Deepwater oil and gas field development in South China Sea

This paper focuses on potential development models of future oil and gas exploration in South China Sea. A detailed study of current development models worldwide is performed through some examples of industry installed/ongoing projects and major technical issues encountered during these practice. Key technologies are discussed for the success of field development. Some of the technologies and field development experience can be used for South China Sea project. Several models are studied in field development for different scenarios,including marginal field,large oil field and gas field. With the massive investment activities,continued improved technologies,and rapidly growing pool of professionals,the offshore industry in China will soon encounter a golden period.

Application of Tension Leg Platform Combined with Other Systemsin the Development of China Deepwater Oil Fields

The development of deepwater oil fields has reached a new stage with the dramatic increase in water depth and the recent increasing demands of the economic development in the filed. The use of a Tension Leg Platform （TIP） combined with other systems, such as Floating Production Storage and Offloading （FPSO） system, Floating Production Unit （FPU） system, Tender Assisted Drilling （TAD） system, etc., has drawn the industry attention and increased significantly in the past few years. For the areas lacking of pipeline system, the use of TIP（s） combined with FPSO has been chosen to efficiently develop the deepwater fields. The TIP with a Tender Assisted Drilling system significantly reduces the payload of the platform and reduces the investment in the TIP system substantially. This opens the door for many new deepwater field developments to use the tension leg platform. The advantage of the TIP combined with a TAD system is more significant when several TIPs are used for the continuous development of the field. One of the applications for the TIP with a tender assisted drilling system can be in the development of an offshore marginal field. Owing to the increase of water depth, the conventional fixed platform model for the exploration of those fields becomes uneconomical. It also would be too expensive to use a large TIP structure for those marginal fields due to the large amount of initial investment. The TIP system with tender assisted drilling can be used to develop those fields economically. There are many marginal fields in China offshore, especially in shelf areas. The application of this field developing model, combined with the existing field developing experience in China, will open the door for many marginal field developments. This paper will review the application of the combined TIP system through some examples of completed/ongoing projects, and major technical issues encountered in those practices. The potential application of this technology in China deepwater development will be discussed in the end.

Floating Production Platforms and their Applications in the Development of Oil and Gas Fields in the South China Sea

This paper studies the current available options for floating production platforms in developing deepwater oil fields and the potential development models of future oil and gas exploration in the South China Sea. A detailed review of current deepwater platforms worldwide was performed through the examples of industry projects, and the pros and cons of each platform are discussed. Four types of platforms are currently used for the deepwater development: tension leg platform, Spar, semi-submersible platform, and the floating production system offloading. Among these, the TLP and Spar can be used for dry tree applications, and have gained popularity in recent years. The dry tree application enables the extension of the drilling application for fixed platforms into floating systems, and greatly reduces the cost and complexity of the subsea operation. Newly built wet tree semi-submersible production platforms for ultra deepwater are also getting their application, mainly due to the much needed payload for deepwater making the conversion of the old drilling semi-submersible platforms impossible. These platforms have been used in different fields around the world for different environments; each has its own advantages and disadvantages. There are many challenges with the successful use of these floating platforms. A lot of lessons have been learned and extensive experience accumulated through the many project applications. Key technologies are being reviewed for the successful use of floating platforms for field development, and potential future development needs are being discussed. Some of the technologies and experience of platform applications can be well used for the development of the South China Sea oil and gas field.

