An offshore reservoir contains multiple layers of formations (as seen in Figure 1). As the reservoir is supported by an aquifer and gas cap, the company has planned to drill a single vertical well through the reservoir formations to produce a liquid (oil) from a consolidated sandstone layer. Different completion options are developed, which are cemented perforated linear and open gravel packed with the sand screen. The casing schedule is shown in Table 1. Clay Shale 6800 ft 7000 ft Top of the reservoir Gas Gas Consolidated sandstone Oil Bottom of 7400 ft the reservoir Water 7700 ft Source rock Figure 1: Reservoir formation layers. . . . . . . . Common Data for all questions Reservoir Data Top of oil column = 7000 ft TVDSS Net pay thickness =331.2 ft . Drainage Area = 552 acres Bottom hole temperature = 140F Average permeability = 200 md Static bottom-hole pressure = 5312 psig at the mid perforation of 7200 ft Oil formation volume factor = 1.25 rb/stb Oil compressibility = 1.4 x 105 /psig Water compressibility = 3 x 10-5/psig Formation compressibility = 2.8 x 105 /psig Water saturation = 35% Reservoir Fluid Data API Gravity = 35 Gas gravity = 0.65 Oil viscosity = 6 cp GOR = 300 scf/bbl Bubble point = 2312 psig 0% water cut Formation fluid gradient = 0.38 psig/ft Test Data For Option 1: Cemented perforated linear well Flow rate =6624 stb/day at Pwf = 1812 psig For Option 2: Gravel packed well Flow rate = 8280 stb/day at Pwf = 2812 psig . . . . . The reservoir consists of consolidated to friable, heterogeneous, and fine-grained sandstone with limited clay content. It is slightly over pressured and bounded by competent shale layers. Table 1: The Provisional Casing Schedule Hole Size Casing/Liner setting Size (inch) (inch) 26 20 17 13 3 8 Setting depth (ft) From Surface Setting depth (ft) To TVDSS (shoe of casing/liner) 500 Surface 3500 124 5 9 8 Surface 5000 822 7 4500 6500 6500 7400 622 Option 1: Cemented perforated linear Option 2: Gravel Screen 6500 7400 Available production tubing size = 4.5 inch, OD and 4.0-inch, ID Question The completion engineer suggested testing two vertical oil-well completion strategies (shown in Table 1) not only to reduce the formation damage but also to prevent water conning. Therefore, answer the following questions using nodal analysis. A. Estimate the optimum operating condition (i.e. rate and bottom hole flowing pressure) and the choke size for both developed completion designs, if the wellhead is set at 331.2 psig. Use the vertical pressure gradient curves as attached below. Consider at least 4 points B. Explain how the pressure data for inflow and outflow curves are calculated for any one of the wells. C. Which option would you recommend? Answer with justification. Pressure in 100 PSIG 4 8 12 16 20 24 28 0 1 Vertical Flowing Pressure Gradients (All Oil) Tubing Size 4in. I.D. Producing Rate 1000 Bols/Day Oil API Gravity 35 API Gas Specific Gravity 0.65 Average Flowing Temp. 140 F 2 3 Length in 1000 Feet 7 0 8 25 50 Gas / Liquid Ratio - SCF Per BBL 9 100 10 500 400 300 200 II Iiiii 800 600 Hiii 1000 3000 1:1200 2000 1500 Pressure in 100 PSIG 12 16 4 8 20 24 28 1 2 Vertical Flowing Pressure Gradients (All Oil) Tubing Size 4in. I.D. Producing Rate 2000 Bbls/Day Oil API Gravity 35 API Gas Specific Gravity 0.65 Average Flowing Temp. 140 F 3 Length in 1000 Feet 7 0 8 25 50 Gas / Liquid Ratio - SCF Per BBL 9 100 10 400 300 200 600 500 !!! 800 1500 P1000 1200 Pressure in 100 PSIG 4 8 12 16 20 24 28 0 1 2 Vertical Flowing Pressure Gradients (All Oil) Tubing Size 4in. I.D. Producing Rate 3000 Bbls/Day Oil API Gravity 35 API Gas Specific Gravity 0.65 Average Flowing Temp. 140F 3 4 Length in 1000 Feet 7 0 8 25 50 Gas / Liquid Ratio - SCF Per BBL 9 100 10 400 300 200 111 800 600 500 !!1000 1200 1500 Pressure in 100 PSIG 0 4 8 12 16 20 24 28 0 1 2 Vertical Flowing Pressure Gradients (All Oil) Tubing Size 4in. I.D. Producing Rate 4000 Bbls/Day Oil API Gravity 35 API Gas Specific Gravity 0.65 Average Flowing Temp. 140 F 3 4 5 Length in 1000 Feet 7 0 25 8 Gas / Liquid Ratio - SCF Per BBL 50 9 100 10 400 300 200 600 500 !! 