Drilling grade bentonite, OCMA and API 13A
Soda-activated sodium bentonite for water-based drilling fluids, offered to two API 13A specifications: OCMA-grade and Section 9. Every shipment carries a certificate of analysis from an independent NABL-accredited laboratory.
API Spec 13A · OCMA-grade and Section 9
OCMA grade is what most Gulf drilling contractors and mud companies ask for by name. It is defined in API Specification 13A, tested by the API 13B-1 methods, and it is the grade we ship most.
Where a buyer needs the higher-yield Section 9 bentonite, we supply that as a separate lot under its own batch code. The two are never blended or relabelled.
The clay is mined from our own leases in Kutch, activated with soda ash in our own yard, aged, sun-dried, then ground and bagged at our partner plant 43 km from Mundra Port.
Where it is used
Drilling grade bentonite specification
OCMA-grade bentonite
API Spec 13A · OCMA-grade bentonite
| Property | Test method | Unit | Standard requires | Our typical | Guaranteed range |
|---|---|---|---|---|---|
| Viscometer dial reading at 600 r/min | API 13B-1 | dial reading | min 30 | 33 | 31–36 |
| Yield point / plastic viscosity ratio | API 13B-1 | — | max 6 | 4.1 | ≤ 5.5 |
| Filtrate volume, 30 min | API 13B-1 | cm³ | max 16.0 | 14.6 | ≤ 15.5 |
| Residue greater than 75 µm | Wet sieve | % by mass | max 2.5 | 1.9 | ≤ 2.3 |
| Moisture as shipped | Oven dry, 105 °C | % | — | 10.5 | ≤ 12.0 |
| Swell index | ASTM D5890 | mL/2 g | — | 22 | 20–25 |
| pH, 2% suspension | pH meter | — | — | 9.6 | 9.0–10.3 |
API 13A Section 9 bentonite
API Spec 13A · Section 9, Bentonite
| Property | Test method | Unit | Standard requires | Our typical | Guaranteed range |
|---|---|---|---|---|---|
| Viscometer dial reading at 600 r/min | API 13B-1 | dial reading | min 30 | 32 | 31–35 |
| Yield point / plastic viscosity ratio | API 13B-1 | — | max 3 | 2.5 | ≤ 2.9 |
| Filtrate volume, 30 min | API 13B-1 | cm³ | max 15.0 | 13.9 | ≤ 14.8 |
| Residue greater than 75 µm | Wet sieve | % by mass | max 4.0 | 2.4 | ≤ 3.5 |
| Moisture as shipped | Oven dry, 105 °C | % | max 10 | 8.9 | ≤ 9.8 |
| Swell index | ASTM D5890 | mL/2 g | — | 24 | 22–27 |
How far inside the API 13A limits we run
Our typical values against each limit. Green is the passing zone, the red line is the limit.
Typical usage
Water-well and HDD: 25–50 kg per m³ of make-up water, adjusted on site to the Marsh funnel viscosity the job needs. Pre-hydrate in fresh water before adding other additives. Indicative only; your mud engineer's checks govern.
Packing and shipping
25 kg laminated PP bags, sealed. Floor-loaded at 1,040 bags, 26.0 MT net per 20ft container, with desiccants fitted. Jumbo bags on request.
MOQ one 20ft FCL · CFR or CIF · Mundra Port
Frequently asked questions
What is the difference between OCMA grade and API 13A Section 9 bentonite?
Both are defined in API Specification 13A and tested by API 13B-1 methods, and both need a 600 r/min dial reading of at least 30. OCMA-grade allows a yield point to plastic viscosity ratio up to 6 and filtrate up to 16.0 mL, but has a tighter residue limit of 2.5%. Section 9 bentonite needs a ratio of 3 or less, filtrate of 15.0 mL or less and residue of 4.0% or less.
Which API 13A section is OCMA grade in?
In the current 19th edition of API Specification 13A, OCMA-grade bentonite is Section 19. Earlier editions listed it as Section 11. The test limits did not change with the renumbering.
Is your drilling bentonite natural sodium bentonite?
No. It is Kutch bentonite activated with soda ash, which is standard practice for Indian drilling bentonite and is accepted by API 13A. We say so on every datasheet and certificate.
Do you hold the API Monogram?
No. We supply to the API 13A specification with a certificate of analysis from an independent NABL-accredited laboratory for every shipment. Pre-shipment inspection by SGS, Bureau Veritas or Intertek can be arranged on request.
Can you provide an XRD report?
Yes. An XRD mineralogy report for the grade, showing montmorillonite and quartz content, is available on request, alongside the certificate of analysis for each shipment.
What is the minimum order?
One 20ft container: 1,040 bags of 25 kg, 26 tonnes net, shipped from Mundra Port on CFR or CIF terms.
Other products: Civil / piling gradeFoundry gradePelletising gradePlastic white clay
Test it against what you buy today.
A 2.5 kg sample with its certificate of analysis, sent by DHL or FedEx. Tell us your current supplier's figures and we will tell you honestly how ours compare.