Water-cut rising mechanism and optimized water injection technology for deepwater turbidite sandstone oilfield: A case study of AKPO Oilfield in Niger Delta Basin, West Africa

Through the analysis of the reservoir connection relationship and the water-cut rising rules after water breakthrough in the highly volatile oil AKPO oilfield, a new model of water-cut rising was established, and the timing and strategy of water injection were put forward. The water-cut rising shapes of producers after water breakthrough can be divided into three types, and their water-cut rising mechanism is mainly controlled by reservoir connectivity. For the producers which directly connect with injectors in the single-phase sand body of the single-phase channel or lobe with good reservoir connectivity, the water-cut rising curve is "sub-convex". For the producers which connect with injectors through sand bodies developed in multi-phases with good inner sand connectivity but poorer physical property and connectivity at the overlapping parts of sands, the response to water injection is slow and the water-cut rising curve is "sub-concave". For the producers which connect with injectors through multi-phase sand bodies with reservoir physical properties, connectivity in between the former two and characteristics of both direct connection and overlapping connection, the response to water injection is slightly slower and the water-cut rising curve is "sub-S". Based on ratio relationship of oil and water relative permeability, a new model of water cut rising was established. Through the fitting analysis of actual production data, the optimal timing and corresponding technology for water injection after water breakthrough were put forward. Composite channel and lobe reservoirs can adopt water injection strategies concentrating on improving the vertical sweep efficiency and areal sweep efficiency respectively. This technology has worked well in the AKPO oilfield and can guide the development of similar oilfields.

Modeling underwater transport of oil spilled from deepwater area in the South China Sea

Based on a Lagrangian integral technique and Lagrangian particle-tracking technique,a numerical model was developed to simulate the underwater transport of oil from a deepwater spill. This model comprises two submodels: a plume dynamics model and an advection-diffusion model. The former is used to simulate the stages dominated by the initial jet momentum and plume buoyancy of the spilled oil,while the latter is used to simulate the stage dominated by the ambient current and turbulence. The model validity was verified through comparisons of the model predictions with experimental data from several laboratory flume experiments and a field experiment. To demonstrate the capability of the model further,it was applied to the simulation of a hypothetical oil spill occurring at the seabed of a deepwater oil/gas field in the South China Sea. The results of the simulation would be useful for contingency planning with regard to the emergency response to an underwater oil spill.

深水固井循环阶段井筒温度场预测模型研究

准确预测固井循环阶段井筒温度场有助于水泥浆性能参数的设计和井筒压力的计算,为此,基于井筒流动机理和传热学理论,考虑不同区域差异对传热过程的影响和不同流体热力学参数差异及其随井深变化的特点,结合流体界面位置描述方程,建立了适用于深水固井循环阶段的井筒温度场预测模型。利用2口井的实测数据对模型进行了验证,并进行了关键因素的影响规律分析。结果表明:注入水泥浆之前,钻井液应循环2~4周,以降低注入过程中循环时间改变对井底循环温度的影响;注入水泥浆过程中,排量越大,周围环境的升温或降温作用越不明显;计算过程中,若不考虑温度对比热容的影响,则预测的井底循环温度会偏高2~4℃;水泥浆密度对温度的影响规律与传热方向有关。研究结果对深水固井具有一定的指导作用。

冲喷式柔性管缆挖沟机在海底管缆铺设挖沟施工中的应用

深水水下管缆的铺设是开发深水油气资源的关键施工作业项目。深水水下挖沟作业具有技术难度大、施工复杂、投资巨大等特点。在深水海域油气开发工程中冲喷式柔性管缆挖沟机应用广泛,因此对其产品性能、实际深水功能测试、挖沟作业工序、挖沟沟型、挖沟效果等关键技术问题进行分析,经过实践验证,该设备能够独立完成千米级深水域水下挖沟施工。

中海油陵水气田首台高压收球筒分析设计

在石油运输管道建设与维护中,清管作业十分关键。收球筒是管道清管作业中必不可少的设备,其壳体接管开孔区域是承压薄弱部位,最易发生破坏。采用ANSYS17.0有限元分析软件,根据收球筒的主要设计条件和结构参数,按照JB 4732—1995 《钢制压力容器——分析设计标准(2005年确认)》的规定,对中海油陵水气田首台高压收球筒壳体多个开孔区域的主要受压元件进行应力分析与强度评定。结果表明,分析设计的高压收球筒满足应力强度评定要求,符合工程项目验收条件。

