Gas Lift Design with Self-Well Gas for AZN-02

R&D Center, Tuha Oilfield Company

January 15, 2014

1. Technical principle

1.1 Technical principle

Gas lift with gas from self-well is a development method used for a well with independent 2 sets of oil and gas zones. As to this technology, the external high pressure gas source is not needed. The high pressure gas zone is used for the production of other oil zones. The high pressure gas from gas zone is continuously injected into tubing with regulated volume via gas lift valves, where the gas well mixes with the well fluids to form mixed fluids. By doing so, the well fluid density is decreased and the purpose of gas lift oil production is realized. This method can not only rationally control the production of high pressure gas zone, but also the purpose of producing from the oil zones can be realized.

1.2 Techncial features

①The oil production cost is lowered by using the produced gas from self-well gas zone;

②The injection volume of the gas zone produced gas is controlled by gas lift valves and the inter-layer interference of gas and oil zones is avoided, therefore, the commingled production of oil and gas is realized;

③The independent oil production requirements is satisfied by forming the single well production system.

1.3 Scope of applicaiton

①The oil and gas are in different zones with stable barriers in between;

②The gas zone pressure coefficient is larger than 0.9MPa/100m;

③The gas zone gas production must satisfy the gas demand of oil well production, i.e.≥5000m3/d;

④ The barrier thickness of oil and gas zones shall be larger than 5m.

2. Purpose and requirement of construction

The high pressure gas source from AG 2D-1 zone of Well AZN-02 is used for the pilot test of gas lift with self-well gas and the crude oil in the three zones of AG-2D-3, AG-2D-5, and AG-2F-1 will be lifted.

3. Basic data

3.1 Basic data

Tubulars Size Weight Grade Set atConductor N/A N/A N/A N/A

Surface Casing 244.5mm 59.5kg/m K-55 1123Intermediate Casing N/A N/A N/A N/AProduction Casing 177.8mm 43.0kg/m K-55 1700Production Tubing 88.9mm 13.84kg/m J-55

3.2 Wellhead data

Wellhead: Make Size WP Serial NumberCasing Vent: Stream Flo 52.38 mm 14 Mpa N/A

Casing Bowl: Stream Flo 279.4 mm 21 Mpa 134628-15

Tubing Head: Stream Flo 279X179 mm 21 Mpa 136991-07

Master Valve: Stream Flo 79.37 mm 21 Mpa

Wing Valve: JMP 79.37 mm 21 Mpa N/A

Casing Valve: Stream Flo 52.38 21 Mpa N/A

Casing Valve: Stream Flo 52.38 21 Mpa N/A

3.3 Existing string configuration

Fig. 2 String configuration of AZN-02

4. Optimization design

4.1 Basic data of gas lift well with gas from self-well

Table 4-1 Basic data of gas lift well AZN-02 with gas from self-well

Gas zone AG-2D-1 Pay zone AG-2D-3, AG-2D-5,

AG-2F-1

Perforation interval of gas zone

(m)1672~1675 Mid-depth of oil zone(m) 1864

Mid-depth of gas zone (m) 1673.5 Temperature of oil zone(℃) 83

Temperature of gas zone (℃) 73 Formation pressure (psi) 2000

Gas zone pressure (psi) 2183 Water cut (%) 40

Gas rate（MMscf/d） 8 Liquid production index (STB/d/psi) 1

Oil rate（blpd） 300~400 Saturation pressure (MPa) ——

Specific gravity of produced gas 0.734 Specific gravity of produced water ——

Casing size (mm) 177.8 Specific gravity of crude (g/cm3) 0.822

Tubing size (mm) 89 Production GOR (m3/m3) ——

Wellhead tubing pressure (MPa) 1.5

4.2 Process design for gas lift production with gas from self-well

（1）Calculation of gas injection pressure and volume

Fig. 3 Gas injection volume and depth of gas lift production with gas from self-well

It is calculated that when gas injection pressure is 7MPa and gas injection rate is

28317m3/d（1mmscf/d）, the lift depth can be 1620m and the production capacity of

the well can be well performed. The pressure of gas source zone of AG-2D-1 is high

as 15.05 MPa (2183psi), which can fully satisfy the requirement of gas lift.

