Organic and inorganic flocculants are used in treatment of water and industrial effluents. Polymeric flocculants, synthetic as well as natural, because of their natural inertness to PH changes, low dosage, and easy handling, have become very popular in industrial effluent treatment. It has been established in the authors' laboratory that by grafting polyacrylamide branches on rigid backbone of polysaccharides, the dangling grafted chains have easy approachability to contaminants in effluents. Thus grafted polysaccharides are very efficient, shear stable and biodegradable flocculants. They also exhibit turbulent drag reducing characteristics. Among grafted guar gum, xanthan gum, carboxymethyl cellulose, and starch, grafted starch performs the best. Starch consists of amylose (a low molecular weight linear polymer) and amylopectin (a high molecular weight, branched polymer). The grafted amylopectin is found to be the best flocculant for various kinds of industrial effluents, providing credibility to the above‐cited model. In the present paper, the details about grafted polysaccharides as turbulent drag reducers and flocculants are given, along with their applications.

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The Tripura state went through extensive geological tectonics that resulted in the creation of complex structural styles with different fault types, lineaments, and plate boundaries, which in turn caused possible zones with over-pressured formations characterized by higher seismic amplitude signatures. Without accurate estimates of pore pressures, drilling through these hazardous zones is very troublesome and could jeopardize the whole drilling rig site. Pore pressures are easily predicted for sediments with normal pressure gradient. The prediction of pore pressure for the abnormally pressured (i.e., overpressured) sediments is more difficult and more important. Understanding of the pore pressure is a requirement of the drilling plan in order to design a proper casing program. With balanced drilling mud, overpressured formations, and borehole instability will be effectively controlled while drilling and completing the well. Well control events such as formation fluid kicks, loss of mud circulation, surface blowouts, and subsurface kicks can be avoided with the use of accurate pore pressure and fracture gradient predictions in the design process. In this study, transform models using modified Eaton's method were used to predict pore pressures from seismic interval velocities. Corrected two-way travel times and average velocity values for 28 sorted common depth points were input into the transform for pore pressures prediction predicted pore pressures show a reasonable match when plotted against formation pressure data from the offset wells namely AD-4 trend, Agartala Dome-6. Ambasa trend, Kathalchari trend, Kubal, Masimpur-3, Rokhia structure-RO1, and Tichna structure-TI1. In this study, it is observed that overpressure starts at shallow depths (1,482-2,145 m) in synclinal section while in flank section it starts deeper (2,653-5,919 m) in Atharamura anticline. It is also observed that the most of wells showing pressure match are located in the western side of the Atharamura. The maximum predicted pore pressure gradient observed in this study is 1.03 psi/feet in both synclinal and flank sections of Atharamura anticline. Based on our observations, it is interpreted that Tripura region is characterized by single pressure source and the pressure is distributed evenly in all the anticlines in this region.

Genetic algorithm has been used in various applications including reserve estimations in oil and gas industry for the last few decades. It is an effective stochastic inversion technique for optimization problems. The oil and gas industry is a risk based industry due to lot of uncertainties associated in each reservoir parameter used during the reserve estimation process. Detailed analysis of input data is very much important, either for the pre-bid evaluation or after the discovery of hydrocarbons. In this paper, stochastic approach in hydrocarbon resource estimation has been discussed. The algorithm starts with development of initial population and evaluation of the same. In the second step a fitness value is assigned to each individual. The best fit parents are then selected and by crossover and mutation of new populations are generated. The same process is continued until the optimum solution is reached. The efficacy of the algorithm is tested on real data set of seismic and petrophysical data from Cambay basin. The outcome is a range of resource estimates with various probability values.

Water production in gas and oil wells is one of the major problems faced by the petroleum industry. Polymers and gels can be efficient materials for controlling excessive water production in gas and oil wells. The injection of gelant solutions into the near-wellbore formation can reduce the permeability of the formation to water much more so than to oil. Such gelants are known as relative permeability modifiers. In this experimental study, tetramethylorthosilicate (TMOS) has been used as the oil soluble gelant. TMOS is soluble in the oil phase, and reacts with water to form a semi-solid gel that is capable of modifying the permeability of the rock. As the water is transformed into gel, the permeability of the medium to water is reduced. Due to the increase in volume of the "water phase", the oil permeability is reduced to a lesser extent. A series of static and dynamic gelation and flow experiments have been performed in test tubes. These were followed by flow tests conducted in transparent glass micromodels to determine the end-point relative permeability for oil and water before and after gelant injection. Our results show that the gel formation depends on the concentration of the gelant in the oil phase, the oil/water ratio, the amount of total gelant solution injected, and the time of flow of the gelant solution into the water phase. It was observed that the volume of gel obtained after gelation increases as the TMOS concentration increases, at a fixed oil/water ratio. The degree of permeability reduction for both oil and water is directly related to the amount of gelant injected. The results we have obtained can be used for pre-screening the efficiency of TMOS treatments. Introduction An increase in water percentage during the production of crude oil from oil and gas reservoirs increases the production costs, and also creates water disposal problems. This problem has consequently attracted the interest of many researchers in the search for methods of reducing water production. Several methods have been used to control water production by reducing the relative permeability to water while avoiding, to the extent possible, any reduction in the relative permeability to oil. One approach has been to inject polymer solution into the production well, along with a cross-linker1–6. The polymer solution and the cross-linker then react to form an annulus of gel around the production well. Once formed, the cross-linked gel is retained within the reservoir rock. This gel has the effect of modifying the flow of the two phases, oil and water. Hence, these polymers/gels are known as known as relative permeability modifiers (RPM), and the phenomenon they induce is known as disproportionate permeability reduction (DPR)1–6. Ideally, the aim of the treatment is to reduce the effective permeability for water flow, with no reduction in oil permeability. Such treatments may lead to significant reduction in water production, and hence a reduction in production costs. Sodium or potassium silicate solutions have been used to form totally blocking gels within the reservoir. Recently, organically modified silicates have been found to produce an effective gel that can modify the relative permeability of the reservoir rock7–9. Tetramethylorthosilicate (also known as tetramethoxysilane, or TMOS) is one of the most widely known alkoxides, and can be hydrolyzed and condensed under relatively wide range of conditions to form a rigid, porous gel.