深水气田开发清井返排水合物风险评估与防控

针对海上深水气井清井返排过程中,生产系统在泥线附近易形成水合物影响正常生产问题。以海上深水气井气藏地质、工程及井内产出流体组分数据和环境参数为模拟条件,基于P-R状态方程、多相流理论,运用OLGA软件建立热力水力学模型,对高产气井在清井返排过程中水合物生成条件及防控进行了研究。研究结果表明:在750 m的深水条件下气井在清井返排过程中,均有水合物生成风险,泥线至平台管段是水合物生成的高风险段;气井产量越高越有利于防止水合物生成;当以不同产量稳产后关井,很快在泥线附近形成水合物,约1 h后,泥线温度降至环境温度;不同阶段、不同含水率时以不同速率注入甲醇(水合物抑制剂)可有效防止水合物生成。

An Installation System of Deepwater Risers by An S-Lay Vessel

Along with the consumption increase of the petroleum products, more countries have transferred their attentions to the offshore fields, especially the deepwater oil and gas reserves. For deepwater exploitation, the risers must be installed to act as the conduits connecting surface platforms to subsea facilities. In this paper, the typical risers sorted by different classes are introduced, and the correspondent installation methods are presented. By investigating the recent projects performed in the deepwater hot spots, and combining the challenges of HYSY20 l for riser installation, a lifting device developed for assisting riser installation is proposed and detailed to satisfy the installation of deepwater risers in the LW3-1 Gas Field of 1500 m in the South China Sea. Tests on both the functions and performances of such a new system exhibit the satisfaction of meeting all challenging requirements of HYSY201 for application to riser installation in waters up to a depth of 3000 m in the South China Sea.

New technology opens the door for deepwater development

The paper provided an updated status of technology for deepwater field development, demonstrated the importance of its application through actual project example, and discussed some future technical development trends. The focus was on the floating structures. By reviewing some of the engineering aspects of the project, the technology advancement, innovations and challenges in offshore engineering were discussed and demonstrated. The author’s view of technical challenges facing deepwater forwarding was discussed, which covered water depth limitations, new material application, installation methods, riser development and operational issues. An overview of technologies that will enable deepwater projects to be extended into new frontiers was presented.

全球深水油气开发特征、潜力分布及发展趋势

全球深水油气田主要分布在中—南大西洋两岸、墨西哥湾、东非海上、东地中海、黑海、南里海、澳大利亚西北陆架七大海域,中—南大西洋两岸海域深水油气技术剩余可采储量和产量占全球比例均为50%左右。近几年,澳大利亚西北陆架海域中深水油气产量增速较快,中低经济性和待获得开发许可的油气田储量最多。全球深水油气发展历经3个发展阶段,主要以衰竭式开发方式为主。深水油气具有高成本、高收益特征,七大国际石油公司纷纷将深水油气作为主要投资领域。对于油公司来说,迈向深水领域是必由之路。建议我国石油公司积极获取规模优质的深水油气资产,与国际大石油公司开展合作,共享勘探开发经验,发挥一体化优势,做好深水油气作业能力体系建设。

深水高温高压气田双层套管射孔技术可行性模拟试验

陵水25-1气田天然气资源丰富,该区块深水、高温、高压并存,完井作业难度大,若采用单层套管射孔完井,不能保障所有气组高效开采,亟需开展双层套管射孔工艺专项技术攻关。双层套管射孔技术可行性模拟试验设计通过高温高压双层套管穿透性能简化试验和常温常压双层套管射孔地面全尺寸试验两部分进行测试和验证射孔作业相关参数。基于高温高压工况双层套管射孔模拟试验,确定了高温高压对射孔孔径和孔眼深度的影响规律,获得了高温高压工况下孔深的折减系数;基于双层套管射孔地面全尺寸模拟试验,研究了不同工况下射孔穿透性规律,建立了炸药量与穿深/孔径的量化关系,并进行了射孔孔径差异影响因素的量化分析。通过高温高压折减系数,分析了双层套管射孔效率量化影响规律,模拟试验证明了双层套管射孔的可行性,对陵水25-1气田高效开采具有借鉴意义。

