TEXAS · WELLS · MARTIN COUNTY · COX 12-9 UNIT 1 LEASE · API 42-317-40785 · DISTRICT 7B
Cox 12-9 Unit 1 #221
Martin County · Spraberry (Trend Area) field · Shut In · Horizontal
Cox 12-9 Unit 1 #221 (API 42-317-40785) is a horizontal well in Martin County operated by Diamondback E&P LLC, completed August 10, 2017 and listed as shut in on the RRC schedule.
The RRC has issued one drilling permit (amended once), issued March 28, 2017, permitted to 9,524 ft.
It was permitted by Endeavor Energy Resources L.P. and has since transferred to Diamondback E&P LLC on the wellbore schedule.
Completion filings report 10 formation tops, including Santa Rosa, Yates, Queen, Grayburg.
Its lease has reported 2.08M barrels of oil and 5.16M mcf of gas since August 2017, last reporting volume in April 2026. The lease carries 13 wells, so these are lease totals, not this well alone.
Operator of record
Permitted by Endeavor Energy Resources L.P.; the EWA schedule now lists a different operator.
- Based in
- Midland, TX
- P-5 status
- Active – Extension (X)
- P-5 last filed
- May 4, 2026
- Permits on file
- 5,254
- Phone
- (432) 221-7400
SOURCE · RRC EWA WELLBORE SCHEDULE
What each RRC source says
| Wellbore schedule | Diamondback E&P LLC |
| Production reports | Diamondback E&P LLCthrough Apr 2026 |
| Latest permit | Endeavor Energy Resources L.P.Mar 28, 2017 |
The sources disagree, which usually means a transfer or a lease-level production filing by a different entity. Petrora goes with the schedule.
- 9,524
- total depth, ft
- 2
- permits on file
- Mar 28, 2017
- last permit issued
- Aug 10, 2017
- completed
- 2.08M
- cumulative oil, bbl
- 5.16M
- cumulative gas, mcf
PRODUCTION FROM PDQ LEASE REPORTS · AUG 2017 THROUGH APR 2026
Regulatory status · RRC wellbore file
- Schedule
- ON SCHEDULE
- Completed
- Aug 10, 2017
- Shut in
- —
- Plugged
- —
Operator's P-5 on the schedule: Active (A)
Surface location
No coordinates on the permit record yet. The RRC's GIS record usually lands within days of issuance; historical master-file permits never carry one.
Wells nearby
Every well with a location on file around this well, in any state, nearest first.
Texas locations come from drilling permits, so most older Texas wells have none and are not listed.
Lease production
PDQ LEASE REPORTS · REPORTED THROUGH APR 2026
Texas reports oil by lease, not by well. These are the lease this well is completed on; they carry 13 wells in total, so volumes are shared.Why →
| Lease | Field | Reporting operator | Wells | Oil, bbl | Gas, mcf | Reported |
|---|---|---|---|---|---|---|
| Cox 12-9 Unit 1 O-10-49245 | Spraberry (Trend Area) | Diamondback E&P LLC | 13 | 2.08M | 5.16M | Aug 2017 – Apr 2026 |
Oil, barrels lease total
Last 12 months 498,220 · prior 12 818,801(-39%)
Gas, mcf lease total
Last 12 months 2,481,154 · prior 12 1,502,229(+65%)
Wells named Cox 12-9 Unit 1
Diamondback E&P LLC's other wells filed under this lease name in Martin County, newest permit first. The RRC gives a gas well its own lease number, so the name is what joins the wells of a unit.
Loading the lease's wellsChain of custody
Every operator that reported production on this well's lease, in order.
