饶阳凹陷西6区块沙一上段沉积微相及其含油气性

Sedimentary microfacies and oil/gas-bearing ability of the upper member of Es1 in the Xi-6 area,Raoyang sag

饶阳凹陷作为一个勘探老区,油气年产量日益下降,亟需发现新的油气储量以满足国家战略发展需求。受限于早期的生产技术及理论模式,地层格架划分粗略,评价目标主要集中以段或亚段,精度较高者以油组为主,以单砂体尺度的储层受非均质性的影响导致沉积微相划分不准,为油田增储上产带来挑战,严重制约了油气勘探开发的发展。基于此,利用岩心、录井及测井等资料,本文以饶阳凹陷南马庄地区西6区块为例,对沙一段各小层(单砂体)沉积微相进行刻画,并对各类微相中砂体含油气性进行分析。结果表明:西6区块沙一上段共分为3个油组9个小层;岩性以偏氧化环境的泥岩与偏还原环境的砂岩混合为主,表现为沉积过程中水体震荡摆动的特点;沉积亚相类型为三角洲平原,发育分流河道、天然堤和河漫沼泽3种微相;沉积微相分布范围控制着砂体展布特征,具体表现为分流河道控制小层的砂地比及渗砂厚度分布,其中以Ⅱ_(1)、Ⅱ_(2)小层砂地比值最大,可达至0.75、0.85,Ⅰ、Ⅱ_(1)小层渗砂厚度值最大,可达至30 m、25 m;Ⅱ、Ⅲ油组中各小层分流河道(微)相控制下的储层砂体整体含油气性较高,Ⅱ_(4)、Ⅲ_(2)小层含油层比例最大为69.6%、65.5%。基于各小层沉积微相与含油层的结合,剖析了沙一上段沉积微相与油气分布关系,指出分流河道、天然堤等微相叠合区内渗砂厚度大于5 m为有利的油气聚集区。

The Raoyang sag is an old exploration area and the annual oil and gas production is decreasing each year.It is urgent to find new oil and gas reserves to meet the needs of national strategic development.Limited by the early production technology and the theoretical model,the stratigraphic framework is roughly divided,and the evaluation target is mainly concentrated on the member or sub-member level,and the oil group is the main one with higher accuracy.Single sand body scale reservoirs are affected by heterogeneity,which leads to the inaccurate division of sedimentary microfacies,which brings challenges to the increase of reserves and production,and seriously restricts the development of oil and gas exploration and development.Based on this,using the core,logging,and logging data,this paper takes the Xi-6 block in the Nanmazhuang area of the Raoyang sag as an example to characterize the sedimentary microfacies of each small layer(single sand body)in the upper member of Es1,and analyzes the oil and gas bearing properties of sand bodies in various microfacies.The results show that the upper SHA-1 member of block Xi-6 is divided into 3 oil formations and 9 sub-layers;the lithology is mainly composed of mudstone from a partially oxidizing environment and sandstone from a partially reducing environment,which is characterized by water oscillation during deposition;the type of sedimentary subfacies is delta plain with three microfacies:distributary channel,natural dike,and river swamp;the distribution range of sedimentary microfacies controls the distribution characteristics of sand bodies,specifically,the distributary channel controls the ratio of sand and sand infiltration thickness distribution of the sublayer,among which the ratio of sand of sublayer Ⅱ_(1) and Ⅱ_(2) is the largest,up to 0.75 and 0.85,and the sand infiltration thickness of sublayer Ⅰ and Ⅱ_(1) is the largest,up to 30 m and 25 m.Under the control of distributary channel microfacies of each small layer in oil group Ⅲ,the overall oil-bearing property of reservoir sand bodies is relatively high,and the largest proportion of oil-bearing layers in Ⅱ_(4) and Ⅲ_(2) is 69.6%and 65.5%.Based on the combination of sedimentary microfacies and oil-bearing layers,the relationship between sedimentary microfacies and oil-gas distribution in the upper Es1 member is analyzed,and it is pointed out that the favorable oil-gas accumulation area is where the thickness of permeable sand in the superimposed area of microfacies such as distributary channels and natural dikes is more than 5 m.