深水气田疏松砂岩储层出砂机理研究

在深水油气开采过程中,储层出砂已成为影响油气井正常生产的重要问题,特别是深水气田高产气井中过高的生产速率提高了砂粒的运移能力。利用现场取心完成出砂临界流速试验,并基于流固耦合理论建立了考虑渗流-应力全耦合和气田砂粒侵蚀准则的高压气井出砂定量预测模型,结合自适应网格技术分析不同岩石强度参数和生产参数下深水气井开采过程中的出砂情况。分析结果表明:储层破坏首发点在最小主应力方向,且在地应力和拖曳力的协同作用下不断向井口内部突进;地层黏聚力和生产压差对储层出砂影响较大,其主要影响近井筒地带储层的塑性变形及塑性区内流体的流动特性,进而影响储层的出砂量;对于目标开采储层需采取有效的防砂工艺,并精确控制生产压差来降低出砂风险,或将出砂率控制在可控水平进行开采作业。所得结论可为高产气井的防砂增产提供参考。

外夹式超声波流量计在深水油气田中的应用

随着海洋油气开发不断向深水方向发展,长距离管道输送的要求越来越高,伴随着高压力、长距离的药剂计量,给深水油气田开发与设计带来了相关问题。基于南海某深水油气田开发对长距离药剂输送计量所选用的外夹式流量计作为研究,为从根本发挥外夹式超声波流量计作用,本文以其概述为基础,针对其优点与缺点展开详细分析,提出其在实际应用中的选型及应用环境。最后指明安装及注意事项,对后期的深水油气田开发设计提供参考。

Reservoir forming conditions and key exploration technologies of Lingshui 17-2 giant gas field in deepwater area of Qiongdongnan Basin

On September 15,2014,China National Offshore Oil Co.,Ltd announced that a high production of oil and gas flow of 1.6
106 m3/d was obtained in Well LS17-2-1 in deepwater area in northern South China Sea,which is the first great oil and gas discovery for self-run deepwater exploration in China sea areas,and a strategic breakthrough was made in natural gas exploration in deepwater area of Lingshui sag in Qiongdongnan Basin.Under the combined action of climax of international deepwater exploration,high oil prices,national demands of China,practical needs of exploration,breakthroughs in seismic exploration and testing technologies,innovations in geological cognition and breakthroughs in deepwater operation equipment,Lingshui 17-2 gas field is discovered.Among these factors,the innovation in reservoir forming geological cognition directly promotes the discovery.The quality of seismic data in the early time is poor,so key reservoir forming conditions such as effective source rocks,high quality reservoirs and oil-gas migration pathways are unable to be ascertained;with support of new seismic acquisition and processing technology,some researches show that Lingshui sag is a successive large and deep sag with an area of 5000 km2 and the maximum thickness of Cenozoic stratum of 13 km.In the Early Oligocene,the Lingshui sag was a semi-closed delta-estuarine environment,where the coalmeasure and marine mudstones in Lower Oligocene Yacheng Formation were developed.The Lingshui sag is a sag with high temperature,and the bottom temperature of source rocks in Yacheng Formation can exceed 250C,but the simulation experiment of hydrocarbon generation at high temperature indicates that the main part of this set of source rock is still in the gas-generation window,with resources of nearly 1 trillion cubic meters,so the Lingshui sag is a hydrocarbon-rich generation sag.In the Neogene,the axial canyon channel from the Thu Bon River in Vietnam passed through the Lingshui sag,and five stages of secondary channels were developed in the axial canyon channel,where four types of reservoirs with excellent physical properties including the axial sand,lateral accretion sand,natural levee sand as well as erosion residual sand were developed,and lithologic traps or structural-lithologic traps were formed.The diapiric zone in the southern Lingshui sag connects deep source rocks in Yacheng Formation and shallow sandstones in the channels,and the migration pattern of natural gas is a T-type migration pattern,in other words,the natural gas generated from Yacheng Formation migrates vertically to the interior of the channel sandbody,and then migrates laterally in the channel reservoirs and forms the reservoirs.Innovations of geophysical exploration technologies for complicated geological conditions of deepwater areas are made,such as the detuning comprehensive quantitative amplitude hydrocarbon detection technology,which greatly improves the success rate of deepwater exploration;key technologies of deepwater safety exploratory well testing represented by the platform-dragged riser displacement technology are developed,which greatly reduces the drilling test cost.The above key exploration technologies provide a strong guarantee for the efficient exploration and development of Lingshui gas field.

