Simulating the Effect of Hydrate Dissociation on Wellhead Stability During Oil and Gas Development in Deepwater

It is well known that methane hydrate has been identified as an alternative resource due to its massive reserves and clean property. However, hydrate dissociation during oil and gas development(OGD) process in deep water can affect the stability of subsea equipment and formation. Currently, there is a serious lack of studies over quantitative assessment on the effects of hydrate dissociation on wellhead stability. In order to solve this problem, ABAQUS finite element software was used to develop a model and to evaluate the behavior of wellhead caused by hydrate dissociation. The factors that affect the wellhead stability include dissociation range, depth of hydrate formation and mechanical properties of dissociated hydrate region. Based on these, series of simulations were carried out to determine the wellhead displacement. The results revealed that, continuous dissociation of hydrate in homogeneous and isotropic formations can causes the non-linear increment in vertical displacement of wellhead. The displacement of wellhead showed good agreement with the settlement of overlying formations under the same conditions. In addition, the shallower and thicker hydrate formation can aggravate the influence of hydrate dissociation on the wellhead stability. Further, it was observed that with the declining elastic modulus and Poisson's ratio, the wellhead displacement increases. Hence, these findings not only confirm the effect of hydrate dissociation on the wellhead stability, but also lend support to the actions, such as cooling the drilling fluid, which can reduce the hydrate dissociation range and further make deepwater operations safer and more efficient.

Deepwater and Deep Layers： the Strategic Choices for China＇s Oil and Gas Resources Development

On December 2, 2017, the 2nd Seminar on the Development Strategy of China＇s Oil and Gas Resources was held in Beijing. This seminar was hosted by the Strategic Research Center for Oil and Gas Resources, Ministry of Land （MLR） and Resources and sponsored by both the CNOOC Exploration Department and the School of Ocean and Earth Sciences of Tongji University. With the theme of ＂deepwater and deep-layer oil and gas resources and development strategy＂,

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.

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”.

Measures of Environmental Protection of Petroleum Exploration and Development in Tarim Basin

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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.

Reservoir accumulation conditions and key exploration&development technologies for Keshen gas field in Tarim Basin

The Keshen gas field is located in the central part of Kuqa foreland thrust belt in Tarim Basin,and is another large gas field discovered in Kuqa depression after Kela 2 gas field.Since the breakthrough in 2008,a number of large and medium scale gas reservoirs including Keshen 2,Keshen 5 and Keshen 8 have been discovered,that are characterized by ultra depth,ultra-high pressure,ultra-low porosity,ultra-low permeability,high temperature and high pressure.With natural gas geological reserves of nearly trillion cubic meters and production capacity of nearly 5.5 billion cubic meters,the Keshen gas field is the main natural gas producing area in Tarim Oilfield.The Keshen gas field is located in a series of thrusting imbrication structures in the Kelasu structural belt of Kuqa foreland thrust belt.The salt roof structure,plastic rheology of salt beds and pre-salt faulted anticlinal structure constitute the large wedge-shaped thrust body.The thick delta sandstone of the Cretaceous Bashijike Formation is widely distributed,and it forms the superior reservoir-caprock combination with overlying Paleogene thick gypsum-salt bed.The deep Jurassic-Triassic oil and gas migrate vertically along fault system formed in Late Himalaya,break through the thick Cretaceous mudstone and move laterally along the fracture system of the pre-salt reservoirs,to form anticline and fault anticline high pressure reservoir groups.Through near ten years of studies,the three-dimensional seismic acquisition and processing technology for complex mountainous areas,extrusion salt-related structural modeling technology and fractured low-porosity sandstone reservoir evaluation technology have been established,which lay a foundation for realization of oil and gas exploration objectives.Logging acquisition and evaluation technology for high temperature,high pressure,ultra-deep and low-porosity sandstone gas reservoirs,and efficient development technology for fractured tight sandstone gas reservoirs have been developed,which provide a technical support for efficient exploration&development and rapid production of the Keshen gas field.

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.

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 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.

全球深水油气勘探开发进展与研究综述

海洋油气勘探开发进入深水、超深水阶段,是全球油气资源供应的重要来源。从国际、国内两个层面,资源、技术、政策与企业行为多个维度,系统梳理相关研究成果,形成了全球深水油气勘探开发领域的综合认识。研究结果表明,深水油气盆地集中分布在被动大陆边缘,呈现“三竖两横”分布特征,资源潜力巨大;资源国政府、石油公司和油服公司等多类主体共同参与深水油气勘探开发的全流程多环节,政策体系、商业运作模式和技术装备能力日益成熟。研究认为,深水油气勘探开发面临重大机遇,政府部门和油气行业需高度重视,建议从政策支持、商业运作和技术发展多方面全向发力,积极应对。

国外深水钢悬链线立管研究发展现状

介绍国外在新型深水立管系统——钢悬链线立管关键技术方面的研究发展现状,论述浮体一、二阶运动对钢悬链线立管疲劳寿命的影响、浮体升沉运动对钢悬链线立管触地点疲劳寿命的影响;钢悬链线立管与海底相互作用机制的实验研究及结果;钢悬链线立管涡致振动与疲劳的研究现状。并简要论述钢悬链线立管触地点问题的研究结论。

