Development technologies for Triassic Chang 7 shale oil in Ordos Basin: A case study of Qingcheng Oilfield, NW China

The reservoirs in the seventh member of the Triassic Yanchang Formation (Chang 7 Member) in the Qingcheng Oilfield of the Ordos Basin are characterized by thin sandbody, tight rocks, high heterogeneity, low formation pressure coefficient, and complex geomorphology. Through the efforts in the stages of exploration, appraisal, pilot testing and development, a series of key technologies have been formed, including “sweet spot” optimization, differentiated three-dimensional well deployment, fast drilling and completion of large-cluster horizontal well, intensively-staged volume fracturing in long horizontal well, and optimization of rational production system. Furthermore, a production organization mode represented by factory-like operations on loess platform has been implemented. Application of these technologies has enabled to significantly improve the single-well production of the Qingcheng Oilfield, reduce the investment cost, and realize a large-scale and beneficial development at a full cost below $55 per barrel. In 2022, the annual production of Chang 7 shale oil in the Ordos Basin reached 221×10^(4) t, accounting for 70% of the annual shale oil production of China. The practice of development technologies in the Qingcheng Oilfield provides valuable references for efficient development of continental shale oil.

Production evolution patterns and development stage division of waterflooding oilfields

The continuous growth of recoverable reserves in a waterflooding oilfield has a significant impact on the patterns of production evolution. A new production evolution model is established by improving the Weng Cycle model. With the new model, the statistical correspondence between the production decline stage and the reserve-production imbalance is clarified,and the correlation of water cut with the recovery percent of recoverable reserves is discussed, providing quantitative basis of reservoir engineering for dividing development stages of oilfield and defining mature oilfields. According to the statistics of oilfields in eastern China, the time point corresponding to the reserve-production balance coefficient dropping to less than 1dramatically is well correlated the beginning point of production decline, thus the time when the reserve-production balance coefficient drops dramatically can be taken as the initiation point of production decline stage. The research results show that the water cut and the recovery percent of recoverable reserves have a good statistical match in the high water cut stage, and it is more rational to take both the start point of production decline stage and the water cut of 90%(or the recovery percent of recoverable reserves of 80%) as the critical criteria for defining a mature oilfield. Five production evolution patterns can be summarized as follows: growth–peak plateau–stepped decline, growth–stepped stabilizing–stepped decline, growth–stepped stabilizing–rapid decline, growth–peak plateau–rapid decline, and growth–continuous decline.

Using a support vector machine method to predict the development indices of very high water cut oilfields

Because the oilfields in eastern China are in the very high water cut development stage, accurate forecast of oilfield development indices is important for exploiting the oilfields efficiently. Regarding the problems of the small number of samples collected for oilfield development indices, a new support vector regression prediction method for development indices is proposed in this paper. This method uses the principle of functional simulation to determine the input-output of a support vector machine prediction system based on historical oilfield development data. It chooses the kernel function of the support vector machine by analyzing time series characteristics of the development index; trains and tests the support vector machine network with historical data to construct the support vector regression prediction model of oilfield development indices; and predicts the development index. The case study shows that the proposed method is feasible, and predicted development indices agree well with the development performance of very high water cut oilfields.

New progress and prospect of oilfields development technologies in China

As technologies advance in oilfield development, mature oilfields are able to keep sustainable production and complex oilfields difficult to produce in the past are put into production efficiently. In this work, new progresses of main development technologies for medium-high permeability and high water cut, low permeability, heavy oil, complex faulted block and special lithology reservoirs in the past decade, especially those international achievements made in enhanced oil recovery, were summarized, the key problems and major challenges that different oilfields are facing were analyzed, and the development route and direction of three-generation technologies were proposed as "mature technology in industrialized application, key technology in pilot test and innovative technology for backup". The key research contents should focus on:(1) Fine water flooding and chemical flooding for mature oilfields, improving oil recovery after chemical flooding, and gas flooding for low permeability reservoirs must be researched and tested in field further.(2) Study on subversive technologies like nanometer smart flooding, in-situ upgrading and injection and production through the same well should be strengthened.(3) EOR technologies for low oil price, new fields(deep sea, deep layer, unconventional reservoirs etc.) and highly difficult conditions(the quaternary recovery after chemical flooding, tertiary recovery in ultra-low permeability reservoirs) should be stocked up in advance. The development cost must be lowered significantly through constant innovation in technology and reservoir management to realize sustainable development of oilfields.

