THE FACILITY AND GAS LIFT

Transcription

1 THE FACILITY AND GAS LIFT John Martinez Production Associates ASME/API/ISO GAS LIFT COURSES THE FACILITY AND GAS LIFT SYSTEM COMPONENTS SYSTEM BACKPRESSURE NUMBER OF WELLS OPERATING FACTOR POWER INPUT AND SYSTEM BACKPRESSURE COMPRESSION OPTIONS DEHYDRATION OPTIONS MEASUREMENT, CONTROL, REMOTE TRANSMISSION FLOW RATE STABILITY & GAS INJECTION RATE 1

2 WHY IS GAS LIFT IMPORTANT? 2002 EM Gross Operated Oil Production Gas Lift 27% Rod Pump 11% Other 21% Progressive Cavity Pump 6% Naturally Flowing 52% Other 2% Electric Submersible Pump 2% 27% of EM gross operated oil production is gas lifted COURTESY EXXONMOBIL MIKE JOHNSON WHY IS GAS LIFT IMPORTANT? COURTESY SHELL JIM HALL 2

3 FACILITY EQUIPMENT DRIVES GAS LIFT AND IS THE LARGEST CAPITAL EXPENDITURE Onshore operator wanted more rig work and less wireline work Standby compressor added due to the remote location FACILITY EQUIPMENT DRIVES GAS LIFT AND IS THE LARGEST CAPITAL EXPENDITURE Offshore operator depends totally on wireline work Excellent dehydration was required because gas had CO 2 3

4 SYSTEM BACKPRESSURE NUMBER OF WELLS OPERATING FACTOR RATE PER WELL VARIES WITH SEPARATOR PRESSURE (SYSTEM BACKPRESSURE) EXPLORATION TEST RATES AND PVT DATA SIMULATE RESERVOIR BEHAVIOR SIMULATE WELL DELIVERY APPLY AN OPERATING FACTOR SIMULATE WELLS NEEDED BASED ON BOTH RESERVIOR AND DELIVERY PERFORMANCE SYSTEM BACKPRESSURE NUMBER OF WELLS OPERATING FACTOR 4

5 SYSTEM BACKPRESSURE NUMBER OF WELLS OPERATING FACTOR RESERVOIR PRESSURE, Psig & Water, % TARGET FIELD OIL RATE stb/d OPERATING FACTOR DAILY OIL REQUIRED stb/d 0% 100, ,530 25% 90, ,650 50% 50, ,240 SYSTEM BACKPRESSURE NUMBER OF WELLS OPERATING FACTOR RESERVOIR PRESSURE Psig & Water % 0% OIL RATE PER WELL psig INLET 2000 WELL psig INLET 54 OIL RATE PER WELL psig INLET 2200 WELL psig INLET 49 25% %

6 COMPRESSOR SUCTION AND DISCHARGE PRESSURE EFFECTS Discharge Pressure vs. Gas Lift Gas Requirement PRODUCTION RATE, GROSS STB/D PRODUCTION VS INJ. GAS & INJ. PRESS. WELL 1 & 2: INJ. PRESS. VARIES WITH INJ. DEPTH, P SEP = 50 PSIG PI=10, 7000', INJ PR = 1100 PSIG PI=10, 6000', INJ PR = 800 PSIG PI=10, 5000', INJ PR = 550 PSIG PI=1, 7000', INJ PR = 900 PSIG PI=1, 6000', INJ PR = 700 PSIG PI=1, 5000', INJ PR = 500 PSIG INJECTION GAS LIQUID RATIO, SCF/STB COMPRESSOR SUCTION AND DISCHARGE PRESSURE EFFECTS Suction Pressure vs. Gas Lift Gas Requirement PRODUCTION RATE, GROSS ST BBL/D PRODUCTION RATE, GROSS ST BBL/D PRODUCTION VS INJ. GAS & SEP. PRESS WELL 1: PI = 10 TBG = 4 1/2" FL = 3.958" & 2000 FT LONG 7000 FT P SEP = 20 PSIG P SEP = 50 PSIG P SEP = 100 PSIG P SEP = 150 PSIG INJECTION GAS LIQUID RATIO, SCF/STB PRODUCTION VS INJ. GAS & SEP. PRESS WELL 2: PI = 1 TBG = 2 7/8" FL = 2.9" & 2000 FT LONG 7000 FT P SEP = 20 PSIG P SEP = 50 PSIG P SEP = 100 PSIG P SEP = 150 PSIG INJECTION GAS LIQUID RATIO, SCF/STB 6

