De-Liquification and Revival of Oil & Gas Wells using Surface Jet Pump (SJP) Technology

Transcription

1 Gas Well Deliquification Workshop Sheraton Hotel, February 19 22, 2012 De-Liquification and Revival of Oil & Gas Wells using Surface Jet Pump (SJP) Technology Colin Morrison & Sacha Sarshar, Caltec, UK

2 Main causes of Liquid Build-up in Oil & Gas Wells Low velocity of gas to carry the liquids through the well bore is caused by a variety of factors Multiphase flow through the well bore could lead to flow regimes such as annular mist, churn flow, slugging, etc., which affect both the hydrostatic head and frictional losses through the well bore The rise in flowing bottom hole pressure (FBHP) is the main factor affecting production. FBHP is a guide but could be misleading Inclined & horizontal profile of wells contribute to gas-liquid separation within the well bore and generation of slugs 2

3 FWHP Effect of Field Depletion on Well Bore Pressure & Production Potential increase of Non Darcy effect due to added turbulence Increase of effective stress (difference between the overburden and fluid pressures) Closure of near well bore natural / micro fractures Closure of induced fractures (fracture conductivity reduction) Near wellbore damage P1 P2 Wells characteristics Q2a Q2b Q1a Q1b Fines migration build-up Flow rate Screen plugging Sand production and build-up in well sump Hole collapse Scale build-up These result in; poorer drawdown and PI Q2 W2 W1 Q1 3

4 Superficial Liquid Velocity (m/s) Superficial Liquid Velocity (m/s) Comparison of Flow Regimes in Horizontal and Vertical Pipes Dispersed Bubble Intermittent Horizontal Pipes Stratified Wavy Annular Mist Correct prediction of flow regime is important in correct prediction of FWHP Slug Bubble Annular Mist Vertical Pipes Froth Source: 8 th International Conference on Multiphase 97 Superficial Gas Velocity (m/s) V 5 m/s 4

5 Challenges of Predicting the FBHP/FWHP using Commercial Software FWHP is provided and software calculates the FBHP FBHP is provided and software calculates the FWHP Measured value 5

6 Remedial Solutions to Well De-Liquification Regular gas blow down to atmosphere Well shut in intermittently not always successful Lower Flowing Well Head Pressure (use of surface jet pump, continuous operation) Use of foaming agents Tubing size modification/velocity string Artificial lift systems including ESP s, plungers, foam injection, jet pumps Best solution in each case is dictated by well status, inflow characteristics, reservoir characteristics, available source of energy, platform constraints and economic considerations. This means a fully integrated analysis. 6

7 Severity and Extent of Liquid Build-up Influences the Solution Selection One-step solution Cases when lowering the FWHP is sufficient to revive the well, the question is effectiveness at what FWHP or FBHP? Cases when a bottomhole boosting system or gas lift is essential for revival and maintaining production Two-step solution Cases when an initial de-liquification is needed, followed by operation under a lower FWHP Two-stage solution, combination of two methods such as use of soap sticks + lower FWHP could be an optimum solution 7

8 Surface Jet Pump (SJP) Technology HP Wells Manifold SJP Commingled Product Patented Universal Design SJP LP Wells Manifold Wellcom TM Gas Some Possible HP Sources:- Removable Nozzle Removable Mixing tube /Diffuser Hp wells (Oil or Gas wells) Compressor Gas/Recycle gas Hp Gas From Process System A Single Phase (Liquid) Pump Hp Liquid (Oil, Water) 8

9 Main Factors Affecting the Performance of SJP Surface Jet Pump Performance Key Factor for Jet Pump Performance: HP/LP pressure ratio LP/HP flow ratio Discharge/LP pressure ratio Other Factors not included in these curves: Temperature, Z factor, Molecular weight, Cp/Cv ratio etc. 9

10 Types and Ranges of SJP Applications Revival of dead Oil & Gas wells/well de-liquification Boost production from Oil or Gas wells Boost pressure of LP gas in a process system De-bottleneck compressors Eliminate intermediate compressors Prevent HP wells to impose excess back pressure on LP wells Prevent flaring of LP gas Achieve de-liquification of pipelines 10

