Study And Application Of The Improvement On The Definition Of Log Curves

In recent years, the thin layer of logging interpretation has aroused great concern of the logging sector, thus promoting the development to data interpretation from the instrument、to theoretical studies from the field logging、from data acquisition to the profound development of all aspects of software development. Ideal thin layer of logging instrument series is not yet available, according to conventional logging methods and data interpretation thin layer is very meaningful.Due to the limit of vertical resolution of the instrument, the logging response value of the thin layer is affected by the adjacent wall rock influence, so that the thin layer of the parameters to explain the lower accuracy. Thin-layer problem arises when the thickness is less than the vertical resolution of logging tools, the most common of thin intercalation sandstone and mudstone. Logging response is the convolution of the response by the thin layer of log responses and mud wall rocking logging, and is the integrated response of the instrument vertical resolution of the scope of the stratum, so logging curve distortion, can not effectively reflect the thin reservoir logging response. At present, a lot of oil fields have entered in the later stages of development. Inherent in the thin layer of oil and gas resources are more and more attention to people, which become the main growth areas of oilfield production, so we begin to a focused reservoir evaluation and interpretation of potentialthin-layer and thin interbedded.The deconvolution method and frequency matching method are two ways to improve the resolution of thin layer, and two methods are applied in actual production, so that a thin layer is influenced by the surrounding roc、a thin layer of logging signals are utmost close to the true formation signal.First, in accordance with the signal processing point of view, logging signal can be seen as the formation signal and logging system response function convolution filter output. Thus, according to the logging system response function, we can do inverse filtering for logging signal to obtain the true value of the formation. Filtering or inverse filtering is achieved through the convolution operation, so it can be called convolution or deconvolution. Inverse filtering can indeed improve the vertical resolution of well logs, to increase the steepness of the curve, clear stratigraphic interface, so as to achieve the purpose of the recovery of true formation signal, the deconvolution method to improve the vertical resolution curve method.Secondly, the well logs can be as a finite discrete signal of the depth domain, after the fast Fourier transformation, log curve can be expressed as frequency domain signal. Usually, regardless of the logging signals have a low-frequency part of the large range and small range of high-frequency part of the significant features. We can use the match frequency domain method to deal with the low-resolution curve. Analysis shows that, the higher resolution well logs can better reflect the true information on the formation and obviously make the curve improve in horizontal amplitude in many layers. So we can achieve the purpose of improving the vertical resolution of conventional logging in a certain extent.In the last, by means of the matlab programming, we deal with some logs in different blocks. Application results show that thin reservoir is influenced by the surrounding rock, so that the logging response is not obvious, resulting in missed reservoir; log curve is limited by the resolution of conventional logging tools, so logging curves can not effectively identify and remove the thin sandwich to interpret reservoir by mistake, resulting in a great gap between log interpretation of reservoir thickness and true reservoir; Without correction of the natural gamma curve, the resistivity curve and the three porosity curves are seriously affected by the surrounding rock in thin bed, and dividing lithology and judgment of reservoir fluid properties are more difficult. After correction curves are more obvious in the logging response characteristics in the thin layer, thus we can easily divide lithology and judgment of reservoir fluid properties.