Numerical Simulation Study on the Effect of Horizontal Well Reservoir Stimulation for Gas Hydrate Production

A new gas hydrate reservoir stimulation method of in-situ fracturing with transient heating is proposed, in line with analysis of the technological bottlenecks faced by marine gas hydrate production. This method injects the developed chemical reagents into a hydrate reservoir through hydraulic fracturing, releasing heat during the chemical reaction to increase the hydrate decomposition rate. The chemical reaction product furthermore has a honeycomb structure to support fractures and increase reservoir permeability. Based on the geological model of natural gas hydrate in the South China Sea, three development methods are simulated to evaluate hydrate production capacity, consisting of horizontal well, fractured horizontal well and in-situ fracturing with transient heating well. Compared with the horizontal well, the simulation results show that the cumulative gas production of the fractured horizontal well in one year is 7 times that of the horizontal well, while the cumulative gas production of in-situ fracturing with transient heating well is 12 times that of the horizontal well, which significantly improves daily efficiency and cumulative gas production. In addition, the variation patterns of hydrate saturation and temperature-pressure fields with production time for the three exploitation plans are presented, it being found that three sensitive parameters of fracture conductivity, fracture half-length and fracture number are positively correlated with hydrate production enhancement. Through the simulations, basic data and theoretical support for the optimization of gas hydrate reservoir stimulation scheme has been provided.

A review: Enhanced recovery of natural gas hydrate reservoirs

Natural gas hydrate(NGH)is a highly efficient and clean energy,with huge reserves and widespread distribution in permafrost and marine areas.Researches all over the world are committed to developing an effective exploring technology for NGH reservoirs.In this paper,four conventional in-situ hydrate production methods,such as depressurization,thermal stimulation,inhibitor injection and CO2 replacement,are briefly introduced.Due to the limitations of each method,there has been no significantly breakthrough in hydrate exploring technology.Inspired by the development of unconventional oil and gas fields,researchers have put forward some new hydrate production methods.We summarize the enhanced hydrate exploiting methods,such as CO2/N2–CH4 replacement,CO2/H2–CH4 replacement,hydraulic fracturing treatment,and solid exploration;and potential hydrate mining techniques,such as self-generating heat fluid injection,geothermal stimulation,the well pattern optimization of hydrate exploring.The importance of reservoir stimulation technology for hydrate exploitation is emphasized,and it is believed that hydrate reservoir modification technology is a key to open hydrate resources exploitation,and the major challenges in the process of hydrate exploitation are pointed out.The combination of multiple hydrate exploring technologies and their complementary advantages will be the development trend in the future so as to promote the process of hydrate industrialization.

Progress in Research of Gas Hydrate

It is of great significance to study gas hydrate because of following reasons. （1） Most organic carbon in the earth reserves in the form of natural gas hydrate, which is considered as a potential energy resource for the survival of human being in the future. （2） A series of novel technologies are based on gas hydrate. （3） Gas hydrate may lead to many hazards including plugging of oil/gas pipelines, accelerating global warming up, etc. In this paper, the latest progresses in exploration and exploitation of natural gas hydrate, the development of hydrate-based technologies including gas separation, gas storage, CO2 sequestration via forming hydrate, as well as the prevention of hydrate hazards are reviewed. Additionally, the progresses in the fundamental study of gas hydrate, including the thermodynamics and kinetics are also reviewed. A prospect to the future of gas hydrate research and application is given.

Application of fracturing technology to increase gas production in low-permeability hydrate reservoir:A numerical study

Low temperature and low permeability are the challenges for the development of hydrate reservoirs in permafrost.The ice produced around the production well caused by high depressurization driving force reduces the gas production,and it is necessary to reduce the effect of ice production on gas production.In this work,a new combination of fracturing technology and depressurization method was proposed to evaluate the gas production potential at the site DK-2 in Qinghai-Tibet Plateau Permafrost.A relatively higher intrinsic permeability of the fracture zone surround the horizontal production well was created by the fracturing technology.The simulation results showed that the fracture zone reduced the blocking of production ice to production wells and promoted the propagation of production pressure.And the gas production increased by 2.1 times as the radius of the fracture zone increased from 0 to 4 m in 30 years.Nearly half of the hydrate reservoirs were dissociated in 30 years,and greater than 51.7%of the gas production was produced during the first 10 years.Moreover,production behaviours were sensitive to the depressurization driving force but not to the thermal conductivity.The growth of gas production was not obvious with the intrinsic permeability of the fracture zone higher than 100 m D.The effect of ice production on gas production by fracturing technology and depressurization method was limited.

