Uses of Prehydrated Bentonite

Bentonite is added to water based muds to increase the viscosity and gel strength, suspend solids and increase the carrying capacity of the mud. Bentonite forms a filter cake and, if properly dispersed, is the main agent for reducing water loss. Bentonite will yield in fresh water less than 50 g l salt but not in salty water. Hence if bentonite is to be used in salty water, it must be prehydrated in fresh water. Before adding bentonite to the water or any other chemical , test the water for...

Drill Off Test Procedure

Select a WOB near maximum allowable . 2. Record the time to drill off a weight increment, ie 5000 lbs. 3. Record length of pipe drilled during step 2. 4. From steps 2 and 3 the drill rate in feet per hours may be found. 5. Repeat steps 2 and 3 at least four times. The last test should be at the same value as the first. This repeat test will determine if the formation has changed or not. 6. Plot seconds to drill off versus bit weight. 7. Plot penetration rate versus...

Rules Of Thumb For Bit Selection

Shale has a better drilling response to RPM. Limestone has a better drilling response to bit weight. Bits with roller bearings can be run at a higher RPM than bits with journal bearings. Bits with sealed bearings can give longer life than bits with open bearings, Milled tooth bits with journal bearings can be run at higher weights than milled tooth bits with roller bearings. Diamond product bits can run at higher RPM than three cone bits. Bits with high offset may wear more on gauge. Bits with...