源断层和构造的合理匹配是浅层气富集的主控因素,气藏类型主要为构造—岩性、断层—岩性圈闭,在以上研究的基础上应用气水解释模板在全区预测地质储量,其研究对指导整个松辽盆地北部浅层气勘探与开发具有重要理论意义和实际应用价值。

The Heidimiao Reservoir of Daqing Placanticline in the Songliao Basin has excellent development potential for shallow gas. Applying high-resolution sequence stratigraphic theory, we analyzed the sediment and superposition styles at various scales based on 1164 loggings and 6 cores. We divided the Heidimiao Reservoir of Daqing Placanticline into 1 long-term,4 intermediate-term and 25 short-term base-level cycles, and proposed a new sequence stratigraphic framework of the study area. The absence of some sequence stratigraphic unit in the northern part of the study area was due to tectonic uplift. The study of the sedimentary features of reservoirs and distribution of single sandbodies in short-term base-level cycles shows that （1） the Heidimiao Reservoir belongs to a gentle river controlled sedimentary system of delta front which formed at the basin-shrink stage and the basin was dominated by sources of the northern Songliao Basin; （2） the main microfacies of the Heidimiao Reservoir are distributary channels,mouth bars. Using the 9 sets of dark shales formed during regional lake overflow,we divided the Heidimiao Reservoir into 9 reservoir-seal assemblages. A comprehensive analysis of the source-reservoir-seal assemblage features and product data indicates that shallow gas is in the reservoir sandbodies of late regression or early transgression intermediate hemicycles in the early fall long-term hemicycles. The reasonable match of distribution patterns of individual sandbodies, and source gas faults and structure is the dominating factor for shallow gas accumulation. The main types of gas reservoirs here are structure-litho and fault-litho traps. Based on this study and using gas-water interpretation models, we depicted gas traps, and estimated a geologic reserve. The study has great theoretical and practical value in guiding the exploration and development of shallow gas in the north Songliao Basin.