Ahmad Jamili

Production Modeling in the Eagle Ford Gas Condensate Window: Integrating New Relationships between Core Permeability, Pore Size, and Confined PVT Properties

Transport properties and mechanisms as well as phase behavior under nanoscale confinement exhibit deviations from their bulk behavior. This is due to the significant effect of molecule-wall interactions as well as molecule-molecule interactions in shale formations which are mainly characterized by nanopores. Consequently, the critical temperatures and pressures and transport properties of hydrocarbon mixtures under nanopores confinement are influenced strongly by fluid molecule-pore wall interactions. The effect of phase behavior on production from a shale gas condensate reservoir is studied where nanopores present either as the dominate storage region and when dispersed with pores with bulk behavior. The effect of pore size on phase behavior is considered by using modified critical properties for different pore sizes in the phase behavior calculations. Permeability, porosity, and mercury injection capillary pressure (MICP) tests are run on several Eagle ford core plugs. Using experimental results, an equation for estimation of mean pore size as a function of permeability and porosity is presented. A shale gas condensate reservoir with an Eagle Ford gas condensate as the reservoir fluid is modeled. The reservoir pressure, dew point pressure and temperature are 5000 psia, 3800 psia and 180 °F, respectively. Pore size distribution of one of the samples is used in the reservoir modeling. Based on MICP experiments and pore-throat size distribution, the pore volume of the reservoir was divided into five regions: bulk (pore sizes more than 50nm (10% PV)), 20-50nm (12% of PV), 12-20nm (29% of PV), 7-12nm (39% of PV), and less than 7nm (10% of PV). For each region, a specific permeability was assigned using the new developed correlation. Three different types of connectives between pores were considered: 1pore sizes from smallest to largest connected to the fracture in series, 2pore sizes from largest to smallest connected to the fracture in series, and 3completely random distribution. Results showed that by decreasing the pore size, dew point pressures decrease between 5 to 24%, fluid tends to behave as a dry gas and the two-phase region shrinks therefore condensate drop-out and near wellbore permeability impairment is reduced. After 15 years of production, condensate saturation around fracture is up to 7% less under confinement effects. Gas and condensate viscosities under confinement decrease 3-16% and 10-50% respectively. Confinement did not affect gas production significantly but condensate production increased more than 30%. Production analysis showed that Permeability is overestimated by 30% if bulk PVT is used instead of modified PVT with pore size. Phase behavior effect has a positive contribution to production while considering permeability variation with pore size has a negative impact on production. Connectivity type between different pore sizes has a pronounced effect and determines which of these factors has more impact on production. Introduction In the past decade, there has been a rapid growth in production from unconventional condensate and gas resources. Due to the importance of these low permeability reservoirs in condensate and gas production, a lot of research has been conducted on these types of resources. Modeling studies on unconventional resources indicate applying physics of fluid and flow behavior in conventional reservoirs under predict production from unconventional resources (Javadpour 2009; Swami, 2012). Therefore in simulation studies in order to match production data, core derived matrix permeability and/or Stimulated Reservoir Volume (SRV) are artificially increased (Swami, 2012). It has been observed that pore sizes of unconventional resources are in the range of 1-200 nm (Cipolla et al., 2009). Different previous studies show that the thermophysical properties of fluids under confinement deviate from its bulk value (Gelb,

Estimation of the effect of biomass moisture content on the direct combustion of sugarcane bagasse in boilers

Many of the large-scale biomass combustion systems for producing heat, hot water, or steam accept biomass fuels containing relatively large amounts of moisture. Dry biomass burns at higher temperatures and thermal efficiencies than wet biomass. Flame temperature is directly related to the amount of heat necessary to evaporate the moisture contained in the biomass, the lower the moisture content, the lower the amount of energy needed to remove the water and the higher the boiler efficiency. In this article, a simple predictive tool is developed to estimate boiler efficiency as a function of stack gas temperature and sugarcane bagasse moisture content. The method quantitatively illustrates the effect of moisture content on the performance of a thermochemical process, for the direct combustion of sugarcane bagasse in a conventional boiler. The results are found to be in excellent agreement with reported data in the literature with average absolute deviation being around 1%. The tool developed in this study can be of immense practical value for engineers to have a quick check on biomass moisture content on the boiler performance at various conditions without opting for any experimental trials. In particular, engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions.

