Hydrogen, clean, efficient and zero-carbon, is seen as a most promising energy source. The use of existing gas pipelines for hydrogen–natural gas transportation is considered to be an effective way to achieve long-distance, large-scale, efficient, and economical hydrogen transportation. However, the pipelines for hydrogen–natural gas transportation contain lots of impurities (e.g., CH4, high-pressure H2, H2S and CO2) and free water, which will inevitably lead to corrosion and hydrogen embrittlement. This paper presents a systematic review of research and an outlook for corrosion and hydrogen embrittlement in hydrogen–natural gas pipeline transportation. The results show that gas-phase hydrogen charging is suitable for hydrogen–natural gas transportation, but this technique lacks technical standards. By contrast, the liquid-phase hydrogen charging technique is more mature but has large deviation from the engineering reality. In the hydrogen–natural gas transportation pipelines, corrosion and hydrogen embrittlement are synergetic and competitive, but the failure mechanism and change law when corrosion and hydrogen embrittlement coexist remain unclear, which need to be further clarified by experiments. The failure mechanism is believed to be mainly sensitive to three key factors, i.e., the H2S/CO2 partial pressure ratio, the hydrogen blending ratio, and material strength. The increase of the three factors will make the pipeline materials more corrosive and more sensitive to hydrogen embrittlement. The research findings can be used as a reference for research and development of long-distance hydrogen–natural gas transportation technology and will drive the high-quality development of the hydrogen–natural gas blending industry.
The Sulige Gas Field in the Ordos Basin is the largest tight gas field in China, with proved reserves exceeding 2 x 1012 m3. As the main contributor to gas production in PetroChina Changqing Oilfield Company, The Sulige Gas Field is in the stage of stable production. Maximizing the stable production period is a focus and challenge for the gas field now. To address a series of problems influencing the efficient development of Sulige gas field, such as large-scale remaining gas reserves between wells/layers and low ratio of employed reserves, the main technologies for enhanced gas recovery (EGR) of tight gas reservoirs were developed by multidisciplinary research with respect to development geology, reservoir engineering, drilling and production process, and surface gathering and transportation. Experiments were conducted on reservoir description and remaining gas characterization, well pattern thickening optimization, vertical well separate-layer fracturing, horizontal-well multi-stage multi-cluster volume fracturing for their improvement and upgrading. The orientation of EGR for tight gas reservoirs is proposed. The following results are obtained. First, well pattern thickening optimization is the most important EGR method, which can increase the recovery rate by more than 6%. Second, based on continuous upgrading and promotion, either of reservoir stimulation technology and drainage gas recovery technology can increase the recovery rate by more than 2%. The gathering and transportation technology which further reduces the wellhead pressure can increase the recovery rate by about 1.5%. Third, the EGR technology should be oriented to maximize the quantity of employed reserves, especially by way of new technologies such as fine remaining gas characterization, well pattern/type optimization, crosslayer fracturing of a multi-thin-layer reservoir by horizontal wells, intelligent drainage gas recovery, and multi-stage pressurization. It is concluded that the development of key EGR technologies will help increase the recovery rate of The Sulige Gas Field by 10%-15%, and will provide an effective support for The Sulige Gas Field to maintain the production at 300 x 108 m3/a for a long term and for the Changqing gas province to increase the production to 500 x 108 m3/a, which will ultimately ensure the national energy security. (c) 2023 Sichuan Petroleum Administration. Publishing services by Elsevier B.V. on behalf of KeAi Communication Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Engineering practices show that installation of oscillators on drillstring can effectively reduce the axial drag and inhibit stick-slip vibration in horizontal drilling. However, the mechanisms of axial drag reduction and stick-slip vibration inhibition of oscillators have not been fully revealed, and there is a lack of effective optimization design methods of vibration parameters. To solve the above problems, the mechanical models of drillstring with drag reduction oscillators are firstly built, which include axial vibration model in sliding drilling mode and stick-slip vibration model in rotary drilling mode. The nonlinear relationship between friction force and velocity is considered in the mechanical models. Next step, the optimal design models of vibration parameters are estab-lished, in which the drag reduction efficiency and the stick-slip reduction efficiency are taken as the objective functions respectively, and drillstring fatigue, hydraulic loss and so on are the constraint conditions.The optimal design models are solved with orthogonal experimental design. Finally, the above models are applied to hori-zontal drilling engineering in Chinese Jimsar oilfield. The results show that oscillators can significantly reduce the total friction forces on drillstring and keep a more stable weight on bit (WOB) in sliding drilling mode, and inhibit the stick-slip vibration of drillstring and fluc-tuation amplitude of WOB. The primary factors affecting the drag reduction efficiency in sliding drilling mode are vibration amplitude and number of oscillators, whereas the primary factors affecting stick-slip reduction efficiency in rotary drilling mode are rotary speed of drillstring and WOB. It is recommended to install 3 os-cillators on bottom hole assembly of drillstring with vibration amplitude of 40 kN, rotary speed of 162 r/min, and the average WOB of 171 kN in case study, and then the drag reduction efficiency and the stick-slip reduction efficiency are respectively 37.47% and 74%.
