Summary To determine the effect of water-soluble polyacrylamide polymer adsorption and flow behavior on oil recovery, relative permeability and mobility were determined from flow experiments at various polymer concentrations. A selective reduction of the relative permeability to water with respect to the relative permeability to oil was observed for both Berea and reservoir sandstone cores. Adsorbed polymer layer increases water wettability. Relative permeability reduction could be attributed to both wettability change and pore-size restriction due to the adsorbed polymer layer. An empirical model was proposed to correlate the relative permeability reduction and the amount of polymer adsorption. Depletion-layer effect results in a reduced polymer viscosity in porous media with respect to bulk solutions. Modification of the existing shear-rate model allows for accurate prediction of this effect. The integration of the new models in UTCHEM provides a more accurate tool for engineering design of polymer applications. Introduction Water-soluble polyacrylamide polymers have been used to reduce water production in oil wells and for mobility control in injection wells for decades.1 One of the attractive properties of polyacrylamides is their ability to reduce the relative permeability to water more than the relative permeability to oil in porous media. From the published field tests on well treatments by polymer adsorption in the 1970's and 1980's,1,2 only a few jobs were considered to be economically successful. Results could not be interpreted due to the lack of detailed information. At present, the importance of laboratory research and simulation study are emphasized for successful field design. The selective permeability reduction by polymer adsorption was traditionally termed as "permeability reduction" or "residual resistance factor," which is equivalent to the endpoint relative permeability. Previous laboratory results1 indicated that the maximum reduction of the endpoint relative permeability to water caused by polymer adsorption can be as high as a factor of 10, while the reduction of the endpoint relative permeability to oil is less than 2. If crosslinking or swelling agents are applied, the maximum reduction of the relative permeability to water could be more than two orders of magnitude. The mechanisms of this selective reduction have been explored by several researchers.3–5 An understanding of these mechanisms could be obtained from the selective permeability reduction by gels.6 Measurement of the residual resistance alone may provide a qualitative estimation. To model the effect of polymer adsorption, however, a measurement of the relative permeability is necessary, especially when residual saturation and the shape of the relative permeability curves change after polymer adsorption. Modification of the relative permeability by polymer adsorption has been intensively studied recently.3-5,7-10 Ali et al.4 and Barrufet and Ali,5 derived the relative permeability from drainage capillary pressure measured by an ultracentrifuge and showed that the reduction of the relative permeability caused by starch-based polymers is dependent on saturation. The reduction was interpreted as a change in lubrication along the pore walls. Direct measurement of relative permeability after polymer adsorption was also seen in Refs. 3 and 7 through 10. In water-wet porous media, it was found that the residual oil saturation remained almost the same after polymer treatment. At residual oil saturation, the quantity of adsorbed polymer per gram of rock was also found to be almost the same as at 100% water saturation, but the endpoint relative permeability reduction to water was increased in the presence of residual oil. Based on a capillary bundle model, a correlation of the relative permeability curves with polymer-layer thickness was proposed by Zaitoun and Kohler.3 However, the relationship of the polymer-layer thickness with the quantity of adsorbed polymer is still unknown, and further modification of the capillary bundle model may also be needed to model complex pore matrices. On the other hand, as polymer propagates through porous media, polymer solution will be diluted in the propagation front due to dispersion and adsorption, and the dilution could extend to the entire slug if the slug size is too small. So far, few researchers have related the variations of the relative permeability curves as a function of polymer concentration or the quantity of adsorbed polymer. Therefore, one of the objectives in the present study is to measure and correlate relative permeability curves as a function of polymer adsorption. Polymer solution mobility was also studied as a function of polymer concentration. Effective viscosity at low shear rate in porous media is lower than that in bulk solution at the same shear rate. The dependence of the depletion-layer effect on polymer concentration as well as porous media will be examined in this paper. Finally, the numerical models of relative permeability and mobility as a function of polymer concentration developed in this study will be incorporated in UTCHEM. Several cases will be studied to compare incremental oil recovery predicted by these new models with that predicted by previous descriptions of polymer behavior in porous media. A simplified layered reservoir model will be used for comparative simulation runs. Polymer flooding and near-wellbore polymer treatments will also be simulated. Results from these simulations should provide guidelines for future field strategies. Experiment Porous Media. Both strongly water-wet and mildly oil-wet cores were chosen to study the influence of wettability on polymer adsorption, two-phase relative permeability, and polymer solution mobility. The mildly oil-wet medium is a Warden reservoir sandstone core from Santa Fe field, Stephens County, Oklahoma. Two strongly water-wet media are Berea sandstone cores with different permeabilities. Table 1 summarizes the petrophysical properties of these sandstone samples. Fluids. Synthetic brines were prepared to represent reservoir brine (produced water) composition and makeup water (injection water) composition used in the Warden reservoir. Produced water has a total dissolved solid (TDS) of 31,300 ppm which contains 29 g/L NaCl, 0.94 g/L CaCl2, 0.77 g/L MgCl2, 0.11 g/L KCl, and 1.1 g/L NaHCO3, and injection water has a TDS of 1,490 ppm which contains 0.343 g/L CaCl2, 0.252 g/L MgCl2, 0.176 g/L Na2SO4, and 0.72 g/L NaHCO3