（2）Gas lift design

Lift gas flowrate

Gas lift depth

Stoc

k-ta

nk li

quid

flow

rate

at o

utle

t

Fig. 4 Gas lift design It is calculated that the liquid production rate of three horizons of AG-2D-3, AG-2D-

5, and AG-2F-1 is 850STB/d.

Table 4-2 Design production parameters

Projected oil rate（STB/d） 510 Gas injection volume (mmscf/d） 1

Projected liquid rate（STB/d） 850 Gas injection depth（m） 1620

Water cut（%） 40 FBHP（psi） 1105

Table 4-3 Design gas lift valve parameters

Stages Model Measured depth（m）

Valve port size（mm）

Opening pressure for adjustment（psi/MPa）

1 KFT-B-25.4 1620 4.8 870/6.05Table 4-4 Technical parameters of matching tools

Description

Total

length（mm

）Max. OD（mm） Min. ID（mm） Connectio

n thread

Tools

quantity（set）KPX-127 gas lift mandrel 2000 127 60 27/8″EUE 1

KFT-B-25.4 gas lift valve 260 25.4 —— —— 1

Y211-148 packer 1670 148 62 27/8″EUE 1

Bell mouth 165 78 50.6 27/8″EUE 1

KZF-94 landing nipple 327 94 56 27/8″EUE 1

KHT-105 slickline sliding

sleeve1021 105 57 27/8″EUE 1

Cross over 27/8″EUE conversion to 31/2″EUE 5

5. Procedure of construction5.1 Wellbore prepoaration Gas injection depth

5.1.1 Release bridge plug, kill and flush well

5.1.4 Run drift gauge

Run 1501.8～2.0m drift size gauge tool to artificial well bottom or current plug surface. Flush well reversely until the inlet and outlet liquids are identical. Pull up the drifting string. During drifting, no exerting pressure abruptly. When obstruction is encountered or the hanging weight changes, advise relevant parties timely. (Before running drifting gauge, check its integrity and the velocity of running in string shall be less than缺具体数字 ). (While pulling up, infill liquid to maintain the liquid level at wellhead)

5.1.5 Scraping and pressure test for tubing

Run in 7" casing scraper below the perforation interval and repeat scraping at least 3 times in the Y211-148 packer location to guarantee the inner wall of casing clean, burr-free and then pull up the scraping string.

5.2 Run in the gas lift completion string

Configure and run in string: run the gas lift string with gas from self-welll to the design location as shown in Fig. 5. The string is composed of packer and gas lift mandrels etc. From bottom to top are bell mouth+KZF landing nipple+Y211 pakcer+ KHT slickline operation sleeve+KPX gas lift mandrel.

(2) Measure the length of each tubing and completion tool to be run in hole (the error shall be less than 1/1000) and record the data;

(3)Clean the dirt in tubing. When tubing is run, the 31/2″heavy weight tubing shall be drifted with 73mm×0.5m gauge. When unqualified ones are found, replace in time;

(4) When string is connected, the arrow direction of side pocket mandrel (i.e. box side) must be upward. The protection tape shall be taken off and gas lift valves shall be installed in mandrels.

(5) When string is run, strictly prevent the adherence of foul or clay to avoid the plugging of valve ports.

(6) When running in gas lift completion string as per the gas lift completion string schematic (when tubing and tubing, tubing and completion tool are connected), PTFE tape coated with sealing grease must be applied to the tubing threads and completion tools. The threads shall be tightened to guarantee no leakage under the pressure of 35MPa; when string is run, the operation shall be stable, and no running and puling violently. The net running time for joint shall be no less than 20s and the drillpipe net running time shall be no less than 45s.

(7) Depth calibration and string adjustment: magnetic depth calibration shall be conducted. The strings shall be adjusted as per the result of depth calibration to match the design location. Ensure the accuracy of packer setting location.

