菏泽市岩溶地热井尾水回灌影响因素及流体可采量估算研究

通过在山东菏泽城区实施地下水回灌实验,对菏泽深覆型岩溶地区地热水的回灌影响因素进行分析研究,并初步估算出评价区可采量。结果可知:深覆型岩溶地热井尾水回灌效果的影响因素主要包括回灌压力、回灌水质、回灌水温、回灌工艺和热储层岩性特征等。在回灌条件下,估算可知允许开采量为6 408. 7 m^3/d,而本次单井地热井的抽水实验开采量值81. 48 m^3/r,远低于该值,说明菏泽城区地热资源丰富。研究结果为下一步的寒武-奥陶系岩溶热储开发打下基础。     

松辽盆地增强型地热系统(EGS)地热能开发热-水动力耦合过程

增强型地热系统地热能开发涉及到热和水动力的耦合,对应的温度和压力场时空变化特征是评价地热开发效果的关键问题。基于松辽盆地徐家围子深部地质条件,采用TOUGH2进行了地热能开发过程中裂隙-孔隙介质系统中温度和压力变化的数值模拟,分析了不同埋深水平情况下地热能开发的差别,研究了孔隙基质和裂隙介质的渗透率和孔隙度、岩石导热系数、井径、注入压力、注入温度及裂隙周围基质因素对地热能开发的影响。结果表明：采用定压力开发时生产井抽出控制整个区域的压力分布,压力梯度在注入井区域较大,并随着开发的进行,注入井的注入对压力的影响逐渐增大;温度由注入井到生产井逐渐增大,并随着开发的进行温度降低范围逐渐向生产井扩大;质量和热提取速率随时间逐渐减小。不同埋深位置的模拟结果显示,埋深大的温度相对较高,水的流动性较强,质量和热提取速率较高,压力和温度变化幅度均较大。裂隙系统的渗透率、注入井/生产井压力和注入温度、井径对深部地热开采过程中的压力和温度影响较大,从而影响热的提取效率;而孔隙基质的渗透率和孔隙度、裂隙介质的裂隙度和岩石的热传导系数的影响并不明显。     

南海北部白云深水区高变地温梯度砂岩渗透率定量预测

地温梯度如何影响砂岩成岩演化和储层物性变化是地学界的热点问题. 以具有高变地温梯度特征的白云深水区为例,通过分析大量不同地温梯度地区的样品,以地温梯度0.1~0.2 ℃/100 m为递进间隔,对比分析了不同地温梯度区间内不同粒度砂岩储层渗透率随埋藏深度变化的趋势,建立了砂岩渗透率的定量地质预测模型,展示了砂岩渗透率与地温梯度之间的内在联系. 结果表明,一定埋深范围内,随地温梯度升高,渗透率每下降一个数量级,砂岩埋深下限差异呈台阶式减少;相同地温梯度区间内,高成分成熟度、低塑性岩屑含量的含砾砂岩、粗粒砂岩、中粒砂岩和细粒砂岩的渗透率下降程度不同,相邻粒径砂岩等效渗透率埋深下限差异相近,随地温梯度增加,相邻粒径砂岩等效渗透率下限埋深差异呈规律性减小;低渗与特低渗砂岩储层的地层深度段随地温梯度升高而明显变小,粗粒砂岩特低渗储层的埋深下限可作为白云深水区常规油气勘探的极限深度. 研究成果对于揭示地温梯度对砂岩成岩演化作用的影响及物性演变效应具有重要的意义,对油气勘探有积极的指导作用.      

