CN114673479B - Based on heterogeneous state CO 2 Horizon type geothermal strengthening mining method - Google Patents
Based on heterogeneous state CO 2 Horizon type geothermal strengthening mining method Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
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- E21B43/2605—Methods for stimulating production by forming crevices or fractures using gas or liquefied gas
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Abstract
本发明公开了一种基于多相态CO2的层位式地热强化开采方法,采用“单主井改造提热—副井监测”的开采模式,大大减小了钻井成本,提高了单一钻井的利用效率;利用液态CO2注入地热层时受热后相变膨胀致裂原理增加体积改造范围,并且在相变致裂的同时,随着内部压力及温度的持续增加,使CO2气体变成处于超临界状态的CO2流体,在致裂完成后,此时使超临界状态的CO2流体与地热层换热后携带大量的地热能,最后高温超临界状态的CO2流体进入换热器内进行换热降温,使其提取的热量用于发电装置进行发电,换热完成后降温的CO2气体通过低温冷凝管降温重新液化成液态CO2,从而实现了CO2工质的闭环利用;最终提高了地热资源的整体开采效率。
The invention discloses a multi-phase CO2 -based layered geothermal intensified mining method, which adopts the mining mode of "single main well reformation and heat improvement-auxiliary well monitoring", which greatly reduces the drilling cost and improves the single drilling cost. Utilization efficiency: using the principle of phase change expansion and cracking after heating when liquid CO 2 is injected into the geothermal layer to increase the volume reformation range, and at the same time as the phase change and cracking, with the continuous increase of internal pressure and temperature, the CO 2 gas becomes The CO2 fluid in the supercritical state, after the cracking is completed, the CO2 fluid in the supercritical state will carry a large amount of geothermal energy after heat exchange with the geothermal layer, and finally the CO2 fluid in the high temperature supercritical state enters the heat exchanger. The heat exchange is carried out to cool down, so that the extracted heat is used for the power generation device to generate electricity. After the heat exchange is completed, the cooled CO 2 gas is cooled down and re-liquefied into liquid CO 2 through the low temperature condenser, thus realizing the closed-loop utilization of CO 2 working fluid; finally Improve the overall mining efficiency of geothermal resources.
Description
技术领域technical field
本发明涉及一种基于多相态CO2的层位式地热强化开采方法,主要适用于低渗透性、岩层致密的深部干热岩储层的地热高效开采。The invention relates to a multiphase CO2 -based stratum-type geothermal intensified mining method, which is mainly suitable for high-efficiency geothermal mining of deep hot dry rock reservoirs with low permeability and dense rock formations.
背景技术Background technique
受日益匮乏的资源量和环境污染的影响,传统的能源结构正面临着不可忽视的应用威胁,而频发的环境问题也给传统能源消费带来了质疑。我国地热资源十分丰富,应用潜力巨大。据统计,我国深层地热资源基数为2.09×107EJ,相当于856万亿吨标准煤。按照干热岩地热资源开采率的2%下限进行计算,深层地热能源可开采量约为17万亿吨标准煤。因此,深部地热资源开发也越来越得到世界各国及研究学者的青睐。Affected by increasingly scarce resources and environmental pollution, the traditional energy structure is facing application threats that cannot be ignored, and frequent environmental problems have also brought doubts to traditional energy consumption. my country's geothermal resources are very rich and have great application potential. According to statistics, the base of China's deep geothermal resources is 2.09×10 7 EJ, equivalent to 856 trillion tons of standard coal. Calculated according to the 2% lower limit of the exploitation rate of hot dry rock geothermal resources, the exploitable amount of deep geothermal energy is about 17 trillion tons of standard coal. Therefore, the development of deep geothermal resources is increasingly favored by countries and researchers all over the world.