全球深水油气勘探开发现状、前景及启示

全球深水油气资源丰富,在全球油气储产量中占有日益重要的地位。本文概述了全球深水油气勘探开发的现状,分析了其分布特征,总结了当前深水油气勘探开发的特点和趋势,认为全球深水勘探开发投入逐年增加,开发方式不断革新,勘探开发时间差缩短,开发成本持续下降,开发领域和方向不断拓展。通过比较各油气盆地的油气成藏条件、资源潜力、已发现油气储量和勘探程度等,优选了深水沉积盆地勘探开发的三个方向,提出了相关思考和建议。

深海油气地震勘探进展和展望

20世纪 90年代后期以来 ,随着深海技术的进步 ,寻找新型大油气田的成功率明显上升 ,深海勘探进入了一个新的纪元 .本文较为详尽的综述了近几年国外在深海石油地震勘探中的关键技术和新发现 ,主要包括 :(1)似地震反射面勘探技术探测天然气水合物 ,(2 )混合地震反演技术 ,(3)区域多次二维叠前深度偏移技术 ,(4)地震和地质力学方法 ,(5 )近偏移距压制多次波 .在将来的 10年 ,国外深海作业的一些领域如电子油田、钻探成像、实时深度成像、多分量成像、环境和灾害分析。

世界深水油气勘探开发态势及启示

全球深水油气资源丰富,勘探不断取得重大发现,国际大石油公司争相在这一领域施展技能,逐步把深水油气资源勘探开发推向更高的阶段。近几年,深水储量、产量双双攀升,在海洋油气储、产总量中的比重不断增加,大型深水装置需求旺盛,研发、建造活跃,深水勘探开发能力已成为国际一流大石油公司的重要标志之一,深水技术成为全球油气技术创新的主攻方向。我国南海深水资源也很丰富,中国石油集团应加快发展深水业务,为保证国家能源安全做出新贡献,建议:制定中长期油气开发计划,实施国际化海洋资源战略;组建专门机构发展业务,提升战略地位;与国际大石油公司、资源国国家石油公司建立战略联盟;重视技术创新和超前储备;制定海洋人才计划、加快人才培养等。

发展海工设备制造,走向世界海洋石油市场

近年来,深海油气勘探开发发展迅速,在2000~2005年全球新增油气储量中,陆上、浅水和深水分别占28%、31%和41%。与此相应,该领域的投资也持续快速增长,据预测,2012年全球海域作业支出将达到3610亿美元,比2007年增长42.1%,其中深水增幅约74%。在影响海上油气发展的诸多因素中,有两个问题最为业内人士所关注。一是海上油气发展需要大量的设备,而所涉及的种类众多的设备和技术必须形成智能化的配套体系;二是要有能胜任海上石油运作实力强大的团队,它不仅拥有投资和抗风险的实力,也要具有一流的技术和管理人才团队。近两年我国海工设备制造已进入深水领域,中国各大造船厂与各大石油公司的海工基地一起,组成了我国正蓬勃兴起的海洋石油装备制造队伍。但同时在这个领域也存在着专业化程度和关键设备国产化程度偏低,深水、超深水配套能力不足等问题。我国应将海上石油设备研制作为走向制造强国的＂抓手＂之一,统一规划,形成协同发展的合力。在拥有了适用于深水的设备并形成初步配套后,就可大踏步走向世界海洋石油市场,在实践中进一步提高设备制造的水平和配套的完整性。此外,我国在南海应更加积极主动地进行勘探开发活动,以深水勘探打破南海油气停滞、被动的局面。

浅谈深海钻井中钻井液适应性评价与应用

随着工业的发展,人类对能源的需求越来越大,人类把石油的勘探开发目光集中到深海。深海海洋油气勘探存在着很多作业难度,具体有作业区域水深、深海钻井难度大等。深海钻井液作业存在着易形成天然气水合物、大尺寸井眼岩屑上返困难、低温钻井液流变性控制困难、钻井液易漏等特点,深海钻井工程也是一项高风险、高投资作业,深海钻井液质量在深海钻井工程中显得尤为重要。

深水油气勘探开发锚泊事故研究及对策分析

深水油气勘探开发锚泊事故主要包括锚索断开、走锚和制动系统失效等类型,如果控制不当可能造成人员伤亡、生产停产、平台碰撞倾覆和井喷等严重后果。鉴于此,通过调研国内外锚泊事故案例,总结事故失效类型以及各类事故的形成原因、影响因素和失效模式,提出了不同失效类型事故的预防措施和应对策略。分析了典型的外部影响因素对锚泊事故的影响,并提出台风和内波等外因影响下的锚泊事故风险应对策略。研究内容可为我国深水锚泊系统优化设计、制造加工工艺的改进以及风险分析提供参考,从而提高我国深水油气勘探开发过程中锚泊作业安全管理能力和事故应急能力。