Vladimir Dubinsky

An MWD Downhole Assistant Driller

Identification of drilling problems is most commonly achieved by simple comparisons of surface and downhole time-averaged measurements of weight and torque, or by shock and vibration sensors located either downhole or at the surface. Various drilling phenomena are more complex than can be described by these simple shock and vibration measurements. The interpretation of drilling vibration data collected at the surface requires specialized expertise, and can be difficult. Sometimes downhole phenomena are not interpretable at the surface. The diagnosis of bottom hole assembly (BHA) vibrations measured directly by a downhole tool is much easier. A prototype downhole assistant driller measurement-while-drilling (MWD) device has been constructed that unambiguously diagnoses drilling phenomena from sensors that are located in the BHA, and that are sampled at a high frequency. Processing algorithms programmed into the prototype identify bit bounce, stick-slip, backward rotation, torque shocks, BHA whirl, pressure anomalies and excessive stress. Drilling efficiency and specific energy at the bit are also calculated. Average weight and torque values as well as drilling diagnostics are transmitted to the surface and enable the driller to make real-time improvements to the drilling process in a timely manner. A key requirement for enhancing drilling performance is the ability to simply and clearly display information about the drilling process on the rig floor. The prototype display not only informs the driller about the severity of drilling phenomena but also provides advice about how to eliminate particular drilling inefficiencies before they become problematic. The real-time drill floor display effectively completes the loop between the MWD prototype in the bottom hole assembly and the drillers controls. Additional displays and logs permit the post-drilling assessment of data from previously drilled intervals. The downhole assistant driller helps optimize the rate of penetration, and reduce bit, motor, MWD and other BHA component failures. Downhole drilling parameters, together with quality conventional surface measurements, identify drilling problems and help drillers better decide when to make short wiper runs, or when to trip for a bit. A method for closed-loop drilling operations is presented. This paper reviews the test program and draws conclusions from long term research with both downhole and surface drilling measurements. Actual field results demonstrate how downhole measurements provide a clearer feel for BHA behavior, and allow the driller to optimize the drilling process, reduce BHA component damage, and improve the efficiency of the drilling operation.

An Interactive Drilling Dynamics Simulator for Drilling Optimization and Training

The dynamic behavior of the drill bit is a critical factor in drilling efficiency. It affects ROP, hole conditions and the frequency of bit trips. Improved understanding of this behavior can result is significant improvements in all of these areas. For this reason an interactive PC-based simulator has been developed. This system simulates the dynamic behavior of the drill bit for various drilling conditions. These conditions are defined by numerous downhole and surface factors, such as hook load, RPM, mud properties and flow rate, BHA configuration, drill bit design, borehole parameters, and formation properties. This system allows for accurate simulation of the major drilling dynamic dysfunctions, such as bit bounce, lateral vibrations, BHA / bit whirl, torque shocks, stick-slip and torsional oscillation. The system was developed using field test results and both theoretical and practical knowledge about dynamic behavior of the drillstring, BHA and drill bit under certain drilling conditions. The so-called System Identification approach has been used as a basic tool for creating the simulators internal model. The downhole dynamic and static measurements required for developing such a model were recorded at a high sampling rate during the field test of a prototype of an MWD downhole dynamics tool. The simulator has certain self-learning capabilities and its smartness depends upon the amount of data used for developing and training the model. The simulator could be used as a key element in a closed loop drilling system which would allow the driller to be more reactive to any undesirable change in downhole dynamic conditions. By using the simulator on-line, one could play different scenarios (i.e., drilling ahead based on the existing or anticipated drilling conditions). This could improve the selection of drilling parameters from the surface prior to event occurrence. Therefore, ROP could be optimized while reducing the severity of downhole dynamic dysfunctions. The simulator could also be efficiently used as a training tool for MWD operators and drilling personnel.

APPLICATION OF SPECIAL FILTERING TECHNIQUES IN THE ANALYSIS OF EMAT DATA

The applicability of Electromagnetic Acoustic Transducers (EMAT) for downhole applications in the oil and gas industry is being currently investigated. This application, when compared to conventional usage of EMAT for pipeline inspection, imposes significant engineering and data processing challenges due to difficult downhole conditions, wide variability of casing sizes (both in diameter and thickness) and signal to noise ratio (SNR) limitations. In this paper the investigation of different filtering techniques and methods aimed at analyzing EMAT data for various downhole scenarios, separation and detection of different modes and improvement of SNR is detailed. The techniques being investigated are frequency (FIR) filtering, Gaussian wavelet decomposition, synchronous detection and their combination. The methods and techniques proposed are confirmed and validated based on the results obtained from the numerical simulations and experiments with physical models.

Obtaining anisotropic velocity data for proper depth seismic imaging

The paper deals with the problem of obtaining anisotropic velocity data due to continuous acoustic impedance-based measurements while scanning in the axial direction along the walls of the borehole. Diagrams of full conductivity of the piezoceramic transducer were used to derive anisotropy parameters of the rock sample. The measurements are aimed to support accurate depth imaging of seismic data. Understanding these common anisotropy effects is important when interpreting data where it is present.

Using Radon Transform For Efficient Acoustic Wave Separation By Velocities In Wireline And Lwd Acoustic Logging

Different acoustic wave components in the borehole acoustic logging differ by frequencies, amplitudes, travel times, and velocities. Depending on the application, some of these components are considered to be informative, and others are detrimental. In some cases, wave propagation conditions and certain tool design limitations do not allow distinct separation of these components without destructive interference between them. Simple time-frequency filtering does not always solve these problems. For example, in case of poor quality of casing cementing job the casing “rings”, and this ringing dominates the informative signal of interest that propagates through the formation. The frequency separation is inefficient in this case, due to the overlapping of the signal frequencies. We propose adding “time-velocity” signal representation to the traditional “time-frequency” consideration. We demonstrate incremental improvement in the data quality when progressing from the traditional Semblance method to the improved non-windowed Hilbert Semblance, and finally to a special case of the Radon transform. We believe the proposed approach can be adapted and efficiently used for different borehole acoustic or seismic applications.