根据现有地热能分布特征,一般可分为浅层地热能(地表至地下200m)、水热型地热能(地下200m-3000m)和干热岩地热能(地下3000m以深)。现有学者多提出利用双井增强型地热开采模式,通过设置至少一个注入井注入高压水对干热岩储层进行改造,增强其渗透性和流体流量,然后驱动低温工质流经改造后的储层裂隙网络进行热能的提取,并将携带热量的工质流通过设置的生产井进行提取利用。该方法在世界范围内已得到广泛应用,也取得了比较好的技术突破,但同时也存在着一些应用局限性,比如,利用高压水对干热岩储层进行改造,这一过程会消耗大量的水资源,对于一些水资源匮乏地区的干热岩储层改造具有很大的应用限制;高压水改造储层过程多受地应力影响,产生的卸压范围呈多向性,难以做到储层致裂的有效控制;常规储层改造方式的改造范围较窄,后期的工质流所流经的区间有限,很难获取得到充足的热量;并且现有采用的双井开采模式常受限于注入井的改造能力,容易出现生产接续问题。另外公开号为:CN114033346A,名称为“一种基于二氧化碳介质的深层地热开采方法”的发明专利公开了采用二氧化碳作为传热介质进行地热开采的方法,其虽然无需高压水注入,但是由于其仍然需要设置双井模式,并且还要向井内设置CO2相变致裂器进行致裂,而CO2相变致裂器安装相对较为困难,且致裂范围有限,并且其注入井内的换热介质为超临界CO2,这样不仅需要大型加热设备和加压设备,而且需要消耗大量能量,因此,这种方式也会导致地热资源的开采成本较高及换热效率较低;因此如何提供一种方法,能有效降低钻井施工复杂度及施工成本的情况下,还能有效保证地热资源开采后的换热效率,最终提高地热资源的整体开采效率,是本行业的研究方向之一。According to the distribution characteristics of existing geothermal energy, it can generally be divided into shallow geothermal energy (surface to 200m underground), hydrothermal geothermal energy (200m-3000m underground), and dry hot rock geothermal energy (under 3000m underground). Existing scholars often propose to use the double-well enhanced geothermal recovery mode to modify the hot dry rock reservoir by setting at least one injection well to inject high-pressure water to enhance its permeability and fluid flow, and then drive the low-temperature working fluid to flow through the modified geothermal reservoir. The reservoir fracture network extracts heat energy, and the working medium flow carrying heat is extracted and utilized through the set production wells. This method has been widely used all over the world and has achieved relatively good technological breakthroughs, but there are also some application limitations. For example, using high-pressure water to stimulate dry hot rock reservoirs will consume a lot of water resources, there are great limitations in the application of hot dry rock reservoir stimulation in some water-scarce areas; the process of high-pressure water stimulation reservoirs is mostly affected by in-situ stress, and the range of pressure relief produced is multi-directional, making it difficult to achieve Effective control of layer fracturing; conventional reservoir stimulation methods have a narrow stimulation range, and the later period of working fluid flow is limited, so it is difficult to obtain sufficient heat; and the existing dual-well production mode is often limited Due to the stimulation ability of injection wells, production continuity problems are prone to occur. In addition, the publication number is: CN114033346A, and the invention patent titled "a deep geothermal mining method based on carbon dioxide medium" discloses a method for geothermal mining using carbon dioxide as a heat transfer medium. Although it does not require high-pressure water injection, it still requires The double well mode is set up, and a CO 2 phase-change cracker is also installed in the well for fracturing, but the installation of the CO 2 phase-change cracker is relatively difficult, and the cracking range is limited, and the heat exchange medium injected into the well is Supercritical CO 2 , which not only requires large-scale heating equipment and pressurization equipment, but also consumes a lot of energy. Therefore, this method will also lead to high mining costs of geothermal resources and low heat exchange efficiency; therefore, how to provide a method , can effectively reduce the complexity and cost of drilling construction, and can effectively ensure the heat transfer efficiency after geothermal resources are exploited, and ultimately improve the overall exploitation efficiency of geothermal resources, which is one of the research directions of this industry.
发明内容Contents of the invention
针对上述现有技术存在的问题,本发明提供一种基于多相态CO2的层位式地热强化开采方法,能有效降低钻井施工复杂度及施工成本的情况下,还能有效保证地热资源开采后的换热效率,最终提高地热资源的整体开采效率。Aiming at the problems existing in the above-mentioned prior art, the present invention provides a multi-phase CO2 -based layer-type geothermal enhanced mining method, which can effectively reduce the complexity and construction cost of drilling construction, and can effectively ensure the exploitation of geothermal resources The final heat exchange efficiency will ultimately improve the overall exploitation efficiency of geothermal resources.
