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Home My WebLink About2023 Prudhoe Oil and Put River Oil Pools3800 Centerpoint Drive, Suite 1400, Anchorage, AK 99503 Phone:907/777-8300 hilcorp.com Hilcorp North Slope, LLC March 30, 2024 Brett Huber, Sr.,Chair Alaska Oil and Gas Conservation Commission 333 West 7th Avenue, Suite 100 Anchorage, AK 99501 RE:Prudhoe Bay Unit, Prudhoe and Put River Oil Pools Annual Reservoir Surveillance Report for Water and Miscible Gas Floods Annual Reservoir Properties Reports January 1, 2023 –December 31, 2023 Chairman Huber, Hilcorp North Slope, LLC, as operator of the Prudhoe Bay Unit, submits the enclosed Annual Reservoir Surveillance Reports for the Prudhoe Bay Waterflood Project, Miscible Gas Project, Gas Cap Water Injection Project, Field Gravity Drainage Area and Put River Oil Pool in accordance with Conservation Orders 341C (originally CO 279), 341D, 341F.007, 341I, and 559A. In addition, Hilcorp North Slope will simultaneously file the Annual Reservoir Properties Reports (ARPs, form 10-428)for the Prudhoe and Put River Oil Pools under this cover and to aogcc.reporting@alaska.gov. The Operators of the Prudhoe Bay Field reserve the right to alter the content of the analyses contained in this report at any time based upon the most recent surveillance information obtained.If you have any questions regarding the reports, please contact Abbie.Barker@hilcorp.com. Thank you, Keith Elliott Asset Team Leader, Prudhoe Bay East Hilcorp North Slope, LLC Cc:Stephanie Erickson, ConocoPhillips Alaska, Inc. Greg Keith, ConocoPhillips Alaska, Inc. Becky Steen, ConocoPhillips Alaska, Inc. Todd Griffith, ExxonMobil Alaska, Production Inc. Jeff Farr, ExxonMobil Alaska, Production Inc. Gary Selisker, Chevron USA Dave Roby, AOGCC Allan Eddy,DNR, Division of Oil & Gas Kenneth Diemer, DNR, Division of Oil & Gas Heather Beat, DNR, Division of Oil & Gas 1 I ANNUAL RESERVOIR SURVEILLANCE REPORT WATER AND MISCIBLE GAS FLOODS PRUDHOE OIL POOL AND PUT RIVER OIL POOL & ANNUAL RESERVOIR PROPERTIES REPORT PRUDHOE AND PUT RIVER OIL POOLS JANUARY THROUGH DECEMBER 2023 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 2 CONTENTS SECTION PAGE 1.0 INTRODUCTION 4 2.0 OVERVIEW 4 3.0 PRESSURE UPDATE 5 4.0 MISCIBLE INJECTANT (MI)6 5.0 PROJECT SUMMARIES 6 5.1 SWOP and PAVE 6 5.2 Gas Cap Water Injection Project 7 5.2.1 Observation Well RST Surveys and Zonal Conformance 8 5.2.2 2024 Surveillance Plans 9 5.2.3 Plans for Change in Project Operation 9 5.3 Put River Pool 9 5.4 N2 Foam Treatment Program 11 6.0 REVIEW OF POOL PRODUCTION ALLOCATION FACTORS 12 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 3 LIST OF EXHIBITS 1-A Prudhoe Bay Unit Field Schematic 2 Fieldwide Reservoir Balance 3-A PBU Pressure Map 3-B Areally Weighted Average Pressure Plot 3-C Areally Weighted Pressure Data 3-D Pressure Survey (Form 10-412) 4 Average Monthly CGF MI Rates and Compositions 5 GCWI Surveillance and Extent 2023 6 Annual Reservoir Properties Report-Prudhoe and Put River Oil Pools (AK 20 AAC 25.270) 7 Put River Sandstone Distribution 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 4 1.0 INTRODUCTION As required by Conservation Order (CO) 341I and CO 559A, this report provides a consolidated report of the surveillance activities and EOR project updates for the Prudhoe Oil Pool, plus a section for the Put River Pool. The time period covered is January through December of 2023. Information included is as follows: •Production and Injection Volumes and Voidage balance by month •Analysis of reservoir pressure surveys and trends •Data on Minimum Miscibility Pressure (MMP) of injected miscible gas •Progress of the enhanced recovery projects, including the gas cap water injection project The Annual Reservoir Properties Report-Prudhoe and Put River Oil Pools is being submitted under cover of this report as Exhibit 6. (AK 20 AAC 25.270). The Excel version is also being submitted electronically to aogcc.reporting@alaska.gov. A report of completed development or service wells that have been shut-in for 365 days or longer as of January 1, 2023, will be separately filed with the Commission by March 31, 2023, in accordance with 20 AAC 25.115. 