The transient simulation technology of natural gas pipeline networks plays an increasingly prominent role in the scheduling management of natural gas pipeline network system. The increasingly large and complex natural gas pipeline network requires more strictly on the calculation efficiency of transient simulation. To this end, this paper proposes a new method for the transient simulation of natural gas pipeline networks based on fracture-dimension-reduction algorithm. Firstly, a pipeline network model is abstracted into a station model, inter-station pipeline network model and connection node model. Secondly, the pressure at the connection node connecting the station and the inter-station pipeline network is used as the basic variable to solve the general solution of the flow rate at the connection node, reconstruct the simulation model of the inter-station pipeline network, and reduce the equation set dimension of the inter-station pipeline network model. Thirdly, the transient simulation model of the natural gas pipeline network system is constructed based on the reconstructed simulation model of the inter-station pipeline network. Finally, the calculation accuracy and efficiency of the proposed algorithm are compared and analyzed for the two working conditions of slow change of compressor speed and rapid shutdown of the compressor. And the following research results are obtained. First, the fracture-dimension-reduction algorithm has a high calculation accuracy, and the relative error of compressor outlet pressure and user pressure is less than 0.1%. Second, the calculation efficiency of the new fracture-dimension-reduction algorithm is high, and compared with the nonlinear equations solving method, the speed-up ratios under the two conditions are high up to 17.3 and 12.2 respectively. Third, the speed-up ratio of the fracture-dimension-reduction algorithm is linearly related to the equation set dimension of the transient simulation model of the pipeline network system. The larger the equation set dimension, the higher the speed-up ratio, which means the more complex the pipeline network model, the more remarkable the calculation speed-up effect. In conclusion, this new method improves the calculation speed while keeping the calculation accuracy, which is of great theoretical value and reference significance for improving the calculation efficiency of the transient simulation of complex natural gas pipeline network systems.
Research on the enhanced gas recovery (EGR) technology is urgently needed in most of China's major gas fields due to low recovery in their late development stages. To promote progress in ERG theory and technology, this paper establishes a unified and universal model for gas recovery evaluation, analyzes the key factors affecting the gas recovery, and expects the prospect of EGR. The results are obtained as follows. First, the production degree of reserves, pressure drawdown sweep efficiency and pressure depletion efficiency are key factors affecting the gas recovery, which is the product of the coefficients corresponding to these factors. Second, according to the development practice of Anyue Longwangmiao gas reservoir, Kela 2 gas field, Sulige gas field and Southern Sichuan shale gas, it is estimated that the recovery of conventional water-driven gas reservoirs and unconventional gas reservoirs (incl. tight gas and shale gas) can be improved by 6–15 percentage points by increasing the production degree of reserves, the pressure drawdown sweep efficiency and pressure depletion efficiency. Third, it is proposed that clarifying the EGR mechanism, developing new EGR methods, and promoting the field test of EGR technologies are directions for theoretical and technical researches. The study results provide a theoretical foundation for EGR. The EGR methodologies for different types of gas reservoirs provide technical support for improving gas recovery and stable production of existing gas fields, promote healthy and rapid development of natural gas industry in China and provide guidance for guaranteeing national energy security.
