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Petrophysical Interpretation Report — 15-135-24,937-00-00


Well (UWI)	15-135-24,937-00-00
Log date	Tue Aug 04 17-12-41 2009
Service company	Log Tech
Acquisition date (header)	Tue Aug 04 17-12-41 2009
PLSS location	Sec 23 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

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.

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)
- net-pay avg PHIE 0.28 > 0.25 — implausibly high for carbonate

The evaluation is restricted to the consolidated section between 900.0 m and 1335.0 m — the interval above it is not evaluated (unconsolidated, washed-out response). Within that interval the net pay is 84.7 m with average effective porosity 0.284 and average water saturation 0.285. Monte-Carlo places the P50 net pay at 46.6 m within a P10-P90 range of 13.0 to 87.2 m. An independent SP-derived water resistivity of 0.0435 ohm-m (static SP -62.0 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 0.641 over 2818 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 = 13.0 / 46.6 / 87.2 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.

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: 59.44–1335.18 m
Log date: Tue Aug 04 17-12-41 2009
Service company: Log Tech · Company: American Warrior, Inc.
Field: Schaben
Not provided by LAS (out of scope): core, mud logs, pressure tests, production, completion, formation tops.

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 150
hard_range_mask	RMED	count 56
hard_range_mask	RHOB	count 1
range_warn	GR	count 2
range_warn	NPHI	count 27
spike_removal	—	83 edits
degradation	—	2 edits

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.

5. Per-curve log QC

GR baseline: gr_p5=34.4, gr_p95=116.0
Bad-hole: GOOD=0.717, DEGRADED=0.255, EXCLUDED=0.028
Low-resistivity: rt_threshold=1.35, n_flagged=816, intervals=[[281.9, 284.1], [292.9, 294.4], [296.1, 307.1], [308.6, 316.5], [317.4, 345.9], [352.5, 353.7], [367.0, 367.9], [371.7, 373.2], [420.6, 421.1], [423.7, 425.3]]

6. Data preparation

Edits applied before compute (by type): degradation: 2, hard_range_mask: 4, range_warn: 2, spike_removal: 83, unit_conversion: 1.

7. Interval definition

Logged interval: 59.44–1335.18 m
Analysis window (analyst-restricted): 900.0–1335.0 m — gross and NTG are measured over this window
Gross evaluated interval: 435.0 m
Computed net-pay runs (pre-merge): 45
Zonation is computed by depth (no formation tops in LAS).

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`

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=34.4, gr_p95=116.0

10. Resistivity analysis

Low-resistivity scan: rt_threshold=1.35, n_flagged=816, intervals=[[281.9, 284.1], [292.9, 294.4], [296.1, 307.1], [308.6, 316.5], [317.4, 345.9], [352.5, 353.7], [367.0, 367.9], [371.7, 373.2], [420.6, 421.1], [423.7, 425.3]].

Invasion profile (multi-depth resistivities, 8134 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.655; reversed (< 0.8): 0.074; median Rxo/RT 1.392; median Rmed/RT 0.989. Raw-curve facts; naming moveable hydrocarbon is the analyst's judgement.

11. Density-neutron crossplot lithology

Matrix point-shares (fraction of points near each matrix line): sandstone: 0.167, limestone: 0.264, dolomite: 0.165. Engine crossplot output; naming the dominant lithology is the analyst's judgement. Comparison with core/mud log: not available (LAS-only).

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: 36.1 m swing.
Formation-temperature correction (Arps, regional-default gradient): Rw ≈ 0.0149 ohm-m at 45.7 °C (evidence only — Sw uses the calibrated Rw).

