Research progress and key issues of ultra-deep oil and gas exploration in China

Based on the recent oil and gas discoveries and geological understandings on the ultra-deep strata of sedimentary basins, the formation and occurrence of hydrocarbons in the ultra-deep strata were investigated with respect to the processes of basin formation, hydrocarbon generation, reservoir formation and hydrocarbon accumulation, and key issues in ultra-deep oil and gas exploration were discussed. The ultra-deep strata in China underwent two extensional-convergent cycles in the Meso-Neoproterozoic Era and the Early Paleozoic Era respectively, with the tectonic-sedimentary differentiation producing the spatially adjacent source-reservoir assemblages. There are diverse large-scale carbonate reservoirs such as mound-beach, dolomite, karst fracture-vug, fractured karst and faulted zone, as well as over-pressured clastic rock and fractured bedrock reservoirs. Hydrocarbons were accumulated in multiple stages, accompanied by adjusting and finalizing in the late stage. The distribution of hydrocarbons is controlled by high-energy beach zone, regional unconformity, paleo-high and large-scale fault zone. The ultra-deep strata endow oil and gas resources as 33% of the remaining total resources, suggesting an important successive domain for hydrocarbon development in China. The large-scale pool-forming geologic units and giant hydrocarbon enrichment zones in ultra-deep strata are key and promising prospects for delivering successive discoveries. The geological conditions and enrichment zone prediction of ultra-deep oil and gas are key issues of petroleum geology.

Analysis of the world deepwater oil and gas exploration situation

The global trends in deepwater oil and gas exploration,characteristics of deepwater oil and gas discovery,and layout of deepwater oil and gas exploration business by seven major international oil companies are systematically analyzed using commercial databases(e.g.S&P Global and Rystad)and public information of oil companies.The deepwater area is currently the most important domain for global oil and gas exploration and discovery,with the most discoveries and reserves in passive continental margin basins.The deepwater discoveries have the greatest contribution to the total newly discovered oil and gas reserves in the sea areas,with an increasing number of lithological reservoirs discovered,and oil and gas discoveries mainly distributed in the Mesozoic–Cenozoic.The seven major international oil companies are widely active in various aspects of deepwater oil and gas exploration and development,and play a leading role.Based on years of theoretical understanding of global oil and gas geology and resource evaluation,it is proposed that favorable deepwater exploration areas in the future will mainly focus on three major areas:the Atlantic coast,the Indian Ocean periphery,and the Arctic Ocean periphery.Six suggestions are put forward for expanding overseas deepwater oil and gas exploration business:first,expand the sources for obtaining multi-user seismic data and improve the scientific selection of deepwater exploration areas;second,increase efforts to obtain deepwater exploration projects in key areas;third,adopt various methods to access into/exit from resource licenses flexibly;fourth,acquire licenses with large equity and operate in“dual-exploration”model;fifth,strengthen cooperation with leading international oil companies in deepwater technology;and sixth,improve business operation capabilities and gradually transform from“non-operators”to“operators”.

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.

Bohai Bay Oil and Gas Exploration Contract Signed

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Regional gravity survey and application in oil and gas exploration in China

Ground gravity survey for regional structure unit delineation and oil and gas exploration in China is addressed in this paper with examples. Gravity survey scales, coverage, technical regulations and achievements at the national level are introduced, including data processing and anomaly interpretation techniques. Bouguer anomalies of terrestrial territories of China and classification of anomalous feature zones are also described;they are well correlated with lithotectonical boundaries, fault zones, and unexposed igneous plutons. Recent study results of petroliferous sedimentary basins are presented as well, including concealed boundaries and major structures of large basins. It is concluded that gravity survey is the most effective and economic method in unveiling unexposed and deep-seated structures, targeting and delineating oil and gas-bearing sedimentary basins, and locating main trap structures within prolific basins in early stage of exploration in China. Suggestions for improving exploration of both conventional and unconventional oil and gas reservoirs in China are also given in the paper.

Produced Water from Oil and Gas Exploration—Problems, Solutions and Opportunities

Large volumes of water are generated in gas- and oil-production. This includes the water that is present originally in the reservoirs, but also water that is injected into the wells. While currently much of the produced water is either reinjected or disposed of after treatment, treated produced water is increasingly seen as an interesting resource, especially in water-scarce regions. This review looks at different PW treatment methods available, with an emphasis on the management of PW in oil- and gas production on the Arabian Peninsula.

“Compression Dynamometamorphic Solid Bitmen” and Its Significance in Oil and Gas Exploration

There is natural occurrence of pressure-induced solid bitumen, here referred to as “compression dynamometamorphic solid bitumen”. It differs in physical properties and chemical structure from thermal metamorphic solid bitumen. Under a high pressure and moderate temperature, the solid bitumen forms crystals and its reflectance rises rapidly with increasing crystallization. Accordingly, its reflectance can reach a very high value without having been exposed to a high level of thermal stress. Laboratory simulation confirms the formation of pressure-induced solid bitumen at moderate temperatures. The revelation of this new bitumen type is very helpful in the accurate maturity determination of carbonate organic matter.

