Formation,evolution,reconstruction of black shales and their influence on shale oil and gas resource

Black shales are important products of material cycling and energy exchange among the lithosphere,atmosphere,hydrosphere,and biosphere.They are widely distributed throughout geological history and provide essential energy and mineral resources for the development of human society.They also record the evolution process of the earth and improve the understanding of the earth.This review focuses on the diagenesis and formation mechanisms of black shales sedimentation,composition,evolution,and reconstruction,which have had a significant impact on the formation and enrichment of shale oil and gas.In terms of sedimentary environment,black shales can be classified into three types:Marine,terrestrial,and marine-terrestrial transitional facies.The formation processes include mechanisms such as eolian input,hypopycnal flow,gravity-driven and offshore bottom currents.From a geological perspective,the formation of black shales is often closely related to global or regional major geological events.The enrichment of organic matter is generally the result of the interaction and coupling of several factors such as primary productivity,water redox condition,and sedimentation rate.In terms of evolution,black shales have undergone diagenetic evolution of inorganic minerals,thermal evolution of organic matter and hydrocarbon generation,interactions between organic matter and inorganic minerals,and pore evolution.In terms of reconstruction,the effects of fold deformation,uplift and erosion,and fracturing have changed the stress state of black shale reservoirs,thereby having a significant impact on the pore structure.Fluid activity promotes the formation of veins,and have changed the material composition,stress structure,and reservoir properties of black shales.Regarding resource effects,the deposition of black shales is fundamental for shale oil and gas resources,the evolution of black shales promotes the shale oil and gas formation and storage,and the reconstruction of black shales would have caused the heterogeneous distribution of oil and gas in shales.Exploring the formation mechanisms and interactions of black shales at different scales is a key to in-depth research on shale formation and evolution,as well as the key to revealing the mechanism controlling shale oil and gas accumulation.The present records can reveal how these processes worked in geological history,and improve our understanding of the coupling mechanisms among regional geological events,black shales evolution,and shale oil and gas formation and enrichment.

Analysis of the world oil and gas exploration situation in 2021

The global exploration investment, new oil and gas discoveries, exploration business adjustment strategies of oil companies in 2021, and future favorable exploration domains are systematically analyzed using commercial databases such as IHS and public information of oil companies. It has been found that the world oil and gas exploration situation in 2021 has continued the downturn since the outbreak of COVID-19. The investment and drilling workload decreased slightly, but the success rate of exploration wells, especially deepwater exploration wells, increased significantly, and the newly discovered reserves increased slightly compared with last year. Deep waters of the passive continental margin basins are still the leading sites for discovering conventional large and medium-sized oil and gas fields. The conventional oil and gas exploration in deep formations of onshore petroliferous basins has been keeping a good state, with tight/shale oil and gas discoveries made in Saudi Arabia, Russia, and other countries. While strengthening the exploration and development of local resources, national, international, and independent oil companies have been focusing on major overseas frontiers using their advantages, including risk exploration in deep waters and natural gas. Future favorable exploration directions in the three major frontiers, the global deep waters, deep onshore formations, and unconventional resources, have been clarified. Four suggestions are put forward for the global exploration business of Chinese oil companies: first, a farm in global deepwater frontier basins in advance through bidding at a low cost and adopt the “dual exploration model” after making large-scale discoveries;second, enter new blocks of emerging hot basins in the world through farm-in and other ways, to find large oil and gas fields quickly;third, cooperate with national oil companies of the resource host countries in the form of joint research and actively participate exploration of deep onshore formations of petroliferous basins;fourth, track tight/shale oil and gas cooperation opportunities in a few countries such as Saudi Arabia and Russia, and take advantage of mature domestic theories and technologies to farm in at an appropriate time.