Oil and gas production systems have the characteristics of high operation and maintenance risk and great accident influence. With the deep integration of informationization and industrialization, the development direction and necessary choice of the oil and gas industry is to develop the oil and gas production system into the interconnected, multi-domain interactive cyber-physical intelligent system. In order to avoid or reduce the complex, diverse and potentially unknown safety risks in the process of oil and gas production, improve the safety and reliability of oil and gas production system and increase the production efficiency, this paper analyzes the safety problems occurring in the intelligentization process of oil and gas production system and constructs a system from the perspective of operation and maintenance based on key elements of intelligent safe operation and maintenance technology, combined with the typical production scenarios in the oil and gas production industry. And the following research results are obtained. First, the connotation of intelligent safe operation and maintenance technology is clarified, the key elements and existing problems and challenges of intelligent safe operation and maintenance technology are analyzed, and the “1-2-3-4-5-6” intelligent safe operation and maintenance technology system of oil and gas production system is constructed, which empowers six key technologies with key elements of oil and gas production to realize the essential safety of oil and gas production system. Second, the intelligent safe operation and maintenance technology actively promotes the application and implementation of condition monitoring, health management, risk assessment, intelligent early warning technologies in typical production scenarios such as drilling and extraction, storage and transportation, refining and chemical industry in up, middle and down streams of oil and gas production. Third, in view of the characteristics of oil and gas production system under digital transformation, it is proposed to develop the intelligent safe operation and maintenance technology with the functions of intelligent decision-making, active prevention and comprehensive safety in the future to help the safe construction in the field of oil and gas production and promote the safe and healthy development of the oil and gas industry. In conclusion, the research on intelligent safe operation and maintenance technology system of oil and gas production system is conducive to the safe construction in the field of oil and gas production, which will not only provide technical support for the realization of trouble-free oil and gas production system, but also provide reference for the intelligent development of the world oil and gas industry.
Enhanced geothermal system (EGS) is subject to the comprehensive effects of multiple physical fields during the long-term heat extraction process, including hydraulic (H), thermal (T), mechanical (M) and chemical (C) fields. The embedded discrete fracture model (EDFM) can effectively simulate the variations of flow, temperature, mechanical and concentration fields in fractured reservoirs. At present, however, the thermo-hydro-mechanical-chemical (THMC) coupling model based on EDFM is less researched. In this paper, the THMC coupling model of fractured reservoir is established based on EDFM by considering the changes in reservoir heterogeneity and physical properties as well as water–rock reactions. Then, the spatiotemporal evolution of flow, temperature, displacement and concentration fields in the operation process of EGS is simulated and analyzed. And the following research results are obtained. First, when the permeability of the basement rock is low, the production temperature decrease during exploitation is gradual, allowing EGS to maintain a high exploitation temperature for an extended period. However, lower permeability may result in a decrease in the quality flow rate from production wells, thereby affecting net heat extraction power. Second, when fracture permeability or fracture opening changes, EGS can output higher temperature stably for a certain period and then the temperature decreases at different amplitudes. When the fracture permeability increases to a certain value or the fracture opening decreases to a certain value, the influence of the change in fracture parameters on production temperature gets weak. Third, After 40 years of EGS operation, considering variable property fluids results in a 22 °C lower exploitation temperature compared to using constant property fluids, and considering water–rock reactions results in a 15 °C lower exploitation temperature, with a 12.5 % increase in reservoir average porosity. In conclusion, when researching a long-term operating EGS, it is necessary to comprehensively consider the influences of reservoir rock parameters, physical properties of injected fluid, water–rock reaction and other factors. And in the future, attention shall be paid to the two-way coupling of chemical reaction and mechanical deformation of other mineral compositions in the reservoir to the hydro-thermo-chemical field influence, so as to provide more accurate and reliable prediction for the engineering development and utilization of EGS reservoirs.
