The objective of this work was to elucidate the mass exchange dynamics (MED) between the tight rock matrix and fractures induced by natural gas ‘dynamic’ soaking (NGDS) during Huff- n -Puff. The equilibrium interfacial tension (IFT) between natural gas (NG) and oil decreased rapidly with an increase in the NG C2/C3 fraction and equilibrium pressure ( P eq ). The IFT curves were separated into two distinct regimes because of the transition of the MED from gas dissolution to oil vaporization. The apparent diffusion coefficient of NG ranged from 4.9 × 10 −11 to 3.35 × 10 −9 m 2 /s. The dissolution of NG into the oil resulted in a linear swelling behavior with P eq . Mass exchange between matrix and fracture took place intensively from the onset of NGDS, driven by gas diffusion, oil swelling, and concentration gradient-driven flow, which stimulated the oil recovery up to 59.3% original oil in place . The NGDS oil recovery curves exhibited three distinctive regions because of the MED evolution over time. The average cutoff pore radius for NGDS-movable oil was less dependent on the operational pressure but was affected by the C2/C3 fraction. We modified a dimensionless number to better correlate the NGDS oil recovery and predict field-scale production.
Ning Zhang,Yang Wang,Wenpeng Xu,Yong Hu,Jianxun Ding
Mass transfer restrictions of scaffolds are currently hindering the development of three-dimensional (3D), clinically viable, and tissue-engineered constructs. For this situation, a 3D poly(lactide-co-glycolide)/hydroxyapatite porous scaffold, which was very favorable for the transfer of nutrients to and waste products from the cells in the pores, was developed in this study. The 3D scaffold had an innovative structure, including macropores with diameters of 300–450 μm for cell ingrowth and microchannels with diameters of 2–4 μm for nutrition and waste exchange. The mechanical strength in wet state was strong enough to offer structural support. The typical structure was more beneficial for the attachment, proliferation, and differentiation of rabbit bone marrow mesenchymal stem cells (rBMSCs). The alkaline phosphatase (ALP) activity and calcium (Ca) deposition were evaluated on the differentiation of rBMSCs, and the results indicated that the microchannel structure was very favorable for differentiating rBMSCs into maturing osteoblasts. For repairing rabbit radius defectsin vivo, there was rapid healing in the defects treated with the 3D porous scaffold with microchannels, where the bridging by a large bony callus was observed at 12 weeks post-surgery. Based on the results, the 3D porous scaffold with microchannels was a promising candidate for bone defect repair.Keywords:poly(lactide-co-glycolide);hydroxyapatite;porous scaffold;microchannel;cell ingrowth;mass exchange;bone tissue engineering
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