EXPERIMENTAL RESEARCH ON QUANTIFICATION OF COUNTERCURRENT IMBIBITION DISTANCE FOR TIGHT SANDSTONE

Abstract

China has an unbelievable number of tight oil reserves in storage, but a large majority of the tight oil reservoirs are in low sweep efficiency and in poor depletion development. Countercurrent imbibition is an important recovery mechanism for enhancing oil recovery during water injection development of tight oil reservoirs. At present, a large number of scholars have mainly conducted research on the imbibition recovery of tight oil reservoirs as well as the factors that may have influences on that, but actually there are few research on the imbibition distance that characterizes the range of imbibition effect in tight oil reservoirs. In this paper, the CT online scanning device is employed to establish a quantification method for countercurrent imbibition distance (CID) of tight cores, determining the range of countercurrent imbibition, and it also can make a further study on the influence of fluid pressure, water saturation, core permeability and surfactant on CID. In addition, it can be utilized to determine the relationship between CID and imbibition recovery. As a result, this study also provides theoretical guidance for enhancing oil recovery of tight oil reservoirs. The research results show that the CID scale of tight core with the permeability of about 0.3 mD is only 1.25 ~ 1.625 cm, and CID of the tight core with 0.302 mD under the condition of 5 MPa is 1.375 cm. Under the experimental conditions in this article, fluid pressure and initial water saturation have little effect on the CID of tight cores, while permeability and surfactant have significant effect on the CID of tight cores. What’s more, the CID of the core with 0.784 mD is 2.63 times higher than that of the core with 0.302 mD. In conclusion, the CID is a crucial parameter for the characterization of imbibition recovery, and it determines the range of countercurrent imbibition.