Exploration and development practices have proved that staged volumetric fracturing stimulation in horizontal wells is a key technology for tight sandstone gas development, and reservoir sweet spot is an important basis for the perforation position selection and staged fracturing in the process of well location deployment and reservoir stimulation. Tight sandstone reservoirs are usually characterized by sandstone and mudstone interlayers with different thicknesses, and complex natural fracture distribution and geostress state. It is hard to predict “geological-engineering” dual sweet spots, and these two kinds of sweet spots are usually in different zones. As a result, there lacks a basis for the optimization of fracturing parameters to stimulate tight sandstone reservoirs. This paper establishes a geological sweet spot prediction model which takes into account total hydrocarbon content, reservoir porosity and other factors, then puts forward a 3D multi-scale engineering sweet spot evaluation method which takes into account lithology, fracture morphology, fracture mechanical behavior, and dilatation and shear dilation effect, and finally a “geological-engineering” dual sweet spot evaluation model for tight sandstone reservoirs. Two wells in the tight sandstone gas field in the Linxing Block of the Ordos Basin were selected as a case, and the dual sweet spot profiles, fracturing pressure and SRV were compared and analyzed. The results show that: 1) shear dilation angle influences the distribution of engineering sweet spots at the most in the study area, followed by dissipated energy, elastic modulus and fracture energy; 2) the geological sweet spot zone with a high coefficient is not necessarily the pay zone with high shale gas production; 3) the engineering sweet spot zone with a high coefficient needs lower fracture pressure and can be stimulated relatively sufficiently; 4) high-quality geological sweet spots and high-quality engineering sweet spots are poorly consistent in spatial location. In conclusion, the stimulation of tight sandstone gas reservoirs shall take geological sweet spot as the basis and engineering sweet spot as the guarantee, and the distribution of dual sweep spots should be considered comprehensively. The multi-scale “geological-engineering” dual sweet spot evaluation method proposed in this paper provides important technical support for the prediction of sweet spots of the tight sandstone gas and the optimization of development schemes in the study area.
The operation parameters and well layout parameters of aquifer thermal energy storage (ATES) system directly influence the thermal energy storage performance. How to optimize the parameters to obtain the optimal process scheme is of great significance to promote the field application of ATES. Taking the thermal storage performance of shallow aquifer as the optimization objective, this paper compares the influence degrees of key factors on thermal storage performance by means of gray correlation analysis (GCA), and prepares the optimal thermal storage scheme by using the multi-objective optimization method. The following results are obtained. First, the great difference between inlet temperature and aquifer weakens the thermal storage capacity of the system, while the thermal interference between thermal storage wells of the same type is favorable for thermal storage capacity instead. Second, aquifer thickness and well number have a greater impact on the thermal loss rate, while injection rate and well spacing have a significant influence on the thermal recovery rate. The inlet temperature has the least effect on both of them. Third, the optimal thermal storage scheme is the single well system with inlet temperature of 25 °C, aquifer thickness of 106.597 m and injection rate of 30 kg/s. In conclusion, the influence degrees of the key parameters on thermal loss rate and thermal recovery rate are different, so in order to improve the thermal storage performance, equilibrium optimization is necessary between both of them. In addition, the optimization scheme effectively expands the thermal storage volume, and reduces the heat loss while improving the thermal recovery, with thermal loss rate and thermal recovery rate of the whole system optimized by 12.69% and 3.19% respectively on the basic case, which can provide a reference for the rational design of ATES system.
管道泄漏是天然气管网系统运行过程中常见的故障之一,准确、快速地对泄漏点进行定位是及时发现并预防安全事故扩张的重要举措.为此,首先提出了考虑基准点—修正点两阶段的天然气管道泄漏定位新框架;其次,基于时域有限差分法构建了含伪泄漏点的天然气管道状态估计模型并采用联邦卡尔曼滤波器求解估计序列,并得到基准点;最后,定义了泄漏条件可信度对估计序列进行时延—分布一致性度量,作为权重得到修正点,实现了天然气管道的泄漏定位.研究结果表明:①所提出的天然气管道两阶段泄漏定位方法可以实现对管道微小泄漏(2％)的有效定位,解决了传统的基准点定位方法与空间步长选取强相关的问题;②所提出的联邦卡尔曼滤波信息分配系数设定方法,解决了因观测路径不同导致的子滤波器观测噪声差异问题;③所提出的基于动态时间规整算法的时延度量方法,可定量描述完整的泄漏量估计序列的响应速度;④所提出的基于时延—分布一致性度量的条件可信度权重概念,可以将泄漏量估计序列的时间信息与波形信息解耦并分别量化,能有效反映出泄漏发生在不同序列对应的伪泄漏点之间的依赖关系.结论认为,该方法提高了管道泄漏的检测、识别、定位的速度与精度,为天然气管道的泄漏定位提供了理论与技术支撑,具有重要的经济价值与社会效益.
