摘要:

The role of added inorganic salt on the thermal degradation of lignin was studied. The results were compared with the thermal analyses of two types of agricultural residues: rice straw with high silica content and bagasse with low silica. Compared to wood, thermal decomposition of such materials is faster, with a dual mechanism concept similar to wood. In general, the activation energy for rice straw is about 19.3 Kcal mol while that of bagasse is 33.4 Kcal mol. This proves that inorganic material either inherited or added changed the thermal activities of the lignocellu losic materials.

ISSN:0090-8312    

DOI:10.1080/00908319950015000

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

One of the most important features of solar panel manufacturing is the thermocapil lary convection of low-Prandtl-number fluid. This numerical modeling study is an effort to simulate the thermocapillary convection in a two-layer fluid system. A two-dimensional axisymmetric liquid column model is developed to obtain a quanti tative estimate of the thermocapillary convection velocities in a fluid with low Prandtl number encapsulated with viscous liquids such as silicone oil and eutectic salt. All simulations for the microgravity case are conducted using the finite element technique. The flow model is Newtonian, incompressible and interfacial tension gradients are linear. Interfacial deformation as a function of the temperature difference caused by the competing effects of fluid dynamic pressure and capillary pressure is reported for each sample, and the effect of encapsulant on this phenomenon is studied. The liquid column is more stable in the presence of an encapsulant.

ISSN:0090-8312    

DOI:10.1080/00908319950015019

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

A comparison of ten two-phase relative permeability models is conducted using experimental, semianalytical and numerical approaches. Model predicted relative permeabilities are compared with data from 12 steady-state experiments on Berea and Brown sandstones using combinations of three white mineral oils and 2 % CaCl2 brine. The model results are compared against the experimental data using three different criteria. The models are found to predict the relative permeability to oil, relative permeability to water and fractional flow of water with varying degrees of success. Relative permeability data from four of the experimental runs are used to predict the displacement performance under Buckley-Leverett conditions and the results are compared against those predicted by the models. Finally, waterflooding performances predicted by the models are analyzed at three different viscosity ratios using a two-dimensional, two-phase numerical reservoir simulator.

ISSN:0090-8312    

DOI:10.1080/00908319950015028

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

An experimental investigation was carried out with a new array of cement additives, replacing some of the currently used ones. In this study, the cement slurry pressure was monitored during the setting of the cement. Two time-cycles of cement expan sion and contraction were observed. This is due to the individual contribution of each component in the cement mixture. To obtain the optimum tightness of the cement, final contraction in the cycle is crucial for blockage of gas migration. Concentrations of the additives were obtained experimentally in this study for which the cyclic pressure behavior of the cement was optimized and the permeability reduced for the best final cement results. The parameters investigated in this study were as follows: pressure applied on the slurry with time, compressive strength, and permeability of the set cement. The major causes of the early microfractures are the incomplete cement-water reaction, low compressive strength of the set cement, and the sudden change in the hydrostatic pressure as the cement changes its phase from a liquid to a solid state. The fluid loss and free water content were measured and controlled for each sample. Three new cement additives were investigated; one was used to eliminate the microannulus with the pipe while the other two were used to eliminate the microfrac tures within the cement body. An appropriate amount of Ironite Sponge concentra tion eliminated the microannulus with the pipe. The optimum amount of synthetic rubber powder needed during the optimum two-cycle expansion-contraction process was also obtained under reservoir conditions. The Anchorage clay concentration in the mixture that migrates for a limited time minimizes the cement body pores. This concentration can also be optimized. This paper reports the appropriate amounts of X-C polymer, Anchorage clay, Ironite Sponge, and synthetic rubber needed to optimize the compressive strength and eliminate both microfracture and microannu lus. There are certain limits to the amount and type of synthetic rubber powder for which microfractures are eliminated. The article reports an experimental approach that can be used to eliminate gas migration through a cement design that is environmentally safe and inexpensive, using recyclable materials.

ISSN:0090-8312    

DOI:10.1080/00908319950015037

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

Over two-thirds of the original oil remains unrecovered in an oil reservoir, after primary and secondary recovery methods have been exhausted. Many chemically based oil recovery methods have been proposed and tested in the laboratory and field. Indeed, chemical oil recovery methods offer a real challenge in view of their success in the laboratory and lack of success in the field. The problem lies in the inadequacy of laboratory experiments on one hand, and the very limited knowledge of the reservoir characteristics on the other. Field test performances of polymer, alkaline, and micellar flooding methods are examined for nearly 50 field tests, results for which are tabulated. The oil recovery performance of micellar floods is the highest, followed by polymer floods. Alkaline floods have been largely unsuccessful. The reasons underlying success or failure are examined.

ISSN:0090-8312    

DOI:10.1080/00908319950015046

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor

摘要:

Foam diversion is a promising method for diverting acid to formations that would otherwise be bypassed. Even though numerous surfactants are being used by the stimulation service companies, there is no reliable or easy-to-use method for screening them. A standard method is proposed in this article. The method is validated with laboratory diversion tests conducted under high-pressure conditions using Berea sandstone cores. Seven different prescreened surfactants were selected for testing the proposed method. Several screening methods have been proposed in the past, including static tests and porous media tests. However, they are neither dependable nor standard. Therefore, a new screening technique was developed in which optimum values of parameters, such as ultimate liquid recovery, recovery at breakthrough, cumulative liquid produced to cumulative air produced ratio (L/A), liquid injection pressure ratio (P2/P1), and breakthrough time during the porous media tests, were used to select the surfactants that are most likely to help diversion. Based on the new surfactant screening criteria, the overall ranking (from best to worst) of the seven surfactants used in this article was as follows: S3 S8 S2 S6 S4 S1 S5 Among these seven surfactants, four surfactants were selected for further evaluation under high-pressure diversion conditions. Diversion tests were conducted using four different permeability contrast values. This was the first time a screening criterion was tested against diversion results that were performed under high pressure and low-permeability conditions. The ranking of the screening criterion held true for the diversion tests. In order to validate the proposed screening criterion further, foam diversion results were obtained in the presence of residual oil. It was found that the presence of residual oil changed the ranking in the high-pressure diversion case. In the presence of oil, the ranking of the diversion tests was exactly the same as that determined by the screening criterion. The screening method is, therefore, proposed as a standard for selecting surfactants for diversion purposes.

ISSN:0090-8312    

DOI:10.1080/00908319950015055

出版商:Informa UK Ltd    

年代:1999

数据来源: Taylor