Petrophysical Interpretation Report — 15-135-24,938-00-00

Well (UWI)	15-135-24,938-00-00
Log date	Sat Oct 24 20-24-33 2009
Service company	Log Tech
Acquisition date (header)	Sat Oct 24 20-24-33 2009
PLSS location	Sec 13 T19 S R22 W (map precision ±1.6 km)
Larionov variant	old_rocks (degraded)
Convergence status	DID_NOT_CONVERGE
Confidence tier	○ BRACKETED
Engine versions	calc_vsh 0.1.0 · calc_phie 0.1.0 · calc_sw 0.1.0 · formula_registry 0.1.0
Config hash (SHA-256)	2a9cb78728e386ab…
Git SHA	bd23bea18153
Generated	autonomously, no human in the per-report loop

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Confidence legend. Each result is tagged by parameter provenance: ● FIRM (core-calibrated) · ◐ QUALIFIED (offset-derived) · ○ BRACKETED (regional/global default — read as a range, dominant uncertainty stated). The system does not claim *always correct*; it states how well-supported each number is.

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⚠️ claim verifier FLAGS: 1 number(s) not traceable to the ledger

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1. Executive summary

⚠️ ABSTENTION — this is NOT a confident estimate. The run did not converge to a defensible result; the numbers below are an uncalibrated engineering estimate, reported for transparency only:
- 1 unresolved MECHANICAL objection(s)

The evaluation is restricted to the consolidated section between 1000.0 m and 1321.0 m — the interval above it is not evaluated (unconsolidated, washed-out response). Within that interval the net pay is 25.5 m with average effective porosity 0.159 and average water saturation 0.329. Monte-Carlo places the P50 net pay at 10.9 m within a P10-P90 range of 2.9 to 27.0 m. An independent SP-derived water resistivity of 0.0445 ohm-m (static SP -58.4 mV; offset-median mud-filtrate resistivity 0.110 ohm-m — a declared cross-well assumption) supports the regional default, and the Monte-Carlo Rw range is narrowed to the field SP band with recorded provenance. The Rxo/Rt movable-hydrocarbon index reads a median of 0.554 over 2071 samples — an invasion-based indicator profile, not a saturation. The run ABSTAINS from a confident estimate: the validators keep an unresolved objection, so the result must be read as a bracketed range, not a point value.

Net pay P10 / P50 / P90 = 2.9 / 10.9 / 27.0 m.
Net pay is dominated by 'm', which is a regional DEFAULT (uncalibrated). This is the single largest uncertainty — the result is bracketed, not a confident point estimate.

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2. Data inventory (from LAS)

• Curves present (canonical ← raw): DCAL←DCAL, DRHO←RHOC, GR←GR, NPHI←CNLS, PHID_SVC←DPOR, RHOB←RHOB, RMED←RILM, RT←RILD, RXO←RLL3, SP←SP
• Logged interval: 59.44–1321.46 m
• Log date: Sat Oct 24 20-24-33 2009
• Service company: Log Tech · Company: American Warrior, Inc.
• Field: Schaben North
• Not provided by LAS (out of scope): core, mud logs, pressure tests, production, completion, formation tops.

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3. LAS quality control

Edit type	Curve	Detail
unit_conversion	NPHI	factor 0.01
hard_range_mask	RXO	count 1
hard_range_mask	RT	count 174
hard_range_mask	RMED	count 16
hard_range_mask	RHOB	count 1
hard_range_mask	DRHO	count 1
hard_range_mask	PHID_SVC	count 3
range_warn	GR	count 2
range_warn	RHOB	count 1
range_warn	NPHI	count 24
spike_removal	—	138 edits
degradation	—	2 edits

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4. Standardization

Raw mnemonics mapped to canonical curve names:

Canonical	Raw mnemonic
DCAL	DCAL
DRHO	RHOC
GR	GR
NPHI	CNLS
PHID_SVC	DPOR
RHOB	RHOB
RMED	RILM
RT	RILD
RXO	RLL3
SP	SP

Unit conversions: NPHI×0.01.

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5. Per-curve log QC

• GR baseline: gr_p5=33.9, gr_p95=116.0
• Bad-hole: GOOD=0.505, DEGRADED=0.456, EXCLUDED=0.039
• Low-resistivity: rt_threshold=1.43, n_flagged=798, intervals=[[265.5, 267.2], [276.1, 291.7], [292.3, 293.1], [294.7, 295.0], [296.3, 300.2], [301.1, 309.5], [310.4, 331.2], [337.3, 338.8], [341.5, 342.4], [352.2, 353.6]]

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6. Data preparation

Edits applied before compute (by type): degradation: 2, hard_range_mask: 6, range_warn: 3, spike_removal: 138, unit_conversion: 1.