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.

'95 Achievements in Oil and Gas Exploration and Prospects for 1996

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Regression analysis and its application to oil and gas exploration:A case study of hydrocarbon loss recovery and porosity prediction,China

In oil and gas exploration,elucidating the complex interdependencies among geological variables is paramount.Our study introduces the application of sophisticated regression analysis method at the forefront,aiming not just at predicting geophysical logging curve values but also innovatively mitigate hydrocarbon depletion observed in geochemical logging.Through a rigorous assessment,we explore the efficacy of eight regression models,bifurcated into linear and nonlinear groups,to accommodate the multifaceted nature of geological datasets.Our linear model suite encompasses the Standard Equation,Ridge Regression,Least Absolute Shrinkage and Selection Operator,and Elastic Net,each presenting distinct advantages.The Standard Equation serves as a foundational benchmark,whereas Ridge Regression implements penalty terms to counteract overfitting,thus bolstering model robustness in the presence of multicollinearity.The Least Absolute Shrinkage and Selection Operator for variable selection functions to streamline models,enhancing their interpretability,while Elastic Net amalgamates the merits of Ridge Regression and Least Absolute Shrinkage and Selection Operator,offering a harmonized solution to model complexity and comprehensibility.On the nonlinear front,Gradient Descent,Kernel Ridge Regression,Support Vector Regression,and Piecewise Function-Fitting methods introduce innovative approaches.Gradient Descent assures computational efficiency in optimizing solutions,Kernel Ridge Regression leverages the kernel trick to navigate nonlinear patterns,and Support Vector Regression is proficient in forecasting extremities,pivotal for exploration risk assessment.The Piecewise Function-Fitting approach,tailored for geological data,facilitates adaptable modeling of variable interrelations,accommodating abrupt data trend shifts.Our analysis identifies Ridge Regression,particularly when augmented by Piecewise Function-Fitting,as superior in recouping hydrocarbon losses,and underscoring its utility in resource quantification refinement.Meanwhile,Kernel Ridge Regression emerges as a noteworthy strategy in ameliorating porosity-logging curve prediction for well A,evidencing its aptness for intricate geological structures.This research attests to the scientific ascendancy and broad-spectrum relevance of these regression techniques over conventional methods while heralding new horizons for their deployment in the oil and gas sector.The insights garnered from these advanced modeling strategies are set to transform geological and engineering practices in hydrocarbon prediction,evaluation,and recovery.

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.

Impacts of Oil Exploration (Oil and Gas Conflicts;Niger Delta as a Case Study)

The discovery of Oil and Gas in Nigeria led to exploration of crude oil for revenue basis. Oil exploration and exploitation caused environmental problems which resulted into major conflicts in the Niger Delta area of Nigeria. The article examines the impact of oil exploration, and oil and gas conflicts in Niger Delta area and it highlights the problems of pipeline vandalism, structure of oil and gas and the general obstacles in the industry. It discovers that pipeline vandalism, crude oil theft, pollution, oil spillage causes serious environmental degradation which resulted into serious conflicts. The article discovered that environmental problems in the area dislodged the people of their means of livelihood both in the area of fishing and farming. It recommends that there should be a compelling environmental restoration of natural resources by deploying land treatment technologies. Government should sanction multinational companies discharging oils or creating environmental pollution through necessary laws and regulations.

Evaluation of the oil and gas preservation conditions, source rocks, and hydrocarbongenerating potential of the Qiangtang Basin: New evidence from the scientific drilling project

The Qiangtang Basin of the Tibetan Plateau,located in the eastern Tethys tectonic domain,is the largest new marine petroliferous region for exploration in China.The scientific drilling project consisting primarily of well QK-1 and its supporting shallow boreholes for geological surveys(also referred to as the Project)completed in recent years contributes to a series of new discoveries and insights into the oil and gas preservation conditions and source rock evaluation of the Qiangtang Basin.These findings differ from previous views that the Qiangtang Basin has poor oil and gas preservation conditions and lacks high-quality source rocks.As revealed by well QK-1 and its supporting shallow boreholes in the Project,the Qiangtang Basin hosts two sets of high-quality regional seals,namely an anhydrite layer in the Quemo Co Formation and the gypsum-bearing mudstones in the Xiali Formation.Moreover,the Qiangtang Basin has favorable oil and gas preservation conditions,as verified by the comprehensive study of the sealing capacity of seals,basin structure,tectonic uplift,magmatic activity,and groundwater motion.Furthermore,the shallow boreholes have also revealed that the Qiangtang Basin has high-quality hydrocarbon source rocks in the Upper Triassic Bagong Formation,which are thick and widely distributed according to the geological and geophysical data.In addition,the petroleum geological conditions,such as the type,abundance,and thermal evolution of organic matter,indicate that the Qiangtang Basin has great hydrocarbon-generating potential.