Direct interpretation of 2D potential fields for deep structures by means of the quasi‐singular points method

Abstract

A B S T R A C TThe founder of the Russian school of direct interpretation of potential fields (with minimal prior geological-geophysical information) was V.M. Berezkin, who introduced the operator of total normalized gradient for the 2D interpretation of profile gravity data sets. This operator was successfully applied in searches of hydrocarbon reservoirs. The further development of this approach (the so-called quasi-singular points method) has allowed solution also to various structural problems, using mathematical criteria for the transition from extremes of total normalized gradient fields to coordinates of anomalous sources. The main numerical evaluation strategy is based on stabilized downward continuation of field derivatives and specific use of the filtration properties of Fourier series approximation. The characteristic properties of the quasi-singular points method are: 1) presentation of a more general total normalized gradient function through additional parameters (derivative order m, form of smoothing function Q, number of Fourier coefficients N * with maximal N), optimum values being chosen during a peak-spectrum analysis of the interpreted function; 2) calculation of the set of total normalized gradient fields for various values of N * /N, representing coordinate systems {x,N * /N} as an 'axes tree' of extrema, where each 2D total normalized gradient field is representationally compressed in a 1D line, permitting a) immediate overview of the positions of the axes in all variants of the calculated fields and b) reduction of the retained information, as required in subsequent interpretation; 3) development of two criteria for transition from extrema of total normalized gradient fields to the coordinates of anomaly sources. The quasisingular points method is intended for tracing limiting gently-sloping boundaries, if their micro-relief features are sources of the interpreted anomaly but sub-vertical contacts may also be traced. The method has been tested in delineating various geological structures. One of the most challenging, successfully achieved, was tracing of the Moho discontinuity and study of the upper mantle, using only Bouguer anomaly data along interpretation profiles. This is attested in an example of two regional profiles intersecting the European part of Russia. The central part of one of them coincides with the results from a deep seismic profile.

Improved normalized full-gradient method and its application to the location of source body

“…However, this method is somewhat subjective, and may entail some ambiguity in the final depth estimates, or even give incorrect results. An alternative is to analyze the field spectrum (Elysseieva and Pasteka, 2009), which is a far more complicated procedure than other implementations of the NFG method. A simple and reliable method to estimate the optimal number of harmonics is therefore required.…”

“…introduced by Berezkin (Berezkin, 1973;Elysseieva and Pasteka, 2009) and applied to locate oil reservoirs from gravity data. It was then extended to three-dimensional applications by Zeng et al (2002) and used to interpret the gravity data obtained from the Shengli oil field in China.…”

Review Paper: Historical development of the total normalized gradient method in profile gravity field interpretation

“…One of the most important topics developed in the Russian school of potential‐field interpretation was the concept of singular points. This concept was introduced in the early 1960s (Golizdra , , ; Strakhov ,b,c, , ) and developed later by various authors (Berezkin ; Voskoboynikov and Nachapkin ; Berezkin ; Zhdanov and Vitvitskiy ; Troshkov ; Elysseieva , ; Elysseieva et al . and any others).…”

“…; Elysseieva ; Berezkin et al . ; Berezkin and Skotarenko ; Skotarenko and Besprozvanniy ; Berezkin ; Lobzova and Elysseieva ; Elysseieva ; Elysseieva et al . ; Elysseieva ).…”

Depth from extreme points method for gravity gradient tensor data

“…Specifically, because of the ongoing development of the gradient tensor technique, study on interpretation methods of gradient tensor data becomes a prevalent and challenging problem. The normalised full gradient method (Elysseieva and Pasteka 2009;Fedi and Florio 2011) uses the adaptive iterative Tikhonov regularisation downward continuation to interpret full tensor gradient data (Zhou 2015). * Email: wennazhou@163.com Many simple and fast methods have been used to interpret gravity gradient tensor data, such as Euler deconvolution, analytic signal method, and tilt-depth.…”