2.0 OVERVIEW IPA Prudhoe Bay (Permo-Triassic) Reservoir development began in 1968 with the Prudhoe Bay State No. 1 exploratory well. Regular production began in June 1977. Produced water injection began in June 1977, and large-scale water flood for secondary recovery was installed in August 1984. In June 1987, the Prudhoe Bay Miscible Gas Project (PBMGP) was established. In 2002, Gas Cap Water Injection (GCWI) began, with the goal of stabilizing reservoir pressure. Most recently, implementation of the Seawater Optimization Plan (SWOP) in 2020 at Flow Station 1 ceased water injection in a portion of the Prudhoe Bay Waterflood Project. During the report period of January through December 2023, Prudhoe Oil Pool production averaged 146.9 MBOD, 7559 MMSCFD (GOR 51,465 SCF/STB), and 1257 MBWD (water-cut 89.54%). Overall injection during this period averaged 1,919 MBWD with 125 MMSCFD of miscible gas injection. 831 Wells contributed to production and 215 wells contributed to injection. PA Average Daily Oil Production (BOPD) Average Daily Water Production (MBWPD) Average Daily Gas Production (MMSCFPD) Oil Production (MBBL) Water Production (MBBL) Gas Production (BSCF) IPA 146,885 1,257 7,559 53,613 458,756 2,759 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 5 PA Total Gas Injection (BCF) Dry Gas Injection (BCF) MI Injection (BCF) Average Daily Water Injection (MBWPD) Average Daily Sea Water Injection (MBWPD) Average Daily Gas Cap Water Injection (MBWPD) IPA 2,545 2,499 46 1920 717.3 697.7 PA Total Active Well Count Active Producer Well Count Active Injector Well Count IPA 1046 831 215 See Exhibit 2 for POP voidage by month. Note – Exhibit 2 does not include aquifer influx as we cannot directly measure this. However, the full field model and water sample data suggest there has been some amount of aquifer influx over time. 3.0 PRESSURE UPDATE Exhibit 3-D (Form 10-412) provides pressure, buildup, and falloff data collected in 2023 at a datum of 8,800 ft, subsea used for the Ivishak Formation. During 2023, per CO 341I, as modified by the Commission on July 20, 2016, use of calculated BHP’s from surface data in injectors are permitted. All of these new data are listed in Exhibit 3-D as “FL”. However, the fluid level calculated pressures have been excluded from the pressure calculation and map, as it has been observed that the fluid level pressures are more subject to error. Previous years have been corrected with this change in the pressure calculation. Exhibit 3-A provides spatial analysis of pressure static, buildup, and falloff data that was collected from 2021 through 2023 at a datum of 8,800 ft, subsea for the Ivishak Formation. This map shows an elevated pressure in the gas cap area as a function of GCWI. As shown in Exhibit 3-B, the historic pressure decline appears to have stabilized due to gas-cap water injection. With increased gas cap water injection volumes and the commencement of PAVE in the end of 2023, we expect to see an increase in average reservoir pressure in 2024. For 2023, average pressure in the PBMGP project areas using three years of pressure static measurements was calculated to be 3324 psia by areal weighting, as compared to 3312 psia in 2022. The GD area pressure increased 28 psi from 3271 psia in 2022 to 3299 psia in 2023 (Exhibit 3-B). Observed increases in pressure appear to be related to statistical variability and sampling locations. Field voidage replacement ratio was 1.01 in 2023 (not including any potential aquifer influx). 