Progress and prospects of oil and gas production engineering technology in China

This paper summarizes the important progress in the field of oil and gas production engineering during the"Thirteenth Five-Year Plan"period of China,analyzes the challenges faced by the current oil and gas production engineering in terms of technological adaptability,digital construction,energy-saving and emission reduction,and points out the future development direction.During the"Thirteenth Five-Year Plan"period,series of important progresses have been made in five major technologies,including separated-layer injection,artificial lift,reservoir stimulation,gas well de-watering,and workover,which provide key technical support for continuous potential tapping of mature oilfields and profitable production of new oilfields.Under the current complex international political and economic situation,oil and gas production engineering is facing severe challenges in three aspects:technical difficulty increases in oil and gas production,insignificant improvements in digital transformation,and lack of core technical support for energy-saving and emission reduction.This paper establishes three major strategic directions and implementation paths,including oil stabilization and gas enhancement,digital transformation,and green and low-carbon development.Five key research areas are listed including fine separated-layer injection technology,high efficiency artificial lift technology,fine reservoir stimulation technology,long term gas well de-watering technology and intelligent workover technology,so as to provide engineering technical support for the transformation,upgrading and high-quality development of China’s oil and gas industry.

Achievements and future work of oil and gas production engineering of CNPC

This paper summarizes the latest achievements and technological progress in oil and gas production engineering of China National Petroleum Corporation(CNPC) and discusses the main four challenges faced: developing low quality resource at low oil price; keeping stable production of mature oilfields when well oil production drops year by year; low systematic efficiency, high cost, prominent environmental protection issue and short of technological strategy for high water cut ratio and high oil recovery ratio oilfields; and lacking of high level horizontal well drilling and completion technology to develop unconventional and deep reservoirs. Three technological development directions to address these challenges are put forward: developing fracture controlling stimulation and well factory to produce low quality resource economically, developing re-fracturing technology for old wells in mature oilfields, promoting the fourth generation separate layer water injection technology to stabilize the production of mature oilfields; innovating new technologies of water flooding with nano-material, injecting and producing through one well.

Multistring analysis of wellhead movement and uncemented casing strength in offshore oil and gas wells

This paper presents a theoretical method and a finite element method to describe wellhead movement and uncemented casing strength in offshore oil and gas wells.Parameters considered in the theoretical method include operating load during drilling and completion and the temperature field,pressure field and the end effect of pressure during gas production.The finite element method for multistring analysis is developed to simulate random contact between casings.The relevant finite element analysis scheme is also presented according to the actual procedures of drilling,completion and gas production.Finally,field cases are presented and analyzed using the proposed methods.These are four offshore wells in the South China Sea.The calculated wellhead growths during gas production are compared with measured values.The results show that the wellhead subsides during drilling and completion and grows up during gas production.The theoretical and finite element solutions for wellhead growth are in good agreement with measured values and the deviations of calculation are within 10％.The maximum von Mises stress on the uncemented intermediate casing occurs during the running of the oil tube.The maximum von Mises stress on the uncemented production casing,calculated with the theoretical method occurs at removing the blow-out-preventer （BOP） while that calculated with the finite element method occurs at gas production.Finite element solutions for von Mises stress are recommended and the uncemented casings of four wells satisfy strength requirements.

Exploration prospects of oil and gas in the Northwestern part of the Offshore Indus Basin, Pakistan

Oil and gas resources are short in Pakistan and no commercially viable oil and gas sources have been yet discovered in its offshore areas up to now.In this study,the onshore-offshore stratigraphic correlation and seismic data interpretation were conducted to determine the oil and gas resource potential in the Offshore Indus Basin,Pakistan.Based on the comprehensive analysis of the results and previous data,it is considered that the Cretaceous may widely exist and three sets of source rocks may be developed in the Offshore Indus Basin.The presence of Miocene mudstones has been proven by drilling to be high-quality source rocks,while the Cretaceous and Paleocene–Eocene mudstones are potential source rocks.Tectonic-lithologic traps are developed in the northwestern part of the basin affected by the strike-slip faults along Murray Ridge.Furthermore,the Cretaceous and Paleocene–Eocene source rocks are thick and are slightly affected by volcanic activities.Therefore,it can be inferred that the northwestern part of Offshore Indus Basin enjoys good prospects of oil and gas resources.

