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Abstract Jidong is a typical small-complex fault-block reservoir in fault basin of Bohai Bay. On the basis of the fine description of the reservoir, the new developed horizontal well technique is generalized and applied. The applied scale of the horizontal well technique to the development of Jidong complex fault-block reservoir is speedily extended and the fine result is achieved in lastly two years. In the application of the horizontal well development technique, such series of the horizontal well development techniques as adaptability evaluation of the horizontal wells, scheme deployment, design, drilling, well logging, borehole log, oil production and production management suitable for the features of the complex fault-block reservoir are gradually formed with keeping search and summary. The matching utilization of the technique effectively ensures the applied result of the horizontal well development technique of the small-complex fault-block reservoirs in Jidong Oilfield and it establishes the good fundament for further promoting the advancement of the horizontal well technique. The reservoir with multi-reservoir, small fault-block, bedded edge-bottom waterflood in Gao 63 fault block of the south area in the shallow formation in Gaoshangpu Oilfield, high-effective development for the difficult-to-production reserves in Ng8 subzone of the reservoir for the north area in the shallow formation in Gaoshangpu Oilfield and the practice of high-effective potential by the slim-hole sidetracking horizontal well for improving the development efficiency in the maturing oilfields prove the validity of the method. Key words: horizontal well, complex fault-block reservoir, Jidong Oilfield, development technical method Introduction Jidong Oilfield is located in the north Huanghua Depression of Bohai Bay Basin. Before the " Tenth Five Year Plan", the initial seismic data could not meet the precise research of the reservoir geology, the precision of the reservoir description is difficult to be in conformity with the demand of the design and operation of the horizontal wells and the application of the horizontal well technique is limited as a result of mult-faults, broken fault blocks and deep-buried formation of interest. In the end of the " Ninth Five Year Plan" and since the " Tenth Five Year Plan", Jidong Oilfield has increased the investment of the science and technology, the knowledge on the reservoir geology has being dept and the reserves have being increased[1,2]. The incremental reserves are urgently developed and the adjustment of the maturing fields is necessarily made deep. Changing the development thought and improving the development level by application of the new techniques is the significant subject for Jidong Oilfield to face. Jidong is a typical complex fault-block reservoir, it takes on such challenges as low-rate drilling across, low production for the single well, quick breakthrough of water, low oil recovery efficiency and serious sand production in the shallow formation by development of the conventional orientation wells. The horizontal well development technique is positively explored and applied so as to improve the development efficiency. The horizontal well development technique of the complex fault-block reservoirs in Jidong Oilfield is formed by the scale application of the horizontal well technique and continual summarization of practical experiences.
Ye, Xiaoming (CNOOC China Limited, Tianjin Branch) | Huo, Chunliang (CNOOC China Limited, Tianjin Branch) | Wang, Pengfei (CNOOC China Limited, Tianjin Branch) | Gao, Zhennan (CNOOC China Limited, Tianjin Branch) | Xu, Jing (CNOOC China Limited, Tianjin Branch) | Mao, Yue (Wood Mackenzie) | Shi, Xinlei (CNOOC China Limited, Tianjin Branch)
Abstract Bohai oilfield located at Bohai Bay of China mainly consists of complex clastic reservoirs. Reservoir prediction is difficult especially in the deep depth oilfields because of low seismic resolution. In addition, how to quantitatively characterize the risk of new oilfield development and how to build a more elaborate model in the late period of oilfield development are particularly challenging. This paper developed an innovative workflow for complex clastic reservoir characterization of offshore oilfield. A modeling method based on sedimentary evolution simulation, which can provide modeling constraints, is proposed for deep depth oilfields. Through sedimentary evolution modeling and other information, reservoir and structure uncertainty are analyzed, then reserves scale and reservoir connectivity are evaluated through experimental design, geological modeling and streamline simulation; 3p models are selected lastly. A new method is proposed for building an elaborate model of old oilfield with less grid amounts. The fluid seepage effect caused by some small scale configuration units is characterized by a parameter similar to fault transmissibility multiplier data in numerical simulation model, for there is no actual modeling of the configuration units, so the operation efficiency is greatly improved. BZ3 oilfield is a deep depth delta oilfield. A geological model was established for exploration evaluation well placement, reserves evaluation and development plan research based on sedimentary evolution simulation and quantitative uncertainty evaluation, the reservoir prediction accuracy is greatly improved that is confirmed by new drilled wells. Through quantitative uncertainty evaluation, reliable geological basis was provided for engineering investment, which can avoid the investment waste caused by geological uncertainty. Q32 oilfield is a fluvial oilfield that has come into high watercut (86.7%). How to characterize the lateral accretion interlayer (often less than 1 meter) in model for fine remaining oil distribution prediction is difficult, thus the method mentioned above for old oilfield was used. Firstly, a conventional geological model was established, then the lateral accretion interlayer was extracted as interface from it based on configuration results, then the interface was used to extract the parameter named transmissibility multiplier data in the numerical simulation model; a software has been compiled to perform the whole process. Based on the method, more than 100 adjusting wells were disposed and better production results were obtained. These geological modeling techniques have been widely applied in Bohai Bay offshore oilfields in different periods of oilfield development, including BZ2, JZ2, KL10, CFD6, SZ3, and JZ9. This ensures that these oilfield developed with high quality and efficiency.
