Browsing by Author "Wu, X."

Now showing 1 - 3 of 3
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    Application and experimental study of cyclic foam stimulation
    (RSC (Royal Society of Chemistry) Advances, 2015-08-27) Chen, Zhangxing (John); Zhang, J.; Wu, X.; Han, G.; Wang, J.; Ren, Z.; Zhang, K.
    Formation damage is a serious problem in oil and gas industries. Based on common reservoir damage, the conditions and factors resulting in damage were summarized into four categories in this paper. The worldwide advanced technologies applied in reservoir damage treatment are reviewed. For the first time, we propose the concept of injecting nitrogen foam into a formation to treat the damage caused by sand blocking. An application of Cyclic Foam Stimulation is introduced, which enhances productivity significantly. Experimental apparatus for the Cyclic Foam Stimulation was designed, which included a wellbore vessel that could stimulate the effect of sand setting. A reservoir vessel was also designed to supply the foam. Additionally, in order to simulate the formation damage caused by the size and distribution of fine sand, six artificial cores, which were porosity contrastive and sand producing, were prepared based on the technologies of pressure control and PVA membrane wrapping. The experimental results show that the foam has a good discharging effect on sand blockages. Moreover, the effects of the size and distribution of the fine sand on the porosity was studied. It was found that the smaller the size of the grains and the more uniform the grain distribution, the worse the formation porosity. A porosity recovery factor has been defined and the recovery rate of the porosity was also studied. A scientific guide for the application of Cyclic Foam Stimulation can be generated from the studies in this paper.
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    THE LARGEST VOLUME INSCRIBED ROOTED TETRAHEDRON IN A CONVEX POLYHEDRON
    (1992-03-01) Rokne, J.; Wang, S.Z.; Wu, X.
    Given a polyhedron with n vertices, we present an algorithm for finding the maximum tetrahedron rooted on a face of the polyhedron in O(n log n) time. For the result we need to discuss a class of reciprocal search problems.
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    A pseudo-bubble point model and its simulation for foamy oil in porous media
    (SPE Journal, 2015-04) Chen, Zhangxing (John); Sun, J.; Wang, R.; Wu, X.
    This is the second paper of a series in which we study heavy oil in porous media. The first paper dealt with an experimental study (Wang et al. 2008), whereas a mathematical and simulation study is presented here. The research program stems from the need to predict the field performance of a class of heavy-foamy-oil reservoirs. These reservoirs show a better-than-expected primary performance: lower production gas/oil ratios (GORs), higher-than-expected production rates, and higher oil recovery. A mechanism used to account for the observed performance is that the liberated solution gas is entrained in the oil when the reservoir pressure falls below the thermodynamic equilibrium bubblepoint pressure. The presence of entrained gas increases the effective compressibility of the oil phase and prevents gas from becoming a free phase. Hence, the foamy oil behaves as if it has a pseudobubblepoint pressure below the usual equilibrium bubblepoint pressure. This paper describes a pseudobubblepoint model and a methodology that can be used to compute foamy-oil fluid properties from conventional laboratory pressure/volume/temperature (PVT) data. The techniques developed are then used to study foamy oil in the Orinoco belt, Venezuela. The present mathematical model is validated by comparing numerical and experimental results.