Research progress on temperature field evolution of hot reservoirs under low-temperature tailwater reinjection

This paper focuses on the study of the evolutionary mechanism governing the temperature field of geothermal reservoir under low-temperature tailwater reinjection conditions,which is crucial for the sustainable geothermal energy management.With advancing exploitation of geothermal resources deepens,precise understanding of this mechanism becomes paramount for devising effective reinjection strategies,optimizing reservoir utilization,and bolstering the economic viability of geothermal energy development.The article presents a comprehensive review of temperature field evolution across diverse heterogeneous thermal reservoirs under low-temperature tailwater reinjection conditions,and analyzes key factors influ-encing this evolution.It evaluates existing research methods,highlighting their strengths and limitations.The study identifies gaps in the application of rock seepage and heat transfer theories on a large scale,alongside the need for enhanced accuracy in field test results,particularly regarding computational effi-ciency of fractured thermal reservoir models under multi-well reinjection conditions.To address these shortcomings,the study proposes conducting large-scale rock seepage and heat transfer experiments,coupled with multi-tracer techniques for field testing,aimed at optimizing fractured thermal reservoir models'computational efficiency under multi-well reinjection conditions.Additionally,it suggests integrat-ing deep learning methods into research endeavors.These initiatives are of significance in deepening the understanding of the evolution process of the temperature field in deep thermal reservoirs and enhancing the sustainability of deep geothermal resource development.

Study on the geothermal production and reinjection mode in Xiong County

The large karst geothermal field of Xiong County,which is located to the south of geothermal field in Niutuozhen,features huge geothermal resources and favorable condition for development and utilization.Because of the long-term extensive production,the pressure of geothermal reservoir continues to decline and some geothermal wells even face the danger of scrapping.To relieve the fall in pressure of geothermal reservoir and achieve the sustainable development and utilization of geothermal field in the long run,reinjection experiment is conducted in the geothermal field of Xiong County and a three-dimensional hydrothermal coupled numerical model was constructed.The reinjection experiment showed that the mode of one production well and one reinjection well can be achieved in this geothermal field.The numerical simulation is used to forecast and compare the change in pressure field and temperature field under different production and reinjection modes and concludes that the most opotimized production and utilization mode is the concentrated production-reinjection mode,and the most opotimized production-reinjection combination mode is the shallow production and shallow reinjection mode which can ensure the sustainable development and utilization of geothermal resources in the long run.

Formation blockage risk analysis of geothermal water reinjection:Rock property analysis,pumping and reinjection tests,and long-term reinjection prediction

The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new drilled geothermal well in Xining basin China is taken as an example to investigate the formation blockage risk due to the movable clay and sand particles in pores.The physical properties of the reservoir rocks were analyzed,a series of pumping and reinjection tests were conducted,and the longterm reinjection performance of the well was predicted by numerical simulation based on the test fitting.The results show that the geothermal reservoir rocks are argillaceous and weakly cemented sandstones with a content of movable clay and sand particles up to 0.18–23.42 wt.%.The well presented a high productivity of 935–2186 m3?d-1 at a pressure difference of 0.7–1.62 MPa in the pumping tests associated with a large amount of clay and sand particles produced out,while in the reinjection test,only a low injectivity of 240–480 m3?d-1 was observed at an injection pressure of 0.2–0.6 MPa with the clay and sand particles near the wellbore move into deep.According to the prediction,under conditions of a blockage risk,the injectivity of the well will start to decline after 100 days of injection,and in the third year,it will decrease by 59.00%–77.09%.The influence of invasion of pretreated suspended particles and scale particles can be neglected.Under conditions of a high blockage risk,the injectivity of the well will decrease significantly in the first 20–30 days,with a decline of 75.39%–78.96%.Generally,the higher the injection pressure or rate,the greater the decrease in injectivity of the well caused by particle blockage.Pump lifting is an effective measure to remove the well blockage which can be used regularly.

