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Home My WebLink About2024 Oooguruk-Nuiqsut Oil Pool2024 Annual Reservoir Surveillance Report Oooguruk-Nuiqsut Oil Pool (ONOP) Oooguruk Field April 17, 2025 Hilcorp – WNS Asset Team Table of Contents SUBJECT PAGE 1.0 Progress of the Enhanced Recovery Project ............................................................................1 2.0 Results and Analysis of Reservoir Pressure Surveys within the Pool .........................................3 3.0 Results and Analysis of Production and Injection Log Surveys, Tracer Surveys, Observation Well Surveys and Any Other Special Monitoring ......................................................................................3 4.0 Review of Pool Production Allocation Factors and Issues Over the Year ...................................4 5.0 Reservoir Management Summary .........................................................................................5 ATTACHMENT A ONOP Well Location Map ..................................................................................6 ATTACHMENT B 2024 ONOP Voidage Balance by Month ...............................................................7 ATTACHMENT C ONOP Pressure Report, Form 10-412 ...................................................................8 ATTACHMENT D ONOP Annual Reservoir Properties Report, Form 10-428 .......................................9 Hilcorp – WNS Asset Team Page 1 1.0 Progress of the Enhanced Recovery Project The Oooguruk Field (OF) is located offshore on the North Slope of Alaska. Three oil pools, the Torok, Kuparuk, and Nuiqsut, are currently under development within the OF. The development consists of an offshore man-made gravel island, the Oooguruk Drill Site (ODS), located just east of the Colville River Delta in Harrison Bay. ODS production is delivered to the Oooguruk Tie-in Pad (OTP) via a buried subsea flowline bundle and onshore flowlines, metered, then transferred to Kuparuk River Unit (KRU) facilities, operated by ConocoPhillips Alaska, Inc. (CPAI), for final processing and transportation to the sales line. At the end of 2024, there were 28 active Oooguruk-Nuiqsut Oil Pool (ONOP) development wells, including 18 producer and ten injection wells. The locations of the ONOP, the existing and planned ONOP wells, the current OU, and Oooguruk Nuiqsut Participating Area (ONPA) are shown in Attachment A. Operations included general maintenance and replacing critical oil, water, and gas piping and valves. Field-wide maintenance was also performed, including mechanical integrity inspections of piping, tanks, pressure vessels and other safety systems. As per vendor recommendation, routine maintenance was performed on the three power generation turbines, including the generator cleaning. In addition, cathodic protection inspections were completed on the sub-sea production flowline from ODS to OTP to ensure the mechanical integrity of the pipelines. The river overflood inspections are completed annually to verify the depth of cover over the buried subsea pipelines, including modeling of water flows over the ice, strudel and scour identification and bathymetric surveys. Conversion from the existing Siemens PCS7 Distributed Control System (DCS) to Emerson DeltaV is ongoing and will be completed in 2025. The Oooguruk development originally envisioned producing wells with electrical submersible pumps (ESPs) in order to maximize drawdown and minimize gas lift and the associated KRU and hydraulic back-out effects. Currently, the majority of the OF producing wells require gas lift to produce; only two wells, ODSN-04 and ODSN-25, produce using ESPs. The gas lift gas coupled with the OF formation gas significantly impacts the flowline pressure, reducing overall flowrates, and generates significant back-out cost at KRU, which is also primarily constrained by gas processing capacity. Hilcorp – WNS Asset Team Page 2 Table 1: 2024 ONOP Well Interventions Average annual daily water injection for 2024 was 9,128 bpd. Total water injection in 2024 was 3,332 Mbbl. No gas injection occurred in 2024. Cumulative gas injection in the ONOP is 12,617 MMSCF since the start of the project. The annual voidage replacement ratio averaged 94% for the year. The cumulative voidage replacement ratio is at 58%. Attachment B details the 2024 voidage balance for the ONOP. Hilcorp – WNS Asset Team Page 3 2.0 Results and Analysis of Reservoir Pressure Surveys within the Pool Two pressure surveys were conducted in 2024 as detailed in Attachment C. The recorded pressures are consistent with expectations for the Nuiqsut reservoir. 