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Condensate Stabilization and Exportation - OTC 2015 Technical Session Presentation
- 1. OTC-25722-MS Offshore Condensate Stabilization and Exportation William Vocke; Daniel Newman, P.E.; Robert Villio; Charles Cook, Ph.D.; Denis Taylor, P.E. Audubon Engineering Solutions, LLC.
- 2. LLOG Delta House FPS • Mississippi Canyon area of Gulf of Mexico • ~4,500 ft. of water • Initial nameplate design capacity • 80,000 BPD of oil • 200 MMSCFD of gas • Initial design fluid properties • ~2000 GOR • 28-32° API INTRODUCTION Slide 2 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 3. CONCEPT DEVELOPMENT • New PVT Data received • ~2300 GOR • 35° API • Rich in C3, C4’s, and C5’s • Created a significant recycle loop Slide 3 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 4. CONCEPT DEVELOPMENT • New PVT Data received (cont.) • Questionable lab data • Could not be duplicated in process simulators • Option Study initiated Option 1 – Condensate Injection Option 2 – Crude Stabilization & Condensate Injection Slide 4 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 5. CONCEPT DEVELOPMENT • Re-analyzed PVT data received • ~2100 GOR • 37° API • Less C3 and C4’s • Process simulators duplicated lab results ±10% • Significant recycle loop remained • Option 2 abandoned • Overly complex • Large weight implications Slide 5 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 6. CONCEPT DEVELOPMENT • Comparison of Initial Design Rates versus New Rates Based on Corrected Compositional Data Slide 6 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. 5.2 MMSCFD 13.6 MMSCFD 12.7 MMSCFD 20.6 MMSCFD 11.3 MMSCFD 17.1 MMSCFD 217 BPD 139 BPD 234 BPD 1621 BPD 1037 BPD 2660 BPD
- 7. CONCEPT DEVELOPMENT • Significant oil production lost to Gas Pipeline with Option 1 • Hybrid of Option 1 and Option 2 was evaluated Condensate Stabilization System • Liquids from FGC were dewatered • Liquids roughly distilled • Bottoms product recycled to bulk liquid separation train • Overhead product partially condensed Overhead vapors routed to compression Overhead liquids metered and injected into Gas Pipeline Slide 7 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 8. CONDENSATE STABILIZATION SYSTEM One-Column Format Slide 8 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 9. CONCEPT DEVELOPMENT • Condensate Stabilization System • Reduced compression of Original Design • Increased Sales Oil of Option 1 • Achieved Sales Oil RVP Specification Slide 9 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. Sales Oil Rates [BPD] Option 1 Condensate Stabilization Sales Oil Gained Case 1 80,706 81,241 535 Case 2 80,733 81,319 586 Case 3 80,966 81,662 696 Case 4 81,027 81,819 792
- 10. PROPOSED OPERATION Seasonal Sensitivities • Ambient Temperatures High - 120°F Aerial Cooler Outlet Temperature Low - 100°F Aerial Cooler Outlet Temperature • Oil Pipeline RVP Specification 8.6 psia: Apr-Sept; “Summer” 9.6 psia: Oct-Mar; “Winter” Slide 10 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 11. PROPOSED OPERATION Seasonal Sensitivities Slide 11 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. Summer Winter Summer Winter RVP [psia] 8.6 9.6 8.6 9.6 Cooler Temp [°F] 120 120 100 100 Reboiler Temp [°F] 315 250 315 260 FWKO Feed Ratio (Note 1) [BBL/1000 BBL Crude] 32 39 33.5 44.5 NGL Production Ratio [BBL/1000 BBL Crude] 10 1.5 18 8.5 Stab Cond Production Ratio [BBL/1000 BBL Crude] 10 16.5 10 17.5 Note 1: Ratio reflects total liquids (water and hydrocarbons) feeding the Freewater Knockout.
