Reserves
The Chinarevskoye field (Chinarevskoye) is the only field owned by the Group. Its PSA was grandfathered from 1997 and the licence is valid until the end of 2031.
The Chinarevskoye field (Chinarevskoye) is the only producing field owned by the Group. Its governing PSA dates from 1997 and the licence is valid until the end of 2031. Initial hydrocarbon discoveries at Chinarevskoye were made during the Soviet era. There have been 103 wells and side-tracks drilled under the PSA between 2004 and 2023. The licence is 100% owned by Zhaikmunai, the Group’s principal Kazakhstan operating company.
Chinarevskoye is a multi-layer structure with 17 reservoirs and 53 compartments spread over three areas. Commercial hydrocarbons have been found in the Lower Permian, Bashkirian, Bobrikovski, Tournaisian, Frasnian, Mullinski, Ardatovski, and Biyski-Afoninski reservoirs.
Group management provided an estimate of the Chinarevskoye Proven, Probable and Possible reserves as of 31 December 2023, which was internally prepared under the guidelines set forth in the 2018 Petroleum Resources Management System (SPE- PRMS) and was not subject to an external audit as no material change in the reserves development was made. The internal reserves estimation workflow covered volumes of reserves, production and discounted future net income estimated by management.
Production and future net income were derived from a drilling and well intervention program to extract the estimated Proven, Probable and Possible reserves at a long-term Brent benchmark average oil price of US$75 for 2024 and US$70 from 2025 onwards. However, execution of the program to recover the 2P reserves is dependent on Nostrum successfully further identifying low risk drilling targets, and to this end seismic and geological work is ongoing. There is no guarantee that the Group will be able to achieve this, which could have a material impact on the Group’s ability to develop the remaining Proven and Probable Reserves at Chinarevskoye.
Total 2P (Proven plus Probable) reserves are 23.2 mmboe as of 31 December 2023 after adjusting for reservoir production of 3.7 mmboe in 2023. The net reduction in reserves of 1.4 mmboe in the year is due to poorer-than-expected production from the Biyski- Afoninski North-East and Ardatovski North-East gas reserves but being partially offset by better production associated from other producing horizons and the 2023 workover and rigless intervention campaign. The Proven and Probable reserves volume requires 14 CAPEX interventions, with an additional 11 OPEX well interventions for production maintenance (2022: 28.3 mmboe requiring 17 CAPEX interventions).
Management’s estimates of reserves of 31st December 2023 and a comparison with the reserves of 31st December 2022 are summarised in Table 1.
Table 1 – Nostrum Reserves, mmboe
| 2023 | 2022 | Change | |
|---|---|---|---|
| Total PDP Total PUD/PDNP | 15.1 1.2 | 19.0 1.2 | -3.9 - |
| Total 1P Total Probable | 16.3 6.9 | 20.2 8.1 | -3.9 -1.2 |
| Total 2P Possible | 23.2 8.2 | 28.3 8.5 | -5.1 -0.3 |
| Total 3P | 31.4 | 36.8 | -5.4 |
Note: Barrel of oil equivalent (boe) totals are management estimates using a conversion factor of 5.327 mcf/boe.
The Total 1P (Proven) reserves for Chinarevskoye at December 31st 2023 was 16.3 mmboe or 3.9 mmboe down year-on- year due to 2023 production and poorer than expected performance in the Biyski-Afoninski North-East and Ardatovski North-East gas condensate reservoir which was partially offset by a positive revision in other reservoirs due to well performance and successful workovers and rigless interventions. 1P reserves volumes are comprised of 15.1 mmboe for Proven, Developed Producing (PDP) from 44 current wells and 1.2 mmboe for the Proven, Undeveloped (PUD) category which assumes the deepening of one well, the sidetracking of another and one workover.
The current Probable Undeveloped case assumes 9 rig-assisted interventions including four workover recompletions, side-tracking of four existing wells, and one new vertical well in the Bashkirian reservoir. After a three-year break, which was bridged with a targeted well workover and rigless well intervention program to offset some of the field production decline, the Company started a two-well drillin program in December 2023 to be executed over 2023-2024.
In 2024, Nostrum plans to continue this workover and well intervention programme by targeting a limited number of reserves development wells along with production maintenance, and continue the drilling programme. This programme, together with the 44 existing producers, cover the estimated 2P reserves as at 31 December 2023. It should also be noted that there has been some decrease in volumes in undeveloped reservoirs associated with delays in the re-start of the drilling campaign.
Possible reserves of 8.2 mmboe as at 31 December 2023 (2022: 8.5 mmboe) are attributed to lower declines than the Proven and Probable cases in existing producers and 10 well interventions (3 WO, 5 sidetracks, 2 new wells).
Table 2 shows the breakdown of each reserves category by products.
