Distribution characteristics, exploration and development, geological theories research progress and exploration directions of shale gas in China

The shale gas resources in China have great potential and the geological resources of shale gas is over 100×10^(12)m^(3),which includes about 20×10^(12)m^(3) of recoverable resources.Organic-rich shales can be divided into three types according to their sedimentary environments,namely marine,marine-continental transitional,and continental shales,which are distributed in 13 stratigraphic systems from the Mesoproterozoic to the Cenozoic.The Sichuan Basin and its surrounding areas have the highest geological resources of shale gas,and the commercial development of shale gas has been achieved in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in these areas,with a shale gas production of up to 20×10^(9)m^(3) in 2020.China has seen rapid shale gas exploration and development over the last five years,successively achieving breakthroughs and important findings in many areas and strata.The details are as follows.(1)Large-scale development of middle-shallow shale gas(burial depth:less than 3500 m)has been realized,with the productivity having rapidly increased;(2)breakthroughs have been constantly made in the development of deep shale gas(burial depth:3500-4500 m),and the ultradeep shale gas(burial depth:greater than 4500 m)is under testing;(3)breakthroughs have been made in the development of normal-pressure shale gas,and the assessment of the shale gas in complex tectonic areas is being accelerated;(4)shale gas has been frequently discovered in new areas and new strata,exhibiting a great prospect.Based on the exploration and development practice,three aspects of consensus have been gradually reached on the research progress in the geological theories of shale gas achieved in China.(1)in terms of deep-water fine-grained sediments,organic-rich shales are the base for the formation of shale gas;(2)in terms of high-quality reservoirs,the development of micro-nano organic matter-hosted pores serves as the core of shale gas accumulation;(3)in terms of preservation conditions,weak structural transformation,a moderate degree of thermal evolution,and a high pressure coefficient are the key to shale gas enrichment.As a type of important low-carbon fossil energy,shale gas will play an increasingly important role in achieving the strategic goals of peak carbon dioxide emissions and carbon neutrality.Based on the in-depth study of shale gas geological conditions and current exploration progress,three important directions for shale gas exploration in China in the next five years are put forward.

Origin,discovery,exploration and development status and prospect of global natural hydrogen under the background of“carbon neutrality”

Global energy structure is experiencing the third transition from fossil energy to non-fossil energy,to solve future energy problems,cope with climate change,and achieve net-zero emissions targets by 2050.Hydrogen is considered to be the most potential clean energy in this century under the background of carbon neutrality.At present,the industrial methods for producing hydrogen are mainly by steam-hydrocarbon(such as coal and natural gas)reforming and by electrolysis of water,while the exploration and development of natural hydrogen had just started.According to this literature review:(1)Natural hydrogen can be divided into three categories,including free hydrogen,hydrogen in inclusions and dissolved hydrogen;(2)natural hydrogen could be mainly from abiotic origins such as by deep-seated hydrogen generation,water-rock reaction or water radiolysis;(3)natural hydrogen is widely distributed and presents great potential,and the potential natural hydrogen sources excluding deep source of hydrogen is about(254±91)×10^(9) m^(3)/a according to a latest estimate;(4)at present,natural hydrogen has been mined in Mali,and the exploration and development of natural hydrogen has also been carried out in Australia,Brazil,the United States and some European countries,to find many favorable areas and test some technical methods for natural hydrogen exploration.Natural hydrogen is expected to be an important part of hydrogen energy production in the future energy pattern.Based on a thorough literature review,this study introduced the origin,classification,and global discovery of natural hydrogen,as well as summarized the current global status and discussed the possibility of natural hydrogen exploration and development,aiming to provide reference for the future natural hydrogen exploration and development.

Research on Integrated Planning Method of Offshore Oil and Gas Exploration and Development

Under the requirement of high-quality development, the research method of integrated model planning for offshore oil and gas exploration and development suitable for the western South China Sea is put forward. Based on the new round of resource evaluation and exploration and development research in the western South China Sea, the in-depth research on underground oil and gas resources, surface development facilities, external factors and economic indexes are carried out to clarify the industrial layout of oil and gas development. The potential and prospect of oil and gas exploration and development were implemented, and the main external factors and corresponding measures affecting the planning were clarified in this paper. The economic evaluation model suitable for the region is established based on the analysis of internal rate of return, comprehensive barrel oil cost, critical price, financial net present value and other important indicators, and a set of planning and research methods suitable for the integration of exploration and development in the western South China Sea is finally formed. This method has been applied to the replacement reserve study of Weizhou X and Weizhou Y oil fields. It is found that the planned reserves and production are consistent with the actual ones, and good practical results have been achieved.

