Beneficial effects of wettability altering surfactants in oil-wet fractured reservoirs

In fractured reservoirs, an effective matrix-fracture mass transfer is required for oil recovery. Surfactants have long been considered for oil recovery enhancement, mainly in terms of their ability to reduce oil–water interfacial tension. These surfactants are effective when the fractured formations are water-wet, where capillary imbibition of surfactants from the fracture into the matrix contributes to oil recovery. However, another beneficial aspect of surfactants, namely their ability to alter wettability, remains to be explored and exploited. Surfactants capable of altering wettability can be especially beneficial in oil-wet fractured formations, where the surfactant in the fracture diffuses into the matrix and alters the wettability, enabling imbibition of even more surfactant into the matrix. This sequential process of initial diffusion followed by imbibition continues well into the matrix yielding significant enhancements in oil recovery.In order to test this hypothesis of sequential diffusion–imbibition phenomenon, Dual-Drop Dual-Crystal (DDDC) contact angle experiments have been conducted using fractured Yates dolomite reservoir fluids, two types of surfactants (nonionic and anionic) and dolomite rock substrates. A new experimental procedure was developed in which crude oil equilibrated with reservoir brine has been exposed to surfactant to simulate the matrix-fracture interactions in fractured reservoirs. This procedure enables the measurements of dynamic contact angles and oil–water interfacial tensions, in addition to providing the visual observations of the dynamic behavior of crude oil trapped in the rock matrix as it encounters the diffusing surfactant from the fractures. Both the measurements and visual observations indicate wettability alterations of the matrix surface from oil-wet to less oil-wet or intermediate wet by the surfactants. Thus this study is of practical importance to oil-wet fractured formations where surfactant-induced wettability alterations can result in significant oil recovery enhancements. In addition, this study has also identified the need to include contact angle term in the dimensionless Bond number formulations for better quantitative interpretation of rock–fluids interactions.     

Adaptive Spatial Partitioning for Multidimensional Data Streams

We propose a space-efficient scheme for summarizing multidimensional data streams. Our sketch can be used to solve spatial versions of several classical data stream queries efficiently. For instance, we can track ε-hot spots, which are congruent boxes containing at least an ε fraction of the stream, and maintain hierarchical heavy hitters in d dimensions. Our sketch can also be viewed as a multidimensional generalization of the ε-approximate quantile summary. The space complexity of our scheme is O((1/ε) log R) if the points lie in the domain [0, R]^d, where d is assumed to be a constant. The scheme extends to the sliding window model with a log (ε n) factor increase in space, where n is the size of the sliding window. Our sketch can also be used to answer ε-approximate rectangular range queries over a stream of d-dimensional points.     

Bayesian and Dempster-Shafer fusion

The Kalman Filter is traditionally viewed as a prediction-correction filtering algorithm. In this work we show that it can be viewed as a Bayesian fusion algorithm and derive it using Bayesian arguments. We begin with an outline of Bayes theory, using it to discuss well-known quantities such as priors, likelihood and posteriors, and we provide the basic Bayesian fusion equation. We derive the Kalman Filter from this equation using a novel method to evaluate the Chapman-Kolmogorov prediction integral. We then use the theory to fuse data from multiple sensors. Vying with this approach is the Dempster-Shafer theory, which deals with measures of “belief”, and is based on the nonclassical idea of “mass” as opposed to probability. Although these two measures look very similar, there are some differences. We point them out through outlining the ideas of the Dempster-Shafer theory and presenting the basic Dempster-Shafer fusion equation. Finally we compare the two methods, and discuss the relative merits and demerits using an illustrative example.     