- 12. PROPOSED OPERATION Water Handling Considerations • Potential to form hydrates in Gas Pipeline • Causes of water presence in Overhead Separator: Freewater Knockout upset Poor Coalescing Filter performance Excessive cooling of overhead product Inadequate draining of Stabilizer water sump Slide 12 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 13. CONCLUSION • Delta House reservoir rich in C3, C4’s, & C5’s High compression requirements Difficulty meeting Sales Oil RVP specification Sales Oil potentially lost • Condensate Stabilization helped optimize facility Reduced compression Provided additional means of RVP control Recovered more liquids to sell as oil Slide 13 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 14. Acknowledgements Thanks to Co-Authors Robert Villio; Charles Cook, Ph.D.; Denis Taylor, P.E. Audubon Engineering Solutions, LLC. Special Thanks to LLOG Exploration, LLC. Rick Fowler, Bruce Cooley, and Craig Mullet Slide 14
- 15. Slide 15 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. QUESTIONS & DISCUSSION
- 16. SLIDE TITLE HERE One-Column Format Slide 16 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 17. APPENDIX Hydrocarbon Content Comparison Slide 17 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. Component Incorrect PVT Data [mol%] Correct PVT Data [mol%] Methane (C1) 51.74 61.23 Ethane (C2) 6.83 6.48 Propane (C3) 7.69 4.42 Isobutane (iC4) 1.84 0.76 N-butane (nC4) 5.06 1.97 Isopentane (iC5) 1.79 0.93 N-pentane (nC5) 2.17 1.31 C6 (generic) 3.20 2.96 C7+ 18.62 19.09
- 18. APPENDIX Comparison of VRU compression between the Original Design, Option 1, and Condensate Stabilization. Slide 18 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. VRU [MMSCFD] Original Option 1 Condensate Stabilization Case 1 4.69 2.93 3.13 Case 2 8.01 3.03 3.21 Case 3 3.28 2.45 2.79 Case 4 5.28 2.42 2.87
- 19. APPENDIX Comparison of FGC 1st Stage compression between the Original Design, Option 1, and Condensate Stabilization. Slide 19 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. FGC 1st Stage [MMSCFD] Original Option 1 Condensate Stabilization Case 1 13.62 9.81 10.12 Case 2 19.37 9.52 9.79 Case 3 11.59 9.39 10.15 Case 4 15.37 9.06 9.89
- 20. APPENDIX Comparison of FGC 2nd Stage compression between the Original Design, Option 1, and Condensate Stabilization. Slide 20 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. FGC 2nd Stage [MMSCFD] Original Option 1 Condensate Stabilization Case 1 20.62 17.26 18.68 Case 2 22.84 16.74 18.08 Case 3 19.22 17.00 19.15 Case 4 21.18 16.50 18.94
- 21. APPENDIX Comparison of Sales Oil between the Original Design, Option 1, and Condensate Stabilization. Slide 21 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E. Sales Oil [BPD] Original Option 1 Condensate Stabilization Case 1 81,549 80,706 81,241 Case 2 81,903 80,733 81,319 Case 3 81,755 80,966 81,662 Case 4 82,048 81,027 81,819
- 22. APPENDIX NGL Pumping, Metering, and Exportation Slide 22 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
- 23. CONCEPT DEVELOPMENT Option 1 • Bulk liquid separation of Original Design intact • Condensate processing added • De-watering • Condensate injected into Gas Pipeline Reduced compression Met RVP specification Simple Potential sales oil lost Option 2 • Full crude stabilizer replaced some bulk liquid separation • Sales oil product • Condensate product • Condensate de-watering • Condensate injected into Gas Pipeline Reduced compression Met RVP specification Complex; large and heavy High heating requirements Slide 23 OTC-25722-MS • Offshore Condensate Stabilization & Exportation • William Vocke; Daniel Newman, P.E.
Editor's Notes
- Good day. My name is Daniel Newman; this is William Vocke. We are with Audubon Engineering. Thank you for coming to our presentation on Offshore Condensate Stabilization and Exportation as part of the LLOG Delta House topsides development.
- This slide shows a picture of the Delta House Floating Production System. Audubon Engineering was tasked with the engineering and design of the topsides. Delta House is located in Mississippi Canyon block 254 in approx. 4,500 ft of water. [See slide – list capacities]. Fluid properties are from an analogous well located in Mississippi Canyon; it was assumed that Delta House’s reservoir fluids would be similar in nature. Engineering and design efforts began prior to completion of drilling any Delta House wells.