Growth behavior and resource potential evaluation of gas hydrate in core fractures in Qilian Mountain permafrost area, Qinghai-Tibet Plateau

The Qilian Mountain permafrost area located in the northern of Qinghai-Tibet Plateau is a favorable place for natural gas hydrate formation and enrichment,due to its well-developed fractures and abundant gas sources.Understanding the formation and distribution of multi-component gas hydrates in fractures is crucial in accurately evaluating the hydrate reservoir resources in this area.The hydrate formation experiments were carried out using the core samples drilled from hydrate-bearing sediments in Qilian Mountain permafrost area and the multi-component gas with similar composition to natural gas hydrates in Qilian Mountain permafrost area.The formation and distribution characteristics of multi-component gas hydrates in core samples were observed in situ by X-ray Computed Tomography(X-CT)under high pressure and low temperature conditions.Results show that hydrates are mainly formed and distributed in the fractures with good connectivity.The ratios of volume of hydrates formed in fractures to the volume of fractures are about 96.8%and 60.67%in two different core samples.This indicates that the fracture surface may act as a favorable reaction site for hydrate formation in core samples.Based on the field geological data and the experimental results,it is preliminarily estimated that the inventory of methane stored in the fractured gas hydrate in Qilian Mountain permafrost area is about 8.67×1013 m3,with a resource abundance of 8.67×108 m3/km2.This study demonstrates the great resource potential of fractured gas hydrate and also provides a new way to further understand the prospect of natural gas hydrate and other oil and gas resources in Qilian Mountain permafrost area.

Technologcial progress and development directions of PetroChina overseas oil and gas exploration

Through a comprehensive review of PetroChina overseas oil and gas exploration of more than 20 years,we systematically summarize the development history,development status and application results of the overseas oil and gas exploration theory and technology.Overseas oil and gas exploration has experienced four stages,exploratory exploration,progressive exploration,risk exploration and efficient exploration.The overseas exploration theory and technology have also gone through the initially direct borrow of domestic mature technology to the integrated application,and then to the research innovation based on overseas features.A series of overseas oil and gas exploration theories and technologies represented by theories and technologies for passive rift basins,salt basins and foreland basin slopes,and global oil and gas geology and resource evaluation have been established.On the basis of deep analysis of the future overseas exploration development demand for the technology,and combined with the domestic and overseas future development trend of theory and technology,this paper systematically discusses the overseas exploration difficulties,technical requirements and the main development directions and aims of exploration theory and technology in the future:(1)Develop conventional onshore oil and gas exploration techniques continuously for the overseas exploration and keep them at an internationally advanced level.(2)Develop the global oil and gas resources and assets integrated optimization evaluation technology and its information system construction project innovatively to reach the international leading level.(3)Develop the deep water exploration technology integratively and narrow the gap with the world’s advanced level.

Research progress and challenges of natural gas hydrate resource evaluation in the South China Sea

As an efficient clean energy,natural gas hydrate(NGH)has become a hot topic in recent researches.Since1990 s,China has made great achievements and progress in NGH exploration in the South China Sea(SCS),including determination of the favorable distribution areas and favorable strata thickness,identification of the dual source for accumulation,evaluation of the prospective gas contents,verification of the widespread existence,and confirmation of the technical recoverability of NGH resources.However,there are three major challenges in the NGH studies.First,all the 24 national key and major projects in the SCS focused on trial production engineering and geological engineering in the past 20 years,while 8 of the 10 international NGH research projects focused on resource potential.Second,resource evaluation methods are outdated and some parameter selection are subjective.Third,the existing resource evaluation results are low-level with a great uncertainty,and cannot be used to guide NGH exploration and production or strategic research.To improve the evaluation of NGH resources in the SCS,future researches should focus on four aspects:(1)improve the research on the criterion of the objective existence of NGH and the method of prediction and evaluation;(2)apply new theories and methods from the global NGH research;(3)boost the research on the difference and correlation of the conditions of hydrocarbon migration and accumulation in different basins;(4)innovate the theory and method of NGH resource potential evaluation.

Deep structural research of the South China Sea: Progresses and directions

The South China Sea(SCS)is the hotspot of geological scientific research and nature resource exploration and development due to the potential for enormous hydrocarbon resource development and a complex formation and evolution process.The SCS has experienced complex geological processes including continental lithospheric breakup,seafloor spreading and oceanic crust subduction,which leads debates for decades.However,there are still no clear answers regarding to the following aspects:the crustal and Moho structure,the structure of the continent-ocean transition zone,the formation and evolution process and geodynamic mechanism,and deep processes and their coupling relationships with the petroliferous basins in the SCS.Under the guidance of the“Deep-Earth”science and technology innovation strategy of the Ministry of Natural Resources,deep structural and comprehensive geological research are carried out in the SCS.Geophysical investigations such as long array-large volume deep reflection seismic,gravity,magnetism and ocean bottom seismometer are carried out.The authors proposed that joint gravitymagnetic-seismic inversion should be used to obtain deep crustal information in the SCS and construct high resolution deep structural sections in different regions of the SCS.This paper systematically interpreted the formation and evolution of the SCS and explored the coupling relationship between deep structure and evolution of Mesozoic-Cenozoic basins in the SCS.It is of great significance for promoting the geosystem scientific research and resource exploration of the SCS.

