河流沉积相类型及相模式

对河流类型进行沉积学分析，将河道体系分为单河道和多河道（或复合河道）体系，顺直河、曲流河和辫状河为单河道体系，而网状河和其他分支河归于多河道体系，单河道一般由细粒漫岸沉积所限定。在曲流河沉积相中，河道内除了河道深泓充填沉积和厚的点坝外，还可能出现反向点坝。在一个向上变细的曲流河层序中，主要由河槽充填沉积、沙坝沉积复合体和上部的漫岸细粒沉积组成。辫状河砂体结构非常复杂，各种大型底形纵横分布，河道内的砂体至少可以划分为河心坝和河心滩2个砂体微相和多个非骨架相。网状河可以由辫状河、曲流河和顺直河等交织在一起组成，或者说组成网状河的单河道可以是底负载河道、混合负载河道和悬移负载河道。末端扇、曲流河扇、辫状河扇乃至某些陆上三角洲体系等都可以纳入分支河体系，实际上在这种分支河体系中，河道性质也发生了变化，河道类型已经由限定性河道转化为非限定性河道。可见分支河这个概念太笼统太宽泛，跨越了不同的体系界限。由于不同河道砂体差别较大，河流沉积微相的精确表征还有较大的局限性。

A New Breakthrough in Exploration of Large Conglomerate Oil Province in Mahu Sag and Its Implications

There had been no significant breakthrough in petroleum exploration in Mahu sag of Junggar basin for about 20 years after the discoveries of Mabei oilfield in 1993 and Ma-6 area in 1994. An overall evaluation was conducted regarding the resources, reservoirs and stimulation potential in Mahu sag in the year of 2010. The results showed that the slope area in Mahu sag was the key strategic area for petroleum exploration. Then the exploration idea was changed from the exploration for structures in the fault zones around source to the exploration for lithological reservoirs in the major area within source. Since 2012 more and more discoveries have been achieved successively. Up to now, 6 large reservoir groups have been discovered and 2 large oil provinces have been proved in the south and north, respectively. The incremental OOIP is 12.4×108 t, among which the proved reserves is 5.2×108 t. The discovery of the large conglomerate oil province proves that hydrocarbon could accumulate in the above-source conglomerate reservoirs under the conditions of fracture connecting, and efficient development could be realized in low-permeability conglomerate reservoirs by using fine volume fracturing technology