(8) Set Y211: when the casing is fully filled, set Y211-148 packer. Pull up string by

1.0～1.2m, and record the maximum load. Slowly lower the string and the hanging

weight decreases 8～10 tons to set Y211-148 packer.

(9) Install wellhead according to the requirements. Well connect gas injection pipelines, oil outlet pipeline and casing & tubing pressure gauges. Guarantee no leakage and the integrity of gauges.

5.3 Induced flow commissioning

(1) Install the flowline and carry out commissioning with the format of open flow;

(2) If production cannot be achieved, commissioning shall be made by injecting N2

produced from Nitrogen trailer into annulus and deliquification shall be conducted from tubing;

6. Requirements of constructionKilling fluids shall be filled from casing in time during tripping and the liquid

level shall be maintained at wellhead.

All the tools to be run in hole shall be checked and made sure qualified by the operation supervisor before their RIH.

6.1 Requirements of open flow commissioning

Before open flow, the tubing and casing flowline, wellhead separator, and wellhead ignition system shall be installed. Based on the season wind direction of local area, the open flow system shall be installed in the downwind side. The outlet shall be more than 30m from wellhead. The surface flowline must be metal and straight. The included angle must be larger than 120° and flowline shall be fastened with ground anchor each 10-15m. No significant throttle shall occur to the flowline and the flowline must be securely fastened.

6.2 Requirements to commissioning with N2 trailer

6.2.1 Before gas lift commissioning, the whole gas injection process shall be purged with N2 to guarantee the gas injection pipeline clean and free from foreign matters; the surface gas injection pipeline shall be tested with 25MPa pressure N2 and no leakage shall occur. When qualified, open the casing control valve to inject gas into the casing and tubing annulus;

6.2.2 Control the flow rate of N2 trailer and slowly control the gas lift gas into the oil well. Initially, the gas injection rate shall be controlled so that the casing pressure increases 2MPa each hour until the wellhead casing pressure increases to 3MPa;

6.2.3 Increase gas injection rate so that the casing pressure increases 4MPa per hour till the gas lift valves start to injection gas;

6.2.4 After 12 hours of continuous deliquification, when the deliquification stabilizes

or the production is in stable condition, the N2 trailer can stop and the production will convert to gas lift with gas from self-well. If the oil well cannot produce normally, then follow 6.2.5;

6.2.5 Vent the casing and tubing annulus till ignition can be made at the end of flowline;

6.2.6 Close casing valve, stop open flow and convert to production with gas from self-well;

Note:

（1）If the gas injection is too intense, the valves ports may be damaged.

（2）During unloading, wellhead back pressure shall be lowered as much as possible

to guarantee the smooth commissioning of gas lift well.

7. Requirements to well control7.1 Determination of killing fluid density

The relevant downhole operation well control regulations of GREATER NILE PETROLEUM OPERATING COMPANY shall be strictly followed.

7.2 Notice to risk of string tripping in and out

7.2.1 Before running in string, the wellbore preparation procedure including drifting, scraping and flushing shall be well followed. The string with packer shall avoid sticking and the damage to the rubber sleeve shall also be prevented;

7.2.2 Before running in hole, the respective tools and tubing shall be accurately measured. The threads shall be cleaned with diesel and steel brush. The unqualified tubing shall be picked out. The threads of tubing to be run in hole shall be applied with sealing grease. The specified torque for tubing threads shall be applied with hydraulic tongs to avoid bad sealing performance;

7.2.3 Connect the downhole tools such as packer. Back-up wrench shall be applied during tightening to avoid the turning of string, which may lead to the setting of packer mid-way. Lower the string at even speed. No running and puling violently. The net running time for joint shall be no less than 20s and the drillpipe net running time shall be no less than 45s. If obstruction is encountered, the pressure exerted shall not exceed 30kN;

7.2.4 In order to guarantee the performance of tools to be run in hole, all the threads of tools shall be applied with sealing tape and sealing grease.

