Showing papers by "Anirbid Sircar published in 2015"

Geothermal exploration in Gujarat: case study from Dholera

Abstract: Utilization of Geothermal resources is an alternate, sustainable energy, which needs to be harnessed in India . Exploration of the resource is the first step to understand potential leads and prospects in the subsurface. An attempt has been made to understand the subsurface picture using geoscientific data, for example, Gravity survey, Landsat imagery, magnetotelluric (MT) survey and water chemistry. Dholera, Gujarat is a potential site for geothermal exploration and exploitation, which is the chosen study area. Dholera also falls under proposed Delhi Mumbai Industrial Corridor Development Corporation Limited (DMICDC), making it a suitable candidate for setting up geothermal power plant in future. The energy potential of prospects identified in Dholera through the above-mentioned studies may help industries in creating geothermal power plant and utilization of energy in space heating & district heating/cooling. Dholera is located 30 km away in southwest direction from Dhandhuka village of Ahmedabad district and 60 km away in north direction from city of Bhavnagar (Fig. 1c). Hot springs exist over gravity high, which is the surface manifestation of deep and shallow water sources. Present research focuses on vegetation index for the study area and land surface temperature; alteration of water chemistry in association with subsurface rocks and understanding of subsurface models using Gravity and MT surveys. 2D geoelectric maps and gravity contours have helped in understanding the aquifer geometry and dimensions. 2D resistivity sections depict the aquifer connectivity across Dholera at depths of 3 and 4 km. MT survey suggests that the volcanic rocks are exposed at places. However, it also depicts locations where sediments exist and are sandwiched between basaltic lavas. MT model is also constrained using residual gravity data and corroborates well with the MT data. Present study will help in harnessing the geothermal energy entrapped within the geobodies and also to understand connectivity between the geobodies. These studies were carried out one after the other, to delineate geothermal reservoir and increase the probability of success. The best location for further exploration and exploitation by drilling has been identified by integration of all these methods.

Overview of Geothermal Surface Exploration Methods

Abstract: The recent increase in conventional fuel prices has resulted in an increase in the interest innatural sources of energy such as geothermal energy. Geothermal energy is the vast reservoir of heat energy in the earth’s interior , whose surface manifestation are volcanoes, fumaroles, geysers, streaming grounds and hot springs. The exploration of geothermal resource in India is in nascent stage and that motivated to look into the aspect in detail. Commercial exploitation for generation of electricity is yet to take place in India. The scientific disciplines commonly involved are geology, geochemistry, and geophysics. This paper shows various techniques which are used for exploration of geothermal energy in Indian context, which preliminarily deals with hot springs, as there are no major active volcanoes or other surface manifestations present in India. Initially, it focuses on primary geological studies like remote sensing and geochemical analysis of water from hot springs to delineate prospective zones. After short listing prospective geothermal sites, geophysical methods such as magnetotellurics, gravity, magnetic and seismic methods are used. The entire exploration method is analogous to oil and gas exploration where the practice is to narrow down the sites based on the probability of success. It emphasizes on accuracy of surface exploration methods so that the risk can be minimized while practicing subsurface exploration methods such as drilling which requires huge capital investment.

Hydrocarbon resource estimation: a stochastic approach

Abstract: 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

Crude characterisation on rheometer for flow assurance

Abstract: Flow assurance basically involves ensuring the fluid flow as intended in a pipe or a well. Wax deposits begin to form when the temperature in the wellbore falls below wax appearance temperature (WAT). This condition leads to reduced production rates and larger pressure drops. Wax problems in production wells are very costly due to production down time for removal of wax. To improve the efficiency of the transportation and the crude oil quality, prevent blockage, preventing and removing wax is very important. In order to develop a solution to wax deposition, it is essential to characterize the crude oil and study phase behavior properties. This paper summarizes the results of the various experiments conducted using crudes of different wells. The experiments conducted during this study include measurement of viscosity as a function of time at different shear rate. It also shows the effect of pre-treatment on crude oil. The paper also discuss about the comparison between use of xylene and pour point depressants (PPD) at different concentration on crude oil. INTRODUCTION One of the major problems confronting the petroleum industry is the untimely blockage of oil arteries due to deposition of heavy organics (asphaltene, resin, paraffin wax) present in the oil. The continued deposition of heavy organics results in reduced area which may lead to plugging of pipe cross section. This can result in huge economic loss. The phenomena may also take place in the formation near the wellbore. (Adesina F., et al., 2010) Flow Assurance addresses the issues of deposition of heavy organics during entire petroleum extraction process from the reservoir to surface process facilities and beyond. The precipitation of waxes from petroleum mixtures at low temperatures may cause different problems during production, transport in pipelines, or storage. Such problems are well-known within the petroleum industry and the best way to deal with such problems is to predict its occurrence and act preventively. WAX Waxes are defined as the relatively high molecular weight C18-C60 alkanes, which are deposited as solids when there is a change in thermodynamic equilibrium, such as the temperature falls below the cloud point. Wax mainly consists of n-alkanes and iso-alkanes. This can be classified into two type macro crystalline and micro crystalline. Macro crystalline waxes (Paraffinic waxes) are iso-paraffins and naphthenes within the range of C18 to C36. Micro crystalline waxes are mainly n-alkanes within the range C30 to C60. (Adesina F., et al., 2010) The critical point in the rheology of waxy crudes is cloud point. Above the cloud point, flow is Newtonian and when the temperature of the crude oil drops below the cloud point the solubility of wax fractions is significantly reduced to cause wax precipitation which changes the flow behaviour to non-Newtonian. When the rheology of the fluid changes, it is observed that there is ten-fold or more increase in viscosity. This results in additional pressure drop and decreases pipeline efficiency because of potential plugging. (Elsharkawy, A. M., et al., 1999) Figure 1: Wax plug in wellbore on platform in North Sea. (Labes-Carrier, C., et al., 2002) The viscosity is one of the most important physical properties affecting the flow behaviour of crude oil. Investments of millions of dollars are committed to the transport of crude oil in pipelines designed. The return on the investment may disappear if the flow rate in a given pipeline is not as high as anticipated due to lack of understanding of the factors affecting the oil's viscosity. Figure 1 shows the wax plugging in wellbore. The presence of wax crystals leads to a wide range of non-Newtonian characteristics including yield stress, pseudo plasticity (shear thinning) and time dependency. The industrial cost involved in preventing wax deposition is high, and the petroleum industry is always looking for a cheap and effective additive to control the problem. (Wardhaugh, L. T., and Boger, D. V., 1988) Figure 2 shows the severity of wax deposition resulting in clogging of pipeline. The viscosity is one of the most important physical properties affecting the flow behaviour of crude oil. Investments of millions of dollars are committed to the transport of crude oil in pipelines designed. The return on the investment may disappear if the flow rate in a given pipeline is not as high as anticipated due to lack of understanding of the factors affecting the oil’s viscosity. Figure 1 shows the wax plugging in wellbore. The presence of wax crystals leads to a wide range of non-Newtonian characteristics including yield stress, pseudo plasticity (shear thinning) and time dependency. The industrial cost involved in preventing wax deposition is high, and the petroleum industry is always looking for a cheap and effective additive to control the problem. (Wardhaugh, L. T., and Boger, D. V., 1988) Figure 2 shows Wax deposited