鄂尔多斯盆地陇东地区延长组长4+5油层组储层特征及主控因素分析

Characteristics and main controlling factors of Chang 4+5 oil reservoir set in Longdong area, Ordos Basin

鄂尔多斯盆地陇东地区延长组长4+5油层组储层由三角洲—湖泊沉积形成,其岩性主要为岩屑质长石砂岩、长石质岩屑砂岩和岩屑砂岩,岩屑含量整体较高。储层平均孔隙度为11.02%,平均渗透率为0.37 mD,属典型的低孔、低渗—特低渗储层,主要孔隙类型为粒间孔及粒内溶孔,孔隙结构以细—小孔微细喉型为主,分选与连通性较差。纵向上,长4+51小层储层物性好于长4+52小层;平面上,西南部储层物性整体优于东北部。陇东地区延长组长4+5油层组致密储层经历了压实、胶结和溶蚀等成岩作用。致密储层的形成主要受沉积和成岩作用的影响,沉积作用是形成致密储层的基础,成岩作用则是形成致密储层的关键因素,强烈的压实和胶结作用是影响储层物性的主要成岩作用。陇东地区延长组长4+5油层组有利储层多发育在三角洲前缘水下分流河道和河口坝砂体中,特别是主砂体中心部位储层物性最好。

The Chang 4＋5 oil reservoir set of Triassic Yanchang Formation in I^ngdong area developed delta and lacustrine facies. The reservoir rock types are mainly lithic arkose, feldspathic litharenite and litharenite. The reservoir is typical low porosity and low permeability reservoir with the average porosity of 11.02% and average permeability of 0.37 mD. The main pore types are intergranular pores and intragranular dissolved pores. The pore structure is tiny pore and micro throat with poor sorting and connectivity. In profile, the reservoir properties of Chang 4＋51 sublayer is better than that of Chang 4＋52 sublayer, and the reservoir properties in the southwest are better than that in the northeast. The clastic rocks experienced compaction, cementation and dissolution. Diagenesis is the basis for the reservoir tightening, while diagenesis is the key factor for forming thigh reservoir. The strong compaction and cementation are the main diagenesis for influencing reservoir properties. The underwater distributary channel and the mouth bar sand body in delta front are favorable reservoirs, and the reservoir properties in the central part of the sand body are the best.