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 6 4.0 MISCIBLE INJECTANT (MI) AOGCC Conservation Order No. 341I, Rule 12 (c) specifies that “The minimum miscibility pressure (MMP) of the Miscible Injectant must be maintained at least 100 psi below the average reservoir pressure in the Prudhoe Bay Miscible Project area. When the Operator demonstrates that the reservoir pressure is no longer declining within the Prudhoe Bay Miscible Project Area (as evidenced by reservoir pressure measurements), the MMP may be maintained at or below the average reservoir pressure in the Prudhoe Bay Miscible Project area.” As MMP became the constraint on NGL production in the winter of 2018, and the reservoir pressure has stabilized with the gas cap water injection project, the MMP limit was increased from 3150 psi to 3200 psi in March of 2019 and further increased to 3300 psi early 2022. Although the PBMGP average pressure is still slightly above MMP overall, we will discuss the benefits of decreasing MMP to 3250 psi, as the average pressure in the MIST and UZI areas appear to be closer to 3250 psi. No degradation in MI utilization has been observed in either of these areas in 2023. There are two MI analyzers at Prudhoe Bay CGF (4901 and 4951). Analyzer 4951 is installed at the suction side of the MI compressors and analyzer 4901 is installed at the discharge side of the compressors downstream of the lean gas back blend. Analyzer 4901 was out of calibration from June to September 2020. However, it was repaired in October 2020 and has been functioning normally since then. The compositional data reported in Exhibit 4 are the monthly average values of analyzer 4901 data. The compositions from the analyzers are used to calculate real time MMP at CGF. The MMP data reported in Exhibit 4 are the monthly averages based on the daily average MMP calculated at the discharge side of the MI compressors. Engineering judgement is applied to remove some poor data with extremely high or low values. 5.0 PROJECT SUMMARIES 5.1 SWOP and PAVE On March 5, 2020, the Commission approved the Seawater Optimization Project (SWOP) which was implemented in the 2020 plan year in DS-1 and DS-12 of the Eastern Peripheral Wedge Zone (EPWZ) of the waterflood at these pads.The Commission specified the following two conditions: Condition 1 states that BPXA is required to include in the Annual Reservoir Surveillance report for the POP and PROP: “a detailed description of the progress towards returning the PROP to production”. Condition 2 states that the ASR is to also include “the evaluation of the potential to improve ultimate recovery by ceasing water injection elsewhere in the POP”. The SWOP project was implemented August 2020; a description of the Put River Oil Pool plan is included in section 6.3 of this report. A preferred PAVE implementation plan was selected in 2022 and implementation began in 2023. 2023 and 2024 activity to date includes the up-hole recompletion of 6 FS2 area Zone 1 water injectors to Zones 2, 3 and 4 and the completion of PAVE1-1 water injector. Collectively, these wells are injecting approximately 150mbwpd of 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 7 produced water and we are evaluating options to increase injectivity to further increase injection to approximately 200mbw/d in these wells. 2024 plans include the continued evaluation of new water injection wells at FS3 and GC1 to inject up to 150mbwd into the original and expanded gas gap. 5.2 Gas Cap Water Injection Project Details of the volume of water injected into the Gas Cap during 2023 are shown below; units in thousands of barrels of seawater injected per month (MBWPM): Month Total GCWI Volume (MBWPM) 1/2023 23,318 2/2023 21,905 3/2023 24,552 4/2023 20,608 5/2023 21,253 6/2023 20,762 7/2023 21,617 8/2023 18,621 9/2023 21,965 10/2023 19,236 11/2023 16,716 12/2023 24,105 The 2023 volume of sea water injected in the PSI wells was 255 million barrels. The cumulative volume injected at the end of 2023 was 3.8 billion barrels of sea water since the project startup in 2002. 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 8 5.2.1 GCWI Surveillance Pulsed neutron logs (RPM, RMT, etc.) run in offset producers continue to be the primary method of monitoring water movement from the Gas Cap Water Injection project. Many of these wells have had several repeat logs since injection began. By comparing the latest neutron logs with the baseline and previous logs, the presence of injected water can be readily observed. This procedure has provided a very clear picture of water in the Ivishak Formation and allows the monitoring of vertical and lateral movement of the waterfront. Exhibit 5 is the locator map for the GCWI area and shows the PSI injectors along