Present Situation of China's Shale Gas Exploration and Development

In recent years,with China＇s continuous investment in shale gas exploration and the continuous efforts of scientific workers,China’s shale gas exploration and development has achieved leap-forward development.In2011,China＇s State Council approved shale gas as a new mineral resource.In 2014,shale gas was first proved at geological reserves of 106.8 billion m^3.

Prospect for strategic minerals exploration and development,investment environment and cooperation in Mozambique

Mozambique is an essential country in the Belt and Road Initiative,and it is also to cooperation between China and with Africa in energy resources.It is located in the critical node of the“East Africa Channel”and close to the“African Twin Ocean Railway”,which is an important strategic position.Mozambique has abundant mineral resources and vast reserves of advantageous minerals.The natural gas reserves of Mozambique ranked second in Africa.It also has world--class scale graphite and rich iron,gold,copper,niobium-tantalum and other resources.In recent years,the mining industry in this country has been rising and attracting many foreign companies to invest,including international mining giants such as Vale,Rio Tinto and large mining enterprises of China.This paper systematically studies the mineral resources endowment,exploration and development situations of natural gas,graphite,titanium-zircon placer deposits,niobium-tantalum,gold,iron and other strategic minerals in Mozambique,comprehensively analyzes the mining investment environment and the current situation of exploration and development of Chinese enterprises in Mozambique,and replans four safeguard areas of strategic mineral resources in critical short supply.Mozambique generally has good prospects of mining investment and a stable foundation for cooperation with China.Chinese enterprises can focus on oil and natural gas,graphite,titanium,zirconium,niobium,tantalum,and iron,which complement the needs of China,expand the mining capacity cooperation,and improve the ability to secure strategic mineral resources supply.

A Step to Speed up Petroleum Exploration and Development in Tarim Basin

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Construction and application of an ontology-based domain-specific knowledge graph for petroleum exploration and development

The massive amount and multi-sourced,multi-structured data in the upstream petroleum industry impose great challenge on data integration and smart application.Knowledge graph,as an emerging technology,can potentially provide a way to tackle the challenges associated with oil and gas big data.This paper proposes an engineering-based method that can improve upon traditional natural language processing to construct the domain knowledge graph based on a petroleum exploration and development ontology.The exploration and development knowledge graph is constructed by assembling Sinopec’s multi-sourced heterogeneous database,and millions of nodes.The two applications based on the constructed knowledge graph are developed and validated for effectiveness and advantages in providing better knowledge services for the oil and gas industry.

Hydrocarbon accumulation conditions and key exploration and development technologies for PL 19-3 oilfield

The PL 19e3 Oilfield is the only super-large monolithic oilfield with oil and gas reserves up to 1×10^(9) t in the Bohai Bay Basin,and it has been successfully developed.Exploration and development practices have provided abundant data for analyzing formation conditions of this super-large oilfield.On the basis of the exploration and development history,fundamental reservoir features,and with available geological,geophysical and test data,the hydrocarbon accumulation conditions and key exploration&development technologies of the PL 19e3 Oilfield were discussed.The key conditions for forming the super-large Neogene oilfield include four aspects.Firstly,the oilfield is located at the high position of the uplift that contacts the brachy-axis of the multi-ridge slope in the biggest hydrocarbon-rich sag in the Bohai Bay Basin,thus it has sufficient hydrocarbon source and extremely superior hydrocarbon migration condition.Secondly,the large-scale torsional anticlines which formed in the Neogene under the control of the Tanlu strike-slipping movement provide sufficient storage spaces for oil and gas preservation.Thirdly,the“multiple sets of composite reservoir-caprock assemblages”developing in the special shallow-water delta further contributes greatly to the effective storage space for oil and gas preservation.Fourthly,due to the coupling of the uplift and strike slip in the neotectonic period,extensive faulting activities constantly released the pressure while the late period massive hydrocarbon expulsion of the Bozhong took place at the same time,which assures the constant and intense charging of oil and gas.The super-large PL 19e3 Oilfield was controlled by the coupling effects of all those special geologic factors.In view of this oilfield's features(e.g.violently reformation caused by strike slip,and the special sedimentary environment of shallow-water delta),some key practical technologies for exploration and development have been developed.Such technologies include:the special prestack depth migration processing for gas cloud zones,the prediction of thin interbed reservoirs based on high-precision inversion of geologic model,the reservoir description for the shallow-water braided river delta,the quantitative description for remaining oil in the commingled oil reservoirs with wide well spacing and long well interval,and the well pattern adjustment for formations during high water cut period in the complex fluvial-facies oilfields.