Numerical analysis of thermal fracturing in subsurface cold water injection by finite element methods

Integration of poromechanics and fracture mechanics plays an important role in understanding a series of thermal fracturing phenomena in subsurface porous media such as cold water flooding for enhanced oil recovery, produced‐water reinjection for waste disposal, cold water injection for geothermal energy extraction, and CO₂ injection for geosequestration. Thermal fracturing modeling is important to prevent the potential risks when fractures propagate into undesired zones, and it involves the coupling of heat transfer, mass transport, and stress change as well as the fracture propagation. Analytical method, finite element method, and finite difference method as well as boundary element method have been used to perform the thermal fracturing modeling considering different degrees and combinations of coupling. In this paper, extended finite element method is employed for the thermal fracturing modeling in a fully coupled fashion with remeshing avoided, and the stabilized finite element method is employed to account for the convection‐dominated heat transfer in the fracturing process with numerical oscillation circumvented. With the thermal fracturing model, a hypothetical numerical experiment on cold water injection into a deep warm aquifer is conducted. Results show that parameters such as injection rate, injection temperature, aquifer stiffness, and permeability can affect the fracture development in different ways and extended finite element method and stabilized finite element method provide effective tools for thermal fracturing simulation. Copyright © 2012 John Wiley & Sons, Ltd.     

集中采灌条件下碳酸盐岩热储群井示踪试验

地热回灌是实现地热资源可持续开发的有力措施,在世界各国已获得广泛应用,在地热资源的保护、减少资源浪费、延长地热井寿命以及减少环境污染等方面具有重要意义.天津是我国开展地热回灌比较成熟的地区之一,截至2019年底,天津市基岩裂隙型热储回灌率已达79.61％.大规模集中采灌条件下热储层渗流场的变化以及是否会影响热储温度已成为热储系统研究的前沿课题.本文以天津市东丽湖地区为例,选取1,5-萘磺酸钠作为示踪剂,在2018～2019年供暖期集中采灌期间开展了群井示踪试验,结果显示,供暖期内地热井开采量(或回灌量)、水温没有明显变化,水位除受正常采灌影响外没有明显变化,热储系统基本处于稳定状态;试验中示踪剂回收率极低,开采井和回灌井之间水力联系较差,有限的优势通道中的最大流速为448.42 m/d,优势通道的方向主要集中于北东向,与区内主要控热断裂沧东断裂及其次生断裂的发育方向一致;在现状开发利用模式下,不会造成该热储层温度的显著变化.这些认识对于指导北方古潜山碳酸盐岩热储的科学开发利用具有一定的现实意义.     

长白山仙人桥温泉断裂岩溶复合型地热成因模式

长白山仙人桥温泉是我国著名的矿泉水疗养旅游胜地,阐明其成因模式对于温泉区的进一步开发和热水资源的可持续利用具有一定的指导意义。笔者采用地质学、水文地质学和地球物理学结合的方法对其进行了系统研究。结果表明,该区属中低温对流型地热系统,地热成因模式为断裂岩溶复合型。热储层主要为古生界寒武系和奥陶系灰岩,灰岩本身的孔渗条件较差,但后期发育的构造裂缝和溶蚀裂缝却极大地改善了热储层的储集性能;盖层主要为中生界侏罗系安山岩和安山质火山碎屑岩,封闭性较好。长白山一带的大气降水沿侧向断裂和溶蚀裂缝渗入热储层中成为地下水;然后经正常大地热流加热成为地热水,热储温度为89~118℃,循环深度为2 853~3 820m;最终地热水在区内NE向与NW向断裂交汇处富集并沿导水断裂上涌形成温泉。因此,该区断裂交汇和岩溶发育的部位是地热勘探的有利部位。该结论为该区类似地热资源的勘探提供了理论依据。     

配伍性实验在西安市地热水回灌试验中的应用

西安市地热田储层为砂岩孔隙型储层,孔隙度和渗透率都比较低,很容易发生回灌堵塞现象。对西安市同层回灌水和异层回灌水的配伍性进行研究,配伍性实验结果表明:西安市地热尾水回灌到回灌井后主要的结垢类型为CaCO3,结垢量小于100 mg/L,配伍性较好,不会大量结垢而导致地热储层堵塞。     

康定-老榆林地热系统氢氧同位素迁移数值模拟分析

以康定老榆林地区地热系统为研究对象,利用TOUGH-Isotope程序进行水-热-同位素耦合数值模拟,并鉴于研究区大气降水氢氧同位素季节性明显、地震活动活跃,探讨了补给水同位素特征、热储层渗透性变化对地热系统氢氧同位素迁移过程的影响.研究结果表明氢氧同位素模拟值与研究区ZK3钻孔流出水测试值基本拟合,高温地热系统的对流-弥散作用对氢氧同位素迁移过程影响明显;研究区地热水循环条件较好,水-岩作用程度较低,导致氧同位素重化现象不明显;补给水同位素特征、热储层渗透性两个因素对地热水循环过程中的氢氧同位素分布具有明显的影响.开展地热系统流体氢氧同位素迁移过程研究,有助于提高对地热系统动态演化的定量化认识,为地热开发提供支持.      