with the observation wells. The pink polygon indicates the interpreted current GCWI waterfront, which has very minimal change since 2018. The most recent acquired neutron surveillance logs include: 05-30, 15-07D, L1-13, and L5-21. Surveillance wells for 2023 saturation monitoring were chosen at the northeastern, southern, and western boundaries of the waterfront to provide sufficient coverage to monitor GCW extent, as well as better refine understanding of the water movement into the producing zones 1A and 1B. Based on surveillance log results, no discernible GCW is observed in 15-07D and L1-13. The results from L5-21 are inconclusive but may suggest that water is present in Z1A – Z1B. For the interim, we show the extent of the GCW to be directly south of L5-21, but this will need to be reevaluated in the future. Many wells in the DS18 area are producing GCW. Understanding the water pathway to Zone 1, the oil-bearing interval in this far up-structure area of the field, is a continued focus for future 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 9 logging and analysis. This continued focus will require integrating production and cased-hole log evidence to define water migration. Future surveillance will continue to include repeat neutron logs for monitoring the maximum lateral extent of the flood front and monitoring water movement within each zone, specifically in the producing Zone 1. No DS18 wells started producing GCW for the first time in 2023. 5.2.2 2024 Surveillance Plans GCWI Injectors Injection pressures, rates, and temperatures are recorded for each well every day. Pressure-rate plots will be routinely monitored for changes in injectivity of the wells. Observation Well Cased Hole Saturation Logs This program will continue as it has in the past by running cased hole saturation logs every year with the final timing and locations determined based on the results to date. Gravity Survey The most recent gravity survey was conducted in 2022 and the next gravity survey is planned for 2028. 5.2.3 Plans for Change in Project Operation None 5.3 Put River Oil Pool On November 22, 2005, the AOGCC ruled in Conservation Order 559 that the Western, Central and Southern Lobes of hydrocarbon bearing Put River sands would be defined as the Put River Pool and that the Northern Lobe would be included in the Prudhoe Oil Pool. Exhibit 7 displays all four lobes which are in pressure isolation from each other. Additional technical information was previously supplied with the application which led to Conservation Order 559. On December 19, 2019, the AOGCC granted BPXA’s request to: (1) to administratively amend Conservation Order 559A to contract the Put River Oil Pool (PROP) to the area encompassed by the Southern Lobe of the Put River sandstone; (2) to modify rule 18 of CO341H to ensure that the downhole commingling ruled authorization that currently allows downhole commingling of any well in the PROP with the Prudhoe Oil Pool will continue to apply to wells completed within the currently established bounds of the PROP when the affected area of the PROP is contracted; and (3) a gas oil ratio exemption to wells completed in the Central and Western lobes of the Put River sandstone for the purposes of collecting data to develop a reservoir development strategy for those sands in accordance with 20 AAC 25.240(b)(3). 2023 Production and Injection For the year 2023, no production came from the Put River Oil Pool. The 02-27A reported production volumes in late 2023, however, this is allocation problem that is currently being resolved. On 10/28/23 a patch was placed over the Put River formation and from this time forward 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 10 all production is coming from the Prudhoe Bay Oil pool. Any production prior to this date is for the year 2023 is also incorrect as the well was shut in. There was no injection in the Southern Lobe of the Put River in 2023. Cumulative Put River water injection is 14.1 MMBW. All Put River Southern Lobe injection has been from well 01-08A. 01- 08A was shut-in in August 2020 and remains shut-in due to the execution of the SWOP