Vertical Orientation With The Fractured Reservoir Detection Technique

The fractured reservoir is one of the difficulties and hot spots for geologists in nowadays. According to the experience in exploration and development oil and gas fields around the world for many years found that the fractured reservoir has following three characteristics:(1)Fractured reservoir are very common in the oil and gas fields. After years of exploration experience of our predecessors, we can see that the cracks can be found in the Sandstone,Mudstone,Carbonatite,Magmatic rocks and Metamorphic rock reservoir.(2)The distribution of the fractured reservoir is very complexity and has poor law.It can be known from the formation mechanism and classification of the fractured reservoir,it has non-single formation and no fixed type.And the occurrence status of the fractured reservoir can be changed by the morphological changes in geological.(3) The fractured reservoir has a dual nature. The high permeability of the cracks are played an important role in the development of oil and gas production. It not only can improve the hole reservoir permeability and porosity, but also can take shape the second trap.So that it is possible to change the non-porosity and permeability of the mudstone, magmatic rocks and metamorphic rocks into the oil and gas reservoir.However, the cracks in the reservoir can be damage to the oil and gas reservoirs.Because of the poor connectivity obstruction or filling in the fractured reservoir, It is likely a false impression that it is oil-free.From the above three characteristics of the fractured reservoir, we can see that precise delineation of fractured layer has a very important practical significance.This article is beginning with the basis concept of the fractured reservoir.it brief introduce the formation mechanism of the fractured reservoir,the classification of cracks,the geological model and research at home and abroad. Then it analyses the anisotropic of the fractured medium and gives the relationship between stress and strain. Derived from Information,I gives two fractured media model: Hudson theoretical model and Thomsen theoretical model.I gives the derivation of the phase velocity of Thomsen theoretical models,by analogying the derivation of the VTI media model which derivate by Thomsen,Daley and Hron.Then i use the result at the given model.From the above working,I get the phase velocity curves of different parameters in the dry,non-viscous fluid containing substances and weak material cracks.By analyzing the result,I summarize up the law of seismic wave phase velocity changed with the parameters in fractured reservoir.During the next paragraph,I study the P-wave AVO forward modeling, From the simulation results we can be seen that: Isotropic media and anisotropic media (EDA medium) P-wave emission coefficient changes with the laws of diametrically are opposed;the P-wave reflection coefficient of EDA media is influence by the nature which is filling the cracks;the reflection coefficient of EDA media is influence by isotropic stratum, the existence of isotropic formation may be buried on the identification of fractured reservoir.Finally, I analyse the single-layer EDA media's traveltime equation and the P-wave's time equation in the orthogonal seismic line equation. The results show that: For the same EDA media model, When the cracks are dry cracks and non-viscous fluid,it has the same numerical that the offset is changed by the azimuth and the p-wave orthogonal difference.Because when the cracks are dry cracks and non-viscous fluid,the p-wave has the same nature.The traveltime of the single-layer EDA media is impact byδ? 2ε≈δ(v),δ(v) is the effective Thomsen coefficient.Whenδ( v)<0, the travel time changes with offset of Azimuth ? = 90°is greater than Azimuth ? = 0°'s;Whenδ( v)>0时, the travel time changes with offset of Azimuth ? = 90°is smaller than Azimuth ? = 0°'s.The p-wave 's time equation is lined by fracture azimuth 35°and 135°.when the fracture azimuth between 0~35°and 135~180°,it is positive and increasing with the offset; when the fracture azimuth between 35~135°,it is positive and reducing with the offset.Through research, this article has made the following innovations:1. I give the derivation of the phase velocity of Thomsen theoretical models,by analogying the derivation of the VTI media model which derivate by Thomsen,Daley and Hron.Then i use the result at the given model.It is verified the three-wave phase velocity expression of Thomsen model in EDA media which is appeared in a lot of literature.Then I analysis the p-wave,S //-wave and S⊥-wave at the different Thomsen parameters and filling the cracks in the Polar coordinates. Through the analysis of graphics,I gave the law of the three group in different filling cracks.It can be seen from phase velocity expression of Thomsen theoretical model:the P-wave and the S //-wave are mainly affected by theε,δof the Thomsen parameter;the S⊥-wave is mainly affected by theε,γof the Thomsen parameter.2.I applicate Shuey's isotropic P-wave reflection coefficient and Andreas Ruger's azimuthal anisotropy P-wave reflection coefficient under different filling cracks,I Simulate the graphics of the P-wave reflection coefficient and the amplitude in different model parameters and fracture azimuth.It can be seen from that the isotropic layer affecte the identification of fractured reservoir; At the same time, the filling cracks in different materials restricte the P-wave reflection coefficient changes.3.I give the process of the single-layer traveltime reflection formula's parameters in EDA media which are definited by Sayers and Ebrom (1997).And I apply it to analysis the traveltime under different filling cracks . As can be seen from the analysis of the results:When changed the filling in the cracks,the single-path of the EDA madia has the same trend, The difference is that in different azimuth and offset go under the different specific.4.I use Li Xiangyang's fracture detection using azimuthal variation of P-wave moveout from orthogonal seismic survey lines theory analysising the Orthogonal traveltime difference in the Dry,non-viscous fluid and weak substances cracks of EDA media. As can be seen from the analysis of the results: when the crack's azimuth in the 35 ~ 135°,the moveout is negative. This is different from the isotropic formation.So,This using law can be identified the fractured reservoir.