Computer Application of Principal Component Analysis to Boundary Identification and Well-to-Well Correlation

Many studies have employed automated procedures in well-log interpretation to aid the identification of formation boundaries, and perform cross-correlation between formations in different boreholes. These investigations have demonstrated the use of only one well-log variable, usually resistivity or Gamma Ray logs in the process. In conventional well-log interpretation, different well-log variables or a group of variables are used for different tasks. This project makes use of principal components and spectral analysis as the basis for well-log interpretation, including automatic formation boundary identification and cross-correlation using the first principal component of well-log variables. By transforming a set of well-log data using principal components analysis a single new variable is extracted from the first principal component scores which accounts for a significant amount of the variation within the original data. A further improvement in the results is obtained by passing the data through a moving filter to reduce noise. Boundary identification is performed by generalized distance (D2 ) method. Cross-correlation between the filtered principal components of two boreholes is then made by matching each formation of one borehole with a part of another. Both the stretch factor which accounts for thickening or thinning between sequences and the relative vertical displacement of the formation are calculated. This requires the calculation of the power spectra, derived form the fast Fourier transform of the principal component data, with high pass filtering using the derivative filter to obtain the appropriate resolution. This new technique was applied on model and real well-log data from five boreholes in the Attahaddy field, Libya. Although the Attahaddy field is structurally complex, the method was found to be reliable at predicting both the geological boundaries of the different formations, and the correlation of formations between boreholes. The distinctive value of this new approach is in its application of the first principal component of the original well-log variables. Such application has many advantages over the previous studies. PCAXCOR is a new computer program written in F77 to perform all the necessary computation for boundary identification and well-to-well correlation based on principal component analysis. Graphical output of the results uses a number of new functions in the S language

Biocompatibility and biodegradation studies of a commercial zinc alloy for temporary mini-implant applications

In this study, the biocompatibility and in vitro degradation behaviour of a commercial zinc-based alloy (Zn-5 Al-4 Mg) were evaluated and compared with that of pure zinc for temporary orthopaedic implant applications. Biocompatibility tests were conducted using human alveolar lung epithelial cells (A549), which showed that the zinc alloy exhibits similar biocompatibility as compared to pure zinc. In vitro degradation evaluation was performed using weight loss and electrochemical methods in simulated body fluid (SBF) at 37 degrees C. Weight loss measurements revealed that the degradation of the zinc alloy was slightly lower during the initial immersion period (1-3 days), but marginally increased after 5 and 7 days immersion as compared to pure zinc. Potentiodynamic polarisation experiments showed that the zinc alloy exhibits higher degradation rate than pure zinc. However, electrochemical impedance spectroscopy analysis suggests that pure zinc is susceptible to localized degradation, whereas the zinc alloy exhibited passivation behaviour. Post-degradation analysis revealed localized degradation in both pure zinc and the zinc alloy

Antipsychotic drug waste: A potential corrosion inhibitor for mild steel in the oil and gas industry

In this study, the corrosion inhibition efficiency of thioridazine hydrochloride (TH), an antipsychotic drug, on mild steel (commonly used pipeline material in the oil and gas industry) in 1 M hydrochloric acid (HCl) was evaluated using electrochemical techniques and weight loss method. Electrochemical impedance spectroscopy (EIS) results suggest that TH significantly enhances the polarization resistance (Rp) of mild steel. Similarly, potentiodynamic polarization results showed that the corrosion current density (icorr) of mild steel decreased significantly with addition of TH. To understand the long-term effect of TH, mild steel was tested for 7 days in 100 ppm TH containing electrolyte. EIS results showed that the Rp did not change significantly after 24 h exposure as compared to 2 h exposure; whereas the Rp increased by 28% after 7-day exposure. Weight loss measurements revealed that the inhibition efficiency of TH is remarkably high (98.8%) after 7-day exposure. The adsorption free energy calculation suggests that at the initial stage (1-day) of mild steel exposure, TH was physically adsorbed onto the surface. However, at a later stage (7- day) the binding of TH was chemical, and hence the corrosion protection increased with increase in the exposure period. As compared to the wide range of corrosion inhibitors reported in the literature, TH has shown to be highly effective for mild steel. Thus, it can be suggested that TH drug waste is a potential corrosion inhibitor for mild steel pipelines in the oil and gas industry