The Application of Optimum Decision in Oilfield Development

The major steps of oilfield development are given in this paper. The optimal model of oilfield development is built and the methods of optimum decision analysis are studied. The solution and analysis of the optimal tactics have been set up according to the data collected in the oilfield.

Investigation of the influences of asphaltene deposition on oilfield development using reservoir simulation

This paper investigates the deposition of asphaltenes in the porous medium of the studied field in Russia and predicts production profiles based on uncertainty evaluation. This problem can be solved by dynamic modeling, during which production profiles are estimated in two scenarios: with and without the activation of the asphaltene option. Calculations are carried out for two development scenarios: field operation under natural depletion and water injection into the aquifer as a reservoir pressure maintenance system. A full-scale compositional reservoir simulation model of the Russian oilfield was created. Within a dynamic simulation, the asphaltene option was activated and the asphaltene behavior in oil and porous medium was tuned according to our own special laboratory experiments. The model was also matched to production historical data, and a pattern model was prepared using the full-scale simulation model. Technological and the asphaltene option parameters were used in sensitivity and an uncertainty evaluation. Furthermore, probable production profiles within a forecast period were estimated. The sensitivity analysis of the pattern model to input parameters of the asphaltene option allowed determining the following heavy-hitters on the objective function: the molar weight of dissolved asphaltenes as a function of pressure, the asphaltene dissociation rate, the asphaltene adsorption coefficient and the critical velocity of oil movement in the reservoir. Under the natural depletion scenario, our simulations show a significant decrease in reservoir pressure and the formation of drawdown cones leading to asphaltene deposition in the bottom-hole area of production wells, decreasing their productivity. Water injection generally allows us to significantly reduce the volume of asphaltene phase transitions and has a positive effect on cumulative oil production. Injecting water into aquifer can keep the formation pressure long above the pressure for asphaltene precipitation, preventing the asphaltene deposition resulted from interaction of oil and water, so this way has higher oil production.

Low cost development strategy for oilfields in China under low oil prices

By reviewing the challenges in the development of oilfields in China under low oil prices,this study analyzes the root causes of cost rising,put forwards the low cost oilfield development strategy and specific paths to realize the strategy,and predicts the development potential and prospect of oilfields in China.In addition to the low grade of the reservoir and high development maturation,the fundamental reasons of development full cost rising of oilfields in China are as follows:(1)Facing the problem of resources turning poorer in quality,we have built production capacity at a pace too fast before making enough technical and experimental preparation;(2)technical engineering service model leads to high service cost;(3)team of oil development expertise and matched engineering system cannot satisfy the technical requirements of stabilizing oil production,controlling water cut and fine development.To realize development at low cost,the core is to increase economic recoverable reserves.The concrete paths include:(1)to explore the"Daqing oilfield development culture",improve the ability of leaders in charge of development,and inspire potential of staff;(2)to improve the ability of reservoir dynamics control,and implement precise development by following scientific principles;(3)to speed up integration of water flooding and enhanced oil recovery(EOR)and technological upgrading in order to enhance oil recovery;(4)to innovate key techniques in gas flooding and accelerate the industrial popularization of gas flooding;(5)to break the related transaction barriers and create new management models;and(6)to collaboratively optimize strategic layout and cultivate key oil bases.Although oilfield development in China faces huge challenges in cost,the low-cost development strategy will succeed as long as strategic development of mature and new oil fields is well planned.The cores to lower cost are to control decline rate and enhance oil recovery in mature oil fields,and increase single well productivity through technical innovation and improve engineering service efficiency through management innovation in new oil fields.

Characteristics of Water Flooding in Thick Reservoirs of Shuanghe Oilfield and Adjustment in the Late Development Period with High Water Cut

The Heterogeneity of the Thick Glutenite Reservoirs and the Direction for Exploit-ing Potential at a Period of Very High Wa-ter Cut

Development Techniques of Zaoyuan Oilfield

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＇96 International Symposium on Well Logging Techniques for Oilfield Development under Waterflooding

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Exploration technology and development trend of Daqing Oilfield

Exploration for oil and deep gas in northern Songliao Basin,complex rift basin—Hailaer Basin,and Yi-Shu Graben in peripheral basin has technical challenge.Researches on supporting technology including seismic acquisition,processing and interpretation,logging and drilling are performed to establish high resolution 3D seismic technology for lithologic reservoir,deep volcanic rock and complex rift basin,reservoir evaluation and stimulation technology for low permeability reservoir,volcanic reservoir and complex rift reservoir,and drilling technology for deep volcanic rock,providing technical support for reserves increase in northern Songliao Basin,large gas reservoirs discovery in deep volcanic rock and exploration progress in complex rift basin.Next-step development trend of exploration technology is proposed to meet the demand of more technical challenges in the future.