To determine the effect of water-soluble polyacrylamide polymer adsorption and flow behavior on oil recovery, both steady-state and unsteady-state flow experiments were performed on Berea sandstone and reservoir cores. Berea sandstone core is strongly water-wet while the reservoir core is mildly oil-wet. Relative permeability curves and polymer adsorption measurements were made at residual oil saturation and 100% water saturation for increasing polymer concentrations. Mobility measurements were made at different polymer concentrations and shear rates. A selective reduction of the relative permeability to water with respect to the relative permeability to oil was observed for both Berea and reservoir sandstone cores. The reduction of the relative permeability to water in the presence of oil phase is more than that at 100% water saturation. As polymer concentration increases, polymer adsorption, irreducible water saturation and relative permeability reduction increase. Residual oil saturation remains almost the same. Wettability is beneficial to water-soluble polymer adsorption. In reservoir core, relative permeability reduction could be attributed to both wettability change and pore-size restriction. Polymer adsorption isotherm follows Langmuir's law. Relative permeability reduction as a function of polymer adsorption exhibits an "S-type" curve. It increases exponentially as polymer adsorption increases and eventually approaches a constant. An empirical model was proposed to correlate this characteristics. As predicted by the depletion layer and viscoelasticity theories, flow behavior of polymer solution in porous media is found to be significantly different from that in bulk solutions. A modification was made to the existing shear rate model based on mobility measurements, showing that the depletion layer effect is in direct proportion to polymer concentration, and is more significant in the reservoir core than in Berea core. New models were incorporated in UTCHEM, a chemical flood simulator developed by the University of Texas. These models can provide more accurate prediction of the combined effects of relative permeability reduction and viscosity over existing models. Case studies show that the long-lasting relative permeability reduction by polymer adsorption is likely to maximize the benefits of polymer solution in polymer flooding. Increased understanding through simulation may lead to improved field profile modification and near wellbore treatments. The effects of cross-flow and the degree of relative permeability reduction are two critical factors to determine polymer placement strategies and success. P. 293

Considering the fact that the anti-swing performance and transport efficiency of the crane system are not satisfactory if we just control the velocity of the cable car, we came up with a joint control technology of the rope and trolley in crane system. Firstly, the simplified mathematical model of the cable car system is built. Secondly, the best joint control scheme is discussed by modeling simulating. Finally, the designing of joint control system is analyzed. What’s more, we will carry relevant experiments about the joint control technology in the near future. The data obtained from our experiment will be used to verify our theoretical results of joint control.

Based on the principle of the attenuation of an acoustic wave propagating in a gas-liquid two-phase flow, an experiment has been designed to measure the void fraction. The experiment system is consisted of three segments which arepressure stabilizing control system, ultrasonic measurement system and bubble injection system. The measurement process is three steps. First, a reference experiment is performed to acquire the received signal amplitude in pure liquid. Then, measurement of the received signal amplitude in different void fraction is accomplished. Last, the relationship between void fraction and signal amplitude attenuation is given on which the void fraction of two-phase flow can be detected. It is confirmed that void fraction detection using the present method achieves successfully.