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25 June 2014, Volume 33 Issue 3 Previous Issue    Next Issue

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China Offshore Oil Recovery Technological Development Strategy Chen Bi, Qiu Zongjie and Xu Wenjiang 2014, 33(3): 1-4.  Abstract ( )   PDF (3853KB) ( )   Offshore oil recovery technological development will bear a direct influence on effective development of China offshore oil reserves and further improvement of the recovery factor of offshore oil and gas fields, following the efforts to infill adjustment wells of offshore oil and gas fields and tap the potential for increase of production through conventional stimulation measures. In the new period of China offshore oil and gas development, the oil recovery technology development pursues a general principle of accelerating the pilot development and attaching importance to concentrated development. Based on the actual conditions, CNOOC comes up with the orientation for oil recovery technological development and work proposals. The pilot technological development includes offshore heavy oil thermal production, development of offshore low-permeability oil and gas reservoirs, chemical flooding stimulation, gas-injection, and microbial enhanced oil production. The orientation for concentration of integrated technology aims mainly at the technological application systems, such as water injection and treatment, ESP process, reservoir protection, well completion and workover, and anti-corrosion, antiscaling and anti-wax process. The efforts will be also focused on some key issues affecting implementation of the strategy, such as talents, technological research and management capability.

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Accelerate Transformation of Production Pattern to Bring About Significant Offshore Oil and Gas Production Growth Zhu Weicheng, Qiu Zongjie, Liu Ming, Quan Yuke, Yao Shuang, Zhan Shengyun and Guan Hongxiang 2014, 33(3): 5-8.  Abstract ( )   PDF (3881KB) ( )   Following successful construction of “Offshore Daqing Oilfield”, China National Offshore Oil Corporation (CNOOC) has come up with an ambitious objective for “second takeoff”, namely building itself into the first-class international energy company in the next 10 to 20 years. According to this article, it is necessary to create new conceptions on oilfield development, such as oil and gas exploration and development integration and full service life, to fulfill the objection for oil and gas production. The efforts should be focused on accelerating transformation of oil and gas development pattern, stepping up management at the grassroots level and basic research, perfecting regional organizations to ensure oil and gas development, creating the preliminary research work style, accelerating development and appraisal of the discovered oilfields, improving producing degree of oil and gas reserves and making technological research on the basis of increasing reserves and production, bringing about significant growth in oil and gas production.

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Development of Clarifiers for Produced Water Used for Offshore Polymer Flooding Oilfields Jing Bo, Zhai Lei, Zhang Jian and Tan Guorong 2014, 33(3): 9-11.  Abstract ( )   PDF (3256KB) ( )   The produced water of polymer flooding contains a large amount of dissolved hydrolyzed polyacrylamide (HPAM). It is difficult to treat HPAM which is a type of polyanion with lots of carboxyl groups. Currently, commercial water clarifiers are mainly polycationic, such as cationic polyacrylamindes, polyaluminum chloride. While attracting the anionic oil drops, the clarifiers can also interact with HPAM in the wastewater, resulting with a large quantity of viscous oil sludge and blocking the production process. To settle this problem, nonionic water clarifiers were synthesized and injected into the produced water from the offshore platform. The results showed the water quality was stabilized after injection and met the requirements on reinjection. The test will be carried out on a larger scale for the purpose to evaluate development of new-type of agents.

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New Method to Test Polymer Concentration in Produced Liquid of Offshore Oilfield Jiang Weidong, Zhang Jian, Xu Wenjiang and Zhu Yuejun 2014, 33(3): 12-15.  Abstract ( )   PDF (4181KB) ( )   Colloid titration method is used to test and analyze polymer concentration in produced liquid of Bohai Oil Field. Based on analysis of colloid titration testing principle, the standard curve is established to give the appropriate conditions for application and compare colloid titration method with starch iodide chromium method and azotification method. The flow back samples from polymer injection wells are brought under inspection both at the laboratory and on the offshore platform for testing of polymer concentration in produced liquid. The results show that colloid titration method can test polymer concentration rapidly and accurately. In addition, formulation of agents is safe and non-toxic in the testing process. The instrument is simple and easy to operate, with a wide range of sample testing. This method can meet the demand for rapid testing of polymer concentration in produced liquid of offshore oilfields.

