共和盆地当家寺岩体节理裂隙特征及对干热岩储层裂缝指示意义

    Characteristics of joints and fissures of Dangjiasi pluton in Gonghe Basin and the indicative significance for the fractures of hot dry rock reservoirs

    • 摘要: 干热岩储层天然裂缝特征研究对于开展人工储层建造进而实现干热岩开发具有重要意义。通过区域构造、岩性、年龄等分析论证共和盆地当家寺岩体与干热岩开发场地已探获高温干热岩为同一地质体,基于152个节理裂隙调查点共5 289条节理裂隙,详细分析当家寺岩体节理裂隙发育情况、产状特征及切割关系,并与开发场地干热岩钻孔显示的储层裂缝特征进行对比。结果表明: 当家寺岩体节理裂隙发育,以剪节理为主,走向主要发育NE向、NW向两组优势方向,倾角以高角度为主,60°以上占比64.2%; 发育最多裂隙倾向为南东、走向为NE向、倾角大于60°; 裂隙形成具有多期性,主要表现为NE向节理裂隙切割了NW向节理裂隙。与深部干热岩裂缝特征对比显示,当家寺岩体由区域构造作用形成的节理裂隙产状特征与干热岩储层裂缝基本吻合,总体优势走向、优势倾角及发育最多裂缝产状基本一致。研究结果显示, 相同地质体的浅表构造节理裂隙产状可为研究深部干热岩储层裂缝产状提供地表依据。

       

      Abstract: Natural fractures in hot dry rock reservoir are of great significance for artificial reservoir construction and dry hot rock exploitation. Dangjiasi pluton in Gonghe Basin is demonstrated to be the same geological body as the explored high-temperature hot dry rock in this paper, after the analysis of regional structure, lithology and age. Besides, the development, occurrence characteristics and cutting relationship of the joints and fractures in Dangjiasi pluton were analyzed in detail based on 5 289 joints and fractures accumulated from 152 investigation points. And the fracture characteristics were compared with those of the hot dry rock borehole reservoir in the exploitation site. The results show that the joints and fractures of Dangjiasi pluton were well-developed and mainly shear joints, and the dominant strike was NW and NE. The dip angles were mainly high, and those above 60° accounted for 64.2%. The most developed fractures were SE in dip and NE in strike, with dip angle greater than 60°. The fracture formation had multiple stages, which was mainly manifested as the NE strike joints and fractures cutting in the NE strike. The occurrence characteristics of joints and fissures formed by regional tectonic activities in Dangjiasi pluton were basically coupled with the fractures in hot dry rock reservoir, compared with fractures characteristics of hot dry rock. The overall dominant strike, dominant dip angle, and the occurrence of the most developed fractures were basically consistent. The results show that the occurrence of shallow structural joints and fractures of the same geologic body could provide surface basis for studying the occurrence of deep hot dry rock reservoir fractures.

       

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