三水盆地页岩气成藏条件分析

doi:10.3969/j.issn.1672-7703.2017.02.010

摘要/Abstract

摘要： 三水盆地常规油气研究程度较高，但针对非常规油气，特别是页岩气研究不足。为研究三水盆地古近系（土布）心组页岩的成藏条件，结合构造和区域沉积背景，通过野外露头观察、样品测试、扫描电镜等多种技术手段，对暗色页岩分布情况、有机地球化学特征及页岩储集性能进行研究。研究表明，三水盆地（土布）心组发育时期为湖盆的主要形成时期，湖相沉积环境控制了暗色页岩的发育，盆地沉积中心与沉降中心一致，暗色页岩厚度为50~70m，平均为58m，埋藏深度为500~3000m，有利于有机质保存。（土布）心组页岩干酪根类型为Ⅱ-Ⅲ型，TOC分布在0.56％~3.29%，平均为1.25%， R_o分布在0.71％~1.94%，平均为1.31%，处于成熟阶段，具备页岩气成藏的基本条件。镜下观察显示，孔隙类型以自生黏土矿物中的微孔隙为主，孔喉半径多为1~8μm，总孔隙空间发育，可提供有效的页岩气储集空间。（土布）心组由下到上可划分为一段、二段和三段，其中（土布）心组二段为深湖相沉积，其沉积期是盆地主要暗色页岩形成期，各项有机地球化学参数最为有利，储集性能相对较好，最具有生烃潜力，（土布）心组三段次之，一段最差。

关键词: 三水盆地, 页岩气, (土布)心组, 成藏条件, 发展前景

Abstract: Many studies have been conducted on conventional oil and gas in the Sanshui Basin, but insuffcient efforts have been made on unconventional oil and gas, especially shale gas. In this paper, based on the structural and regional sedimentary settings, and using multiple techniques such as outcrops observation, samples testing, and scanning electron microscope (SEM), the distribution, organic geochemical features and reservoir properties of the Palaeogene Buxin Formation dark shale were investigated to identify the accumulation conditions in this area. It is shown that the Buxin Formation shale was developed under the control of lacustrine sedimentary environment during the formation of the lake basin, with consistent depocenter and subsidence center, shale thickness of about 50-70 m (58 m on average), and burial depth of about 500-3000 m, which are favorable for preservation of organic matters. Dominated by Type Ⅱ-Ⅲ kerogens, the Buxin Formation shale is in the maturity stage, with TOC of 0.56%-3.29% (1.25% on average) and Ro of 0.71%-1.94% (1.31% on average), indicating that it is basically qualifed for gas accumulation. Microscopically, micropores in authigene clay minerals are dominant, with the pore-throat radius of 1-8 μm, and total pore space is developed, providing effective reservoir space for shale gas. The Buxin Formation can be divided into three members from the bottom to the top. The 2^nd Member composed of deep lacustrine sediments was deposited during the period when dark shale in the basin was formed and has the most favorable organic geochemistry parameters, relatively good reservoir properties, and greatest hydrocarbon generation potentials. In contrast, the 3^rd Member and 1^st Member have inferior properties in a descending order.

Key words: Buxin Formation, accumulation conditions, development prospects, Sanshui Basin, shale gas

中图分类号:

TE112

苑坤, 方欣欣, 林拓. 三水盆地页岩气成藏条件分析[J]. 中国石油勘探, 2017, 22(2): 84-89.

Yuan Kun, Fang Xinxin, Lin Tuo. Analysis on accumulation conditions of shale gas in Sanshui Basin[J]. China Petroleum Exploration, 2017, 22(2): 84-89.

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