A new method estimates TEG purity versus reconcentrator temperature at different levels of pressure in gas dehydration systems

There are several processes and principles for obtaining high triethylene glycol (TEG) purity in gas dehydration process. All methods are based on the principle of reducing the effective partial pressure of water in the vapour space of the glycol reboiler, and hence obtaining a higher glycol concentration at the same temperature. One of the most common methods for enhancement of the glycol concentration has been by means of pressure reduction in the reboiler. In this article a simple method is developed to estimate TEG purity as a function of reconcentrator (reboiler) temperature and pressure. The results are found to be in excellent agreement with reported data in the literature with average absolute deviation being around 0.05%. The tool developed in this study can be of immense practical value for engineers to have a quick check on TEG purity as a function of reconcentrator (reboiler) temperature and pressure at various conditions without opting for any experimental trials. In particular, engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions.

CALCULATING PSEUDO-STEADY-STATE HORIZONTAL OIL WELL PRODUCTIVITY IN RECTANGULAR DRAINAGE AREAS USING A SIMPLE METHOD

To determine the economical feasibility of drilling a horizontal well, engineers need reliable methods to estimate its productivity. In this work, a simple-to-use method is developed to rapidly estimate a pseudo-steady-state horizontal wells productivity. Estimations are found to be in excellent agreement with the reliable data in the literature, with average absolute deviation being less than 1%. The tool developed in this study can be of immense practical value for petroleum engineers to make a quick check on a pseudo-steady-state horizontal wells productivity at various conditions without opting for any field trials. The predictive tool is simple and straightforward, and it can be readily implemented in a standard spreadsheet program. The prime application of the method is as a quick-and-easy evaluation tool in conceptual development and scoping studies where horizontal wells are being considered. The method may also serve as a benchmark in numerical reservoir simulation studies.

Determination of the Density of Water Emulsions in the Crude Oil Dehydration Process

The salt elimination from produced crude oil is an important stage in oilfield processing and it is considered as a compulsory requirement in the oil industry. In most cases, salt is found a dissolved component in the brine phase in contact with oil. Different compositions of various salts might exist in the brine; however, sodium chloride (NaCl) has the highest fraction in the solution. The water existing in the crude oil is seen as very small drops dispersed in the bulk of oil. In the current study, a simple predictive strategy for density determination of aqueous salty solution in crude oil as a function of salinity (in vol% of sodium chloride concentration), temperature, and pressure is proposed through combination of an Arrhenius-type asymptotic exponential function and the relationship introduced by Spivey et al. (2004). The developed method predicts the amount of salt in the crude oil for temperatures up to 373 K, sodium chloride concentrations up to 250,000 ppm (25% by volume), and maximum pressure of 200 MPa, upon availability of the required input data. Estimations obtained from the proposed approach are found to be in very good agreement with the reported data in the literature so that the absolute error percentage varies in the range of 0.003–1.681%. The technique introduced in this research appears to provide reliable value for the oil engineers to attain a fast estimation of the salt content in the crude oil at various operating conditions without conducting laboratory tests. It is believed that the approach would be user-friendly without complicated computations for chemical and petroleum engineers and researchers. It can be also combined with existing thermodynamic software packages, resulting in an accurate and fast predictive model for practical applications.

Estimation of configuration factor for radiation from a rectangle to a parallel small element of surface lying on the perpendicular to a corner of the radiator

To calculate the radiant intensity at a point distant from a radiator, a geometrical or configuration factor must be used. If the temperature is known, then the emissive power can be calculated using the mean equivalent beam length, but before the radiant heat flux at a distance can be estimated, a configuration factor must be calculated. In this article a simple predictive tool is developed to estimate the configuration factor for a geometry including a receiving element lying on the perpendicular to one corner of a radiant rectangle. The results are found to be in excellent agreement with reported data in the literature with average absolute deviation being around 2%. The results can be used in follow up calculations to estimate heat fluxes on surfaces exposed to radiation. The tool developed in this study can be of immense practical value for engineers as a quick check on the configuration factor for a geometry including a receiving element lying on the perpendicular to one corner of a radiant rectangle without opting for any experimental trials. In particular, engineers would find the approach to be user-friendly with transparent calculations involving no complex expressions.