Rotational failure analysis of spherical-cylindrical shell pressure controllers related to gas hydrate drilling investigations

In situ pressure-preserved coring(IPP-Coring)technology is considered one of the most efficient methods for assessing resources.However,seal failure caused by the rotation of pressure controllers greatly affects the success of pressure coring.In this paper,a novel spherical-cylindrical shell pressure controller was proposed.The finite element analysis model was used to analyze the stress distribution and deformation characteristics of the pressure controller at different rotation angles.The seal failure mechanism caused by the rotation of the pressure controller was discussed.The stress deviation rate was defined to quantitatively characterize the stress concentration.Based on the test equipment designed in this laboratory,the ultimate bearing strength of the pressure controller was tested.The results show that the rotation of the valve cover causes an increase in the deformation on its lower side.Furthermore,the specific sealing pressure in the weak zone is greatly reduced by a statistically significant amount,resulting in seal failure.When the valve cover rotates 5°around the major axis,the stress deviation rate is-92.6%.To prevent rotating failure of the pressure controller,it is necessary to control the rotation angle of the valve cover within 1°around the major axis.The results of this research can help engineers reduce failure-related accidents,provide countermeasures for pressure coring,and contribute to the exploration and evaluation of deep oil and gas resources.

中国油气矿业权管理改革进展、问题及政策建议

为促进油气勘探开发和增储上产,保障国家能源安全,国家有关政府部门加快油气资源管理改革步伐,着力进行油气矿业权改革,实施了力度空前的探矿权勘查面积退减政策,积极开展探矿权竞争性出让,取得了进展与成效。油气探矿权勘查面积退减和竞争性出让政策仍存在亟待改进完善的问题。探矿权勘查面积退减存在的问题有:退减力度过大,退减比例过高;实行“一刀切”,不利于鼓励勘探投入;缺乏对有关退减矿业权的补偿机制;探矿权退减监管工作较薄弱。探矿权竞争性出让存在的问题包括:竞争机制有待完善;出让方式单一;出让力度不足;出让频次低且缺乏规律性;配套服务和支撑条件不足。为进一步激发油气上游市场活力,建议加快构建适应加大油气勘探开发和增储上产力度需要的法律法规;完善油气探矿权面积退减机制,尽快出台专门管理办法;完善油气探矿权区块出让机制,尽快出台相应管理办法;加强并完善油气探矿权退减和出让的配套政策与服务。

Accumulation of unconventional petroleum resources and their coexistence characteristics in Chang7 shale formations of Ordos Basin in central China

The Ordos Basin is the largest oil and gas producing basin in China, where tight oil, shale gas, oil shale, and other unconventional oil and gas resources have been found in the Chang7 subsection of the Triassic Yanchang Formation. However, the mechanism of formation and the distribution of unconventional oil and gas resources in the shale layers have not been systematically investigated until now. According to the type of unconventional oil and gas resources, main controlling factors, and the maturity, depth and abundance of organic matters, the shale oil and gas resources from Chang7 region are divided into five zones that include an outcrop-shallow oil shale zone, a middle-matured and medium-burial shale oil zone, a medium-matured and medium-burial in situ conversion process (ICP) shale oil zone, a high-maturity and deep-burial shale gas zone, and an adjacent-interbedded tight sandstone oil zone. By the distribution of resources, orderly evolution of oil and gas resources and coexistences in lacustrine shale formations have been put forward, and also a strategy of integrated exploration and development of resources in the shale formations is proposed. Overall, the outcome of this study may guide on the effective utilization of unconventional oil and gas resources in other shale formations.

