Search

This paper presents an analysis of four aspects, including the distribution and production of global oil and gas fields, the distribution and changes of remaining recoverable reserves, the differences in oil and gas production between regions/countries, and the development potentials of oil and gas fields unproduced and to be produced in 2023. On this basis, the situation and characteristics of global oil and gas development are expounded, and the trend of global oil and gas development is summarized. In 2023, upstream oil and gas production landscape is expanding, and the number of oil and gas fields in production is increasing significantly; oil and gas recoverable reserves increased year-on-year, driven by significant contributions from new discoveries and reserve re-estimates; the overall oil and gas production grew continuously, with notable contributions from new projects coming online and capacity expansion efforts; and the oil and gas fields unproduced or to be produced, especially large onshore conventional oil fields and economically challenging offshore gas fields, host abundant recoverable reserves. From the perspectives of reshaping oil and gas production areas due to the pandemic and Russia-Ukraine conflicts, geopolitical crises, capital expenditure structures in petroleum exploration and development, and the proactive layout of oil and gas associated resources, the trend of global oil and gas development in 2023 was analyzed systematically. The enlightenment and suggestions in four aspects are proposed for Chinese oil companies to focus on core businesses and clarify development strategies in the post-pandemic era and the context of energy transition: The global oil and gas landscape is undergoing profound adjustments, and it is essential to grasp development trends, especially in core businesses; upstream business exhibits a strong potential, and emerging fields are considered as new growth poles; the prospects for tight/shale oil and gas are promising, and new pathways to ensure national energy security are explored; cutting-edge breakthroughs are achieved in emerging industries of strategic importance, and a comprehensive energy collaboration system for supply security is established.

Through analysis of four aspects, including the distribution and production of global oil and gas fields, the distribution and changes of remaining recoverable reserves, the differences in oil and gas production between regions/countries, and the development potential of oil and gas fields with production capacity not built and to be built, this paper presents the situation and trends of global oil and gas development in 2022. It is found that, in 2022, oil and gas fields are widely distributed worldwide, and upstream production activities continue to recover; the oil and gas reserves decrease slightly year on year, and the oil and gas reserves in sea areas increase significantly; the oil and gas production increases continuously, and the key resource countries make a significant contribution in oil and gas production growth; the oil and gas fields with production capacity not built and to be built hold abundant reserves, and their development potential will be gradually released with the economic benefits increase. Further analysis is conducted from the perspectives of global oil and gas resources continuity, geopolitical risks, potential of international cooperation, and upgrade of unconventional oil and gas technology. Finally, in view of core business domains and strategies under the new situation, the Chinese oil companies are recommended to: (1) keep a foothold in onshore conventional oil and gas development by virtue of their comparative advantages and learning from other's experience in cooperation; (2) carry out pilot tests on development adjustment, and deepen the international cooperation in enhanced oil/gas recovery; (3) improve the oil and gas operation capabilities in sea areas to transform from follower as minority shareholder to joint venture and then to independent operations; and (4) seek appropriate ways for shale oil/gas development to reduce the dependence on foreign oil and gas.

By analyzing the distribution of global oil and gas fields and the reasons why some oil and gas fields are not in production, the distribution characteristics of oil and gas remaining recoverable reserves and their year-on-year changes, the distribution characteristics of oil and gas production and their year-on-year changes, and the development potential of oil and gas to be tapped in 2021, this paper sorts out systematically the current status and characteristics of global oil and gas development, summaries the major trends of global oil and gas development, puts forward enlightenment for international oil and gas cooperation. In 2021, oil and gas fields were widely distributed, the number of non-producing oil and gas fields was large; the whole oil and gas remaining recoverable reserves declined slightly, unconventional oil and gas remaining recoverable reserves dropped significantly; the overall oil and gas production continuously increased, the outputs of key resource-host countries kept year-on-year growth; undeveloped oilfields had abundant reserves and great development potential. Combined with global oil and gas geopolitics, oil and gas industry development trends, oil and gas investment intensity, and the tracking and judgment of hotspot fields, the major trends of global oil and gas development in 2021 are summarized. On this basis, the four aspects of enlightenment and suggestions for international oil and gas cooperation and development strategies are put forward: attach great importance to the obligation of marine abandonment to ensure high-quality and long-term benefit development of offshore oil and gas; adhere to the principle of not going to dangerous and chaotic places, strengthen the concentration of oil and gas assets, and establish multi stable supply bases; based on the multi-scenario demand of natural gas, realize the transformation from integrated collaboration to full oil and gas industry chain development; increase the acquisition of high-quality large-scale assets, and pay attention to the continuous optimization of the shareholding ratio of projects at different stages.

