温米退积型与进积型浅水辫状河三角洲沉积模式

Depositional Models of Regressive and Progressive Shoal Braided Deltas in Wenmi Oilfield

不同类型辫状河三角洲的成因分析是预测剩余油分布及制定合理开发政策的基础。岩石地球化学及成因地层分析表明,温米油田三间房组是在气候干燥的淡水湖盆长期基准面旋回内的退积型和进积型浅水辫状河三角洲沉积。应用精细成因地层对比方法建立三间房组单砂层成因地层格架。基于单分流河道识别：退积型辫状河三角洲规模小,分流河道宽深比30~58,平面形态纵向由枝状向指状演化,发育CSm→MSp-l→FSh→FSp-h→FStr→FSp-h→Fr较细岩石相组合;进积型辫状河三角洲规模相对较大,分流河道宽深比53~108,平面形态纵向呈指状-枝状-片状演化,发育SCm→GCSm→CStr→FSp-h→FSp-l较粗岩石相组合,湖底坡折带发育小型河口坝。水气交替注入能较大幅度提高这类油藏的采收率。

Genetic analysis on different braided deltas is the basis of remaining oil prediction and reasonable developing policy making.Lithogeochemical and genetic stratigraphic analysis indicates that Sanjianfang Formation in Wenmi oilfield is deposited by regressive and progressive shoal braided deltas during long term base level cycles under the aridic climate in a fresh lacustrine basin.Genetic stratigraphic frameworks of individual sand units of Sanjianfang Formation are established with the method of detailed genetic stratigraphic correlation.Regressive braided deltas are smaller in scale,within which distributary channels range from 30 to 58 in width to depth ratios,and evolve from branched shape to fingered shape in areal geometry,and consist of finer lithofacies association of CSm→MSp-l→FSh→FSp-h→FStr→FSp-h→Fr.On the contrary,progressive braided deltas are larger in scale,within which distributary channels range from 53 to 108 in width to depth ratios,and evolve from fingered shape to branched and sheeted shapes in areal geometry,and include coarser lithofacies association of SCm→GCSm→CStr→FSp-h→FSp-l.Small scaled mouth bars are formed around the slope break areas of lacustrine bottom.Water alternating gas（WAG） injection can enhance the recovery efficiency further.