深水气田井流物净化研究与实践

南海荔湾区块深水气田采用水下采输系统,井流物从水下井口产出后与水合物抑制剂、各类化学药剂掺混形成复杂组合流体。生产运行中发现井流物中不溶物和悬浮固体含量增加,洁净度下降,流程中各类滤器频繁发生堵塞。通过化验分析和电镜扫描对比,明确了井流物杂质成分为乙二醇再生单元中颗粒过滤器的助滤剂硅藻土以及处理设备中的腐蚀产物。由于助滤剂的强吸附性,使杂质吸附了大量重烃组分,成分更加复杂,同时在海管段塞作用下不断富集加强,井流物成分均质性不断遭到破坏,加剧了工艺处理的难度。针对上述问题,将颗粒过滤器滤布规格由35L/(m^(2)·s)提高至21L/(m^(2)·s),控制助滤剂漏失量,同时持续投用脱盐闪蒸单元抑制系统腐蚀问题,有效降低井流物杂质含量,提升了系统洁净度。另外,采用精细控压携液策略,抑制深水海管井流物段塞的形成。

Risk Identification and Mitigation Strategies for Deepwater Oilfields Development

Deepwater oilfields will become main sources of the world's oil and gas production.It is characterized with high technology,huge investment,long duration,high risk and high profit.It is a huge system project,including exploration and appraising,field development plan(FDP)design,implementation,reservoir management and optimization.Actually,limited data,international environment and oil price will cause much uncertainty for FDP design and production management.Any unreasonable decision will cause huge loss.Thus,risk foreseeing and mitigation strategies become more important.This paper takes AKPO and EGINA as examples to analyze the main uncertainties,proposes mitigation strategies,and provides valuable experiences for the other deepwater oilfields development.

气液混输管道清管球运行速度控制方法研究与实践

在深水天然气的开采过程中,一般采用水下生产系统+深水海管+浅水固定平台/浮式平台+浅水海管+陆地终端的模式进行开采。为了提高海底管线的输送效率和运行安全,需要定期对管道进行清管作业,而管道末端清管球的运行速度的合理控制对平台的工艺稳定起着决定性的作用。某深水天然气开采平台对现有的工艺流程进行了详细的分析和研究,设计了一套“三先三后”清管球运行速度控制方法。该方法涉及通球全过程,可有效预防清管作业带来的段塞、气荒等异常工况,并解决液位超高、凝析油品质下降、滤器堵塞、控制节点过多等问题。清管球在管道末端运行速度控制在0.76 m/s,来液得到有效控制和稳定处理,每次作业可产生经济效益56万元。

深水钻探井筒温度场的计算与分析

通过对海水温度数据回归分析,得到了南海海水温度场随深度的分布。以传热学基本理论为基础,通过理论推导,得到了循环及停止循环条件下的深水钻探井筒温度场理论计算公式。计算结果表明,循环钻进期间,要维持隔水管内的温度,应保证隔水管的保温层完好,并在满足钻井施工条件下尽量增大循环排量;停止循环时,随着关井时间的增加,井筒内流体温度逐渐接近外界环境温度,为避免在井筒及防喷器处生成大量水合物,关井时间要尽量短。