Geothermal energy exploitation from depleted high-temperature gas reservoirs by recycling CO2:The superiority and existing problems

CO2 can be used as an alternative injectant to exploit geothermal energy from depleted high-temperature gas res-ervoirs due to its high mobility and unique thermal properties.However,there has been a lack of systematic anal-ysis on the heat mining mechanism and performance of CO2,as well as the problems that may occur during geothermal energy exploitation at specific gas reservoir conditions.In this paper,a base numerical simulation model of a typical depleted high-temperature gas reservoir was established to simulate the geothermal energy exploitation processes via recycling CO2 and water,with a view to investigate whether and/or at which condi-tions CO2 is more suitable than water for geothermal energy exploitation.The problems that may occur during the CO2-based geothermal energy exploitation were also analyzed along with proposed feasible solutions.The re-sults indicate that,for a depleted low-permeability gas reservoir with dimensions of 1000 m × 500 m × 50 m and temperature of 150℃using a single injection-production well group for 40 years of operation,the heat mining rate of C02 can be up to 3.8 MW at a circulation flow rate of 18 kg s-1 due to its high mobility along with the flow path in the gas reservoir,while the heat mining rate of water is only about 2 MW due to limitations on the injectivity and mobility.The reservoir physical property and injection-production scheme have some effects on the heat mining rate,but CO2 always has better performance than water at most reservoir and operation condi-tions,even under a high water saturation.The main problems for CO2 circulation are wellbore corrosion and salt precipitation that can occur when the reservoir has high water saturation and high salinity,in which serious salt precipitation can reduce formation permeability and result in a decline of CO2 heat mining rate(e.g.up to 24％reduction).It is proposed to apply a low-salinity water slug before CO2 injection to reduce the damage caused by salt precipitation.For high-permeability gas reservoirs with high water saturation and high salinity,the supe-riority of CO2 as a heat transmission fluid becomes obscure and water injection is recommended.     

Hypothetical thermohaline transportation study of pumping-reinjection wells in the geothermal field

In the use of geothermal energy, the reinjection of heat-depleted brines is the most important issue. The reinjection of reservoir fluid can support reservoir pressures and also allow more efficient thermal energy recovery, but at the same time many problems occur during reinjection of heat-depleted brines, among which is the precipitation of the products of reactions between reinjected fluid and the reservoir’s fluid and solid constituents. We discuss the dynamics of the reinjection of heat-depleted brines into the original reservoir using a thermohaline theoretical model using FEFLOW software, representing the effect of the difference in temperature and concentration between heat-depleted brine and reservoir fluid, regardless of the chemical reactions and assuming clean brine.     

Numerical simulation of operation performance on production and injection of a double well geothermal system in Kailu Basin,Inner Mongolia

Inner Mongolia is abundant in geothermal resources, but the development and utilization of medium-depth geothermal resources for clean heating in winter is still in the preliminary stage compared with the neighboring provinces. In this paper, a recently developed geothermal heating system using the Mesozoic sandstone reservoirs in Baokang of Kailu Basin, Eastern Inner Mongolia was investigated, a three-dimensional geological model of a pair of production and injection well was established, and numerical simulations on the long term operation performance were conducted and verified by pumping test and water level recovery test data. The effects of flow rates, the direction of wells, injection temperature and ratios on the flow field and water level in the thermal reservoir were analyzed. The results show that considering a 30-year operation period and a production rate from 90 m³/h to 110 m³/h, the optimum well spacing can be increased from 225 m to 245 m, with an average value of 235 m. With the decrease of the injection temperature, the cold front of the injection water has an increasing influence on the temperature in the production well. A complete injection or the principle of production according to injection is recommended in order to maintain the long-term operation stability. In addition, the location of the injection well should be arranged in the downstream of the natural flow field. The present results can provide a useful guide for the optimum design and performance prediction of geothermal wells, thus maintaining the production and injection balance and promoting the sustainable development and utilization of medium-depth and deep geothermal resources.     