Abstract As the Offshore oilfields enter the high water cut stage, it encounters new and prominent problems such as difficulty in developing remaining oil, increased water breakthrough and rapid decline in production. How to maximize the recovery of high water cut offshore reservoirs and improve economic efficiency is a challenge. This paper reviews the lessons learned on how SZ field improves water injection to stable reservoir pressure. Architecture unit-based well pattern improvement, Increasing injection and big-pump enhanced liquid production including renovation and capacity expansion of Water treatment system; Polymer flooding, Modifying reservoir flow pattern with Gel Treatment, Polymer Microspheres. The wells display positive responses from the water injection. The responses include stable reservoir pressure, slower production increase, and slightly water cut increase. Enough and high quality water injection is extremely essential to maximize the recovery of a mature offshore heavy oil.
Feng, Xin (China National Offshore Oil Company) | Wen, Xian-Huan (Chevron Asia Pacific) | Li, Bo (China National Offshore Oil Company) | Liu, Ming (China National Offshore Oil Company) | Zhou, Dengen (Chevron Asia Pacific) | Ye, Qiucheng (Chevron Asia Pacific) | Huo, Dongmei (China National Offshore Oil Company) | Yang, Qinghong (China National Offshore Oil Company) | Lan, Lichuan (China National Offshore Oil Company)
Summary BZ25-1s field in Bohai Bay, China, is characterized as a complex channelized fluvial reservoir in which small meandering channels were deposited at different geological times stacking and cross cutting each other. There are many isolated small reservoir systems following channel distributions. Early production showed steep pressure and production decline. Quick implementation of water injection was needed to arrest the fast production decline and to stabilize reservoir pressure. While designing the water-injection plan, we faced a number of challenges, such as high oil viscosity (˜200 cp), strong heterogeneity, poor reservoir connectivity, complex channel geometry, and irregular well patterns. A workflow integrating geological, well-log, seismic, and dynamic production data was developed to optimize a water injection plan for this field after a short production history. Focuses of this workflow are the selection of injection wells (converted from existing producers), timing of water injection, and the optimization of injection rates. Following the workflow, the optimal water-injection design for the areas around Platforms D and E was developed and quickly implemented within the first year of production. We started with a relatively small water-injection rate and gradually increased the injection rate to avoid the fast water breakthrough and yet to limit the pressure-decline rate. The responses from the water injection were very positive and resulted in stable reservoir pressure and increase of oil production. Before water injection, the production-decline rates were 26 and 47% in Platforms D and E, respectively. After 1 year of water injection, oil-production-decline rates in these two platforms were reduced to 19 and 14%, respectively. The responses of water injection for different well groups were analyzed in a timely fashion and adjustments to injection/production strategies were implemented accordingly. New information revealed from the water-injection response analysis was used to update the geological model to reduce the model uncertainty, as well as to adjust the water-injection strategies for better sweep efficiency. Our experiences showed that such dynamic adjustment of injection and production schedule is very important to achieve better water-injection efficiency for this heavy-oil reservoir with complex channel geometry.
Li, Junfei (CNOOC Ltd, Tianjin Branch) | Liu, Xueqi (PetroChina Research Inst. Petroleum Exploration and Development) | Gao, Zhennan (CNOOC Ltd, Tianjin Branch) | Shang, Baobing (CNOOC Ltd, Tianjin Branch) | Xu, Jing (CNOOC Ltd, Tianjin Branch)
Abstract After more than 20 years’ development, S oilfield has entered high water cut stage. The layer contradiction is prominent and the water flooding condition is complex, which result in the complex decentralized state of the remaining oil. In order to determine the remaining oil distribution to guide the comprehensive adjustment of the oilfield, the reservoir architecture analysis of delta front was conducted. Based on the core, seismic data, dense well logging data and production performance data, the reservoir architecture of delta front in Dongying group is characterized with hierarchy process, model guidance and numerical simulation methods. In the paper, the distribution style of interlayers in single mouth bar is discussed. The distribution feature of the remaining oil under the control of interlayers is analyzed. It shows that multiple main channels form continuous mouth bar complex and single mouth bar develops several accretions. Interlayers in single mouth bar express in two forms: the foreset type along the source direction and the arch type perpendicular to the source direction with a low angle from 0.4° to 1.0°. Along the source direction, remaining oil gathers inside accretions whose injection-production does not correspond under the control of interlayers. And the remaining oil is enriched at the front of accretion. In the vertical source direction, the remaining oil accumulates in the high part of accretions. Under the guidance of remaining oil distribution characteristics controlled by reservoir architecture, one horizontal well was deployed. The average output is more than 100m/d and the water cut is under 30%, which indicates the effect of this reservoir architecture analysis work. The successful implementation of the horizontal well demonstrates the vital function of the reservoir architecture research for this kind of mature oilfield. This will also be one promising research direct for the overall adjustment and remaining oil tapping.