Formation and characterization of oxynitride glasses in the Si-Ca-Al-O-N and Si-Ca-Al,B-O-N systems

Oxynitride compositions in the Si-Ca-Al-O-N and Si-Ca-Al, B-O-N systems were melted and furnace-cooled in BN crucibles at temperatures from 1650 to 1850° C under dry nitrogen atmosphereS. Glass formation, phase stability and crystallization were studied by characterizing the cooled melts by X-ray diffraction, DTA, and electron microscopy. Oxynitride batches with nitrogen content up to 11 at % formed glasses in the Si-Ca-Al-O-N system. Glasses in the Si-Ca-Al, B-O-N system could be formed only when the B₂O₃ content of the batch was less than 3 wt %. Oxynitride glasses in these boron-containing systems were characteristically inhomogeneous, difficult to process, and prone to crystallization. In both the systems, glasses exhibited glass transitions beginning at 1000° C and crystallization at 1300 to 1500° C. Nitrogen-containing crystalline phases were identified in devitrified glasses via microstructural and micro-mechanical analyses.     

Microchemistry and microstructure of a multiphase aluminosilicate ceramic

The microstructure and microchemistry of a sintered (≈ 1700° C) aluminosilicate ceramic (60 wt % Al₂O₃-40 wt% SiO₂) was investigated by optical, scanning (SEM and EDAX), and analytical electron microscopy (TEM and STEM). The microstructural features of the fired ceramic consisted of unreacted Al₂O₃, glass, porosity, and equilibrium and metastable mullite phases. Residual Al₂O₃ agglomerates (≈ 15 to 30 μm in size) were surrounded by a ≈ 6 μm layer of equilibrium mullite (≈ 71.3 to 73.5 wt% Al₂O₃). The unreacted Al₂O₃-equilibrium mullite assembly formed islands embedded in a silica rich glass (≈ 4.5 to 14wt% Al₂O₃) which also contained 2 to 3 μm thick metastable mullite needles (≈ 70 to 77 wt% Al₂O₃). Phase separation and alumina rich glass compositions (≈ 57 to 59 wt% Al₂O₃) were also observed in some areas of the microstructure.     

双超越离合器式电磁馈能阻尼器原型机试验测试与分析

在对双超越离合器式电磁馈能阻尼器的前期研究基础上,试制了该阻尼器的原型机,并对谐波激励下原型机的频谱响应特性和阻尼响应特性进行了分析。通过对原型机的测试,证明了该结构方案的可行性,同时还证实了利用转动惯量分力,在被动模式下实现"high-low"半主动阻尼方法的正确性,并为展开对双超越离合器结构的进一步研究奠定了基础。     

Compressing Two-Dimensional Routing Tables

We consider an algorithmic problem that arises in the context of routing tables used by Internet routers. The Internet addressing scheme is hierarchical, where a group of hosts are identified by a prefix that is common to all the hosts in that group. Each host machine has a unique 32-bit address. Thus, all traffic between a source group s and a destination group d can be routed along a particular route c by maintaining a routing entry (s, d, c) at all intermediate routers, where s and d are binary bit strings. Many different routing tables can achieve the same routing behavior. In this paper we show how to compute the most compact routing table. In particular, we consider the following optimization problem: given a routing table D with N entries of the form (s, d, c) , determine a conflict-free routing table with fewest entries that has the same routing behavior as D. If the source and destination fields have up to w bits, and there are at most K different route values, then our algorithm runs in worst-case time O( NK w2) .     

A cyclic policy for the loading of multiple products on a vehicle with different compartment sizes

In this paper, we address a multi-product loading problem in which a vehicle (a truck or a ship) is used to transfer multiple products. The product demands are different but stationary over time. The vehicle consists of compartments of different sizes and each compartment can contain only one product type during each shipment. No shortages are permitted, and we assume that the inventory holding cost is significantly lower than the delivery cost. The objective is to minimize the setup rate, that is, the number of deliveries per time unit. A cyclic policy is shown to be optimal, and a heuristic algorithm is developed to determine the cycle length as well as the assignments of products to the compartments during each of the requisite number of shipments made during that cycle. A comparison of the solutions obtained by the proposed algorithm with the optimal solutions (or a bound) indicate that the algorithm provides solutions with optimal setup rates in most of the problem instances considered and, when not optimal, the setup rates of these solutions are close to optimal values.