Median Polish Kriging and Sequential Gaussian Simulation for the Spatial Analysis of Source Rock Data

In this technical note, a geostatistical model was applied to explore the spatial distribution of source rock data in terms of total organic carbon weight concentration. The median polish kriging method was used to approximate the “row and column effect” in the generated array data, in order for the ordinary kriging methodology to be applied by means of the residuals. Moreover, the sequential Gaussian simulation was employed to quantify the uncertainty of the estimates. The modified Box–Cox technique was applied to normalize the residuals and a cross-validation analysis was performed to evaluate the efficiency of the method. A map of the spatial distribution of total organic carbon weight concentration was constructed along with the 5% and 95% confidence intervals. This work encourages the use of the median polish kriging method for similar applications.

Top-of-Line Spatial Corrosion Prediction in Gas Pipelines

The top-of-line corrosion (TLC) is corrosion observed at the upper section of a pipeline, as measured from the circumference of the pipe. The magnitude of TLC is mostly determined using the mechanistic condensation models. The spatial prediction of TLC, however, has not been of the interest among researchers, so as to know at what o’clock orientations (with respect to pipeline cross section) corrosion may accumulate the most. TLC spatial prediction is directly related to the release of corrosion inhibitor (CI) in the pipeline. The probability of retaining CI at the upper part of the pipeline is always a challenge due to the inconsistency of the operational flow parameters coupled by acceleration due to gravity. Thus, there is the need to properly understand the development of TLC with regard to its space. This paper proposes the analysis on TLC spatial prediction to be carried out by means of statistical approaches called the Exploratory Data Analysis (EDA) due to the nature of corrosion that are random. EDA is a simple tool that is able to summarize the main characteristics of TLC data using visual methods. The TLC data was taken from a gas pipeline operating in Malaysian offshore region. A median polish model (of EDA) for the TLC was later generated. A prediction table was also developed to guide users on the estimate of TLC in gas pipelines with regards to the o’clock orientations of the pipe circumference.