Petrophysical Interpretation Report — 15-135-25402-00-00
| Well (UWI) | 15-135-25402-00-00 |
| Log date | Tue Jul 31 09-25-21 2012 |
| Service company | Log Tech |
| Acquisition date (header) | Tue Jul 31 09-25-21 2012 |
| PLSS location | Sec 19 T19S R21W (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 | df574ffab7ee |
| 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
The pay estimate for well 15-135-25402-00-00 must be read as a bracketed range rather than a firm number, spanning 1.2 m at P10 to 16.9 m at P90 around a P50 of 5.6 m within a 180.0 m gross interval — a net-to-gross of only 0.012 that points to thin, sparse reservoir. Where pay is present the rock looks reasonable, carrying effective porosity of 0.152, water saturation of 0.391, and a modest shale volume of 0.132, but these averages should be treated as indicative given the very limited net thickness. The dominant control on this outcome is the cementation exponent m, which here is a regional DEFAULT with no core calibration and drives a swing of 3.5 m in net pay, making it the single largest source of uncertainty. One validator objection remains unresolved and the interpretation did not fully converge, so the wide P10–P90 spread is the honest expression of the pay potential until m can be locally constrained.
Net pay P10 / P50 / P90 = 1.2 / 5.6 / 16.9 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: 59.44–1339.75 m
- Log date: Tue Jul 31 09-25-21 2012
- 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 186 |
| hard_range_mask | RMED | count 24 |
| hard_range_mask | RHOB | count 1 |
| hard_range_mask | DRHO | count 4 |
| hard_range_mask | PHID_SVC | count 5 |
| range_warn | RHOB | count 4 |
| range_warn | NPHI | count 29 |
| spike_removal | — | 162 edits |
| degradation | — | 3 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=23.4, gr_p95=102.7
- Bad-hole: GOOD=0.734, DEGRADED=0.219, EXCLUDED=0.047
- Low-resistivity: rt_threshold=1.58, n_flagged=806, intervals=[[237.4, 237.7], [282.2, 284.4], [288.3, 288.3], [289.0, 290.3], [293.1, 346.3], [351.1, 354.3], [357.2, 358.3], [367.9, 369.3], [372.6, 374.0], [406.6, 407.1]]
6. Data preparation
Edits applied before compute (by type): degradation: 3, hard_range_mask: 6, range_warn: 2, spike_removal: 162, unit_conversion: 1.
7. Interval definition
- Logged interval: 59.44–1339.75 m
- Analysis window (analyst-restricted): 1150.0–1330.0 m — gross and NTG are measured over this window
- Gross evaluated interval: 180.0 m
- Computed net-pay runs (pre-merge): 3
- 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 | Larionov 1969 (old rocks) | vsh_larionov_old 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=23.4, gr_p95=102.7
10. Resistivity analysis
Low-resistivity scan: rt_threshold=1.58, n_flagged=806, intervals=[[237.4, 237.7], [282.2, 284.4], [288.3, 288.3], [289.0, 290.3], [293.1, 346.3], [351.1, 354.3], [357.2, 358.3], [367.9, 369.3], [372.6, 374.0], [406.6, 407.1]].
Invasion profile (multi-depth resistivities, 8055 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.775; reversed (< 0.8): 0.050; median Rxo/RT 1.555; median Rmed/RT 0.993. 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: 0.102, limestone: 0.243, dolomite: 0.119. 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: 3.2 m swing.
13. Figures
Composite log
Pickett plot
Neutron-density crossplot
Buckles plot
Hingle plot
Distributions
Sensitivity tornado
Net-pay Monte-Carlo distribution
14. Permeability (uncalibrated)
- perm_timur: mean k = 0.50 mD
_Uncalibrated screening estimate (no core); Sw used as the Swirr proxy._
15. Rock quality (uncalibrated)
- rqi: mean = 0.023
_Built on the uncalibrated permeability; indicative only._
16. Derived parameters
- Bulk-volume water (BVW = PHIE*Sw): mean 0.0369 v/v
- Porosity-thickness (Phi·H over net pay): 0.324 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 0.198 m
- Buckles constant (BVW at P10 of net pay): 0.0410 → Swirr (mean) ≈ 0.270 over 14 pay samples
17. Electrofacies
Unsupervised k-means on 1172 samples into 4 electrofacies (sample counts: facies 0: 157, facies 1: 251, facies 2: 276, facies 3: 488). Descriptive only — no core labels.
