Gravity And Magnetic Anomaly Of Reservoirs Identificating And Evaluating Technology Research

Relying on the subject of National Science&Technology Important&Specific Projects ("Extraction and Overall Evaluation Technology on Geophysical and Geochemical Oil-Gas Exploration Information",2008ZX05020-008), the paper researched the methods for identifying and evaluating gravity and magnetic anomalies information of reservoir. Based on the features of reservoir’s gravity and magnetic information, it puts forward a set of methods on eliminating the gravity and magnetic anomalies information excluded reservoir—identifying the gravity and magnetic weak information of reservoir—comprehensive evaluation of reservoir. It will provide supporting afore-information on the location of reservoir for huge oil-gas fields’ seismic surveys. The paper mainly got the following achievements.It studied the pattern of gravity and magnetic anomalies of typical reservoir. This paper analyzed the correspondence of gravity and magnetic anomalies and the geology structure of reservoir based on lots of forward simulation on different types of reservoirs. It summarized the correlation of gravity and magnetic anomalies and oil-gas with the methods of statistic analysis, the normalized level derivative, the normalized vertical derivative, power spectral analysis, the ratio of gravity&magnetic anomalies and the structure characteristic of reservoirs. Statistic analysis methods told us the relationship between gravity&magnetic anomalies of reservoir and the features on reservoir’s amplitude and tendency based on the mean value, variance, migration coefficient and kurtosis coefficient of gravity&magnetic anomalies of reservoirs. The normalized level derivative and the normalized vertical derivative can indicate the border of gravity and magnetic anomalies caused by reservoirs. Compensation factor can overcome the problem of spectrum leakage when do Fourier transform on the finite length of data. Took cut-off frequency of power spectrum of different scope of slope as the important parameter for distinguish the deep anomalies and shallow anomalies of reservoir’s geological structure. It also studied the relationship between the ratio of gravity and magnetic anomalies caused by reservoir and the anomalies caused by geology structure and the tectonic height and depth, reservoir properties and the oil-gas distribution range, discussed the possibility of distinguishing the weak gravity&magnetic anomalies caused by reservoirs which located on different geology structure.It proposed the methods for distinguishing and eliminating the gravity&magnetic anomalies not caused by reservoir. Towards the random interference caused by shallow geology (does not contain oil or gas), this paper proposed one method to conserve useful information and eliminate useless information based on wavelet analysis combined spatial correlation with threshold, the key point of related coefficient of neighboring two scales can be used for decomposing scales for wavelet analysis. Proposed basis function’s self-adaption constructing method for gravity&magnetic anomalies based on power spectral analysis; constructed the relating scale-basis function according to the different characters of power spectral of gravity&magnetic anomalies caused by reservoir and anomalies not caused by reservoir.Based on support vector machine (SVM) technology, the paper had studied a technique to identificate and evaluate gravity and magnetic anomalies of oil-gas. Conventional treatment methods mainly in the following two questions: in the both of "exist oil-gas" and "not exist oil-gas" cases, gravity and magnetic anomalies is very similar so be difficult to identify; even if the oil-gas gravity and magnetic anomalies is easy to identify, the parameters in the process remain the lack of quantitative description of the problem. Therefore, in the prediction of gravity and magnetic anomalies of reservoirs background structure, based on Support Vector Machine(SVM) that contains the new scale kernel function related to gravity and magnetic anomalies, the paper puts forward a adaptive processing method to identify oil-gas of different types reservoir. Compared with the conventional, it can add more geological constraints and to avoid the problem of parameter selection, at the same time, the weak gravity and magnetic anomalies of oil-gas to get better recognition.Finally, the actual data processing to verify the practicality and effectiveness of the new method, and gives the interpretation of the results of oil-gas reservoirs comprehensive evaluation of the study area.