The cost and operational limitations of deploying downhole seismic sensors have often precluded the acquisition of important reservoir data. The need exists for a retrievable borehole seismic package or array that can be repeatedly deployed in production wells without pulling production tubing for each use. Engineering calculations, cost analyses and scientific discussion have shown the technical feasibility of using coiled tubing and miniaturized hardware for drilling 1.125 in. diameter boreholes to depths ranging form 100 to 10,000 ft. Modern electronics and advances in sensor technology make the miniaturization of borehole packages possible. Microboreholes have the potential to be drilled for less than one-fifth the cost of conventional wellbores. The goal was to develop, evaluate and field test miniature sensors for use in microboreholes.