project. As a result of the injector shut-in, the Put River Southern Lobe producer 02-27A was also shut-in. The 2023 cumulative production for the Put River Oil Pool was 15 MBO, 0.7 MBW and approximately 523 MMSCF formation gas. The full life cumulative production for the Put River Oil Pool through December 31, 2023, was 4.3 MMBO, 9.2 MMBW, and approximately 9.9 BSCF formation gas. (Note that these cumulative volumes include a technical estimate, based on material balance calculations, of Southern lobe production from a casing leak in 02-27 between 1994-1997. The cumulative gas volume reported in this report is reflective of the best technical estimate of the formation gas production from the PROP; the volume reported in previous ASRs may differ due to accounting for the estimated casing leak volumes and gas lift volumes.) Average Daily Oil Production (BOPD) Average Daily Water Production (MBWPD) Average Daily Gas Production (MMSCFPD) Oil Production (MBBL) Water Production (MBBL) Gas Production (BSCF) 0 0 0 0 0 0 Cumulative Oil Production (MMBO) Cumulative Water Production (MMBW) Cumulative Gas Production (BSCF) 4.3 9.2 9.9 Since the commencement of SWOP and the shut-in of all injection at Flow Station 1, options have been evaluated to restore the PROP to production, including drilling, workover, and non-rig wellwork options to allow for resumed injection into the PROP. We will continue to consider the feasibility of alternative sources of injection water to satisfy voidage replacement requirements needed to resume production from the PROP. In the meantime, while we evaluate our options, we will continue to monitor the reservoir by obtaining a static bottom hole pressure or fluid level in one of our three Put River Southern Lobe wells in 2024 to observe the pressure behavior during the shut-in period. For this report, the reservoir properties in Exhibit 6 for the PROP pertain to the Southern lobe only. 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 11 2023 Pressures The PROP Southern Lobe pressure obtained in injector 01-08A on 7/7/2022 measured 3,653 PSI at -8,100’ SSTVD. 2024 Surveillance Plan PROP affected area (Southern Lobe) –A static bottom hole pressure or fluid level survey is planned in 2024 for producer 02-23A or injector 01-08A to observe the pressure behavior in the Put River Southern Lobe. 5.4 N2 Foam Treatment Program In 2022 and 2023 a campaign began to pump water and foam into Gravity Drainage producers and flowback in an attempt to block gas production and reduce producing GORs. Water injection occurred before foam injection. Multiple injection volumes and periods of well testing during flowback proved that GOR suppression was possible and helped inform the optimal injection volume for GOR suppression, on a well-by-well basis. Water injection for GOR suppression has been executed into 8 gravity drainage wells and observed predictable GOR suppression results, which last for a period of about one week. Follow up foam injection has occurred on three wells to date: C-10B, C-22A, and E-24B. Learnings to date demonstrate that foam treatments can be economic if 4 months of lower GOR are achieved creating competitive production as observed in C-10B. E-24B (zone 1A) was the poorest-performing foam treatment so far – lower permeability GD wells appear to be less 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 12 favorable for foam. C-10B and C-22A are both higher permeability and similar production rate Zone 1B/2A wells, but the foam results were quite different. C-22A GOR suppression lasted only about one month. Looking for high-grading clues, however, it looks like the water response from C-22A was also less favorable than that of C-10B. So perhaps water response can be predictive of foam performance. Going forward, more water treatments are planned to help high- grade future foam candidates. A repeat foam treatment on C-10B is being evaluated to optimize foam treatment design in future candidates. 