Table 2 – Nostrum Reserves, by product and by reserves category
| Fluid | Unit | Proven Producing (PDP) | Proven Non-Producing & Undeveloped (PDNP & PUD) | Total Proven (1P) | Probable (2P) | Total Proven plus Probable | Possible (P3) | Total Proven, Probable and Possible |
|---|---|---|---|---|---|---|---|---|
| Oil/Condensate | barrels | 6,754,782 | 909,411 | 7,664,193 | 3,471,879 | 11,136,072 | 4,469,489 | 15,605,561 |
| Plant products (LPG) | barrels | 1,711,341 | 87,922 | 1,799,263 | 647,198 | 2,446,461 | 785,976 | 3,232,437 |
| Gas (after shrink) | mmcf | 35,232 | 1,228 | 36,460 | 14,919 | 51,379 | 15,576 | 66,955 |
| Gas (after shrink) | boe | 6,614,329 | 230,591 | 6,844,920 | 2,800,831 | 9,645,750 | 2,924,159 | 12,569,909 |
| Total | boe | 15,080,452 | 1,227,924 | 16,308,376 | 6,919,907 | 23,228,283 | 8,179,624 | 31,407,907 |
Reserves by reservoir
The breakdown by reservoir is given in Table 3.
Table 3 – Comparison of reserves by reservoir 2022 versus 2021
| 31 December 2023 | 31 December 2022 | Change | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Reservoir | Proven, mmboe | Probable, mmboe | Possible, mmboe | 3P, mmboe | Proven, mmboe | Probable, mmboe | Possible, mmboe | 3P, mmboe | Proven, mmboe | Probable, mmboe | Possible, mmboe | 3P, mmboe |
| Biyski/Afoninski NE | 6.1 | 1.0 | 0.8 | 7.9 | 7.9 | 2.0 | 1.8 | 11.7 | -1.8 | -1.0 | -1.0 | -3.7 |
| Tournaisian NE | 6.1 | 2.4 | 1.3 | 9.8 | 7.3 | 2.5 | 1.4 | 11.2 | -1.2 | -0.1 | -0.1 | -1.4 |
| Frasnian N | 0.4 | 1.1 | 2.5 | 4.0 | 0.6 | 1.0 | 2.6 | 4.2 | -0.2 | 0.1 | -0.1 | -0.2 |
| Ardatovski NE | 1.5 | 1.6 | 0.1 | 3.2 | 2.0 | 1.8 | 0.1 | 4.0 | -0.5 | -0.2 | 0.0 | -0.8 |
| Filippovski | 0.2 | 0.2 | 0.8 | 1.2 | 0.2 | 0.2 | 0.8 | 1.2 | 0.0 | 0.0 | 0.0 | 0.0 |
| Tournaisian South | 0.3 | 0.1 | 0.7 | 1.2 | 0.3 | 0.1 | 0.7 | 1.1 | 0.0 | 0.1 | 0.0 | 0.1 |
| Mullinski NE | 0.6 | 0.0 | 1.1 | 1.8 | 0.6 | 0.0 | 0.4 | 1.0 | 0.0 | 0.0 | 0.7 | 0.7 |
| Bashkirian NE & W | 0.5 | 0.2 | 0.0 | 0.7 | 0.6 | 0.2 | 0.1 | 0.9 | -0.1 | 0.0 | 0.0 | -0.1 |
| Tournaisian West | 0.3 | 0.1 | 0.0 | 0.4 | 0.3 | 0.1 | 0.1 | 0.5 | -0.1 | 0.0 | 0.0 | -0.1 |
| Mullinski South | 0.0 | 0.0 | 0.7 | 0.7 | 0.0 | 0.0 | 0.4 | 0.4 | 0.0 | 0.0 | 0.2 | 0.2 |
| Bobrikovski South | 0.1 | 0.1 | 0.0 | 0.2 | 0.1 | 0.1 | 0.0 | 0.3 | 0.0 | 0.0 | 0.0 | -0.1 |
| Ardatovski S | 0.1 | 0.0 | 0.0 | 0.2 | 0.2 | 0.0 | 0.0 | 0.2 | 0.0 | 0.0 | 0.0 | -0.1 |
| Mullinski North | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Total | 16.3 | 6.9 | 8.2 | 31.4 | 20.2 | 8.1 | 8.5 | 36.8 | -3.9 | -1.2 | -0.3 | -5.4 |
A summary and comparison of the workover and drilling programme by reservoir is given in Table 4.
