In-situ thermal upgrading significantly alters pore structure in low-maturity oil shales, yet the key mechanisms controlling this transformation remain to be defined. Deciphering pore geometry and seepage capacity is crucial, as they directly dictate the flow network connectivity and ultimate hydrocarbon recovery; however, systematic quantification of their dynamic anisotropic variations is currently lacking. We establish two novel two-dimensional coordinate mapping classification schemes based on geometric parameters extracted via machine learning. These represent a seepage capacity classification based on pore cross-sectional area (S) and perimeter (C), and a morphological classification based on circularity (Circ.) and aspect ratio (AR). Observations reveal a pronounced anisotropy in pore evolution. Bedding-normal (nominally vertical), both seepage capacity and morphological complexity follow non-monotonic trajectories driven by stress. Bedding-parallel (nominally horizontal), however, permeability decreases with the increasing number and proportion of low seepage capacity pores (L-SC), and the quantity of each morphological pore type increase continuously, although morphological complexity is diluted by newly formed simple pores. Fractal dimension (D) and Pearson correlation analysis further corroborate this anisotropy: throughout the heating process, D values in bedding-parallel direction (DH) remains consistently higher than in bedding-normal direction (DV). D values monotonically increase in the bedding-normal direction, showing a significant positive correlation with regular elongated pores; whereas bedding-parallel, D values fluctuate, exhibiting the strongest correlation with transitional pores. These newly established classification frameworks provide quantitative tools for characterizing the anisotropic evolution of pore architecture and offer theoretical support for efficient in-situ conversion of low-maturity oil shale.

Geothermal resources have important value for its development and utilization. In this work, a thermal-hydraulic-mechanical (THM) coupled numerical model is developed to simulate the heat extraction process in an enhanced geothermal system (EGS). In particular, the matrix permeability enhancement is related to thermal unloading, and the fracture conductivity is determined by the normal effective stress state. Then, a theoretical solution and a field measurement are selected to validate the accuracy/practicality of the THM coupled model. Afterwards, two simulation cases are designed to discuss the effect of natural fractures on the heat extraction performance. Firstly, the EGS contains only one natural fracture. The heat exchange and the temperature distribution in the natural fracture and rock matrix are greatly affected by the location of the natural fracture. Secondly, the EGS contains multiple natural fractures. The results indicate that more natural fractures improve the performance of heat exchange in middle natural fracture and generate a larger cooling area in the rock matrix. With an increase in the fracture number in the EGS, the influence of the included angle between the hydraulic fracture and natural fracture on the production temperature becomes more significant, and the heat extraction efficiency is greatly improved.

With the theoretical and technological developments related to cratonic strike-slip faults, the Shuntuoguole Low Uplift in the Tarim Basin has attracted considerable attention recently. Affected by multi-stage tectonic movements, the strike-slip faults have controlled the distribution of hydrocarbon resources owing to the special fault characteristics and fault-related structures. In contrast, the kinematics and formation mechanism of strike-slip faults in buried sedimentary basins are difficult to investigate, limiting the discussion of these faults and hydrocarbon accumulation. In this study, we identified the characteristics of massive sigmoidal tension gashes (STGs) that formed in the Shunnan area of the Tarim Basin. High-resolution three-dimensional seismic data and attribute analyses were used to investigate their geometric and kinematic characteristics. Then, the stress state of each point of the STGs was calculated using seismic curvature attributes. Finally, the formation mechanism of the STGs and their roles in controlling hydrocarbon migration and accumulation were discussed. The results suggest that: (1) the STGs developed in the Shunnan area have a wide distribution, with a tensile fault arranged in an en échelon pattern, showing an S-shaped bending. These STGs formed in multiple stages, and differential rotation occurred along the direction of strike-slip stress during formation. (2) Near the principal displacement zone of the strike-slip faults, the stress value of the STGs was higher, gradually decreasing at both ends. The shallow layer deformation was greater than the deep layer deformation. (3) STGs are critical for connecting source rocks, migrating oil and gas, sealing horizontally, and developing efficient reservoirs. This study not only provides seismic evidence for the formation and evolution of super large STGs, but also provides certain guidance for oil and gas exploration in this area.

