Natural Gas engineering

Questo lavoro è frutto del tirocinio “Engineering and Energy Economics” tenuto dal
Professor Renato Urban, con la super visione della Professoressa Luisa Ferroni, con lo scopo
di fornire gli strumenti necessari per conoscere tutti gli aspetti del ciclo economico dell’energia.

This research concludes that, natural gas dewatering techniques consists of; absorption, adsorption, condensation and membrane separation. The criteria for selecting the dewatering method to use, depends on the dew point requirements and the dewatering capacity. Tri-ethylene Glycol (TEG) dewatering method was chosen to be the best because it can provide the desired dewatering capacity, low cost of operation and low energy consumption. We can achieve a water content of 6lb/MMSCFD-7lb/MMSCFD which is the standard water content in natural gas.

Compressibility factor (z-factor) of gasses is a thermodynamic property used to account for the deviation of real gas deviation from the ideal gas behavior.  The best correlations for this factor given by Hall and Yarborough, Dranchuk & Abou-Kassem and Dranchuk, Purvis & Robinson are based on nonlinear equation of state requiring iterative solution.

It is not uncommon for nonlinear equations to have multiple roots, hence, Newton-Raphson often fail to converge or converges on the undesired root of these equations. This unstable behavior of iterative procedure requires that the initial guess is set close to the desired root to ensure convergence.

Here we examine the residual equations of the reduced densities of these correlations and set the criteria for the determination of the initial guess as function of the reduced temp...

Formation damage is a major problem experienced in the operation and development of petroleum reservoir. Its occurrence, occasioned with the release of particles, water, emulsions or scales, hitherto impairs the hydrocarbon delivery/transport system. Formation or skin damage impedes flow of fluids into the wellbore and cause low permeability, hence reducing the productivity of the wells. The production loss directly reflects the economic loss due to formation damage. In the extreme, damage may cause the Well to be uneconomic and be shut-in. The objectives of this project was to determine Stimulation C andidate for three (3) Wells in the Niger Delta Oilfield, using the R ratios, stimulate the candidate wells and make comparison between the wells with regard to the Pre-Stimulation

The determination of quantity of gas loss from an underground natural gas storage system was presented. A system equation was propounded for the determination of the quantity of gas loss from an underground gas storage system. The variable parameters that the equation considered were the initial and final pressures, initial and final temperatures and initial and final compressibility factors of the storage gas while the constant was 35.3021 which is a factor for relating the pressure, temperature and compressibility factor of the gas at standard conditions. A Microsoft visual basic program was also developed based on the equation which can determine the quantity of gas loss from an underground natural gas storage system.
Key words: system, quantity, gas, loss, reservoir, aquifer, salt, cavern, pore, volume, underground, equation, storage, pressure, temperature, compressibility, factor.

Formation damage is a major problem experienced in the operation and development of petroleum reservoir. Its occurrence, occasioned with the release of particles, water, emulsions or scales, hitherto impairs the hydrocarbon delivery/transport system. Formation or skin damage impedes flow of fluids into the wellbore and cause low permeability, hence reducing the productivity of the wells. The production loss directly reflects the economic loss due to formation damage. In the extreme, damage may cause the Well to be uneconomic and be shut-in. The objectives of this project was to determine Stimulation Candidate for three (3) Wells in the Niger Delta Oilfield, using the R ratios, stimulate the candidate wells and make comparison between the wells with regard to the Pre-Stimulation and Post-Stimulation analysis. An analytical method was used to calculate Productivity Index, PI; Permeability, K; Skin, S; Production Rate, q, R-Ratio and Pressure Drawdown, ΔP using data from Pressure build...