Table 4 – Summary of the 31 December 2023 well programme supporting the reserves estimates compared to the previous year (excluding rigless interventions)
| 31 December 2023 | 31 December 2022 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Reservoir | Proven wells | Probable wells | Possible wells | Total | Proven wells | Probable wells | Possible wells | Appraisal | Total |
| Biyski/Afoninski NE | — | − | − | − | 1 | − | − | − | 1 |
| Tournaisian NE – oil | 2 | 2 | − | 4 | 2 | 1 | − | − | 3 |
| Tournaisian NE – WI | 1 | 3 | − | 4 | − | 3 | − | − | 3 |
| Tournaisian South | − | − | 1 | 1 | − | − | 1 | − | 1 |
| Tournaisian West | − | − | − | − | − | − | − | − | − |
| Mullinski South | − | − | 1 | 1 | − | − | 1 | − | 1 |
| Mullinski North | − | − | − | − | − | − | − | − | − |
| Mullinski NE | 1 | − | 2 | 3 | 1 | − | 2 | − | 3 |
| Bashkirian NE & W | − | 1 | − | 1 | − | 1 | − | − | 1 |
| Ardatovski NE | − | 1 | − | 1 | − | 1 | − | − | 1 |
| Ardatovski S | − | − | − | − | − | − | − | − | − |
| Frasnian N | − | 1 | 3 | 4 | − | 1 | 3 | − | 4 |
| Filippovski | − | 1 | 4 | 5 | − | 1 | 4 | − | 5 |
| Bobrikovski South | − | 1 | − | 1 | − | − | − | − | − |
| Appraisal | − | − | − | − | − | − | − | — | |
| Total | 16.3 | 6.9 | 8.2 | 31.4 | 4 | 8 | 11 | - | -23 |
Biyski-Afoninski North-East
2P reserves are estimated at 7.15 mmboe, down 2.75 mmboe compared to 2022-year end (9.9 mmboe) which includes 1.4 mmboe of production in 2023 and a 1.35 mmboe negative revision due to observed gas production performance in 2023.
Gas lift was introduced into 4 more wells in 2023 to maintain production with increasing water-gas ratio and a further 2 wells are planned in 2024, predominantly through low cost rigless interventions and using the expanded Gas lift system commissioned in July 2023.
Probable and Possible Developed volumes are attributed to existing producing wells, with lower declines interpreted respectively. No new drilling is planned in this reservoir. The 2019 Schlumberger study concluded that the potential of further infill drilling is limited, which corresponds with management’s opinion.
Tournaisian North-East, West and South
The Tournaisian North-East has a total 2P of 8.5 mmboe at 2023-year end, representing a 1.3 mmboe decline year-on year, including 1.26 mmboe production and a 0.05 mmboe negative revision to reflect recent well performance.
Proven Undeveloped volumes are associated with one deepening and one sidetrack well in 2024-2025 whilst Probable Undeveloped Reserves are associated with one idle well workover in 2024, one sidetrack producer in 2026, one water-flood sidetrack in 2026 and two workover recompletions for the extension of the water-flood in 2025. Production maintenance workovers are planned in the reservoir in the years up to and including 2027.
Tournaisian West 2P is 0.34 mmboe despite 0.11 mmboe production as the well Ch-204 was connected to GL in the second half of 2023 showing stabilised production performance.
In the Tournaisian South, there are limited PDP volumes associated with the three remaining producers and Possible reserves associated with one new well planned for 2026.
Ardatovski North-East and South
Proven Producing volumes are associated with three current producers. One Probable Undeveloped side-track well is planned for the Ardatovski North-East reservoir in 2026. No further reserves development is planned for the Ardatovski South reservoir, beyond the current producer.
Frasnian North
2P reserves are estimated at 1.51 mmboe at year end 2023, despite 0.21 mmboe of production in 2023; the better than expected well performance is reflected in the slight reserves increase by 0.08 mmboe of the existing producer Ch-40_1. Probable Undeveloped reserves being attributed to well Ch- 41_1_1, with a drilling start in Q2 2024 and expected to be online before end of 2024.
The development plan still foresees three additional Possible Undeveloped side- tracks planned for 2025-2026, depending on the success of Ch-41_1_1, which the geological model is expected to confirm.
Mullinski North-East, North and South
Proven Developed Producing reserves remain for three wells, two in the North- East and one in the North respectively. Proven Undeveloped volumes are attributed to one new well in the North-East block and planned for drilling in 2024.
Two Possible Undeveloped category well locations have been identified in the North-East block and are side-tracks of existing wells, while one new Possible well is planned for drilling in the Mullinski South. All three wells are planned for 2025-2026.
Bashkirian North-East & West
PDP reserves remain for two wells produced via Electric Submersible Pumps (ESPs). One Probable Undeveloped new vertical well is proposed in the Bashkirian North-East from 2026.
Filippovski
Five low-cost workover recompletions (one Probable and four Possible) have been identified for the Filippovski reservoir. These are planned, subject to further technical and economic evaluation, to be carried out in 2025-2026.
