New Research and Application of High Efficient Development Technology for Offshore Heavy Oil in China

摘要

China Offshore oilfield is rich in heavy oil, M oilfield in Bohai Bay is the most thick heavy oil field inrnoffshore by far with the formation oil viscosity as high as 450 ~ 950mPa.s. Using conventional oil fieldrndevelopment (depletion and water flooding), the heavy oil field exposed its limits, such as lowrnproductivity of single well, low production rate and low predicted recovery.rnAs we all know, the development effect of thermal recovery is not only related with the thermalrnrecovery methods (steam stimulation, steam flooding, etc.), but also related with the thermal mediumrn(steam, hot water, flue gas etc.). A new thermal media called multi-thermal fluid, which contains steam,rnhot water and flue gas was researched for horizontal well stimulation, which is to inject N2 and CO_2 atrnthe same time when injecting steam. This multi-thermal fluid could employ various mechanisms of eachrnfluid, including reducing oil viscosity by heating and dissolving gas, increasing pressure by injectingrngas, expanding heating range, reducing heat loss and gas assisting gravity drive etc.With the advantagesrnof single thermal injection, this method made up the disadvantages of single thermal fluid injection andrncan improve steam stimulation effect in some special formation conditions.rnIn this article, the author first analyzed the characterization of multi-thermal fluid, and then researchedrnits stimulation theory. Based on this theory, the single element of geological data, such as dip angle,rnpermeability, rock compression coefficient, formation thickness, oil viscosity, and injection data, such asrninjection volume, gas-water-ratio and CO_2 concentration was analyzed using numerical simulationrnsoftware. Based on this result, selecting data that make more contribution in incremental oil, productionrnrate, and EOR to make sensitivity study to summarize formation that multi-thermal fluid could bernapplied.rnBased on the theoretical research, a multi-thermal fluid stimulation pilot test was carried out at Mrnoilfield applying compact thermal recovery equipment. The first cycle of the pilot test showed somernoptimistic results. Multi-thermal fluid stimulation becomes a new efficient development model forrnoffshore heavy oil, opening up a domestic precedent of thermal development of offshore heavy oilrn(except shallow sea).