Accumulation conditions and key technologies for exploration and development of Qinshui coalbed methane field

The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration&development of coalbed methane(CBM),it has become the largest CBM industrialization base in China and also is a model which successfully realize commercialization of CBM of high rank coal-bearing basin in the world.Although the high-rank coal field is characterized by low pressure,low permeability,low saturation and strong heterogeneity,the exploration practice and research show that the accumulation conditions of CBM reservoir in the Qinshui Basin are superior.As main productive intervals,No.15 coal seam of Taiyuan Formation and No.3 coal seam of Shanxi Formation respectively belong to the epicontinental-sea carbonate platform sedimentary system and the epicontinental-sea shallow-water delta sedimentary system.The coal seam has large thickness,and is mostly composed of humic coal and mainly contains vitrinite.Affected by tectonic thermal events in the Yanshanian period,the coal rank is high,the adsorption capacity is strong,and the gas content is large.Formation of the CBM reservoir goes through three stages including two stages of hydrocarbon generation,gas phase transformation and sealing of hydrodynamics and roof and floor.In view of the characteristics of the Qinshui Basin topography and the high rank coal,a series of key technologies for exploration and development are developed,including mountainous region seismic acquisition,processing and interpretation technology,drilling and completion technology of multiple wells,drilling and completion technology of multiple horizontal wells dominated by compound V type,deplugging secondary fracturing stimulation technology,control technology of high rank CBM drainage,and CBM gathering and transportation technology,which effectively supports the scale and industrialization development of high rank CBM in the Qinshui Basin.

Strategies of Efficient Exploration and Development of Deepwater Oil and Gas Overseas

Deepwater offshore area,with rich oil and gas resources,has currently become the hot area for oil and gas exploration and the main battlefield where global oil majors compete with each other.This article summarizes the current situation of deepwater oil and gas exploration and development overseas from the perspectives of exploration history,exploration achievements and technical progress,and analyzes the difficulties and challenges faced by the industry,such as low level understanding of hydrocarbon accumulation conditions,global security and environmental challenges.And then,several feasible implementation strategies have been proposed on how to actively deal with the challenges,promote Chinese oil companies' overseas exploration,and realize efficient exploration and development of deepwater oil and gas fields overseas.These strategies consist of three aspects:profit-oriented operation principle,exploration ideas supported by theory and technology,and exploration strategy that puts safety first.In the era of low oil prices,Chinese oil companies must build up confidence,seize the opportunity and face the challenge while taking efforts to innovate technologies and theories,updates strategic ideas,and cultivate deepwater talents so as to be in an active position in global deepwater exploration and development industry in the future.

Reservoir formation conditions and key technologies for exploration and development in Qingcheng large oilfield

The Qingcheng oilfield,the largest shale oil field in China,was discovered in 2019 in source rock of Chang 7 Member of Mesozoic Yanchang Formation,Changqing Oilfield in Ordos Basin,with newly increased proven geological reserves of 358 million tons,predicted geological reserves of 693 million tons,and a total of 1.051 billion tons of shale oil resources.This achieves a historic breakthrough in exploration of shale oil in Chang 7 Member.In recent years,focusing on key issues,such as whether there develop sweet spots in source rock,whether commercial oil production capacity can be formed,and whether scale-effective development can be achieved,studies about geological conditions for shale oil accumulation have been continuously carried out,key supporting technologies have been developed,and a series of theoretical innovations and technological breakthroughs have been achieved in oil exploration in source rocks.The results indicate that shale oil accumulation in Chang 7 Member is controlled by following factors.Firstly,lacustrine black shale,dark mudstone and other high-quality source rocks lay a material foundation for shale oil formation.Secondly,sandy deposits intercalated within black shale and dark mudstones are exploration sweet spots,and sandbody combination types are controlled by morphology of bottom of the lacustrine basin.Thirdly,reservoir properties are good due to development of micro-nano pore throats.Finally,reservoirs with high oil saturation and high gas-oil ratio are formed due to high-intensity oil charging in source rock.Effective matching of multiple factors is a key for shale oil accumulation in Chang 7 Member in Ordos Basin.Through innovation of key supporting technologies,exploration and development technologies for shale oil are developed,and substantial breakthrough on exploration and development of shale oil is realized.The first application of logging-seismic combination technology in loess plateau improves significantly quality of 3D seismic data,which effectively guides prediction of sandy sweet spots.Three-quality well logging technology is used for further evaluation of geological and engineering sweet spots of shale oil.With volumetric fracturing technology based on precise segmentation of long horizontal wells,initial daily oil production of individual well is increased from previously 10 tons to more than 18 tons.The exploration breakthrough in source rocks in Chang 7 Member in Qingcheng oilfield provides an important resource base for the second accelerated development of Changqing Oilfield.It is predicated that oil production from shale in Chang 7 Member in Qingcheng oilfield will reach three million tons in 2022 and five million tons in 2025.