为了实现上述目的,本发明采用的技术方案是:一种基于多相态CO2的层位式地热强化开采方法,具体步骤为:In order to achieve the above object, the technical solution adopted in the present invention is: a layer-type geothermal enhanced mining method based on multiphase CO 2 , the specific steps are:
A、首先利用钻机在地面向下进行钻设,使钻孔穿过上覆地层到达干热岩储层中形成竖井,竖井分成上覆地层段和干热岩储层段,竖井直径为300-400mm,竖井井底进入干热岩储层内150-200m范围内;A. First, use a drilling rig to drill downward on the ground, so that the borehole passes through the overlying strata to reach the hot dry rock reservoir to form a shaft. The shaft is divided into the overlying stratum section and the hot dry rock reservoir section. The diameter of the shaft is 300- 400mm, the bottom of the shaft enters within 150-200m of the hot dry rock reservoir;
B、在钻机上安装定向钻头,并将定向钻头伸入至干热岩储层,使定向钻头从竖井沿同一水平方向在干热岩储层不同深度依次钻进形成三个水平钻井,且从上至下分别设定为第一水平钻井、第二水平钻井和第三水平钻井,并在退钻时排渣排浆;接着利用钻机从地面钻设监测井,使监测井的终孔位置处于第一水平钻井正上方的上覆地层内;B. Install the directional drill bit on the drilling rig, and extend the directional drill bit into the hot dry rock reservoir, so that the directional drill bit drills in sequence from the shaft along the same horizontal direction at different depths in the hot dry rock reservoir to form three horizontal drilling wells, and from From top to bottom, the first horizontal drilling, the second horizontal drilling and the third horizontal drilling are respectively set, and the slag and slurry are discharged when the drilling is withdrawn; In the overburden directly above the first horizontal well;
C、在竖井的上覆地层段和干热岩储层段交界处安装高压密封器,对竖井的干热岩储层段进行封堵;然后将绝热注液管一端和绝热抽采管一端均伸入竖井内、并穿过高压密封器,其中绝热注液管一端伸入第二水平钻井中,并在绝热注液管一端安装耐温压封隔器对第二水平钻井进行封堵;绝热抽采管一端处于竖井的干热岩储层段;C. Install a high-pressure sealer at the junction of the overlying formation section and the hot dry rock reservoir section of the shaft to seal off the hot dry rock reservoir section of the shaft; Extend into the shaft and pass through the high-pressure sealer, where one end of the heat-insulating liquid injection pipe extends into the second horizontal drilling, and a heat-resistant and pressure-resistant packer is installed at one end of the heat-insulating liquid injection pipe to seal the second horizontal drilling; heat insulation One end of the extraction pipe is located in the hot dry rock reservoir section of the shaft;
D、绝热注液管另一端与CO2泵体的出口连接,绝热抽采管另一端与换热器的进口连接,换热器的热量排出口通过传热管路与发电装置连接,换热器的流体排出口与低温冷凝管一端连接,低温冷凝管另一端与CO2泵体的进口连接,接着将监测装置送入监测井的终孔位置,监测装置通过光纤数据传输线与地面上的多源数据反演系统连接,完成多相态CO2地热开采系统的布设工作;D. The other end of the insulated liquid injection pipe is connected to the outlet of the CO2 pump body, the other end of the adiabatic extraction pipe is connected to the inlet of the heat exchanger, and the heat outlet of the heat exchanger is connected to the power generation device through the heat transfer pipeline for heat exchange The fluid discharge outlet of the device is connected to one end of the cryogenic condenser tube, and the other end of the cryogenic condenser tube is connected to the inlet of the CO2 pump body, and then the monitoring device is sent to the end hole of the monitoring well, and the monitoring device is connected to the multiple on the ground through the optical fiber data transmission line. The source data inversion system is connected, and the layout of the multiphase CO 2 geothermal recovery system is completed;
