About API 13A Section 9 Drilling Grade Bentonite
API 13A Section 9 bentonite is the drilling-grade sodium bentonite specified for water-based drilling fluids. In fresh water it hydrates to build viscosity and gel strength, lifts and suspends drilled cuttings, and lays down a thin, low-permeability filter cake on the borehole wall that limits fluid loss into permeable formations.
Section 9 is the tighter of the two bentonite specifications we supply. It requires a 600 r/min viscometer dial reading of at least 30, a yield point to plastic viscosity ratio no greater than 3, filtrate of 15.0 cm³ or less, and no more than 4.0 % by mass of residue above 75 µm. The low YP/PV limit points to an efficient, well-dispersed clay rather than one that depends on flocculation for apparent viscosity. When a mud programme asks for API bentonite without naming a section, Section 9 is normally what it means.
Our drilling grade is produced from selected sodium bentonite, dried, milled and classified to control fineness and residue. Every batch is tested in our NABL-accredited laboratory using API 13A procedures, and the results appear on the Certificate of Analysis supplied with the shipment. The applicable edition of API 13A should be confirmed at order. The grade suits oil and gas, water-well, mineral exploration and horizontal directional drilling programmes.
Typical specifications
| Parameter | Typical Value | Test Method |
|---|---|---|
| Viscometer dial reading at 600 r/min | ≥ 30 (API 13A requirement) | API 13A, Section 9 |
| Yield point / plastic viscosity ratio | ≤ 3 (API 13A requirement) | API 13A, Section 9 |
| Filtrate volume | ≤ 15.0 cm³ (API 13A requirement) | API 13A, Section 9 |
| Residue > 75 µm | ≤ 4.0 % by mass (API 13A requirement) | API 13A, Section 9 |
| Moisture | ≤ 10 % (typical) | Internal method |
| Form | Free-flowing powder | Visual |
| Colour | Cream to grey | Visual |
API 13A requirements are the specification limits each batch is tested against; confirm the applicable API 13A edition at order. Other values are typical, for guidance. Guaranteed limits are stated on the Technical Data Sheet and batch CoA.
Key features & benefits
Tested to Section 9 limits
Every batch is tested for 600 r/min dial reading, YP/PV ratio, filtrate volume and residue above 75 µm using API 13A procedures, so the CoA can be checked line by line against your mud programme.
Predictable viscosity build
A minimum 600 r/min reading of 30 in the standard API suspension gives mud engineers a dependable starting point for funnel viscosity and gel strength in freshwater spud and top-hole muds.
Thin, tight filter cake
Filtrate held at or below 15.0 cm³ in the API test reflects a compressible, low-permeability cake that helps stabilise the wellbore and reduce fluid invasion into permeable sands.
Low YP/PV ratio
The Section 9 ceiling of 3 on YP/PV ratio favours a dispersed clay structure, giving better control of rheology when thinners, polymers or weighting agents are added later in the well.
Controlled grit content
Residue above 75 µm is held within the 4.0 % limit, which keeps abrasive coarse solids down and reduces wear on pump liners, bits and solids-control equipment.
Applications
Oil and gas spud and top-hole muds
Freshwater bentonite muds for surface and intermediate hole sections, where the clay provides hole cleaning, cuttings suspension and wall cake before the system is converted, inhibited or weighted up.
Water-well and exploration drilling
Simple bentonite and water systems for rotary water-well, mineral exploration and geotechnical drilling, where good cuttings lift and a firm wall cake help keep unconsolidated formations open.
Horizontal directional drilling
Base viscosifier for HDD and trenchless drilling fluids, carrying cuttings out of the bore, stabilising the hole and lubricating the product pipe during pullback. Polymers are often added in reactive clays.
Usage & handling
- Typical concentration in fresh water is about 20–70 kg/m³ (roughly 7–25 lb/bbl), depending on hole size, formation and target viscosity.
- Add slowly through a mixing hopper and allow at least 30 minutes of agitation, ideally longer, before adding salts, lime or cement-contaminated returns.
- Calcium and chloride in make-up water reduce yield; treat hard water with soda ash and keep chlorides as low as practical.
- Store bags and jumbo bags dry and covered on pallets, away from rain and standing water at the rig site or yard.
Packaging & supply
- 25 kg and 50 kg HDPE or paper bags for rig-site handling
- 1 MT and 1.2 MT jumbo (FIBC) bags for mud plants and bulk mixing
- Custom or private-label packaging on request
- MSDS, Technical Data Sheet and batch CoA with each shipment
Frequently asked questions
What are the API 13A Section 9 requirements for bentonite?
API 13A Section 9 sets four physical requirements for drilling bentonite: a viscometer dial reading at 600 r/min of at least 30, a yield point to plastic viscosity ratio of 3 or less, filtrate volume of 15.0 cm³ or less, and residue above 75 µm of no more than 4.0 % by mass. We test each batch against these limits. Please confirm the edition of API 13A your contract refers to at order.
How is Section 9 bentonite different from Section 11 OCMA-grade bentonite?
Both require a 600 r/min reading of at least 30. Section 9 is stricter on rheology and fluid loss, with YP/PV of 3 or less and filtrate of 15.0 cm³ or less. Section 11 OCMA grade allows YP/PV up to 6 and filtrate up to 16.0 cm³, but limits residue above 75 µm to 2.5 % rather than 4.0 %. Buy the section your mud programme or tender names.
Which edition of API 13A do you test against?
API 13A is revised from time to time, and contracts may refer to different editions. Tell us the edition your programme or tender cites when you enquire, and we will confirm that the test procedures and limits on our Certificate of Analysis match it. The requirements shown on this page reflect the Section 9 limits and should be read alongside the edition you specify.
Can Section 9 drilling bentonite be used in salt water?
Sodium bentonite yields poorly when mixed directly into salt water or brine, because dissolved salts suppress swelling. If the system must be salty, pre-hydrate the bentonite in fresh water first and then add it to the active system, or use a saltwater viscosifier. For saturated salt muds, consider our API 13A Section 12 attapulgite, which builds viscosity in salt water.
What documents come with an API bentonite shipment?
Each shipment of drilling bentonite is supplied with a batch Certificate of Analysis showing the API 13A test results, plus a Technical Data Sheet and MSDS. Testing is carried out in our NABL-accredited laboratory under ISO 9001 certified processes. If your tender or customs process needs additional documents, list them at enquiry and we will confirm what can be provided.