Carboniferous carbonate reservoirs at the eastern edge of the Pre-Caspian Basin have undergone complex sedimentation, diagenesis and tectonism processes, and developed various reservoir space types of pores, cavities and fractures with complicated combination patterns which create intricate pore-throats structure. The complex pore-throat structure leads to the complex porosity-permeability relationship, bringing great challenges for classification and evaluation of reservoirs and efficient development. Based on the comprehensive analysis on cores, thin sections, SEM, mercury intrusion, routine core analysis and various tests, this paper systematically investigated the features and main controlling factors of pore-throats structure and its impact on the porosity-permeability relationship of the four reservoir types which were pore-cavity-fracture, pore-cavity, pore-fracture and pore, and three progresses are made. (1) A set of classification and descriptive approach for pore-throat structure of Carboniferous carbonate reservoirs applied to the eastern edge of the Pre-Caspian Basin was established. Four types of pore-throat structures were developed which were wide multimodal mode, wide bimodal mode, centralized unimodal mode and asymmetry bimodal mode, respectively. The discriminant index of pore-throat structure was proposed, realizing the quantitative characterization of pore-throat structure types. (2) The microscopic heterogeneity of pore reservoir was the strongest and four types of pore-throat structures were all developed. The pore-fracture and pore-cavity-fracture reservoirs took the second place, and the microscopic heterogeneity of pore-cavity reservoir was the weakest. It was revealed that the main controlling factor of pore-throat structure was the combination patterns of reservoir space types formed by sedimentation, diagenesis and tectonism. (3) It was revealed that the development of various pore-throat structure types was the important factor affecting poroperm relationship of reservoirs. The calculation accuracy of permeability of reservoirs can be improved remarkably by subdividing the pore-throat structure types. This study deepens the understanding of pore-throat structure of complicated carbonate reservoirs, and is conducive to classification and evaluation, establishment of precise porosity-permeability relationship and highly efficient development of carbonate reservoirs.

Based on about 20 years of accumulated experience and knowledge of oil and gas field development in overseas countries and regions for China's oil companies, the development features, ideas, models and plan designing strategies of overseas oil and gas fields were comprehensively summarized. Overseas oil and gas field development has ten major features, such as non-identity project resource, diversity of contract type, complexity of cooperation model, and so on. The overseas oil and gas field development aims at the maximization of production and benefit during the limited contract period, so the overseas oil and gas field development models are established as giving priority to production by natural energy, building large-scale production capacity, putting into production as soon as possible, realizing high oil production recovery rate, and achieving rapid payback period of investment. According to the overseas contract mode, a set of strategies for overseas oil and gas field development plans were made. For tax systems contracts, the strategy is to adopt the mode of “first fat and then thinner, easier in the first and then harder”, that is, early investment pace, production increase rate, development workload and production were decided by the change of tax stipulated in the contract. For production share contracts, the strategy is to give priority to high production with a few wells at a high production recovery rate to increase the cost-oil and shorten the period of payback. For technical service contracts, the strategy is that the optimal production target and workload of the project were determined by the return on investment, so as to ensure that the peak production and stable production periods meet the contract requirements. Key words: overseas oil and gas field, development ideas, technical strategy, development model, contract type, development plan design