6.0 Review of Pool Production Allocation Factors Prudhoe Oil Pool (POP) and Put River Oil Pools Monthly Average Oil Allocation Factors: 2023 Oil Allocation Factor Jan 0.944 Feb 0.950 Mar 0.949 Apr 0.954 May 0.959 Jun 0.943 Jul 0.949 Aug 0.935 Sep 0.939 Oct 0.942 Nov 0.939 Dec 0.942 The table contains monthly averages of oil allocation factors from the 7 facilities that receive production from these two pools: GC-1 (POP only), GC-2 (POP only), GC-3 (POP only), FS-1 (POP & PUT), FS-2 (POP only), FS-3 (POP only) LPC (POP only). Any days of allocation factors of zero were excluded. Daily allocation data and daily test data are being retained. 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 13 Exhibit 1-A Prudhoe Bay Unit Map 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 14 Exhibit 2 Fieldwide Reservoir Balance Mo n t h Oi l , M R B Wa t e r , MR B Fr e e G a s , MR B To t a l Vo i d a g e , MR B Ye a r C u m , MR B Cu m S i n c e S t a r t - Up , M R B Wa t e r In j e c t i o n , MR B Mi s c i b l e Ga s In j e c t i o n , MR B Le a n G a s In j e c t i o n , MR B To t a l In j e c t i o n , MR B Ye a r C u m , MR B Cu m S i n c e St a r t - U p , MR B Ne t In j e c t i o n , MR B Ye a r Cu m , MR B Cu m S i n c e St a r t - U p , M R B Ja n - 2 3 6, 4 6 2 41 , 9 1 8 21 7 , 5 4 6 26 5 , 9 2 6 26 5 , 9 2 6 10 4 , 5 0 5 , 6 6 8 64 , 8 5 0 3, 3 1 2 20 1 , 2 3 6 26 9 , 3 9 8 26 9 , 3 9 8 92 , 8 8 7 , 5 0 2 3, 4 7 2 3, 4 7 2 (1 1 , 6 1 8 , 1 6 6 ) Fe b - 2 3 5, 8 4 4 38 , 1 9 9 19 7 , 7 1 2 24 1 , 7 5 5 50 7 , 6 8 0 10 4 , 7 4 7 , 4 2 3 59 , 5 1 4 2, 9 3 4 18 2 , 2 8 0 24 4 , 7 2 9 51 4 , 1 2 6 93 , 1 3 2 , 2 3 1 2, 9 7 4 6, 4 4 6 (1 1 , 6 1 5 , 1 9 2 ) Ma r - 2 3 6, 3 3 8 42 , 6 2 9 21 1 , 9 4 2 26 0 , 9 0 9 76 8 , 5 8 9 10 5 , 0 0 8 , 3 3 2 66 , 9 8 9 3, 1 9 0 19 5 , 8 7 8 26 6 , 0 5 7 78 0 , 1 8 3 93 , 3 9 8 , 2 8 8 5, 1 4 8 11 , 5 9 4 (1 1 , 6 1 0 , 0 4 4 ) Ap r - 2 3 5, 9 3 7 40 , 0 5 4 20 0 , 3 5 9 24 6 , 3 5 0 1, 0 1 4 , 9 3 9 10 5 , 2 5 4 , 6 8 2 61 , 0 9 6 2, 7 0 9 18 5 , 5 9 7 24 9 , 4 0 3 1, 0 2 9 , 5 8 6 93 , 6 4 7 , 6 9 1 3, 0 5 3 14 , 6 4 6 (1 1 , 6 0 6 , 9 9 1 ) Ma y - 2 3 6, 0 5 4 43 , 5 6 4 19 7 , 9 6 0 24 7 , 5 7 8 1, 2 6 2 , 5 1 8 10 5 , 5 0 2 , 2 6 0 64 , 3 0 5 2, 9 1 8 18 3 , 2 3 1 25 0 , 4 5 4 1, 2 8 0 , 0 4 0 93 , 8 9 8 , 1 4 5 2, 8 7 6 17 , 5 2 2 (1 1 , 6 0 4 , 1 1 6 ) Ju n - 2 3 5, 6 8 9 39 , 0 5 3 18 2 , 6 3 7 22 7 , 3 7 8 1, 4 8 9 , 8 9 6 10 5 , 7 2 9 , 6 3 8 61 , 0 6 3 2, 5 1 7 16 8 , 8 9 7 23 2 , 4 7 7 1, 5 1 2 , 5 1 7 94 , 1 3 0 , 6 2 2 5, 0 9 9 22 , 6 2 1 (1 1 , 5 9 9 , 0 1 7 ) Ju l - 2 3 5, 1 5 7 30 , 0 5 3 17 0 , 6 5 2 20 5 , 8 6 1 1, 6 9 5 , 7 5 7 10 5 , 9 3 5 , 4 9 9 50 , 6 5 8 1, 7 2 6 15 8 , 5 8 2 21 0 , 9 6 6 1, 7 2 3 , 4 8 3 94 , 3 4 1 , 5 8 8 5, 1 0 5 27 , 7 2 6 (1 1 , 5 9 3 , 9 1 2 ) Au g - 2 3 4, 9 7 3 34 , 7 4 8 15 5 , 9 5 5 19 5 , 6 7 6 1, 8 9 1 , 4 3 3 10 6 , 1 3 1 , 1 7 5 51 , 4 6 0 1, 4 1 9 14 4 , 6 1 3 19 7 , 4 9 3 1, 9 2 0 , 9 7 6 94 , 5 3 9 , 0 8 1 1, 8 1 7 29 , 5 4 3 (1 1 , 5 9 2 , 0 9 5 ) Se p - 2 3 5, 3 3 8 36 , 4 5 8 17 1 , 0 2 7 21 2 , 8 2 3 2, 1 0 4 , 2 5 6 10 6 , 3 4 3 , 9 9 8 59 , 4 3 3 2, 6 0 3 15 7 , 0 6 6 21 9 , 1 0 1 2, 1 4 0 , 0 7 6 94 , 7 5 8 , 1 8 1 6, 2 7 8 35 , 8 2 1 (1 1 , 5 8 5 , 8 1 7 ) Oc t - 2 3 6, 0 2 0 41 , 1 6 4 19 9 , 3 8 0 24 6 , 5 6 5 2, 3 5 0 , 8 2 1 10 6 , 5 9 0 , 5 6 3 59 , 2 7 9 2, 8 9 4 18 3 , 1 4 3 24 5 , 3 1 7 2, 3 8 5 , 3 9 3 95 , 0 0 3 , 4 9 8 (1 , 2 4 8 ) 34 , 5 7 3 (1 1 , 5 8 7 , 0 6 5 ) No v - 2 3 5, 9 1 9 41 , 9 0 6 19 9 , 1 0 6 24 6 , 9 3 2 2, 5 9 7 , 7 5 2 10 6 , 8 3 7 , 4 9 5 57 , 5 5 4 2, 5 0 1 18 4 , 5 8 1 24 4 , 6 3 6 2, 6 3 0 , 0 2 9 95 , 2 4 8 , 1 3 4 (2 , 2 9 6 ) 32 , 2 7 7 (1 1 , 5 8 9 , 3 6 1 ) De c - 2 3 6, 2 9 6 45 , 0 6 8 22 0 , 3 0 3 27 1 , 6 6 7 2, 8 6 9 , 4 1 9 10 7 , 1 0 9 , 1 6 2 68 , 8 2 4 3, 2 0 9 20 3 , 9 1 2 27 5 , 9 4 5 2, 9 0 5 , 9 7 4 95 , 5 2 4 , 0 7 9 4, 2 7 8 36 , 5 5 4 (1 1 , 5 8 5 , 0 8 3 ) 20 2 3 T o t a l s 70 , 0 2 8 47 4 , 8 1 3 2, 3 2 4 , 5 7 9 2, 8 6 9 , 4 1 9 72 5 , 0 2 6 31 , 9 3 2 2, 1 4 9 , 0 1 7 2, 9 0 5 , 9 7 4 36 , 5 5 4 (1 3 9 , 1 8 6 , 8 5 8 ) 20 2 3 V R R 1. 0 1 Cu m . V R R 0. 