7 COMPRESSOR SUCTION AND DISCHARGE PRESSURE EFFECTS Optimize Compression Horsepower (BHP) 0.14 COMP. BHP/STB VS SEP. PRESS. WELL 1: PI = 10, RATE = 3000 STB/D, INJ P = 1100 PSIG WELL 2: PI = 1, RATE = 500 STB/D, INJ P = 900 PSIG BRAKE HP PER STB WELL 1 WELL SEPARATOR PRESSURE, PSIG COMPRESSION OPTIONS OPERATING EFFECTS WATER VAPOR IN THE GAS REQUIRES MORE POWER FOR COMPRESSION COMPARED TO SIMULATING DRY GAS HEAT DUTY FOR COOLERS GOES UP EXCHANGER SIZE BASED ON DRY GAS IS TOO SMALL TEMPERATURE OF GAS AND AMBIENT AVERAGE USED IN DESIGN, ACTUAL OPERATING CAN BE SIGNIFICANTLY HIGHER DRIVER DERATES, CANNOT SUPPY SUFFICIENT POWER COMPRESSOR CYLINDER (RECIP) OR IMPELLER WHEELS (CENTRIFUGAL) CANNOT MOVE THE DESIGN RATE 7

8 COMPRESSION OPTIONS - RECIPROCATING Reciprocating compression applied to smaller rates Good discharge pressure flexibility, limit on cylinder capacity Matched with gas engine or electric motor Dresser Industries COMPRESSION OPTIONS - CENTRIFUGAL Centrifugal compression applied to large rates offshore or internationally Large gas throughput in a small package Sensitive to gas composition changes Mated with gas turbine or electric motor Solar Gas Turbine Dresser-Clark 8

9 DEHYDRATION OPTIONS Triethylene glycol (TEG) is the common absorption dehydration method Mole sieves adsorb water vapor onto the surface in the bead DEHYDRATION OPTIONS WATER CONTENT BASED ON PRESSURE AND TEMPERATURE IS PREDICTABLE GPSA 9

10 DEHYDRATION OPTIONS HYRATE CONDITIONS ARE PREDICTABLE GPSA MEASUREMENT, CONTROL, REMOTE TRANSMISSION MEASURE INJECTION GAS LIFT GAS SINGLE PHASE FLOW STEADY PRESSURE (SHOULD BE) MOST RELIABLE (COMPARED TO PRODUCTION SEPARATOR) USE LOW POWER ACTUATED CHOKES USING SOLAR PANELS RADIO TRANSMISSION OF GAS MEASUREMENT DATA, WELLHEAD AND CASING PRESSURE AND TEMPERATURE 10

11 MEASUREMENT, CONTROL, REMOTE TRANSMISSION INSTALL DOWNHOLE PRESSURE SENSORS IN NEW WELLS MONITOR FLOWING BOTTOMHOLE PRESSURE ADJUST GAS LIFT GAS RATE TO KEEP MAINTAIN THE FLOWING BHP (NOT CONTINUOUSLY) MONITOR SUDDEN INCREASES WHICH INDICATE VALVE PROBLEM OR SHIFT IN POINT OF LEFT TRANSMIT DATA TO OPERATIONS CENTER, PLATFORM OR EVEN HOUSTON, FOR ANALYSIS AND ADJUSTMENT FLOW STABILITY AND GAS INJECTION RATE VALIDATED SIMULATION AND PRODUCION TESTS CAN DETECT UNDER PERFORMING WELLS DUE TO LIFT POINT SHIFT COMPRESSOR OUTAGE AND FREEZING SIMULATE VELOCITY AND FLOW PATTERN 11

12 FLOW STABILITY AND INJECTION RATE GAS RATE PERMITTING SLUG FLOW, VELOCITY LESS THAN 5 FT/SEC FLOW STABILITY AND INJECTION RATE GAS RATE PROMOTES STABLE ANNULAR FLOW, VELOCITY GREATER THAN 5 FT/SEC 12

13 FLOW STABILITY AND INJECTION RATE GAS RATE PERMITS SLUG/CHURN FLOW, VELOCITY ABOUT 5 FT/SEC GAS LIFT OPTIMIZATION DEPENDENT ON WELL PERFORMANCE AND FACILITY AVAILABILITY COMPRESSION AVAILABLE >99% EFFECTIVE DEHYDRATION FREEZING IS A COMMON FIELD PROBLEM 7 LB/MM (3 LB/MM IN COLD CLIMATES) GAS SYSTEM DESIGN LOW SUCTION PRESSURE HIGH DISCHARGE PRESSURE POWER REQUIRED PER BARREL IS LESS AT LOW SUCTION PRESSURE 13

14 GAS LIFT OPTIMIZATION DEPENDENT ON WELL PERFORMANCE AND FACILITY AVAILABILITY FIELD SIMULATION FOR DEVELOPMENT RESERVOIR PRESSURE DECLINE AND WATER INCREASE RATE VS INJECTION GAS DELIVERABILITY AT EACH RESERVOIR CONDITION WELL COUNT FOR DIFFERENT OPERATING CONDITIONS GAS MEASUREMENT MAKE THE INJECTION GAS METER RELIABLE MATE WITH LOW POWER CHOKE ACTUATOR AND REMOTE TRANSMISSION CAPABILITY FLOW STABILITY SIMULATE FLOW PATTERNS AND MATCH TO MEASURED AND OBSERVED BEHAVIOR ANNULAR FLOW VELOCITY > 5 FT/SEC 14