Global climate change is a crucial issue confronting the international community [...]

As the burial depth of shale exploitation increases, it is challenge to form fracture networks through hydraulic fracturing technology. When cryogenic fluid contacts with hot rock, heat exchange process occurs and temperature gradient is generated at the rock surface, resulting in thermal stress. Once the thermal stress exceeds the tensile strength, the fractures are generated. To study the initiation and propagation of fractures induced by thermal shock, a thermal-mechanical (TM) coupled two-dimensional model is developed in the paper. To simulate the heat exchange process, the heat convective boundary is applied in the surface between the fluid and the rock. In addition, the initiation and propagation of fractures are described by the cohesive zone model. The accuracy and reliability of the numerical model is validated by an existing analytical solution. Under the thermal shock, the temperature at the contact surface drops quickly. The stress distribution is determined by the temperature variation. The variations of temperature and stress are greatly affected by the heat exchange coefficient. With the fractures embedded in the model, the initiation and propagation of fractures are analysed. The multi-fracture propagation induced by thermal shock exhibits competition effect. With the propagation of fractures, the stress distribution in the rock changes. The heat exchange coefficient has a significant effect on fracture initiation and propagation, presenting more fractures generation in the larger coefficient.

Herein, a brush-like Cu2O-CoO core-shell nanoarray on copper foam (Cu2O-CoO/CF) can achieve efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance in alkaline seawater electrolyte. This Cu2O-CoO/CF shows overpotentials as low as 315 and 295 mV at 100 mA cm-2 for the OER and HER, respectively. Moreover, it could also be operated at 1.82 V with 100 mA cm-2 in a two-electrode electrolyzer and exhibits strong stability for at least 50 hours of electrolysis. The excellent performance and hierarchical structure advantages of Cu2O-CoO/CF provide new ideas for designing efficient seawater splitting electrocatalysts.

The nitrate reduction reaction is emerging as having tremendous potential to mitigate nitrate pollution and simultaneously produce valuable ammonia. Here, we propose Co3O4 nanoparticles embedded in porous carbon nanofibers (Co3O4@CNF) as a high-efficiency catalyst to convert nitrate to ammonia, and it achieves a high faradaic efficiency of 92.7% and an extremely large NH3 yield of 23.4 mg h-1 mg-1cat, and also presents excellent electrochemical stability. Theoretical calculations reveal that the potential determining step (PDS) reaches as low as 0.28 eV. This work is expected to open a new avenue to rationally design robust noble-metal-free catalysts for the electrochemical synthesis of ammonia.

The Shunbei No. 5 strike-slip fault and its associated fractures in Tarim Basin control the formation of reservoirs and impact the migration and accumulation of oil and gas. Selecting appropriate seismic attributes to characterize and describe the spatial distribution of fractured reservoirs plays an important role in fractured reservoir prediction. Due to the seismic resolution of faults and fractures at different scales, it is necessary to use different methods and their combinations to identify fractures at different scales. To further characterize the fractures that associated with strike-slip faults in the Shunbei area in Tarim Basin, this paper compares the capability characterizing faults and fractures of individual seismic attributes and their combined attributes.The seismic attribute comparison shows that the high-precision coherent volume that constrained by dip angle and plane feature attribute can characterize the large-scale faults with fault distances over 40 m.The multi-coherent merge and strain-energy attributes can represent mesoscale fractures with a fault distance of 40-15 m. In addition, fracture-gave gain and thin likelihood enhancer can characterize small-scale fractures with a fault distance less than 15 m.The results of correlation fitting of typical seismic attributes to actual fracture data and fracture density curves that interpreted from EMI imaging logging were ranked.Finally, four seismic attributes including chaos, planes, third component of structural tensor, and frequency division coherence fusion are optimized for fracture density calculation.The calculated results show that the potential reservoirs that associated with the high-density fracture zone is mainly located within 1.5 km of the transpression section of the fault in the upper section of the lower to middle Ordovician Yingshan Formation.