Application of the monitoring and early warning system for internal solitary waves:Take the second natural gas hydrates production test in the South China Sea as an example

Internal solitary waves(ISWs) contain great energy and have the characteristics of emergency and concealment. To avoid their damage to offshore engineering, a new generation of monitoring and early warning system for ISWs was developed using technologies of double buoys monitoring, intelligent realtime data transmission, and automatic software identification. The system was applied to the second natural gas hydrates(NGHs) production test in the Shenhu Area, South China Sea(SCS) and successfully provided the early warning of ISWs for 173 days(from October 2019 to April 2020). The abrupt changes in the thrust force of the drilling platform under the attack of ISWs were consistent with the early warning information, proving the reliability of this system. A total of 93 ISWs were detected around the drilling platform. Most of them occurred during the spring tides in October–December 2019 and April 2020, while few of them occurred in winter. As suggested by the theoretical model, the full-depth structure of ISWs was a typical current profile of mode-1, and the velocities of wave-induced currents can reach 80 cm/s and30 cm/s, respectively, in the upper ocean and near the seabed. The ISWs may be primarily generated from the interactions between the topography and semidiurnal tides in the Luzon Strait, and then propagate westward to the drilling platform. This study could serve as an important reference for the early warning of ISWs for offshore engineering construction in the future.

Application of wellhead suction anchor technology in the second production test of natural gas hydrates in the South China Sea

Traditional suction anchor technology is mainly used in the fields of subsea structure bearing foundations,single-point mooring systems and offshore wind power.It is characterized by providing sufficient lateral and vertical bearing capacities and lateral bending moment.The anchor structure of a traditional suction anchor structure is improved with wellhead suction anchor technology,where a central pipe is added as a channel for drilling and completion operations.To solve the technical problems of a low wellhead bearing capacity,shallow built-up depth,and limited application of conductor jetting in the second production test of natural gas hydrates(NGHs)in the South China Sea(SCS),the China Geological Survey(CGS)took the lead in independently designing and manufacturing a wellhead suction anchor,which fulfilled the requirements of the production test.This novel anchor was successfully implemented in the second production test for the first time,providing a stable wellhead foundation for the success of the second production test of NGHs in the SCS.

Distributed optical fiber acoustic sensor for in situ monitoring of marine natural gas hydrates production for the first time in the Shenhu Area,China

The distributed acoustic sensor(DAS)uses a single optical cable as the sensing unit,which can capture the acoustic and vibration signals along the optical cable in real-time.So it is suitable for monitoring downhole production activities in the process of oil and gas development.The authors applied the DAS system in a gas production well in the South China Sea for in situ monitoring of the whole wellbore for the first time and obtained the distributed acoustic signals along the whole wellbore.These signals can clearly distinguish the vertical section,curve section,and horizontal production section.The collected acoustic signal with the frequency of approximately 50 Hz caused by the electric submersible pump exhibit a signal-to-noise ratio higher than 27 dB.By analyzing the acoustic signals in the production section,it can be located the layers with high gas production rates.Once an accurate physical model is built in the future,the gas production profile will be obtained.In addition,the DAS system can track the trajectory of downhole tools in the wellbore to guide the operation.Through the velocity analysis of the typical signals,the type of fluids in the wellbore can be distinguished.The successful application of the system provides a promising whole wellbore acoustic monitoring tool for the production of marine gas hydrate,with a good application prospect.