Sub-sea-floor metamorphism,heat and mass transfer; an additional comment

Attention is drawn to the fact that the warm geothermal brines of Matupi Harbour (New Britain) are of sea water origin, contain amounts of total dissolved solids comparable to those in sea water, but are remarkably enriched in heavy metals (Ferguson and Lambert, 1972). This evidence supports the proposal that metal enriched brines, of sea water origin, may be generated in sub-sea-floor geothermal systems by a high temperature leaching process, and may form a metal enriched sedimentary component on discharge back into sea water (Spooner and Fyfe, 1973).The chloride contents of the Matupi Harbour brines are low, relative to other known hydrothermal solutions which carry comparable amounts of heavy metals in solution. This evidence indicates that high dissolved chloride contents of the order of 160000 ppm, compared with sea water which contains 19800 ppm, are not a prerequisite for a high metal carrying capacity in natural brines.     

注入水对地层伤害的评价

通过不同水样的岩心驱替实验，研究了注入水质对岩心渗透率的伤害率。结果表明：①现场注入水对岩心渗透率的伤害率大于50％；②注入处理不彻底的水后岩心渗透率的伤害变小，但伤害深度变大；③薄膜过滤后的水和处理后的水对岩心的伤害率基本相同；④注入水质应按处理后的水质指标控制。     

西宁盆地热储构造概念模型的建立

基于西宁盆地地热地质条件的研究,在Donaldson管状模型的基础上,提出的西宁盆地热储构造概念模型是大地热流为热源一低热导率岩层聚热-深循环逐渐加热受迫对流为机制-构造控水控热。进而揭示出,尽管西宁盆地地热异常分布范围较广,但也并非“遍地有热”。在生产实践中,关键是要较为准确地确定地热井的最佳构造部位和找到高渗透率的热储。     

渭河盆地新生界水气资源储层特征及存在问题分析

渭河盆地北靠鄂尔多斯地块,南依秦岭造山带,为一典型的地堑盆地,构造活动复杂,发育较厚的新生代地层,资源丰富.利用钻测录井等资料及野外调研、实验分析等方法,结合前人研究成果,对盆地新生代地层进行了重新划分界定,对水气资源类型及其赋层特征进行了深入分析.结果表明,盆地水气资源丰富,主要有地热（水）、矿泉水、地下水、水溶气、生物气、氦气、氡气、氢气等;含水层主要为古近系和新近系基岩裂隙孔隙含水层、第四系砂砾孔隙含水层,含水性好;热储层主要有红河组、白鹿塬组、高陵群（寇家村-冷水沟组）、蓝田-灞河组,总体物性较好,多为中孔-中渗储层;含气层除了和热储层一样外,还有张家坡组,其物性很好,为优质储层.对目前在盆地水气资源研究中存在的问题也进行了分析.     

沉积盆地砂岩热储回灌试验研究——以山东禹城市为例

禹城市为东营组热储地热资源开采利用集中区,因地热资源集中开采及地热尾水的直接外排,造成了水化学污染、热污染及热储层压力下降等一系列地质环境问题。本次在禹城市地热资源开发利用现状调查的基础上,在禹城市栖庭水岸开展地热回灌试验研究,回灌模式为自然同层对井回灌。根据本次回灌试验取得的数据,对回灌量与回灌压力关系、回灌对热储层水质影响、回灌对热储层温度影响规律进行了分析研究并根据拟合回灌量与水位升幅关系曲线计算了最大回灌量。分析结果表明:回灌量随压力的增大而增大,单位回灌量随回灌压力的增大呈减小趋势;回灌井因灌入了矿化度比其自身地热水矿化度高的水源,所以回灌后采集的回灌井地热水矿化度比回灌试验之前高,但因采灌井开采热储层属于同层热储,故回灌对热储层水质影响小;本次试验采灌井间距较大,故回灌对热储层温度无影响;计算确定该回灌井最大回灌量为70 m~3/h。本次回灌试验研究为禹城市地热资源可持续开发利用提供了依据。     

