Drilling fluid standards and rules govern every mud twice: API and ISO set material grades and test methods, while EPA, the OSPAR Commission and national regulators set what may be discharged or notified offshore. API Spec 13A alone covers 13 drilling fluid materials.
Each compliance question asks which document, which edition and which waters, and the answers differ across a drilling fluid program.
Nine pages cover the documents, seven API 13-series editions are current, five with an ISO counterpart, and offshore rules run from the 3-mile line in US waters to 1 % oil on dry cuttings under OSPAR.
Standards and regulations are checked against their issuing bodies, product values against the named data sheet and figures against the dated source named in the sentence; see our methodology and fact-checking.
What Are Drilling Fluid Standards and Regulations?#
Drilling fluid standards are the API 13-series documents and their ISO counterparts, while drilling fluid regulations are legal instruments such as 40 CFR 435 in the US and OSPAR Decision 2000/3 in the North-East Atlantic. The API Committee on Standardization of Oilfield Equipment and Materials (CSOEM) lists the 13-series in the API Standards Plan. ISO/TC 67/SC 3 owns ISO 13500, ISO 10414-1, ISO 10414-2, ISO 10416 and ISO 13501.
Standards govern materials and measurements; regulations govern the discharge of mud and cuttings and the notification of each additive before offshore use. Both reach the drilling fluid additives a mud contains: a product needs a grade for the buyer and a discharge status for the operator.
Every Standard and Rule Page in This Section#
Nine pages cover the drilling fluid standards and rules: five API documents (13A, 13B-1, 13B-2, 13I and 13D) and four discharge and notification rules (40 CFR 435, OSPAR, OCNS and PLONOR). The table below compares them; API RP 13C, API RP 13K and ISO 13501 follow under the editions.
| Page | Document or rule | Issuer | Current edition or instrument | What it governs |
|---|---|---|---|---|
| API Spec 13A | API Spec 13A, ISO counterpart ISO 13500:2008 | API; ISO/TC 67/SC 3 | 19th edition (2019) with Addendum 1 (2020), Addendum 2 (2022) and Errata 1 (2024) | Requirements and test procedures for 13 commodity drilling fluid materials |
| API RP 13B-1 | API RP 13B-1, ISO counterpart ISO 10414-1 | API; ISO | 6th edition (2026) | Field testing of water-based drilling fluids |
| API RP 13B-2 | API RP 13B-2, ISO counterpart ISO 10414-2 | API; ISO | 6th edition (2023) with Addendum 1 (2025) | Field testing of nonaqueous (oil- and synthetic-based) drilling fluids |
| API RP 13I | API RP 13I, ISO counterpart ISO 10416:2008 | API; ISO | 9th edition (2020) with Addendum 1 (2023) | Laboratory testing of drilling fluid materials and fluid properties |
| API RP 13D | API RP 13D, no ISO counterpart | API | 8th edition (2026) | Rheology and hydraulics of drilling fluids |
| US offshore discharge rules | 40 CFR 435 Subpart A (and Subpart D, Cook Inlet) | US EPA | eCFR version 2026-10-01 | Discharge of drilling fluids and cuttings in US waters |
| OSPAR rules | OSPAR Decision 2000/3, Decision 2000/2 (HMCS) | OSPAR Commission | Decision 2000/3 in force 2001-01-16 | Use of organic-phase drilling fluids and discharge of their cuttings in the North-East Atlantic |
| OCNS and CHARM | Offshore Chemical Notification Scheme, HOCNF | Cefas for OPRED (UK); SSM (Netherlands) | OSPAR Recommendation 2010/3 (HOCNF); UK Offshore Chemicals Regulations 2002 | Notification and hazard ranking of drilling chemicals |
| PLONOR list | OSPAR PLONOR list | OSPAR Commission | OSPAR Agreement 2013-06, Update 2026 | Substances that pose little or no risk to the marine environment |
Editions checked against the API Standards Plan and ISO Open Data on 2026-10-27.
API Specification vs Recommended Practice: How the 13-Series Is Organized#
API Spec 13A is a Specification with "shall" requirements for manufacturers of named commodity drilling fluid materials, while API RP 13B-1, 13B-2, 13C, 13D, 13I and 13K are Recommended Practices that describe test, evaluation and analysis procedures. The type is part of the name: never "API RP 13A" or "API Spec 13B-1".
