扇三角洲砂砾岩储层沉积特征及与储层物性的关系——以罗家油田沙四段砂砾岩体为例

Depositional Characteristics of Sandstone and Conglomerate Reservoirs of Fan Delta and Relationship to Reservoirs' Physical Properties ——Taking the Fourth Member of Shahejie Formation, Luojia Oilfield, Zhanhua Depression for An Example

从岩心和各类薄片资料入手 ,以沉积学和储层地质学为基础 ,结合各类分析资料 ,对山东沾化凹陷罗家油田沙四段砂砾岩体储层的沉积特征进行了研究。前人所提出的水下冲积扇和近岸水下扇沉积的认识 ,忽视了扇形沉积体的水上部分 ,因而改为扇三角洲沉积更为合适。扇三角洲沉积可进一步细分为扇三角洲平原、扇三角洲前缘和前扇三角洲三个沉积亚相及五个微相 ,其中水下分流河道沉积微相的储层最为发育。详细阐述了砂砾岩体的岩性、沉积微相等沉积因素对储层物性的影响 ,其中粒度对砂砾岩储层物性与对砂岩储层物性的影响明显不同。

Based on the sedimentology and reservoir geology, combined with drilling, logging and analytical data, depositional characteristics of sandstone and conglomerate bodies' reservoirs for the fourth member of the Shahejie Formation in the Luojia oilfield are studied in detail. The rusults show unacceptability of some previous cognition. As to depositional environment of fan deposits, the conception of fan delta is better than the nearshore subaqueous fan and the subaqueous alluvial fan. According to the characteristics of sandstone and conglomerate bodies, the fan-deltas can be subdivided into three subfacies and five microfacies. It is elaborated that physical properties of reservoirs are effected by lithological properties, sedimentary microfacies and other factors. The porosity and permeability of reservoirs of sandstone and conglomerate bodies is improved by dissolution of feldspar and carbonate rock-fragments. However, it would be decreased awfully with increase of fine matrix and carbonate contents. A style of parabola is shown in the relationship of the mean grain size with the porosity and permeability of the reservoirs which is greatly different from sandstone reservoirs. The oil-bearing properties of the packsand and the pebbled gritstone with parallel bedding and homogeneous bedding is better than glutinite with wavy bedding and graded bedding. Among all microfacies classified, the best reservoir is developed in subaqueous distributary channels.