我国深层—超深层油气资源探矿权管理存在的问题及政策建议

随着我国浅层—中浅层油气资源的探明程度逐年升高,勘探增储潜力逐年递减,加大深层—超深层油气勘探对于缓解年度新增油气探明储量的压力、保障国家能源安全具有重要战略意义。为保障资源充分利用、促进深层—超深层油气资源发现、有效统筹资源,从而保障国家能源安全,对深层—超深层矿权管理提出了优化建议。深层—超深层矿权管理过程中存在探采合一期限过短不足以完成转采、新出让深层—超深层探矿权范围较小不利于油气勘查、探矿权相互穿插导致科研资金重复投入等问题。通过系统梳理深层—超深层油气勘探开发现状及资源潜力,深入分析深层—超深层矿权管理中存在的问题并提出针对性解决方案。建议探采合一期满再延续一次至8~10年,保障油田企业有足够的转采时间;合理设置出让矿权规模及延续退减方式,鼓励矿业权人在新区块内加强投入,促进油气资源发现;加强组建专项联合研究团队,贯通深层—超深层油气勘探开发装备材料器件、制造、应用产业链条,优化资源投入,提升中国战略资源整体效率。加强资源统筹、优化矿权管理政策,为我国深层—超深层油气勘探开发高质量可持续发展提供有力保障。

我国油气探采合一制度改革与实践

为促进油气探矿权和采矿权的有序衔接,针对多年存在的问题,自然资源部于2019年12月印发《自然资源部关于推进矿产资源管理改革若干事项的意见(试行)》,首次提出了油气探采合一的理念。油气探采合一制度结合油气资源勘探开发特点,能够初步解决油气资源勘查阶段获取油气的合法性问题,符合油气勘探开发规律,有助于激发活力,促进上游油气勘探开发,但仍有诸多问题待明确。在梳理报告可供开采区块数据信息基础上,结合调查研究,总结油气探采合一制度执行情况,分析认为油气探采合一制度在执行层面上存在管理需要进一步规范、与当前制度不衔接和监管责任未落实等问题。针对存在的问题,建议从发现可供开采资源的报告期、报告可供开采的油气资源回执两方面规范油气探采合一制度,从矿业权审批、两证管理方面做好探采合一制度与相关行政许可制度的衔接,进一步完善探采合一的监管制度并加快修改法律法规条款,并结合当前油气行业发展形势,提出了油气探采合一“一证式”管理设想。

关于加强我国油气资源勘查开发管理的若干思考

油气资源管理体制是油气产业发展的前提和保障。但我国油气资源管理体制中仍然存在不少问题,如国家油气资源管理部门在协调、管理国有大型石油公司时难以发挥应有的功能,政府与企业对油气资源勘查开发管理的功能定位不清晰,市场参与者错位,管理部门众多,缺乏一个统一管理的能源综合管理部门进行协调和组织;资源税费改革有待进一步深化;油气资源勘查开发的监管机制不健全;缺乏完整的油气行业管理法律框架基础;市场化机制弱化;国家油气资源发展战略、政策和法规等缺乏整体协调性等。为了构建全新的油气资源管理体制,应转变政府管理方式,建立科学、高效的油气资源勘查开发管理模式;建立完善的油气矿业权管理制度,推进油气资源税费改革;加强油气资源监管,保障油气资源勘查开发的科学、合理和高效;构建法律保障体系;建立健全油气资源勘查开发的市场化运行机制;同时借鉴国外先进经验,建立高级别的油气资源集中管理模式。

SDMKD在油气资源勘探中的应用

从空间数据挖掘与知识发现(SDMKD)的内涵入手,对比分析了SDMKD与传统数据挖掘的异同,在归纳SD-MKD的任务与方法、实现过程和研究现状的基础上,对油气资源勘探SDMKD应用现状、面临的主要问题进行了总结和分析。最后,文章给出了油气资源勘探SDMKD的概念模型。

油气资源勘探开发投资市场化研究

油气资源关系国家能源安全,为缓解油气供需矛盾,国家出台了系列政策措施,开展了多次改革试点,积极推动油气资源勘探开发投资市场化改革,在市场准入、矿业权管理体制、激励措施等方面不断释放政策红利。目前油气资源探采市场化改革还存在市场化机制不健全、常规油气市场化程度低、非常规油气资源市场化运行情况欠佳等问题。为发挥市场在油气资源配置中重要作用,提高油气资源勘查开采效率,保障国家油气资源安全,建议:(1)完善市场化制度的顶层设计;(2)激发国有石油公司在常规油气市场的活力;(3)积极推动非常规油气资源市场化进程。