Analysis of Maximum Liquid Carrying Capacity Based on Conventional Tubing Plunger Gas Lift

China’s unconventional gas fields have a large number of low-productivity and low-efficiency wells, many of whichare located in remote and environmentally harsh mountainous areas. To address the long-term stable productionof these gas wells, plunger-lift technology plays an important role. In order to fully understand and accurately graspthe drainage and gas production mechanisms of plunger-lift, a mechanical model of plunger-liquid column uplift inthe plunger-lift process was established, focusing on conventional plunger-lift systems and representative wellboreconfigurations in the Linxing region. The operating casing pressure of the plunger-lift process and the calculationmethod for the maximum daily fluid production rate based on the work regime with the highest fluid recovery ratewere determined. For the first time, the critical flow rate method was proposed as a constraint for the maximumliquid-carrying capacity of the plunger-lift, and liquid-carrying capacity charts for conventional plunger-lift withdifferent casing sizes were developed. The results showed that for 23/8 casing plunger-lift, with a well depth ofshallower than 808 m, the maximum drainage rate was 33 m3/d;for 27/8 casing plunger-lift, with a well depth ofshallower than 742 m, the maximum drainage rate was 50.15 m3/d;for 31/2 casing plunger-lift, with a well depthof shallower than 560 m, the maximum drainage rate was 75.14 m3/d. This research provides a foundation for thescientific selection of plunger-lift technology and serves as a decision-making reference for developing reasonableplunger-lift work regimes.

Influence of wellhead pressure and water cut in the optimization of oil production from gas lifted wells

The worldwide increase in energy demand necessitates the development and optimization of marginal oil fields for sustenance.In this regard,effective and economic production of fluids are heavily relied upon the artificial lift techniques as the reservoir's natural energy may not be able to deliver the fluids to the surface.Gas lift is a widely practised and successful method that is suitable for rejuvenating the oil production from such fields.In this study,the influence of critical parameters like water cut,wellhead pressure(WHP)and gas-lift gas injection rate on the output from a gas lifted well was analysed.A significant reduction in the oil production was observed with the increase in water cut.For a fixed gas injection rate of 1 Mmscf/day,the production decreased by 26.90%when the water cut increased from 15%to 30%and further by 50.80%when the water cut reached 45%.An increase in the gas injection rate from 1 Mmscf/day to 8 Mmscf/day resulted in an increase in the production rate by 29.21%,40.48%and 56.56%for 15%,30%,and 45%water cut conditions,respectively.It was observed that there is a drop in the oil rate with the increase in WHP for a constant gas injection rate.An increase in the WHP from 100 psi to 300 psi resulted in a drop in the oil production rate by 11.01%,11.78%and 12.74%for 15%,30%and 45%water cut conditions,respectively.The study sheds light on the significance of optimizing the critical parameters to maximize the production from a well,with severely affected productivity,using a continuous gas lift system.

A novel model for predicting the temperature profile in gas lift wells

One of the most common methods for calculating the production oil rate in a gas lift well is nodal analysis.This manner is an accurate one,but unfortunately it is very time consuming and slow.In some modern studies in petroleum engineering such as close loop control of the wells this slowness makes it impossible to have an online optimization.In fact,before the end of the optimization the input parameters have changed.Thus having a faster model is necessary specially in some of the new studies.One of the sources of slowness of the nodal analysis is the temperature profile estimation of the wells.There are two general approaches for temperature profile estimation,some like heat balance are accurate but slow.Others,similar to linear profile assumption are fast but inaccurate and usually are not used commonly.Here,as a new approach,a combination model of heat balance and linear temperature profile estimation has represented which makes the nodal analysis three times faster and it is as accurate as heat balance calculations.To create this,two points(gas injection point and end of tubing)are selected,then using heat balance equations the temperature of those two points are calculated.In normal nodal analysis the temperature of each wanted point in the well is estimated by heat balance and it is the source of slowness but here just two points are calculated using those complex equations.It seems that between these points assuming a linear temperature profile is reasonable because the parameters of the well and production such as physical tubing,and casing shape and properties and gas oil ratio are constants.But of course,it still has some deviation from the complete method of heat balance which using regression and assigning a coefficient to the model even this much of the deviation could be overcame.Finally,the model was tested in various wells and it was compared with the normal nodal analysis with complete heat balance models.Results showed that the new model is as accurate as normal heat balance but three times faster.