The Value Constrained Production Decline Model and Its Application in Reserve Valuation

In the asset valuation of oil and gas reserves, it is discovered that the production decline trend of wells is not very obvious and that it is hard to make a production forecast matching the production history, thus resulting in a significant deviation of oil and gas asset value. For production with a significant fluctuation, the value deviation is also considerable if the matching production, which is predicted with classical decline methods, cannot appropriately reflect the time value distribution of actual production. To mitigate such a deviation, a concept is proposed concerning the value constrained production forecast and the value constrained production decline model is developed. A field case is demonstrated as an application of such a model. The model can significantly decrease the risk in the value deviation of a production decline analysis and be applied to the production forecasts for a single well, well clusters, blocks or field scale, and even for other mining industries.

Nuclear magnetic resonance study of the formation and dissociation process of nature gas hydrate in sandstone

In this work,the authors monitored the formation and dissociation process of methane hydrate in four different rock core samples through nuclear magnetic resonance(NMR)relaxation time(T_(2))and 2D imaging measurement.The result shows that the intensity of T_(2) spectra and magnetic resonance imaging(MRI)signals gradually decreases in the hydrate formation process,and at the same time,the T_(2) spectra move toward the left domain as the growth of hydrate in the pores of the sample accelerates the decay rate.The hydrate grows and dissociates preferentially in the purer sandstone samples with larger pore size and higher porosity.Significantly,for the sample with lower porosity and higher argillaceous content,the intensity of the T_(2) spectra also shows a trend of a great decrease in the hydrate formation process,which means that high-saturation gas hydrate can also be formed in the sample with higher argillaceous content.The changes in MRI of the sample in the process show that the formation and dissociation of methane hydrate can reshape the distribution of water in the pores.

All-Electric Subsea Control Systems and the Effects on Subsea Manifold Valves

Subsea development is moving constantly toward simplification,digitalization,and cost-out strategies because the exploration and production of hydrocarbons are moving toward deeper and remote sea water areas.Usage of all-electric subsea technology instead of hydraulic technology is growing and will be the future of subsea systems due to the former’s environmental and functional advantages and reduced costs.The benefits of all-electric subsea systems are health,safety,and environment(HSE)and improved reliability,flexibility,and functionality compared with traditional hydraulic-electrical systems.Existing electrohydraulic technology for a typical subsea system,hydraulic and electric actuators,and subsea manifold valves including valve types and selection philosophy have been reviewed in this paper.Some major worldwide oil companies such as Equinor and Schlumberger have successful experiences with subsea electric actuators.Considering the benefits of all-electric technology especially in terms of cost and HSE,as well as successful experiences of two major oil companies,further research in this area is warranted.One of the gaps in existing reviewed literature is the effect of using all-electric actuators for manifold valves.Thus,three main questions related to electric actuator selection,requirement of safety integrity level(SIL),and effect of using electric actuators on manifold valve selection have been addressed and answered.Forty hydraulic actuated manifold valves from nine past subsea projects in different parts of the world,mainly Africa and Australia,have been selected for the analysis of all-electric actuators.Results show that 93%of the valves require spring-return electric actuators,whereas 7%can be operated with conventional electric actuators without any spring.The manifold valves do not require SIL certification because they are not connected to an emergency shut down system.Introducing the electric actuators to the manifold valve will not change the valve selection philosophy.

Experimental investigation of hydrate formation in water-dominated pipeline and its influential factors

Blockage in water-dominated flow pipelines due to hydrate reformation has been suggested as a potential safety issue during the hydrate production.In this work,flow velocity-dependent hydrate formation features are investigated in a fluid circulation system with a total length of 39 m.A 9-m section pipe is transparent consisted of two complete rectangular loops.By means of pressurization with gas-saturated water,the system can gradually reach the equilibrium conditions.The result shows that the hydrates are delayed to appear as floccules or thin films covering the methane bubbles.When the circulation velocity is below 750 rpm,hydrate is finally deposited as a“hydrate bed”at upmost of inner wall,narrowing the flow channel of the pipeline.Nevertheless,no plugging is observed during all the experimental runs.The five stages of hydrate deposition are proposed based on the experimental results.It is also revealed that a higher driving pressure is needed at a lower flow rate.The driving force of hydrate formation from gas and water obtained by melting hydrate is higher than that from fresh water with no previous hydrate history.The authors hope that this work will be beneficial for the flow assurance of the following oceanic field hydrate recovery trials.