E、开始进行地热开采工作时,先启动CO2泵体一段时间,使其将低温冷凝管内的高压低温液态CO2流体经由绝热注液管注入第二水平钻井内,低温液态CO2流体在第二水平钻井内受到地热温度影响持续升温,此时液态CO2流体吸热过程中发生瞬态相变形成CO2气体,由于第二水平钻井被封堵,其产生的高压膨胀作用对第二水平钻井周围干热岩进行冲击致裂,完成一次冲击致裂过程,然后重复上述过程再启动CO2泵体一段时间,如此经过多次循环致裂过程后,使第二水平钻井周围的干热岩形成复杂的裂隙网络,同时监测装置实时对下方的地质情况进行监测,并将监测数据反馈给多源数据反演系统,多源数据反演系统根据监测数据对地热层的致裂情况进行确定,并根据致裂情况调整CO2泵体的注入压力和注入流量,直至监测到第二水平钻井通过裂隙网络分别与第一水平钻井和第三水平钻井发生贯通时,停止CO2泵体工作完成致裂过程;E. When starting geothermal exploitation, first start the CO2 pump body for a period of time, so that it can inject the high-pressure and low-temperature liquid CO2 fluid in the low-temperature condensation pipe into the second horizontal drilling through the heat-insulating liquid injection pipe, and the low-temperature liquid CO2 fluid at the first The temperature in the second horizontal drilling continues to rise due to the influence of geothermal temperature. At this time, the liquid CO 2 fluid undergoes a transient phase transition during the heat absorption process to form CO 2 gas. Since the second horizontal drilling is blocked, the high-pressure expansion generated by it has a negative effect on the second horizontal drilling. The hot dry rock around the drilling well is subjected to impact fracturing, and the impact fracturing process is completed once, and then the above process is repeated and the CO 2 pump body is started for a period of time. After several cycles of fracturing, the hot dry rock around the second horizontal drilling A complex fracture network is formed. At the same time, the monitoring device monitors the geological conditions below in real time, and feeds the monitoring data back to the multi-source data inversion system. The multi-source data inversion system determines the fracturing of the geothermal layer based on the monitoring data. And adjust the injection pressure and injection flow rate of the CO 2 pump body according to the fracturing situation until the second horizontal drilling well is monitored to pass through the fracture network to the first horizontal drilling well and the third horizontal drilling well respectively, and the CO 2 pump body is stopped to complete the work. cracking process;
F、当裂隙网络(13)将第一水平钻井、第二水平钻井和第三水平钻井相互贯通时,由于持续多次循环注入的液态CO2流体在地热温度及气化产生的压力共同作用下,液态CO2流体相变形成CO2气体会变成处于超临界状态的CO2流体,接着由于第一水平钻井和第三水平钻井内的气压较低,此时处于超临界状态的CO2流体沿着裂隙网络进入第一水平钻井和第三水平钻井内,并持续进行吸热,最终经由竖井进入绝热抽采管内;F. When the fracture network (13) connects the first horizontal well, the second horizontal well and the third horizontal well, the liquid CO2 fluid injected continuously for multiple cycles is under the joint action of the geothermal temperature and the pressure generated by gasification , the liquid CO 2 fluid phase changes to form CO 2 gas will become CO 2 fluid in supercritical state, and then due to the lower gas pressure in the first horizontal drilling and the third horizontal drilling, the CO 2 fluid in supercritical state at this time Enter the first horizontal drilling well and the third horizontal drilling well along the fracture network, and continue to absorb heat, and finally enter the adiabatic extraction pipe through the shaft;
G、高温CO2流体经过绝热抽采管进入换热器,在换热器内经过辐射换热过程将分离出来的热量通过传热管路进入发电装置进行发电,换热完成后降温的CO2气体进入低温冷凝管,通过低温冷凝管降温作用使CO2气体重新液化成液态CO2进行储藏;G. The high-temperature CO 2 fluid enters the heat exchanger through the adiabatic extraction pipe. In the heat exchanger, through the radiation heat exchange process, the separated heat enters the power generation device through the heat transfer pipeline for power generation. After the heat exchange is completed, the cooled CO 2 The gas enters the cryogenic condenser, and the CO 2 gas is re-liquefied into liquid CO 2 for storage through the cooling effect of the cryogenic condenser;
H、待换热器分离出来的热量值低于设定值时,重复步骤E至G,从而提高换热器分离出来的热量值,如此循环,最终实现对干热岩的地热开采。H. When the heat value separated by the heat exchanger is lower than the set value, repeat steps E to G, so as to increase the heat value separated by the heat exchanger, and so on, and finally realize the geothermal exploitation of hot dry rock.