Computational fluid dynamic(CFD)simulation of pilot operated intermittent gas lift valve

To design an efficient intermittent gas-lift installation,reliable information is needed in the performance of all process components,from the outer boundary of the reservoir to the surface separators.The gas lift valve is the one critical component that affects the design of the whole system.In intermittent producing system,the pilot gas-lift valve is extremely used to control the point of compressed gas entry into the production tubing and acts as a pressure regulator.A novel approach using computational fluid dynamics simulation was performed in this study to develop a dynamic model for the gas passage performance of a 1-in.,Nitrogen-charged,pilot gas-lift valve.Dynamic performance curves were obtained by using Methane as an injection gas with flow rates reaching up to 4.5 MMscf/day.This study investigates the effect of internal pressure,velocity and temperature distribution within the pilot valve that cannot be predicted in the experiments and mathematical models during the flow-performance studies.A general equation of the nonconstant discharge coefficient has been developed for 1-inch pilot valve to be used for further calculation in the industry without using CFD model.The developed model significantly reduces the complexity of the data required to calculate the discharge coefficient.

Computational fluid dynamic(CFD)modelling of transient flow in the intermittent gas lift

A computational fluid dynamics model(CFD)is developed for intermittent gas lift techniques.The simulation is conducted for a test section of 18 m vertical tube with 0.076 m in diameter using air as injection gas and oil as a formation fluid.The results obtained from the CFD model are validated with the experiment results from the literature.The current study shows that computational modeling is a proven simulation program for predicting intermittent gas lift characteristics and the transient flow parameters that are changing with time and position in the coordinate system.The model can predict the slug velocity behavior for different injection pressure.The slug velocity profile shows three regions;the first region is the rapid acceleration at the initial time of injection,the second region shows the nearly constant velocity until the slug reaches the surface and the third region is again the rapid acceleration when the liquid starts to produce.Also,the results obtained from this model show that as the gas injection pressure increases,the liquid slug velocity increase,and the region of the constant velocity decrease.The effect of the injection time on the liquid production rate has been studied for two different gas injection pressures of 40 psig and 50 psig.The developed model shows that more than 50%of the liquid production is coming from after flow period.

Experimental study and field application of appropriate selective calculation methods in gas lift design

The most common way to achieve an enormous production rate of a reservoir is to increase drawdown pressure during the production procedure by decreasing the bottom-hole pressure.This process was done by artificial patterns like a gas lift.Nowadays,most of the wells worldwide due to years of production and reducing the amount of energy which was supplied by natural drive mechanisms are being placed on artificial lift methodologies.Hence,the number of wells that used this method will continue to increase.The primary purposes in the gas lift design of a wellbore are to determine the proper depths and the location of valve installation,select appropriate flow regime during the pipeline and calibrate the pressures of the operating and unloading valves.The purpose of this research is to design gas lift system in the oil wells of on the south fields of Iran by considering the maximum production connate water volume of 40 percent and average pressure drop(20-25 psia)throughout the year regarding production continuously or increasing the flow rate of the wells.Therefore,20 wells that their number starts A to T with this locations L280N,W115S and W002S are the candidates for gas lift procedures.Furthermore,the appropriate flow regimes through the well are being studied,and the most proper method for gas lifting and required surficial equipment will be designed for this field.Consequently,due to increasing the volume of gas and connate water among the production after gas lifting,fundamental changes on the equipment,flow regimes and gas lift system are being proposed that production will be done by proper engineering method.In the well gas lift design,Beggs&Brill Revised method is being selected for hydraulic calculation of pipeline flow due to low errors.

