Abstract

While innovations and advances in drill rig and downhole drilling technology have enabled operational efficiencies and productivities in drilling far beyond that achieved even a decade ago, a large proportion of drill rigs today still lack suitable instrumentation that can be utilized to achieve a higher level of drilling performance. Operating with the disadvantages associated with inadequate, inferior, sometimes poorly maintained, and often uncalibrated rig sensors, these rigs are unable to achieve the efficiencies increasingly being demanded by operators and owners. To address this situation, a single point of service has been developed that contains a suite of calibrated and accurate surface rig sensors for acquisition of measurements essential for operations such as drilling optimization. These sensors, housed within an instrumented surface sub, include block height; drillstring tension, torsion, bending moment, bending angle, and rotation speed; mud flowrate, density, pressure and temperature; and drillstring vibrations. The sensor measurements are direct, calibrated, acquired simultaneously at user-configured sampling and recording rates, and possess degrees of accuracies well beyond those of standard rig instrumentation.

Utilizing aerospace, medical, industrial, and proven oilfield technologies, such as acoustics, laser range finding, thin-film strain gages, and product miniaturization, an instrumented sub system is being developed to provide for direct acquisition of the most critical measurements required for drilling optimization. The sub was designed to be located at the top of the drillstring. Primary design considerations included high accuracies of measurements, with traceability of calibrations; simultaneous acquisition of all measurements; preservation and extension of battery life via sophisticated sensor and battery management; very low bit error rates and robustness of radio telemetries; and ease of use tied with flexibility of user customizations.

Early and limited testing of the system indicates accuracies of measurements of hookload, torsion, bending moment, rotation speed, pressure and temperature to be in the range of 1% or better. While characterizations of accuracies for the laser-derived height measurement, volumetric flowrate, and mud density are in the process of being determined, these measurements are innovative and enabling with respect to the unique location in which they are sensed. The acquisition of synchronous measurements facilitates and enhances processing, manipulation and ultimate interpretations of mixed data. Data are telemetered wirelessly from the sub to a surface-based computing and display device via a robust radio communications channel designed and being tested for bit error rates of <1/10,000.

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