进一步,所述监测装置包括微震监测探头、超声波探头和气体监测探头,且各个探头均采用热绝缘包裹方式用于隔离高温。采用这种结构能通过多种不同探头对地热层的致裂情况进行数据采集,便于后续数据处理的准确性。Further, the monitoring device includes microseismic monitoring probes, ultrasonic probes and gas monitoring probes, and each probe is wrapped in thermal insulation to isolate high temperature. With this structure, data can be collected on the fracturing of the geothermal layer through a variety of different probes, which facilitates the accuracy of subsequent data processing.
进一步,所述第一水平钻井、第二水平钻井和第三水平钻井的钻井直径均为150-180mm,钻井长度均处在200-300m范围。Further, the drilling diameters of the first horizontal drilling, the second horizontal drilling and the third horizontal drilling are all 150-180mm, and the drilling lengths are all in the range of 200-300m.
进一步,所述第一水平钻井、第二水平钻井和第三水平钻井在空间层位上的方位角误差小于5°,第三水平钻井布置在竖井井底位置,第二水平钻井和第一水平钻井分别布置在第三水平钻井上方60m、120m位置。采用这个布设,不仅便于对地热层致裂,而且能更好的实现对地热层的换热开采。Further, the azimuth error of the first horizontal drilling, the second horizontal drilling and the third horizontal drilling on the spatial horizon is less than 5°, the third horizontal drilling is arranged at the bottom of the shaft, the second horizontal drilling and the first horizontal drilling Drilling wells are respectively arranged at positions 60m and 120m above the third horizontal drilling well. Adopting this arrangement not only facilitates fracturing of the geothermal layer, but also better realizes heat exchange exploitation of the geothermal layer.
进一步,所述高压密封器最大耐受压力为150MPa,最大耐受温度为500℃。这样能保证其密封效果。Further, the maximum withstand pressure of the high pressure sealer is 150MPa, and the maximum withstand temperature is 500°C. This can ensure its sealing effect.
进一步,所述耐温压封隔器能够承受的最大温度为600℃,最大压力为200Mpa。这样能保证其密封效果。Furthermore, the maximum temperature and pressure that the temperature and pressure resistant packer can withstand is 600°C and 200Mpa. This can ensure its sealing effect.
进一步,所述绝热注液管和绝热抽采管均采用柔性材料,且能够承受的最大温度为 500℃;绝热注液管管径为80mm,绝热抽采管管径为150mm。这样设置保证通过绝热注液管注入地热层内的CO2介质处于液态,便于后续工作的开展。Further, both the heat-insulated liquid injection pipe and the heat-insulated extraction pipe are made of flexible materials, and the maximum temperature they can withstand is 500°C; the diameter of the heat-insulated liquid injection pipe is 80 mm, and the diameter of the heat-insulated extraction pipe is 150 mm. This setting ensures that the CO2 medium injected into the geothermal layer through the adiabatic liquid injection pipe is in a liquid state, which facilitates the development of follow-up work.
进一步,所述CO2泵体的注入压力可调控范围为10-70MPa,注入流量范围为5-10L/min。这种参数范围能满足致裂时对CO2泵体的调控需要,保证致裂的顺利进行。Further, the injection pressure of the CO 2 pump body can be adjusted in the range of 10-70MPa, and the injection flow range is in the range of 5-10L/min. This parameter range can meet the control requirements of the CO 2 pump during fracturing and ensure the smooth progress of fracturing.