中国海油海上油田采油工程技术进展与展望

针对海上油田面临的油气开采技术难度大、重大技术迭代慢、大型作业技术应用成本高等多方面的挑战,中国海油经过数十年的发展,从稳产上产、技术迭代和降本增效等3方面推动技术变革,逐步形成了以“两提一降”为主线的数智化精细注水和稳油控水、大井距高强度稠油热采、低渗储层改造等三大工程技术,以及机采井延寿降耗、低产低效井增产、大修井作业、提高采收率等四类技术。提出了采油工程技术发展的10条技术路线,加快构建海上低成本采油工程技术体系,为推进中国海上油田采油工程技术高质量发展提供支撑。

基于PDCA循环的海外油田采油工程方案质量创新管理与实践

海外油田开发方案是石油公司发展战略的重要组成部分,是油田开发工作的纲领和指南。海外油田采油工程方案在开发方案中起着承上启下的重要作用,是实现海外油田高产稳产的关键所在,也是实现油田有效开发管理和科学化的前提所在。海外油气开发项目合同模式、合作方式、开发时效性、项目经济性等独有的特点,决定了海外油气田勘探开发不能照搬国内已有的模式,必须开拓创新,形成一套适合海外油气特点、具有中国石油公司特色的方案设计方法。基于PDCA循环,通过全过程控制对海外油田采油工程方案编制模式进行创新管理,有效提高方案编制水平,科学指导海外油田建设,增强国际竞争能力。

海上特稠油热采SAGD技术方案设计

辅助重力泄油(SAGD)技术是近年来特稠油高效开发的新技术之一,复杂的海上环境对该技术的应用提出更大挑战。结合国内外SAGD技术的开发经验和渤海旅大特稠油油藏实际情况,从注汽工艺、采油工艺和地面工程进行分析,确定了SAGD开发过程:预热、降压和SAGD操作;优化了不同阶段的注汽和举升工艺,注汽井采用同心双管均匀注汽,降压阶段采用气举,SAGD操作阶段采用高温电泵生产;地面采用小型化、橇装化的热采设备,并对其地面流程进行优化。总体论证了SAGD技术在该油田的可实施性,为海上油田进行SAGD先导性试验提供了理论依据和技术支持。

空间随机场模型的建立与桩基竖向承载力的可靠度分析

为了研究桩基础的可靠度设计方法,搜集和整理了大量的海洋土钻孔资料,开发了用于地基可靠度分析的数据库系统。利用数据库强大的数理统计功能建立起土性剖面的空间随机场模型,进而将随机场理论与可靠度理论相结合,对渤海海域中海工结构物桩基础的稳定性进行了可靠度分析,详细阐述了各个设计指标的变化对分项系数及可靠度指标的影响规律,并对各指标的灵敏度进行比较分析。结果表明,在各个设计参数中厚土层的强度指标以及设计荷载是2个重要的参数,在渤海海域中应用API标准 (美国桩基规范) 中规定的荷载抗力系数进行设计是安全可靠的。

基于OBE理念的《海洋采油气工程》课程改革实践

针对《海洋采油气工程》教学过程中,学生学习积极性不强,课程教学目标的达成度不高,教学效果还不够理想等问题,提出了基于OBE理念的教学模式改革。通过探索实施混合式教学模式、建立立体化的优质工程教学资源、进行课内外一体化设计、开发与专业紧密联系的创新性实验项目。教学实践表明,改革促使学生成为了课堂的主体,有效激发了学生的学习兴趣,海洋采油气工程学习效果明显提升。