Accurate estimation of two-phase compressibility factor is of great importance in predicting the performance of a gas condensate reservoir using the material balance approach. Over the years, several correlations for estimating gas compressibility factor have been developed. Some of these correlations are; the Standing and Katz, Rayes etal, Dranchuk and Abou-Kassem, Brill and Beggs’ and Hall-Yarborough’s correlations.
However, these correlations have not been so successful in predicting the compressibility factor of gas reservoir fluids in the two-phase region (below dew point pressure) and this explains why the industry still relies on the expensive and time-consuming constant volume depletion (CVD) approach. Therefore, this paper presents two different correlations for estimating two-phase compressibility factor using stochastic and robust gradient-based Newton-Raphson optimization algorithm. The first correlation presents the two-phase Z-factor as a function of pseudo-reduced pressure, pseudo-reduced temperature and the specific gravity. The second correlation on the other hand presents the two-phase Z-factor as a function of the
single-phase Z-factor (obtained using Standing and Katz approach). Both correlations were developed using over 50 constant volume depletion (CVD) data of reservoir fluid samples obtained from gas condensate reservoirs around the world. Furthermore, in order to develop these correlations, two different models were proposed and the heptane-plus (C7+) and acid gas fractions were accounted for using the Sutton’s and Lee Kesler correlations respectively. Moreover, using the expected values of the pseudo-reduced pressure, pseudo-reduced temperature, specific gravity and single-phase Z-factor (all obtained using appropriate probability distributions) as the input variables, the optimum values of the models’ fitting parameters that minimize the sum of squares of the errors (SSE) were obtained using the stochastic and robust optimization algorithm(an algorithm obtained from Taylor series expansion of the error function and implemented on Octave programming language for the purpose of this study). Finally, having developed the correlations
using 70% of the available data, the performances of these correlations were evaluated using 30% of the available data and the results obtained shows that these correlations outperform other pre-existing correlations.

Formation damage is a major problem experienced in the operation and development of petroleum reservoir. Its occurrence, occasioned with the release of particles, water, emulsions or scales, hitherto impairs the hydrocarbon delivery/transport system. Formation or skin damage impedes flow of fluids into the wellbore and cause low permeability, hence reducing the productivity of the wells. The production loss directly reflects the economic loss due to formation damage. In the extreme, damage may cause the Well to be uneconomic and be shut-in. The objectives of this project was to determine Stimulation Candidate for three (3) Wells in the Niger Delta Oilfield, using the R ratios, stimulate the candidate wells and make comparison between the wells with regard to the Pre-Stimulation and Post-Stimulation analysis. An analytical method was used to calculate Productivity Index, PI; Permeability, K; Skin, S; Production Rate, q, R-Ratio and Pressure Drawdown, ΔP using data from Pressure build...

Estimation of the storage capacity of an underground gas storage salt formation was presented. An equation was propounded for estimating salt formation storage capacity which was based on the mass of salt produced from the formation. The propounded equation also introduces a coefficient termed Salt Formation Storage Coefficient otherwise called Muon Coefficient which is read from a chart called the Muon Chart. The applicability of the Muon Chart and thus the equation was based on certain assumptions which were listed in the Theory. The single limitation of this new equation was also shown in the Theory of this work. This new equation is termed Mass of Salt Equation because it makes use of the mass of salt produced from the formation in estimating the storage capacity of the salt formation. The Mass of Salt Equation was actually applied to compute the storage capacity of a salt formation, Formation AN-01, located South-East Nigeria. A Microsoft visual basic program was also developed based on the Mass of Salt Equation that can estimate salt formation storage capacity.
Key words: underground, natural gas, storage, salt, formation, capacity, mass,    equation, coefficient, Muon, chart.

Accurate estimation of compressibility factor is of great importance in predicting the performance of gas reservoirs using the material balance approach and also in the designing of gas pipelines and flowlines. Over the years, several correlations for estimating gas compressibility factor have been developed. However, these correlations have not been so successful in predicting the compressibility factor for High pressure-High temperature (HPHT) reservoirs and this explains why the industry still relies on the expensive and time-consuming constant volume depletion (CVD) approach. Therefore, this paper presents a correlation suitable for estimating the compressibility factor for high pressure-high temperature (HPHT) reservoirs using stochastic and robust optimization approach with Gaussian probability distribution. The results obtained shows that the correlation outperforms other pre-existing correlations within the range of pressures and temperatures considered.

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