Due to superheated steam as a pure gas, the ordinary steam model for the calculation of horizontal well-bore parameters based on two phases flow theory isn't applicable to the superheated steam injection process. According to the conservation of mass, conservation of momentum and conservation of energy, a calculation model for on-way parameters of horizontal well-bore in the superheated steam injection considering the steam phase changing is set up. The on-way parameters of temperature, pressure and dryness of a horizontal well injected superheated steam from Kazakhstan Kumsai oilfield is calculated using the model, and the calculation result of the new model is in good agreement with that of the field data, which verifies the effectiveness of the model. Sensitivity analysis indicates that the length to the heel of horizontal well undergoing the steam phase state changing increases as the injection rate or the degree of superheat increases, but the increase extent is not significant when the injection rate is larger than 8 t/h or the degree of superheat is larger than 80 °C. In the permeability distribution pattern that the permeability increases along the horizontal well-bore, steam temperature is decreased at the lowest rate and the length to the heel of horizontal well undergoing the steam phase changing is the longest. Key words: heavy oil, horizontal well, superheated steam, steam phase changing, on-way parameters, calculation model, steam injection rate

The pressure balance between gas cap and oil ring is likely to be broken during their concurrent production in gas cap reservoirs. In order to increase the whole development efficiency of the concurrent production of gas cap and oil ring, the Zhanzhol gas cap reservoir of Kazakhstan was taken as example to carry out the research, a three-dimensional visualization physical model was established based on the similarity criterion of oil phase, gas phase and water phase, and a reservoir engineering model of fluid interface moving rate was also set up according to the material balance principle. The calculation results of reservoir engineering model tally with the results of physical simulation experiment and reservoir dynamic test data. The moving rate template of fluid interface under three development modes, depletion development, barrier water injection development and barrier plus pattern water injection development have been also established by reservoir engineering method. The main controlling factors under different development modes have been figured out: for depletion development, the main controlling factors on the stabilization of oil-gas contact are oil recovery rate and gas recovery rate; for barrier water injection development, the main controlling factors are oil recovery rate, gas recovery rate and production-injection ratio; and for barrier plus pattern water injection development, the main controlling factors are oil recovery rate, gas recovery rate, production-injection ratio and the ratio of barrier water injection to pattern water injection. Key words: Zhanzhol oil field, gas cap reservoir, concurrent production of gas cap and oil ring, fluid interface, moving rule

Reservoir Γ north, which belongs to Zhanzhol, Kazakhstan, a fracture-pore typed carbonate oilfield, has a variety of reservoir types. According to the combination pattern of different voids and the relationship between porosity and permeability, carbonate reservoirs are classified into four types which are fracture-cavity-pore typed (referred to as composite typed here after), fracture-pore typed, pore typed and fracture typed, and the identification of which by well logging data is realized. There is a little difference in the producing degree within the same reservoir type for composite typed and fracture typed reservoirs. However, there are large differences in the producing degree for fracture-pore typed and pore typed reservoirs. In order to appraise the producing degree of reservoirs more exactly, key parameters affecting the producing degree of fracture-pore typed and pore typed reservoirs are selected separately, which, for the fracture-pore typed are reservoir quality index (RQI), pore throat radius at mercury saturation of 50% (R50), total permeability (Kf+Km), and the ratio of fracture permeability to matrix permeability (Kf/Km), and for the pore typed are RQI, R50, and matrix permeability (Km). With the integrated consideration of matrix and fracture, a flow unit classification method for dual medium reservoir is established, and taking these parameters as clustering variants, four types of reservoirs are further divided into six kinds of reservoir flow units by the means of neural network clustering technology. Based on reservoir flow unit modeling, a numerical simulation model is built with each type of reservoir flow units adopting its corresponding relative permeability curve, based on which, the distribution regularity of remaining oil of reservoir Γ north is studied and demonstrated. Eight new wells are designed according to the research result, and put into production in 2013 with the initial daily oil production rate being 2.3 times that of nearby old wells. Key words: carbonate oil reservoir, reservoir type, reservoir flow unit, neural network clustering technology, reservoir flow unit model, remaining oil