近年来,四川盆地渝西地区大安区块上奥陶统五峰组—下志留统龙一 1 亚段连续获得多口高产工业气井,展示了该区块页岩气良好的勘探开发前景.但由于该区块页岩埋藏深,勘探程度低,深层优质页岩段沉积微相类型、储层特征及其空间展布规律不清,页岩气有利区优选依据不充分,制约了该区页岩气的深化勘探与开发.为此,通过岩心观察、扫描电镜、地球化学与物性测试、含气量测定和核磁共振等实验手段分析,结合钻测井资料,研究了大安区块五峰组—龙一 1 亚段各小层地质特征及储层展布规律,建立了深层页岩气有利区评价标准,优选了深层页岩气勘探有利区.研究结果表明:①高碳硅质页岩微相和高碳含黏土硅质页岩微相是最优质页岩气储层发育的沉积微相,主要发育于五峰组—龙一 13 小层.②龙一 11—龙一 14 小层孔隙度平均超过 4%,储集性好;五峰组—龙一 13 小层超大孔和裂缝较发育,所占比例分别为 66%和 25%.③五峰组—龙一 13 小层脆性矿物平均含量为 55%,可压性好;含气量平均值不低于 4.0 m3/t,含气条件较好;龙一 11—龙一 13 小层各层平均总有机碳含量超过 3.0%,生烃条件好;地层压力系数普遍大于 1.90.结论认为:①五峰组—龙一 13 小层页岩储层品质最优;②Ⅰ类、Ⅱ类和Ⅲ类页岩气有利区资源量分别为3 775.78×108 m3、2 970.05×108 m3、599.83×108 m3;③该区深层页岩气勘探潜力大,是四川盆地重要的天然气产能接替区,其中临江向斜为下一步页岩气勘探的最有利区.
Multi-cluster perforation and multi-staged fracturing of horizontal well is one of the main technologies in volumetric fracturing stimulation of unconventional oil and gas reservoirs, but unconventional reservoirs in China are generally of strong heterogeneity, which causes different fracture initiation pressures in different positions of lateral, making it difficult to ensure the balanced fracture initiation and propagation between clusters in multi-cluster perforating. It is in urgent need to precisely evaluate the difference in rock strength in lateral and determine the well section with similar rock strength to deploy fractures, so as to reach the goal of balanced stimulation. Based on the drilling and logging data, this paper establishes an unsupervised clustering model of mechanical specific energy of bit at the bottomhole the lateral. Then, the influence of drill string friction, composite drilling and jet-assisted rock breaking on the mechanical specific energy is analyzed, and the distribution and clustering categories of bottomhole mechanical specific energy with decimeter spatial resolution are obtained. Finally, a fracture deployment optimization method for horizontal well volumetric fracturing aiming balanced stimulation is developed by comprehensively considering inter-fracture interference, casing collar position, plug position, and clustering result of bottomhole mechanical specific energy. The following results are obtained. First, compared with brittleness index, Poisson's ratio and stress difference, perforation erosion area is in a stronger correlation with the mechanical specific energy, and the mechanical specific energy can effectively characterize the difference in the amount of proppant injected into the perforation clusters in the lateral, so it can be served as one of the important indicators for the selection of fracture deployment position. Second, the drilling and logging data cleaning and smoothing and the clustering number selection by the elbow method are the key steps to obtain the clustering results of bottomhole mechanical specific energy, which can tell the difference in the mechanical specific energy with decimeter-level resolution. Third, the interval with mechanical specific energy within 10% of the average value in the section is selected for deploying perforation clusters, and the compiled computer algorithm can automatically determine the optimal position of fracturing section and cluster, so as to realize the differential design of stage spacing and cluster spacing. In conclusion, the research results can further improve the fractures deployment efficiency and balanced stimulation of volumetric fracturing in unconventional oil and gas reservoirs, and this technology is expected to provide ideas and new methods for the fracture deployment optimization of horizontal well volumetric fracturing in unconventional oil and gas reservoirs.
