Research on Optimization of Intermittent Production Process System
Abstract
:1. Introduction
2. Mathematical Model
2.1. Model Establishment
- The gas–liquid flow velocity and pressure distribution in the wellbore are solved using a transient model;
- The steady-state two-phase flow friction and holdup calculation are also applicable to transient conditions.
2.1.1. Initial Condition
2.1.2. Formation Inflow
2.1.3. Liquid Plug Formation Stage
2.1.4. Liquid Plug Outflow Stage
2.1.5. Liquid–Gas Eruption Stage
2.1.6. Liquid Reflux Stage
2.2. Model Solution
2.2.1. Grid Division Method
2.2.2. Boundary Conditions
2.2.3. Solution Steps
3. Optimization of Intermittent Production System
3.1. Overview of Intermittent Gas Well Production
3.2. Intermittent Production History Fitting
3.3. Dynamic Analysis of Intermittent Production Process
3.4. Optimization Simulation of Intermittent Production System
3.5. Integration of Intelligent Control System for Intermittent Production System
4. Conclusions
- The intermittent production process of gas wells is divided into four stages, and a transient mathematical model for intermittent production is established in stages, considering the variation laws of slip gas holding rate, pressure, and gas–liquid inflow and outflow of tubing and casing;
- The use of dynamic tracking technology for the movement of liquid plugs in the wellbore results in fine mesh division of the plug interface position. The mesh boundary is re finely divided to ensure that the liquid plug interface falls exactly at the mesh boundary, greatly reducing computational complexity and improving computational accuracy;
- The transient mathematical model developed for intermittent gas well production achieved a high historical fit accuracy of over 90%. This indicates that the simulation results are in line with the real situation of gas well intermittent production and can effectively guide intermittent production;
- Based on the transient mathematical model of intermittent production, the boundary point between opening and closing the well is determined, and the variation laws of pressure, liquid level rise velocity, liquid level height, etc. during the closing process are obtained. The optimal closing time for intermittent production in Menxi 005-H3 well is determined to be 11 h;
- The cumulative gas production of Well Menxi 005-H3 within one month under the original intermittent production system was 3.65 × 105 m3. After optimizing the intermittent production system, the cumulative gas production within one month was 3.91 × 105 m3, indicating a higher cumulative gas production. This demonstrates the effectiveness of the intermittent production system optimization model and method established in this paper, achieving the optimization of the intermittent production system and guiding efficient production of gas wells in low-pressure formations.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
Nomenclature
Symbol | Explanatory Note |
pwf | The pressure at the connection point between the tubing and the casing, MPa |
pr | Formation pressure, MPa |
pi | Raw formation pressure, MPa |
pt | Tubing pressure, MPa |
pc | Casing pressure, MPa |
ptg | Gas–liquid interface pressure in tubing, MPa |
pcg | Gas–liquid interface pressure in casing, MPa |
pcavg | Average gas pressure in the casing, MPa |
ptavg | Average gas pressure in the tubing, MPa |
∆pu1 | The difference-pressure of the flowing gas column above the tubing liquid level, MPa |
∆pb1 | The difference-pressure of two-phase flow below the tubing liquid level, MPa |
∆pu2 | The static gas column difference-pressure above the casing liquid level, MPa |
∆pb2 | The static liquid column difference-pressure below the casing liquid level, MPa |
p2 | Pressure behind the throttle valve, MPa |
pf | The pressure caused by the liquid falling back from the bottom of the tubing, MPa |
pt(0,t) | The pressure at the outlet of the tubing, MPa |
Krg | Relative permeability of the gas phase |
Krw | Relative permeability of the water phase |
μg | Gas viscosity, mPa·s |
μl | Water viscosity, mPa·s |
