西湖凹陷深层低渗-致密气藏“甜点”类型划分及成因探讨

doi:10.11743/ogg20180415

摘要/Abstract

摘要： 低渗-致密气藏开发的关键是“甜点”的识别和预测，为探索海上少井、深层低渗-致密气藏“甜点”类型及成因，指导油气田勘探开发，利用岩心观察，铸体、阴极发光、扫描电镜等薄片鉴定，粒度分析，核磁共振，高压压汞，恒速压汞，孔渗测试和元素分析等多种手段对东海陆架盆地西湖凹陷X气田“甜点”进行研究。首先对研究区“甜点”定义进行探讨，并根据理论产能、物性、孔隙结构和束缚水含量将“甜点”分为3类：Ⅰ类“甜点”为高产气藏，以Ⅰ类孔隙结构为主，束缚水饱和度大多处于22%~57%；Ⅱ类“甜点”为中产气藏，储层中主要发育Ⅱ类孔隙结构，其次为Ⅰ类孔隙结构，少见Ⅲ类孔隙结构，束缚水饱和度大多处于45%~55%；Ⅲ类“甜点”为低产气藏，主要以Ⅲ类孔隙结构为主，发育少量Ⅳ类孔隙结构，束缚水饱和度大多处于45%~55%。认为Ⅰ类和Ⅱ类“甜点”能够实现现阶段经济有效开发，Ⅲ类“甜点”为后期开发的“潜力层”。研究认为，埋深是控制“甜点”发育的决定性因素，研究区4 000 m以深基本不发育Ⅰ类和Ⅱ类“甜点”；沉积环境是控制“甜点”发育的内因；事件性沉积作用及成岩作用是Ⅰ类和Ⅱ类“甜点”的重要影响因素；溶蚀作用是Ⅲ类“甜点”的主控因素；构造运动是研究区气藏“甜点”形成和保存的必要条件。

关键词: “甜点”分类, “甜点”成因, 深层, 低渗-致密气藏, 西湖凹陷, 东海陆架盆地

Abstract: "Sweet spot" identification and prediction is the key to develop tight gas reservoirs with low permeability.In order to explore the types and genesis of "sweet spots" in deep low permeability tight gas reservoirs with fewer wells in the sea,and to guide the exploration and development of oil and gas fields,the study investigated the "sweet spots" in X gas field in the Xihu Sag,East China Sea Shelf Basin,through multiple methods,such as core observation,cast thin section,cathodoluminescence and scanning electron microscopy thin section identification,grain size analysis,nuclear magnetic resonance,high pressure and constant pressure mercury intrusion porosimetry(MIP),porosity and permeability test and elemental analysis.First of all,the definition of "sweet spot" was explored,and three classes of "sweet spots" were identified based on the theoretical production capacity,physical property,pore structure and bound water content:"Sweet spot" Class Ⅰ is high yield gas reservoirs with Type Ⅰ pore structure being dominant and the irreducible water saturation mostly in the range of 22% to 57%; "Sweet spot" Class Ⅱ is moderate yield gas reservoirs with Type Ⅱ pore structure being dominant,followed by Type Ⅰ pore structure and Type Ⅲ pore structure being rare,and irreducible water saturation varies mostly between 45% and 55%; "Sweet spot" Class Ⅲ is low-yield gas reservoirs,with Type Ⅲ pore structure being dominant and a small number of IV pore structures developed,and irreducible water saturation mostly between 45% and 55%.It is believed that Class Ⅰ and Ⅱ "sweet spots" can be efficiently and economically developed at present,but Class Ⅲ "sweet spot" has "potentials" for future development.According to the research,we propose that (1) burial depth is the decisive factor in controlling the development of "sweet spot",thus no Class Ⅰ and Ⅱ "sweet spots" occur in areas with burial depth larger than 4 000 m in general; (2) sedimentary environment is the root cause controlling the development of "sweet spot"; (3) event sedimentation and diagenesis greatly impact the formation of Class Ⅰ and Ⅱ "sweet spot"; (4) dissolution is the main controlling factor for the development of Class Ⅲ "sweet spot"; (5) tectonic movement is a necessary condition for the formation and preservation of "sweet spots" in the study area.

Key words: “sweet spot” classification, origin of “sweet spot”, deep stratum, low permeability tight gas reservoir, Xihu Sag, East China Sea Shelf Basin

中图分类号:

TE122.3

赵仲祥,董春梅,林承焰,等. 西湖凹陷深层低渗-致密气藏“甜点”类型划分及成因探讨[J]. 石油与天然气地质, 2018, 39(4): 778-790. doi: 10.11743/ogg20180415 Zhao Zhongxiang,Dong Chunmei,Lin Chengyan,et al. Classification and origin of “sweet spots” in deep low permeability tight gas reservoirs,Xihu Sag,East China Sea Shelf Basin[J]. Oil & Gas Geology, 2018, 39(4): 778-790. doi: 10.11743/ogg20180415

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