The Specification names 13 materials: barite in two density grades, hematite, bentonite, non-treated bentonite, OCMA-grade bentonite, attapulgite, sepiolite, CMC-LVT, CMC-HVT, starch, the polyanionic cellulose grades PAC-LV and PAC-HV, and drilling-grade xanthan gum. Organoclay, PHPA, calcium carbonate and lost circulation materials carry no API 13A grade.
Buyers name a material by its API 13A grade and check API Monogram licensees on the API Composite List. Mud engineers and laboratories follow the Recommended Practices.
Current Editions of the API 13-Series and Their ISO Counterparts#
Seven API 13-series documents are current on the API Standards Plan (checked 2026-10-27), the newest being API RP 13B-1 and API RP 13D from 2026. Each ISO document is an ISO counterpart, because API revised 13A, 13B-1, 13B-2 and 13I on its own.
Superseded editions still circulate as free PDFs; the register below shows which edition is current and which is superseded.
| Document | Type | Current edition (API Standards Plan, checked 2026-10-27) | Next edition | ISO counterpart | Superseded edition not to cite as current |
|---|---|---|---|---|---|
| API Spec 13A | Specification | 19th edition (2019) with Addendum 1 (2020), Addendum 2 (2022) and Errata 1 (2024) | 20th edition in development | ISO 13500:2008 with Cor 1:2009 and Amd 1:2010 | 18th edition (2010) |
| API RP 13B-1 | Recommended Practice | 6th edition (2026) | None listed | ISO 10414-1 | 5th edition (2019) |
| API RP 13B-2 | Recommended Practice | 6th edition (2023) with Addendum 1 (2025) | None listed | ISO 10414-2 | 5th edition (2014) |
| API RP 13I | Recommended Practice | 9th edition (2020) with Addendum 1 (2023) | 10th edition in development | ISO 10416:2008 (ISO/DIS 10416 at DIS stage) | 8th edition |
| API RP 13D | Recommended Practice | 8th edition (2026) | None listed | No ISO counterpart | 7th edition, September 2017, reaffirmed 2023, superseded 2026 |
| API RP 13C | Recommended Practice | 6th edition (December 2023) | 7th edition in development | ISO 13501:2011 | Any edition before the 6th |
| API RP 13K | Recommended Practice | 4th edition (2022) | None listed | No ISO counterpart | Any edition before the 4th |
"None listed" means the API Standards Plan showed no edition in development on 2026-10-27.
API RP 13B and ISO 10414: Field testing of water-based and nonaqueous fluids#
API RP 13B is a two-part practice: 13B-1 for water-based fluids (6th edition, 2026) and 13B-2 for nonaqueous fluids (6th edition, 2023, with Addendum 1 of 2025), and ISO 10414-1 and ISO 10414-2 are their ISO counterparts. API RP 13B-1 covers density, rheology and gels, filtration, retort, sand, methylene blue, pH, alkalinity, chloride, hardness and low-gravity solids. API RP 13B-2 adds electrical stability, lime and salinity, and its 6th edition is titled "Field Testing Nonaqueous-based Drilling Fluids".
Each of the API RP 13B field tests reports one property in a stated unit, such as mud weight in lb/gal (sg; kg/m3).
Standards without their own page: API RP 13C, API RP 13K and ISO 13501#
Two API Recommended Practices have no page of their own: API RP 13C, Drilling Fluid Processing Systems Evaluation (6th edition, December 2023), and API RP 13K, Chemical Analysis of Barite (4th edition, 2022). ISO 13501:2011 is the ISO counterpart of API RP 13C and is not intended for comparing individual equipment. API RP 13K serves barite quality checks.
How Drilling Fluid Rules Differ by Jurisdiction#
Drilling fluid rules differ by jurisdiction: US federal waters regulate the discharge of mud and cuttings, while the OSPAR area also controls each chemical through notification and ranking. In the US, 40 CFR 435 Subpart A allows water-based fluid and cuttings to be discharged only beyond 3 miles (4.8 km) from shore (all Alaskan facilities follow the beyond-3-mile limits); whole non-aqueous fluid is never discharged.
In the North-East Atlantic, OSPAR Decision 2000/3 allows no diesel-based fluids and, since 2001, no discharge of cuttings carrying more than 1 % oil on dry cuttings. The UK and the Netherlands notify chemicals through the Offshore Chemical Notification Scheme (OCNS); Norway caps cuttings at 10 g/kg dry mass (Activities Regulations s.68).
