Research On Redevelopment Protection Hydrocarbon Zone Of Lunnan Reservoir

Reservoir protection is a form of job involved in multidisciplinary and multi-section, which is a system technology running through the whole process of field exploration and development. It must be taken into consideration that the reservoir protection consciousness is important from the beginning of well drilling to reservoir depletion. Just as the old saying goes,"One false move may lose the game," any mistake in a little link may affect the result of reservoir protection. Only implementing protection measurement in the whole course can we hit the mark of effective development of oil and gas resources.Oil and gas, important energy which we live by, are deeply buried in reservoir stratums. Scientific research and production practice indicate that foreign fluid, such as drilling fluid and completion fluid, would have Physicochemical reactivity with rocks in the stratums and damage the reservoir in every link of exploration and development, especially in the process of well drilling and completion. The damage to the stratum may influence the well capacity and production and reduce the final recoverable reserve. Therefore, it is significant and practical to carry out evaluating and forecasting methods study about drilling mud and completion fluid so as to bring up well capacity and final recovery ratio in oil and gas field.Reservoir stratums damage experimental researches include indoor simulator, damage mechanism, evaluation criterion and protection technology. Since1950s, foreign researchers have studied reservoir damage mechanism, but they just made slow process in the next20years, while sporadic literature reports came out and most of them are confined to reservoir damage owing to hydration and swelling of clay. The Middle East embargo caused the increase of oil price in1970s, so people began paying attention on reservoir protection. And in1980s, systematic researches on reservoir stratums are conducted with the help of new testing technology and advances on reservoir damage mechanism. From the end of80s to present, researchers introduces mathematic simulation methods to the study and have made significant progress on reservoir protection technology and gained prominent economic benefits.Lunnan oilfield came to exploration in1987, and prospector discovered this oilfield stem testing on Lunnan-2well. In June of1989, some pilot productions were implemented in Lunnan, and the oilfield were brought into development in May of1992. The oilfield entered into high and stable yield stage(100MTPA), until2002the stable production period has last for10years. Main reservoir, Lunnan-2well area TI oil group, began water injection in March1993, and the injection pattern was edge ring injection combined with internal point-like injection.Lunnan oilfield has developed for20years from1992to2009with1441×104tons oil. The production decreased rapidly from2005, and the recovery of recoverable reserves was up to84.5percent with90.1percent of water cut. Through the early stage of potential analysis and evaluation screening, Lunnan becomes the first oilfield to start second development researches in Tarim, whose reservoir conditions, fluid properties, reservoir type and development mode are typical. After the development of20years, the remaining oil distribution is highly dispersive, and the water oil relationship is complicated. The average daily production of single well declined year by year, while the pressure coefficient decreases from1.7to1.3. Underground oil and water system is much more different from the initial stage of development, and the infill wells are restricted by various conditions in the process of drilling and production, which are vulnerable to pollution so as to influence per well production. Therefore, it is necessary to implement reservoir protection researches on second development of Lunnan-2and Lunnan-3well areas.In order to draw up oil and gas reservoir stratums protection scheme of second development in Lunnan oilfield and provide a reference to other reservoirs, this paper bases on much different information, such as Seismic interpretation result, microfacies and individual layer data, clay mineral content, core analysis, well coordinate and track, logging interpretation result, perforation and measures material of water and oil wells, as well as production dynamic material, relative permeability curve, high pressure physical parameters, reservoir sensitive material and drilling the well completion fluid material. With the help of software about reservoir geologic modeling and numerical simulation, we can get the pressure and water saturation distribution in the area. Then calculate old wells’depth of reservoir damage and statically analyze the mud system and pollution damage situations, therefore, we could gain hydrocarbon reservoir protection effect with different drilling mud protection systems. This paper mainly has the following results and the understanding:(l)Set up fine structure model for Lunnan-2and Lunnan-3well areas, which could describe complex fault block oil field in this area, and provide some materials about faults.(2)Build models about porosity, permeability and water saturation in Lunnan-2and Lunnan-3well areas and describe the reservoir anisotropy, which could provide high reliability static data body for further numerical reservoir simulation.(3)Due to static data body and numerical reservoir simulation, pressure distribution and water saturation change rules could be received.(4)Evaluate the reservoir damage degree of30old wells in Lunnan-2and Lunnan-3well areas, and analyze the main impact factor (Skin parameter), and deduce the formation damage skin factor combined with reservoir damage depth so as to gain the evaluation result.(5)Analyze the mud system, which contains sulfonylurea system, double protect system, environmental protection system, polymer system and organic salt system. Compare the results of reservoir damage evaluation and we could draw this conclusion: sulfonylurea system and environmental protection system are better than others at reservoir protection.(6) According to the sensitivity of the reservoir experimental evaluation in Lunnan, the reservoir sensitivities sorted by size are as follows:water sensitivity(very strong), speed sensitivity(strong),salt sensitivity(strong), ph sensitivity(medium weak), alkali sensitivity(medium weak).(7)According to the contrast experiment between OBM and WBM, some conclusions are as follows:when in the OBM, the diesel bag water(90:10) system can gain the minimum filtration(2.20ml), and at that time permeability recovery value is the largest(87.59percent), i.e. that mud system has the best reservoir protection effect.