3.0 Results and Analysis of Production and Injection Log Surveys, Tracer Surveys, Observation Well Surveys and Any Other Special Monitoring Reservoir surveillance is routinely conducted to monitor wells and reservoir performance and to recommend changes in operating conditions, perform rate allocations, propose optimization actions, address, and solve general issues. Historically well surveillance equipment was placed in the liners of seventeen Nuiqsut wells during the initial completions. The systems are in-place to assess production profiles and continuity along the lateral via target fluid tracers, which were monitored and analyzed by collecting surface fluid samples during restarts and over time. The tracers have been used to assess hydraulic connectivity along the laterals to evaluate the need for coil tubing interventions to clear any sand or debris blocking the flow path. For all wells the oil tracer components are no longer active. However, if a significant water breakthrough event occurs sampling to assess the water tracer response is planned. Hilcorp – WNS Asset Team Page 4 4.0 Review of Pool Production Allocation Factors and Issues Over the Year Production from the Oooguruk-Torok Oil Pool (OTOP), Oooguruk-Kuparuk Oil Pool (OKOP) and Oooguruk-Nuiqsut Oil Pool (ONOP) is commingled at the surface into a common production line. Allocation between the pools is based on the ratio of total production for a pool to the total production for the Oooguruk Unit. The pool oil allocation factors for 2024 are: ONOP:96.1% OKOP: 3.9% OTOP: 0% Theoretical production for individual wells for all pools is calculated on a daily basis. Daily theoretical production for a well was calculated using the data from the most current well test and the amount of time a well was on production for a given day: oductionlDailyTheoreticaBOPDxDailyRate dayMinutes Minutes Welltest produced Pr)(1440  The daily allocation factor for the unit is calculated by dividing the actual total production for the day by the sum of the theoretical daily production for each individual well. Daily allocated production is assigned to each well by multiplying its theoretical daily production by the daily allocation factor. The average daily oil allocation factor for 2024 during Hilcorp operation was 0.914. Hilcorp – WNS Asset Team Page 5 5.0 Reservoir Management Summary The AOGCC issued pool rules under Conservation Orders No. 645A, 596 and 597 for the OTOP, OKOP and the ONOP, respectively. While there is no subsurface commingling, unitized substances produced from the three oil pools are commingled on the surface. Area injection orders (AIOs) authorizing the injection of fluids for enhanced oil recovery in the OTOP, OKOP, and ONOP reservoirs were issued by the AOGCC as AIO No. 37A, 33 and 34, respectively. Injection commenced into the ONOP in 2009. During 2024 the ONOP Under-Saturated Water-Alternating-Gas (US-WAG) reservoir management included maximizing voidage replacement, while minimizing known adverse injector to producer flow path connections and managing producing gas oil ratios by cycling producing wells on and off production where possible operationally. The current cumulative voidage replacement ratio is at 58%, which is consistent with ratio of injection wells to producing wells (17 producer and ten injection wells active) and the overall ONOP pattern layout. Attachment B details the 2024 annual and cumulative voidage balance for the ONOP. In general, producing wells in the more mature flood areas have seen GOR stabilization, stabilized or increased oil production, and some water breakthrough as expected, and also via unexpected connections which are being evaluated, monitored and managed. With the consistent water injection and ample supply due to implementation of SWIS, ONOP flood throughput has increased reducing the overall GOR and stabilizing area pressures. Reservoir management for the ONOP will continue to maximize voidage within allowable injection pressure. Hilcorp – WNS Asset Team Page 6 ATTACHMENT A ONOP Well Location Map Hilcorp – WNS Asset Team Page 7 ATTACHMENT B 2024 ONOP Voidage Balance by Month Month Oil, MSTBO Produced Gas, MMSCF Water, MBBL Total Voidage, MRB Year Cum Voidage, MRB Cum Since Start-up, MRB Gas Injection [MMscf] Water Injection, Mstb Total Injection, Mrb Year Cum, Mrb Cum Since Start-up, Mrb Net Injection, MRB Year Cum, MRB Cum Since Start-up, MRB Cum Since Start-Up Thru 2023 >>85,206 Cum Since Start-Up Thru 2023 >>48,431 -36,775 1/31/2024 168 102 48 294 294 85,500 0 277 283 283 48,714 -11 -11 -36,786 2/29/2024 138 75 45 237 532 85,738 0 260 265 548 48,979 28 17 -36,758 3/31/2024 166 90 51 281 813 86,019 0 273 279 827 49,258 -2 14 -36,761 4/30/2024 165 99 46 286 1,099 86,305 0 266 272 1,099 49,530 -14 0 -36,775 5/31/2024 169 97 52 292 1,391 86,597 0 273 278 1,377 49,808 -14 -14 -36,789 6/30/2024 157 88 53 275 1,666 86,872 0 278 283 1,660 50,091 9 -5 -36,780 7/31/2024 167 85 55 280 1,945 87,151 0 291 297 1,958 50,389 18 12 -36,763 8/31/2024 159 85 55 274 2,219 87,425 0 293 299 2,257 50,688 25 37 -36,738 9/30/2024 177 104 49 304 2,523 87,729 0 276 281 2,538 50,969 -23 14 -36,761 10/31/2024 193 123 54 344 2,867 88,073 0 278 284 2,822 51,253 -60 -45 -36,820 11/30/2024 184 150 49 364 3,232 88,438 0 287 293 3,115 51,546 -71 -117 -36,892 12/31/2024 194 127 58 353 3,585 88,791 0 279 284 3,399 51,830 -69 -186 -36,961 2024 Totals 2,036 1,226 616 3,585 0 3,332 3,399 -186 Produced Fluids Injected Fluids Net Injection Hilcorp – WNS Asset Team Page 8 ATTACHMENT C ONOP Pressure Report, Form 10-412 Hilcorp – WNS Asset Team Page 9 ATTACHMENT D ONOP Annual Reservoir Properties Report, Form 10-428