What Does Progressive Gel Strength Mean?
Progressive gel strength refers to the property of the drilling mud to gain strength rapidly with time.
This means that the difference between 10-minute and 10-second gel strength is large. This feature is not desirable in a drilling mud mixture because it indicates that excessive pump pressure will be required to break circulation.
For progressive gels, it is recommended to undertake a 30-minute gel strength measurement to check the progress of gelation.
Trenchlesspedia Explains Progressive Gel Strength
Gel strength indicates the gelling that will take place once the circulation of drilling fluid is stopped. It measures the inter-particle forces that will prevent the cuttings from settling in the borehole.
To break circulation in a high gel mud, high pump pressure is required. The 10-minute and 10-second gel strength indicates the initial gel as per API, and is the shear stress measured at low shear rate after the mud is allowed to set for 10 minutes and 10 seconds respectively.
The drilling fluid is stirred at 600 rounds per minute (rpm) using a viscometer or rheometer. The 3 rpm reading is used to take the gel strength measurement after 10 seconds and 10 minutes. A third reading is also taken after 30 minutes to study if the gel formation is significant in the case of long static periods such as when the bottom hole assembly (BHA) trips.
The mud will create high pump pressure to break circulation after the mud has been static for a long period of time.