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7. Interval definition

• Logged interval: 59.44–1321.46 m
• Analysis window (analyst-restricted): 1000.0–1321.0 m — gross and NTG are measured over this window
• Gross evaluated interval: 321.0 m
• Computed net-pay runs (pre-merge): 26
• Zonation is computed by depth (no formation tops in LAS).

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8. Methodology

All numbers are produced by the deterministic, golden-tested engine. The LLM only selects methods/parameters and writes prose — it never computes a number. Figures are deterministic renderings of these computed numbers for the human reader; the agent reasons over the numeric EDA digest, not images (the models have no vision).

Step	Method (frozen)	Version
Vsh	2-mineral volumetric solve (matrix+clay+porosity from RHOB+NPHI)	vsh_multimineral 0.1.0
PHIE	Density-neutron crossplot, shale-corrected	phie_density_neutron 0.1.0
Sw	Archie 1942	sw_archie 0.1.0
Net pay	Vsh/PHIE/Sw cutoffs → net sand → net reservoir → net pay	netpay 0.1.0
Uncertainty	Monte Carlo P10/P50/P90 + parameter sensitivity	mc 0.1.0

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9. Gamma-ray analysis

• Clean baseline gr_min = 20.0 API · shale gr_max = 120.0 API
• Shale index IGR = (GR − gr_min)/(gr_max − gr_min), the basis for Vsh.
• GR baseline check: gr_p5=33.9, gr_p95=116.0

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10. Resistivity analysis

Low-resistivity scan: rt_threshold=1.43, n_flagged=798, intervals=[[265.5, 267.2], [276.1, 291.7], [292.3, 293.1], [294.7, 295.0], [296.3, 300.2], [301.1, 309.5], [310.4, 331.2], [337.3, 338.8], [341.5, 342.4], [352.2, 353.6]].

Invasion profile (multi-depth resistivities, 7969 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.682; reversed (< 0.8): 0.058; median Rxo/RT 1.402; median Rmed/RT 1.006. Raw-curve facts; naming moveable hydrocarbon is the analyst's judgement.

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11. Density-neutron crossplot lithology

Matrix point-shares (fraction of points near each matrix line): sandstone: 0.107, limestone: 0.256, dolomite: 0.075. Engine crossplot output; naming the dominant lithology is the analyst's judgement. Comparison with core/mud log: not available (LAS-only).

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12. Water resistivity (Rw)

• Rw = 0.0400 ohm-m · provenance: default
• Sourced by the engine (Pickett / SP / default); never authored by the LLM.
• Net-pay sensitivity to Rw: 18.0 m swing.
• Formation-temperature correction (Arps, regional-default gradient): Rw ≈ 0.0096 ohm-m at 46.9 °C (evidence only — Sw uses the calibrated Rw).

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13. Figures

Composite log

Pickett plot

Neutron-density crossplot

Buckles plot

Hingle plot

Distributions

Sensitivity tornado

Net-pay Monte-Carlo distribution

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14. Shale volume (Vsh)

Mean Vsh by method (selection is the agent's; the LLM authors no number):

Method	Mean Vsh	Selected
vsh_larionov_old	0.348
vsh_larionov_tertiary	0.279
vsh_linear	0.460
vsh_clavier	0.334
vsh_steiber	0.300
vsh_neutron_density	0.147
vsh_multimineral	0.153	✓

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15. Porosity

Mean porosity by method (effective where shale-corrected; the LLM authors no number):

Method	Mean porosity	Selected
phie_density_neutron	0.070	✓
phi_density	0.087
phi_neutron	0.119

Service-company porosity curves (cross-check evidence, full-column means): phid_svc: 0.343. Matrix assumptions differ per curve; agreement/disagreement is the analyst's reading.

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16. Water saturation

Mean Sw (Archie 1942) = 0.808 (a=1.00, m=2.00, n=2.00, Rw=0.0180 ohm-m). Electrical parameters are engine-sourced; alternative Sw models are optional sections.