The table below compares eight jurisdictions by instrument and scope.
| Jurisdiction | Instruments (section, date) | What they control | Page |
|---|---|---|---|
| US federal offshore | 40 CFR 435 Subpart A (435.12 to 435.15); NPDES GMG290000 (western Gulf OCS, EPA Region 6, 2023-05-11 to 2028-05-10) | Discharge of drilling fluids and cuttings | US offshore discharge rules |
| US coastal and onshore | 40 CFR 435 Subpart D (435.43, Cook Inlet only); Subpart C (435.32) | No discharge except Cook Inlet; no discharge to navigable waters onshore | US offshore discharge rules |
| US onshore waste | 40 CFR 261.4(b)(5) RCRA exclusion; state rules, for example Louisiana Statewide Order 29-B | Waste status and land treatment | drilling waste management |
| OSPAR area (North-East Atlantic) | Decision 2000/3 (2001-01-16); Decision 2000/2 HMCS with Decisions 2005/1 and 2023/02 (2024-01-16); Recommendation 2010/3 HOCNF (2011-01-01); Agreement 2013-06 PLONOR, Update 2026 | Organic-phase fluids and cuttings; chemical use and discharge | OSPAR rules; PLONOR list |
| United Kingdom | Offshore Chemicals Regulations 2002 (SI 2002/1355) as amended; OCNS | Permits for chemical use and discharge; CHARM and OCNS ranking | OCNS and CHARM |
| Netherlands | OCNS; regulator State Supervision of Mines (SSM) | Chemical notification and ranking | OCNS and CHARM |
| Norway | Activities Regulations s.63 (green, yellow, red and black categories) and s.68 (cuttings) | Chemical categories; cuttings discharge | OSPAR rules |
| Canada | Offshore Chemical Selection Guideline (2024-10-28); Alberta AER Directive 050 (2024-11-13) | Offshore chemical selection; onshore drilling waste | OCNS and CHARM; drilling waste management |
Instruments as read from eCFR (version 2026-10-01), OSPAR, Cefas, legislation.gov.uk and Havtil.
On US land, 40 CFR 261.4(b)(5) excludes drilling fluids from hazardous waste; state rules still apply. These rules frame drilling fluids and the environment.
How to Choose the Standard or Rule That Applies#
Pick the document by the question: a material grade points to API Spec 13A, a rig-site test to API RP 13B-1 or 13B-2, a laboratory test to API RP 13I, and a discharge to the local rule. The seven steps are listed below.
- Specify an API 13A material by grade name.
- Test water-based mud with API RP 13B-1.
- Test oil- or synthetic-based mud with API RP 13B-2.
- Evaluate fluids in the laboratory with API RP 13I.
- Model rheology and hydraulics with API RP 13D.
- Check a US offshore discharge against 40 CFR 435 and the NPDES permit.
- Notify a UK or Dutch chemical through OCNS, check its PLONOR status and, in Norway, its s.63 category.
How Standards and Rules Change: Revisions, Reviews and News#
API reviews each standard at least every five years and revises, reaffirms or withdraws it, with a one-time extension of up to two years. ISO/DIS 10416 is at DIS stage, so ISO 10416:2008 stays current.
In eCFR version 2026-10-01, 40 CFR 435 was last amended on 2021-01-04. Dated items appear in the news on standards and discharge rules.
Standards and the Tests, Materials and Additive Classes They Govern#
Standards end where the mud meets a material or a test: API Spec 13A governs the material, API RP 13B-1, 13B-2 and 13I govern the measurement.
API RP 13J (6th edition, 2023) tests completion brines, not covered here. API RP 13L (3rd edition, 2024) covers fluids specialist training, also not covered here.
Where a test method becomes a rule: EPA Method 1674#
EPA Method 1674, the retort method for base fluid retained on cuttings, is Appendix 7 to 40 CFR 435 Subpart A. It is derived from API RP 13B-2, but it is an EPA method, not an API method.
Where standards meet materials such as barite#
API Spec 13A sets density, soluble calcium and particle-size limits for barite but no mercury or cadmium limit; those stock-barite limits are in 40 CFR 435.13 and 435.15.
Each material page states its own requirement values. The grades and discharge status of barite follow this split.
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