18. 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
defaultare regional/global — they drive the bracketed tier.
19. 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.
20. 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: 3, hard_range_mask: 6, range_warn: 2, spike_removal: 162, unit_conversion: 1.
| Validator | Type | Detail |
|---|---|---|
| vsh_phie_anticorrelation | support | Vsh-PHIE Pearson 0.87 > 0.3 (dirty rock + high porosity) |
21. Methodology (decision graph)
flowchart TD
dec_1["decision: step: depth_quality"]
act_1["tool_call: depth_quality"]
dec_2["decision: step: review_attempts"]
act_2["tool_call: review_attempts"]
dec_3["decision: step: low_res_scan"]
act_3["tool_call: low_res_scan"]
dec_4["decision: step: interval_stats"]
act_4["tool_call: interval_stats"]
dec_5["decision: step: set_zone_of_interest"]
act_5["tool_call: set_zone_of_interest"]
dec_6["decision: step: crossplot"]
act_6["tool_call: crossplot"]
dec_7["decision: step: lithology"]
act_7["tool_call: lithology"]
dec_8["decision: step: validate_choice"]
act_8["tool_call: validate_choice"]
dec_9["decision: step: permeability"]
act_9["tool_call: permeability"]
dec_10["decision: wasted no-op: permeability"]
dec_11["decision: step: rock_quality"]
act_10["tool_call: rock_quality"]
dec_12["decision: step: derived_parameters"]
act_11["tool_call: derived_parameters"]
dec_13["decision: step: electrofacies"]
act_12["tool_call: electrofacies"]
dec_14["decision: wasted no-op: lithology"]
dec_15["decision: wasted no-op: permeability"]
dec_16["decision: wasted no-op: lithology"]
dec_17["decision: wasted no-op: permeability"]
dec_18["decision: wasted no-op: lithology"]
dec_19["decision: wasted no-op: permeability"]
dec_20["decision: wasted no-op: lithology"]
dec_21["decision: wasted no-op: permeability"]
dec_22["decision: wasted no-op: lithology"]
dec_23["decision: step: rw_evidence"]
act_13["tool_call: rw_evidence"]
dec_24["decision: wasted no-op: lithology"]
dec_25["decision: wasted no-op: permeability"]
dec_26["decision: wasted no-op: lithology"]
dec_27["decision: wasted no-op: permeability"]
dec_28["decision: wasted no-op: lithology"]
dec_29["decision: wasted no-op: permeability"]
dec_30["decision: step: mhi_scan"]
act_14["tool_call: mhi_scan"]
dec_31["decision: wasted no-op: permeability"]22. 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.
23. 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.
24. Conclusions
This interpretation is bracketed, not firm, and should be carried forward as a range. Net pay is most likely near the P50 of 5.6 m but could be as low as 1.2 m (P10) or as high as 16.9 m (P90) across the 180.0 m gross interval, with a net-to-gross of only 0.012 indicating a thin and sparse reservoir. The averages where pay is present — PHIE 0.152, Sw 0.391, and Vsh 0.132 — are consistent with a viable but volumetrically minor target and should be read as indicative given the limited net thickness. The width of the range is driven principally by the cementation exponent m, which is an uncalibrated regional default responsible for a 3.5 m swing in net pay; this is the single largest lever on the result. With one validator objection unresolved and the run flagged DID_NOT_CONVERGE, no point estimate should be treated as confident. The most effective next step is to constrain m locally — through core or a defensible offset calibration — which would meaningfully narrow the bracket before any volumetric or economic decision is taken on this well.
Appendix A — Ledger excerpt (traceability)
{
"net_pay_total_m": 2.1336000000000013,
"net_pay_p10_p50_p90": [
1.2192000000000007,
5.638800000000003,
16.931640000000012
],
"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 | ✓ |