7.3 Notice to commissioning risk

7.3.1 The gas injection rate shall be strictly controlled in accordance with the process

design. If the gas injection rate is too high, the valve ports will be damaged.

7.3.2 If the start pressure cannot satisfy the requirement of gas lift design, normal unloading will not occur to the oil well. In such case, the wellhead back pressure shall be lowered as much as possible to realize the smooth unloading and normal production of gas lift wells.

7.3.3 During gas lift production, the wellhead casing pressure is about 1911psi. In order to guarantee long-term safety production, pressure test shall be conducted for the wellhead. The relevant standards for pressure testing of GREATER NILE PETROLEUM OPERATING COMPANY shall be referred to. When result of pressure test is qualified, the gas lift production with gas from self-well can be conducted.

7.3.4 During gas lift production, the monitoring to the pressure of surface casing and intermediate casing shall be well performed. If there is anomaly with the pressure, report to the Operation Department shall be made immediately and relevant operation shall be carried out by following the instruction from the Operation Department.

7.4 Requirements to blow out prevention

7.4.1 Careful check shall be made to the wellhead blowout prevention facility to guarantee they are in full function. The well site shall be furnished with high quality killing fluids and equipments. The preparation for the installation of wellhead during emergency shall be made. The wellhead shall be installed immediately once well kick is discovered to carry out well killing operation. The well control measures shall be strictly executed to strictly avoid environmental pollution.

7.4.2 The blowout prevention shall be able to seal the operation string of all sizes.

7.4.3 When continuous operation cannot be made to the well with natural flow capacity, the wellhead facility shall be well installed to avoid blowout.

7.4.4 During tripping, the blowout prevention facility (such as tubing control valve and tubing cocks etc.) capable of plugging tubing shall be prepared.

7.4.5 During tripping operation, if the wellbore fluids touch the string, the wellhead blowout prevention facility shall be shut off under the premise of guaranteeing the smooth operation of string and then the following step shall be adopted.

7.4.6 During tripping operation, the killing fluids in wellbore shall be maintained permanently fully filled. Killing fluids shall be supplemented once for each tripping

of 10～ 20 pieces of tubing. Opening while blowout occurs is not allowed. The

blowout prevention facility shall be immediately shut off once the string is tripped out.

7.5 Precautionary measures

7.5.1 The relevant norms and standards in terms of blowout prevention and pollution prevention for oil well operation shall be strictly executed.

7.5.2 No smoking in the operation job site.

7.5.4 The pressure test of the pipeline must conform to the requirement of design.

7.5.5 Nitrogen purging must be carried out to the high pressure gas pipeline during welding to guarantee the safety of welding operation.

7.5.6 After the high pressure pipeline is installed, air tightness test shall be made to verify the leak points. Open the surface gas supply valves and slowly control the pressure to 20MPa to check if there are leak points. If there are such points, vent the pipeline, fasten connections and reliably seal; dedicated personnel shall be designated to check the leak points. The irrelevant personnel shall stay 30m from the operation site and no fire source shall be taken into the operation area.

7.5.7 The speed of tripping operation shall be controlled within 30 pieces per hour. The blowout preventer shall be well installed. Once well kick or blowout occurs, swift handling shall be made in accordance with the well control emergency procedure.

7.5.8 Before construction, the pressure test shall conform to the design requirement. The overpressure operation shall be prohibited; during construction, the field operators shall wear the personal protection equipment and shall stay out of the safety distance from the high pressure zone.

7.5.9 The field operators shall pay high attention to safety and be aware of the escape route.

Fig.5 Completion string for gas lift well AZN-02 with gas from self-well

1672m

1675m

Gas zone

1717m

2012mOil zone

Bell mouth 1720m

KZF-94 landing nipple 1710m

Y211-148 packer 1700mDepth adjustable to casing collar size调整深度

KHT-105 slickline operation sleeve 1680m

KPX-127 gas lift mandrel 1620m

31/2″ tubing