Processing Of Gravity And Magnetic Data In The ShiWu Graben Basin And Basement Structure Analysis

An area of about 2800 km2, The ShiWu graben basin is in the southeast of the SongLiao Basin, and is one of the most important regions for petroleum geology research and petroleum prospecting. For the past few years, a series of breakthroughs has been made in oil and gas exploration in deep zone of SongLiao Basin, and that indicates hydrocarbon potential in the basement. However, researches about the late Paleozoic basement are still very poor in this area. In this paper, the gravity and magnetic anomaly characteristics of basement of the ShiWu graben basin are extracted with the support of data processing and interpretation. Besides, the fault character and the structure of the late Paleozoic basement are discussed and predicted on the basis of geological data, petrophysical parameters, seismic data and log information collected in working area and its adjacent area.In this paper, the gravity and magnetic anomaly response of fault are analyzed, besides that the faults of basement are interpreted and the characteristics of fault system can be analyzed. General rules of petrophysical parameters are obtained based on rock density and magneticsusceptibility characteristics in working area and its adjacent area. Five structural units (sand-mudstone zone, sand-mudstone and vulcanite zone, carbonate zone, schist or gneiss zone, magmatic rock zone) of basement can be subdivided in ShiWu basin on the basis of geologic outcrop observation and log information. Residual and regional field, as well as superficial and deep field can be obtained from the gravity and magnetic abnormal separation. Make use of gravity-seismic exfoliation model, the sedimentary rock anomaly is peeled off, and the basement lithologic gravity anomaly may be obtained. The basement lithologic magnetic anomaly can be obtained by using vertical second derivative combined with the method of depth anomaly separation. On this base, basement structural unit is predicted and divided. At the end, the basement structural evolutional setting of the ShiWu graben basin is discussed further on.