8 9 Pr o d u c e d F l u i d s In j e c t e d F l u i d s Ne t I n j e c t i o n ( I n j e c t i o n - P r o d u c t i o n ) 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 15 Exhibit 3-A Pressure Map 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 16 Exhibit 3-B Areally Weighted Average Pressure Plot Exhibit 3-C Areally Weighted Pressure Data Exhibit 3-C Areally Weighted Average Pressures DATE FS2 EPWZ WPWZ NWFB GD EWE PBMGP Dec-77 3935 4005 4016 3944 3999 3968 Jul-78 3870 3967 3978 3909 3963 3914 Dec-78 3832 3930 3944 3875 3933 3873 Jul-79 3813 3895 3911 3843 3901 3844 Dec-79 3791 3861 3879 3799 3871 3816 Jul-80 3799 3831 3848 3770 3856 3798 Dec-80 3852 3819 3822 3781 3823 3818 Jul-81 3881 3821 3799 3814 3809 3840 Dec-81 3880 3815 3799 3820 3793 3842 Jul-82 3872 3806 3800 3812 3778 3833 Dec-82 3850 3795 3797 3804 3762 3818 Jul-83 3831 3784 3792 3787 3745 3804 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 17 Jan-84 3814 3771 3783 3772 3728 3790 Jul-84 3796 3758 3777 3756 3711 3774 Jan-89 3779 3743 3771 3736 3695 3755 Jul-89 3760 3730 3763 3723 3678 3740 Jan-90 3732 3708 3731 3704 3658 3713 Jul-90 3708 3693 3716 3687 3641 3695 Jan-91 3680 3676 3694 3655 3623 3666 Jul-91 3642 3657 3673 3628 3605 3635 Jan-92 3617 3641 3652 3602 3588 3615 Jul-92 3591 3626 3632 3577 3570 3593 Jan-93 3561 3600 3619 3544 3549 3582 Jul-93 3543 3595 3598 3515 3531 3565 Jan-94 3539 3555 3578 3483 3512 3537 Jul-94 3523 3536 3555 3456 3492 3516 Jan-95 3496 3524 3555 3507 3482 3506 Jul-95 3473 3507 3536 3489 3466 3486 Jan-96 3466 3485 3497 3478 3446 3463 Jul-96 3450 3467 3472 3461 3430 3443 Jan-97 3446 3484 3460 3444 3404 3441 Jul-97 3429 3467 3438 3427 3387 3421 Jan-98 3452 3417 3417 3421 3379 3430 Jul-98 3435 3409 3394 3402 3363 3415 Jan-99 3445 3391 3382 3343 3339 3443 Jul-99 3429 3378 3360 3317 3323 3426 Jan-00 3406 3361 3372 3268 3294 3418 Jul-00 3390 3351 3353 3240 3273 3395 Jan-01 3366 3325 3325 3225 3274 3358 Jul-01 3360 3310 3309 3205 3257 3347 Jan-02 3325 3334 3289 3163 3270 3358 Jul-02 3312 3324 3273 3144 3245 3347 Jan-03 3299 3316 3262 3121 3236 3696 3297 Jul-03 3285 3306 3245 3118 3223 3659 3283 Jan-04 3271 3296 3228 3116 3211 3645 3272 Jul-04 3277 3324 3281 3296 3239 3614 3290 Jul-05 3338 3344 3282 3289 3250 3542 3314 Jul-06 3304 3296 3276 3296 3233 3536 3293 Jul-07 3357 3339 3275 3248 3243 3618 3310 Jul-08 3317 3299 3298 3269 3244 3626 3299 Jul-09 3348 3310 3308 3271 3248 3663 3315 Jul-10 3367 3329 3317 3329 3259 3666 3339 Jul-11 3368 3345 3308 3322 3265 3640 3338 Jul-12 3375 3338 3350 3302 3283 3632 3348 Jul-13 3391 3335 3313 3329 3276 3663 3348 Jul-14 3402 3324 3314 3322 3270 3652 3348 Jul-15 3398 3330 3313 3335 3275 3645 3350 Jul-16 3409 3332 3303 3332 3277 3650 3343 Jul-17 3396 3306 3310 3327 3287 3611 3343 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 18 Jul-18 3375 3330 3313 3363 3281 3600 3347 Jul-19 3370 3342 3296 3441 3292 3693 3358 Jul-20 3370 3342 3296 3441 3292 3693 3358 Jul-21 3316 3316 3326 3378 3275 3690 3331 Jul-22 3340 3290 3270 3342 3271 3587 3312 Jul-23 3361 3257 3277 3385 3229 3640 3324 It was agreed with the commission that the polygon pressures would be calculated differently starting with the 2005 report, than it had in past reports due to the advent of pressure response to gas-cap water injection. That methodology consisted of utilizing only the pressure gathered during the reporting period. Starting with the 2009 report, since the field pressure has stabilized, pressure points from a rolling three-year period were used to construct the pressure map so as to reduce the statistical variation induced by changing year-to-year well sets. Exhibit 3-A illustrates the 2022 pressure map using 2020 through 2022 data points. Fluid level data points have been removed from the analysis this year, as they appeared to introduce too much error. Using the three-year rolling technique improves the statistical validity of the pressure distribution since it roughly triples the number of data points employed versus only using the current year static pressures. As in the past, abnormal pressures, such as pressures taken in fault compartments and in the Sag River Formation have been removed. For this report, as in the past, pressures taken in fault compartments, the Sag River Formation, and in Zone 1 of the G-Pad LPA (Low Pressure Area), which don’t appear to be in good communication with the rest of the reservoir, have been excluded from Exhibit 3-A. Also excluded were wells shut-in less than a week that had not stabilized as compared to offsetting statics. Other wells completed in Zone 1 and Zone 4B, which are in poor communication with the rest of the reservoir and therefore have lower pressures, were still included in the map and calculations if their shut-in times were deemed long enough. Unless otherwise noted, all pressure calculations are areally weighted, bound by the main field original 50' LOC contour, and are referenced to a pressure datum of 8,800' SS. 