东辛北带沙四段砂砾岩成因及其成藏模式研究

Origin of Es4 Member Sandy Conglomerate and Its Hydrocarbon Accumulation Pattern in North Belt of Dongxin

东辛北带古地貌形态具有"三扇两沟"特征,沙四段发育大套近岸水下扇和滑塌浊积扇砂砾岩体。沉积相带对砂砾岩体储集物性具有重要的控制作用:扇中亚相物性最好,发育中孔中低渗储层;扇缘亚相、滑塌浊积砂砾岩次之,为中孔低渗储层;扇根亚相物性最差,属于低孔低-特低渗储层。近岸水下扇砂砾岩体成藏条件较好,油气藏产量较高;滑塌浊积砂砾岩体由于物性较差,故油气藏含油气充满度较低,含水较高。

The palaeogeomorphology is characterized by＂three fans and two troughs＂in north belt of Dongxin, where a thick set of sandy conglomerate deposited from nearshore submarine fans and slumping turbidite fans in Es4 Member.The petrophysical properties of Es4 Member sandy conglomerate are significantly controlled by sedimentary facies,with the good,moderate and poor ptrophtsical properties in mid-fan,peripheral-fan and root-fan subfacies respectively,equivalent to a middle porosity and permeability reservoir,a middle porosity and low permeability reservoir and a low porosity and very low permeability reservoir.The sandy conglomerate bodies of nearshore submarine fans are better in hydrocarbon accumulation conditions,and their oil and gas reservoirs are higher in production.The sandy conglomerate bodies of lumping turbidite fans are lower in hydrocarbon saturation and higher in water cut, due to their poor petrophiseal properties.