The Research about Storage and Transportation of Natural Gas Based on LNG Technology

Nowadays, we are in great lack of the technology theory for the storage and transportation of gas hydrate. Under this condition, after checking out related theory of these, we established the technology roadmap of the storage and transportation of gas hydrate by LNG technology. Study has shown that the technology of LNG is more saving than that of pipeline. Then we came out with the new idea of storage and transportation of hydrate by LNG technology.

Advances of experimental study on gas production from synthetic hydrate reservoir in China

China has entered the area of new normal economy which requires the harmonious development of energy consumption,environmental protection and economic development.Natural gas hydrate is a potential clean energy with tremendous reserve in China.The successful field test of marine hydrate exploitation in South China Sea created a new record of the longest continuous gas production from natural gas hydrate.However,the corresponding fundamental research is still urgently needed in order to narrow the gap between field test and commercial production.This paper reviewed the latest advances of experimental study on gas production from hydrate reservoir in China.The experimental apparatus for investigating the performance of hydrate dissociation in China has developed from one dimensional to two dimensional and three dimensional.In addition,well configuration developed from one tube to complicated multi-well networks to satisfy the demand of different production models.Besides,diverse testing methods have been established.The reviewed papers preliminary discussed the mechanical properties and the sediment deformation situation during the process of hydrate dissociation.However,most reported articles only consider the physical factor,the coupled mechanism of physical and chemical factor for the mechanical properties of the sediment and the sand production problem should be studied further.

海洋天然气水合物降压开采装备现状与技术探讨

在南海神狐海域采用降压法成功实施了2次天然气水合物试采,在深水浅软地层水合物钻采技术上取得了多项重大技术突破,但仍面临单井产量低、开采配套装备复杂及经济适用性弱等问题。为了配套神狐海域第3次降压法试采开采方案,系统梳理了降压法开采技术对开采装备的影响因素,对比分析了常规油气开采的水下采油树结构适应性,提出了一套适用于深水天然气水合物开采的水下卧式采气树关键技术理论;形成的“一体式”集成化采气树本体、双穿越结构水下穿越器、失效安全型液控水下阀门及驱动器、复合电液控制系统等技术,可满足海洋天然气水合物开发装备质量轻、水合物二次结冰封堵干预、井下作业工况监测和远程控制等要求。所得结果可为海洋天然气水合物长期稳定、可控开采的配套装备开发提供借鉴。

Theoretical Progress and Key Technologies of Onshore Ultra-Deep Oil/Gas Exploration

Oil/gas exploration around the world has extended into deep and ultra-deep strata because it is increasingly difficult to find new large-scale oil/gas reservoirs in shallow–middle buried strata. In recent years, China has made remarkable achievements in oil/gas exploration in ultra-deep areas including carbonate and clastic reservoirs. Some (ultra) large-scale oil and gas fields have been discovered. The oil/gas accumulation mechanisms and key technologies of oil/gas reservoir exploration and development are summarized in this study in order to share China’s experiences. Ultra-deep oil/gas originates from numerous sources of hydrocarbons and multiphase charging. Liquid hydrocarbons can form in ultradeep layers due to low geothermal gradients or overpressures, and the natural gas composition in ultra-deep areas is complicated by the reactions between deep hydrocarbons, water, and rock or by the addition of mantle- or crust-sourced gases. These oils/gases are mainly stored in the original highenergy reef/shoal complexes or in sand body sediments. They usually have high original porosity. Secondary pores are often developed by dissolution, dolomitization, and fracturing in the late stage. The early pores have been preserved by retentive diageneses such as the early charging of hydrocarbons. Oil/gas accumulation in ultra-deep areas generally has the characteristics of near-source accumulation and sustained preservation. The effective exploration and development of ultra-deep oil/gas reservoirs depend on the support of key technologies. Use of the latest technologies such as seismic signal acquisition and processing, low porosity and permeability zone prediction, and gas–water identification has enabled the discovery of ultra-deep oil/gas resources. In addition, advanced technologies for drilling, completion, and oil/gas testing have ensured the effective development of these fields.

Quick Assessment of Potential Hydrate Promoters for Rapid Formation

Hydrate technology has advanced to greater proportions: implementing the high latent heats as refrigerant, safe carbon capture as carbon sequestration in hydrates, purifying rare gases in hydrates, and safe efficient transport of energy using rapid hydrate formation. These account for only a small amount of the fundamental understanding of gas hydrates and the use of such a novel technology. A quick and broad analysis of novel hydrate promoters is needed to assess the potential of other promoter agents. This will improve the understanding of rapid hydrate formation and fundamental ideas related to the kinetics and formation of hydrates. There are still hundreds of other surfactants that have not been identified for rapid formation. The insurmountable endeavor deters many from trying as it can be like finding a needle in a hay stack. This almost futile endeavor of correctly identifying a surfactant as a promoter agent without doing a formation test can be accomplished with recent techniques. Using Raman and a liquid hydrocarbon (Cyclo-pentane), surfactants may shift the sample’s peak towards the hydrate peak (890 cm–1), thereby identifying it as a choice surfactant for rapid formation of hydrates. With a broad survey of surfactants, understanding fundamental science and engineering kinetics for hydrates will be easily achieved. Finding more effective and novel surfactants for hydrate formations will broaden the field of hydrates and self-assembling crystallization. As hydrate technology broadens, interdisciplinary fields can contribute expertise from surface science to spectroscopy leading to geological formations and engineering kinetics.

