地学前缘 ›› 2021, Vol. 28 ›› Issue (1): 235-248.DOI: 10.13745/j.esf.sf.2020.5.22

• 致密/页岩储层 • 上一篇    下一篇

四川安岳气田龙王庙组颗粒滩岩溶储层发育特征及主控因素

张满郎(), 郭振华, 张林, 付晶, 郑国强, 谢武仁, 马石玉   

  1. 中国石油勘探开发研究院, 北京 100083
  • 收稿日期:2019-12-05 修回日期:2020-05-19 出版日期:2021-01-25 发布日期:2021-01-28
  • 作者简介:张满郎(1963—),男,博士,高级工程师,从事储层评价、油气藏描述及开发地质研究。E-mail: zhangml69@petrochina.com.cn
  • 基金资助:
    国家科技重大专项(2016ZX05007);中国科学院A类战略性先导科技专项(XDA14010403)

Characteristics of and main factors controlling the karst shoal reservoir of the lower Cambrian Longwangmiao Formation in the Anyue gas field, central Sichuan Basin, China

ZHANG Manlang(), GUO Zhenhua, ZHANG Lin, FU Jing, ZHENG Guoqiang, XIE Wuren, Ma Shiyu   

  1. Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China
  • Received:2019-12-05 Revised:2020-05-19 Online:2021-01-25 Published:2021-01-28

摘要:

安岳气田磨溪区块下寒武统龙王庙组气藏是迄今为止我国已发现的最大的整装碳酸盐岩气藏。该气藏发育于川中古隆起东端,已探明含气面积805 km2,提交探明天然气地质储量4 403.8×108 m3,其高效开发对保障川渝地区的天然气供应具有重要战略意义。龙王庙组储层发育表现出较强的非均质性,不同部位气井产能差异较大。深入开展储层宏观、微观特征研究,评价储层空间分布的非均质性,对气藏开发部署具有重要的支撑作用。基于岩心、成像测井、铸体薄片、CT扫描、核磁共振、压汞等分析手段,对安岳气田下寒武统龙王庙组开展了系统的层序地层划分对比、岩溶模式研究、储层特征及其主控因素研究。研究结果表明,龙王庙组可识别出溶蚀孔洞、溶蚀孔隙、基质孔隙3种储集空间类型,主要为砂屑白云岩溶蚀孔洞型储层,中小溶洞发育,具有中低孔、中-高渗特征。龙王庙组全直径样品分析储层孔隙度为2.00%~18.48%,平均4.81%,渗透率为0.01~78.5 mD,平均渗透率3.91 mD。由于缝、洞发育,不同尺度样品测试的储层渗透率差异明显,测井解释渗透率一般为0.1~10 mD,略大于岩心测试渗透率,试井解释渗透率分布于3.24~925 mD,是岩心测试渗透率的1~2个数量级。龙王庙组可划分为4期向上变浅的沉积旋回,纵向上发育4期向上变粗的颗粒滩,平面上呈“两滩一沟”的分布格局,第二、三期颗粒滩分布规模最大。龙王庙组经历了准同生期、表生期、埋藏期岩溶作用,准同生期颗粒滩频繁的短暂暴露并遭受大气淡水的淋漓改造,形成早期的微孔及针状溶孔。加里东期风化壳岩溶是龙王庙组溶蚀孔洞型储层形成的关键,广阔的岩溶斜坡区顺层溶蚀孔洞发育。溶蚀孔洞型储层叠置连片,并与高角度构造裂缝配置良好,形成整体连通的裂缝-孔洞型视均质储层。优质储层主要发育于磨溪11—磨溪8和磨溪10—磨溪12—磨溪9井区,储层厚度为40~50 m。

关键词: 安岳气田, 龙王庙组, 颗粒滩, 储集空间, 岩溶模式, 储层特征, 主控因素

Abstract:

The Lower Cambrian Longwangmiao Formation gas reservoir in the Moxi Block of the Anyue gas field is the largest complete carbonate gas reservoir discovered in China so far. The gas reservoir, developed in the eastern end of the paleo-uplift in the central Sichuan Basin, has a proven gas-bearing area of 805 km2 and proven gas geological reserves of 4403.8×108 m3. Its high efficiency development is of strategic significance for ensuring natural gas supply in the Sichuan-Chongqing area. Reservoir development in the Longwangmiao Formation shows strong heterogeneity, and the gas well productivity varies greatly across the reservoir. For gas reservoir development and deployment, it is very important to study both macroscopic and microscopic characteristics of the reservoir and evaluate the heterogeneity of the reservoir storage space. Based on core, imaging log and cast slice data as well as CT scan, nuclear magnetic resonance, mercury injection, etc., we conducted a systematic study on the stratigraphic sequence division, correlation, karst pattern, reservoir characteristics and main controlling factors of the Lower Cambrian Longwangmiao Formation in the Anyue gas field of the central Sichuan Basin. Results show that there are three types of reservoir storage spaces in the Longwangmiao Formation: millimeter-sized dissolved vugs, solution pores, and intergrain/intercrystal pores. Reservoir of the Longwangmiao Formation is mainly developed in sand-clastic dolomite, featuring small to medium-sized dissolved vugs or solution pores, with medium-low porosity and medium-high permeability. Porosity of the full diameter samples from the Longwangmiao Formation was between 2%-18.48%, averaging at 4.81%, and the full diameter permeability ranged between 0.01-78.5 mD, averaging at 3.91 mD. Due to fracture and cavity, reservoir permeability acquired at different measurement scales varied greatly. The log interpreted permeability ranged between 0.1-10 mD, which was slightly higher than the core tested permeability; whereas well tested permeability ranged between 3.24-925 mD, about 1-2 orders of magnitude higher than the core tested permeability. The Moxi area developed four stages of shaols in the vertical and two main shoals with one trench in the horizontal directions, while the second and third stage shaols distribute most extensively. The Longwangmiao Formation experienced three stages of reservoir dissolution, namely the pene-sedimentary, supergene reformation and burial stages. In the pene-sedimentary stage, frequent short time exposures and leaching and dissolution of meteoric fresh water resulted in the formation of early micropores as well as solution pinholes in shoal carbonate deposits. Caledonian period karstification was the key factor for the formation of the vuggy reservoir of the Longwangmiao Formation. Along the vast karst slope, bed-parallel dissolved vugs and pores were well developed, with the karst vuggy reservoirs superimposing vertically and compacting laterally. The favorable spatial allocation of the bed-parallel dissolved vugs and the high-steep structure fissures resulted in the formation of the apparently homogeneous fractured vuggy reservoir. High-quality reservoir is mainly distributed in the MX11- MX8 and MX10-MX12-MX9 well fields, with a reservoir thickness of 40-50 m.

Key words: Anyue gas field, Longwangmiao Formation, shoal, reservoir space, karst pattern, reservoir characteristics, main controlling factors

中图分类号: