BLOWOUT RATE EVALUATIONS FOR THE 9-5/8" CASING DESIGN TRANSIENT RESERVOIR RESPONSE EVALUATIONS. Acona Flow Technology AS

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1 MEMO BLOWOUT RATE EVALUATIONS FOR THE 9-5/8" CASING DESIGN TRANSIENT RESERVOIR RESPONSE EVALUATIONS ODA (BUTCH) DEVELOPMENT WELLS (PL405) Rev 1 17 th October 2016 Acona Flow Technology AS Visiting address: Hydrovegen 67, NO-3936 Porsgrunn Norway Postal address: P.O. Box 1045, NO-3905 Porsgrunn, Norway T: Org. NO VAT

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3 Disclaimer The data forming the basis on this report has been collected through the joint effort of Acona Flow Technology AS and Acona AS, hereinafter named Acona. Acona has gathered the data to the best of our knowledge, ability, and in good faith from sources to be reliable and accurate. Acona has attempted to ensure the accuracy of the data, though, Acona makes no representations or warranties as to the accuracy or completeness of the reported information. Acona assumes no liability or responsibility for any errors or omissions in the information or for any loss or damage resulting from the use of any information contained within this report. This document may set requirements supplemental to applicable laws. However, nothing herein intends to replace, amend, supersede or otherwise depart from any applicable law relating to the subject matter of this document. In the event of any conflict or contradiction between the provision of this document and applicable law as to the implementation and governance of this document, the provision of applicable law shall prevail. Revision and Approval Form TECHNICAL REPORT Title Blowout rate evaluations for the 9-5/8" casing design with and without transient reservoir response Report No. Revision Date Rev. No. AFT MEMO Client Client Contact Client Reference Centrica E&P Norway Stian Brevik - Rev. No. Revision History Date Prepared Approved 0 Issued for comments V.Grüner T.Rinde 1 Comments included V.Grüner T.Rinde Name Date Signature Prepared by Vegar Grüner Approved by Trygve Rinde Revision No.: 1 Revision Date: Page 3/18

4 Table of Contents 1 INTRODUCTION CASE DATA General input data Case description and Well design Transient blowout reservoir response METHOD DISCUSSION TRANSIENT P90 APPROACH P90 estimates transient approach Data analysis 45 days P90 estimate Data analysis 60 days P90 estimate Data analysis 75 days P90 estimate Data set and frequencies REFERENCES APPENDICES Appendix A : About Acona Flow Technology AS Revision No.: 1 Revision Date: Page 4/18

5 Figures Figure 1: Well schematics MPROD2-9-5/8" casing design... 7 Figure 2: MPROD2 PARTIAL reservoir exposure - 9-5/8" casing - Transient reservoir response... 8 Figure 3: MPROD2 FULL reservoir exposure - 9-5/8" casing - Transient reservoir response... 9 Figure 4: Expectation curves for volume/frequencies and possible simplification strategies Figure 5: Histogram - data set for 45 days transient P90 evaluation Figure 6: Histogram - data set for 60 days transient P90 evaluation Figure 7: Histogram - data set for 75 days transient P90 evaluation Tables Table 1: Transient model - flowpath scenario listing... 8 Table 2: Probability distribution and resulting data multiplier MPROD2 - Surface release point Table 3: Transient P90 estimates Table 4: Data groups and frequency transient P90 evaluation Abbreviations AFT ANN AOF BHA BHP BOP CGR DHSV DP FBHP GOR ID IPR LPM MD MSL NOROG N/G OD OH OIM OWC RKB sg TD TVD Acona Flow Technology AS Annulus Absolute open flow Bottomhole assembly Bottomhole pressure Blowout preventer Condensate gas ratio Down hole safety valve Drillpipe Flowing bottomhole pressure Gas oil ratio Inner diameter Inflow performance relationship Litres per minute Measured depth Mean sea level Norwegian Oil and Gas Association Net/Gross Outer diameter Open hole Offshore Installation Manager Oil water contact Rotary Kelly bushing Specific gravity Total depth True vertical depth Revision No.: 1 Revision Date: Page 5/18

6 1 INTRODUCTION This memo sum up and discuss blowout rate calculations performed for the drilling operations of a typical Oda development production well. Blowout rates resulting from both initial/virgin reservoir pressure as well as rates resulting from an expected transient reservoir response during a blowout are discussed and presented. Main focus of this memo is to discuss and present the use of transient reservoir response in blowout rate calculations and subsequent estimation of P90 estimates. The transient reservoir behaviour is run on the best available models and is based on updated reservoir models in Eclipse. The main reason for using a transient model approach is to provide a significantly larger data set in order to provide a more confident P90 rate estimate for use in environmental evaluations. Simulations are performed and modelled based on a representative well, MPROD2. MPROD2 is chosen as it represents the highest potential for flow and thus gives the worst case discharge scenario. For the full study and discussion of probability distributions, input data and kill requirements, please refer to Acona report AFT [2]. 2 CASE DATA 2.1 General input data Please refer to Acona report AFT [2] for specific data on reservoir and fluid properties, and resulting inflow performance etc. 2.2 Case description and Well design The following scenario is evaluated in this memo: MPROD2, 1 st producer: Blowout through 10 ¾ x 9 ⅝ casing while drilling Ula in the 8 ½ reservoir section Blowout rates for 5m (partly) and 100% (fully) exposure of Ula Fm based on transient reservoir response during a blowout. The well is to be drilled as a deviated well, and the following well schematics have been used in this study: MPROD2: 9 ⅝ casing to surface. 30 conductor pipe 182 m MD/TVD RKB 20 surface casing 461 m MD/TVD RKB 16 liner 930 m MD/TVD RKB 13 ⅜ intermediate casing 2170/2116 m MD/TVD RKB 10 ¾ x 9 ⅝ reservoir casing 2645/2454 m MD/TVD RKB with 430 m MD/TVD RKB An 8 ½ section will be drilled into the reservoir with 5 ½ drillpipe OD to 2785/2529 m MD/TVD RKB Revision No.: 1 Revision Date: Page 6/18

7 MPROD2 RKB-MSL 44 m Drilling BOP Sealevel Seabed 66 m MSL X/O 430 m MD/TVD RKB 30" Conductor 182 m MD/TVD RKB 20"csg 461 m MD/TVD RKB 13 ⅜"csg 2170/2116 m MD/TVD RKB 10 ¾ x 9 ⅝"csg 2645/2454 m MD/TVD RKB Top Reservoir Depth: 2478 m TVD RKB Pres: 376 bara Tres: 113 C 8 ½" OH 2785/2529 m MD/TVD RKB Figure 1: Well schematics MPROD2-9-5/8" casing design 2.3 Transient blowout reservoir response Transient modelling for release to surface/drill floor is prioritized over a seabed release point as it gives slightly higher blowout rates to sea. Seabed release rates are assumed represented by surface release rates due to the shallow water, as a conservative approach. 12 different flowpath scenarios are modelled and run to match flowpath distribution data as used in the basic approach for calculation of risked rates [2]. These scenarios are: Revision No.: 1 Revision Date: Page 7/18

8 Oil rate [Sm³/d] TECHNICAL REPORT Table 1: Transient model - flowpath scenario listing Scenario Flowpath BOP Status Exposure Status Status 1 Open Open hole 2 Restricted 3 Open Partial reservoir exposure Annulus 4 Restricted 5 Open Drill pipe 6 Restricted 7 Open Open hole 8 Restricted 9 Open Full reservoir exposure Annulus 10 Restricted 11 Open Drill pipe 12 Restricted Figure 2 and Figure 3 show the resulting transient reservoir response for both partial and full reservoir exposure, measured in oil rate per day, over a blowout duration of 75 days OH - Open ANN - Open DP - Open OH - Restricted ANN - Restricted DP - Restricted Duration [days] Figure 2: MPROD2 PARTIAL reservoir exposure - 9-5/8" casing - Transient reservoir response Revision No.: 1 Revision Date: Page 8/18

9 Oil rate [Sm³/d] TECHNICAL REPORT OH - Open ANN - Open DP - Open OH - Restricted ANN - Restricted DP - Restricted Duration [days] Figure 3: MPROD2 FULL reservoir exposure - 9-5/8" casing - Transient reservoir response 3 METHOD DISCUSSION TRANSIENT P90 APPROACH The transient reservoir response is integrated into the blowout rate evaluation in order to provide a significantly larger data set on which the P90 rate estimate is based on. The method is based on the OLF Guidelines for estimation of blowout potentials [1]. Conservative simplifications can be made, as illustrated in Figure 4, where curve A represents a rigorous study with extensive parametric analyses, whereas curve B and C represent conservative simplifications. All scenarios A, B and C are acceptable; alternative A is most work intensive, and alternative C is least work intensive, but most conservative. This study is based on a full A (i.e.alternative A with extensive parameter variation), thought to give the best available data set for P90 rate estimation. The background for the P90 rate is to obtain an estimate that will represent 90 % of all possible blowout rates, for use in environmental response evaluations. The typical approach for P90 rate estimation is to base the estimate on the 12 rates represented by Table 1, and incorporate the flowpath probability distribution of Table 2 [2]. This provides a small (12) but usually sufficient data set for P90 estimation. For the Oda development Centrica has put significantly more effort into providing a more detailed P90 rate estimate in order to most accurately evaluate the response requirements. The estimated maximum duration of a potential blowout is 75 days [2]. P90 estimates have been calculated for three blowout durations: 45, 60 and 75 days, where including the 45 first days are the most conservative approach. Using the data containing the 45 first days of blowout data as an example, this will produce a data set of: 45 x 12 = 540 rates. In addition the data set needs to be expanded according to the probability [2] for each of the 12 scenarios to occur, ref. Table 2. Note that prior to expanding the data set based on the probability distribution, the data set is reduced to 10 scenarios; 45 x 10 = 450 rates, as Row 1 and 2 of Table 2 have 0% probability to occur according to the scenario assumptions used [2]. Revision No.: 1 Revision Date: Page 9/18

10 The Multiplier column lists how many instances of the rates from each scenario that is present in the final data set, according to the probability of this scenario to occur. Accounting for the probability, the data set is expanded to contain 45 x 100 = 4500 rates. From this the P90 estimate is estimated. Figure 4: Expectation curves for volume/frequencies and possible simplification strategies Table 2: Probability distribution and resulting data multiplier MPROD2 - Surface release point Scenario Flowpath BOP Status Total Risk Multiplier Prob. % Exposure Prob. % Status Prob. % Status [%] [-] 40 Partial reservoir exposure 60 Full reservoir exposure 0 Open hole 86 Annulus 14 Drill pipe 16 Open hole 72 Annulus 12 Drill pipe 30 Open Restricted Open Restricted Open Restricted Open Restricted Open Restricted Open Restricted Total sum: P90 estimates transient approach The P90 estimates, when using data from the transient reservoir model and evaluating for different cut-of times with respect to data to include, are show in Table 3. Table 3: Transient P90 estimates Data included P90 oil rate [days] [Sm 3 /d] Revision No.: 1 Revision Date: Page 10/18

11 Percentile More Frequency TECHNICAL REPORT 4.1 Data analysis 45 days P90 estimate The data set for the 45 days analysis contains 4500 rates. This accounts for unique rates for each day for the different scenarios, and with rates for each scenario multiplied according to probability of occurrence, as described in Section 3. A graphical presentation is found in Figure 5, while tabulated data is found in Section 4.4, Table 4. Figure 6 graphically present how the 90 percentile is being obtained Oil rate (range) [1000 Sm³/d] Figure 5: Histogram - data set for 45 days transient P90 evaluation 100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0 % Oil rate [Sm³/d] Figure 6: Obtaining 90%-ile estimate based on 45 days transient data - graphical presentation Revision No.: 1 Revision Date: Page 11/18

