Development of exploration methods for reservoir characterization in conduction dominated geothermal play types

地热储是一种绿色能源，通常用于近期火山或构造活动的高热流地区。增强型或工程化地热系统(EGS)技术允许从中等热流到低热流的水库提取热量，不仅大大提高了世界各地的地热潜力，也大大提高了加拿大的地热潜力。虽然用于基岩利用的EGS，即所谓的热干岩，已经研究了几年，但在热水沉积含水层中利用热液资源还处于早期阶段。艾伯塔省拥有以传导热传输为主的地热沉积类型。这一提议是艾伯塔省应用地热研究的开始，目的是评估以传导为主的地热圈闭类型；其中对流体流动、渗透率和孔隙度的地质控制；以及确定地热使用的有利钻探地点和支付区的过程和方法。根据Moeck新的地热类型目录(已提交)，有三种以传导为主的地热类型：(1)受岩相控制的克拉通内盆地中的热沉积含水层；(2)主要受断层控制的造山带和前陆盆地中的热沉积含水层；(3)无明显地层流体的结晶基底岩。本建议将研究这三种类型，但重点应放在第二种类型(造山带和前陆基础)上。在项目1中，将研究落基山脉前缘山脉露头类似物的断裂带尺寸和与断层抛掷相关的渗透率分布。应确定断层分带的尺寸，以及它们与每一带的断层运动学、渗透率和孔隙度的关系。这将有助于反射地震数据的构造解释，在反射地震数据中，只有断层段是可识别的。所采用的方法将包括详细的断层带构造地质制图，重点是破裂网络和用于测量岩石物理参数的岩石取样。岩石学薄片分析旨在确定影响孔隙度和渗透率的微观过程。这两个方面的研究数据将被整合到3D地质图中。在项目2中，渗透率分布的岩相控制应通过采用Thomas-Stieber方法的测井来识别，该方法允许识别非均质砂岩中的清洁砂层。干净的砂岩通常代表高孔隙度的区段，因此也就是产层的位置。对产层进行定量化，有助于圈定层状砂岩中的高产、吸水带。将对薄片进行岩石学分析，以确定孔隙度是否受页岩颗粒(即原生孔隙度)或溶解-再结晶缝(即次生孔隙度)控制。页岩类型也将通过能谱伽马测井识别，并与岩石学结果相结合，以改进用于地热储层评估的Thomas-Stieber方法。项目3涉及一种新的概念，即使用超临界二氧化碳作为高效的热流体，利用低热流基岩用于地热应用。阿尔伯坦基岩的孔隙度、渗透率、体积模数、导热系数和热容量应作为温度、压力和岩性的函数来表征。此外，超临界二氧化碳的密度、粘度、导热系数和热容将在与结晶基岩潜在有效利用相关的温度和压力下确定。这一提议的结果将与世界范围内以传导为主的地热利用类型的利用概念相关。

Geothermal reservoirs are a green energy resource commonly utilized in high-heat flow areas with recent volcanic or tectonic activity. Enhanced or Engineered Geothermal Systems (EGS) technology allows heat extraction from reservoirs of average to low heat flow and has significantly increased not only the world-wide but also Canada’s geothermal potential. While EGS for basement rock utilization, known as hot-dry rock, has been studied since several years, the use of hydrothermal resources in hot sedimentary aquifers is in its early stages. Alberta hosts geothermal play types that are dominated by conductive heat transport. This proposal is the start of applied geothermal research in Alberta to evaluate conduction dominated geothermal play types; the geologic controls therein on fluid flow, permeability and porosity; and the processes and methods to determine favorable drill sites and pay zones for geothermal use. According to the new geothermal play type catalog of Moeck (submitted), there are three conduction dominated geothermal play types: (I) hot sedimentary aquifers in intracratonic basins that are lithofacies controlled, (II) hot sedimentary aquifers in orogenic belts and foreland basins that are predominantely fault controlled, and (III) crystalline basement rock with no significant formation fluids. These three play types shall be studied in this proposal; however, the focus on research shall be on the second type (orogenic belts and foreland basis). In Project 1, outcrop analogues in the Rocky Mountain Front ranges shall be studied for fault zone dimensions and fault throw related permeability distribution. The dimensions of fault zonation shall be determined, along with their relation to fault kinematics, permeability and porosity in each zone. This will assist structural interpretation of reflection seismic data, where only the fault throw is identifiable. Methods employed will include detailed structural geological mapping of fault zones with emphasis on fracture networks and rock sampling for measuring petrophysical parameters. Petrographic thin section analysis aims to determine micro-scale processes that influence porosity and permeability. Data from these two aspects of the study will be integrated into 3D geological maps. In Project 2, lithofacies controls on permeability distribution shall be identified by well logs employing the Thomas-Stieber method, that allows the identification of clean sand layers in heterogeneous sandstones. Clean sandstones represent generally high-porosity sections and, thus, the location of pay zones. The quantification of pay zones may help to delineate high productivity and injectivity zones in laminated sandstone. Thin sections will be petrographically analysed to determine if the porosity is controlled by shale particles (i.e. primary porosity) or dissolution-recrystallization seams (i.e. secondary porosity). Shale types will be also identified by spectral gamma logs and integrated with petrographic results to improve the Thomas-Stieber method for geothermal reservoir evaluation. The Project 3 deals with a new concept that uses supercritical CO2 as efficient thermal fluid for utilizing low heat flow basement rock for geothermal applications. Albertan basement rocks shall be characterized on porosity, permeability, bulk modulus, thermal conductivity and heat capacity as a function of temperature, pressure and lithology. Additionally, the density, viscosity, thermal conductivity and heat capacity of supercritical CO2 will be determined at temperatures and pressures relevant for potential efficient use from crystalline basement rock. The results from this proposal will be relevant for utilization concepts in the wide range of conduction dominated geothermal play types worldwide.