- Approximately 6 months into the design effort, we received fluid samples for some of the reservoirs. One of the samples was expected to be representative of the majority of the Delta House production. The analysis indicated a significant deviation from the original fluid basis. The new sample was approx. 2300 GOR and 35 API. It was very rich in propane, butanes, and pentanes. It posed significant problems meeting oil pipeline RVP specification. It also resulted in a large recycle loop with liquids dropping out in the scrubbers that re-flashed in the oil train thus drastically increasing compression requirements.
- When we looked at the lab data, we could not reproduce it in our process simulations. It looked suspicious due to the high concentrations of propane, butanes, and pentanes. We requested LLOG to have the sample re-analyzed. We began evaluating different options in order to reduce compression and meet the oil pipeline RVP spec. Option 1 was condensate injection. Option 2 was full crude stabilization and condensate injection.
- A few months into the option study, we received the re-analyzed well data. It was significantly different from the original lab data. It was approx. 2100 GOR and 37 API, but our process simulations were able to reproduce the lab tests within an acceptable margin of error. We based all new design and evaluation on this new analysis. A large recycle loop still remained when the flash gas compressor liquids were recycled to bulk liquid separation. Option 2 was abandoned to its complexity, weight, and was not as advantageous with the re-analyzed well fluid.
- This slide gives you an idea of the differences between the original design rates prior to any well data versus the new rates based on the re-analyzed well fluid for compression and the scrubbers. These rates are based on a process system that does not incorporate Option 1 nor Option 2. There is a significant increase in overall compression requirements and the liquid rates. It is not as bad as the erroneous lab data. We still needed to find a means to reduce compression and meet the oil RVP spec. We preferred to maintain a traditional bulk liquid separation train similar to Option 1.
- The main drawback to Option 1 was that significant oil production was lost to the Gas Pipeline since heavier components were not being recovered. A hybrid of Option 1 and Option 2 was developed. [See slides]
- This is a high level sketch of the Condensate Stabilization System.
- From our review of the Condensate Stabilization system, it allowed us to reduce compression from the original design, increased sales oil over Option 1, and allowed the sales oil to meet RVP since lighter components were not being recycled. We gained approx 500-800 BPD of sales oil.
- We looked at various seasonal sensitivities to determine the impacts on the Stabilization System. Since the platform has aerial coolers, the ambient temperature significantly impacts the rates of the Stabilization System. We added VFDs to all of the aerial coolers to help control the outlet temperatures. We also looked at the impacts of the seasonal changes in RVP spec. The higher RVP allows more light hydrocarbons to be present in the sales oil. The seasonal sensitivities were performed in order to ensure the design would be able to handle the potential operating conditions and to ensure there was acceptable turndown.
- This slide shows the results from our seasonal sensitives. It shows reboiler temperatures, FWKO feed ratios, and production ratios. We have a means of temperature control on the cooler, but we did not think we would be able to hold a completely constant outlet temperature so we allowed for a temperature variation of 20F. The main point of interest is the NGL production and the Stab Cond that is recycled to the bulk liquid separation train. Significantly more oil is recovered in the winter months when the RVP spec is higher. There is also a significant impact due to ambient temperatures. The reboiler temperature is varied in order to maximize oil production and to help control the RVP spec.
- Stabilization has some water handling concerns that must be addressed. Water can have severe ramifications on stabilization system and export. If water is present in the NGL, hydrates can form in the Sales Gas Pipeline. The overall water content in the sales gas pipeline should be less than 4 lb/MMSCF, but an upset in the Stabilization system could quickly add a significant amount of water to the pipeline. [see slides for sources of water problems and talk about mitigation of water issues]. Water boot in stabilizer, cooler temp control, interface level monitoring on overhead separator.
- Sum up and wrap up
- Option 1 left the bulk liquids separation train intact. We took the condensate from the flash gas compressor scrubbers, dewatered, and pumped into the sales gas pipeline. It reduced compression significantly and eliminated the recycle loop. It was very simple. The drawback was that we would be losing oil to the Sales gas pipeline. Some of the heavier components (C5+) of the condensate were not being recovered and sold as oil. Option 2 was a full crude stabilizer. We removed some stages of separation from the bulk liquid train. The intention was to maximize the oil production and minimize compression. The stabilizer provided several products – crude oil, condensate, and vapors. [See slide]