玛湖地区三叠系克拉玛依组浅水辫状河三角洲沉积特征

近年来，玛湖地区三叠系克拉玛依组的多口井获得工业油气流，展现了该地区中浅层较大的勘探潜力。为了查明玛湖地区克拉玛依组沉积体系特征，明确主要砂体的成因和分布，开展了岩心观察、物源分析、沉积相研究、砂体平面展布规律及控制因素研究。结果表明：①克拉玛依组沉积时期，准噶尔盆地处于坳陷湖盆演化阶段，玛湖地区由"多隆多凹"逐渐转化为"大型缓坡"背景，在此基础上发育四大物源体系，主要为浅水辫状河三角洲沉积，三角洲前缘水下分流河道砂体为主要储集体类型；②克拉玛依组下段的砂体主要集中于底部，与泥岩呈互层状，在夏子街、黄羊泉等主物源区较为发育；③克拉玛依组上段的砂体主要发育于顶部，三角洲砂体呈叠瓦状向湖盆中心进积，延伸较远。克拉玛依组下段砂体与上段厚层暗色泥岩形成的储盖组合和克拉玛依组顶部砂岩与白碱滩组巨厚泥岩形成的储盖组合均为有利勘探领域。该研究成果对玛湖地区克拉玛依组的油气勘探具有指导意义。

Sedimentary characteristics of shallow-water braided delta of Karamay Formation in Mahu area

Recently,several wells of Karamay Formation in Mahu area have obtained industrial oil and gas flow,which shows a favorable exploration potential of middle and shallow strata. In order to find out the characteristics of sedimentary system of Karamay Formation in Mahu area and to clarify the origin and distribution of main sand bodies,core observation,provenance analysis,sedimentary facies study,plane distribution rule and controlling factors of sand bodies were carried out. The results show that:(1)During the sedimentary period of Karamay Formation,Junggar Basin was a depression lacustrine basin,and Mahu area was gradually transformed from a "multi-uplift and multi-depression" to a "large gentle slope" background. Based on this structural background,four provenance systems were developed during the Karamay Formation. The sedimentary facies are mainly shallow braided river delta. The main reservoir types are underwater distributary channel sand bodies in the front of shallow braided river delta.(2)The sand bodies in the lower Karamay Formation are mainly concentrated at the bottom,interbedded with mudstone,and relatively developed in Xiazijie,Huangyangquan and other main provenance areas;(3)The sand bodies in the upper Karamay Formation are mainly developed at the top, and the delta sand bodies deposit in the form of imbrication toward the center of the lacustrine and extend far away. Reservoir-seal assemblage formed by sand bodies of lower Karamay Formation and thick dark mudstone of upper Karamay Formation and reservoir-seal assemblage formed by sand bodies at top of Karamay Formation and huge thick mudstone of Baijiantan Formation are favorable exploration zones. The research results have guiding significance for oil and gas exploration of Karamay Formation in Mahu area.