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Development and Application of Heavy Oil Activating Agent Xu Xiaohui, Zhang Jian, Yang Guang, Shi Xuefeng and Wang Jinben 2014, 33(3): 16-19, 27.  Abstract ( )   PDF (6202KB) ( )   To meet the demand for heavy oil production in Bohai Oilfield, Chemical Research Institute of China’s Academy of Sciences and CNOOC Research Institute jointly developed heavy oil activating agent (ICAJ). As a single chemical agent, ICAJ is simple in formulation process, convenient in use of injection facilities, easy for operation and management, and cost-effective in service and maintenance. The test of its oil displacement ability confirms that ICAJ has a strong affinity of heavy oil and is able to emulsify and disperse heavy oil. The core flooding results show that ICAJ can enlarge swept volume and improve oilwashing efficiency, more appropriate for heavy oil production. The physical simulation experiment indicates that the agent can raise EOR by about 15 percent as compared to water flooding. It can be put into wide application in oilfields.

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Numerical Simulation Study of Factors Influencing Polymer Flooding Injectability He Chunbai, Tang Engao, Xie Xiaoqing, Lin Chunyang and Jiang Shanshan 2014, 33(3): 20-23.  Abstract ( )   PDF (4388KB) ( )   Take a certain oil field in Bohai Sea for instance. The analysis is made on the basis of numerical experiment, studying the five factors influencing single-well polymer flooding injectability, such as formation permeability, formation crude oil viscosity, polymer viscosity, polymer injection rate, and polymer injection time. Then, the functional relationship between the influencing factors and injectability under the conditions of a single factor is acquired from the study. Based on calculation of different influencing elements, the factors influencing polymer flooding injectability are ranked according to the order of importance, with the formula for rapid calculation of the single-well polymer injectability acquired. The formula is tested on the basis of indoor experiment and dynamic analysis. The results show that this formula is simple, workable, accurate and reliable.

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Improve JBN Calculation Method of Oil and Water Two-phase Permeability of Water Sensitive Low-permeability Reservoirs Ma Shigang 2014, 33(3): 24-27.  Abstract ( )   PDF (4673KB) ( )   When the water sensitive low-permeability sandstone reservoir comes under the water-flooding process, abnormal injection pressure may appear owing to water sensitive influence, such as expansion of clay, migration of particles and plugging. Therefore, adoption of conventional JBN method to calculate oil and water two-phase permeability may lead to abnormal phase permeability curve. On the condition that water-sensitive influence is taken into account in the waterflooding process of water-sensitive low-permeability sandstone reservoir, improvement is made on the conventional JBN interpretation method to meet the demand for correct interpretation of oil and gas water two-phase permeability of watersensitive low-permeability sandstone reservoir. Actual application confirms correctness and feasibility of the improved method.

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Detailed Management of Offshore Gas Fields Li Yubin 2014, 33(3): 28-31.  Abstract ( )   PDF (3913KB) ( )   Detailed management is a managerial pattern characterized in management on a scientific basis and operation in details, aiming at reduction of corporate operating cost and improvement of work efficiency. The conception of detailed management has been actively put into practice for Dongfang 1-1 Gas Field since it was put into production. A tailored management pattern has been established for the gas field, including detailed safety management, detailed production management, detailed personnel training management, detailed equipment maintaining management, and detailed cost control. Based on detailed management, the gas field has made remarkable achievements in safety management, production management, equipment management, personnel management and cost control. Such management pattern and conception can be promoted and used for offshore oil and gas fields.