与现有技术相比,本发明将注入井和抽采井合二为一,并且与多种相态的CO2相结合的方式,通过定向卸压技术和不同相态CO2相变时产生的能量扩大地热储层改造区域面积,联合多种监测传感器实现原位监测,保证致裂的顺利进行,提出了“单主井改造提热—副井监测”的开采模式,即只有一个井伸入地热层,无需额外再增设,监测井仅仅是处于上覆底层内,这样的方式一方面形成了能够集合储层改造、工质驱动取热和工质提热等工序为一体的单井开采方式,大大减小了钻井成本,提高了单一钻井的利用效率;另一方面利用液态CO2注入地热层时受热后相变膨胀致裂原理增加体积改造范围,并且在相变致裂的同时,随着内部压力及温度的持续增加,使CO2气体变成处于超临界状态的CO2流体,在致裂完成后(即裂隙网络连通各个钻井时),此时利用其超临界状态的强流动性、低摩阻性等优势进入裂隙网络的多尺度孔裂隙结构中使超临界状态的CO2流体与地热层换热后,携带大量的地热能,最后高温超临界状态的CO2流体通过绝热抽采管进入换热器内进行换热降温,使其提取的热量用于发电装置进行发电,换热完成后降温的CO2气体进入低温冷凝管,通过低温冷凝管降温作用使CO2气体重新液化成液态CO2进行储藏,作为后续注入的工质源,从而实现了CO2工质的闭环利用;另外通过监测井的设置,利用微震技术、声波技术和气体监测技术分别监测储层致裂改造过程和气体运移规律,借助现有的深度学习算法对海量数据进行训练预测,可为调节CO2工质不同阶段的注入参数进行有效调节,最终保证致裂的顺利进行,有效保证了地热资源开采后的换热效率,提高了地热资源的整体开采效率。Compared with the prior art, the present invention combines the injection well and the extraction well into one, and combines it with various phases of CO 2 , through directional pressure relief technology and different phases of CO 2 phase transitions to generate The energy of the geothermal reservoir can be expanded to expand the area of geothermal reservoir stimulation, and multiple monitoring sensors can be combined to realize in-situ monitoring to ensure the smooth progress of fracturing. Into the geothermal layer, there is no need for additional installations, and the monitoring well is only located in the overlying bottom layer. On the one hand, this method forms a single-well production that can integrate reservoir transformation, working fluid-driven heat extraction, and working fluid heating. method, which greatly reduces the drilling cost and improves the utilization efficiency of a single well; on the other hand, when liquid CO 2 is injected into the geothermal layer, the principle of phase change expansion fracturing after heating is used to increase the volume reconstruction range, and at the same time of phase change fracturing, As the internal pressure and temperature continue to increase, the CO 2 gas becomes a CO 2 fluid in a supercritical state. After the fracturing is completed (that is, when the fracture network connects each drilling well), at this time, the strong flow of the supercritical state is used Advantages such as high resistance and low friction enter into the multi-scale pore-fracture structure of the fracture network so that the CO 2 fluid in the supercritical state exchanges heat with the geothermal layer, and carries a large amount of geothermal energy. Finally, the CO 2 fluid in the high-temperature supercritical state passes through the adiabatic The extraction pipe enters the heat exchanger for heat exchange and cooling, so that the extracted heat is used in the power generation device to generate electricity. After the heat exchange is completed, the cooled CO 2 gas enters the low-temperature condenser tube, and the CO 2 gas is regenerated through the cooling effect of the low-temperature condenser tube. Liquefied into liquid CO2 for storage, as a source of working fluid for subsequent injection, thus realizing the closed-loop utilization of CO2 working fluid; in addition, through the setting of monitoring wells, microseismic technology, acoustic wave technology and gas monitoring technology are used to monitor reservoir fracturing In the transformation process and gas migration law, with the help of the existing deep learning algorithm to train and predict massive data, it can effectively adjust the injection parameters of different stages of CO 2 working fluid, and finally ensure the smooth progress of fracturing and effectively ensure the geothermal energy. The heat exchange efficiency after resource mining improves the overall mining efficiency of geothermal resources.
附图说明Description of drawings
图1是本发明的结构示意图。Fig. 1 is a structural schematic diagram of the present invention.
