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Abstract There are well-known correlations and technologies which estimate the flow rate in dry gas wells. Measuring the surface rate is challenging, especially when there is no measuring equipment. Nevertheless, the choke equation and some well-known correlations can provide an estimate of the flow rate whether the gas at the surface is single-phase or multi-phase but with a certain accuracy and basic assumptions. Another tool to estimate flow rate is the surface venturi meter, which is being used for dry gas wells. In this paper, a new method was established to calculate and verify measured gas flow rates. An empirical correlation was developed to calculate the real-time flow rate in dry gas wells at the surface utilizing the most appropriate parameters: upstream flowing wellhead pressure, downstream flowing wellhead pressure, upstream flowing wellhead temperature, and choke size. The proposed equation consists of a coefficient for each individual parameter which is fine-tuned in the equation using an advanced non-linear regression method. Moreover, a comparison between calculated rate using the new method and measured gas rate shows accurate values with an average absolute error of 11%. A comparison between the measured rate, Beggs equation, and Gilbert's correlation showed highly deviated values, with an average absolute error of 60% for Beggs's and more for Gilbert's. It is worth highlighting that there is a major difference between the new correlation and Beggs' equation or any other that the new correlation is customized for the selected field. Another difference that the new correlation uses real and field data whereas the Beggs's equation and Gilbert's correlation used experimental data which might not be applicable to the selected field. Hence, this correlation provides a matching trend to the measured flow rate from venturi readings in dry gas wells. The new correlation would enable production engineers to enhance their rate validity and furthermore it might replace the meter readings when the meter device become defective. Also, this correlation is aimed at calculating the gas flow rate in real-time measurements of wellhead parameters which enhances the monitoring of the well's performance on a real-time basis.
Abstract The critical and subcritical multiphase flow through wellhead restrictions of a prolific oil field in the Middle East is investigated and two sets of new correlations are presented. The first set of correlations is developed by using "40" field tests representing critical flow conditions. The second set of correlations is based on "139" field tests representing subcritical flow conditions of gas-liquid mixtures through wellhead chokes. For the critical multiphase flow condition, the predicted oil flow rates by the new set of correlations are in excellent agreement with the measured ones. The absolute average percent difference (AAPD) is between "1.88" and "4.37", and the corresponding standard of deviation (SD) is between "2.52" and "6.52". These results are found to be statistically superior to those predicted by other published correlations considered in this work. During the subcritical gas-liquid flow conditions through surface chokes, the accuracy of oil flow rates predicted by the new set of correlations seems to be sensitive to the type and size of the choke being used. For Cameron LD type and 144/64 -inch choke, the oil flow rates predicted by the proposed correlation are superior to those predicted by other methods available in the literature, with AAPD of "8.5". However, for smaller choke sizes of 96/64 and 64/64 -inch, the oil flow rates predicted by the new correlations and other methods are found to be close to each other. For Cameron F type and 144/64 -inch choke size, the oil flow rates predicted by the new correlation are closely matched by those predicted by other published methods, with AAPD of "13.7". For smaller choke sizes of 80/64 and 64/64 -inch few field tests are available and the predications of all methods, including the proposed ones, show similar statistical results. The above findings for Cameron F choke also seem to apply to Beaned wellhead assemblies for this particular oil field. Introduction The main problems associated with multiphase flow through restrictions are calculation of (i) pressure upstream from choke, (ii) liquid production rate, or (iii) choke diameter. Thus, various developments have been published that present theory and correlations for describing simultaneous liquid and gas flow through surface restrictions. Most of these correlations are for critical flow across the choke and very little work has been done for subcritical flow. Fonseca (1972) showed that the approach used by most investigators may be classified into one of the following:(i) Empirical correlations from field or laboratory data. (ii) Empirical correlations using dimensional analysis to select and group the most important variables. (iii) Theoretical approaches applying mathematical analysis to a simplified physical model with development of equations. Beggs and Brill (1975) stated that the two-phase flow through restrictions may fall into one of the following categories:Critical flow: this occurs when the fluid flows through the choke at velocities greater than that of sound in that fluid. To satisfy this condition in oil field work the upstream pressure must be approximately twice the downstream pressure. Subcritical flow: this occurs when the velocity of the fluid is less than the velocity of sound in that fluid.
Abstract Sachdeva's multiphase choke flow model has capabilities of predicting critical-subcritical boundary and liquid and gas flow rates for given upstream and downstream pressures. Although this model was shown to be accurate by Sachdeva et al. in their original paper using laboratory and field data, inaccuracy of the model has been found in other field applications. It is highly desirable for production engineers to find the applicability of this model when it is applied to gas condensate wells. In this study, the accuracy of the Sachdeva's choke model was evaluated using data from oil and gas condensate wells in Southwest Louisiana. Comparisons of the results from the model and field measurements indicate that Sachdeva's choke model generally under-estimates gas and condensate flow rates. Based on measurements from 239 gas condensate wells it was found that the model under-estimates gas rate and liquid rate by as much as 40% and 60%, respectively. The model also failed to calculate mass flow rates for 48 condensate wells where relatively low-pressure differentials at chokes and high-flow rates were observed. The investigation further went on to improve the performance of Sachdeva's choke model. It was found that the error of the model could be minimized using different values of choke discharge coefficient (CD). For gas condensate wells, the error in gas flow rate calculations can be minimized using CD = 1.073. However, the error in liquid flow rate calculations for condensate wells is minimum when CD = 1.532. Introduction Computer technology has been widely used for simulation of petroleum production network today. The production network consists of reservoirs, wellbore equipment, and surface equipment including chokes, flow lines, production manifolds, and distilation facilities such as separators. The production network simulation has gained strong momentum due to fast advances in computing technology in the past five years. Wellhead chokes are special equipment used in energy industry to control fluid production rates from wells, to maintain stable pressure downstream from the choke, and to provide the necessary backpressure to a reservoir to avoid formation damage from excessive drawdown. Because oil and gas production rates are extremely sensitive to choke size, accurate modelling of choke performance is vitally important for petroleum engineers in oil production simulation.
This model which assumes a polytropically compressible homogenous flow, is reducible to the familiar single phase orifice flow equations. A derivation for the limiting case of isothermal compressible flow is also giveno These derivations are flexible enough to be used for either critical or subscritical multiphase flow. Comparison of the proposed model with existing multiphase orifice flow models shows a good agreement. The paper also presents a simple procedure and examples to illustrate the applicability of the model to critical and subscritical flow metering. SPE 17 17 4. 2. INTRODUCTION The.flow o.r.fluids through delilJraLu re:::;LrleLluu:::; such as orifices and chokes is commonly used in the oil and gas industry for flow metering and evaluation of pressures. Practically-all flowing wells utilize some surface restriction in order to regulate.