石油与天然气地质 ›› 2023, Vol. 44 ›› Issue (4): 923-936.doi: 10.11743/ogg20230410

• 油气地质 • 上一篇    下一篇

北部湾盆地涠西南凹陷流沙港组二段下亚段页岩油储层非均质性特征

邓勇(), 范彩伟, 胡德胜, 何卫军, 张建新   

  1. 中海石油(中国)有限公司 湛江分公司,广东 湛江 524057
  • 收稿日期:2023-02-20 修回日期:2023-05-05 出版日期:2023-08-01 发布日期:2023-08-09
  • 第一作者简介:邓勇(1975—),男,教授级高级工程师,海上石油地质与综合勘探。E-mail: dengy@cnooc.com.cn
  • 基金项目:
    中国海洋石油有限公司科技项目(KJZH-2023-2106);中国海洋石油有限公司“十四五”重大科技项目(KJGG2022-0303)

Heterogeneity of shale oil reservoirs in the E2l2(1) in Weixinan Sag, Beibu Gulf Basin

Yong DENG(), Caiwei FAN, Desheng HU, Weijun HE, Jianxin ZHANG   

  1. Zhanjiang Branch of CNOOC,Zhanjiang,Guangdong 524057,China
  • Received:2023-02-20 Revised:2023-05-05 Online:2023-08-01 Published:2023-08-09

摘要:

北部湾盆地涠西南凹陷是中国南海海域重要的常规和非常规油气勘探开发区域,2022年7月WY-1井页岩油压裂测试成功并获得商业油气流,标志着中国海上页岩油勘探取得重大突破。基于岩心、薄片、矿物组成、有机地化、扫描电镜、基质孔渗和精细测井分析,开展了涠西南凹陷WY-1井的页岩油储层非均质性特征研究。结果表明:WY-1井流沙港组二段下亚段(流二下亚段)可识别出富硅黏土质泥岩相、混合质泥岩相、富黏土硅质粉砂岩相和(混合)硅质砂岩相4类岩相。对该4类岩相的物性、孔喉特征、可动性和脆性进行分析发现,储集空间以粒间孔为主,(混合)硅质砂岩相孔渗值最高、可压性最好、可动性最高,为有利岩相,富黏土硅质粉砂岩相次之,混合质泥岩相与富硅黏土质泥岩相较差,但混合质泥岩相可压性与可动性好于富硅黏土质泥岩相。有利于储层发育的顺序为(混合)硅质砂岩相>富黏土硅质粉砂岩相>混合质泥岩相>富硅黏土质泥岩相。从储集性的纵向展布特征来看,流二下亚段底部储集性、可动性和可压性最好,其岩相主要为(混合)硅质砂岩相和富黏土硅质粉砂岩相互层;流二下亚段中部混合质泥岩相与富硅黏土质泥岩相互层分布,其脆性和可压性较流二下亚段上部好。综合评价认为,WY-1井甜点段主要为(混合)硅质砂岩相和富黏土硅质粉砂岩相以互层形式分布的流二下亚段下部,其次为混合质泥岩相较为发育的流二下亚段中部。

关键词: 岩相, 非均质性, 页岩油储层, 流二下亚段, 涠西南凹陷, 北部湾盆地

Abstract:

Weixinan Sag, an important area for the exploration and development of both conventional and unconventional hydrocarbon in the Beibu Gulf Basin, South China Sea, has witnessed the success of well WY-1 which tested commercial oil and gas flow after fracturing in July, 2022, marking a major breakthrough in offshore shale oil development in China. An integration of the analysis of core, thin section, mineral composition, organic geochemistry, scanning electron microscope (SEM), matrix porosity and permeability and fine logging, is applied to study the heterogeneous signatures of shale oil reservoirs in well WY-1, Weixinan Sag. The results are shown as follows. Four types of lithofacies can be identified in the lower submember of the second member of Liushagang Formation (E2l2(1)) in well WY-1, including highly siliceous clayey mudstone, mixed mudstone, clay-rich siliceous siltstone and (mixed) siliceous sandstone. Lithofacies is key to the reservoir heterogeneity. An analysis of the physical properties, pore throat characteristics, mobility and brittleness of the four types of lithofacies, indicates that the reservoir space is dominated by intergranular pores, and the (mixed) siliceous sandstone facies is of the highest porosity and permeability, the best compressibility and the highest mobility, a favorable lithofacies, followed by clay-rich siliceous siltstone, and the mixed mudstone and highly siliceous clayey mudstone coming at last though the compressibility and mobility of mixed mudstone are relatively better than the highly siliceous clayey mudstone. It is found that the favorable lithofacies for reservoir development can be sorted as (mixed) siliceous sandstone the first, followed by clay-rich siliceous siltstone, mixed mudstone and highly siliceous clayey mudstone in order. In terms of the vertical distribution of reservoir properties, the bottom interval of the E2l2(1) dominated by (mixed) siliceous sandstone interbedded with clay-rich siliceous siltstone, is the best in reservoir property, mobility and compressibility; the brittleness and compressibility of the interbedded mixed mudstone and highly siliceous clayey mudstone in the middle interval of the E2l2(1) are better than the upper interval. In all, it can be concluded that the sweet-spot section in well WY-1 is mainly composed of (mixed) siliceous sandstone interbedded with clay-rich siliceous siltstone in the lower interval of the E2l2(1), followed by the middle interval where mixed mudstone is well developed.

Key words: lithofacies, heterogeneity, shale oil reservoir, E2l2(1), Weixinan Sag, Beibu Gulf Basin

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