Detecting Carbonate-karst Reservoirs Using the Directional Amplitude Gradient Difference Technique Available to Purchase

Karst-controlled Ordovician carbonate formations are the main oil- and gas-bearing reservoirs in the Tarim Basin, China. Unlike clastic reservoirs and carbonate reservoirs in other areas, the carbonate-karst reservoir in the Tarim Basin has its distinct characteristics that make its detection difficult because no pronounced effect can be recovered using conventional techniques and methods. In this paper, a new method, directional-amplitude-gradient-difference, using the least-squares-fitting (LSF) algorithm, is presented and used to detect carbonate-karst reservoirs. The method estimates the rate of change of the seismic amplitude, also known as the gradient, horizontally and vertically and calculates the difference between these directions. Compared with other gradient-estimation methods, the proposed directional-amplitude-gradient-difference has clear advantages. A field-data example shows that the method can improve accuracy and efficiency in the detection of carbonate-karst reservoirs.