珠江口盆地惠州凹陷HZ21区岩性地层油气藏分布特征

惠州凹陷经历了近几年对岩性油气藏勘探的实践和探索,认为层序-沉积-构造综合影响了岩性地层圈闭的分布。频繁的海平面变化,三角洲在盆地内的尖灭和相互叠置,砂体展布末端的局部构造抬升都是有利的影响因素。HZ21区位于惠州凹陷的东部,在珠江组沉积时期,珠江三角洲的前缘带向东披覆在东沙隆起的西倾斜坡带,在HZ21区形成三角洲前缘的砂体尖灭,海陆过渡时期的沉积特征和复杂的水动力条件使得前缘砂体受波浪和潮汐作用改造,形成北西—南东向展布的条带砂,快速尖灭的砂体展布形态和良好的物性使其成为该区岩性地层圈闭勘探的重点。结合高精度层序格架和沉积展布特征分析,认为K22low、K22up和K08low均为改造后的条带砂,是HZ21区重点勘探目标,K08up为三角洲前缘尖灭沉积,由于尖灭位置不易确定,该砂体具有一定的勘探风险。

Distribution of stratigraphic and lithologic reservoirs in Block 21 of Huizhou Sag, Pearl River Mouth Basin

By these years research on lithological reservoir exploration in HuiZhou sag, it is widely recognized that lithological reservoir distribution is affected by sequence stratigraphy, deposition, and structure. And several other favorable factors are also important to the distribution, such as frequency see level change, delta sand pinch out and stacked , local structure uplift, and so on. As one of the important area, Block HZ21 is on the east of Huizhou sag, which the east slope of Dongsha Massif is draped by the delta sand from west, and pinched out in most area of HZ21. The northwestward banding sand distribution is reformed by wave and tide in the continental-marine transitional period, which make the pinch out area become the key of lithological reservoir exploration of this area. Combined with high-resolution sequence framework and sedimentary distribution characteristics analysis, we think the banding sand of K22-low, K22-up, K08-low is the main target of the next exploration target, and because of its uncertain pinch out position, sand K08-up (delta front pinched out sand) has a certain risk of exploration.