Clogging mechanism in the process of reinjection of used geothermal water: A simulation research on Xianyang No.2 reinjection well in a super-deep and porous geothermal reservoir

In the process of geothermal exploitation and utilization, the reinjection amount of used geothermal water in super-deep and porous reservoir is small and significantly decreases over time. This has been a worldwide problem, which greatly restricts the exploitation and utilization of geothermal resources. Based on a large amount of experiments and researches, the reinjection research on the tail water of Xianyang No.2 well, which is carried out by combining the application of hydrogeochemical simulation, clogging mechanism research and the reinjection experiment, has achieved breakthrough results. The clogging mechanism and indoor simulation experiment results show: Factors affecting the tail water reinjection of Xianyang No.2 well mainly include chemical clogging, suspended solids clogging, gas clogging, microbial clogging and composite clogging, yet the effect of particle migration on clogging has not been found; in the process of reinjection, chemical clogging was mainly caused by carbonates(mainly calcite), silicates(mainly chalcedony), and a small amount of iron minerals, and the clogging aggravated when the temperature rose; suspended solids clogging also aggravated when the temperature rose, which showed that particles formed by chemical reaction had a certain proportion in suspended solids.

An Experimental Study on Bio-Clogging in Porous Media during Geothermal Water Reinjection

To study the mechanism of bio-clogging in a porous medium during the reinjection of geothermal water and to improve reinjection efficiency, an indoor one-dimensional reinjection experiment was conducted based on the geological model of the geothermal reinjection demonstration project in Dezhou City. The biological process of porous media clogging was investigated by analyzing the variation of permeability within the medium, the main indexes of nutrient salts, and the content of extracellular polymeric substances (EPS). High-throughput sequencing, based on 16S rRNA, was used to analyze the characteristics and succession of microbial communities during the reinjection of geothermal water. The results of the study show that significant bio-clogging occurs during the reinjection of geothermal water, with an increase in the heterogeneity of the thermal reservoir medium, and a decrease in permeability. The extent of clogging gradually reduces with an increase in seepage path. Thus, thermal reservoir clogging is more serious closer to the water inlet. With an increase in the duration of reinjection, the permeability of the porous medium undergoes three stages: “rapid”, “decline-slow”, and “decrease-stable”. The results show that the richness and diversity of the bacterial community increase and decrease, respectively, during the reinjection process. Bacterial community succession occurs, and the bacterial communities mainly include the Proteobacteria and Bacteroidetes phyla. Pseudomonas and Devosia are respectively the dominant bacteria in the early and late stages of geothermal water reinjection.

A New Method for the Dynamic Reserves of Gas Condensate Reservoir Using Cyclic Gas Injection Based on the Effects of Reinjection Ratio and Water Influx

As we all know, cyclic gas injection is one of the most effective development methods to improve condensate oil recovery. When dealing with the calculation of the reserves, the injection-production differences and water influx create great influence on the accuracy. Based on the existing research, we proposed a new material balance equation which considered the differences of composition between produced and injected fluids and the effect of water influx, and a solution was provided in this paper. The results of the method are closer to the actual situation because they are built on the law of conservation of mass, and the using of curve fitting method can not only avoid the use of water influx coefficient but also obtain the water influx rate and reserves at the same time. The YH-23 gas condensate reservoir is taking as a typical subject to do the research, which has been exploited by cycle gas injection for 14 years. Three different methods are used to calculate the reserves, and the results show that the method proposed in this paper has minimum error of 2.96%.

Reinjection Tests in Bedrock Geothermal Reservoir of Tianjin

By the end of 2002, there are about 219 production wells (including 12 reinjection wells) in Tianjin. The annual production rate is 1.5×10 7 m 3 and the reinjection rate is 1.66×10 6 m 3. The main side effect anticipated from reinjection is the cooling of the reservoir. It is necessary to estimate the thermal breakthrough time in different distances between injection production wells. This paper describes the 2 D mass and heat transfer in the heterogeneous fractured rocks. The equations that arise for each grid block must be linearized. The main reinjection model is simulated by a program of the TOUGH2 to analyze the change of the temperature field and predict the pressure and heat break through. The tracer test is very important for understanding the transportation pathway and transport channel/space in the doublet system, and estimating the possible cooling resulted from the injection processes.