Taking the Kumkol oilfield of high water cut in the South Turgay Basin, Kazakstan as an example, this article built the architecture models of meandering river sandstones, braided river sandstones and delta sandstones, and analyzed the influence of the superimposed structure characteristics between different types of sandstones and internal architecture features on warterflooding mechanisms and effects. The meandering river sandstones are mainly characterized by lateral accretion shale beddings inside, with simple overlay-relationship in sand bodies. In meandering river sandstones, injected water almost sweeps through the bottom of sand bodies and the bottom part of the sandstones is previously waterflooded, and the thickness ratio of strong and moderate waterflooded zone is about 51.8%. Braided river sandstones are characterized by nearly horizontal interlayers inside, with low heterogeneity and uniform waterflooding sweep vertically, and the thickness ratio of strong and moderate waterflooded zone is as high as 81.7%. The superimposed structure and architecture of delta sandstone is relatively complicated; different types of sandstones overlay each other frequently and shale interbeds are developed in sandstones. The injected water is obstructed not only by impermeable or low-permeable layers between sand bodies but also by shale interbeds in sandstones, with low sweep range of injected water, and the thickness ratio of strong and moderate waterflooded zone is only 32.6%. The braided river sandstone has low rising velocity of water cut and high no-water recovery degree, and its waterflooding development effect is the best. The waterflood sweep of delta sandstones is poor, with fast rising velocity of water cut and low no-water recovery degree, and its waterflooding development effect is the worst. The waterflooding development effect of meandering river sandstones is moderate among these three types of sandstones. Key words: South Turgay Basin, sandstone type, meandering river, braided river, delta, warterflooding degree, warterflooding characteristics, remaining oil

Taking the Kenjiyak Oilfield in Kazakhstan as an example, the fracture characteristics and genetic mechanism of carbonate reservoirs with overpressure were discussed. The study showed that carbonate reservoirs are formed under overpressure developed hydraulic fractures besides tectonic fractures and karstic fractures. The Carboniferous sub-salt hydraulic fractures in Kenkiyak are mainly formed in the Mesozoic and Cenozoic, on a macroscopic level they cut rocks into brecciated texture or are packed by calcite veins, on a microscopic level they are in a radiant distribution around pores. The formation and evolution of the fracture system in the region experienced three main stages, including structure transforming and uplifting, structure stretching and subsiding, and hydraulic cracking. In the stage of hydraulic cracking, salt movement and tectonic movement lead to the formation of overpressure zone, with the pressure coefficient of 1.84. Overpressure leads to the formation of hydraulic fractures in the Carboniferous low permeable carbonate reservoirs under the Permian non-permeable mudstones, and also leads to reopening, widening and prolonging of former tectonic fractures. Hydraulic fractures are mainly the extensional fracture, which has late opening time and low filling degree, thus is the main effective fractures in the study area. 摘要: ：以哈萨克斯坦肯基亚克油田为例讨论了异常高压碳酸盐岩油藏储集层裂缝特征及形成机制。异常高压条件下形成的碳酸盐岩储集层除发育构造裂缝和岩溶裂缝外，还发育水力破裂缝。盐下石炭系水力破裂缝形成于中、新生代，宏观上表现为将岩体切割成角砾状及充填方解石脉，微观上表现为沿孔隙周围呈放射状分布。该区裂缝系统的形成与演化经历了3个主要阶段，即构造变形与抬升阶段、构造拉张与沉降阶段、水力破裂阶段。在水力破裂阶段，在盐丘活动、构造运动等多种因素作用下，盐下地层中形成异常高压带，压力系数高达1.84，在异常高压条件下，二叠系泥岩不渗透层下的石炭系碳酸盐岩低渗透层发生破裂，形成水力破裂缝，同时使早期闭合的裂缝开启、扩张和延伸。水力破裂缝以张性裂缝为主，其张开时间晚，充填程度低，是研究区主要的有效裂缝。图8参13 Key words: carbonates, overpressure, tectonic fracture, hydraulic fracture, genetic mechanism