The tight sandstones of the fourth (E3h4) and fifth (E3h5) members of the Oligocene Huagang (E₃h) Formation in the Xihu Sag of the East China Sea Basin are feldspar lithic quartzose, which are ideal for the investigation of compaction. Based on routine core analysis, petrology, fluid inclusions, and compaction numerical simulation, this study investigated the compaction characteristics, porosity evolution, and high-value porosity area of tight sandstone on a structural anticline two-dimensional (2D) profile. The textural characteristics of the sandstones are moderately well sorted and are generally subangular-subrounded. The E3h4 and E3h5 sandstones on the crest of the anticline develop primary intergranular pores, whereas these sandstones on the flank develop a small amount of primary intergranular pores. The contact types between quartz grains on the anticline crest were mainly tangential, long, and concavo-convex contacts, whereas the contact types between quartz grains on the flank were primarily long, concavo-convex, and sutured contacts. The duration age of the mechanical compaction (MEC) porosity loss of sandy conglomerate (SC), fine-grained sandstone (FS), and medium-grained sandstone (MS) in the E3h4 and E3h5 members ranged from 27 Ma to 7 Ma. The onset of the chemical compaction (CHC) of the E3h4 and E3h5 sandstones were between 10.2 Ma and 10.6 Ma, respectively. Based on similar grain size, mineral composition, and sorting, the degree of the MEC of the E3h4 and E3h5 sandstones on the crest of the anticline is less than that of the flank due to burial depth. The distribution ranges of the MEC porosity loss were 21.92%–26.02% and 22.31%–26.43% for the E3h4 on the anticline crest and flank and 26.74%–27.26% for the E3h5 on the flank, respectively. By integrating similar burial time and clay minerals, the degree of the CHC of the E3h4 and E3h5 sandstones on the crest of the anticline is less than that of the flank due to reservoir temperature. The distribution ranges of the CHC porosity loss were 0.41%–1.05% and 0.44%–1.02% for the E3h4 on the anticline crest and flank and 0.48%–0.91% for the E3h5 on the flank, respectively. During the Late Miocene Longjing movement, the CHC porosity loss ranged from 0.15% to 0.4%. The study results show that the sandstone with porosity between 9% and 11% is distributed sporadically in E3h4 and E3h5, whereas the sandstone with porosity between 6% and 9% is distributed in contiguous pieces. The formation of high-value porosity areas is mainly due to the coarser grain size, shallower burial depth, chlorite coat, underdeveloped illite, lower reservoir temperature, and slight overpressure.

_{渐新统花港（E3）四段（ E3h4}）和五段（E3h5）致密砂岩h) 东海盆地西湖凹陷地层为长石岩屑石英岩，是研究压实作用的理想材料。本研究基于常规岩心分析、岩石学、流体包裹体和压实数值模拟，研究了构造背斜二维（2D）剖面上致密砂岩的压实特征、孔隙度演化和高值孔隙度区域。砂岩的结构特征分选中等，一般呈亚角-亚圆形。背斜顶部的E3h4和E3h5砂岩发育原生粒间孔，而侧面的这些砂岩发育少量原生粒间孔。背斜峰顶石英颗粒间的接触类型主要为切向接触、长接触、凹凸接触，而侧面石英颗粒之间的接触类型主要是长的、凹凸的、缝合的接触。E3h4和E3h5段砂砾岩（SC）、细粒砂岩（FS）和中粒砂岩（MS）机械压实（MEC）孔隙度损失的持续年龄为27~7Ma。E3h4 和 E3h5 砂岩的化学压实 (CHC) 开始时间分别在 10.2 Ma 和 10.6 Ma 之间。基于相似的粒度、矿物组成和分选，背斜顶部E3h4和E3h5砂岩的MEC程度由于埋深而小于侧面。背斜峰顶和侧面E3h4的MEC孔隙度损失分布范围为21.92%～26.02%和22.31%～26.43%，侧面E3h5的MEC孔隙度损失分布范围为26.74%～27.26%。综合相似的埋藏时间和黏土矿物，背斜顶部E3h4和E3h5砂岩的CHC程度低于侧翼，受储层温度影响。背斜峰顶和侧翼E3h4的CHC孔隙度损失分布范围为0.41%~1.05%和0.44%~1.02%,侧面E3h5的分布范围为0.48%~0.91%。晚中新世龙井运动期间，CHC孔隙度损失范围为0.15%～0.4%。研究结果表明，孔隙度在9%~11%的砂岩在E3h4和E3h5呈零星分布，而孔隙度在6%~9%的砂岩呈连片分布。高值孔隙区的形成主要是由于粒度较粗、埋深较浅、绿泥石层、伊利石不发育、