Petrophysical Interpretation Report — 15-135-25990-00-00
| Well (UWI) | 15-135-25990-00-00 |
| Log date | 2/11/2018 |
| Service company | Pioneer Energy Services |
| Acquisition date (header) | 2/11/2018 |
| PLSS location | Sec 31 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
⚠️ 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)
This interval must be read as a bracketed estimate, not a firm result. The run DID NOT CONVERGE, and with one unresolved mechanical objection still open in the QC loop, the numbers below are an uncalibrated engineering estimate reported for transparency only. Net pay across the 180.0 m gross section could range from as little as 2.6 m to as much as 33.1 m, with a central figure near 8.4 m — a very thin net-to-gross of only 0.027. Where pay is developed, the rock reads reasonably: effective porosity averages 0.184, water saturation sits near 0.375, and shale volume is modest at about 0.153. But those averages rest on a water-resistivity value (Rw) carried as a regional default rather than a locally calibrated measurement, and that single uncalibrated parameter alone drives roughly 7.8 m of swing in the pay estimate. With no core control to anchor the interpretation, this summary is a range bounded by Rw uncertainty — nothing more. Local Rw calibration is the clear priority before any volumetric decision rests on these numbers.
Net pay P10 / P50 / P90 = 2.6 / 8.4 / 33.1 m.
Net pay is dominated by 'Rw', 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: 59.44–1376.17 m
- Log date: 2/11/2018
- Service company: Pioneer Energy Services · Company: SCHABEN OIL, LLC
- 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 | PHID_SVC | count 4 |
| hard_range_mask | DRHO | count 4 |
| hard_range_mask | RT | count 151 |
| hard_range_mask | RMED | count 82 |
| range_warn | RHOB | count 4 |
| range_warn | NPHI | count 15 |
| spike_removal | — | 134 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=27.3, gr_p95=100.5
- Bad-hole: GOOD=0.748, DEGRADED=0.21, EXCLUDED=0.041
- Low-resistivity: rt_threshold=1.33, n_flagged=836, intervals=[[292.0, 293.7], [300.7, 356.9], [361.6, 366.4], [418.9, 419.4], [435.1, 435.3], [438.0, 439.8], [478.1, 484.6], [495.3, 496.8], [501.9, 503.1], [508.1, 512.5]]
6. Data preparation
Edits applied before compute (by type): degradation: 2, hard_range_mask: 4, range_warn: 2, spike_removal: 134, unit_conversion: 1.
7. Interval definition
- Logged interval: 59.44–1376.17 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): 6
- 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=27.3, gr_p95=100.5
10. Resistivity analysis
Low-resistivity scan: rt_threshold=1.33, n_flagged=836, intervals=[[292.0, 293.7], [300.7, 356.9], [361.6, 366.4], [418.9, 419.4], [435.1, 435.3], [438.0, 439.8], [478.1, 484.6], [495.3, 496.8], [501.9, 503.1], [508.1, 512.5]].
Invasion profile (multi-depth resistivities, 8346 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.931; reversed (< 0.8): 0.032; median Rxo/RT 2.380; median Rmed/RT 1.073. 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: 0.099, limestone: 0.186, dolomite: 0.167. 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: 7.8 m swing.
13. Figures
Composite log
Pickett plot
Neutron-density crossplot
Buckles plot
Hingle plot
Distributions
Sensitivity tornado
Net-pay Monte-Carlo distribution
14. Derived parameters
- Bulk-volume water (BVW = PHIE*Sw): mean 0.0489 v/v
- Porosity-thickness (Phi·H over net pay): 0.897 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 0.563 m
- Buckles constant (BVW at P10 of net pay): 0.0350 → Swirr (mean) ≈ 0.190 over 32 pay samples
15. Permeability (uncalibrated)
- perm_timur: mean k = 4.08 mD
_Uncalibrated screening estimate (no core); Sw used as the Swirr proxy._
16. Rock quality (uncalibrated)
- rqi: mean = 0.062
_Built on the uncalibrated permeability; indicative only._
17. Electrofacies
Unsupervised k-means on 1155 samples into 4 electrofacies (sample counts: facies 0: 448, facies 1: 210, facies 2: 378, facies 3: 119). 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 Rw — 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: 2, hard_range_mask: 4, range_warn: 2, spike_removal: 134, 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 | 6 depths with Sw<0.4 but RT<5.0 ohm-m |
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: crossplot"]
act_3["tool_call: crossplot"]
dec_4["decision: step: set_zone_of_interest"]
act_4["tool_call: set_zone_of_interest"]
dec_5["decision: step: compare_methods"]
act_5["tool_call: compare_methods"]
dec_6["decision: step: validate_choice"]
act_6["tool_call: validate_choice"]
dec_7["decision: step: derived_parameters"]
act_7["tool_call: derived_parameters"]
dec_8["decision: step: lithology"]
act_8["tool_call: lithology"]
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: objection_profile"]
act_11["tool_call: objection_profile"]
dec_13["decision: wasted no-op: lithology"]
dec_14["decision: step: electrofacies"]
act_12["tool_call: electrofacies"]
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: wasted no-op: permeability"]
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: wasted no-op: lithology"]
dec_31["decision: wasted no-op: permeability"]
dec_32["decision: wasted no-op: lithology"]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): Rw (calibrated by produced-water salinity or a Pickett/SP Rw calibration).
- 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
The interpretation does not converge and is tagged BRACKETED; it should not be used as a confident point estimate. The headline outcome is a wide net-pay range of 2.6 m (P10) to 33.1 m (P90) about a central 8.4 m (P50) over a 180.0 m gross interval, a net-to-gross of only 0.027. The width of that range is governed almost entirely by Rw, which is carried as a regional default and accounts for about 7.8 m of the swing. Within the intervals that meet cutoffs, the rock quality itself is unremarkable but not discouraging — PHIE near 0.184, Sw near 0.375, and Vsh near 0.153 — yet these figures inherit the same uncalibrated Rw and so cannot be read as firm. Two validator objections remain, one of them an unresolved mechanical objection that triggers the abstention on this run. The single, unambiguous next step is local Rw calibration; until that is in hand, no volumetric or completion decision should rest on these numbers, and no core, mud-log, or pressure data were available to independently anchor the result.
Appendix A — Ledger excerpt (traceability)
{
"net_pay_total_m": 4.876800000000003,
"net_pay_p10_p50_p90": [
2.5908000000000015,
8.382000000000005,
33.11652000000003
],
"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 | ✓ |