Flow Assurance Principles Applied to Unconventional Gas Well Deliquification

Transcription

1 Gas Well Deliquification Workshop Sheraton Hotel, February 23 25, 2015 Flow Assurance Principles Applied to Unconventional Gas Well Deliquification Rob Sutton, Consultant Steve Pohler, Marathon Oil Company Dr. Cem Sarica, U of Tulsa

2 The Classic Flow Assurance Problem Gas-Water Oil Hydrate Formation Salt/Scale Precipitation Paraffin Deposition Asphaltenes High Viscosity Emulsions Multiphase Flow Issues Slugging Corrosion Erosion 2

3 Talk Overview Unconventional Horizontal Gas Wells Barnett Fayetteville Haynesville Marcellus Woodford Deliquification Solution Drill Toe Up Wells Potential Consequences 3

4 Flow Assurance For Unconventional Gas Wells Gas-Water Oil Hydrate Formation Salt/Scale Precipitation Paraffin Deposition Asphaltenes High Viscosity Emulsions Multiphase Flow Issues Slugging Corrosion Erosion Note: Potential problems vary with play & producing conditions. Consider this for other evaluation scenarios. 4

5 Complex Well Geometries Undulations that cross 90 create traps 5

6 Gas Operating Envelope Gas Operating Envelope Superficial Liquid Velocity, ft/sec Superficial Liquid Velocity, ft/sec Typical Flow Patterns in Lateral -5 Hole Angle +5 Hole Angle TUFFP Unified Model Flow Pattern Map TUFFP Unified Model Flow Pattern Map Dispersed Bubble Dispersed Bubble 10 Slug 10 Annular Annular 1 1 Stratified Slug Stratified Superficial Gas Velocity, ft/sec Superficial Gas Velocity, ft/sec 6

7 Lateral Orientation 7

8 Toe Elevation & Tubing Placement 8

9 Traps Contribute to liquid slugging Accumulation site Liquids Debris Sand Scale Salt Corrosion 9

10 Gas Flow Thru Trap 10

11 Trap Count 11

12 Trap Location Multiple Traps No Traps Trap Near Toe 12

13 Lateral Length 13

14 Trap Location 14

15 Trap Location 15

16 Fraction of Lateral Beyond 1 st Trap 16

17 Formation Water Salinity 17

18 Salinity Profile with Time 18

19 Play Depth 19

20 Low Pressure Water Vapor Content 20

21 Relative Water Vapor Content (500 psi) 21

22 Vaporization & Salt Plugging Potential Assumptions: Reference to low temperature, low salinity Fayetteville at 500 psi Downhole temperature (see Slide 19) Vaporization & vaporization contrast (see Slide 20) Water salinity & salinity contrast (see Slide 17) Same gas & water rates Same trap geometry 22

23 Conclusions Reviewed major unconventional gas plays Play Depth (Pressure and Temperature) Produced Water Salinity Well Configurations Horizontal Well Deliquification Solutions Toe Up Lateral Orientation Multiphase Flow Patterns Downward flow regime: Stratified Uphill flow regime: Slug Traps Accumulation site for water and debris Isolate a significant portion of lateral 23

24 Conclusions Natural Gas Undersaturated at low BHP Water vapor content depends on pressure & temperature Water Evaporation Concentrates salts leading to salt/scale precipitation Flow Assurance Principles Ensure proper long term producibility of lateral Examine other aspects of well Ensure deliquification, slugging & corrosion mitigation goals are attained Reservoir inflow impairment 24

25 Conclusions Plays with higher water salinity and higher temperature are more problematic Greater potential for salt/scale deposits Higher water vaporization potential Reduced time frame for apparent problems Solution to problem Avoid traps in toe-up wells Avoid low bottomhole pressure operations Utilize equipment to keep water moving in the lateral 25

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