地热储层损害修复与增产技术研究

Research on restoration and stimulation technology for damaged geothermal formations

随着深部地热资源勘查开发规模化的实施,深部钻井工艺和热储层保护与修复面临着新的挑战和问题。目前的深部地热钻井工程,几乎都是采用正循环水基钻井液钻进工艺。由此带来不可避免的主要问题就是热储层损害。在热储层损害修复方面,国内还没有形成强制性的标准和规范。从而出现了许多地热完井后,未进行合理规范的修复改造就进入降压或抽水试验,造成地热资源评价失真和合同纠纷等问题。本文在大量地热钻井工程实例基础上,并结合油气储层改造文献资料,从地热储层损害形式、热储层岩性和堵塞充填物主要矿物组分、修复与增产机理等方面进行了分析研究。试验和工程实践证明:盐酸(HCl)、土酸(HCl+HF)和超临界CO_(2)对热储层中的堵塞物或裂隙,具有溶解、溶蚀、驱逐、置换和扩充作用,是热储层损害修复和储层渗透率提高的基本方法。在实际工程中,单一修复方法效果甚微,应结合热储层损害机理和程度,采用“二合一”或“三合一”方法最佳。针对目前普遍问题,提出了不同类型热储层修复增产的基本方法和热储层修复改造应作为地热钻井工程重要组成部分(工序)。

With the large-scale implementation of deep geothermal resources exploration and development,deep drilling technology and geothermal reservoir protection and restoration are facing new challenges and problems.At present,almost all deep geothermal drilling projects are using circulation boring method of water-based drilling fluid,which caused the damage of geothermal reservoir.In terms of geothermal reservoir restoration there are no compulsory standard in China.As a result,after the completion of geothermal Wells,many of them enter into the depressurization or pumping test without standardized geothermal reservoir restoration,resulting in the wrong evaluation of geothermal resources and contract disputes.This paper is based on a large number of geothermal drilling engineering examples,combined with oil and gas reservoir reconstruction literature.The damage type,lithology,mineral composition of plugging and filling,restoration and stimulation mechanism of geothermal formation are studied.The test and engineering practice show that hydrochloric acid(HCl),mud acid(HCl+HF)and supercritical carbon dioxide can dissolve,expel,displace and expand the blockage or fracture in geothermal reservoir,which is the basic method to restore geothermal reservoir and improve the reservoir ermeability.The single restoration method is not effective in practical application,and the“two-in-one”or“three-in-one”method should be adopted in combination with the mechanism and degree of formation damage.In view of the common problems at present,the basic methods of restoration and stimulation technology for different types of geothermal reservoirs are put forward,in addition,the restoration and reconstruction of geothermal reservoirs should be an important part(working procedure)for geothermal drilling engineering.