回顾、探索与开创——第十届天然气水合物国际会议评述

第十届天然气水合物国际会议(ICGH10)于2023年7月9—14日在新加坡召开,参会人数700余人,由新加坡国立大学主办。ICGH10共收到摘要538份,分为292份口头报告和246份墙报展示。ICGH10总结了近6年来水合物相关领域的研究进展,本文主要就能源勘探与开发、流动保障、水合物应用技术3个方面重点评述:作为一种清洁低碳能源,天然气水合物在基础理论和试采工程方面取得了许多突破性进展,但距商业化开发利用仍具有一定距离;为实现油气管道的高效输送,与水合物堵塞有关的流动保障技术受到广泛研究,研发了许多环境友好型的水合物动力学和热力学抑制剂;水合物应用技术在碳封存、水处理和气体储运方面也逐步由实验研究走向商业应用。本文对会议内容做简要梳理,旨在介绍国际上水合物领域的最新研究及发展趋势。

Comparative Study and Analysis of the Development of Shale Gas between China and the USA

In the 21st century, the shale gas is a greatly potential unconventional gas resource, which can serve as an important complement to conventional energy sources, and can effectively alleviate the energy pressure of the world. The development of shale gas in the USA is in the developing stage with advanced exploitation technology and huge reserves. Compared with the USA, the development of shale gas in China is still in the early stage. The development of shale gas is both an opportunity and a challenge. Chinais in the exploration and preparation stage of resource assessment and exploration. This paper presents the importance of the formation principle of shale gas and the energy application, and compares the progress of shale gas studies, exploitation technology as well as the study hot-points betweenChinaand theUSA. Meanwhile, this paper states the difficulties and challenges with the development of shale gas inChina.

天然气水合物勘探开发技术研究进展

天然气水合物是一种具有巨大潜在开发价值的海洋新型能源矿产。近 30年来 ,各国相继开展了海洋天然气水合物的勘探和开发技术的研究 ,天然气水合物的勘探技术日趋成熟 ,而开发技术基本上还都处于实验阶段。与国外正在形成的天然气水合物研究热潮相比 ,我国对天然气水合物研究尚处于起步阶段。

海域天然气水合物开采的地质控制因素和科学挑战

目前,国际上对天然气水合物产状、分布和特征的认识已取得显著进展,开展了一系列陆地多年冻土区和海域天然气水合物试采,但天然气水合物开采仍面临科学挑战。本文在综述全球天然气水合物勘探开发现状的基础上,阐述了天然气水合物储层分类及其开采的地质控制因素,提出了海域天然气水合物有效经济开采面临的资源评价、开采技术方法、储层地质参数和工程地质风险等4方面的科学挑战。要实现海域天然气水合物的有效经济开采,资源评价是基础,开采技术方法是关键。判定天然气水合物储层是否可采需要精确的储层地质参数,能否实现有效开采取决于工程地质风险的控制。

天然气水合物试采：从实验模拟到场地实施

天然气水合物研究的终极目标是对其进行有效的开发利用,即实现长期安全、高效地开采,而水合物试采只是迈出了第一步。数十年的室内水合物开采方法实验及其数值模拟研究取得了显著的成果,为天然气水合物试采奠定了坚实的基础。加拿大、美国等国家先后在陆地冻土区进行了水合物试采工作,试验成果为海域水合物试采提供了宝贵的经验。2013年和2017年,日本、中国先后在不同海域实施了天然气水合物试采,并取得了成功,这是天然气水合物研究的一个里程碑式的进步,标志着天然气水合物开采技术研究从室内实验模拟逐步转到产地实施。本文回顾了各种水合物开采方法的原理及其模拟实验成果,简要介绍了水合物开采数值模拟方法与进展,评述了水合物试采的前期关键技术准备及场地实施效果,讨论了每种技术方法的局限性及面临的挑战,并针对海洋天然气水合物开采面临的科学与技术问题提出了建议。

水合物法储运天然气技术及其应用前景

从天然气水合物的制备、储存、运输和分解四个方面介绍了水合物储运的相关技术。与其他天然气储运技术进行了比较,认为水合物法储运天然气是一种高效、经济、安全的储运方式,并对NGH技术的应用前景进行了展望。