图中:1-上覆地层;2-干热岩储层;3-竖井;4-第一水平钻井;5-第二水平钻井;6-第三水平钻井;7-绝热注液管;8-高压密封器;9-耐温压封隔器;10-CO2泵体;11-绝热抽采管;12-换热器;13-传热管路;14-发电装置;15-低温冷凝管;16-裂隙网络;17-多源数据反演系统;18-光纤数据传输线;19-监测井;20-监测装置。In the figure: 1-overlying formation; 2-hot dry rock reservoir; 3-vertical well; 4-first horizontal drilling; 5-second horizontal drilling; 6-third horizontal drilling; 7-insulation liquid injection pipe; 8 -high pressure sealer; 9-temperature and pressure resistant packer; 10-CO 2 pump body; 11-insulated extraction pipe; 12-heat exchanger; 13-heat transfer pipeline; 14-power generation device; 15-low temperature condensation 16-fracture network; 17-multi-source data inversion system; 18-optical fiber data transmission line; 19-monitoring well; 20-monitoring device.
具体实施方式Detailed ways
下面将对本发明作进一步说明。The present invention will be further described below.
如图1所示,本发明的具体步骤为:As shown in Figure 1, the concrete steps of the present invention are:
A、首先利用钻机在地面向下进行钻设,使钻孔穿过上覆地层1到达干热岩储层1中形成竖井3,竖井3分成上覆地层段和干热岩储层段,竖井3的直径为300-400mm,竖井3 井底进入干热岩储层1内150-200m范围内;A. First, use a drilling rig to drill downwards on the ground, so that the borehole passes through the overlying stratum 1 to reach the hot dry rock reservoir 1 to form a
B、在钻机上安装定向钻头,并将定向钻头伸入至干热岩储层2,使定向钻头从竖井3 沿同一水平方向在干热岩储层2不同深度依次钻进形成三个水平钻井,三个水平钻井的钻井直径均为150-180mm,钻井长度均处在200-300m范围,且从上至下分别设定为第一水平钻井4、第二水平钻井5和第三水平钻井6,第一水平钻井4、第二水平钻井5和第三水平钻井6在空间层位上的方位角误差小于5°,第三水平钻井6布置在竖井3井底位置,第二水平钻井4和第一水平钻井3分别布置在第三水平钻井5上方60m、120m位置;采用这个布设,不仅便于对地热层致裂,而且能更好的实现对地热层的换热开采;并在退钻时排渣排浆;接着利用钻机从地面钻设监测井19,使监测井19的终孔位置处于第一水平钻井4正上方的上覆地层1内;B. Install the directional drill bit on the drilling rig, and extend the directional drill bit into the hot dry rock reservoir 2, so that the directional drill bit drills sequentially from the shaft 3 along the same horizontal direction at different depths in the hot dry rock reservoir 2 to form three horizontal drilling wells , the drilling diameters of the three horizontal drilling wells are all 150-180mm, the drilling lengths are all in the range of 200-300m, and they are respectively set as the first horizontal drilling 4, the second horizontal drilling 5 and the third horizontal drilling 6 from top to bottom , the azimuth error of the first horizontal drilling 4, the second horizontal drilling 5 and the third horizontal drilling 6 on the spatial horizon is less than 5°, the third horizontal drilling 6 is arranged at the bottom of the shaft 3, the second horizontal drilling 4 and The first horizontal drilling well 3 is respectively arranged at positions 60m and 120m above the third horizontal drilling well 5; adopting this arrangement not only facilitates cracking of the geothermal layer, but also better realizes heat exchange and exploitation of the geothermal layer; Slag discharge and slurry discharge; then use a drilling rig to drill a monitoring well 19 from the ground, so that the final hole position of the monitoring well 19 is in the overlying formation 1 directly above the first horizontal drilling 4;