11 Well Revival Spilamberto Field, Italy Daily Production Solution Near-by HP gas well used as the HP source. Benefits: Revived liquid loaded dead well Sustained gas production at 23,000 sm3/d (0.812MMscfd) for almost two years 11

12 BP Inde, UKCS Solution: Used HP recycled gas to power SJP, to draw-in low pressure satellite shell wells. Benefits: Recovered extra 68 MMscfd of gas from LP Shell wells. Stabilised/de-liquified LP wells Production increased by 25% Davy Line Bessemer Line Increased intake capacity of compressor De-bottlenecked existing compressor Low Pressure Gas Wells Juliet Kilo Separator Compressor Silencer Subsea Line Multi International Awards winning solution Surface Jet Pump Dp Recycle-line Silencer Export 12

13 Chevron, USA (GOM) Solution: HP gas from the existing compressor on recycle used to power the SJP to revive wells. Benefits: Lowered arrival pressure at the platform by 200 psi Higher gas velocities, removed bulk of liquids accumulated in the pipeline, causing a further 140 psi pressure drop at the wellhead Production increased by 24% due to FWHP reduction and lower pipeline pressure loss 2.5 Bscf of otherwise lost reserves recovered Separator Liquid 200 psig 40MMSCFD 400 psig Export Sales 7.4 MMSCFD 850 psig SJP Compressor Recycle gas GEMINI Sub sea manifold 1250 psig 13

14 Alaska, USA Solution: Used HP gas from long-string to off-load the well via SJP. Benefits: Used available wasted energy to offload the LP string Total production from well increased from 2.5 MMscfd to 7 MMscfd. Production increased by 180% Liquid loading cycle was reduced, hence more sustained production gain Gas Surface Jet Pump LP Wet gas Dual Completion Wellhead 14

15 Oil Production - Wellcom TM Boost System This is a Wellcom TM Boost system in which the separated gas is boosted with HP gas phase and the separated LP liquid is boosted with a HP liquid source. HP Gas Surface Jet Pump LP Separation System HI-SEP LP Gas Commingler Gas To export Pipelines I-SEP Liquid Liquid Liquid LP Oil Wells Commingler Booster Pump 15

16 Offshore Malaysia: Prevent New HP Well Restricting Production from LP Wells + Well Revival TT PT TT PT Gas SJP 14 Sub Sea Line to CPP HP Well PT TT PT Well Revival SJP PT PT Liquid booster pump TT LP Wells Production Header Test Header Test Separator M M 16

17 Wellcom System: Offshore Malaysia Lift gas as the motive flow + a booster pump to boost the liquid phase. HI-SEP Surface Jet pump (SJP) I-SEP Booster Pump 17

18 Wellcom Application: Cendor, Malaysia Solution: Wellcom oil system; multiphase HP wells were used to bring in closed low pressure (LP) oil wells. I-SEP Benefits: 20% pressure boost for LP wells Increased production by 35% (150 bbl/d) Gas From HP Well I-SEP Liquid SJP To Process System Improved flow regime in the well bore and stabilised production From LP Well Commingler 18

19 06:00:00 06:57:00 07:54:00 08:51:00 09:48:00 10:45:00 11:42:00 12:39:00 13:36:00 14:33:00 15:30:00 16:27:00 17:24:01 18:21:02 19:18:02 20:15:02 21:12:02 22:09:02 23:06:02 00:21:00 01:18:01 02:15:01 03:12:01 04:09:01 05:06:01 06:03:01 07:01:54 07:59:32 FBHP (psi) Record of Flowing Bottomhole Pressure (FBHP) Before and After Installing the SJP System Dp at wellhead=17.4 psi FBHP Dp =140 psi Time 19