800 11000 1200 An offshore reservoir contains multiple layers of formations (as seen in Figure 1). As the reservoir is supported by an aquifer and gas cap, the company has planned to drill a single vertical well through the reservoir formations to produce a liquid (oil) from a consolidated sandstone layer. Different completion options are developed, which are cemented perforated linear and open gravel packed with the sand screen. The casing schedule is shown in Table 1. Clay Shale 6800 ft 7000 ft Top of the reservoir Gas Gas Consolidated sandstone Oil Bottom of 7400 ft the reservoir Water 7700 ft Source rock Figure 1: Reservoir formation layers. . . . . . . . Common Data for all questions Reservoir Data Top of oil column = 7000 ft TVDSS Net pay thickness =331.2 ft . Drainage Area = 552 acres Bottom hole temperature = 140F Average permeability = 200 md Static bottom-hole pressure = 5312 psig at the mid perforation of 7200 ft Oil formation volume factor = 1.25 rb/stb Oil compressibility = 1.4 x 105 /psig Water compressibility = 3 x 10-5/psig Formation compressibility = 2.8 x 105 /psig Water saturation = 35% Reservoir Fluid Data API Gravity = 35 Gas gravity = 0.65 Oil viscosity = 6 cp GOR = 300 scf/bbl Bubble point = 2312 psig 0% water cut Formation fluid gradient = 0.38 psig/ft Test Data For Option 1: Cemented perforated linear well Flow rate =6624 stb/day at Pwf = 1812 psig For Option 2: Gravel packed well Flow rate = 8280 stb/day at Pwf = 2812 psig . . . . . The reservoir consists of consolidated to friable, heterogeneous, and fine-grained sandstone with limited clay content. It is slightly over pressured and bounded by competent shale layers. Table 1: The Provisional Casing Schedule Hole Size Casing/Liner setting Size (inch) (inch) 26 20 17 13 3 8 Setting depth (ft) From Surface Setting depth (ft) To TVDSS (shoe of casing/liner) 500 Surface 3500 124 5 9 8 Surface 5000 822 7 4500 6500 6500 7400 622 Option 1: Cemented perforated linear Option 2: Gravel Screen 6500 7400 Available production tubing size = 4.5 inch, OD and 4.0-inch, ID Question The completion engineer suggested testing two vertical oil-well completion strategies (shown in Table 1) not only to reduce the formation damage but also to prevent water conning. Therefore, answer the following questions using nodal analysis. A. Estimate the optimum operating condition (i.e. rate and bottom hole flowing pressure) and the choke size for both developed completion designs, if the wellhead is set at 331.2 psig. Use the vertical pressure gradient curves as attached below. Consider at least 4 points B. Explain how the pressure data for inflow and outflow curves are calculated for any one of the wells. C. Which option would you recommend? Answer with justification. Pressure in 100 PSIG 4 8 12 16 20 24 28 0 1 Vertical Flowing Pressure Gradients (All Oil) Tubing Size 4in. I.D. Producing Rate 1000 Bols/Day Oil API Gravity 35 API Gas Specific Gravity 0.65 Average Flowing Temp. 140 F 2 3 Length in 1000 Feet 7 0 8 25 50 Gas / Liquid Ratio - SCF Per BBL 9 100 10 500 400 300 200 II Iiiii 800 600 Hiii 1000 3000 1:1200 2000 1500 Pressure in 100 PSIG 12 16 4 8 20 24 28 1 2 Vertical Flowing Pressure Gradients (All Oil) Tubing Size 4in. I.D. Producing Rate 2000 Bbls/Day Oil API Gravity 35 API Gas Specific Gravity 0.65 Average Flowing Temp. 140 F 3 Length in 1000 Feet 7 0 8 25 50 Gas / Liquid Ratio - SCF Per BBL 9 100 10 400 300 200 600 500 !!! 800 1500 P1000 1200 Pressure in 100 PSIG 4 8 12 16 20 24 28 0 1 2 Vertical Flowing Pressure Gradients (All Oil) Tubing Size 4in. I.D. Producing Rate 3000 Bbls/Day Oil API Gravity 35 API Gas Specific Gravity 0.65 Average Flowing Temp. 140F 3 4 Length in 1000 Feet 7 0 8 25 50 Gas / Liquid Ratio - SCF Per BBL 9 100 10 400 300 200 111 800 600 500 !!1000 1200 1500 Pressure in 100 PSIG 0 4 8 12 16 20 24 28 0 1 2 Vertical Flowing Pressure Gradients (All Oil) Tubing Size 4in. I.D. Producing Rate 4000 Bbls/Day Oil API Gravity 35 API Gas Specific Gravity 0.65 Average Flowing Temp. 140 F 3 4 5 Length in 1000 Feet 7 0 25 8 Gas / Liquid Ratio - SCF Per BBL 50 9 100 10 400 300 200 600 500 !! 800 11000 1200