顺北地区发育断控储集体,埋深大,储集空间复杂,储集体展布主要受深大型走滑断裂控制,准确刻画断控储集体空间位置、储集体体积和储集体连通性,已成为断溶体油气藏勘探开发的主要难点.依据顺北地区走滑断裂的地质发育模式、断控储集体类型及地震响应特征,通过模型正演及井震结合分析,建立了走滑断裂带及断控储集体地震识别模式,开展储集体敏感地震属性分析,形成了针对断控储集体外部轮廓、内部不同类型储集体的一系列储集体预测技术.在此基础上,应用结构张量属性、增强相干属性、瞬时能量属性、杂乱属性以及相控波阻抗反演技术,对断控储集体边界及内部储集体进行表征,最终形成了顺北地区超深断控储集体地震识别技术.

在详细刻画与定量分析顺北地区走滑断裂几何学特征的基础上,解剖了走滑断裂典型构造样式,建立了主干断裂演化模式,并结合生产动态资料探讨了走滑断裂差异演化对规模储集体发育部位、油气沿断裂带差异分布的控制作用:(1)顺北地区普遍具有"纵向分层变形、主滑移带平面分段"的空间结构特征,纵向分层变形分界面多为岩性界面,平面分段主要发育于中下奥陶统碳酸盐岩(勘探目的层).平面分段中叠接变形段长宽比相似,均值为3.2.(2)顺北地区走滑断裂在目的层同时发育有"压脊?地堑"复合构造样式,上覆地堑构造是下伏压脊构造在后期活动时拖曳上覆地层形成的伴生构造.(3)顺北地区走滑断裂演化受控于盆地南、北不同区域应力场的叠加作用,演化早期最大主应力方向从南到北发生了NNE向到NNW向的逆时针偏转,为顺北5断裂弧形构造行迹的发育奠定了基础.(4)压脊构造与压隆段边界断面类似,根部沟通烃源,具有"控储、控藏"特征.地堑构造自上而下发育至目的层,不直接沟通烃源,暂未钻遇规模性储集体.研究区走滑断裂晚期活动强度可控制晚期高成熟油气充注程度.

塔里木盆地顺北地区发育一系列中小尺度的板内走滑断裂,断裂带油气富集,但断裂空间结构、断裂演化及其对断控缝洞型储层的控制机理尚不明确.以富含油气的顺北1号断裂与顺北5号断裂为研究对象,对走滑断裂垂向构造样式、平面分段样式、空间结构开展系统研究,并结合生产动态资料深入探讨了走滑断裂构造变形对油气富集的控制作用.基于重要构造变革期及岩性特征将顺北地区古生界地层划分为6个构造层,提出走滑断裂在不同构造层具有"分层变形、分段演化"的构造变形特征.顺北1号断裂垂向构造序列相对简单,深层线性走滑断裂平面分段数少,断裂纵向空间结构组合较简单;顺北5号断裂垂向构造序列复杂,发育一套膏盐岩滑脱构造."分层变形、分段演化"的构造变形导致断层空间结构复杂,同时走滑断裂在不同构造层中的构造样式对断控缝洞型油气藏成藏要素具有重要控制作用.走滑断裂在平面分段、纵向构造、活动强度和空间结构等方面的差异是导致顺北1号断裂和顺北5号断裂油气差异富集的根本原因.

海相碳酸盐岩储层是南黄海盆地崂山隆起中—古生界重要的油气储层,由于钻井少,储层非均质性强,地震储层预测研究是油气勘探的重点和难点.以南黄海石炭系—下二叠统碳酸盐岩为例,通过分析CSDP-2井生物碎屑灰岩储层的岩石物性及井-震响应特征,发现生物碎屑灰岩声波阻抗高于纯灰岩以及碎屑岩的声波阻抗,低λρ具有较好的岩石物性特征,针对这种特点,采用叠前同时反演方法对孔隙型碳酸盐岩储层的岩性和物性进行预测.预测结果表明南黄海崂山隆起石炭系—下二叠统生物碎屑灰岩储层比较发育,横向不连续且具有较强的非均质性,位于古高地储层物性发育较好,其成因是由于受印支构造运动,上覆地层抬升到地表遭到暴露,加上淡水淋滤溶蚀作用,在一定程度上提高了碳酸盐岩储层的次生孔隙,形成了钻井岩心所揭示的储层特征,因此,高孔隙度的孔隙型碳酸盐岩是南黄海石炭系—下二叠统油气勘探的首选目标.