采灌均衡条件下地热资源潜力评价方法探讨——以雄安新区碳酸盐岩热储为例

回灌是保障地热资源可持续开发利用的关键手段,而采灌均衡条件下地热资源潜力评价方法研究对地热资源的可持续开发利用具有重要意义。本文通过引入热突破和考虑回灌条件下单井开采权益保护半径的概念,提出了回灌条件下地热资源可开采量的评价方法,并以雄安新区雾迷山组碳酸盐岩热储层为例,分别计算了未考虑回灌条件和考虑回灌条件下的地热流体可开采量、可开采热量及折合标煤量。结果显示采用开采系数法计算的未考虑回灌条件下的可开采量要远小于考虑回灌条件下的可开采量;考虑回灌条件下三种方法的结果对比为:热突破法>考虑回灌条件下单井开采权益保护半径(消耗15%)>考虑回灌条件下单井开采权益保护半径(热储温度下降2℃),考虑地热资源的可持续性以及对热储环境严格保护要求,按照考虑回灌条件下单井开采权益保护半径方法计算的雄安新区雾迷山组热储地热开采量更为适宜。目前全国各地陆续出台相关政策要求实施地热回灌,该方法的提出为科学评价各地回灌条件下的地热可开采量提供了技术支撑。

地热井砂岩热储回灌堵塞机理及解堵研究

地热井回灌是制约水热型地热持续开发的“卡脖子”难题,特别是砂岩热储的回灌更为艰难。为揭示制约砂岩热储回灌过程中面临的堵塞难题,以陕西关中渭河盆地某“一采一灌”模式砂岩地热井为例开展试验研究,探究砂岩热储回灌过程中的4类堵塞机理,并提出相应解堵措施。结果表明:碳酸盐类、部分铝硅酸盐类和铁类矿物沉淀受温度影响较大,地层温度的升高会加速其化学堵塞的形成;随温度的上升,悬浮物堵塞和化学堵塞会构成协同效应。同时悬浮物颗粒布朗运动速度也因温度上升而增大,使堵塞更严重;回灌产生气体堵塞的原因主要是:大体积气泡进入储层内部难、气泡直径与底层喉道大小相当;腐生菌和铁细菌是成微生物堵塞的主要微生物。通过加入阻垢剂可有效防止化学堵塞,采取多级过滤可减缓物理堵塞,在回灌系统中加入自动排气装置可防止气体堵塞,对尾水进行灭菌处理降低微生物堵塞风险。经过现场回暖季试验,采取的解堵措施应用于目标地热井后的回灌率达100%,降低了回灌过程中可能发生的堵塞对回灌带来的不良影响。

尕斯高盐油藏污水配聚阳离子对聚合物溶液黏度影响的主控因素

根据青海油田尕斯区块回注污水矿化度较高的特点,以山东宝莫生产的聚合物为研究目标,系统探讨了从聚合物驱采出水中的Na^(+)、K^(+)、Ca^(2+)、Mg^(^(2+))、Fe^(2+)、Fe^(3+)等6种离子对聚合物溶液的黏度和稳定性影响的变化规律,并提供了回注污水配聚主要研究方法。结果表明:导致聚合物黏度降低的主要控制因素是高价阳离子,其影响顺序从大到小的次序是Fe^(2+)、Fe^(3+)、Mg^(^(2+))、Ca^(2+)、Na+、K+;而高价阳离子对聚合物溶液黏度稳定性影响顺序从大到小的次序则是:Fe^(2+)、Ca^(2+)(Mg^(^(2+)))、Fe^(3+)、Na^(+)(K^(+))。研究结果展示了回注污水配聚中阳离子对聚合物溶液黏度的响应机理,为聚合物驱技术提供了理论指导。

