Elemental Capture Spectroscopy Log Interpretationmethod And Its Application

With the further development of oil and gas exploration and development, more and more igneous rock and shale oil and gas reservoirs have been found. The reservoir space is complex and the elements are various, the conventional well logging technology is facing a severe challenge. The elemental capture spectroscopy logging technology can identify the mineral composition by calculating the content of the reservoirs’ main elements, and then solve the problem of lithologic identification. Compared with other logging methods, this method has obvious advantages in the calculation of element content and skeleton parameters, the evaluation of mineral composition and the identification of lithology.Based on a large number of domestic and foreign literatures, this paper systematically introduces the physical basis and basic working principle of the elemental capture spectroscopy logging, the model of Am-Be neutron source in the element capture energy spectrum logging tool is established by Monte Carlo method, and the standard spectrum of elements is obtained by the MCNP software simulation. I have researched the interpretation method and data processing flow of elemental capture energy spectrum. First of all, by using the spectrum stripping method and the least square method, the spectrum of the captured gamma ray is unscrambling, and the relative yield of each element is obtained; After that, the weight percentage of each element is obtained according to the oxide synizesis model. Finally, the mineral content of rock is calculated by the model of elemental-mineral transformation. The application of the above methods in igneous rock and organic shale is studied. In igneous rock formation, using elemental capture spectroscopy logging calculated mineral content, combined with TAS chart to realize the identification of igneous rock lithology, calculated the matrix density, matrix neutron and other parameters. In the organic shale formations, using elemental capture spectroscopy logging realized the shale clay, feldspar, quartz, carbonate, pyrite and other mineral groups of calculation, and matrix density, matrix neutron parameters have been calculated, completed the storage layer brittleness index, total organic carbon content and porosity reservoir parameter evaluation. Application examples and analysis show that the elemental capture spectrum logging technology in igneous rocks and shales of the qualitative interpretation and reservoir parameter quantitative calculation application effect is significant, especially for organic shale of fine logging interpretation provides an important research means and methods.