As we introduce this discussion on gyp-lime fluids, forget everything you once knew or were told about high calcium in your drill fluids. This fluid mix is not well suited for shallow wells due to increased equipment requirements, but you can use it with success. Typical application is on holes at depths of more than 1500 feet and finished in sandstones or limestones. The benefit of this mix is you can run a lower viscosity for a higher penetration rate and have less pressure on the formation and circulation system. Many of the deeper shale formations have reactive characteristics such as swelling, caving, and flocking from anhy-drates. This fluid will let you drill through anhydrates without any reaction that causes the fluid to flocculate to a paste consistency. Usually, the only way you know you have penetrated an anhydrate zone is to observe the cuttings coming off the shaker screens.
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