1.目的 随着四川盆地油气勘探目标向隐蔽性地质目标转移,对地震资料保真度和分辨率提出更高要求.地震检波器是油气地震勘探关键设备之一,直接关系到地震资料品质的优劣.理想条件下,检波器接收到的信号反映了表土真实的机械振动情况,但实际的地震波接收过程受检波器自身性能及检波器表土耦合问题的制约,会影响接收到的地震波动力学特征信号.因此,笔者基于外界噪声投射原理、检波器与表土耦合响应影响因子分析,提出了四川盆地地震采集检波器"体耦合"埋置技术.
目前深层页岩气储层压裂缝网复杂程度普遍偏低,多簇裂缝非均衡起裂延伸现象普遍,在一定程度上制约了页岩气的规模效益开发.为此,从多级双暂堵角度入手,提出了一种"长段差异化极限布缝+多级双暂堵"的新工艺,并建立了暂堵球暂堵参数优化模型,分析了暂堵剂运移及封堵规律,研究了缝内暂堵暂堵剂参数优化以及簇间暂堵工艺优化和暂堵有效性识别.研究结果表明:①压裂液黏度与密度、暂堵球密度与粒径及射孔孔眼直径是缝口暂堵优化的关键性参数,采用不同密度、不同粒径的暂堵球组合,多次投球并配合变参数射孔,非均匀布酸及变排量注入措施可提高暂堵球暂堵效果;②应力差、天然裂缝密度是暂堵剂暂堵时机及次数优化的关键因素,提高排量和压裂液黏度、降低暂堵剂粒径及注入浓度利于提高缝内暂堵效果;③经过川东南地区深层页岩气现场应用,采用该新工艺的试验井平均单井压裂费用可降低约 15%,取得了良好的经济效益.结论认为,基于多级双暂堵技术形成的"长段差异化极限布缝+多级双暂堵"工艺技术试验效果较好,有利于推动深层页岩气水平井压裂由"多段少簇"压裂模式转变为"少段多簇"压裂模式,对深层超深层页岩气的规模效益开发具有重要的借鉴和指导意义.
以"能源转型:通往净零之路"为主题的第 24 届世界石油大会于 2023 年 9 月 17 日—21 日在加拿大阿尔伯塔省卡尔加里市召开.该次会议主要就未来能源转型与发展进行了讨论,重点探讨了如何利用多种解决方案在保障能源安全的同时实现碳减排目标,并就油气行业能源转型达成多项共识:①油气公司清洁能源转型已是大势所趋,"先立后破"的推进方式得到广泛认同;②当前油气公司仍需增加油气产量和供应量,但前提是率先减少碳排放量;③油气公司能否顺利实现能源转型,取决于对技术的掌控度与经济可行性;④天然气作为清洁化石能源,在能源转型过程中扮演着重要保障和忠实伴侣的角色;⑤碳捕获与封存(CCS)和碳捕获、利用与封存(CCUS)等脱碳技术将升级为投资杠杆,进一步释放技术和政策潜力;⑥氢能成为该次大会的"宠儿",蓝氢与CCS结合将成为碳捕集市场的推手;⑦受俄乌冲突对能源供需的影响,部分国家正设法加强保护自身的能源供应安全.基于参加该次大会的收获与体会,对中国油气工业发展提出建议:①结合我国能源发展的具体国情,加大国内油气稳产上产力度仍是近期能源发展的主旋律;②加大油气战略储备能力建设,主动应对极端环境挑战并保障油气稳定供给;③加强新能源、电气化的应用,因地制宜地实现油气生产过程中的能耗低碳化;④充分发挥油气工业发展的整体优势,积极布局并推动CCS和CCUS产业发展;⑤积极参与世界石油大会等国际交流,彰显中国智慧和负责任大国形象.结论认为,实现二氧化碳净零排放已成为全人类共同的责任,油气行业在推进能源转型的道路上应率先垂范.
