干热岩压裂开发技术现状及展望

Present Situation and Prospect on Hydraulic Fracturing Development Technique of Hot Dry Rock

干热岩的应用原理是在地层中不渗透的干热岩体内形成热交换系统,取出热水进行发电或取暖等。我国高温岩体干热岩地热资源储量丰富,地壳深层岩体温度高。发达国家在干热岩发电的基本原理和基本技术方面有相当大的进展,而我国在其开发利用方面处于探索阶段。干热岩开发经常采用一注一采系统,也有一注三采、二注一采系统。一注一采系统在执行过程中,大都经过了后期的调整,即重新钻一口新井,钻入老井压裂形成的裂隙系统中。一般而言,地应力状态决定裂缝形态是水平裂缝还是垂直裂缝,继而决定了采用一注一采或其他井网形式。注入井与生产井都需要适当规模的压裂,在地层中制造出一定规模的裂缝,造成井与井之间裂缝的连通。天然裂缝在裂缝延展方面具有控制作用,微震监测技术在判断压裂激发方面具备关键作用。干热岩开发的独特机理包括造缝机理、注采井裂缝连通性要求、井与井之间的距离、布井先后顺序等。目前,干热岩开发还有一些技术难点需要解决。

Application principle of the hot dry rock is to hot dry rock in the formations and to take out hot water source reserves of the hot dry rock in high-temperature crustal bathyderm is high.Basic principle and technology of get a hot exchange system inside the impermeable for power generation or heating etc.Geothermal re- rocks in China are rich,and rock temperature in power generation by the hot dry rock in the de- veloped countries have relatively great progress,but development and application of the hot dry rock in China is still at the stage of probe.Hot dry rock development often adopts the system of one injection well and one production well,as well as one injection well and three production wells or two injection wells and one production well.In the system of one injection well and one production well,later adjustment was almost done,that is,another new well was drilled in the fracture system formed by the old well.Generally speaking the state of the ground stress determines fracture morphology ：horizontal fractures or vertical fractures ,and then determines the well pattern of one injection well and one production well or others.Suitable scale of fractur- ing was needed in both the injection wells and the production wells to make a certain scale of fractures in the formations,which will result in the connection of the fractures between two wells.Natural fracture has the control role on fracture propagation, and microseismic monitoring technology plays a key role on judging stim- ulation of the fracturing.The unique development mechanism of the hot dry rock includes fracture initiation mechanism,fracture connection request of the injection well and production well,the distance between two wells and precedence order on well arrangement.Now,the hot dry rock development has some technical difficulties to be solved.