Well Performance Experience with Plastic Pipe

Transcription

1 Well Performance Experience with Plastic Pipe Alison Bondurant Bryan Dotson 3rd European Conference on Gas Well Deliquification September 15-17, 2008

2 Agenda What is plastic pipe? Why run plastic pipe? Conclusions 2

3 What is plastic pipe? Types run by BP: Tension Set hang off from wellhead Compression Set set on a packer or stop Pre-installed threaded steel tubing with thick plastic lining Type Vendor/Brand Name Tension Set Polyflow Thermoflex BP Installs 9 (6 with Fortron) Picture Compression Set Trican Polybore Pre-Installed Western Falcon Enertube (also Polycore, Ultratube) 3 3 3

4 Why run plastic pipe? Plastic pipe is a cost effective alternative to steel Technical Aspects: Corrosion Resistance Temperature Bitumen Prevention Relative Roughness 4

5 Corrosion Resistance Simply Plastic doesn t corrode! 1 BP trial specifically for corrosion resistance: Western Falcon Enertube pre-installed plastic lining Designed to limit the permeability of acid gases (CO 2 in the trial) Iron counts: 150 (steel tubing with corrosion inhibition treatments) decreased to 45 (Enertube with no corrosion inhibition) Have not pulled any plastic installations to date to visually confirm corrosion resistance If have corrosion issues, plastic is a good option to consider 5

6 Temperature Heat Transfer Theory The Hotter the Fluid = More Water Staying in the Vapor Phase Location Temperature ( o F/ o C) Pressure (psi / bar) Capacity to Hold Water as Vapor (lb/mmscf) Surface 62 / /4 182 Surface 65 / /4 201 Surface 72 / /4 255 Surface 82 / /4 354 For a given flowrate, Produced Fluid Temperature at surface is dependent on: Temperature of the earth Overall Heat Transfer Coefficient Thermal Conductivity (k) alone can be misleading: Polyethylene: k = Steel: k = 46 Q=U to A T = U to h f h c h r h co Where: U to : Overall heat transfer coefficient (HTC) h f : HTC, forced convection inside tubing h c : HTC, natural convection in annulus h r : HTC, radiation from tubing to casing h co : HTC, conduction through tubing Adding insulation only affects k and radius; all other HTC factors are basically unchanged. ( r to ) r to ln(----) ( r ti ) h co = k 6

7 Temperature Example BP Oklahoma, USA Steel Tubing 2-7/8" (2.441"ID) with Plunger Oklahoma, USA Daily Averages Wellwork Western Falcon Enertube 1.7" ID Temperature F Rate MSCFD Casing psig Tubing psig 300 Parameter /1/07 Tubing 10/1/07 11/1/07 Gas 12/1/07 Rate 1/1/08Tubing Temperature 1/31/08 DateAverage Average (MSCFD) ( o F/ o C) 2.441" ID Steel / " ID Western Falcon Enertube / 18 7

8 Temperature Conclusions What is the effect of this 3 o F (1 o C) temperature increase? Location Temperature ( o F/ o C) Pressure (psi / bar) Capacity to Hold Water as Vapor (lb/mmscf) Surface 62 / /4 182 Surface 65 / /4 201 Surface 72 / /4 255 Surface 82 / /4 354 Reservoir (Example) 170 / / Required Temperature to keep Water as Vapor = 82 o F (28 o C) Prosper Model of this well a 20 o F (11 o C) increase! With 0.2 of plastic thickness, full model of system gives 1 F increase In line with observed increase Reservoir can hold 350 lb/mmscf = 1bbl/MMscf Matches observed water production from this well 8

9 Bitumen Prevention Bitumen: A sticky, tar-like form of petroleum Must be heated or diluted before it will flow At room temperature, it is like cold molasses Canada Situation: Gas cap on top of heavy oil / tar sands Produce pure methane & tar Plugs up tubing & surface equipment Tested Fortron-lined velocity string (Polyflow) Consists of two polymer layers reinforced with Kevlar threads Lab testing showed little to no bitumen sticking 6 Trials in Canada No conclusive evidence to date 9

