This paper describes a new gas-influx detection technique that monitors the acoustic responses of annular measurementwhile-drilling (MWD) pulses to provide a rapid, early warning of the development of potential gas-kick situations. The technique has been evaluated in both water-and oil-based muds during about 40 gas-kick simulations at two full-scale testing facilities. Free gas is identified by amplitude attenuation and phase delay of MWD fundamentals and their harmonic frequencies. Detection is independent of influx location because the entire length of the annulus between the bit nozzles and a surface-pressure transducer is sampled. Detection of potential gas-kick situations generally occurred within minutes of influx initiation, before any significant gas expansion.Some tests also evaluated a downhole MWD mud-resistivity sensor. Results indicated that both these techniques, and particularly the pulse acoustics, can provide unequivocal confirmation of gas and an earlier warning of gas-kick situations than conventional kickdetection techniques.

SPE Member Abstract A dual-basis application of the shale resistivity pore pressure detection technique has been pore pressure detection technique has been developed that emphasizes the availability of MWD formation resistivity measurements while minimizing input from the operator. This method is based upon accepted petrophysical and mechanical principles. Operator inputs are streamlined, requiring one-time-only entry of local air gap, water depth, normal pore pressure gradient, and a baseline value of shale water resistivity. MWD shale resistivity is utilized in the Archie equation to solve for shale porosity. The Baldwin-Butler normal shale compaction pressure is calculated using a generalized Tertiary basin equation. The difference between normal and actual matrix stress values represents the magnitude of change from normal to abnormal pore pressure conditions. Unlike traditional empirical approaches and other, more recent petrophysical-mechanical techniques, this technique does not need data from a normally pressured section for establishment of a normal pressured section for establishment of a normal trend, does not require the degree of local knowledge associated with these of overlays, and involves neither guesswork nor comprehensive expertise on the part of the operator. The model has been successfully tested on approximately 100 well locations in the Gulf of Mexico, offshore Alaska, North Sea, and Niger Delta. Field examples are presented that demonstrate the technique's consistency with principles quantitative accuracy, and relative principles quantitative accuracy, and relative ease of use. Introduction Abnormal formation pressures generated by compaction-related mechanisms have for many years been evaluated through the use of techniques relating a measurement of some formation-related characteristic to depth. These measurements include gamma radiation, resistivity and conductivity, sonic transit time, density, seismic travel time, the drilling exponent, and other less well known or used measurements. The measurements vary both in the manner by which they are acquired (e.g. cuttings analysis, electrical and acoustical wireline logging etc.) and the time when they are made (e.g. before, during, or after drilling). These variations have an obvious effect on the quality of measurement. Differences in the application of any particular measurement by which that measurement may be used for evaluating compaction-related pore pressure. There are numerous pore pressure estimation techniques associated soley with a formation resistivity measurement. Each technique has particular advantages and disadvantages, but all particular advantages and disadvantages, but all share certain traits. Each is applicable only for the clay-shale lithology, and each is based upon an expected response with increasing depth for normally pressured shale formations. Very early applications of these shale resistivity techniques involved the "equivalent depth" method as described in the classic work of Rubey and Hubbert.

Recently, an MWD acoustic technique for gas influx detection was evaluated under fullscale, controlled testing conditions. This technique continually monitors annular MWD pUlse characteristics using a pressure transducer installed on the bell nipple riser pipe. Since the completion of the controlled testing program, the technique has been tested under actual drilling conditions.

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.