Hainan to Promote the Exploration and Development of National Strategic Minerals and Prohibit the Mining of Rare Earth Metals

The Land and Resources Department of Hainan Province said on November 10 that the Overall Mineral Resources Plan of Hainan Province(2016-2020)(hereinafter referred to as the'Plan')has gone into effect with the approval of the Ministry of Land and Resources,and that the province will strongly promote the exploration and development of

Study on the Environmental Impact of Oil and Gas Field Development on the Ecological Red Line Area

To cooperate with the five ministries and commissions of the state to carry out joint investigation on the environmentally sensitive areas involved in oil and gas exploration and development,for the problems found in survey,containing complex type and numerous amount of ecologically sensitive space and ecological red line involved in oil and gas field enterprises,scientific nature of delimitation,lack of strong support of laws and regulations for forced withdrawal of oil and gas production facilities in these areas,some countermeasures and suggestions were proposed,such as further evaluating and combing scope and functional zoning of existing environmentally sensitive areas and ecological red lines,treating differently,enhancing pertinence of prohibition in ecologically sensitive regions,declining blindness of the withdrawal of oil and gas facilities in environmentally sensitive areas,strengthening seriousness of approval of exploration and mining rights of oil and gas resources,and establishing strategic reserve exploration and hierarchical development mechanism. Moreover,oil and gas field enterprises should integrate more efforts to ① accelerate to find out the current situation of environmental quality,② adhere to developing in protection,and protecting in development,③ increase attention and participation strengthen of providing technical support for national oil and gas exploration and development strategy evaluation,④ accelerate communication and docking with local governments on the ecological red line,⑤ actively strive to be included in the positive list management of local governments,⑥ accelerate to establish and perfect primary database of oil and gas production and facilities construction,and ⑦ document management information system of the ecological red line.

An Effective Thin Reservoir Identification Method for Fine Oilfield Development

Thin reservoirs prediction method such as spectral inversion has drawn considerable attention in recent years. In order to avoid extracting wavelets within the whole field area purposeless and to make the filtered data has preferable fidelity as well as signal-to-noise ratio, an effective structural constrained thin reservoir description method which combines spectral inversion and wide-band Ricker wavelet filtering technology has been proposed in this paper. The method given here is more credible and is suitable for the prediction of middle-deep thin reservoirs. We take LD-A structure within Bohai Bay Basin as an example to show the implement of our method. Several sets of thin sand layers which are hardly to recognize originally have been finally identified. Also, with the application of this method, a high-production thin reservoir of LD-B structure has been identified accurately, which provides credible information for subsequent fine oil exploration and development.

The mechanism of unconventional hydrocarbon formation: Hydrocarbon self-sealing and intermolecular forces

The successful development of unconventional hydrocarbons has significantly increased global hydrocarbon resources, promoted the growth of global hydrocarbon production and made a great breakthrough in classical oil and gas geology. The core mechanism of conventional hydrocarbon accumulation is the preservation of hydrocarbons by trap enrichment and buoyancy, while unconventional hydrocarbons are characterized by continuous accumulation and non-buoyancy accumulation. It is revealed that the key of formation mechanism of the unconventional reservoirs is the self-sealing of hydrocarbons driven by intermolecular forces. Based on the behavior of intermolecular forces and the corresponding self-sealing, the formation mechanisms of unconventional oil and gas can be classified into three categories:(1) thick oil and bitumen, which are dominated by large molecular viscous force and condensation force;(2) tight oil and gas, shale oil and gas and coal-bed methane, which are dominated by capillary forces and molecular adsorption;and(3) gas hydrate, which is dominated by intermolecular clathration. This study discusses in detail the characteristics, boundary conditions and geological examples of self-sealing of the five types of unconventional resources, and the basic principles and mathematical characterization of intermolecular forces. This research will deepen the understanding of formation mechanisms of unconventional hydrocarbons, improve the ability to predict and evaluate unconventional oil and gas resources, and promote the development and production techniques and potential production capacity of unconventional oil and gas.

Prospects of borehole NMR instruments and applications Dedicated to Professor Chaohui Ye on the occasion of his 80th birthday

Borehole nuclear magnetic resonance(NMR)is a powerful technology to characterize the petrophysical properties of underground reservoirs in the petroleum industry.The rising complexity of oil and gas exploration and development objectives,as well as the novel application contexts of underground reservoirs,have led to increasingly demanding requirements on borehole NMR technology including instrument design and related processing methods.This mini review summarizes the advances and applications of borehole NMR instruments along with some future possibilities.It may be helpful for researchers and engineers in the petroleum industry to understand the development status and future trends of borehole NMR technology.