基于“深地-井下-地面”联动的煤矿矿井水处理利用模式初探

煤矿矿井水的高效低耗处理有助于推动煤炭资源的安全、高效开采。现有矿井水井下处理工艺选择受限、处理量小,地面处理占地面积大、运行成本高,矿井水处理后外排至地表又会产生高额的排水费。本文在总结分析煤矿矿井水处理技术现状基础上,提出了“深地-井下-地面”联动的煤矿矿井水处理利用模式:对矿井涌水通过“井下-地面”协同的方式进行高效低耗处理,处理后的矿井水部分用于矿区生产和矿区居民生活,其余部分则进行深地回灌或外排。首先介绍了该模式的基本原理;然后从水质、水量、水文、地质、地下建筑结构和回灌工程可行性对矿井水回灌工程的适用性进行评估和分析;最后介绍了不同水质矿井水处理技术和“井下-地面”协同处理技术体系,尤其针对回灌含水层选择、回灌施工作业、回灌试验、回灌水质模拟、回灌安全性分析等进行总结。

海上油田污水回注井高效解堵技术研究与应用

针对污水回注井酸化效果不理想的问题,利用岩心流动实验、悬浮物含量及粒径测试、X射线衍射对堵塞情况进行了分析。在此基础上,利用填砂管流动和岩心溶蚀实验研发了一套兼具污油清洗与高溶蚀率的酸液体系。此外,结合储层特征优化了酸液置放工艺。结果表明,污油和固体悬浮物在近井地带形成的复合堵塞物是造成储层堵塞的主要原因;1%水基清洗剂洗油率达到86.44%,高溶蚀酸对固体悬浮物溶蚀率达到89.77%,二者复配体系能够快速瓦解油泥小球;化学微粒分流剂可对储层形成有效暂堵分流,且酸化后自动溶解。该技术矿场应用8井次,平均视吸水指数提高1.74倍。该技术适用于污水回注井解堵,并为提高海上污水回注井酸化效果提供理论和实践依据。

钻屑回注泵液力端有限元分析

岩屑回注技术是有效处理钻井废弃物以及消除其对环境影响的重要手段。但由于岩屑回注浆体中含有大量微小颗粒,在回注过程中对于回注泵液力端的磨损较大,导致岩屑回注泵寿命较短。为此,通过ANSYS数值模拟软件的FLOTRAN CFD模块分析液力端内的流场分布,分析发现:吸入工况下,流体流经吸入凡尔时流道过流面积最小,所形成的流速最高;排出工况下,流体在排出凡尔左侧壁面形成最大流速,且在出口附近产生漩涡。液力端基体材料采用沉淀硬化性不锈钢合金,延长了液力端凡尔周围材料的耐磨性,延长回注泵使用寿命。

基于时序参数分析的砂岩热储回灌特征变化研究——以山东临清市为例

为促进山东省临清市地热资源循环利用,开展了地热水回灌工程。针对采暖期前与采暖期两种情形的回灌情况,监测了开采井及回灌井的水量、水温、水位及井口压力等,并基于时序参数分析了回灌能力及最大回灌量、开采井温度场、水质变化和回灌堵塞程度。结果表明:本次施工的回灌井能够满足单井100%回灌,单井自然回灌量可达121~227 m^(3)/h;总体上开采井地热水温度表现为在供暖期上升、供暖末期下降的趋势;由于井位深度差别,在供暖期前后,开采井矿化度比回灌井分别高约45.34%和17.33%;经过一个供暖季的回灌,虽然在回扬过程中渗透系数有一定的改善,但仍由0.7699 m/s降至0.3254 m/s,有明显变小的趋势。

海上平台超临界CO_(2)管道泄漏扩散规律实验研究

CO_(2)封存是实现中国“双碳”目标的有效技术途径之一,海上CO_(2)封存通常依托海上油气平台管道回注,CO_(2)回注过程中可能发生泄漏而严重影响作业人员安全。以恩平15-1海上平台为研究对象,开展超临界CO_(2)泄漏扩散规律实验研究。通过缩比设计,搭建与恩平15-1相应的物理模型实验平台,利用相似理论和量纲分析方法,设计了超临界CO_(2)泄漏扩散参数,开展了海上平台管道CO_(2)在不同泄漏压力(1.5~3.0 MPa)、泄漏孔径(0.5~6.2 mm)、泄漏方向(水平、竖直、斜45°)及环境风速(0~0.5 m/s)下的相似模型实验,研究泄漏CO_(2)在平台上的扩散情况及浓度分布规律。结果表明:压力和环境风速的变化,会影响CO_(2)泄漏后的近场射流,但对其远场扩散的影响较小;CO_(2)浓度会在泄漏约20 s后达到峰值并保持稳定,不会随泄漏时间的增加而增大;泄漏口径会显著影响泄漏口轴向CO_(2)浓度的分布规律。研究结果为海上平台CO_(2)泄漏监测与安全防护设计提供了参考。