13. Figures

Composite log

Composite log

Pickett plot

Pickett plot

Neutron-density crossplot

Neutron-density crossplot

Buckles plot

Buckles plot

Hingle plot

Hingle plot

Distributions

Distributions

Sensitivity tornado

Sensitivity tornado

Net-pay Monte-Carlo distribution

Net-pay Monte-Carlo distribution

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	0.364
vsh_larionov_tertiary	0.291
vsh_linear	0.479
vsh_clavier	0.349
vsh_steiber	0.313
vsh_neutron_density	0.126
vsh_multimineral	0.127	✓

15. Porosity

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

Method	Mean porosity	Selected
phie_density_neutron	0.130	✓
phi_density	0.160
phi_neutron	0.142

Service-company porosity curves (cross-check evidence, full-column means): phid_svc: 0.305. Matrix assumptions differ per curve; agreement/disagreement is the analyst's reading.

16. Water saturation

Mean Sw (Archie 1942) = 0.729 (a=1.00, m=2.00, n=2.00, Rw=0.0275 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	0.729	✓
sw_simandoux	0.659
sw_indonesia	0.663

17. Zonation (net-pay intervals)

Raw net-pay runs merged into 36 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	924.8	927.7	3.0	0.379	0.353	0.008
Z2	934.5	937.7	2.6	0.308	0.369	0.063
Z3	969.4	973.1	3.5	0.294	0.376	0.167
Z4	980.7	1019.6	39.0	0.342	0.226	0.000
Z5	1032.5	1038.5	6.1	0.328	0.207	0.000
Z6	1065.9	1068.2	2.4	0.275	0.326	0.000
Z7	1204.0	1205.6	1.8	0.187	0.386	0.106
Z8	1213.0	1214.2	1.4	0.148	0.250	0.103
Z9	1247.7	1249.2	1.2	0.216	0.410	0.281
Z10	1254.1	1259.6	4.1	0.206	0.339	0.134
Z11	1263.9	1265.4	1.7	0.227	0.299	0.087
Z12	1294.2	1295.2	1.2	0.238	0.258	0.231
Z13	1315.8	1318.7	2.6	0.146	0.287	0.128
Z14	1326.2	1327.3	1.2	0.118	0.396	0.256
Z15	1329.8	1331.7	2.0	0.147	0.284	0.161

18. Results

Quantity	Value
Gross interval	435.0 m
Net pay (P10/P50/P90)	13.0 / 46.6 / 87.2 m
Net-to-gross	0.195
Avg PHIE (net pay)	0.284
Avg Sw (net pay)	0.285
Avg Vsh (net pay)	0.050

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	36.7
Rw	36.1
a	18.0
n	7.9

Dominant uncertainty: m (swing 36.7 m).

Multi-seed robustness: P50 stable (spread 3.5 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.

20. Derived parameters

Bulk-volume water (BVW = PHIE*Sw): mean 0.0645 v/v
Porosity-thickness (Phi·H over net pay): 24.083 m
Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 17.627 m
Buckles constant (BVW at P10 of net pay): 0.0475 → Swirr (mean) ≈ 0.167 over 556 pay samples

21. 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.

22. 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.

23. 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: 4, range_warn: 2, spike_removal: 83, unit_conversion: 1.

Validator	Type	Detail
vsh_phie_anticorrelation	support	Vsh-PHIE Pearson 0.95 > 0.3 (dirty rock + high porosity)
rt_sw_consistency	mechanical	236 depths with Sw<0.4 but RT<5.0 ohm-m
net_pay_plausibility	irreducible	net-pay avg PHIE 0.28 > 0.25 — implausibly high for carbonate

24. 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: lithology"]
    act_10["tool_call: lithology"]

25. 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.

26. 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.

27. Conclusions

RHOB 2.40-2.41 at 900-1000 is porous reservoir facies, not overburden — included. N-D clay ~0.12 -> 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.

Appendix A — Ledger excerpt (traceability)

{
  "net_pay_total_m": 84.73440000000005,
  "net_pay_p10_p50_p90": [
    12.954000000000008,
    46.63440000000003,
    87.20328000000006
  ],
  "driving_params": {
    "a": 1.0,
    "m": 2.0,
    "n": 2.0,
    "Rw": 0.04
  },
  "claim_verifier": {
    "result": "PASS",
    "flags": [],
    "tone_flags": []
  }
}

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	✓