东营市城区地热储人工回灌条件及分区研究

地热水资源开发利用往往伴生诸多环境地质问题,人工回灌是解决这些问题的有效和重要手段。影响人工回灌效果的主要因素有地质构造复杂程度、回灌水源类型,热储厚度、渗透性能、储水能力,地热水头大小及溶气状况等。就东营市城区馆陶组、东营组地热水资源的人工回灌条件进行了论述,并利用综合方法开展了分区评价,划分出回灌条件好区、较好区、一般区和较差区。对该区地热水资源人工回灌的可行性进行了讨论,提出了建议。     

贵州省开阳县马岔河温泉水化学特征及成因

结合马岔河区域内多年的水质分析、监测资料,系统阐述了马岔河温泉水文地球化学特征,利用同位素手段,分析了马岔河温泉的水源、补给区高程;利用Na-K-Mg三角图解法判断水岩平衡状态,判断结果为马岔河温泉属于未成熟水,只能利用SiO2温标计算温泉的热浩温度。通过分析,认为其水源为大气降水,热源为深循环加热,热储温度72．33℃,热储深度为2690m。马岔河温泉的地质成因为：在正常区域地热场环境中,大气降水沿高渗透率的岩石渗入地下,深部地下水沿断层破碎带向马岔河运移,循环加热,深部地下水在马岔河断束上涌汇集,并与近源低温地下水混合,在地势低洼处出露形成温泉。     

高孔砂岩断层内部微观结构及渗透性变化规律物理模拟

在油气勘探过程中,对于小位移断层分隔油水封闭能力的控制因素研究尚浅,野外也难以获得不同变形过程的断层带结构及其渗透性变化规律.因此,以高孔隙度纯净砂岩人造岩心为研究对象,采用自主研发的“高压~低速环形剪切装置”开展实验,实验后样品取心分别进行覆压孔渗测试、纳米CT扫描、铸体薄片分析等分析测试.以有效正应力和断层位移为实验变量开展了多组环剪实验,其研究结果表明:宏观上断层面上可观察到明显擦痕与粉末状碎裂岩,微观上确定了断层带内碎裂作用导致的颗粒粒度降低与颗粒的定向排列是孔渗降低的主要原因,断层带渗透率小于10 mD,较母岩降低2~3个数量级.随着断层有效正应力或断层滑动位移增加,断层带碎裂程度增大且粒径和孔径减小,断层带厚度增大,孔隙度和渗透率逐渐减小.这一结果可为小位移断层侧向封闭能力与油气勘探领域的研究奠定理论基础.      

广安市铜锣山背斜三叠纪岩溶热储结构特征及热水成因研究

为探讨广安市铜锣山背斜三叠纪岩溶热储特征、地热水水化学与同位素组成、热储温度及地热水循环机理,采用地热钻探、水化学与同位素取样测试、热水溶质组分图解分析等手段和方法,开展了地热水成因的研究工作。结果表明:研究区三叠纪碳酸盐岩热储结构相对完整,热储盖层、热储层和热储下部隔水层形成独立的地热水文地质单元。岩溶地热水水化学类型主要为SO₄-Ca·Mg和SO₄-Ca型,富含F、Sr、Li、B和SiO₂物质,其水源补给为大气降水,补给区位于铜锣山以北的大巴山一带,深部地热水补给高程大于1 100 m,补给区年均温度为9 ℃。热储温度为56~76 ℃,热水循环深度为2 013~3 030 m。地热水在循环过程中,主要发生碳酸盐岩和蒸发岩溶解、冷热水混合过程,且冷水混入比例大于80%。结合区域地热地质条件,构建了研究区地热水成因概念模型。