The imbibition mechanism and the calculation method of maximum imbibition length during the hydraulic fracturing

Abstract

It was acknowledged that fluid imbibed into matrix and flooded oil during the hydraulic fracturing; however, the mechanism of fluid imbibed into matrix and flooded oil still kept unclear. Meanwhile, the maximum imbibition length calculation method was still scarce. In the paper, we firstly analyzed the imbibition mechanism during the hydraulic fracturing, and then built an imbibition length calculation method by the mercury intrusion experiment, seepage theory, and numerical calculation method. By comparing with the experimental results and model calculation results, our proposed method was verified. Finally, the influences of the maximum imbibition length were presented. From the work, it was concluded that the imbibition during the hydraulic fracturing was the counter-current imbibition with the surround pressure. The effect of the permeability on threshold pressure gradients was greater than that on the capillary pressure, which caused that the maximum imbibition length increased with an increased permeability (from 0.01 to 0.2×10-3μm2), but the time of achieving maximum imbibition lengths decreased exponentially. When the reservoir permeability was 0.1×10-3 μm2, the contact angle was 60°, and the interface tension was 50 mN/m, the maximum imbibition length was 1.8 m, and the time of achieving maximum imbibition length was 70 days. This study provided a method for evaluating the extent of imbibition draw.