In order to test the effectiveness and efficiency of nano-microspheres which can be used to effectively reduce water cut with a small slug size, a series of experimental tests have been conducted to evaluate the performance of nano-microspheres and factors affecting the performance. Those tests include hydration swelling characteristics, blocking and migration characteristics, salt resistance, shear resistance and so on. Based on the experimental study, detailed pilot test design were conducted by considering the different reservoir pore structures and microsphere sizes used for oil displacement, so that the slug size is minimized while the net revenue is maximized. Since 2009, deep profile control technology by injecting small slug-size nano-microsphere has been developed in offshore oilfields in Bohai Sea. The main mechanism of nano-microsphere is different from the traditional approaches which increase the water phase viscosity to improve mobility ratio. In nano-microsphere deep profile control technology, nano/micron level microspheres were dispersed in the water phase. Along with the water injected into formation, microspheres swell under the formation condition, plug the water channels, reduce the permeability of high permeable zone, dynamically change the water flow paths, thus increase the water sweeping efficiency. Since 2009, a total of 17 well patterns have implemented in QHD, BZ28, BZ29 oilfields in Bohai Sea. In all those tests, small slug sizes in the range from 0.01 to 0.02 PV were used. Water cut is reduced from 80% to 70% and cumulative oil production was increased by 13.1×106m3. The economic evaluation suggests that for every one dollar investment on this technology, 3.1 dollar can be made even when the oil price is $30 per barrel. So the project has a good technical and economic outcome even in extreme low oil prices.

QHD oilfield in Bohai Bay, China, is characterized by conventional heavy oil (average viscosity 150cp under reservoir conditions) with excellent reservoir quality (up to 30% porosity and 1-2D permeability) and strong aquifer. Horizontal and multilateral wells are widely used in QHD and most wells were standard completion. After 13 years of development, many wells show sharp production decline and rapid water cut increase. What's more, water breakthrough in several wells is much earlier than prediction. The high mobility ratio, hell-toe effect, bottom water, permeability heterogeneity and sand are contributed to reduced ultimate recovery and well life.The use of ICD (inflow control device) is becoming more and more prevalent as it can delay the water break through and significantly improve the economic life of a well. This is especially important for offshore fields where well intervention is difficult and expensive. Therefore, ICD technique is proposed to address the above production problem while prolonging production life (BREKKE K, 1997).In this paper, I discuss the feasibility of ICD for horizontal wells in heavy oil reservoir of offshore field. First, I analyze the actuality of the offshore heavy oil with strong bottom water in Bohai Bay and the reason of bottom water coning. Secondly, I discuss the feasibility of ICD for horizontal wells in heavy oil reservoir of offshore field. Finally, a new method is established to design the additional pressure of ICD. The method is compared to the uniform liquid method; what's more, a numerical model is developed to validate the new method. The production performance of the first ICD wells was discussed to provide evidence on its effectiveness and robustness. This has provided valuable data prior to well drilling and the final optimization of ICD.The paper demonstrates the importance of seamless teamwork and coordination between reservoir engineers and project team to deliver superior performance. In a word, this paper is expected to assist well completion decisions for offshore heavy oil reservoir and to spark continue research on ICD.

Fluvial facies reservoirs account for 60% of the reserves in Bohai oilfield. The effective development of such reservoirs plays a very important role in long-term stable production of Bohai oilfield. There are many challenges including: poor reserve, large well spacing, large lateral changes, poor connectivity, heterogeneity, unfavorable viscosity, low structure amplitude and strong bottom water. Horizontal wells are widely used in these reservoirs, especially in the edge or bottom water reservoir and the narrow channel reservoir in Bonan area. Many cases of horizontal wells design, implementation, well pattern optimization and water flooding management were presented to improve the recovery rate of fluvial oil reservoirs. The technique has been widely used in ten fluvial oil fields in Bohai, and has enhanced the recovery rate of by 3% and achieved remarkable technical and economic effects.

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Portfolio optimization is a financial task which requires the allocation of capital on a set of financial assets to achieve a better trade-off between return and risk. To solve this problem, recent studies applied multi-objective evolutionary algorithms (MOEAs) for its natural bi-objective structure. This paper presents a method injecting a distribution-based mutation method named Lévy Flight into a decomposition based MOEA named MOEA/D. The proposed algorithm is compared with three MOEA/D-like algorithms, NSGA-II, and other distribution-based mutation methods on five portfolio optimization benchmarks sized from 31 to 225 in OR library without constraints, assessing with six metrics. Numerical results and statistical test indicate that this method can outperform comparison methods in most cases. We analyze how Lévy Flight contributes to this improvement by promoting global search early in the optimization. We explain this improvement by considering the interaction between mutation method and the property of the problem. We additionally show that our method perform well with a round-lot constraint on Nikkei.