Using Gravity Anomaly Study Structure Division And Basement Morphology Of The Hulin Basin

With the rapid development of economic construction, the demands of oil ,gas and other nature resources are on the increase for our country. The potential of exploring large oil and gas fields is relatively decreasing and it is difficult to maintain stable and high yield for the needs of our country. It has great significance to attain oil and gas potential areas via exploration and development of small and medium-sized basins around Daqing Oilfield for our country's economic construction. The paper based on the gravity data of actual measurement plane to study morphology and construction division in Hulin Basin, where belongs to the external basin group in Daqing Exploration Area, and gives the oil and gas prospect area.The distribution characteristic of Gravitational field is a wide range of comprehensive reflection of geological bodies, measured by inversion of gravity data to determine the interface depth, density distribution and the physical properties of ups and downs, that is one of the issues we are very concerned about. In recent years, with performance improvement on the equipment of gravity and magnetic detection, we have gravity and magnetic data accuracy and resolution by increasing, so how to effectively use these measured data, from which we get more geological information, an increase explained accuracy and precision, to obtain the information we need is an important issue. Firstly, this article studied the substrate interface inversion method. The model using polygonal cross-section method, putting the traditional of the polygonal cross-section into a line, depending on the line nodes which are the test point on the ground, in accordance with the polygonal cross-section formula for programming the calculation method may invert the profile of base interface, and divide the plane data into a number of profiles which can invert the basement interface, then the substrate can be planar interface.Physical parameters can be calculated and geological information can be gained in accordance with the gravity anomaly of geological bodies. Derivative conversion,among Gravity data processing,is the first calculation method we contact with which can be used to divide the borders of geological bodies, or analyse the depth or occurrence of geological bodies. The predecessors raised the concept of the horizontal derivative and vertical derivative which can be used in potential field. They demonstrated these methods'effectiveness to detect the border of the geological bodies through model experiment and practical application for many times. This paper based on Derivative conversion. With the foundation of tilt angle, the total horizontal derivative of the tilt angle, non-value total horizontal derivative of the tilt angle and Theta map used to determine the border of geological bodies, first of all, I verify the effectiveness of these methods through model test and bring forward their shortcomings in recognition of the border. At last,I put forward a number of methods for detecting the border of geological bodies.1. It was found that use of the real part of the hyperbolic tangent function in the tilt angle calculation achieved better delineation of the edges of the body than the filter predecessors raised(we referred it as HTA in this paper). We can find the border of the geological bodies when the number of the HTA value is 0 or close to 0.The border of the geological bodies identified in HTA map surrounded by a circle of negative value which would complicate the interpretation of geological. Overlaying only the value of the HTA above some user-defined threshold on the original data proved useful in solving this problem. The value of HTA which is greater than threshold will be covered so that you can get a clear boundary of geological bodies.2. After the definiens of tilt angle is given while previous people studied the detection methods of the border of geological bodies, We can associate it with the detinition of second-order tilt angle. The second-order tilt angle means the tilt angle of the tilt angle. It is proved that the second-order tilt angel is effective in detecting the border of the geological bodies through model experiment. The second-order tilt angle was sensitive to noise, and improved results were achieved when the first-order tilt angle data was smoothed(using a simple Gaussian convolution kernel)prior to compulation of the second-order tilt angle. In theory the calculation of the second-order tilt angle is not physically valid, however, the result of detecting the border of the geological bodies is reliable. The second-order tilt angle is good at attaining the detailed of the geological information, so it can magnify the noise. We can make the first tilt angle smoothed which is mentioned above in order to figure out this problem. We can use diaphaneity deal with the second-order tilt angle map, so as to enhance the display of useful information.3. Standard tilt angle is defined as a ratio's arctan. The ratio's numerator is vertical derivative of potential field while its denominator is horizontal derivative. Similar to this definition, we can define the direction tilt angle. In accordance with the differences between the ratio's numerator and ratio's denominator, we definition two forms of direction tilt angle. These forms are based on the result of arctan. We called them Tdrx and Tdry. Tdrx and Tdry produce Tilt datasets with features enhanced in the x and y directions, respectively. Their forms of definition is similar to the standard tilt angle. Directional tilt angle can identify the border of the geological bodies partially. For grid data, two directional tilt angle which are orthogonal in two horizontal directions can detect the edge of the body in two direction orthogonal. In the view of the effectiveness of the second-order tilt angle, we can calculate the second-order tilt angle based on directional tilt angle which can be used to detect the edge of the body.4. We can calculate the absolute value of the vertical derivative of potential field which is as denominator, and the total horizontal derivative is as horizontal. We should calculate this ratio's arctan which can be called TDX map(we also call it switch tilt angle). This approach has been proved very effectively in detecting the edge of model.These new technologies is proved very effectively through model experiment. The gravity data of Hulin Basin after smoothed is used in these new technologies. We detect 30 fault zone using these new technologies. Hulin Basin is divided into three zones and five depression combined with gravity anomaly subarea. At last, I gived the oil and gas prospect area field combined with electrical information.The boundary detection techniques has a good effect through the results of the model experiment and actual data processing. It need a further study in order to know the results of these techniques using in detecting the non-vertical model of geological bodies.