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 19 Exhibit 3-D Pressure Surveys (Form 10-412) 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 20 Exhibit 4 MI Composition EO A MI R a t e MM P MW Av e r a g e M o n t h l y M o l e % MC F D PS I Mo l W t CO 2 C1 + N 2 C2 C3 IC 4 NC 4 C5 + 1/ 1 / 2 0 2 3 10 0 , 3 0 7 3, 2 4 3 32 . 0 8 21 . 3 0 % 32 . 8 3 % 20 . 6 3 % 24 . 4 7 % 0. 5 8 % 0. 1 9 % 0. 0 0 % 2/ 1 / 2 0 2 3 10 7 , 0 0 9 3, 3 1 3 32 . 2 1 21 . 3 4 % 32 . 3 2 % 20 . 6 6 % 25 . 0 0 % 0. 5 2 % 0. 1 5 % 0. 0 0 % 3/ 1 / 2 0 2 3 11 1 , 5 4 1 3, 3 0 4 32 . 1 3 20 . 9 6 % 32 . 8 1 % 20 . 3 7 % 25 . 0 2 % 0. 6 5 % 0. 1 9 % 0. 0 0 % 4/ 1 / 2 0 2 3 10 3 , 9 6 7 3, 1 5 8 32 . 0 6 20 . 7 8 % 33 . 1 2 % 20 . 1 8 % 25 . 1 6 % 0. 6 2 % 0. 1 4 % 0. 0 1 % 5/ 1 / 2 0 2 3 10 7 , 5 7 4 3, 2 7 5 32 . 1 1 20 . 6 5 % 33 . 4 4 % 19 . 8 6 % 24 . 6 6 % 0. 9 1 % 0. 4 9 % 0. 0 0 % 6/ 1 / 2 0 2 3 10 5 , 2 1 2 3, 2 7 0 32 . 1 9 20 . 5 7 % 33 . 5 3 % 19 . 6 4 % 24 . 2 8 % 1. 1 2 % 0. 8 5 % 0. 0 1 % 7/ 1 / 2 0 2 3 70 , 0 9 4 3, 2 9 1 32 . 2 6 19 . 6 8 % 33 . 7 0 % 19 . 3 8 % 24 . 7 5 % 1. 2 8 % 1. 2 0 % 0. 0 1 % 8/ 1 / 2 0 2 3 54 , 2 0 4 3, 2 2 9 32 . 3 2 19 . 7 9 % 33 . 3 4 % 19 . 3 1 % 25 . 3 9 % 1. 2 6 % 0. 8 9 % 0. 0 1 % 9/ 1 / 2 0 2 3 99 , 3 4 3 3, 3 2 9 32 . 0 3 20 . 9 2 % 33 . 8 6 % 19 . 8 1 % 23 . 7 4 % 1. 0 1 % 0. 6 5 % 0. 0 1 % 10 / 1 / 2 0 2 3 11 0 , 1 8 9 3, 3 2 9 32 . 2 1 21 . 5 5 % 32 . 7 7 % 20 . 3 7 % 24 . 0 1 % 0. 8 6 % 0. 4 4 % 0. 0 0 % 11 / 1 / 2 0 2 3 10 7 , 1 7 6 3, 2 1 5 32 . 3 4 21 . 5 5 % 32 . 0 9 % 20 . 6 3 % 24 . 6 0 % 0. 7 6 % 0. 3 7 % 0. 0 0 % 12 / 1 / 2 0 2 3 13 0 , 2 6 9 3, 3 0 1 32 . 1 5 21 . 4 9 % 32 . 5 6 % 20 . 6 5 % 24 . 5 7 % 0. 5 9 % 0. 1 3 % 0. 0 0 % WO A MI R a t e MM P MW Av e r a g e M o n t h l y M o l e % MC F D PS I Mo l W t CO 2 C1 + N 2 C2 C3 IC 4 NC 4 C5 + 1/ 1 / 2 0 2 3 15 7 , 0 2 5 3, 2 3 2 32 . 1 3 21 . 2 6 % 32 . 7 6 % 20 . 5 9 % 24 . 4 2 % 0. 5 7 % 0. 4 0 % 0. 0 0 % 2/ 1 / 2 0 2 3 14 4 , 4 3 6 3, 3 1 4 32 . 1 6 21 . 4 0 % 32 . 4 8 % 20 . 6 3 % 24 . 8 1 % 0. 5 3 % 0. 1 5 % 0. 0 0 % 3/ 1 / 2 0 2 3 15 7 , 4 3 9 3, 2 9 9 32 . 1 0 21 . 0 4 % 32 . 9 1 % 20 . 4 1 % 24 . 8 2 % 0. 6 4 % 0. 1 8 % 0. 0 1 % 4/ 1 / 2 0 2 3 15 9 , 8 1 0 3, 3 2 6 32 . 1 5 20 . 9 2 % 32 . 7 1 % 20 . 3 8 % 25 . 2 2 % 0. 6 3 % 0. 1 4 % 0. 0 1 % 5/ 1 / 2 0 2 3 17 0 , 6 4 1 3, 2 7 5 32 . 1 2 20 . 6 4 % 33 . 4 0 % 19 . 8 6 % 24 . 7 1 % 0. 9 0 % 0. 4 9 % 0. 0 0 % 6/ 1 / 2 0 2 3 15 8 , 5 0 9 3, 2 7 5 32 . 2 3 20 . 5 3 % 33 . 4 5 % 19 . 5 6 % 24 . 4 7 % 1. 1 2 % 0. 8 6 % 0. 0 1 % 7/ 1 / 2 0 2 3 14 3 , 8 7 6 3, 2 1 1 32 . 3 6 19 . 7 1 % 33 . 3 9 % 19 . 3 8 % 24 . 9 4 % 1. 3 2 % 1. 2 5 % 0. 0 1 % 8/ 1 / 2 0 2 3 12 9 , 2 2 4 3, 1 1 3 32 . 5 8 20 . 0 5 % 32 . 1 1 % 19 . 8 5 % 25 . 9 2 % 1. 2 3 % 0. 8 2 % 0. 0 1 % 9/ 1 / 2 0 2 3 15 0 , 9 0 4 3, 3 1 1 32 . 0 9 20 . 9 8 % 33 . 6 4 % 19 . 8 5 % 23 . 8 6 % 1. 0 1 % 0. 6 5 % 0. 0 1 % 10 / 1 / 2 0 2 3 15 6 , 6 8 0 3, 3 0 4 32 . 2 0 21 . 6 1 % 32 . 8 4 % 20 . 2 8 % 24 . 0 0 % 0. 8 3 % 0. 4 4 % 0. 0 0 % 11 / 1 / 2 0 2 3 14 6 , 1 0 7 3, 2 0 2 32 . 3 9 21 . 4 1 % 32 . 0 0 % 20 . 4 6 % 24 . 9 4 % 0. 8 3 % 0. 3 6 % 0. 0 0 % 12 / 1 / 2 0 2 3 15 1 , 0 8 9 3, 2 8 9 32 . 2 1 21 . 6 4 % 32 . 3 6 % 20 . 5 9 % 24 . 7 0 % 0. 5 8 % 0. 1 3 % 0. 0 0 % 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 21 Exhibit 5 GCWI Surveillance and Extent 2023 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 22 Exhibit 6 Annual Reservoir Properties Report-Prudhoe and Put River Oil Pools (AK 20 AAC 25.270) 2023 ANNUAL RESERVOIR SURVEILLANCE REPORT PRUDHOE BAY AND PUT RIVER OIL POOLS 23 Exhibit 7 Put River Sandstone Distribution