C、在竖井3的上覆地层段和干热岩储层段交界处安装高压密封器8,对竖井3的干热岩储层段进行封堵;高压密封器8最大耐受压力为150MPa,最大耐受温度为500℃,这样能保证其密封效果;然后将绝热注液管7一端和绝热抽采管11一端均伸入竖井3内、并穿过高压密封器8,其中绝热注液管7一端伸入第二水平钻井5中,并在绝热注液管7一端安装耐温压封隔器9对第二水平钻井进行封堵;耐温压封隔器9能够承受的最大温度为600℃,最大压力为200Mpa。这样能保证其密封效果;绝热抽采管11一端处于竖井3的干热岩储层段;C. Install a high-
D、绝热注液管7另一端与CO2泵体10的出口连接,绝热抽采管7另一端与换热器11的进口连接,换热器11的热量排出口通过传热管路13与发电装置14连接,换热器11的流体排出口与低温冷凝管15一端连接,低温冷凝管15另一端与CO2泵体10的进口连接,接着将监测装置20送入监测井19的终孔位置,监测装置20通过光纤数据传输线18与地面上的多源数据反演系统17连接,所述监测装置20包括微震监测探头、超声波探头和气体监测探头,且各个探头均采用热绝缘包裹方式用于隔离高温。采用这种结构能通过多种不同探头对地热层的致裂情况进行数据采集,便于后续数据处理的准确性,完成多相态CO2地热开采系统的布设工作;所述绝热注液管7和绝热抽采管11均采用柔性材料,且能够承受的最大温度为500℃;绝热注液管7管径为80mm,绝热抽采管11管径为150mm。这样设置保证通过绝热注液管7注入地热层内的CO2介质处于液态,便于后续工作的开展;D, the other end of the heat-insulating
E、开始进行地热开采工作时,先启动CO2泵体10一段时间,使其将低温冷凝管15内的高压低温液态CO2流体经由绝热注液管7注入第二水平钻井5内,低温液态CO2流体在第二水平钻井5内受到地热温度影响持续升温,此时液态CO2流体吸热过程中发生瞬态相变形成CO2气体,由于第二水平钻井5被封堵,其产生的高压膨胀作用对第二水平钻井5 周围干热岩进行冲击致裂,完成一次冲击致裂过程,然后重复上述过程再启动CO2泵体10 一段时间,如此经过多次循环致裂过程后,使第二水平钻井5周围的干热岩形成复杂的裂隙网络16,同时监测装置20实时对下方的地质情况进行监测,并将监测数据反馈给多源数据反演系统17,多源数据反演系统17根据监测数据对地热层的致裂情况进行确定,并根据致裂情况调整CO2泵体10的注入压力和注入流量,直至监测到第二水平钻井5通过裂隙网络16分别与第一水平钻井4和第三水平钻井6发生贯通时,停止CO2泵体10工作完成致裂过程;所述CO2泵体10的注入压力可调控范围为10-70MPa,注入流量范围为5-10L/min。这种参数范围能满足致裂时对CO2泵体10的调控需要,保证致裂的顺利进行;E. When starting geothermal exploitation work, start the CO2
F、当裂隙网络16将第一水平钻井4、第二水平钻井5和第三水平钻井6相互贯通时,由于持续多次循环注入的液态CO2流体在地热温度及气化产生的压力共同作用下,液态CO2流体相变形成CO2气体会变成处于超临界状态的CO2流体,接着由于第一水平钻井4和第三水平钻井6内的气压较低,此时处于超临界状态的CO2流体沿着裂隙网络16进入第一水平钻井4和第三水平钻井6内,并持续进行吸热,最终经由竖井3进入绝热抽采管11内;F. When the
G、高温CO2流体经过绝热抽采管11进入换热器12,在换热器12内经过辐射换热过程将分离出来的热量通过传热管路13进入发电装置14进行发电,换热完成后降温的CO2气体进入低温冷凝管15,通过低温冷凝管15降温作用使CO2气体重新液化成液态CO2进行储藏;G. The high-temperature CO2 fluid enters the
H、待换热器12分离出来的热量值低于设定值时,重复步骤E至G,从而提高换热器12分离出来的热量值,如此循环,最终实现对干热岩的地热开采。H. When the heat value separated by the
上述高压密封器8、耐温压封隔器9、CO2泵体10、换热器12、发电装置14、低温冷凝管15、多源数据反演系统17和监测装置20均为现有设备或器件,能通过市场购买获得;其中多源数据反演系统17在接收到监测装置20反馈的监测数据后采用已知的深度学习算法和滤波降噪技术对监测数据进行分析处理,从而实现致裂过程的可视化。便于后续根据致裂情况及时调整CO2泵体的压力及流量。低温冷凝管15能将流入的CO2气体通过持续降温,使其相变成液态CO2流体。The above-mentioned high-
以上所述仅是本发明的优选实施方式,应当指出:对于本技术领域的普通技术人员来说,在不脱离本发明原理的前提下,还可以做出若干改进和润饰,这些改进和润饰也应视为本发明的保护范围。The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.
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