(1) (n.) Drilling. A temporary drilling site, usually constructed of local materials such as gravel, shell or even wood. For some long-drilling-duration, deep wells, such as the ultradeep wells of western Oklahoma, or some regulatory jurisdictions such as The Netherlands, pads may be paved with asphalt or concrete. After the drilling operation is over, most of the pad is usually removed or plowed back into the ground. (2) (n.) Drilling. A fluid used to initiate hydraulic fracturing that does not contain proppant. (3) (n.) Formation Evaluation. That part of a wireline logging tool that is pressed firmly against the borehole wall. The pad holds sensors that are focused in one direction and must be as close as possible to the borehole wall. The density detectors and the microresistivity electrodes are examples of sensors that must be placed on pads. Some pads are a rigid part of the logging tool. Others have articulated joints attaching them to the logging tool, with a backup arm to press the pad against the borehole wall. See: Sidewall, Sonde, Wireline Log