South part of NN reservoir, locating at Bohai Bay of China, has geology characteristics of flat structure, complex oil-water contact system. The formation oil viscosity reaches as high as 413~741mPa•s. At initial production stage, daily oil of vertical well and horizontal well reached 21m3/d and 35m3/d, respectively. Due to complex oil-water relationship and high formation oil viscosity, oil production rate of whole reservoir decreased from 0.6% to 0.3% after one year. Combinatorial development techniques including thermal huff-puff and weak gel flooding have been optimized for further enhancing oil recovery. Considering the platform space limit, thermal huff-puff uses multiple thermal fluid(nitrogen, dioxide, hot water) instead of conventional steam. Twelve new horizon wells have been carried out in the pure oil zone for thermal huff-puff pilot. Until now, there have been twelve wells which completing the first cycle huff-puff, and six wells have completed the second cycle. Meanwhile, in order to keep the formation pressure and reduce the channeling risk, selected three high water-cut production wells were changed into injection wells for weak gel flooding pilot. After carried out combinatorial development techniques, the rate of oil production of whole reservoir has increased from 0.3% to 0.7%. Thermal huff-puff heated oil during the huff process then decreases the formation oil viscosity, and finally increasing the production ability of horizon wells in the puff process. Compared with natural energy production, peak oil production and periodic oil production of thermal production respectively increases to 3 times and 1.6 times in the first cycle. Weak gel flooding increases viscosity of the injected fluid and reduces the difference of water-oil mobility ratio, the average resistance coefficient of three injection wells reaches as high as 1.74. Around the three injection wells, there are nine wells increasing the oil production, and incremental oil production for single well has reached 0.45×104m3~2.12×104m3 in the past few years. Also, there is a positive synergistic effect between thermal huff-puff and weak gel flooding. The artesian flow days of one thermal well extends 76 days in the help of weak gel flooding. Our experiences show that such combinatorial development techniques are effective for enhancing oil recovery of heavy oil fields and meet the demand of high speed development for offshore oil fields.
This article gives an overview of Bluetooth and Bluetooth Low Energy. Furthermore, it presents BlueTrk+, a lightweight application for tracking presence and position securely and flexibly for military-related or Disconnected, Intermittent and Limited (DIL) environments. For tracking presence, four schemes with varying security levels are presented for broadcasting identities. For tracking position, a polar coordinate-based approach is used. It involves using a radar-inspired method for estimating direction/angle and a machine learning method for estimating distance. Experimental results are presented to evaluate the positioning methods.
During the later period of steam injection, the oil production largely decreases to be a state of low production or low oilsteam ratio. In this article, a classification method of low production wells was established and some measures of improving oil production were researched for the low production wells during thermal recovery. Three visualization experiments were implemented to analyze the sweep efficiency and to measure the oil recovery factor during injecting different flooding agents. Then a novel diagram was introduced to guide us how to precisely choose the appropriate measures for the low production wells during thermal recovery in heavy oil reservoirs. According to the statistical results, the low production wells can be categorized into three types involving high degree of oil recovery, thermal disturbance (even steam channeling) among wells and dual factors. The results of visualization experiments showed that the injection of chemical agents can effectively increase the displacement efficiency in swept zone after steam injection. Temperature-resistant gel or foams can be used to decrease thermal disturbance and even steam channeling among wells during steam injection in heavy oil reservoir. The values of a new parameter can be employed to confirm the boundary of different improvement measures. Finally, a diagram was established to help choosing appropriate measures involving nitrogen injection, foam injection, gel injection and invalid measure.
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