富泥三角洲特征及形成机理研究—以海拉尔盆地大磨拐河组三角洲为例

Gillbert-type deltas commonly consists of topset, bottomset and foreset, which.ususally is coarse-grained sediment, such as gravel, sandstone. And.prograding-seismic reflections can be observed through seismic profiles. Samely.the Damoguaihe formatin of Hailaer basin is charactered by prograding-seismic.reflections through 3D-seismic data analyzing, however, it is usually muddy.sediment by core data or well logs data. It is confirmed that this muddy sediment.which charactered   by prograding-seismic reflections is one type of deltas.deposition. So this unusual muddy delta has Gillber-type deltas architecture and.sepcial sedimentary sequence. The important factor is sandbody for oil exploration.of Damoguaihe formation. Hense, it has theoretical significance that the.sedimentary sequence, architecture, building mechanism of this muddy delta must be.analyzing, and it has practical significanse for oil exploration of muddy deltas.samelly. This study will analyze the sedimentary characters, faces, and forming.mechanism of muddy deltas through core data, logging data, seismic data, and.outcropping, and some recognitions may be found about muddy deltas.

经典的吉尔伯特型三角洲由顶积层、前积层和底积层三部分组成，并且前积层往往为砾、砂等砂质沉积物，地震剖面上可见前积反射结构。海拉尔盆地大磨拐河组地层在地震剖面上显示完美的前积结构，而钻井显示前积层多为泥质沉积，泥地比值可达70%，经证实为三角洲沉积。这种富泥的三角洲既具有吉尔伯特型三角洲的结构，却又有着独特的垂向沉积序列。并且大磨拐河组地层成藏的关键是砂体是否发育。因此，确定这种富泥三角洲的垂向沉积序列展布、地层叠加样式、岩性分布特征、形成机理及石油地质意义既可以在理论上补充、完善沉积学中关于三角洲的特征及分类体系的认识，又可以在实践中指导富泥三角洲的油气勘探及开发工作。本题拟综合测井、录井、岩芯、露头、三维地震资料及水槽实验详细研究富泥三角洲的结构、沉积充填特征、相带划分及主要控制因素，预期获取富泥三角洲相标志、相模式、沉积演化、形成机理等方面的成果认识。

经典的吉尔伯特型三角洲由顶积层、前积层和底积层三部分组成，并且前积层往往为砾岩、砂岩等粗粒沉积物。综合测井、录井、岩芯、露头及三维地震资料对大磨拐河组地层进行了详细的研究，证实大磨拐河组为早白垩时期湖相沉积下的三角洲体系，且沉积物主要以泥质为主，泥岩占比可达70%，该泥质三角洲既具有经典吉尔伯特型三角洲的前积结构，却又有着独特的垂向沉积序列。并且成藏条件分析表明，大磨拐河组地层成藏的关键是砂体是否发育。通过对大磨拐河组地层进行详细的岩性描述，确定大磨拐河组的三角洲沉积主要以泥质为主，不同于以往的粗粒沉积。因此，望对该泥质三角洲的研究可以在实践中指导泥质三角洲的油气勘探及开发工作。