西湖凹陷渐新统花港组浅水三角洲河道砂岩精细储层预测方法

doi:10.3969/j.issn.1672-7703.2025.02.008

摘要/Abstract

摘要： 东海陆架盆地西湖凹陷中南部花港组整体为浅水三角洲沉积体系，勘探主要目的层埋深大、砂泥岩阻抗相近、河道期次及叠置关系复杂，致使储层预测难度大。针对此问题，通过对Zoeppritz 方程Shuey 近似式梯度项详细解剖，并结合地震正演等分析，明确了AVO 梯度与泊松比相关，对储层响应最为敏感和稳定。采用AVO 梯度进行河道精细刻画，在花港组H5 层识别出4 条分流河道，河道1 和河道4 呈NW—SE 走向，平均宽度、宽厚比、弯曲度分别为0.7km 和0.8km、29 和28、1.04 和1.06；河道2 和河道3 为NE—SW 走向，平均宽度、宽厚比、弯曲度分别为0.85km 和3.1km、26 和70、1.40 和1.09。应用层序地层学认识和相对等时面层拉平等方法进行河道期次识别，从早到晚依次为河道1、河道2、河道3、河道4。通过不同河道地震响应特征和可能的含气平点等多信息交叉验证分析，认为H5 层4 条河道互不连通，均具备独立成藏的条件。建立背斜翼部岩性圈闭“断—砂耦合”的成藏模式，认为构造翼部相对核部具有更好的成藏条件。基于以上认识推动在A 构造河道4 和B 构造河道3 各钻1 口探井，首次获得研究区岩性勘探成功，证实了相关技术方法的实用性与可靠性，并指出了下一步有利勘探区。

关键词: 西湖凹陷, 花港组, 浅水三角洲, 河道砂体, 储层预测, 岩性圈闭, 成藏模式

Abstract: The Oligocene Huagang Formation is mainly composed of a shallow-water delta sedimentary system in the central–southern Xihu
Sag, East China Sea shelf basin. It is difficult to predict the reservoir due to the large burial depth of the main target layer, similar impedance of sandstone and mudstone, complex channel stages and superposition relationship. In response to this problem, the Shuey approximate gradient term of Zoeppritz equation has been studied in detail, and seismic forward analysis has been conducted, which clarify that AVO gradient is related to Poisson’s ratio, and it is the most sensitive and consistent to reservoir response. Using AVO gradient to finely delineate the channel boundary, a total of four distributary channels have been identified in H5 layer. Channels No.1 and No.4 are characterized by NW–SE trending, with the average width, width-to-thickness ratio and curvature of 0.7 km and 0.8 km, 29 and 28, 1.04 and 1.06, respectively. Channels No.2 and No.3 are characterized by NE–SW trending, with average width, width-to-thickness ratio and curvature of 0.85 km and 3.1 km, 26 and 70, 1.40 and 1.09, respectively. Based on sequence stratigraphy and relative isochronous surface flattening method, the stages of channels have been identified, including channels No.1, No.2, No.3 and No.4 from early to late stages. After multi-information cross-validation analysis such as seismic response characteristics of various channels and possible gas bearing flat points, it is regarded that the four channels in H5 layer are disconnected and have the conditions for independent hydrocarbon accumulation. In addition, a “fault-sand coupling” hydrocarbon accumulation mode for lithologic traps in anticlinal wings has been established, which indicates that the anticlinal wings have better hydrocarbon accumulation conditions than the core. Based on the above understanding, one exploration well has been drilled each for channel No.4 in structure A and channel No.3 in structure B, and good exploration results have been obtained in lithologic oil and gas reservoirs for the first time in the study area, confirming the applicability and reliability of the technique and method, and putting forward the favorable exploration zone in the near future.

Key words: Xihu Sag, Huagang Formation, shallow-water delta, channel sand body, reservoir prediction, lithologic trap, hydrocarbon accumulation mode

中图分类号:

P631.4

焦社宝, 许怀智, 蔡坤, 常吟善, 张岩. 西湖凹陷渐新统花港组浅水三角洲河道砂岩精细储层预测方法[J]. 中国石油勘探, 2025, 30(2): 98-114.

Jiao Shebao, Xu Huaizhi, Cai kun, Chang Yinshan, Zhang Yan. Fine reservoir prediction methods for shallow-water delta channel sand body in the Oligocene Huagang Formation in Xihu Sag[J]. China Petroleum Exploration, 2025, 30(2): 98-114.

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