页岩气是目前天然气勘探开发的重点和热点,但页岩气在开发过程中经常会遇到套管变形问题,套管变形不仅影响单井产量,还将缩短井筒生命周期,严重制约着我国页岩气的规模效益开发.为此,利用橡胶吸收裂缝/断层的滑动位移原理,创新设计了一种橡胶组合套管;在综合套管变形量、橡胶膨胀率、下套管摩阻、水泥浆通道和吸水膨胀效率等因素基础上,优选了橡胶胶种,设计橡胶筒成槽孔结构;并利用物理模拟试验系统对橡胶组合套管进行了抗剪切试验,最后利用ABAQUS有限元软件建立了橡胶组合套管位移加载三维力学模型,评价了橡胶组合套管的抗剪切能力.研究结果表明:①膨胀橡胶通过变形和破碎吸收了地层位移载荷,保护了套管,吸收地层滑动量可达到 37.2～40.0 mm;②当橡胶筒厚度增加时,套管的变形量随之减小,当橡胶筒厚度达到 21.7 mm时,橡胶可以完全吸收施加的位移,避免套管发生变形.结论认为,橡胶组合套管可以有效吸收裂缝/断层的滑动位移,从而保护了内层套管不受影响,进而提高了页岩气井的压裂施工效率,缩短了投产周期,可为我国页岩气的效益开发提供重要的技术支撑.
四川盆地川西地区前陆坳陷上三叠统须家河组发育多种油气资源类型,由于受多期构造裂缝与岩性复合控制和改造,该区油气藏富集规律复杂多样.为此,基于全油气系统新概念,诠释了它们的基本油气地质条件、常规—非常规油气共生特征与形成分布.研究结果表明:①川西上三叠统须家河组全油气系统具有多层系垂向叠置,以裂缝与低孔渗储层构成的立体成藏系统,是原生气藏和次生气藏共存、常规和非常规共存的陆相天然气富集区;②由北向南,上三叠统须家河组—侏罗系气藏压力系数降低、产层层系具有向浅层(向上)变迁的趋势,且甲烷含量和甲烷碳同位素特征具有增加趋势;③垂向上,须家河组至侏罗系气藏具甲烷含量和天然气干燥系数逐渐增大、非烃组分(CO2 和N2)含量减小趋势,且山前带—前陆坳陷—斜坡带气藏垂向发育层系也具有明显的不同性,体现出山前带更加易于多套成藏组合垂向常规—非常规气藏叠置.结论认为,川西前陆坳陷—前陆斜坡为上三叠统须家河组全油气系统常规和非常规气藏富集共存区,邛崃—新津隆起带为常规油气—非常规油气垂向多层系富集带,其规律性认识对于川西前陆坳陷的不同类型油气资源分布预测和勘探具有重要指导意义.
如何准确评价沉积有机质特征是油气资源勘探开发工作的关键问题之一,勘探开发实践证实高—过成熟有机质特征评价尤其困难.为此,以松辽盆地下白垩统沙河子组、四川盆地下志留统龙马溪组和下寒武统筇竹寺组烃源岩为研究对象,运用激光拉曼和傅里叶变换质谱等方法对烃源岩样品进行了有机质特征评价,开展了超高分辨率的傅里叶变换离子回旋共振质谱(FT-ICR MS)实验,并从分子角度讨论了有机质热演化特征,计算了烃源岩样品的成熟度评价指标(MAT),表征了有机质分子化合物相对含量动态变化规律,实现了可连续量化的有机质成熟度评价.研究结果表明:①松辽盆地沙河子组、四川盆地龙马溪组和筇竹寺组烃源岩的有机质具有良好的生油气潜力,镜质体反射率(Ro)大于 1.30%,有机质的热演化程度为高—过成熟;②松辽盆地沙河子组烃源岩有机质化合物以碳氢类型为主,四川盆地龙马溪组和筇竹寺组以硫化合物和氧化合物为主,碳氢化合物、N1、O1、S1 化合物的单同位素离子总丰度呈现出随成熟度的增加而降低的趋势;③在Ro = 0～2.50%、岩石热解高峰温度(Tmax)介于 420～600℃时,烃源岩的MAT与成熟度正相关,而当Ro＞2.50%、Tmax＞600℃时,MAT出现逐渐下降的现象,该现象可能与有机质分子化合物的热稳定性和沥青、石墨的生成有关;④激光拉曼光谱实验结果证实了基于FT-ICR MS的成熟度指标化合物中芳香环增加的现象.结论认为,激光拉曼和傅里叶变换质谱从不同角度揭示了热演化过程中有机质的结构变化,为高—过成熟烃源岩的有机质特征评价提供了启示.
