Fractured Shale Reservoir Geophysical Characteristics And Detection Method

With the increasing of the extent of oilfield prospecting, shale fractured oil-gas reservoir is becoming an important field gradually with substitute position. Up to now, there is no systemic, integrated theory and method on fractured oil-gas reservoir' s exploration and prediction. From research status on fractured oil-gas reservoir, this paper has a deep research on shale fracture' s forming -causes and types, characteristics, distributing rules, and control factors of reservoir, seismic reflected characteristics, logging curve' s response by using theory and method of petroleum geology, structural geology, sedimentology and geophysics synthetically. Meanwhile, synthetic prediction and recognition of shale fractured oil-gas reservoir by geological, seismic, and logging are probed, and are applied in shale fractured oil-gas reservoir' s exploration of luojia area to predict the advantaged zone. As a result, we get the cognition and production as follows:(1) Above all, deep research on target zone' s regional structural characteristics, evolutive history of structure, growth characters of layer, evolvement of lake basin and distributing characters of shale fractured oil-gas reservoir have been done. And we find shale fractured oil-gas reservoirs, which locate in mid-lower layer, 2400m"3500m under the surface, are mainly rich in between the third segment' s lower layer and the first segment' s lower layer of sha of the third series. The area are mainly rich in structural fracture, diagenesis fracture, abnormal stress fracture, diagenism shrink fracture, and the majority is steep gradient fracture. As covert oil-gas pool, shale fractured oil-gas pool have special hydrocarbon-bearing system character in the producing of hydrocarbon, the shaping of fractured trap, moment of closing down, holding of hydrocarbon. Therefore, six concept model have been built, including layer, structure, sediment, diagenesis, abnormal stress, and hydro-geotectonic, considering characters of the river entrance' s shale fractured oil-gas reservoir.(2) Systemic research on core from luo-67 well shows us that velocity of p-wave and s~wave in shale will be lower along with the increasing of temperature and will be increase along with the increasing of stress if temperature is constant. Logging curve of shale fracture usually have rules of high resistance and negative SP abnormity, low AC, which can be used to compartmentalize the character of shale fracture semi- quantificationally. Therefore, trains of thought and methods are provided to match different scale data mutually, which is a important and difficult.(3) Internal relationship is analyzed between fracture media and anisotropy. It can be'concluded that the characters of anisotropy, which are induced by different shapes' fracture, are different and the models to be built are thus different too. In fracture media, three kind of waves ( semi-P-wave, semi-Sl-wave, and semi~S2-wave) are coupled together and influence mutually. When they transmit in media, the main influencing factors are elastic parameters and wave' s transmit direction. According to Hudson theory , we can deduce elastic parameters, get the three kind of waves' phrase velocity and polarized direction approximatively based on Christoffel method, analyze their characters of wavefront in EDA media and compare the characters between carbonate fracture and shale fracture.(4)The paper has studyed the characteristics of seismic wave field in the media of EDA, and has made out three aspects of numerical simulation on wave field features by using definite difference: The simulation of P-wave ground .seismic logs in the media of EDA;thediagnostic complication of seismic wave field in cranny belts due to the scattering of cranny wrappage;the decreasing of amplitude and the reversing of polarity of the wave reflected on not only the top but also the bottom of fracture zone. So we can detect fracture through, the variation of some kinetic features such as amplitude. The results indicate that:?When density of cranny increase, th...