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Petrophysical Interpretation Report — 15-135-25545-00-00


Well (UWI)	15-135-25545-00-00
Log date	Mon Mar 18 01-30-42 2013
Acquisition date (header)	Mon Mar 18 01-30-42 2013
PLSS location	Sec 12 T20S R22W (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)

The evaluation is restricted to the consolidated section between 1000.0 m and 1370.0 m — the interval above it is not evaluated (unconsolidated, washed-out response). Within that interval the net pay is 48.8 m with average effective porosity 0.223 and average water saturation 0.289. Monte-Carlo places the P50 net pay at 31.6 m within a P10-P90 range of 9.3 to 56.1 m. An independent SP-derived water resistivity of 0.0402 ohm-m (static SP -76.2 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 0.598 over 2414 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 = 9.3 / 31.6 / 56.1 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, NPHI_DOL←CNDL, NPHI_SS←CNSS, PHID_SVC←DPOR, RHOB←RHOB, RMED←RILM, RT←RILD, RXO←RLL3, SP←SP
Logged interval: 57.91–1370.23 m
Log date: Mon Mar 18 01-30-42 2013
Service company: — · Company: Trans Pacific Oil Corporation
Field: Schaben Pool
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 153
hard_range_mask	RMED	count 10
hard_range_mask	RHOB	count 2
hard_range_mask	DRHO	count 3
hard_range_mask	PHID_SVC	count 7
hard_range_mask	NPHI	count 3
hard_range_mask	NPHI_SS	count 3
hard_range_mask	NPHI_DOL	count 3
range_warn	GR	count 4
range_warn	RHOB	count 3
spike_removal	—	105 edits
degradation	—	2 edits

4. Standardization

Raw mnemonics mapped to canonical curve names:

Canonical	Raw mnemonic
DCAL	DCAL
DRHO	RHOC
GR	GR
NPHI	CNLS
NPHI_DOL	CNDL
NPHI_SS	CNSS
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=24.9, gr_p95=113.5
Bad-hole: GOOD=0.559, DEGRADED=0.407, EXCLUDED=0.034
Low-resistivity: rt_threshold=1.73, n_flagged=837, intervals=[[67.5, 67.8], [280.6, 281.8], [283.8, 286.5], [289.4, 304.0], [304.5, 321.9], [322.5, 344.4], [351.1, 352.2], [367.4, 368.7], [405.7, 407.2], [409.0, 409.3]]

6. Data preparation

Edits applied before compute (by type): degradation: 2, hard_range_mask: 9, range_warn: 2, spike_removal: 105, unit_conversion: 1.

7. Interval definition

Logged interval: 57.91–1370.23 m
Analysis window (analyst-restricted): 1000.0–1370.0 m — gross and NTG are measured over this window
Gross evaluated interval: 370.0 m
Computed net-pay runs (pre-merge): 38
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=24.9, gr_p95=113.5

10. Resistivity analysis

Low-resistivity scan: rt_threshold=1.73, n_flagged=837, intervals=[[67.5, 67.8], [280.6, 281.8], [283.8, 286.5], [289.4, 304.0], [304.5, 321.9], [322.5, 344.4], [351.1, 352.2], [367.4, 368.7], [405.7, 407.2], [409.0, 409.3]].

Invasion profile (multi-depth resistivities, 8360 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.529; reversed (< 0.8): 0.122; median Rxo/RT 1.234; median Rmed/RT 0.909. 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: 0.039, limestone: 0.163, dolomite: 0.051. 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: 22.7 m swing.
Formation-temperature correction (Arps, regional-default gradient): Rw ≈ 0.0128 ohm-m at 47.6 °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	0.279
vsh_larionov_tertiary	0.213
vsh_linear	0.385
vsh_clavier	0.265
vsh_steiber	0.233
vsh_neutron_density	0.166
vsh_multimineral	0.167	✓

15. Porosity

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

Method	Mean porosity	Selected
phie_density_neutron	0.085	✓
phi_density	0.105
phi_neutron	0.135

Service-company porosity curves (cross-check evidence, full-column means): phid_svc: 0.422, nphi_dol: 0.166, nphi_ss: 0.265. Matrix assumptions differ per curve; agreement/disagreement is the analyst's reading.

16. Water saturation

Mean Sw (Archie 1942) = 0.774 (a=1.00, m=2.00, n=2.00, Rw=0.0242 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	0.774	✓
sw_simandoux	0.623
sw_indonesia	0.681

17. Zonation (net-pay intervals)

Raw net-pay runs merged into 26 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	1000.0	1008.0	6.2	0.333	0.209	0.000
Z2	1015.4	1016.1	0.8	0.324	0.226	0.000
Z3	1038.8	1042.3	3.7	0.424	0.192	0.000
Z4	1168.9	1170.1	1.4	0.172	0.378	0.075
Z5	1195.0	1195.7	0.9	0.176	0.338	0.034
Z6	1233.5	1235.5	2.1	0.132	0.228	0.178
Z7	1249.7	1250.4	0.9	0.145	0.306	0.152
Z8	1268.4	1269.2	0.9	0.198	0.371	0.311
Z9	1274.8	1276.0	1.4	0.160	0.387	0.319
Z10	1284.9	1285.5	0.8	0.163	0.337	0.223
Z11	1316.4	1317.3	1.1	0.229	0.214	0.318
Z12	1320.4	1321.2	0.9	0.175	0.271	0.017
Z13	1325.3	1330.6	3.8	0.249	0.227	0.026
Z14	1332.7	1342.8	8.2	0.239	0.170	0.080
Z15	1346.0	1360.9	11.9	0.149	0.407	0.126

18. Results

Quantity	Value
Gross interval	370.0 m
Net pay (P10/P50/P90)	9.3 / 31.6 / 56.1 m
Net-to-gross	0.132
Avg PHIE (net pay)	0.223
Avg Sw (net pay)	0.289
Avg Vsh (net pay)	0.101

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	24.5
Rw	22.7
n	9.0
a	7.0

Dominant uncertainty: m (swing 24.5 m).

Multi-seed robustness: P50 stable (spread 1.2 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 0.0527 v/v
Porosity-thickness (Phi·H over net pay): 10.866 m
Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 8.124 m
Buckles constant (BVW at P10 of net pay): 0.0333 → Swirr (mean) ≈ 0.150 over 320 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, NPHI_DOL←CNDL, NPHI_SS←CNSS, PHID_SVC←DPOR, RHOB←RHOB, RMED←RILM, RT←RILD, RXO←RLL3, SP←SP.

QC edits applied before compute — degradation: 2, hard_range_mask: 9, range_warn: 2, spike_removal: 105, unit_conversion: 1.

Validator	Type	Detail
vsh_phie_anticorrelation	support	Vsh-PHIE Pearson 0.96 > 0.3 (dirty rock + high porosity)
rt_sw_consistency	mechanical	65 depths with Sw<0.4 but RT<5.0 ohm-m

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

From 1000 m (2.51). N-D clay ~0.11 -> 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": 48.76800000000003,
  "net_pay_p10_p50_p90": [
    9.296400000000006,
    31.62300000000002,
    56.09844000000004
  ],
  "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	✓