Application of machine learning algorithms to predict tubing pressure in intermittent gas lift wells

Tubing pressure at gas injection depth in intermittent wells is one of the most critical parameters for production engineers to evaluate the performance of the system.However,monitoring of the tubing pressure is not usually carried out in real time.It has been realized that the generally used correlations are not effective enough due to complexity of the intermittent process which involve many parameters and assumptions to develop such equations.The focus of this study is to utilize machine learning(ML)algorithms to develop a model that can accurately predict tubing pressure in artificial intermittent gas lift wells.intelligent algorithms built on the field data provide a solution that is easy to use and universally applicable to the complex problems.Various non-linear regression ML methods are employed in this study,namely,Decision Tree-regression(DT),Random Forest-regression(RF)and K Nearest Neighbors-regression(KNN).All the tubing pressures obtained from ML models were compared with the actual values to ensure the effectiveness of the work.The developed models show that it can predict the pressure with more than 99.9%accuracy.This is an interesting result,as such outcome accuracy has not been reported usually in the open literature.

Optimization of gas lift system for well performance improvement in Asmari formation:A techno-economic perspective

Well productivity in the Asmari carbonate formation of southwest Iran has decreased in recent years as a result of production issues.The production rate must be maintained below 1500 STB/day to prevent water coning.In this study,a gas lift well is modeled using data from one of the producing wells of this field.Nodal analysis is performed using lift-gas injection rates and wellhead pressures at different reservoir pressures and water cut conditions to optimize production.Economic aspects are considered to optimize the artificial gas injection rates at different tubing head pressures and water cut conditions.Increasing the lift-gas injection rate from 0.4 MMscf/day to 1 MMscf/day enhances the oil production rate by 37.71%and 43.89%for 10%and 30%water cut conditions,respectively.Gas injection rates of 5.2 MMscf/day and 5.4 MMscf/day are determined to be economically optimal for 30%water cut with tubing head pressures of 260 psig and 270 psig,respectively.

Improving Existing Drainage and Gas Recovery Technologies: An Experimental Study on the Wellbore Flow in a Horizontal Well

With the increasing number of horizontal wells with low pressure,low yield,and water production,the phenomenon of water and liquid accumulation in gas wells is becoming progressively more serious.In order to fix these issues,it is necessary to improve existing drainage and gas recovery technologies,increase the fluid carrying capacity of these wells,and ensure that the bottom-hole airflow has enough energy to transport the liquid to the wellhead.Among the many techniques of drainage and gas recovery,the gas lift has recently become a popular method.In the present study,through the simulation of the entire horizontal well,the flow regularity of the whole wellbore during the lift of low-pressure gas has been analyzed.The pressure distribution,liquid holdup rate,flow pattern,and energy loss(including gravity loss and friction loss)have been determined using the Beggs-brill approach.It has been found that the total pressure drop of the wellbore decreases first and increases gradually after reaching a minimum value when gas extraction is carried out via gas lift.Based on the analysis of the influence of the injection volume on wellbore pressure drop and the influence of flow pattern on the lifting efficiency,the optimal gas-lift injection parameters have been determined by taking the minimum pressure loss of wellbore as the judgment criterion.

Integrated asset management:a case study of technical and economic optimization of surface and well facilities

Oil production could be increased by using optimization techniques in each stage of oil production system from field to production unit.However,the maximum profit will be obtained once integrated optimization of surface and subsurface components of the oil production system is implemented.In addition,when using high-tech equipment and facilities,an integrated study of well and surface facilities affects the economic benefits significantly.In this work,one of the Iranian brown fields(mature or declining production fields)was studied to find the best renovation plan with maximum profits.The base scenario was designed with four stages of separation,and the high-pressure gases from the first and the second separator were planned to be sold,while the low-pressure gases from subsequent stages were supposed to be flared.In this paper,two additional scenarios,namely separator optimization and full optimization,were proposed and 12 cases were defined.In the full optimization scenario,low-pressure gases were prevented from being flared.It was observed that by stopping the flaring systems,gas production rate increases as high as 20%and 150 to 200 MW power will be generated in all cases during the next 20 years.Finally,economic evaluation for all of the cases was done and different cases were compared in terms of incremental annual worth and payback period.