矿物绝缘电伴热在海洋石油工程中的应用设计

目前在海洋工程领域通常使用的电伴热产品对在要求高功率输出和适应极端恶劣工况环境方面还有不足,而矿物绝缘(MI)电伴热在尼克森油砂项目中广泛应用,在-40℃的极端低温和高腐蚀性环境中发挥了其优异的性能,为要求高功率输出和适应极端恶劣工况环境的海洋工程领域的电伴热的应用提供了思路。研究了MI电伴热在海洋石油工程中应用的可行性,从主要产品的类型特点、工作原理、使用范围、选型设计、安装应用等方面做了简单介绍。

我国海洋深水油气田开发工程技术研究进展

分析了中国海洋深水油气田开发工程技术与国外的差距,详细论述了“十一五”至“十三五”期间国家科技重大专项“海洋深水油气田开发工程技术”项目所取得的重大研究进展。具体体现在:构建了1500 m深水油气田开发工程设计技术体系,基本具备了1500 m深水油气田开发工程设计能力,相关研究成果已在荔湾3-1气田群、流花16-2油田群和陵水17-2深水气田等工程项目中得到成功应用;构建了4大类共16项深水工程实验系统,形成了国内深水工程实验技术及实验体系,为相关深水工程技术研究、设备研发等提供了实验手段;自主研制了一批1500 m水深的水下关键设备和产品,其中深水保温输送软管、深水水下管汇、水下多相流量计等高端产品和设备已初步实现了国产化应用;自主研制的4类深水工程设施监测系统已部分应用于现场监测。相关研究成果带动了我国海洋石油设备制造能力由陆地向海洋、由浅水向深水的跨越式发展。最后结合我国南海及海外深水油气田开发的实际需求,对我国海洋深水油气田开发工程技术的未来研究及发展方向提出了具体建议。

国家科技重大专项支撑中国海油增储上产

海洋石油工业具有高技术、高投入、高风险"三高"特点,这决定了在海洋油气资源勘探开采过程中必须要不断进行理论技术创新和实践,实现海洋油气资源的高效、安全合理开发利用。中国海油以国家科技重大专项为依托,"产学研用"相结合,通过联合攻关,在海洋油气勘探、开发、钻采、工程建设等方面取得了丰硕的理论认识创新、技术进步和实践成果。建立并完善了中国近海深层湖相烃源岩大规模生气和成藏理论、近海高温高压天然气成藏理论、近海新近系岩性油气藏成藏理论、盆地边缘富烃凹陷形成机制地质认识,形成了适用于近海独特地质条件的高效地震勘探配套技术,推动了中国海域渤中19-6、垦利6-1、惠州26-6等26个大中型油气田的发现;形成并丰富了海上常规稠油水驱综合调整及高效开发钻采技术、非常规稠油多轮次吞吐与规模化热采配套技术、海上油田化学驱技术,大幅提高了海上油田开发采油速度和采收率;攻克海上高温高压钻井难题,促成中国海上最大高温高压气田东方13-2成功投产;形成了具有自主知识产权的深水油气开发工程技术体系及深水工程实验技术体系,建成流花油田群示范工程,自主设计建造了世界首个带凝析油储存功能的深水半潜式平台"深海一号"。以部分典型案例为代表,论述国家科技重大专项成果为中国海油增储上产起到了支撑作用。

海洋油气田水下设施的防渔业损坏

为保障海洋油气开采的安全和顺利,文章以我国南海东部海域为例,在概述渔场和渔船基本情况的基础上,分析拖网对海洋油气田水下设施可能造成的损坏,并提出相关建议。研究结果表明:对海洋油气田水下设施影响最大的捕捞作业方式是拖网;双拖网渔船产生的最大拖曳力远大于脐带缆所能承受的最大拉力,很有可能损坏脐带缆等水下设施;应对渔船作业水域的海洋油气田水下设施采取保护措施,限制可能损坏水下设施的渔船作业,加强管理和培训以及通过技术手段对相关情况进行监测和处理。