顺北地区奥陶系目的层主要发育洞穴型、裂缝型和孔洞型3种类型储层,储层非均质性强,且储集规模受多期活动走滑断裂体系控制。已钻井揭示的断溶体储层地震响应特征多样,预测与描述难度大。断溶体圈闭是一种与喀斯特岩溶缝洞型圈闭有较大差异,在复杂条件下形成的特殊碳酸盐岩缝洞型圈闭,具有纵向跨越深度大、横向非均质性强、不受局部构造形态控制、无统一油水界面、上覆区域泥岩顶封、致密碳酸盐岩可侧封的特点。在前期研究认识基础上,通过模型正演,结合井震标定及地震反射特征分析,建立了走滑断裂、断控缝洞储集体地震识别模式,形成了梯度结构张量定断溶体轮廓,振幅变化率、杂乱相属性等分类预测断裂带内部储层,多属性融合雕刻描述断溶体的储层识别描述技术;建立了断溶体识别与圈闭描述技术。该技术的应用指导了顺北地区多口井部署并实现油气重大突破,储层钻遇率达84%,证实了技术的有效性及适用性,为顺北油气田和其他地区识别及描述断溶体提供了解决方法和技术参考,对顺北油田超深层领域断溶体勘探开发具有重要意义。

苏里格气田下古生界马家沟组储层目前已成为该气田稳产的有力支撑,分析其储层特征及控制因素对维持气田稳产具有重大意义.利用岩心观察、薄片鉴定、阴极发光等资料,系统分析了马家沟组主力储层特征.研究表明:马家沟组储层以颗粒白云岩、晶粒白云岩和微生物岩为主,储集空间主要为晶间孔、晶间溶孔、膏模孔、小型溶蚀孔洞及粒间孔等;储层展布主要受控于岩溶作用及古地貌分布,加里东期表生岩溶作用对储层改善贡献不大,甚至是一种破坏作用;岩溶古地貌高部位主要受表生岩溶作用的影响,对储层的储集空间和连通性有一定的改造作用,使储层物性较好,单井产气量高,而岩溶古地貌低部位主要受准同生期岩溶作用的影响,物性相对较差,单井产气量低.该研究成果可为苏里格气田下古生界气藏的有利区预测提供地质依据.

塔里木盆地顺北地区碳酸盐岩发育断溶体储层.断溶体纵向深度大、内部非均质性极强,其展布主要受深大走滑断裂带控制.断溶体的储集空间主要为洞穴、孔洞和裂缝.断溶体储层在不同级别断裂带、同一断裂带不同分段内的发育程度有明显差异.如何准确刻画断溶体的空间位置、体积和连通性已成为断溶体油藏勘探开发的主要难点.基于正演模拟和井震结合的储层地震反射特征所分析的断溶体储层地震识别模式,结合结构梯度张量分析、增强相干处理的自动断层提取技术、相控波阻抗反演技术可对断溶体储层的边界及内部特征进行描述,并对断溶体储层进行空间雕刻及储量计算.利用单井产量、动态储量可对结果进行验证.

南海北部陆坡神狐海域天然气水合物钻探结果显示,这一区域水合物储层具有纵横向分布不均质性、规模小且变化快的特点,使得精确评价水合物资源量面临诸多困难.根据井震数据分析了水合物分布特点,利用分频反演方法对该区水合物的空间分布进行预测.分频反演是利用测井和地震资料,采用支持向量机(SVM)的方法研究不同探测频率下的振幅响应(AVF),将AVF作为独立信息引入反演,建立起测井和地震波形间的非线性关系,充分利用地震中全频带信息,实现高分辨率的反演结果.采用该方法进行预测的结果与实际钻井情况非常吻合,验证这一技术适用于预测非均质性天然气水合物空间分布.基于预测结果并结合区域地质特征综合分析表明:水合物分布不均匀的主控因素除温压条件外,晚中新世之后的频繁构造运动使较深部的热解气沿着断层、气烟囱向上运移,形成厚块状"流体运移通道型"天然气水合物藏,而浅部沉积物中以扩散方式在渗透性良好的储层形成薄层状天然气水合物藏.