Mean Sw by method (engine-computed comparison; the LLM authors no number):

Method	Mean Sw	Selected
sw_archie	0.808	✓
sw_simandoux	0.687
sw_indonesia	0.715

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17. Zonation (net-pay intervals)

Raw net-pay runs merged into 22 intervals (gap tolerance 1.5 m); showing the 15 thickest, depth-ordered. Full set traces in the ledger.

Interval	Top (m)	Base (m)	Net pay (m)	Avg PHIE	Avg Sw	Avg Vsh
Z1	1010.9	1011.3	0.6	0.318	0.266	0.000
Z2	1063.9	1064.4	0.6	0.159	0.418	0.110
Z3	1099.4	1100.6	1.4	0.216	0.401	0.101
Z4	1119.5	1120.1	0.8	0.189	0.315	0.073
Z5	1165.1	1167.2	2.3	0.145	0.335	0.040
Z6	1202.4	1203.2	0.9	0.144	0.310	0.026
Z7	1218.3	1218.7	0.6	0.146	0.335	0.141
Z8	1227.6	1229.3	1.1	0.143	0.342	0.052
Z9	1236.4	1237.2	0.9	0.155	0.380	0.159
Z10	1241.6	1243.3	1.8	0.145	0.370	0.213
Z11	1258.2	1259.9	1.8	0.143	0.376	0.212
Z12	1281.8	1282.9	1.2	0.222	0.205	0.185
Z13	1288.7	1294.6	4.9	0.156	0.316	0.071
Z14	1309.9	1311.9	2.0	0.107	0.284	0.004
Z15	1314.6	1317.5	2.3	0.143	0.247	0.117

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18. Results

Quantity	Value
Gross interval	321.0 m
Net pay (P10/P50/P90)	2.9 / 10.9 / 27.0 m
Net-to-gross	0.079
Avg PHIE (net pay)	0.159
Avg Sw (net pay)	0.329
Avg Vsh (net pay)	0.098

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19. Uncertainty and sensitivity

Monte Carlo, 500 realizations (seed 42). Net pay swing per parameter (one-at-a-time):

Parameter	Net-pay swing (m)
m	19.2
Rw	18.0
a	4.7
n	1.7

Dominant uncertainty: m (swing 19.2 m).

Multi-seed robustness: P50 UNSTABLE across seeds (spread 2.1 m across 4 seeds).

Net pay is dominated by 'm', which is a regional DEFAULT (uncalibrated). This is the single largest uncertainty — the result is bracketed, not a confident point estimate.

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20. Derived parameters

• Bulk-volume water (BVW = PHIE*Sw): mean 0.0478 v/v
• Porosity-thickness (Phi·H over net pay): 4.056 m
• Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 2.762 m
• Buckles constant (BVW at P10 of net pay): 0.0334 → Swirr (mean) ≈ 0.209 over 167 pay samples

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21. Permeability (uncalibrated)

• perm_timur: mean k = 20.85 mD

_Uncalibrated screening estimate (no core); Sw used as the Swirr proxy._

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22. Rock quality (uncalibrated)

• rqi: mean = 0.102

_Built on the uncalibrated permeability; indicative only._

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23. Electrofacies

Unsupervised k-means on 1774 samples into 4 electrofacies (sample counts: facies 0: 270, facies 1: 466, facies 2: 319, facies 3: 719). Descriptive only — no core labels.

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24. Parameters and provenance

Parameter	Value	Unit	Provenance	Source
gr_min	20.000	API	default	—
gr_max	120.000	API	default	—
rho_ma	2.710	g/cc	default	Schlumberger 1989
rho_fl	1.000	g/cc	default	—
phie_max	0.450	v/v	default	—
phi_sh_d	0.100	v/v	default	—
phi_sh_n	0.350	v/v	default	—
a	1.000	-	default	Winsauer et al. 1952
m	2.000	-	default	Archie, G.E. 1942
n	2.000	-	default	Archie, G.E. 1942
Rw	0.040	ohm-m	default	Kansas Geological Survey 2000
rt_hydrocarbon_floor	5.000	ohm-m	default	—
vsh_cutoff	0.350	v/v	default	—
phie_cutoff	0.100	v/v	default	—
sw_cutoff	0.500	v/v	default	—
bit_size_config	7.875	in	default	—
qc_abort_threshold	0.800	-	default	—
circuit_breaker_n	3.000	-	default	—

The citations table (not RAG) gives each cited parameter exactly one frozen source. Parameters tagged default are regional/global — they drive the bracketed tier.

