地热储层类型与损害机理研究

Research on geothermal reservoir types and formation damage mechanism

摘要:

常规油气储层损害机理研究比较成熟,而地热储层类型划分与损害机理研究至今尚未引起人们的关注和重视。目前,在地热资源勘查开发中仅出现砂岩热储和岩溶热储2种类型的概念。由于储层概念和类型的含糊不清,从而造成了钻井方法、钻井液选择不当和资源评价失真现象。在热储层损害机理和损害程度评估方面,更是没有规范要求,使地热完井工序缺失,最终导致水量小、温度低,甚至报废等问题。本文在大量地热资源勘查工程基础上,针对目前存在的突出问题,借鉴常规油气储层研究成果,着重从地热储层类型划分和热储层损害机理2方面进行了分析研究。研究表明：①地热储层按照孔隙型、裂隙型、溶洞型和复合型4种模式划分,可以使钻井方法、钻井液选择和资源评价更加合理和精准。②热储层损害表现方式主要是空隙堵塞或储层结构破坏。其中,钻井液侵入和井内压力液柱静、动压力是热储层损害的主要因素,也是不可避免普遍存在的问题。

关键词:地热储层;热储层类型;钻井液侵入;井内压力;损害机理

Abstract:

The research on the formation damage mechanism of conventional petroleum reservoirs is relatively well-established, but there has been a lack of attention towards the type classification and formation damage mechanism of geothermal reservoirs. Currently, only two types of geothermal reservoirs - sandstone and karst - are recognized in the exploration and development of geothermal resources. Because of the unclear concept and type of reservoir, the incorrect drilling method, drilling fluid selection and wrong resource assessment are caused. Furthermore,there is no formation damage mechanism and damage assessment criteria, so that the geothermal well completion process is missing, and leads to small water volume, low temperature, and even abandonment.On the basis of a large number of geothermal engineering, this paper focuses on the research of geothermal reservoir types and formation damage mechanism, aiming at the outstanding problems and referring to the conventional petroleum reservoirs research results. Researches show that: (1) Geothermal reservoirs can be categorized into four types: porous, fissure, karst, and compound type; this categorization allows for more accurate drilling methods, selection of drilling fluids,and resource assessment.(2) The main modes of thermal reservoir damage are porosity blockage or failure in the structure; among these factors,damage caused by intrusion from drilling fluid as well as staticand dynamic pressure from liquid column within wells are inevitable common problems.

Key words:geothermal reservoir; thermal reservoir type; drilling fluid invasion; drilling pressure; mechanism of formation damage.