Artificial Lift Design of Mishrif Formation in Nasiriyah Oil Field

E1 Artificial Lift Design of Mishrif Formation in Nasiriyah Oil Field Mohammed Saeed Mohammed, Dr. Abdul Aali Al Dabaj, Dr. Samaher AbdilRassol Lazim Petroleum Technology Department, UOT, Iraq Corresponding Author E-mail: msm_8310@yahoo.com Abstract: The possibility of improving the oil production rate for Mishrif formation in Nasiriyah oil field, located in Thi-Qar Governorate – southern province of Iraq, proposed in this paper. Electrical submersible pump (ESP) and gas lift techniques were applied to one well (NS-Y) in the studied reservoir. Firstly, the mathematical model has been built and validation has been done using PIPESIM software in order to select the best correlation (Duns & Ros correlation) for the pressure gradient calculation in the wellbore. The effect of decreasing reservoir pressure and increasing water cut on production rate has been studied through the evaluation of the well performance. The production rate was decreased to 1917 STB/D when reservoir pressure reached to 2750 psi, and flow rate decreased to 1210 at water cut 60%. Therefore, the artificial lift techniques were applied to increase the oil production rate. The result showed that Gas lift system contributed to increase production rate to (3198) STB/D at reservoir pressure equal to 2750 psi, while using the ESP system improved oil production rate to (2800) STB/D at reservoir pressure 2750 psi. The results also showed that gas lift system contributed to increase production rate to (3805) STB/D at water cut 60% and ESP raised the production rate to 3087 STB/D at water cut 60%. The comparison between them showed that the gas lift technique gave the highest production rate at different reservoir pressure and water cut. يطفنلا ةيرصانلا لقح يف فرشملا ةقبطل يعانصلا عفرلا ةموظنم ميمصت ةصلاخلا :


Introduction:
There are a number of oil wells, can flow naturally depending on the reservoir energy in the first life of production. After a period of production, the flow rate decreases until it is not possible for natural flow to continue. In order to maintain production for as long as possible, new methods were developed to resume or increase production. Artificial lift represents the one of these methods, which used when decreasing reservoir pressure and the well wouldn´t is able to lift fluid up to the surface [1]. Approximately 50% of wells need artificial lift systems. The commonly used method is artificial lift [2]. The most used methods in Iraqi oil fields are Gas lift and Electrical Submersible Pump, where the Gas lift method takes place through injection of a specific amount of compressed gas in the annular between casing and production tubing, which works by reducing the density of liquid in wellbore and lightening the hydrostatic column. This helps to raise the fluid E3 to the surface, Gas lift is utilized in one of the two ways: (1) continuous gas lift by continuous gas injection into annular between the production tubing and casing (2) intermittent lifting by rapid injection of very large quantities of gas into the tubing,

Mathematical models:
A Mathematical model used to simulate fluid flow for the system. It contains complete information on the well, including wellbore construction, downhole equipment and artificial lift equipment. This model has been developed based on the available data from well completion reports as shown in Table (1).

Pressure gradient matching:
The data matching task has been used to select the suitable flow correlations for the pressure drop and heat transfer calculations in the wellbore. Measured flow data available in (Production Log Interpretation Report) has been used Table (2). This data has been inserted in Survey data catalog of PIPESIM. The next step is to run data

No.23-(6) 2019 Journal of Petroleum Research & Studies (JPR&S)
E4 matching and choose the appropriate correlation among the correlations available in PIPESIM. The selection of the correlation is based on the optimal flow rate should give the lowest error ratio for the measured flow rate. The best flow rate gives the lowest value of (RMS).

Nodal analysis and bottom hole pressure (P wf ) match:
After selecting the appropriate correlation for the well, a nodal analysis has been built which represent the relationship between vertical lift performance curve (VLP) and  Well performance with the reduction of reservoir pressure: Evaluation of well performance was considered using Nodal analysis (inflow sensitivity) by evaluating the effect of reduction of reservoir pressure on production flow rate for the well. The result showed that the production rate of well (NS-Y) reached 1917 STB/D when reservoir pressure decreased to 2750 psi, as shown in Table ( Well performance with the increase in water cut: As the water cut increases to 60%, the production rate reaches to 1210 STB/D. Table

Gas lift design:
The objective of this work is to find the best location for unloading valves and operating valves for the gas lift plant.

Determine optimum surface injection pressure and Optimum gas injection rate:
From a gas lift response simulation in PIPESIM, the well performance under gas lift with the surface injection pressure (casing head pressure, CHP) and target injection gas rate (Qgi) have been determined. The ranges of sensitivity data for gas lift response contain ten values for target injection gas rate and three values for surface injection pressure; therefore, the sensitivity was repeated twice for each well in order to take more values of (CHP). The results of gas lift response in PIPESIM for well (NS-Y) can be seen in Table   (7) and Figures (5 and 6), which explained the optimum gas injection rate of 3MMSCF and optimum surface injection pressure of 1800psi.

Gas Lift valves Installation design
The objective of the valve design is to determined position of the process and Unloading Valves, which depends on the gas injection pressure to calculate the Opening and closing pressures for gas lift valves. Figure (7) showed the results of well (NS-Y) as listed in

Fig. (9) The performance curve of pump for well (NS-Y)
Results:

1-
The results of reservoir pressure decreasing showed that production rate after installation of the  Tables (10 and   11), and showed in Figures (10 and 11). All values of flow rate and P wf have been calculated by PIPESIM software based on the principle of nodal analysis. The P wf in ESP case was higher than the Gas lift case because the design flow rate has been selected at P wf above Bubble point pressure (2105 psi). Finally, the Gas lift system has achieved quantities of production rate was more than ESP at different reservoir pressure as shown in Figure (

2-
The impact of water cut demonstrates that ESP system achieved higher production rates than Gas lift system at water cut 0 and 10%, while the gas lift system achieved higher production rates than ESP system at water cut 20%, 30%, 40% ,50% and 60% as given in Tables (12, 13) and Figures (13, 14 and 15).