12 Percentile Frequency TECHNICAL REPORT 4.2 Data analysis 60 days P90 estimate The data set for the 60 days analysis contains 6000 rates. A graphical presentation is found in Figure 7, while tabulated data is found in Section 4.4, Table 4. Figure 8 graphically present how the 90 percentile is being obtained Oil rate (range) [1000 Sm³/d] Figure 7: Histogram - data set for 60 days transient P90 evaluation 100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0 % Oil rate [Sm³/d] Figure 8: Obtaining 90%-ile estimate based on 60 days transient data - graphical presentation Revision No.: 1 Revision Date: Page 12/18

13 Percentile Frequency TECHNICAL REPORT 4.3 Data analysis 75 days P90 estimate The data set for the 75 days analysis contains 7500 rates. A graphical presentation is found in Figure 9, while tabulated data is found in Section 4.4, Table 4. Figure 10 graphically present how the 90 percentile is being obtained Oil rate (range) [1000 Sm³/d] Figure 9: Histogram - data set for 75 days transient P90 evaluation 100 % 90 % 80 % 70 % 60 % 50 % 40 % 30 % 20 % 10 % 0 % Oil rate [Sm³/d] Figure 10: Obtaining 90%-ile estimate based on 75 days transient data - graphical presentation Revision No.: 1 Revision Date: Page 13/18

14 4.4 Data set and frequencies Table 4 lists data basis for the evaluations and histograms in Section 4. Table 4: Data groups and frequency transient P90 evaluation Rate range [1000 Sm 3 /d] 45 days Frequency [-] 60 days Frequency [-] 75 days Frequency [-] More Total Revision No.: 1 Revision Date: Page 14/18

15 5 REFERENCES 1. OLF Retningslinjer for beregning av utblåsningsrater og - varighet til bruk ved analyse av miljørisiko - Nilsen, Thomas, Rev. nr. 02, 15. januar "Blowout and Kill Simulations_Butch_rev 0", Report, Kristin Dyb, , Acona report AFT APPENDICES Appendix A. About Acona Flow Technology AS Revision No.: 1 Revision Date: Page 15/18

16 Appendix A: About Acona Flow Technology AS Acona Flow Technology AS Since 2006 Acona has built a unique expert team within flow modelling and simulations services, named Acona Flow Technology. This group has the capability and the ambition to contribute to increased operational safety, minimization of risks and increased profitability for its clients. Acona Flow Technology has the mission to: Deliver best-in-class services within blowout modelling and well control Provide simulation services based on state-of-the-art tools and models Offer in-depth understanding and analytical approach to complex flow phenomena Serve various industries worldwide, and transfer know-how across industries Attract world-class specialists and enthusiastic talents through outstanding reputation Acona Flow Technology provides simulations and advisory services to the oil and gas industry within the following areas: Blowout contingency planning Risk management and contingency documentation through advanced simulations and operational insight. Simulation services, advisory services, risk management and peer review services. Wellkill planning and well control advisory Transient kill simulations as mandatory documentation of kill capability and to assist well engineering teams. Emergency response teams Trained and IWCF certified teams available to assist planning, preparation and execution of wellkill operations worldwide. Flow assurance teams Skilled seniors with long industrial training available for detailed flow assurance studies related to well and flowline hydraulics, thermal performance, production chemistry or metallurgy. Complete design-basis engineering studies can be delivered. Computational Fluid Dynamics Advanced CFD experts are available for in-depth analysis of process related flow phenomena and their interaction with structure. Wind, gas, explosion, spill, separation, settling, erosion, insulation, combustion and radiation are some of many areas to be covered with CFD. Revision No.: 1 Revision Date: Page 16/18

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