Rsgw | Dissolved air-to-water ratio |
Rpgw | Produce gas-to-water ratio |
Rswg | Dissolved water-to-air ratio |
Sg | Gas saturation |
Sw | Water saturation |
gg | The shape factor of the relative permeability curve of the gas |
ww | The shape factor of the relative permeability curve of the water |
G | Single-well dynamic reserves, 108 m3 |
Gp | Cumulative gas production, 108 m3 |
We | Cumulative water intrusion, 104 m3 |
Wp | Water production, 104 m3 |
Cw | Compressibility coefficient of water, MPa−1 |
Cf | Compressibility coefficient of rock, MPa−1 |
Swi | Bound water saturation |
γg | Relative density, kg/m3 |
ρl | Liquid density, kg/m3 |
ρg | Gas density, kg/m3 |
ρm | Mixed density, kg/m3 |
qsc | Formation gas production, 104 m3/d |
qw | Formation water production, m3/d |
qtg | The gas flow rate flowing into the tubing,104 m3/d |
qcg | The gas flow rate flowing into the casinging,104 m3/d |
qtsc | Wellhead gas production, 104 m3/d |
qlo | The water production rate at the wellhead, m3/d |
d | Tubing diameter, m |
D | Casing diameter, m |
dl | Maximum droplet diameter, m |
At | The annular area of the casing, m2 |
Ac | Casing area, m2 |
H | Well depth, m |
Tc | Casing temperature, K |
Tt | Tubing temperature, K |
ht | The height of fluid accumulation in the tubing, m |
hc | The height of fluid accumulation in the casinging, m |
Zc | Compression factor of casing |
Zt | Compression factor of tubing |
Zi | Gas deviation factor under raw conditions |
M | Molar mass of gas, kg/mol |
mg | Gas mass, kg |
ml | Droplet mass, kg |
vcg | The gas flow rate of the casing, m/s |
vtg | The gas flow rate of the tubing, m/s |
vtgout | Gas outflow velocity, m/s |
v0 | Gas drift velocity, m/s |
vtbg | The rising speed of the first gas bomb inside the tubing, m/s |
vcr | The critical liquid carrying velocity of gas, m/s |
vfd | Liquid falling speed, m/s |
vdown | The speed at which the down of the plug moves, m/s |
vup | The speed at which the up of the plug moves, m/s |
vl(0,t) | The velocity of the liquid at the tubing inflow, m/s |
vg(0,t) | The velocity of the gas at the inflow of the tubing, m/s |
vl(nt,t) | The velocity of the liquid at the outlet of the tubing, m/s |
vg(nt,t) | The velocity of the gas at the outlet of the tubing, m/s |
vl(nc,t) | The velocity of the liquid at the outflow of the casing, m/s |
vg(nc,t) | The velocity of the gas at the outflow of the casing, m/s |
Vcg | The volume of compressed gas space in the casing, m3 |
Vtg | The volume of compressed gas space in the tubing, m3 |
Vf | The volume of liquid falling back, m3 |
σ | surface tension, N/m |
nc | The ratio of the mass of casing gas to the molar mass of gas |
nt | The ratio of the mass of tubing gas to the molar mass of gas |
n | Index |
R | Gas constant |
Bg | Gas volume coefficient |
Bw | Water volume coefficient |
Bgi | The volume coefficient of the gas under the original conditions |
f | Friction coefficient |
a | Laminar flow coefficient |
b | Turbulence coefficient |
J | Water production coefficient |
k | coefficient |
Cd | coefficient |
β | Ratio of tubing area to flow area of membrane valve |
Hl | Slip liquid holdup |
C0 | Flow coefficient |
Cl | Drag coefficient |
Xdonwnew | Update the down position of the plug |
Xdonwold | The down position of the plug in the previous time step |
Xupnew | Update the up position of the plug |
Xupold | The up position of the plug in the previous time step |
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Xiong, J.; Zhang, T.; Yang, J.; Sun, F.; Liu, J.; Wen, Y.; Pan, G. Research on Optimization of Intermittent Production Process System. Processes 2024, 12, 1877. https://doi.org/10.3390/pr12091877
Xiong J, Zhang T, Yang J, Sun F, Liu J, Wen Y, Pan G. Research on Optimization of Intermittent Production Process System. Processes. 2024; 12(9):1877. https://doi.org/10.3390/pr12091877
Chicago/Turabian StyleXiong, Jie, Ting Zhang, Jian Yang, Fengjing Sun, Jianyi Liu, Yimin Wen, and Gongheng Pan. 2024. "Research on Optimization of Intermittent Production Process System" Processes 12, no. 9: 1877. https://doi.org/10.3390/pr12091877