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25. Petrophysical cutoffs

Boundary-inclusive criteria applied by the engine (netpay) to flag reservoir:

Stage	Criterion	Cutoff	Provenance
Net sand	Vsh ≤ cutoff	0.350	default
Net reservoir	+ PHIE ≥ cutoff	0.100	default
Net pay	+ Sw ≤ cutoff	0.500	default

Cutoff values are engine parameters (never LLM-authored); the dominant net-pay uncertainty is m — see Uncertainty for the swing.

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26. Data quality and validator objections

Curve provenance (canonical ← raw mnemonic): DCAL←DCAL, DRHO←RHOC, GR←GR, NPHI←CNLS, PHID_SVC←DPOR, RHOB←RHOB, RMED←RILM, RT←RILD, RXO←RLL3, SP←SP.

QC edits applied before compute — degradation: 2, hard_range_mask: 6, range_warn: 3, spike_removal: 138, unit_conversion: 1.

Validator	Type	Detail
vsh_phie_anticorrelation	support	Vsh-PHIE Pearson 1.00 > 0.3 (dirty rock + high porosity)
rt_sw_consistency	mechanical	16 depths with Sw<0.4 but RT<5.0 ohm-m

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27. Methodology (decision graph)

flowchart TD
    dec_1["decision: step: set_zone_of_interest"]
    act_1["tool_call: set_zone_of_interest"]
    dec_2["decision: step: compare_methods"]
    act_2["tool_call: compare_methods"]
    dec_3["decision: step: compute_vsh"]
    act_3["tool_call: compute_vsh"]
    dec_4["decision: step: compute_phie"]
    act_4["tool_call: compute_phie"]
    dec_5["decision: step: compare_methods"]
    act_5["tool_call: compare_methods"]
    dec_6["decision: step: compute_sw"]
    act_6["tool_call: compute_sw"]
    dec_7["decision: step: apply_cutoffs"]
    act_7["tool_call: apply_cutoffs"]
    dec_8["decision: step: run_uncertainty"]
    act_8["tool_call: run_uncertainty"]
    dec_9["decision: step: derived_parameters"]
    act_9["tool_call: derived_parameters"]
    dec_10["decision: step: permeability"]
    act_10["tool_call: permeability"]
    dec_11["decision: step: rock_quality"]
    act_11["tool_call: rock_quality"]
    dec_12["decision: step: electrofacies"]
    act_12["tool_call: electrofacies"]
    dec_13["decision: step: lithology"]
    act_13["tool_call: lithology"]

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28. Data gaps for calibration

This is a LAS-only study. Data that would calibrate the interpretation is absent:

• Core (routine + SCAL): would anchor PHIE and Archie m, n, a.
• Pressure tests (RFT/MDT): would give true fluid contacts and gradients (log-based).
• Production/flow data: would test the net-pay flag against deliverability.
• Dominant net-pay uncertainty driver (from the sensitivity): m (calibrated by core SCAL — cementation exponent m).
• Standard curves absent: DT, PEF, CALI.

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29. Limitations

• LAS-only study: no core calibration, no pressure tests (no true fluid contacts), no production, no mud logs, no formation tops (zonation computed by depth).
• Standard curves absent in this well: DT, PEF, CALI.
• Results are uncalibrated; accuracy depends on data not provided.

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30. Conclusions

900 m bin 2.16 (washed); sustained from 1000 m (2.44). N-D clay ~0.07 -> Archie. Method choices were made against the engine's numeric comparisons, not by preference; the comparison tables show the rejected alternatives beside the selected method. All numbers in this report come from the deterministic engine; the analyst chose the interval, the methods and the analyses, and wrote this prose — nothing more. Remaining uncertainty is dominated by the uncalibrated regional parameters.

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Appendix A — Ledger excerpt (traceability)

{
  "net_pay_total_m": 25.450800000000015,
  "net_pay_p10_p50_p90": [
    2.8956000000000017,
    10.896600000000007,
    26.974800000000016
  ],
  "driving_params": {
    "a": 1.0,
    "m": 2.0,
    "n": 2.0,
    "Rw": 0.04
  },
  "claim_verifier": {
    "result": "FLAGS",
    "flags": [
      2.16
    ],
    "tone_flags": []
  }
}

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Appendix B — Completeness gate

Item	Present
QC edits recorded before compute	✓
Every number ledger-traced	✓
Confidence tier on the run	✓
Parameter citations frozen	✓
Validator objections listed, not hidden	✓
Uncertainty propagated (Monte Carlo)	✓
Claim verifier run on prose	✓