This invention relates to drilling fluids and, more particularly, to the monitoring of a drilling fluid to identify change in its potassium chloride property.
In the rotary drilling of wells, such as those for petroleum oil or gas, a drilling fluid is continuously circulated from the surface of the ground to the bottom of the well and back to the surface of the ground again. The drilling fluid has various functions, including those of lubricating the drill bit and pipe, carrying cuttings from the bottom of the well to the surface of the ground, and imposing a hydrostatic pressure on the drilled formations to prevent escape of oil, gas, or water therefrom into the well during the drilling operations.
Frequently, during the drilling of a well, drilling conditions change. Changes in temperature occur. The character of the formations being drilled may change. Each change in drill conditions can affect the properties of the drilling fluid. Frequently, to counteract the effect of the changed drilling conditions on the properties of the drilling fluid, a change in the composition or character of the drilling fluid is required.
In many cases, the drilling fluid contains potassium chloride or other potassium salts to help in maintaining optimum drilling conditions.
The potassium ion, when used at the proper concentration acts as a shale inhibitor. It interacts with clays, such as illite or montmorillonite, lowers the hydration energy and, in turn, reduces swelling. Without the addition of a shale inhibitor, clay hydration can produce drilling problems, such as wellbore instabilities, stuck pipe, bottomhole fill, torque drag and solids build-up in the drilling fluid. Completion problems may also result because of formation damage in shaly sands, logging and coring failures, hole washout, and poor cement jobs. It is, therefore, important to avoid those problems by maintaining the optimum KC1 content in the drilling fluid as prescribed by drilling operations.
It is, therefore, a specific object of the present invention to provide a method for monitoring the potassium chloride concentration of a drilling fluid during drilling operation so that such concentration may be maintained for optimum drilling operations.