推进柴达木盆地东部(以下简称柴东地区)上石炭统油气勘探进程亟待明确其烃类地球化学特征、赋存状态及其生成过程.为此,通过天然气组分与碳同位素测试,探讨了柴东地区欧南凹陷 2 口关键井上石炭统天然气的成因与来源,在此基础上厘清了上石炭统海陆过渡相烃源岩生烃过程及烃类赋存状态.研究结果表明:①上石炭统天然气中烃类气平均含量为 94.51%,非烃气平均含量为 5.49%,干燥系数介于 0.28～1.00,干气为主,湿气仅发育于上石炭统浅层,深层天然气干燥系数较高;②浅层气甲烷碳同位素明显偏轻,乙烷碳同位素和二氧化碳碳同位素分布范围大,低碳烷烃以腐泥型干酪根初次热解为主,早期产出的液态烃经微生物降解形成生物甲烷,高碳烷烃与原油裂解作用密切相关,腐殖型干酪根初步热解的煤成气多以吸附态形式赋存;③深层低碳烷烃为裂解反应较充分的原油裂解气混入部分煤型游离气,高碳烷烃可能与腐泥型干酪根二次活化裂解有关;④天然气中二氧化碳不仅存在干酪根热降解有机成因类型,也发育碳酸盐矿物化学反应释放的无机成因类型.结论认为,上石炭统烃源岩混合了海洋、陆地两种环境来源的生物有机质,海相腐泥型有机质因热化学活化能低而优先进入生烃门限生成液态烃及伴生油型湿气,原油裂解和陆相腐殖型干酪根生气在高成熟阶段逐步启动,在过成熟阶段 2 种生气机制的作用愈发突显,残余腐泥型干酪根也因高温条件发生二次活化裂解并生成少量高碳烷烃.
济阳坳陷页岩油气藏具有埋藏深、构造复杂、沉积相变化快、纹层发育、原油黏度高等复杂特征,采用常规缝网压裂技术时改造效果普遍不理想、压后产量低且衰减快,亟待攻关能形成与之相适应的长期高导流能力复杂缝网的压裂新技术.为此,基于地质工程一体化思路,开展了地质—工程双甜点评价、四级组合缝网构建、主裂缝脉冲加砂理论与技术研究,形成了组合缝网高导流压裂关键技术,并实现了规模应用.研究结果表明:①充分考虑页岩油气富集、可动性、页岩纹层发育情况等特征,建立了考虑"岩屑—岩心—井眼—储层"的"地质—工程"双甜点评价模型,井位布置、压裂层位及射孔位置优选更加精准;②构建了CO2 与酸液联合降低破裂压力,低黏度压裂液造复杂缝、高黏度压裂液促缝高的组合压裂液新模式,增加了压裂后缝网的复杂性;③形成了多层叠置储层压裂后的"大缝宽主裂缝+分支裂缝+自支撑裂缝+酸蚀蚓孔缝"四级组合缝网体系,提出了主裂缝脉冲加砂、分支裂缝连续加砂的高导流缝网加砂压裂新方法,提升了缝网的长期导流能力.结论认为,"双甜点布缝+CO2 与酸液降破促缝+压裂液变黏高黏+主裂缝脉冲加砂"的组合缝网高导流压裂关键技术,促进了济阳坳陷陆相页岩油气藏的高黏度原油经济高效开发,为类似地区页岩油气藏的改造提供了理论与技术参考.