20 Effectiveness of Downhole Jet Pumps for Well De-Liquification Traditionally liquid has been the motive flow. Effective mainly for maintaining production from shallow oil wells with very low GOR Experience in lifting heavy oil using a diluent fluid to reduce viscosity (Vega Field-AGIP) Limited experience in using gas as the motive flow HP gas is not effective in reducing the back pressure (FBHP) via the jet pump if liquids are produced Gas can be injected at bottomhole as lift gas via a number of specially designed nozzles to generate a good mixture. 20

21 Downhole Jet Pump - Gas as Motive Flow Some restrictions caused by wrong design of the jet pump. A GOOD EXAMPLE OF JET PUMP USED AS LIFT GAS SYSTEM 21

22 Well Revival using the Test Separator applies to both Gas and Oil Wells Production Line HP Gas Well Revival Gas SJP HP Liquid Well Revival Liquid SJP Test Header Gas LP Wells M Production Header Test Separator M Liquid 22

23 SJP to Raise the Pressure of Lift Gas For Increasing Gas Injection Depth SJP Recycle Gas lift Injection line Wellhead Well production To production process Surface Injection Gas Gas lift Compressor Gas lift injection valves Liquid level Increased depth of gas injection Pay zone Wellbore Pay zone 23

24 Extra Production gain with SJP System and Gaslift Produced Oil Flowrate High Pressure (HP) source [Gas or liquid] Wellcom System Gaslift injection system Production via Tubing Wellhead Well production Surface To downstream process Well Additional production Wellcom system & Gaslift injection Pay zone Lift gas Pay zone Gaslift injection Wellbore Gaslift Injection Flowrate 24

25 Comparison of Gas Lift with Lowering FWHP Depth Lift Gas (ft) 0 MMscfd 0 MMscfd 2 MMscfd 2 MMscfd 0 Dispersed Bubble Dispersed Bubble Dispersed Bubble Dispersed Bubble 700 Dispersed Bubble Dispersed Bubble Dispersed Bubble Dispersed Bubble 1425 Dispersed Bubble Dispersed Bubble Dispersed Bubble Dispersed Bubble 2125 Slug Dispersed Bubble Dispersed Bubble Dispersed Bubble 2850 Slug Slug Dispersed Bubble Dispersed Bubble 3550 Slug Slug Dispersed Bubble Dispersed Bubble 4275 Slug Slug Slug Dispersed Bubble 4975 Slug Slug Slug Slug 5700 Bubble Flow Slug Slug Slug 6400 S.P. Turbulent S.P. Turbulent Slug Slug 7125 S.P. Turbulent S.P. Turbulent Slug Slug 7825 S.P. Turbulent S.P. Turbulent Slug Slug 8546 S.P. Turbulent S.P. Turbulent Slug Slug 9246 S.P. Turbulent S.P. Turbulent Bubble Flow Bubble Flow 9971 S.P. Turbulent S.P. Turbulent S.P.Turbulent S.P.Turbulent S.P. Turbulent S.P. Turbulent S.P.Turbulent S.P.Turbulent FWHP (psig) BHP (psig) Oil flow rate (bbl/d) dq (bbl/d) Base case Water flow rate (bbl/d) Gas flow rate (MMscfd)

26 Economics Use of Surface Jet Pumps (SJP s) Low capital cost, no interference with wellbore Recovery of capital within a few weeks to a few months Short delivery period. On average about 8 to 14 weeks No manpower needed for operation Practically no operation cost/passive operation Practically no maintenance cost Alternative solutions more complex and more expensive Rental options available to minimise capital cost Short life period is economically acceptable Could enhance what is achieved by other downhole de-liquification systems, e.g. Gas lift + SJP 26

27 Closing Remark Simplicity and cost effectiveness makes SJP solutions very attractive & economical in most cases A good tool for well de-liquification before the situation worsens, requiring downhole systems In addition to economic benefits, eliminating intermediate compressors, deferring compressor upgrading or reducing liquid hold-up in pipelines are additional benefits The system can work well with gas lift or use of other downhole boosting systems Installing tie-in points during shut downs simplifies installation Efficiency of SJPs is around 30% but often uses wasted energy Rental option justifies very short operation life 27

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