10 Relative Roughness Theory Theoretical FBHP For Reduced ID Plastic, Reduced ID Steel, and Standard ID Steel Grey's Modified, 1 BBL/MMSCF, 60 psig FTP, 8400 foot depth 300 Highly dependent on the Pressure Sensitivity of the 280 formation Flowing Bottom Hole Pressure, psig Roughness has much more impact on pressure at high flow rates Roughness has less effect around the minimum stable flow Hypothetical 1.71" ID steel for comparison of roughness 140 Note: 120 Calculated, not measured. Doubts 1.71" ID Plastic about accuracy of all VLP methods. Roughness for Plastic " ID Steel inches, Steel inches 1.995" ID Steel Rate, MSCFD Commercially available Enertube plastic lined 2-7/8" with 1.71" ID Commercially available 2-3/8" steel pipe 10

11 Downhole Pressure (psi) Relative Roughness Example 1 BP Canada 2-3/8 Tbg (1.995 ID) 1.08 ID Polyflow (BP) 1.08 ID Polyflow Production Rate (mscfd) 2 Production Production (Mscfd) (mscfd) Friction Reduction Calculated (psi / bar) / / / 1.2 Original IPR Adjusted IPR Calculated (Grey) Friction Reduction Smooth plastic ( in.) over Steel ( in.) 1. Unstable Production observed 210 Mscfd Minimum Stable Flow: 340 Mscfd (J-curve), 190 Mscfd (Coleman), 250 Mscfd (Turner) 2. Installed 1.08 ID Polyflow velocity string Increased to 310 Mscfd w/ less downtime Conclusions: Higher benefit than predicted = didn t have correct IPR 1.25 ID Velocity String may have been a better fit in retrospect Coleman critical flow method not applicable, showed a velocity string was not needed At 300Mscfd, Polyflow has a calculated 9 psi advantage over steel BUT going to 1.25 ID steel has 25 psi advantage over 1.08 ID plastic 11

12 Relative Roughness Example 2 BP Oklahoma, USA Rate, MSCFD Enertube Installation Review (July 2008) Note: Line pressure averaged 85 psig over time interval and did not change appreciably. Rate MSCFD Casing psig Prior Situation: 2-3/8" steel tubing set to 13766' (just above Spiro perfs) through packer. Panola and Atoka open on annulus. In 1983, perforated the tubing at 10042', just above the Panola perfs. 4/30/08: Set Enertube Polyliner 2-7/8" 7.9# tubing (1.995" ID) to 10037', just above Panola perfs. Essentially same downhole configuration as Oct. 07 with same ID, but plastic surface. 10/17/07: Found obstruction in 2-3/8" (above Spiro, below Panola) and perforated the 2-3/8" at 5830' (just above the Atoka). Well beginning to impair due to liquids, so cycling. Interpretation: Panola did not flow for about 6 months & recharged about 20 MMSCF; accounts for high rate May-June. Calculated friction reduction on plastic ~ 10 psi Jan-07 Feb-07 Mar-07 Apr-07 May-07 Jun-07 Jul-07 Aug-07 Sep-07 Oct-07 Nov-07 Dec-07 Jan-08 Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Pressure, psig Date 12

13 Relative Roughness Conclusions Highly dependent on the Pressure Sensitivity of the formation Canada example: 10psi = ~300mcfd Oklahoma example: 10 psi = ~0mscfd Choosing the Right Diameter is key May gain a little extra from roughness reduction if high productivity Roughness reduction will have more impact if undersize the tubing 13

14 Conclusions Plastic pipe is a cost effective option for velocity strings Great for corrosion resistance Benefits from temperature were not seen in field trial Would need 7 times the temperature increase observed Bitumen prevention has not been confirmed to date Relative roughness is highly dependent on the Pressure Sensitivity of the Formation 14

15 Thanks To Bryan Dotson Bill Baack Kelly Richardson Heath Mireles Josh Chebul Bob Wiley Henry Nickens George King Jay Wright (Polyflow) Polybore Western Falcon Trican 15

16 Questions? 16