含油污泥资源化处理及利用研究进展

介绍含油污泥的组成和污染危害。简述了罐底油泥、落地油泥和炼油厂“三泥”等三种含量较大的油泥来源和特点。着重分析了热解法、表面活性剂法、回注调剖技术、乳液法等传统含油污泥资源化处理热点技术的工艺技术原理,相关工艺的优点和局限性以及在国内外的应用现状。探讨了微波辐射和超声处理法等两项新兴处理油泥的技术,意图为含油污泥资源化处理提供参考建议。

永久式光纤监测技术在海上首口二氧化碳回注井的应用

近期南海东部海域恩平油田我国海上首口二氧化碳回注井正式投产,采油分离出来的二氧化碳气体被烘干压缩后回注至储层进行封存。为确保注入期间的安全性需要实时掌握注入参数判断井下情况,采用永久式分布式光纤监测技术,实现了全井筒温度剖面及井底压力的实时动态监测。现场应用结果表明:分布式光纤温度监测剖面与地层梯度测试温度剖面误差0.1%,光纤压力计监测结果与注入压力、地层压力误差0.05%,根据光纤数据监测的分布解释结果可反演二氧化碳回注剖面,从而指导注气参数动态调整。

影响岩溶热储采出温度的开采参数敏感性研究——以河南清丰地区为例

采出温度是影响地热能有效利用率的关键指标,采出温度越高,热储开发效果越好。岩溶热储作为一种重要的地热储层类型,其采出温度受到储层参数的影响。以河南清丰地热田奥陶系岩溶热储为例,通过建立热储地质模型并利用7口地热井资料,进行基于热流和井储耦合的数值模拟研究,探讨储层地质条件和回灌参数对采出温度的影响。研究结果发现,断层的存在加速了热储中低温区向生产井的扩散,导致热突破时间的提前。在开采后期,有断层情况下采出温度较高,且变化曲线斜率远高于无断层情况,表明断层有助于提高清丰地区热平衡时的采出温度,最终有利于增加采热量。目前,一般认为,注采井距越小采出温度越低。但是,当回灌速率高于50 kg/s时,随着开采时间的增加,采出温度呈现快速下降趋势,注采井距835 m下的采出温度甚至高于1000 m的情况。最后,确定清丰地区特定场景下的最优回灌参数组合为:回灌温度20℃、回灌速率50 kg/s、注采井距835 m。本研究结果将为清丰地区或其他类似岩溶热储开发方案的制定提供有益指导。

热储特征对砂岩热储采灌井距的影响-以济阳坳陷为例

水热型地热资源的回灌式开采是公认的地热可持续开采方式,而采灌井距是地热项目中需要着重关注的问题,以避免开采井中的热突破现象。回灌水在热储中的运移取决于热储特征,也就是储层的透水能力,主要指热储的孔隙度、渗透率及砂泥岩组合关系等参数。基于济阳坳陷典型地热田的储层数据,采用Tough2为核心的Petrasim软件建立数值模型,系统研究了储层孔隙度、渗透率及单砂体厚度对热储中回灌水的运移以及温度场的影响。模拟结果显示:(1)储层孔隙度对回灌压力与采灌井距几乎没有影响;(2)储层渗透率对采灌率和采灌压力影响较大,控制着热储的回灌能力,但对采灌井距没有影响;(3)多次叠置的薄砂层热储中的泥岩隔层影响回灌水运移,在多层薄砂叠置的热储中回灌水水平运移距离远,温度影响范围更大,应扩大采灌井距。该研究对地热开发项目的可持续运行具有指导意义。