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Risk Assessment and Maintenance Cost Optimization of Undersea Oil and Gas Wei Li 2014, 33(3): 32-36.  Abstract ( )   PDF (4807KB) ( )   It is more and more important to make analysis and study of the relations between risk assessment of pipelines and maintenance cost thanks to the current stern situation in safety of oil and gas pipelines. It is of great urgency to establish an assessment and management system for integrity of undersea oil and gas pipelines to ensure safety of operation and minimize the possibility for accidents. This article makes briefings about the basic conceptions of risk assessment, elaborates the implementation process for risk assessment, lists the matrix table for judgment of the risks through quantitative calculation of the failure risks, and draws the conclusion that purposely cost management can effectively lower the cost for operation and maintenance of pipelines. Optimization of pipeline operation and maintenance aims at maximize the safety of pipelines at the possible lowest cost. The trend and distribution of cost for pipeline operation and maintenance are listed in the form of risk assessment cost table. Managers can make operation and maintenance of pipelines cost-effective on the basis of the table.

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Make Technological Breakthrough in Effective Development of Offshore Low Permeability Oil FieldsPipelines Xu Wenjiang 2014, 33(3): 37-40.  Abstract ( )   PDF (3982KB) ( )   This article makes briefings about a series of research on how to make technological breakthrough in effective development of offshore low-permeability oil fields so as to settle the contradiction between “development on the basis of a few wells” and “establishment of effective production and injection pattern,” the contradiction between “high-efficiency production” and “low degree of spread” and the contradiction between “high-speed development” and “injection-production imbalance.” Based on theoretical analysis and laboratory experiment, the method for making technological breakthrough for effective development is brought under a systematic study, thus proposing to implement effective injection and production, keep energy continually and transform reservoirs effectively for gradual settlement of the above-stated three basic contradictions. A set of methods to make technological breakthrough for effective development of offshore low-permeability oilfields is created, which are of great significance to development of the pilot offshore low-permeability oil fields.

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Study of Flooding Technology for Offshore OilfieldsPipelines Liu Yigang, Xu Wenjiang and Jiang Weidong 2014, 33(3): 41-44.  Abstract ( )   PDF (4267KB) ( )   The offshore sandstone reservoirs of conventional heavy oil in Bohai Bay are strong in heterogeneity and loose in cementation. Long-term water-injecting development has intensified horizontal and vertical heterogeneity of reservoirs, leading to rapid increase of water cut and gradual decrease of production in the oilfield development process. Flooding technology is an important technological process to improve development results of high water-cut oilfields and control water cut for stable oil production. It finds wide application in oilfields. To settle the issues existing in offshore oilfield development, CNOOC has focused on the study and application of various technologies for profile control, water plugging and deep-layer flooding. This article makes briefings about the principles and application of flooding technology, such as weak gel flooding, jelly deep-layer flooding, nanosphere flooding, nitrogen foam pressure cone, and modified heavy oil water plugging. Application of the technology and process has achieved good results for increase of oil production and water-cut control, technologically ensuring high water-cut oilfield development.

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Study of Production Mode for Offshore Low Permeability Thin Interbedded Oil Fields Zhu Weicheng, Zhan Shengyun, Liu Ming and Liu Fan 2014, 33(3): 45-48.  Abstract ( )   PDF (4147KB) ( )   Development of China’s offshore low-permeability oil fields is currently under its preliminary stage. This article makes briefings about the experiment that uses numerical simulation and reservoir engineering method to determine reasonable development horizons, optimize water injection time and improve development results and economic performance of such oil reservoirs. The results indicate that the offshore low-permeability thin interbedded oil reservoirs have a strong heterogeneity. To achieve good water flooding results for low-permeability horizons, the generalized factor should be lower than 5, namely the permeability difference among the horizons should be less than 8 while there are no more than six or seven thin interbeds. As for the company’s special offshore oilfields, the water flooding project should be preferably initiated as soon as they are put into production

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Keep Energy for Development of Offshore Low Permeability Oil Reservoirs Tan Xianhong 2014, 33(3): 49-52, 61.  Abstract ( )   PDF (5346KB) ( )   To settle the contradiction between “high-efficiency development” and “injection and production imbalance” that appears in the development process of offshore low-permeability oilfields, the study selects a number of controllable factors, including low-limit design of controlling targets, high-limit design of controlling targets and design of water quality target. The prediction is also made of the changes in water absorption capability. The results show that effective water injection for maintenance of formation energy is related to the geological conditions of oil reservoir, water quality control, water injector type, injection and production well pattern, and well completion design. Based on design and analysis, it is assumed that three methods can be used to keep the energy of offshore low-permeability oil reservoirs: use of horizontal wells for water injection to increase the length of water-injecting wellbore for a higher amount of injected water, multi-staged fracturing of water injectors to increase the flow area for a higher water-injecting amount, and adjustment of injection-production well pattern to increase water injectors for more water injection.

