he nature of the various rock layers that will be drilled or the fluids and pressures that may exist in the various formations. Therefore, the well completion and the drilling program are usually overdesigned to assure safety of the operation. This first well, therefore, does not represent the optimum design and would probably cost much more than the rest of the wells that will be drilled in the field.this exploratory well is drilled, samples of the rock cuttings are collected and examined for their composition and fluid content. The data are used to identify the type of formation versus depth and to check on the presence of hydrocarbon materials within the rock. Cores of the formationsare also obtained, preserved, and sent to specialized laboratories for analysis.a petroleum-bearing formation is drilled, the well is tested while placed on controlled production. After the well has been drilled, and sometimes at various intervals during drilling, various logs are taken. There are several logging tools, or techniques, (electric logs, radioactivity logs, and acoustic logs) that are used to gather information about the drilled formations. These tools are lowered into the well on a wireline (electric cable) and, as they are lowered, the measured signals are transmitted to the surface and recorded on computers. The signals collected are interpreted and produced in the form of rock and fluid properties versus depth.exploratory well will provide important data on rock and fluid properties, type and saturation of fluids, initial reservoir pressure, reservoir productivity, and so forth. These are essential and important data and information, which are needed for the development of the field. In most situations, however, the data provided by the exploratory well will not be sufficient. Additional wells may need to be drilled to provide a better definition of the size and characteristics of the new reservoir. Of course, not every exploratory well will result in a discovery. Exploratory wells may result in hitting dry holes or they may prove the reservoir to be a uneconomical devel
