砂砾岩储层非均质性及其对剩余油分布的影响——以克拉玛依油田二中西区八道湾组为例

Heterogeneity of sandy conglomerate reservoir and its influence on remaining oil distribution: A case study from Badaowan Formation in the mid-west of block Ⅱ in Karamay Oilfield

冲积扇扇中砂砾岩油藏开发后期储层强非均质性引起的注采不平衡、层间干扰矛盾及层内差异等问题极为凸显。以克拉玛依油田二中西区八道湾组冲积扇扇中砂砾岩油藏为例,开展了储层非均质性精细表征研究。运用野外露头观察、岩心描述、测井相分析等,以单砂体刻画及其内部构型技术为支撑,细化了砂砾岩油藏不同类型沉积微相-岩相。结合不同类型单砂体宏观与微观非均质特征,总结出扇中砂砾岩油藏剩余油富集的3种类型:Ⅰ型辫状水道粗砂岩相储层,微观孔隙结构属中孔-中细喉型;Ⅱ型辫状水道细砂岩相储层,微观孔隙结构为细孔-细喉型;Ⅲ型辫状水道砂砾岩相储层,微观孔隙结构为中细孔-中喉型。其中Ⅰ型与Ⅱ型储层剩余油基本分布在储层中上部物性较差、非均质性相对较强的部位,而Ⅲ型砂砾岩相储层由于受岩性与物性差异影响,局部易形成高渗部位,剩余油多呈条带状分布在层内非均质变强、物性变差的部位。针对该类型油藏,以"认识储层非均质性,并解决储层非均质性"为切入点来分析剩余油分布,为砂砾岩油藏高含水期剩余油预测提供了较好的借鉴作用。

At present,the voidage-injection imbalance,interlayer interference and in-layer interference leaded by the reservoir heterogeneity are extremely highlighted during the production tail of sandy conglomerate reservoir in the mid-fan of alluvial fan.Taking the Jurassic Badaowan Formation in mid-west of the block II in Karamay Oilfield as an example,this paper studied the reservoir heterogeneity of alluvial fan sandy conglomerate reservoir.Based on outcrop observation,core description,electrofacies analysis,the single sand body description technique was used to divide the reservoir into 4 types of microfacies-lithofacies single sand body.Combining with the macroscopic and microscopic heterogeneity in different single sand body,the remaining oil were divided into 3 enriched types： Ⅰ-type braided channel gritstone facies,which has mesopore and small throat texture;Ⅱ-type braided channel fine sandstone facies,which has small pore and small throat texture;Ⅲ-type braided channel sandy conglomerate facies,which has small pore and fine throat texture.It is concluded that the type Ⅲ has the best water flooding effect and should be the main object of stabilizing oil production and controlling water cut,and the type I and Ⅱ,where the properties are relatively worse and the heterogeneity is stronger,should be the next potential target.Using this method of＂recognizing the reservoir hetero-geneity and resolving it＂ as the breakthrough point to analyze the single sand body and the heterogeneity,which can provide better reference for forecasting the distribution of remaining oil in the sandy conglomerate reservoir.