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Method for Improving Economic Performance of Offshore Heavy Oil Thermal Wei Li and Xu Wenjiang 2014, 33(3): 53-57.  Abstract ( )   PDF (5190KB) ( )   It is necessary to combine business conceptions with technological application for development of offshore low-grade oil reservoirs. Taking Nanpu 35-2 Oilfield for instance, the profit-loss balance curve analysis method is used to analyze economic performance of offshore heavy oil thermal production. Based on the results from the first round of thermal production in the testing zone of Nanpu 35-2 Oilfield, the production of most wells are only close to the profit-loss balance curve of economic development (IRR=12%, NPV=0), when the investment for platform engineering and drilling of modular rig are taken into account. On the condition that the investment for platform engineering is not taken into account, the output of all thermal production wells is above the profit-loss balance curve for economically-effective development following the first round of thermal recovery. If the oilfield has some advantageous conditions and the follow-up thermal production wells no longer share the engineering investment, the existing technology can meet the demand for economic development. The profit-loss balance curve method is recommended for reference. Namely, the stimulation operation can be used to keep economic performance of thermal production wells when the output of producing wells is below the profit-loss balance curve. Key words:

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New-type Downhole Oil-water Separation and Re-injection Process of Offshore Oilfield Wang Sheng, Liu Min, Luo Changhua, Zhang Chengfu and Wang Yao 2014, 33(3): 58-61.  Abstract ( )   PDF (4242KB) ( )   When an offshore oilfield enters into its later high water-cut period, it is more and more difficult to lift, store and treat the produced water with the cost on the rise, causing a great pressure on the offshore oil field in the energy saving and pollution-reducing areas. In addition, part of platform facilities cannot satisfy the demand for treatment. CNOOC has developed a new-type downhole oil-water separator and designed the pipe string for the process, thus creating a set of suspending downhole oil-water separation and re-injection process suitable for offshore oilfields. The maximum outer diameter of the new-type oil-water separator is 130mm and the handling capacity reaches 1200 cubic meters per day. The whole process system adopts the suspending three-pass joint device to establish the flow path, ensuring that a large flow channel is established in the wellbore. The downhole parameters monitoring and adjusting facilities can make realtime inspection and adjustment of the entrance pressure of the oil-water separator on the surface to ensure the separation efficiency of the system. With a large handling capacity, this system is compact in structure. The process is similar to the process of the production pipe string of electric submersible pump currently used in offshore oilfields, significantly lowering the risks for operation and service.

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Oil-collecting and Cleaning Technology of Offshore Buffer Tank Zhou Guanghui, Ma Yansong and Zhang Ziyou 2014, 33(3): 62-65.  Abstract ( )   PDF (4019KB) ( )   With the production scale of offshore oil fields expanding, it is increasingly difficult to treat the production water re-injected into the CEP process. When the oil-contaminated water is discharged into the buffer tank, the floating oil is accumulated on the top of the tank with sludge sinking on the bottom. The quality of injected water will become worse and worse if not processed. Based on the on-the-spot investigation of offshore oil fields for many years, Enman Technology (Beijing) Co. Ltd. has independently developed a set of oil-collecting and cleaning device system, which adopts the technology to collect floating oil and the new-type hydraulic jet technology to eliminate sludge. The device can automatically collect oil on the top and eliminate sludge on the bottom at any time. Onshore and offshore application in the past few years confirmed that this system could improve water quality of buffer tank, reduce the work intensity of operators and keep working staff from high-risk service.