塔里木盆地顺北地区地表沙丘起伏大,地震信号吸收衰减严重,断溶体储集体埋藏深度大,纵横向非均质性强,因而断溶体(断裂、缝洞)成像精度不高、储层预测与圈闭描述难度大.为此,在该区系统开展了三维地震采集、目标处理、综合解释一体化技术攻关.首先,基于断溶体目标优化采集方案设计,采用中小面元、长排列、宽方位、高覆盖的观测系统,尽可能保护断裂绕射、缝洞体低频信息,提高采集数据质量;其次,在保幅、保真的前提下,建立了以"三层一带"精细速度建模为核心的断溶体成像技术,提高缝洞及不同尺度走滑断裂带的成像精度;再次,依据断溶体储层类型及反射结构特征,建立了走滑断裂带及断溶体储层地震识别模式,开展储层敏感属性分析,形成针对断溶体外部轮廓、内部不同类型储层的一系列储层预测及流体检测技术;最终,建立了"张量属性定轮廓、振幅属性定边界、融合雕刻定体积"的圈闭落实与描述技术,形成了"打主断、过异常、穿核部"目标优选与井轨迹优化设计技术.探区多口钻井实现了油气重大突破,证实了顺北沙漠区超深断溶体油气藏三维地震勘探技术的有效性及适用性.

Coalbed methane (CBM) is an important unconventional gas resource, and pore structure characterization is important for CBM reservoir evaluation. Existing methods for studying the petrophysical properties of coal have limitations on the data quality or require sample destruction. In this chapter, we present the experimental results of low-field nuclear magnetic resonance (NMR) relaxation of 12 coal samples under different water-saturated conditions. Results show that NMR characterization of porosity, pore size distribution, pore geometry, pore connectivity, and permeability of coal is reliable and better than other conventional methods. More importantly, the NMR method does not require the destruction of the coal samples and is not time-consuming. It is concluded that the NMR method should be applied for CBM reservoir analysis in the laboratory and CBM well loggings in the coalfield.

As coalbed methane (CBM) reservoirs have extremely low permeability, hydraulic fracturing is a common stimulation process for enhancing the CBM production. An in-depth understanding about the propagation mechanism of hydraulic fractures in coal is important for designing a hydraulic fracturing process and thus for improving the CBM production. This study performed a set of true tri-axial fracturing experiments on six block samples (300 mm × 300 mm × 300 mm, including raw coal and artificial roof/floor) with consideration of in situ conditions, aiming at simulating the propagation of hydraulic fractures in the CBM reservoir in the Changzhi field, southern Qinshui basin. Four groups of experiments were organized to evaluate the influences from the pre-existing natural fracture, in situ stresses and injection flow rates on the hydraulic fracture propagation. Meanwhile, five series of numerical simulations were constructed to model the relationship between in situ horizontal stresses and hydraulic fracture propagation. The results show that the hydraulic fracture propagates only along the pre-existing natural fracture direction under a small approaching angle, while it propagates along both the directions of the pre-existing natural fracture and the maximum horizontal principal stress (σH) under a large approaching angle. Whether pre-existing natural fractures exist or not can result in a distinct influence on hydraulic fracture propagation. Hydraulic fractures straightly propagate along the σH direction under a high value of horizontal stresses difference coefficient (Kh), while they tend to deviate from the σH direction under a low Kh value. The influence of Kh is greater than that of the horizontal stresses difference (Δσ) in determining fracture propagation to extend along the σH direction in the coal seam. Large approaching angle, high in situ stresses and a high injection flow rate are three major factors to cause the roof/floor broken by hydraulic fluids.