The Experimental Research Of Imbibition Mechanisms Of Tight Reservoirs On The M Block Of Santang Lake Basin

The M block of Santang Lake basin has great potentiality of tight oil.The tight reservoirs are widely distributed and oil-rich.The reservoir physical property has the characteristics of mid-level and high-level porosity,super-low permeability and highlevel oil saturation.Multi-stage fracturing technique in horizontal well is commonly used for tight oil reservoir development due to its tiny pores and throats,as well as extremely low permeability in order to bring it into production at the beginning.Low flow-back rate of fracturing fluid is often observed to correspond with higher oil recovery,in which spontaneous imbibition is considered to be one of the most important mechanisms.However,large amount of oil will still be left after this stage,in which depletion is the main mechanism,and water huff-and-puff is recently proposed to be a promising method for enhanced oil recovery in such oil reservoirs.The water injected will flow in fractures and spontaneously imbibe the oil into the fractures.The oil is then produced during “puff” process.Spontaneous imbibition is a very important mechanism for tight oil reservoir exploration and it is a hot topic being investigated by many researchers,but systematic study of influencing factors on imbibition oil recovery factor and how to improve oil recovery factor is insufficient.In this study,large of imbibition tests were performed and many influencing factors were taken into account by the quality method,such as permeability of rock,size of rock,cracks,viscosity of oil,brine salinity,temperature and pressure.Also,different types,concentrations and ratios of surfactants were investigated for screening the best imbibition agent and finding the mechanisms of improving imbibition effect by lowering IFT and wettability of rock.Finally,concluding relevant imbibition mechanisms and ways of enhancing imbibition efficiency by studying the influences of water-flood huff and puff rounds,timing and soaking time in numerical modeling way.This study is importanct for improving the imbibition efficiency of the M block of Santang Lake basin's tight oil reservoirs.