水力输送法开采海底浅层天然气水合物技术研究

海洋天然气水合物占全球水合物总储量的99%,海洋天然气水合物大部分沉积在海底浅层没有良好的覆盖层,无法采用开采传统油气资源的方法进行开采。为了开采海底浅层天然气水合物,分析了海洋天然气水合物的存在类型及地质特征,探讨了目前开采海洋天然气水合物的理论方法及局限性。根据海底天然气水合物成矿的地质特点及水合物的物理特性,提出了以水力输送技术为主要理论的海洋浅层天然气水合物开采方法。该方法克服了其他方法开采海底天然气水合物面临的技术困难,为海洋天然气水合物的开采提供了技术基础及理论支撑。

中国非常规天然气资源基础与开发技术

中国非常规天然气资源丰富,合理有效地开发可为中国经济的可持续发展提供能源保障。致密砂岩气藏远景资源量超过12×1012m3,已经实现规模开发;煤层气勘探在高阶煤中取得突破;页岩气研究刚刚起步,四川盆地、塔里木盆地、鄂尔多斯盆地等具有良好的页岩气成藏和开发条件;在中国南海多处发现天然气水合物存在的证据。但是,由于非常规天然气地质条件具有复杂性和特殊性,现有的部分勘探开发技术适用性差、不够成熟,加之低渗透储层单井产量低等因素,严重制约了非常规天然气开发利用的步伐。因此应加强以下工作:研发不同类型致密砂岩气藏的开发技术;优选煤层气有利目标区及扩大勘探开发规模;研发适合高阶煤层气田的高效勘探开发关键技术;调查页岩气资源分布并查明成藏主控因素;开展天然气水合物资源评价。

青海天然气水合物的特征及其开发约束

运用综合分析的方法初步研究了青海陆域天然气水合物的开发方法,认为天然气水合物特性以及其赋存的地质、地理条件制约着开发利用.可以通过采用安全可靠的具有针对性的技术有效开发陆域天然气水合物藏;木里地区天然气水合物采用CO2置换法为主导的开采方法是可行的.可以从开发前缜密筹划,加大勘探力度,开发新方法,制定法律法规,编制应急预案,开发中控制和严密监测工程过程等措施,防止或降低天然气水合物开发过程中的风险和损失.

基于ICP技术的天然气水合物开采方案

天然气水合物(NGH)矿产储量巨大,燃烧后几乎不产生任何残渣,是一种高效利用的清洁能源。为了提出天然气水合物切实可行的开采方案,对天然气水合物成藏特点进行分析,通过当前室内研究的天然气水合物开采方法比较,并考虑到真实开采过程中可能出现的地层破坏问题,在CO_2乳状液置换天然气水合物中CH_4实验和页岩油ICP开采技术的启发下,最终制订出一套具有井工厂特点的天然气水合物开采方案。研究得出:ICP技术核心工艺冷冻墙、加热井井网布置能有效克服热散失,并持续提供热量促进天然气水合物分解。CO_2乳状液置换技术能在高效产出CH_4情况下形成CO_2水合物,防止地层因为天然气水合物分解而产生的地层破坏。注采监测系统的部署能实时监控生产反应过程,可操作性强,控制精度高。

天然气水合物射流破碎工具及其配套工艺技术

针对中国海洋天然气水合物(以下简称水合物)储藏埋藏浅和胶结性弱的特点,急需开发一系列保障水合物安全、经济、绿色、高效开采的工艺技术和配套工具。为此,提出了一种在不改变水合物储层温度和压力条件下的射流破碎流化开采水合物的技术思路,同时,开展了射流破碎水合物配套喷嘴工具的设计、室内实验与优化。进而基于室内实验探索了喷嘴射流破碎工作压降、排量、上提下放喷嘴速度和趟数等施工参数与破碎水合物孔眼直径和破碎速率之间的关系,建立了水合物射流破碎流化开采工艺现场施工工程图版。在中国南海荔湾3井采用该方法进行了生产验证。结果表明:(1)水合物射流破碎流化开采工艺技术提高了水合物开采生产效率、保护了储层底层安全,降低了水合物开采能耗;(2)水合物射流破碎喷嘴工具破碎形成的孔径规整、破碎颗粒返排效果好,无领眼时喷嘴射流破碎下放速度不超过7.1 m/h;(3)水合物射流破碎流化开采工程图版解释了射流破碎工况和施工参数对射流破碎水合物孔径和破碎速率的影响规律,为水合物试采施工工艺参数选择提供了参考;(4)水合物射流破碎流化工艺在荔湾3井试采成功,验证了射流破碎流化开采工艺的可行性和其应用于水合物商业开采的广阔前景。