- 1Endeavor Energy Resources L.P.Aug 2017 → Dec 2024
- 2Diamondback E&P LLCJan 2025 → Apr 2026
Permits
| Permit | Type | Operator | Received | Issued | Spud | Depth |
|---|---|---|---|---|---|---|
| 824812-98 | Drill | Endeavor Energy Resources L.P. | Apr 21, 2017 | Mar 28, 2017 | — | 11,000 |
| 824812-99 | Drill | Endeavor Energy Resources L.P. | Mar 24, 2017 | Mar 28, 2017 | — | 11,000 |
Completions
| Completed | Lease | Field | Operator | Status | Depth |
|---|---|---|---|---|---|
| Aug 10, 2017 | Cox 12-9 Unit 1 O-10-49245 | Spraberry (Trend Area) | Diamondback E&P LLC | Shut In | 9,524 |
Formation tops
As filed on W-2/G-1. Subsea from 2,834 ft elevation.Download CSV →
| Formation | MD ft | Subsea |
|---|---|---|
| Santa Rosa | 1,000 | 1,834 |
| Yates | 2,750 | 84 |
| Queen | 3,505 | -671 |
| Grayburg | 4,283 | -1,449 |
| San AndresSAN ANDRES - ACTIVE CO2 FLOOD; H | 4,490 | -1,656 |
| Cisco | 5,276 | -2,442 |
| Spraberry | 8,015 | -5,181 |
| Dean | 9,078 | -6,244 |
| Dean | 9,087 | -6,253 |
| Wolfcamp | 9,500 | -6,666 |
| Pennsylvanian | — | — |
Perforations
Perforated and open-hole intervals.
| From | To | Type |
|---|---|---|
| 9,815 | 16,986 | Perforated |
Casing
Strings as reported, shallowest first.
| Casing in | Set at | Hole in | Cement |
|---|---|---|---|
| 13.375 | 1,890 | 17.5 | 1,640 S |
| 9.625 | 6,555 | 12.25 | 380 S |
| 5.5 | 17,112 | 8.5 | 2,485 S |
Completion filings
W-2 and G-1 reports on record in the RRC wellbore file, newest first. The suffix identifies the wellbore or completion event. The record date is the RRC's own date on the record, not the day the report was filed: 462,034 of the state's filings carry 1984-01-12. About these reports →
| Suffix | RRC record date | W-2 / G-1 date | Logs referenced |
|---|---|---|---|
| 00 | Feb 8, 2019 | Dec 13, 2018 | Yes |
| 00 | Feb 12, 2018 | Oct 24, 2017 | Yes |
Well logs
1 log loaded from the RRC's log index, the latest received Jun 9, 2020. Mud log. These are the logs loaded into Petrora from the Railroad Commission's inventories, not necessarily every log run on the well. The RRC holds the files; each opens from its log search for the well. The kind is the RRC's description of the log; the interval is the one filed for it.
Open the RRC's log search for this well ↗| Logas described | Files | Intervalft, as filed | Datereceived | SizeMB |
|---|---|---|---|---|
| MudSpans San Andres, Cisco, Spraberry, Dean, Wolfcamp | TIFF | 5,000 to 17,132 | Jun 9, 2020 | 48.9 |
"Spans" is by this well's own filed formation tops: a formation runs from its top to the next deeper top filed, and the deepest runs to the bottom of the log. Depths are measured along the wellbore, so on a horizontal the lateral counts in the formation it was landed in.
The source documents
Petrora holds the structured record. The scanned filings live at the RRC; these links open its search already filled in for this API.
- Wellbore filings for 42-317-40785 → W-2, G-1, plugging reports, as PDFs
- Completion packets for 42-317-40785 → scanned completion filings
The logs loaded for this well are under Well logs, with the RRC's log search for it. The University Lands library has no per-well link: then paste it into its search.
About this data
Permits from the RRC OGA049M master and daily daf420 files; wellbore and operator of record from the EWA schedule, weekly; completions, formation tops, casing, and perforations from the dbf900 wellbore file; production from PDQ lease reports, which lag two to three months; injection from UIC permits, H-10 reports, and TexNet daily volumes; earthquakes from the TexNet catalog.
New to these records? How to read a well page · API numbers · completion reports and tops · why production is by lease
Developers: this page as JSON is GET /v1/data/wells/31740785, documented in the API reference.