大庆油田油藏工程技术的创新发展与攻关方向

简要回顾了大庆油田开发65 a来油藏工程技术的进步历程,梳理了大庆油田立足油田开发实践创新形成的开发地质、数值模拟、水驱开发、化学驱油、油田开发规划编制方法5项综合研究体系;总结了在油藏工程领域创新发展的小层对比、精细储量计算、注水倍数对驱油效率的影响规律、全国第一条相渗透率曲线研制、小井距注水全过程开发试验、高含水期剩余油分布类型、高含水期稳油控水系统工程、聚合物黏弹性驱油理论和低酸值原油大幅度提高采收率的三元复合驱油理论10项行业领先的关键理论技术;提出了大庆油田持续开发面临的5大难题和需要进一步攻关的高含水区精细挖潜、天然气高效开发、CO_(2)驱油、微生物驱油、非常规油藏开发、地热能源开发、智能油田和高效优质驱油剂研制8项技术。研究成果为大庆油田可持续发展奠定了理论基础。

大庆油田特高含水期原油开发规划技术发展现状与展望

开发规划在油田开采过程中发挥着重要的龙头指导作用,是油田企业在一定时期内制定的行动纲领和指南。开发规划技术水平的高低直接影响油田开发的效果和效益。在明确开发规划的基本内涵及与计划、战略的区别基础上,着重介绍了大庆油田发展的2类7项开发规划系列技术,包括开发规律及指标预测技术、技术经济政策界限确定技术、开发效果及潜力评价技术、规划编制及优化技术4项核心技术和可采储量及SEC储量评估技术、经济效益评价及决策支持技术、规划信息化技术3项支撑技术。通过分析当前油田开发规划技术发展存在的生产与技术难题,明确了3个发展方向以及3条实现路径。研究成果与认识对油田开发规划理论研究和实际应用具有重要的参考价值和借鉴意义。

长庆油田数智化油藏建设理论与实践

随着油气勘探认识和技术的不断进步,盆地边缘新层系非常规储层成为油气增储上产的重要领域,开采难度增加,工作量培增。然而,油田用工总量不增反降,如何提升油气藏研究的精细化水平,培育新质生产力,打造油田高质量发展新引擎,是油田急需解决的问题。长庆油田制定了“125”数智化油藏建设规划,通过数智化技术,助力资源勘探、油气开发和新能源3大主业的高质量发展。立足数智化油藏学科长远建设,结合地质研究、井位部署与随钻、产能建设、稳产提产等领域的数智化建设特点,总结出一套高效稳健的数智化油藏建设理论与方法,形成了“一体系四中台”基本建设思路,制定了勘探开发数智化整体解决方案。在该理论指导下,建成了数字油气藏研究与决策支持平台,有效推进了长庆油田的快速上产稳产,现已成为中国石油天然气集团有限公司的品牌产品,支撑着长庆油田向国际一流大油气田迈进。

胜利油田油藏描述技术回顾与发展方向

胜利油田为典型的陆相复式油气区,油藏类型多、含油层系多、断裂系统复杂,20世纪90年代初进入含水率为90%以上的特高含水开发阶段,如何针对不同类型油藏和开发阶段,精细刻画地下储层变化、精准认识剩余油,是实现高含水老油田提高采收率的基础。为此,从1996年始开展了针对老油田剩余油挖潜的精细油藏描述,通过精细储层构型表征、低序级断层精细描述、砂砾岩期次划分与连通性评价、薄互层滩坝砂储层预测、三维精细地质建模及剩余油精细描述等关键技术攻关,以及多轮次油藏描述技术迭代,形成了一套胜利特色的精细油藏描述技术,编制了精细油藏描述技术规范。截至2023年累计描述开发单元600余个,覆盖石油地质储量为43.6×108 t,建模数模技术在老区调整和新区方案编制中得到广泛应用,有效支撑了油田的规模建产与效益稳产。系统分析胜利油田油藏描述技术发展历程,总结不同类型油藏形成的特色技术,分析特高含水后期老油田精细油藏描述面临的5项挑战,阐述下一步油藏描述技术的5个发展方向,对推动陆相油田精细油藏描述技术具有指导和借鉴意义。